<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <HTML> <HEAD> <META NAME="keywords" CONTENT="FAQ, robot, combat, questions, Battlebots, Robot Wars, Robotica, Run Amok"> <META NAME="description" CONTENT="Ask Team Run Amok's Aaron Joerger your questions about combat robots and robot events."> <META NAME="viewport" content="width=device-width, intitial-scale=1"> <META http-equiv="Content-Type" content="text/html;charset=ISO-8859-1"> <TITLE>Ask Aaron: questions and answers about combat robots</TITLE> <link rel="stylesheet" type="text/css" href="aaron.css"> <link rel="apple-touch-icon" sizes="180x180" href="/AskAaron/apple-touch-icon.png"> <link rel="icon" type="image/png" sizes="32x32" href="/AskAaron/favicon-32x32.png"> <link rel="icon" type="image/png" sizes="16x16" href="/AskAaron/favicon-16x16.png"> <link rel="manifest" href="/AskAaron/manifest.json"> <link rel="mask-icon" href="/AskAaron/safari-pinned-tab.svg" color="#5bbad5"> <link rel="shortcut icon" href="/AskAaron/favicon.ico"> <meta name="msapplication-config" content="/AskAaron/browserconfig.xml"> <meta name="theme-color" content="#ffffff"> <script type="text/javascript"> if (top.location != self.location) top.location = self.location; </script> </HEAD> <BODY class=menu> <div class=pos_fixed> <a href="AskAaron/FAQ.html"><img src="pic2/Qmark.gif" vspace=5 border=0 title="FAQ" onmouseover="this.src='pic2/Qmark2.gif';" onmouseout="this.src='pic2/Qmark.gif';"/></a> <br> <a href="AskAaron/tools.html"><img src="pic2/tool.gif" vspace=5 border=0 title="Combat Robot Design Tools" onmouseover="this.src='pic2/tool2.gif';" onmouseout="this.src='pic2/tool.gif';"/></a> <br> <a href="javascript: void(0)" onclick="window.open('squid/newtorquecalc.htm','TorqueWin', 'toolbar=no,top=89,left=65,width=740,height=550,menubar=no,resizable=yes'); return false;"> <img src="pic2/gear_link.gif" vspace=5 border=0 title="Tentacle Drivetrain Calculator" onmouseover="this.src='pic2/gear_link2.gif';" onmouseout="this.src='pic2/gear_link.gif';"/></a> <br> <a href="AskAaron/optimum.html"><img src="pic2/optimum.gif" vspace=5 border=0 title="Optimum Robot Drivetrain Gearing" onmouseover="this.src='pic2/optimum2.gif';" onmouseout="this.src='pic2/optimum.gif';"/></a> <br> <a href="AskAaron/tools.html#spinner"><img src="pic2/weapon_link.gif" vspace=5 border=0 title="Excel Spinner Weapon Spreadsheet" onmouseover="this.src='pic2/weapon_link2.gif';" onmouseout="this.src='pic2/weapon_link.gif';"/></a> <br> <a href="AskAaron/spinner_FAQ.html"><img src="pic2/spiral_button.gif" vspace=5 border=0 title="Ask Aaron Spinner Weapon FAQ" onmouseover="this.src='pic2/spiral_button2.gif';" onmouseout="this.src='pic2/spiral_button.gif';"/></a> <br> <a href="AskAaron/hamburger.html"><img src="pic2/hamburger.gif" vspace=5 border=0 title="The Hamburger is Bad" onmouseover="this.src='pic2/hamburger2.gif';" onmouseout="this.src='pic2/hamburger.gif';"/></a> <br> <a href="AskAaron/solenoid.html"><img src="pic2/solen_link.gif" vspace=5 border=0 title="Solenoid and Relay Guide" onmouseover="this.src='pic2/solen_link2.gif';" onmouseout="this.src='pic2/solen_link.gif';"/></a> <br> <a href="AskAaron/radio_guides.html"><img src="pic2/radioicon.gif" vspace=5 border=0 title="Radio Guides" onmouseover="this.src='pic2/radioicon2.gif';" onmouseout="this.src='pic2/radioicon.gif';"/></a> <br> <a href="AskAaron/LiPo_FAQ.html"><img src="pic2/bolt_button.gif" vspace=5 border=0 title="Lithium Polymer Battery FAQ" onmouseover="this.src='pic2/bolt_button2.gif';" onmouseout="this.src='pic2/bolt_button.gif';"/></a> <br> <a href="AskAaron/greatest.html"><img src="pic2/greatest.gif" vspace=5 border=0 title="Aaron's Greatest Hits" onmouseover="this.src='pic2/greatest2.gif';" onmouseout="this.src='pic2/greatest.gif';"/></a> </div> <A name="TOP"></A> <FONT FACE="Lucidia Sans, Arial"> <table width=100% border="0" cellpadding="0"> <tr> <td width="60" valign="top" align="left"> <img src="pic2/60.gif" alt="spacer"><p> </td><td> <table width=100% cellpadding=0> <tr> <td width=90% style="text-shadow: 1px 2px 1px #CCC; vertical-align: top"> <A href="AskAaron.html"><img src="pic2/aaron_banner_ani.gif" width=249 height=59 align=left border=0 style="margin: 5px 15px 5px 10px;"></a> <Font size=+1 face="Verdana, Lucidia Sans, Arial"><B><br> <rem ===><nobr> 6471 Questions and Answers</nobr> <nobr>about Combat Robotics</nobr> <br><nobr>from Team Run Amok</nobr> <rem ===> </b></font> <HR class="red"> </td> </td><td rowspan=2 valign=top align=right> <a href="AskAaron/anniversary.html"> <img src="pic2/Ten_2.gif" border=2 style="margin: -5px 5px 0 25px;" title="Fifteen Years of Ask Aaron [Click Me]"> </a> </td> </tr> <tr> <td valign=top> <FONT FACE="Lucidia Sans, Arial"><b> <a href="robotica.html">Team Run Amok</a> receives a lot of email asking about the design and operation of combat robots. In 2003 my son and team member Aaron Joerger (then 12 years old) asked for a question and answer page to document our responses.</b> </td></tr></table> <REM =================================> <P><center> <table width=99% border=1 bordercolor="#D0C0A7" cellspacing=4 bgcolor="#C1B497"> <tr><td><font face="Lucidia Sans, Arial"> <table class="main" cellpadding=4><tr><td> <img src="pic2/aaron_ani2.gif" style="width: 148px; float: left; margin: 10px 15px 10px 10px;"> <table bgcolor="white" border bordercolor="#E2DAC2" style="margin: 10px;"><tr><td> <table cellpadding="2"> <tr><td valign="top"> <a href="#question"><img src="pic2/question.gif" border="0" style="margin: 5px 10px 10px 5px; width: 157px; float: left;" alt="Got a question?"></a> <rem /td><rem td> <font color="#444444"><b> We&nbsp;welcome&nbsp;combat&nbsp;robot questions. Check the Ask Aaron Archives first to see if your question has already been answered, then click the&nbsp;blue&nbsp;button. </b></font> </td></tr></table> </td></tr></table> <p> <table bgcolor="white" border bordercolor="#E2DAC2" style="margin: 10px;"><tr><td> <table cellpadding="2"> <tr><td valign="top"> <a href="AskAaron/FAQ.html"><img src="pic2/arch.gif" border="0" style="margin: 5px 10px 10px 5px; width: 157px; float: left;" alt="The Ask Aaron Archives"></a> <rem /td><rem td> <font color="#444444"><b> Click&nbsp;to&nbsp;browse&nbsp;<i>thousands</i> of previously answered questions by category, or search for specific&nbsp;topics. Includes <a href="AskAaron/FAQ.html"><img src="pic2/faq.gif" border="0" align="absmiddle" width="169" height="19" alt="FAQ"></a><br> </b></font> </td></tr></table> </td></tr></table> <p> <table bgcolor="white" border bordercolor="#E2DAC2" style="margin: 10px;"><tr><td> <table cellpadding="2"> <tr><td bgcolor="#000000" valign="middle"> <img src="pic2/caution.gif" width="160" height="41" alt="Caution"> </td><td>&nbsp; </td><td> <font color="#444444"><b>Even small combat robots can be dangerous! Learn proper construction and safety techniques before attempting to build and operate a combat robot. Do not operate combat robots without proper safeguards. </b></font> </td></tr></table> </td></tr></table> </td></tr></table> </td></tr></table> </center> <REM =================================> <FONT FACE="Lucidia Sans, Arial"><B>&nbsp; <A name="RECENT"></A> <hr class="box" style="margin: 0;"> <center> <table width=98% style="background-image: url(pic2/paulcos60.gif); height: 60px;" title="Robots from paulcosdrawings.blogspot.com"><tr><td></td></tr></table> </center> <hr class="box" style="margin: 0px 0px 30px 0px;"> <REM =================================> <rem css center - "max-width: 70%; display: block; margin: 0 auto; border-color: #BBB;"> <REM =================================> <font color="#C22222"> <img src="pic2/hard_bar.jpg" border=2 style="float: right; max-width: 40%; margin: -10px 10px 5px 20px;" title="Tombstone - standard weapon bar"> <img src="pic2/soft_bar.jpg" border=2 style="float: right; clear: both; width: max-width: 40%; margin: 0 10px 5px 20px;" title="Tombstone - soft target weapon bar"> Q: Hi Mark, Had a conceptual question about impactors on horizontal spinners. Traditionally, the inserts come to a triangle point with the <a href="https://en.wikipedia.org/wiki/Hypotenuse">hypotenuse</a> facing bot. Is there any sense in making a vertical ramp impactor to get under opponents instead of a straight line to hit anywhere in the height of the weapon? <p> Many Thanks. [Pittsburgh,&nbsp;Pennsylvania] </font><p> A: <font color="#116644">[Mark J.] I'm confused by your question. I'm not sure why you'd want to use a horizontal spinner to try to 'get under' your opponent when the weapon is designed to tear them apart. If you want to get under them, build a wedge. <p> The impactors and inserts I typically see on horizontal spinner weapons are typically flat, hardened, vertical surfaces designed to transfer destructive impact energy against an opponent's hard surfaces. Some spinners have special blades with sharp leading edges to swap-in against softer-armored opponents, but hitting a hardened surface with a sharp blade blunts it immediately. See the comparison of 'Tombstone' bar weapons at right. <p> For a reader quetion (now in our <a href="AskAaron/ants.html">Ants, Beetles, and Fairies archive</a>) I asked builder Jamison Go why he sometimes replaces the single-tooth disk (STD) in his beetleweight horizontal spinner 'Silent Spring' with a saw-edged impactor. His answer: <p> <table class="box" style="float: right; clear: both; margin: 5px 10px 20px 10px;"><tr><td><i><img src="pic2/silent.jpg" border=2 width=300 style="float: right; margin: 5px 5px 5px 20px; max-width: 50%; "title="Beetleweight combat robot 'Silent Spring'"> Everyone is hype about single tooth blades for "bite" but why? What does bite actually do for you? It is heavier engagement on a piece of material which is arguably more energy dissipated just because it has nowhere to go. <p> What if the opponent has no such grabbable surfaces? Say for example, a robot made of rubber or foam? The traditional STD would be ineffective unless sharpened every match and even then its likely only good to the first few hits because it is THE singular wear point. <p> The saw-blade is for whittling opponents who have only compliant armor or soft things at the hitting surface. Instead of going for one big impact which would normally be absorbed, I flake material away at a high rate. What happens is I end up grabbing the same amount, but only after several milliseconds of tearing deep into them. <p> [My opponent was going to] use his over undercutter attachment which meant the only hitable surfaces were his wheels, hence the decision for that type of blade. </i></td></tr></table> <p> </font><hr class="box"> <font color="#C22222"> Q: Hi Mark! I was wondering if there were any robots with instead of a single drum, Had two or three disks next to each other to make more power from all three motors? Thanks! (Also go RunAmok) [Lynn,&nbsp;Massachusetts] </font><p> A: <font color="#116644">[Mark J.] Thanks for the 'Run Amok' shout-out, Massachusetts. <p> <img src="pic2/rotator.jpg" border=2 style="float: right; width: 240px; max-width: 40%; margin: 0 10px 5px 20px;" title="BattleBots competitor 'Rotator'"> There have been several multi-spinner combat robots, but the spinners are usually located on opposite ends of the 'bot. A current example of that design is BattleBot 'Rotator', armed with large independent horizontal disks on front and back. The flaw in this design is that only one of the two disks can impact your opponent at a time, limiting the damage the system can inflict. <p> <img src="pic2/double_dutch.jpg" border=2 style="float: right; clear: both; width: 240px; max-width: 40%; margin: 0 10px 5px 20px;" title="BattleBots competitor 'Double Dutch'"> An alternative twin-spinner system design is employed by 2018 BattleBots competitor 'Double Dutch'. Their design features counter-rotating bar spinners placed above and below the robot body. The two bars are powered by a single electric motor. Although both weapon bars can attack an opponent at the same time, it's likely that one bar with strike before the other and throw the opponent clear before the second bar can impact. Almost certainly the two potential weapon impacts will strike different locations on the opponent, which will also limit their effectiveness. <p> <img src="pic2/not_so_free.jpg" border=0 style="float: right; clear: both; width: 240px; max-width: 40%; margin: 0 10px 5px 20px;" title="Antweight combat robot 'Not So Free Hugs'"> A different double-spinner approach is seen in antweight 'Not So Free Hugs' which has twin saw blades on articulated arms. The idea here is not impact damage but the ability to trap and saw into soft wheels or plastic side armor. Here the ability to access different locations on the opponent is a benefit as it gives a greater chance to find something vulnerable to saw damage. <p> You'll note that all of these designs are horizontal spinners, and that none of them are terribly successful. The potential benefits of multiple vertical drums or disks are even more difficult to imagine. Why bother with three small independent disks and three small motors when you can have one larger drum and a large motor three times as powerful? A hit anywhere on the drum would transfer full impact energy to the opponent, whereas a less-than-perfectly-aligned hit from a triple disk might only transfer impact energy from one of the disks. Sorry, but I'm seeing added weapon complexity and weight with no real advantage. Simple robots win. <rem> <div class="box" style="text-align: left;"> Drivetrain, radio set-up, general construction practice, and weapon/chassis balance are all <u>much more important</u> than the type of weapon you choose. There are plenty of examples of winning robots with ineffective weapons, and there are many more examples of losing robots with awesome weaponry. If you get the basics right you're going to have an above average robot no matter what weapon it carries. <a href="javascript: void(0)" onclick="window.open('cheerleader.html','CheerWin', 'toolbar=no,top=110,left=70,width=700,height=370,menubar=no,resizable=yes'); return false;"> <input type="button" value="Cheerleader" name="cheerleader" style="background-color: #A02; color: #FFF; font-weight: bold; margin: 0px 0 0 5px;"></a> </div></font><hr class="box"> <font color="#C22222"> Q: Is there a reason those who use brushless only have used the ones made for airplanes? Why not cars? Something like this: <a href="https://hobbyking.com/en_us/turnigy-1-8th-scale-4-pole-brushless-motor-2100kv.html">Turnigy 1/8th Scale 4-pole 2100KV</a>.[Hagerstown, Maryland] </font><p> A: <font color="#116644">[Mark J.] There are two broad types of brushless motor design: <ul class="blue"> <li><span class="x">Outrunners</span> have a stationary core (stator) and a magnet-lined 'can' (rotor) that spins around the outside. <li><span class="x">Inrunners</span> have a stationary outer 'can' like a brushed motor with a spinning magnet rotor inside. </ul> The outrunner-style motors are commonly used in smaller combat robots because they spin more slowly and with greater torque than inrunners. This makes it simpler to get the correct reduction for weapon use, and keeps input RPM low enough for inexpensive drive gearboxes. <p> As robots get larger you see more inrunner designs in use. Larger inrunner motors spin more slowly than the tiny ones which makes them a workable option for both drive and weapon power. The Turnigy motor you referenced has about the right amount of power for a hobbyweight weapon but spins at better than 38K RPM, which could be difficult for a belt drive to handle -- simpler to use an outrunner. For drive use, a pair of the Turnigy inrunners would have enough power for a featherweight 'bot, and this is probably the lightest class where I would consider using inrunner drive motors. <p> By the time you get up to heavyweight 'bots, the outrunner motor styles have disappeared and everyone uses inrunners if they're using brushless. </font><hr class="box"> <font color="#C22222"> Q: Can I use my Quantum pistol-grip radio for an antweight robot? </font><p> A: <font color="#116644">[Mark J.] Yes, with a little added hardware. Your <a href="https://hobbyking.com/en_us/quanum-2-4ghz-3ch-pistol-grip-tx-rx-system.html">Quantum radio</a>, like most pistol-grip R/C systems does not have the 'mixing' capability to to control a robot. Your steering 'wheel' (radio channel 1) controls your steering servo servo to point your front wheels, and your throttle 'trigger' (radio channel 2) controls the motor speed controller for forward/reverse motion. To control a 'tank-steer' robot the control channels must be 'mixed' to each control the motor(s) on each side of the robot, but in different ways: <ul> <li>The 'trigger' must instruct both motor controllers to respond together to move the robot forward/reverse; and <li>The 'wheel' must instruct the motor controllers to respond in opposite directions to turn the robot. </ul> Fortunately, you can add a small an inexpensive bit of electronics called a 'channel mixer' to your robot to sort this all out. These are available from multiple sources. Many builders use the <a href="https://www.fingertechrobotics.com/proddetail.php?prod=ft-tinyMixer">FingerTech tinyMixer</a> for its robot-friendly design and functions. </font><hr class="box"> <font color="#C22222"> Q: what flavor of Machine screws are best for a battle bot? (GR 8/alloy steel, Titanium, stainless) specifically what is needed for holding armor on?<br> Is harder always better? [Hagerstown, Maryland] </font><p> A: <font color="#116644">[Mark J.] <img src="pic2/shear_bolt.jpg" border=2 style="float: right; max-width: 40%; margin: 0 10px 5px 20px;" title="Shear forces on a bolt are bad!"> Machine screws / bolts are designed and rated to resist a 'pull' force that is tested by a machine that applies a gradually increasing force. That type of strength is important in many applications, but it is not the type of load fasteners will face when holding combat robot armor. Forces encountered in combat are typically sudden 'shock' loads that may have a high 'shear loading' factor. Ideally, mounting should be designed to prevent shear load on bolts, but combat impact vectors are unpredictable -- you need to design for all possible loads. <p> The desired material and temper of the bolts depends a great deal on the armor mounting style, but there are some general considerations. Grade 8 bolts are strong, but their added hardness results in a lack of 'toughness' needed to survive shock loads. Stainless steel fasteners have much greater toughness, but are not nearly as strong overall. Titanium falls in between, but the added expense and bother far outweigh any advantage. What you most commonly see in use are standard grade 5 steel bolts: greater strength than stainless and greater toughness than grade 8. The loss of strength can be made up by adding a few extra bolts. <img src="pic2/headsup.gif" border=0 style="max-width: 70%; display: block; margin: 0 auto;" title="Bolt heads"> If your bolt heads are exposed to possible spinner attack, you'll want to countersink the heads to prevent the spinner from grabbing exposed 'spinner bait' and tossing your 'bot and/or shearing the bolt heads. <p> Need more info on machine screws? <a href="http://store.curiousinventor.com/guides/Metal_Working/Screws">Curious Inventor: All about screws</a>. <p> You might also be interested in searching the <a href="AskAaron/materials.html">Ask Aaron Materials and Components archive</a> for 'shock mount'. </font><hr class="box"> <font color="#C22222"> Q: Hey, Mark! I've been goofin' around with the Tentacle Calculator, and I've come up with a couple questions about it: <p> <img src="pic2/shufflebot.jpg" border=0 style="float: right; max-width: 35%; margin: 0 10px 5px 20px;" title="Combat shufflebot 'Fission Product'"> 1) Is there a way to determine the gearing ratio on a robot with a chain or belt-driven drive with front and rear wheels of different sizes? For instance, the rear wheels are 3", and the front wheels are 4". The rear has, say, a 1.75" sprocket, the motor itself has a 2" sprocket, and the front has a 3" sprocket. These aren't real numbers, they're just random numbers to be used as an example. <p> 2) Is there a way to determine the speed of a shufflebot? I ask because the calculator does calculations for wheels, and IDK if there's a way to calculate for shufflebots. <p> Thanks again! [Jacksonville, Illinois] </font><p> A: <font color="#116644">[Mark J.] By the numbers... <ol class="x"> <li> If you're driving front/rear wheels of different diameters, the front/rear sprockets/pulleys should be in the same proportional diameters as the wheels to avoid wasteful tire 'scrub'. In your example: <ul class="blue"> <li>The front wheels are 4" diameter with 3" sprockets, making the sprockets 75% of the wheel diameter. <li>The rear wheels are 3" diameter, so their sprockets should also be 75% of their diameter: <nobr><span class="x">3" * 75% = 2.25"</span>.</nobr> </ul> If the proportions of the wheels and sprockets are correct on front and rear, entering the gear reduction for either set of sprockets and tire diameters into the Tentacle Calculator will give the correct result. <li> I'll tell you what the speed of a shufflebot is - <nobr><span class="g">it's too damned slow</span>.</nobr> The faster you try to go the bouncier it gets. At speed you spend as much time with the shufflepods in the air as on the ground and a lot of the drive energy goes into making the whole robot shake. Think 'robot with hexagonal wheels'. <p> If you want an estimate from the Tentacle calculator of how fast it <i>would</i> be going if it wasn't hopping, double the offset distance for a lobe on the shufflepod cam and enter that value as the 'wheel' diameter. But seriously... </ol> </font><hr class="box"> <font color="#C22222"> Q: How much can the performance of a brushless ESC be improved by swapping capacitors? <p> I saw on <a href="http://www.etotheipiplusone.net/?page_id=6">Charles Guan's website</a> when he was learning brushless drive setups that he swaps the capacitors out on all his ESCs for high-performance capacitors. I know this is supposed to help shield the ESCs and prevent burnouts from current surges when the motors are pushing at low RPMs, but how much does it help, and how much should I upgrade the capacitance of my ESC? <p> To be more specific, I have a 30 amp brushless ESC with a pair of 25v 550 uf capacitors. Would it make sense to swap those for a pair of 35v 2200 uf capacitors? They only weigh 6 grams and the ones I'm losing are probably 3, so if I can get any increased survivability for my ESC that kind of weight would be worth it. <p> The ESC will be running a .102 Ohm 4S 580kv brushless motor with a 1.8:1 pulley reduction to power a large horizontal spinner (about .0025 Kg M2). <p> Also, I read on some hobby forums that ESC capacitors should generally be rated at twice the voltage of the system, is that true? My system is 15v, and the current caps on the ESC are 25v so is it worth it upgrading for that alone? <p> Thanks again for all your help! The bot is coming together nicely and I've registered for the Robothon in Seattle in October. [Mark from Vancouver] </font><p> <img src="pic2/e-caps.jpg" border=0 style="float: right; max-width: 30%; margin: -5px 10px 5px 20px;" title="Electrolytic capacitors"> A: <font color="#116644">[Mark J.] How much extra salt should you shake onto your hamburger? Some need a little, some need a lot, some have too much already. <p> Charles Guan is an MIT engineer who designs and manufactures ESCs in his spare time 'cause he thinks it's fun. He absolutely knows what he's doing. If you're not a electrical engineering graduate of a respected school you're likely gonna to do as much harm as good by tinkering with the components of a complex digital electronic device. <p> That said, the little brushless ESCs robot builders 'borrow' from the hobby R/C aircraft industry are designed for very different performance targets than we expect from them in our applications. Bumping up the voltage rating of the filter capacitors will do no harm and may provide some level of extra reliability. <p> Blindly increasing the capacitance is another matter. I'm pretty sure that Charles Guan had his drive system fully instrumented and was watching voltage spikes on a oscilloscope as he changed the capacitor values. Simply pouring in more capacitance is shooting in the dark. <p> A drive motor ESC sees a lot of high-load/low-speed action that can benefit from added capacitance, but a spinner weapon ESC operates much closer to the propeller-spinning job for which the unit was designed. I'd suggest keeping the factory capacitance value as-is unless you discover a specific reliability problem as too much capacitance can adversely effect high-speed operation. If you really want to tinker, keep the increase to no more than double the original value. I suspect that most spinner ESCs fail for reasons that more capacitance isn't going to overcome. <p> P.S. - I'm happy to hear that your build is going well and that you're registered for Robothon - that's a great event. Say 'hi' to the Seattle crowd for me. </font><hr class="box"> <font color="#C22222"> Q: I've had difficulty sourcing tool steel for my beetleweight bar spinner, so I've been looking into methods to harden mild steel. Have you heard of <a href="http://magichammer.freeservers.com/robb_gunter.htm">Robb Gunter's "Super Quench" method</a>? It sounds like you can get a good facsimile of tool steel out of mild steel fairly easily (well, as easy as other home blacksmithing techniques anyhow). <p> Have you heard of this method, or do you know of any teams who have tried this? Would it be effective for a bar spinner? I think I'm going to give it a shot, unless I hear a good reason not to. [Mark from Vancouver - again] </font><p> A: <font color="#116644">[Mark J.] What do the things in this list have in common?</font> <div class=box style="margin: 20px auto; text-align: left; padding: 0 15px 0 0;"> <ul> <li>Apricots cure cancer. <li>Global warming is a hoax. <li>Chain letters are like free money. <li>Goat pheromones will make you irresistible to women. <li>Elvis is alive in a nuclear submarine under the polar ice cap. <li>Detroit suppressed a device that attaches to your car's air filter and doubles gas mileage. <li>Hillbilly metallurgy is awesome. </ul> </div> <font color="#116644">Give up? They're all things that you'd really like to believe are true but absolutely aren't. <p> There's a long list of desirable and required metal properties for spinner weapons, and if Billy Bob's mystical backyard hardening provided a reasonable mix of those properties you wouldn't have to search the back alleyways of the internet to find out about it. Don't waste your time. <p> Tool steel and abrasion resistant steel are fine spinner materials, but if you can't lay hands on them a nice bar of 'cheap and widely available' 4130 steel (AKA 'chromoly') is your go-to substitute. You can harden chromoly using standard practices and when you're done you'll know what you've got. <rem> <div class="framed" style="width: 95%; background-color: #EEE;"><font color="black"> <center><span class="x">A little more about 'Super Quench'</span></center> <p> The lower the carbon content of steel, the faster the cooling temperature drop has to be in order to create the crystaline structure needed to harden that alloy by heat treating. 'Mild steel' has a very low carbon content (0.05% to 0.30%) and is generally not hardened by heat treatment because the techniques needed to chill mild steel quickly enough to achieve barely significant hardening are simply not worth the effort. It's ever so much simpler and more productive to start with a higher carbon alloy. <p> So far so good, but then some backyard metal bangers dredged up work done by a metalurgical researcher who was able to add a little heat hardening to "unhardenable" mild 1018 alloy steel as kind of a parlor trick. The internet has built this 'super quench' mild steel up to mythical proportions, touting it as a substitute for tool steel. In truth, the stuff isn't even a match for common low-alloy steels.</font> </div> </font><hr class="box"> <font color="#C22222"> Q: Hi Mark, <p> I'm designing a 'Breaker Box' style rammer bot for 15# competition. I was curious about different types of drive motors. There are several variations that will allow the full pushing force, but I imagine a higher torque motor would win in a pushing match. In my area, Leopard and Castle Creation 540 size motors attached to Banebots gearboxes are most common. I was curious if you can use an outrunner with the same or similar bolt pattern, hooked up to a Banebots gearbox, as a drive motor. I know AmpFlow motors are all the rage in the higher weight classes, would one be suitable here? <p> I was also wondering how to maximize grip on the area floor. I have cut treads in tire and clean my wheels religiously with mixed results. Do lower shore hardness wheels offer better grip, ex green banebots vs black banebots or Colsons? Has anyone had success with adding "grip" to the tire? I was thinking studs like Riobots did, low grit sandpaper, two sided tape or something that can be sprayed on that adds grip. <p> Your insight and experience is much appreciated. [Pittsburgh, Pennsylvania] </font><p> <img src="pic2/bear2.gif" border=2 style="float: right; max-width: 30%; margin: 0 10px 5px 30px;" title="Search the archives!"> A: <font color="#116644">[Mark J.] You're asking about very popular design topics. A search of the <a href="AskAaron/design.html">Ask Aaron Combat Robot Design archive</a> yields 127 hits for 'traction' and 128 hits for 'pushing'. The <a href="AskAaron/motors.html">Ask Aaron Robot Motors and Controllers archive</a> has dozens of posts about using brushless motors for robot drive systems -- and there are several on this page. <p> Here are some quick topic highlights -- search thru the archives for details: <ul class="x"> <li> Brushless motors mated to assorted planetary gearboxes are VERY popular in sublight robot classes. There are plenty of examples and build logs to provide guidance, as well as many posts in the Ask Aaron archives. <li> Using brushless drive motors is much more complex than using brushed drive motors. Hobby grade brushless motors and controllers are borrowed from the R/C model aircraft industry and are made to spin lightweight propellers -- not push heavy robots. Getting the motor controllers repurposed to do this work is complex and often frustrating. <li> Torque is only useful to the point where the tires 'break traction' and start to slip. Torque past that point does not significantly add to pushing power. The <a href="javascript: void(0)" onclick="window.open('squid/newtorquecalc.htm','TorqueWin', 'toolbar=no,top=89,left=65,width=740,height=550,menubar=no,resizable=yes'); return false;"> Tentacle Drivetrain Calculator</a> is invaluable in designing a robot drivetrain for pushing power -- if you're using brushed motors. Click its 'Help' button for details. <li> The high performance AmpFlow motors are needlessly heavy for a 15-pound robot. You can get all the torque you need from much smaller/lighter motors. Want more torque? Increase the gearbox reduction ratio and/or go with smaller diameter tires to trade speed for torque. <li> For maximum pushing power get as much of your robot weight as possible onto your powered wheels. A 4-wheel drive robot with all the robot weight supported by driven wheels is a great start. Two-wheeled robot? The RioBots combat tutorial has a section on calculating center of gravity placement for 2-wheel robots to get optimum traction. <li> Want to win a pushing match? Get a wedge or lifter under your opponent to take weight off their drive wheels and put that weight onto your drive wheels. <li> Soft 'sticky' tires have better traction than hard tires when clean, but 'sticky' tires collect a lot of grit and dirt from the arena surface which eliminates their traction advantage. Cutting a tread helps tires shed grit and oil, but if your tires are super sticky you're fighting a losing battle. <li> Foam tires are soft but aren' great for traction. They can be coated with liquid latex or silicone sealant to improve their grip. <li> You can GREATLY improve traction with magnetic downforce -- if the arena surface is magnetic, and if the event allows such designs. You can also boost traction with vacuum fans. Search the design archive for 'vacuum'. While you're there, search for 'sumo'. </ul> </font><hr class="box"> <font color="#C22222"> Q: Hey Mark, question about insect-class pneumatics: <p> I understand that a larger cylinder bore equals more useable force, however, how do you calculate the limit of this, when the slower piston speed due to larger bore becomes a greater limitation than the additional force? <p> For example, say my valve has a flow rate (scfm) of 2.1469; I am thinking of switching from a cylinder with 5/8" bore to 3/4". Could you point me in the right direction, even external links on the math behind calculating this? <p> Thanks! [Utrecht, Netherlands] </font><p> A: <font color="#116644">[Mark J.] It's very difficult to model the speed of pneumatic systems, in part because of the interaction of multiple system elements on gas flow and in part because of the compressible nature of gasses. Ultimate force is easy, but actuator motion starts as the pressure first builds past the force preventing system movement and may be complete before the force even approaches full theoretical force. <p> You can find a discussion of factors effecting pneumatic system speed at the <a href="https://www.machinedesign.com/archive/air-it-out">Machine Design: Pneumatic Speed page</a>, and you can poke thru the <a href="RunAmok/pneu_tricks.html">Team Run Amok: Pneumatic Tricks page</a> for tips on improving speed. <p> <span class="x">In wildly over-simplified terms</span> both your speed and force are related to the cross-sectional area of the actuator bore: double the area = double the force and double the time to extend. <div class="framed"> Your existing 5/8" cylinder has a <nobr><span class="g"> * (5/16)<sup>2</sup> =</span></nobr> 0.307 in<sup>2</sup> cross-section area and your proposed 3/4" cylinder has a <nobr><span class="g"> * (3/8)<sup>2</sup> =</span></nobr> 0.442 in<sup>2</sup> cross-section area. <p> Switching to the larger actuator <i>should</i> yield <nobr><span class="g">(0.442 / 0.307) =</span></nobr> 144% of the original theoretical force, with full extension in 144% of the original time -- but that's not what you'll see in actual practice. There is no simple math to get real-world numbers. </div> If you're like most builders you picked your current components because they 'looked' about right given what you've seen in other 'bots. In general it's simply too difficult to quantify a combat robot pneumatic system design. From a practical standpoint, improvements to your system are best approached in an entirely experimental fashion: try something and see if it works. </font><hr class="box"> <font color="#C22222"> Q: I'd like to try brushless drive motors for a new robot, but I can't figure out how to input brushless motor data into the Tentacle drive train calculator. How do I calculate the stall torque and torque constant for a brushless motor? [West of the Pecos] </font><p> A: <font color="#116644">[Mark J.] The <a href="javascript: void(0)" onclick="window.open('squid/newtorquecalc.htm','TorqueWin', 'toolbar=no,top=89,left=65,width=740,height=550,menubar=no,resizable=yes'); return false;"> Team Tentacle Torque/Amp-Hour calculator</a> was designed for brushed motors and assumes an inverse linear relationship between motor speed and torque. Common hobby brushless motors <i>do not have</i> that speed/torque relationship, and the entire concept of brushless 'stall torque' doesn't really make sense. To further complicate the issue, the torque curve of a brushless motor is highly dependent on motor controller firmware and on the specific user-adjustable firmware settings. The Tentacle calculator is nearly useless for designing a brushless drive train. <p> See what successful bots in your weight class are using for brushless drive motors, gearboxes, ESCs, and (importantly) controller firmware/settings. In general you'll find motors with high Kv constants, high reduction ratio gearboxes, and controllers flashed with SimonK or maybe BLHeli firmware. Brushless is a whole lot more complex than brushed drive, and I'd strongly recommend that you start with a proven combination. Experiment after you have a working drive train. </font><hr class="box"> <font color="#C22222"> <img src="pic2/DX5C.jpg" border=0 style="float: right; max-width: 25%; margin: -15px 10px 5px 30px;" title="Spektrum DX5C transmitter"> Q: Great site! I'm getting a lot of good info as my son and I are building a beetleweight. <p> He wants to use a pistol-grip style radio, we're looking at the Spektrum DX5C with the SRS6000 receiver due to its built-in gyro. My concern is that it only lists a failsafe on the throttle channel. I see that some of the Spektrum receivers have the (sometimes undocumented) ability to switch to a mode where all of the channels will fail in the bind position if you bind it the right way, but I have not found any info on this receiver yet. <p> Looking through the radio archives, you have a lot of suggestions for radios/receivers with good (or at least passable) failsafe capabilities. However, when I search for them they seem to all be coming up as "discontinued" items. Do you have any suggestions for current receivers, or know of a good list somewhere? [Fredericksburg, Virginia] </font><p> A: <font color="#116644">[Mark J.] Well, now you've opened up the jumbo can-o-worms. Where to start... <div class="framed"> I'm assuming that you've found our <a href="RunAmok/radio_func.html">Robot Combat Radio Guide</a>, but in case you haven't I'm gonna suggest that you take the time to give that a read. And since you mentioned gyros, our <a href="http://runamok.tech/RunAmok/gyro.html">Guide to Combat Robot Gyros</a> will be handy as well. </div> Combat robots 'borrow' most of their R/C gear from model aircraft because their control needs are the closest to those of our machines. Better than 90% of the transmitters you see at tournaments are twin-stick aircraft units. A fair number of novice builders decide that pistol-grip or gamepad-style transmitters would suit them better because they are familiar with their use in R/C cars or gaming. The great majority of those builders soon realize that combat robots have much different control requirements than cars or games and quickly switch to twin-stick. I strongly suggest that you skip over the </nobr><span class="x" style="background-color: #666;"><i>"this doesn't work as well as I thought it would"</i></span></nobr> stage and buy a twin-stick radio to start, if only for the much greater selection and the much larger support base from other builders. <p> Radio gear has been changing at a ridiculous rate since Chinese manufacturers jumped into the game headfirst a few years back. New transmission protocols, open-source firmware, onboard serial networks... which is why all the receivers you've found in the radio archives are outdated and no longer in production. Our robots don't really need all this new fancy stuff that's aimed mostly at the drone market, but we make up such a tiny portion of R/C gear sales that we have to go along with whatever happens in the larger industry. <p> The upside of the Chinese R/C takeover is a stupendous drop in prices. The downside... well there are several downsides: <hr class="dash" style="width: 96%; display: block; margin: 20px auto; border: 2px dashed #A22;"> <ul class="blue"> <li> <span class="x">Unreadable Documentation</span> The quality and completeness of the manuals for Chinese R/C systems is truly awful. Here's an actual quote from one: <div class="framed" style="width: 95%;"> <font face="arial" color="#1122CC">The time-recorder is used calculating comparable bo stipulated time unexpectedly, or the possible time of flight under the state that the fuel fill it up with, it is very convenient. The pattern of the timer-recorder is the count-down. Pour time-recorder from set for time is it is it count to change, show surplus time at interface to begin.</font> </div>I recommend downloading the manual for any radio you consider purchasing to see if you can make any sense of it -- before you buy. I also recommend going with a system that is in use by a large number of combat robot builders, so that you have a knowledge base to tap when you realize the manual doesn't cover what you're trying to do. <li> <span class="x">Factory Support</span> There isn't any. That's why you need your friendly knowledge base. <li> <span class="x">Initial Quality</span> When you're paying $50 for a radio system with features that would have cost you $350 fifteen years ago, something's gotta give. The feel is cheap, the switches and gimbals wear out, and sometimes it doesn't work right out of the box. At these prices, you just go buy another one. Some are better than others. <li> <span class="x">Unreadable Documentation</span> I know I already mentioned this, but it's so bad I wanted to put it in twice. </ul> <hr class="dash" style="width: 96%; display: block; margin: 20px auto; border: 2px dashed #A22;"> <img src="pic2/taranisX7.jpg" border=0 style="float: right; max-width: 30%; margin: -5px 10px 5px 30px;" title="Taranis Q X7 transmitter"> Alright, so what do I recommend? I personally prefer Futaba radio gear such as the '6J' for high quality and <a href="http://manuals.hobbico.com/fut/6j-manual.pdf">excellent manuals</a> -- but they are not widely used in robot combat so a new user would not have the knowledge base of established users they might need. Consider one of these: <div class="box" style="text-align: left; margin: 20px;"> <span class="x" style="background-color: #128;">Flysky FS-i6</span> Probably the most common system in use in robot combat, and certainly a good choice for a first system. Comes with a very useable receiver that fully failsafes on all channels, with a wide variety of specialized receivers available should the need arise. <p> <span class="x" style="background-color: #128;">Taranis Q X7</span> A very sexy system widely used in robot combat. Better than usual quality, looks great, but it's a complex radio that will intimidate novice builders. Does not come with a receiver, but multiple full-featured receivers are available. </div> <span class="g">A quick word about 'failsafe'</span> As fully discussed in the Robot Combat Radio Guide, there are at least three different things a receiver can do to on signal loss that qualify as a 'failsafe'. Some of these are suitable for robot combat, and some are not. Make sure you understand the differences. <p> <span class="g">One last thing</span> I don't recommend receivers with built-in gyros. A gyro has to be specifically oriented within the robot relative to 'up' and 'forward'. This can make fitting your receiver-gyro unit into a small robot awkward. Robots also have special requirements for gyro shut-off when the robot happens to be inverted that a receiver-gyro combo is unlikely to provide. I you want a gyro, get a stand-alone unit. <p> Sorry for the long and rambling answer, but I did warn you that this is a big can of worms. If you'd like to hear other opinions on this subject there is an active 'Combat Robotics' group on Facebook that would love to give you a full spectrum of opinion -- and then some. </font><hr class="box"> <font color="#C22222"> <img src="pic2/hazard_2001.jpg" border=0 style="float: right; max-width: 40%; margin: 0px 10px 0 20px;" title="Combat robot 'Hazard'"> Q: Hi Mark, I'm working on a hobbyweight horizontal spinner and wanted your opinion. There are spinners like 'Last Rites'/'Tombstone' that ping pong like a fbs after impact and others like 'Hazard' that barely turn. I looked in the forum and read up on Hazard's faux clutch and don't fully understand it. So really 3 questions: <ol class="x"> <li>Is a clutch needed for a 12" bar spinner in this weight class? <li>Does it make a difference if the bot is 4wd? <li>If a clutch is needed, how do you make one? </ol> I looked on McMaster Carr and they have clutches, but I do not know if they are suitable. <p> Thank you for your time and insight. [New&nbsp;York] </font><p> A: <font color="#116644">[Mark J.] There have been a lot of questions from builders about weapon clutches here at 'Ask Aaron'. A search of the <a href="AskAaron/weapon.html">Ask Aaron Robot Weapons archive</a> shows 51 hits for 'clutch', including a few that discuss the odd pressure clutch used by 'Hazard'. You'll be interested in reading thru those earlier posts for additional depth on the subject, but I'll summarize important points here. <ul class="blue"> <li> 'Hazard' had a weapon clutch, and recent versions of Ray Billing's big bar spinners also have weapon clutches. The presence or absence of a clutch isn't what accounts for the difference in their reaction on impact. <li> 'Tombstone' has its huge bar spinner way out in front of the 'bot. The point of impact is a good distance away from the robot's center of mass, which is not far ahead of the two drive wheels. That distance gives a lot of lever advantage to the reaction force from a weapon impact to spin the 'bot around. Combined that with the enormous kinetic energy of the monsterous weapon and you've got the reason for the 'hockey puck' reaction of Ray's 'bots on impact. <li> 'Hazard' had the axle for its spinner centered in the square formed by its drive wheels. The point of impact was much closer to the robot's center of mass, which was surrounded by tires that would have to be dragged sideways across the floor to spin the 'bot around. That makes for much less reaction to a weapon impact. <li> The purpose of weapon clutch is to protect the weapon drive components from damage from an abrupt decelleration when the weapon strikes. The weapon motor and belt/chain drive build up a lot of kinetic energy of their own and the shock-loading from a sudden stop can overstress shaft interfaces, bearings, and hubs. The larger the robot, the more of a problem this is, and I'd put a hobbyweight into the 'probably need' category. Even a little 'slip' in the system can go a long way toward saving the weapon drive. <li> The simplest and most common method of providing that little bit of 'slip' is to use a belt drive to transfer power from the motor to the weaon. A V-belt is common for large 'bots, and 'round' belts are common in sub-lights. An alternative is to use a widely available toothed 'timing belt' and pulleys, but to machine away all or most of the depth of the 'teeth' on one of the pulleys to allow slippage under high load. <li> <span class="x">Do Not Even Think</span> about direct driving a 12" spinner with an unmodified brushless motor -- with or without a clutch. The side-loading from a weapon impact would immediately destroy the motor. There are a very few hobbyweight direct drive weapons, but they use custom fabricated hub motors with huge axles designed to take the load. </ul> For what it's worth, I don't understand Hazard's clutch either. The weapon bar is squished in place on the shaft between two phenolic washers by a shaft collar. I've got a really good picture of the collar, but I can't figure out how you get enough 'squish' pressure from the collar to hold the weapon bar firmly enough. If anybody happens to run into builder Tony Buchignani do me a favor and ask him, wontcha? </font><hr class="box"> <font color="#C22222"> <img src="pic2/step_drum.jpg" border=0 style="float: right; max-width: 40%; margin: 0px 10px 0 20px;" title="Single Impactor Drum Weapon"> Q: Hi Mark, it's drum spinner guy again. Here is my weapon design thus far. The length is fixed, the radius is flexible, but the larger the better obviously for energy storage. I fell it's overbuilt just because of its weight, but wanted your take. This is for a 15# robot. <p> Mostly, I want to know if I can use a thinner drum as it is currently 3/8 aluminum. I am trying to maximize bite so I was only planning on spinning it to 5000 rpm and have it store around 2000 joules while having a max bite between 12.5 and 25 mm. Any advice is, as always, much appreciated. [Pittsburgh] </font><p> A: <font color="#116644">[Mark J.] Looks like a classic drum -- no problems with what I can see, but your comments raise a couple points: <ul class="x"> <li> The photo of the drum attached to your earlier posts a bit down the page is from a 12-pound robot that fought more than ten years ago -- before LiPo batteries and brushless weapon motors raised weapon energy levels to the high levels seen in current competition. It spun much slower than you plan to spin your drum and faced opponents with much less damaging weapons than are seen today. Comparing your CAD to that photo and updating to current standards of combat, I don't believe your proposed drum is 'overbuilt' at all. <li> You say the drum will be built from aluminum -- but there's <i>aluminum</i> and then there's <nobr><span class="x">* A L U M I N U M *</span></nobr>. <div class="framed"> <ul class="blue"> <li> If you're making a drum of nasty, soft aluminum alloy like '<a href="https://en.wikipedia.org/wiki/3003_aluminium_alloy">3003</a>': the drum is gonna get gashed/slashed/crunched and will need to be very thick to survive. <li> If making a drum of heat-tempered 'aircraft' alloy like '<a href="https://en.wikipedia.org/wiki/7075_aluminium_alloy">7075</a>': the drum will be harder, stronger, and can me made with a thinner wall. </ul></div> The question of <span class="g">"How much thinner?"</span> will be answered in combat. <li> If you're designing to get a realistic 25mm 'bite' you'll want an impactor tall enough to take advantage of that bite: about 25mm. You want to have the 'reach' to impact your target before it can penetrate far enough to impact your drum! </ul> </font><hr class="box"> <font color="#C22222"> Q: My antweight horizontal bar spinner bot currently uses: <ul class="x"> <li>two 22.2:1 silver sparks for drive paired with the tinyESC's, and <li>an EMAX 2204 weapon motor, driven by a 12a BLHELI esc. </ul> I'm thinking about switching the brushless ESC to a 20a. The whole bot currently runs off of a single Turnigy nano-tech 450mAh 3S 65C Lipo. Can that battery handle the upgraded ESC? [Ballwin,&nbsp;Missouri] </font> <p> A: <font color="#116644">[Mark J.] There are some fairly common misconceptions about hobby-grade brushless ESC amperage ratings that I need to clear up: <div class="framed" style="max-width: 700px;"></font> Increasing the current rating of your brushless weapon ESC will do <u><i>absolutely nothing</i></u> to the current drain on your battery or to the performance of your weapon.<font color="#116644"> </div> <ul class="x"> <li>Your '12 amp" brushless speed controller does not <i>use</i> 12 amps of current. It can safely <i>control</i> up to 12 amps of current flowing thru it for use by the weapon motor. <li> The hobby-grade brushless ESCs borrowed from model aircraft <u>do not</u> monitor or limit the current flowing thru them. It is the weapon motor and the load placed on it by the weapon that determine the current consumption of your weapon system. <li> A 12A rated brushless ESC can <i>safely</i> flow 12 amps of current for a long period. However, if the load on the weapon motor has it 'asking' for 50 amps, your battery will push 50 amps thru your 12A rated BESC -- until the ESC vaporizes. <li> Replacing your 12 amp rated brushless ESC with a 20 amp rated brushless ESC <u>will not</u> provide more current to your weapon motor. The ONLY reason to move to a higher amp rating is if the ESC you <i>were</i> using failed due to overload. </ul> If you are looking for increased weapon motor performance, bump up the voltage or go to a higher output motor. </font><hr class="box"> <font color="#C22222"> Q: So, My Favorite BattleBot is 'Chomp' (The newer one even though I also Like the older one from season 3.0). I was wondering if 'The Machine Corps' (AKA the team that built 'Chomp') made any other robots for smaller comps? Also I am a huge fan of 'Run Amok' in Robotica! [Lynn,&nbsp;Massachusetts] </font><p> <img src="pic2/chomp.jpg" border=0 style="float: right; margin: 10px 10px 10px 20px;" title="Combat robot 'Chomp'"> A: <font color="#116644">[Mark J.] Thank you for the mention of <a href="http://runamok.tech/RunAmok/retire.html">Run Amok</a> -- several fans from our team's early days have contacted me recently with kind comments, stories, and memories. I'm also glad to hear from a fan of 'Chomp'. The robot and team get a lot of flack on the forums and they deserve more respect. <p> Due to elevated acceptance standards and heightened expectations associated with the ABC BattleBots reboot, many of the current teams are 'super groups' whose members each bring expertise from earlier independent robot projects. Although 'The Machine Corps' was formed for Battlebots and had no previous combat experience <i>as a team</i>, their members bring serious credentials: <ul class="blue"> <li> Jascha Little and Scott Little were founding members of '<a href="http://web.archive.org/web/20031026104002/home.austin.rr.com/machinegod/">Team Mechanicus</a>' who campaigned BattleBots legend and <a href="http://runamok.tech/hall_of_fame.html">Combat Robot Hall of Fame</a> robot 'The Judge'. <li> The Littles were joined by Zoe Stephenson and Jo Balme as members of 'Team Survey', a non-combat robotics team that won the NASA '<a href="https://www.nasa.gov/directorates/spacetech/centennial_challenges/sample_return_robot/srr_results_2013.html">Sample Return Robot Challenge</a>' in 2013. </ul> You might be interested in this podcast of "<a href="https://www.spreaker.com/user/thefanshow/episode-50-zoe-chomp ">The F.A.N. Show</a>" that features an interview with team captain Zoe Stephenson about her start in robotics and BattleBots. Zoe's segment comes about 30 minutes into the show. </font><hr class="box"> <font color="#C22222"> Q: Hi Mark, is a <a href="https://www.mcmaster.com/#standard-threaded-standoffs/=1dyepev">threaded round standoff</a> generally usable as a dead shaft for an antweight vertical spinner? I am not sure how much force the weapon shaft has to take. After looking at the tensile strengths, a 1/4" aluminum standoff has 45,000 PSI tensile strength, while a 1/4" stainless steel standoff has 80,000 PSI tensile strength. <p> I am wondering if there is a standoff that is usable, and why the stainless steel standoff has a higher tensile strength. Thank you. [Bellevue, Washington] </font><p> A: <font color="#116644">[Mark J.] Designing a combat robot certainly would be much easier if you could look up a single material property for an item to determine its suitability for a broadly defined application. Unfortunately, that isn't how it works. <div class="framed"> <ol class="blue"> <li> Check <a href="AskAaron/FAQ.html">Frequently Asked Questions</a> #17 for an explanation of why I genuinely cannot answer your question with the information you have provided. <li> <a href="">Tensile strength</a> is the ability of a material to resist a 'pull' force -- as opposed to a 'push' force or a 'bend' force or a 'shear' force or an 'impact' force. It tells you very little about the suitability of a material to perform the function of a shaft in an un-dimensioned weapon only broadly categorized to a weight class. <li> 'Standoffs' are little more than convenient spacers for mounting components in cabinents or panels. They are not designed or intended to be subjected to large structural loads, and the materials from which they are made are selected accordingly; they aren't 'strong'. <li> The '18-8' stainless steel standoff has a greater tensile strength than the unspecified aluminum alloy standoff because food-grade stainless steel has greater tensile strength than basic aluminum alloy. There are a great many different <a href="https://en.wikipedia.org/wiki/Steel">steel compositions</a> with wildly different properties, and the same is true for aluminum. As noted above, 'standoffs' aren't made for strength as much as they are to meet corrosion, weight, or electrical specifications. </ol></div> What you're looking for in a weapon shaft is a solid rod of 'tough' steel intended for a similar purpose -- a <a href="https://www.mcmaster.com/#steel-rods/=1dyff66">carbon steel drive shaft</a> could be a good choice. Diameter will depend on your design parameters for both shaft support and weapon energy level. Start with what successful robots with similar weapon designs are using. If it breaks, make it stronger. </font><hr class="box"> <font color="#C22222"> <img src="pic2/fdisk.gif" border=0 style="float: right; margin: 5px 20px 10px 0px; max-width: 50%;" title="Asymmetric spinner weapon"> Q: How can you design a single impactor or snail style drum weapon and assure it is balanced? Every time I start to design one in <i>Autodesk Inventor</i>, I keep making it an egg beater or really asymmetrical, and doubt its balance. [Pittsburgh,&nbsp;Pennsylvania] </font><p> A: <font color="#116644">[Mark J.] The <i>Autodesk Inventor</i> CAD program can <a href="https://knowledge.autodesk.com/support/inventor-products/learn-explore/caas/CloudHelp/cloudhelp/2016/ENU/Inventor-Help/files/GUID-5A8F73C1-B19C-4DCA-85F3-B7AEF252632D-htm.html">display an object's center of gravity</a>. Hover over the CG to display its coordinates. <ul class="blue"> <li>If the center of gravity is centered on the axis of rotation of your drum, it's balanced. <li>If not centered, move the axis or add/move some mass until it is. </ul> Here's a video of builder Marcus Quintilian <a href="https://www.youtube.com/watch?v=nVCdjNSpPB4">designing a Single Tooth Disk on <i>Fusion 360</i></a> -- the process is similar in <i>Inventor</i>. </font> <p> <font color="#C22222"> <img src="pic2/drum.jpg" border=2 style="float: right; margin: 10px 10px 10px 10px; max-width: 27%;" title="Drum impactor recessed and bolted"> <img src="pic2/tooth2.png" border=2 style="float: right; margin: 10px 0px 10px 20px; max-width: 25%;" title="Recess impactor to remove shear on screws"> Q: Hi, single tooth drum guy again. What screws are recommended for attaching an impactor to a drum? It is bad design practice as the force on the screws is sheer force, but I do not see another way around it. Just looking at alternatives to a unidrum as it gets very complicated very quick. </font><p> A: <font color="#116644"> You haven't mentioned the weight class of your 'bot, and impactor strength issues increase rapidly by weightclass. I'll need to be a bit general. <p> Impactor failure from shear at high weapon energy levels is what led to the development of unidrums. Machine screws are made for optimal tensile strength at the expense of shear resistance, and you REALLY can't expose screws to impactor shear forces anywhere above insect level weapons. <p> If you're going to attach drum impactors with screws you'll want to machine a recess into the drum such that the lateral impact force is transferred directly to the drum. The retaining screws are isolated from shear and serve only to pull the impactor down into the recess. See diagram and photo at right. </font><hr class="box"> <font color="#C22222"> Q: I'm confused. Didn't anyone got to pick there own Loanerbots in Robot Wars Extreme Warriors? [Clay, New York] </font><p> A: <font color="#116644">[Mark J.] 'Ask Aaron' no longer answers questions about UK Robot Wars for reasons discussed in <a href="AskAaron/FAQ.html">Frequently Asked Questions</a> #37. </font><hr class="box"> <font color="#C22222"> <img src="pic2/opto.jpg" border=2 style="float: right; margin: -5px 10px 10px 30px; max-width: 50%;" title="an 'OPTO' brushless ESC"> Q: I see several different brands of brushless ESCs labeled 'OPTO'. What does that mean? When would I want 'OPTO'? Would it ever be a bad thing? [Pomona,&nbsp;California] </font><p> A: <font color="#116644">[Mark J.] A complete answer requires a bit of history. <p> <span class="g">Back in the day...</span> <p> The small, high-power <i><u>brushed</u></i> motors powering early electric model aircraft created a huge amount of high-frequency electrical 'noise' and voltage spikes from the arcing of the motor brushes at high speed. This 'noise' traveled along the power wires and found its way to the sensitive and vulnerable electronics in the R/C receiver, wreaking havoc with reception. <p> To protect the receiver from this electrical noise, 'OPTO' speed controllers included a device called an <a href="https://en.wikipedia.org/wiki/Opto-isolator">optical isolator</a> in the line between the receiver and the power circuits. This 'opto-isolator' converted the receiver output signal to a modulated light beam, then back to an electrical signal for the ESC. Electrical noise couldn't jump back across the optical gap to get to the receiver. Genius! <p> <span class="g">But there's a catch...</span> <p> If you use a battery eliminator circuit (BEC) to power the receiver from the main battery pack the electrical noise can use it as a path to the receiver, nullifying the benefit of the opto-isolator. Fully isolating the receiver from motor 'noise' requires that the receiver have it's own battery, so OPTO ESCs had no BEC. Inconvenient, but it worked. <p> <span class="g">Jump to present day</span> <p> Brushless motors have replaced the 'noisy' brushed motors in model aircraft and the need for opto-isolation no longer exists in most applications. Few brushless 'hobby' ESCs have an optical barrier to electrical noise, yet many still carry the OPTO label. In current useage it's simply an indication that the ESC has no battery eliminator circuit. Eliminating the BEC shaves off a couple grams of weight and eliminates the need to 'clip' the red power line in the receiver cable when multiple BEC equipped ESCs are on the 'bot. <p> You need <i>something</i> in your power system to provide power to your receiver, and a convenient way to do that is to make sure that <i>one</i> of the ESCS for the weapon or drive motors has an BEC -- but you only need one. </font><hr class="box"> <font color="#C22222"> Q: I'm new to brushless motors and having trouble setting up the Plush 30A ESC for my weapon. When I switch on the robot power the Plush keeps beeping and I get no response from the motor. What's the problem? <nobr>[West Aether, North America]</nobr> </font><p> A: <font color="#116644">[Mark J.] All the Plush ESCs use beep tones to communicate their status and alert you to problems. Since you say it 'keeps beeping' we can rule out the normal startup tones that tell you everything is OK. The 'keeps beeping' codes are: <ul class="blue"> <li> <span class="x">Fast individual beeps</span> <span class="g">four per second</span> - the transmitter stick/switch is not in the 'zero throttle' position. Correct the transmitter throttle position and the startup sequence will continue. <li> <span class="x">Slow individual beeps</span> <span class="g">every two seconds</span> - no throttle signal detected. Check the ESC connection to the receiver and that the receiver has power. Check that the transmitter is has on and correctly bound to the receiver. <li> <span class="x">Two beeps and a pause</span> <span class="g">once per second</span> - the voltage applied to the ESC power leads is out-of-range -- usually too low. Charge your battery and check the power connections. </ul> Refer to the <a href="https://hbfpnl.files.wordpress.com/2009/11/turnigy-plush-esc-user-manual.pdf">Turnigy Brushless ESC manual</a> for other beep codes and the correct start-up sequence. </font> <p> <font color="#C22222"> Q: Got it! It was a low voltage issue. Now I have a new problem. My outrunner weapon motor spins up fine without the weapon, but with the weapon attached it spins very slowly and at an uneven speed. The battery is fully charged, I've checked all the connections, and the weapon spins freely by hand. Any ideas on what might be wrong? </font><p> A: <font color="#116644">Robot builders 'borrow' brushless motors and ESCs from the model aircraft hobby market. These products are designed to spin low-mass propellers, and the firmware in the ESCs are designed for that purpose. When you hang a big, high 'Moment of Inertia' bar/disk/drum off an unsensored hobby brushless motor the ESC 'firmware' may not know how to handle that type of load and gets stuck in its 'startup' sequence. This is usually more of a problem with robot drive than with spinner weapons, but it does crop up and can be very frustrating. It's called 'cogging'. <p> There are adjustments to the Plush firmware settings that may help. Instructions for entering the ESC programming mode are given in the Turnigy Brushless ESC manual linked above, but I think you'll be better off watching <a href="https://www.youtube.com/watch?v=cj7yLk41kwY">a video of the programming process</a>. It's more than a little confusing, and you might be interested in purchasing an inexpensive <a href="https://hobbyking.com/en_us/turnigy-besc-programming-card.html">Plush Programming Card</a> to avoid all the beep-counting and stick-throwing. <p> There are six settings that are user-adjustable, but for this problem you'll be interested in 'Timing' and 'Startup Mode': <ul class="blue"> <li>Start with 'Timing'. The Plushes default to 'Low' timing advance, but your outrunner will likely do better with timing set to 'Medium' or 'High'. Try all the settings and keep the best response. <li>If the best timing setting hasn't cured the problem you can try switching from 'Normal' startup to 'Soft' startup mode. There is also a 'Super Soft' mode, but the delay in spinup time is generally unacceptable. </ul> If you're still 'cogging' you may want to switch to a different ESC that has 'BLHeli' or 'SimonK' firmware, which have better startup performance in robot applications. </font><hr class="box"> <font color="#C22222"> Q: Last year I used a 3s 30c 450mAh battery on my wedgebot that uses four 22.2:1 silver sparks for drive. This year I'm switching to a 300mah battery with the same C rating, but I just now realized that this changes the amount of current the battery can supply safely. Am I still within a safe operating window for that battery? [Ballwin,&nbsp;Missouri] </font><p> A: <font color="#116644">[Mark J.] Let's do a quick check. The calculation is: <nobr><span class="x">'C' rating * Amp Hour rating = Safe Current</span></nobr>. For your new battery that works out to: <div class="box"><span class="g">30C * 0.300 Ah = 9 amps</span></div> The <a href="javascript: void(0)" onclick="window.open('squid/newtorquecalc.htm','TorqueWin', 'toolbar=no,top=89,left=65,width=740,height=550,menubar=no,resizable=yes'); return false;"> Tentacle Torque Calculator</a> can estimate the peak current consumption of your drivetrain. It reports that a FingerTech Silver Spark motor at 11.1 volts (3s) will consume 2.4 amps at stall, so if you somehow manage to stall all four of your drive motors at the same time you could pull as much as <nobr><span class="x">4 motors * 2.4 amps = 9.6 amps</span></nobr> -- but you aren't gonna stall all those motors! <p> You didn't tell me the weight of your 'bot or the size of the wheels, but a 'worst case' four-motor <i>beetleweight</i> with overly large 3" wheels would break traction at around 1.5 amps per 22.2:1 Silver Spark for a max 6 amp total battery drain. Your battery is safe. </font><hr class="box"> <div style="display: table;"> <font color="#C22222"> Q: Hi Mark, <p> I have looked high and low and cannot seem to find the motor I would like. I would like a flat motor (no taller than 2") that runs on 24 volts. It will be used as a weapon motor for an overhead spinner with a 20" or so bar weighing between 4.5 and 6.5 pounds. By my rough calculations, 250 kv and 4 Nm of torque would be ideal, but 150 kv with 8 Nm of torque would also work. Any websites or brand suggestions would be much appreciated. <p> Many Thanks! [Pittsburgh, PA] </font><p> A: <font color="#116644">[Mark J.] There's a reason you can't find that motor. Robot builders 'borrow' weapon motors from the model aircraft hobby industry, and the motor you're looking for is... <img src="pic2/copter.gif" border=0 style="float: right; margin: 20px 20px 10px 30px;" title="Helicopter"> <ol type="A" class="blue"> <li>Very specific; and <li>Fits into no model aircraft niche. </ol> No airplane/helicopter/quad would have a use for a motor with those specs, so nobody makes such a motor. Redesign. </font></div><hr class="box"> <font color="#C22222"> Q: Hey Mark, fellow Willamette Valley-ite here again <img src="pic2/smile.gif"> <p> So here's where I'm at. I recently built a brand new hobbyweight. Spent months on the design, meticulously selected components, machined every part, and promptly went 0-2 in my first competition. <p> <img src="pic2/shear_fail.jpg" border=2 style="float: right; margin: 5px 10px 10px 30px; width: 320px; max-width: 50%;" title="Hobbyweight combat robot gearbox/hub CAD"> The flaw lay in a very poor hardware choice. The output shafts for my drive gearboxes have a 3mm hole. I designed wheel hubs to slip over the shaft and used an M3 alloy bolt to lock the shafts to the hubs. Bad idea. About a minute into each fight, both bolts sheared and turned my bot into a very expensive paper weight. I didn't take any major hits, and I believe that the bolts sheared solely from the torque of the motors turning the wheels back and forth. <p> I am now wondering if a 3mm hardened pin will be sufficient to lock the hubs to the shafts. The ones I have in mind have a 1600lb shear rating. I emailed McMaster-Carr to try and get a shear rating for the bolts so I could compare, but they said that they don't test shear on their bolts. I am wondering if the pins would hold up, or if I should completely redesign the hub? <p> I'm running 12 volt Johnson RS-550 motors (40:1 reduction). Also attached is my CAD of the hub and gearbox. <p> As always, I appreciate your input very much! [Albany, Oregon] </font><p> A: <font color="#116644">[Mark J.] That's what's so great about combat robotics; you learn all sorts of unexpected things that you wouldn't run across in a normal lifespan. Sometimes it's fun, sometimes it's painful. <p> Bolts are designed for optimal tensile strength at the expense of shear resistance. Make that 3mm bolt out of alloy instead of steel, add in the leverage advantage of a (perhaps) 50mm radius wheel on the outer surface of a 2.5mm radius shaft, and then try to abruptly reverse the momentum of a 12-pound robot moving along at 9 MPH, and presto -- shear failure. <ul class="x"> <li><span class="x">The Good News</span> Replacing the alloy bolt with a 3mm hardened steel pin will very likely eliminate the shearing problem as the weak link in your driveline. <li><span class="x">&nbsp;The Bad News&nbsp;</span> Shearing the alloy bolt was probably all that prevented the failure of the small gearbox output shaft with the large cross-drilled hole. </ul> Based on your CAD, the gearbox shaft is very small for a hobbyweight, and that 3mm hole removes a great deal of the shaft strength at a critical location. A 3mm cross-drill thru a 5mm shaft removes more than 70% of the shaft material at the minimum cross-section. The hardened pin will transfer the torque load directly into that weak area of that shaft -- which will be your new failure point. <p> If those shafts are as small as they appear you don't just need new hubs, you need new gearboxes. For a hobbyweight, I'd look for minimum 8mm diameter steel shafts with no cross-drilled holes. </font> <p> <font color="#C22222"> <img src="pic2/shear_fail2.jpg" border=2 style="float: right; margin: -5px 10px 10px 30px; width: 320px; max-width: 50%;" title="Proposed fix for a weak gearbox."> Q: So it sounds like a hardened pin isn't going to be my simple solution. I don't know of any other offset gearboxes that I could switch to and fit inside the robot in the same way. I'm trying to avoid redesigning the whole bot and have a couple ideas. I could try to modify the gearboxes and install a larger shaft, but I'm sure that is easier said than done. My other idea seems a little more appealing (for the moment). <p> I was thinking I could press fit a square hub (red in the picture) made out of a somewhat flexible plastic onto the existing shaft. This would take the cross-drilled hole out of the equation and add some flexibility. Is this a viable solution, or recipe for disaster? </font><p> A: <font color="#116644">I'm concerned that the gearbox weaknesses run deeper than the shaft -- why would there be combat-quality components up to but not including the output shaft? I suspect that you're going to chase a series of weak points thru the entire structure of those boxes, ruining your combat success for as long as you keep them. <p> I realize that you've invested effort and heart into your current design, but there are reasons your competition does not use those gearboxes. Cut your losses and start fresh. </font><hr class="box"> <font color="#C22222"> Q: Hi. I am building a 15 lb combat robot, and I have a 1700Kv Brushless Inrunner motor by Dr. Mad Thrust. I am running a 25v system with a reduction of 1:1.5 so the weapon will be spinning at around 28,000 rpm. Do you think this is too fast for the weapon? I have seen many beater bar robots spinning insanely fast, and the downfall of my last robot I believe was the weapon speed. I have attached my weapon so you can base your answer off of that as well. Thanks :) [Dublin, Ohio] </font><p> A: <font color="#116644">[Mark J.] Your drawing/CAD failed to 'attach' so I don't have the details of your weapon design. I'll have to be general in my comments. <ol class="x"> <li> It's unlikely that your actual weapon speed will approach 28,000 RPM even with a very powerful weapon motor. The Kv 'speed constant' value is accurate for an unloaded motor. As you add load to the motor the speed drops, and the aerodynamic load on a spinnng weapon increases with the square of speed. Spinning a weapon at 28K RPM requires four times the power needed to spin the same weapon at 14K RPM -- sixteen times the power needed at 7K RPM. Your weapon will fall farther off the calculated speed as aero drag increases, and will pull greater current in direct proportion to the increasing load. <li> Read thru the <a href="AskAaron/spinner_FAQ.html">Ask Aaron Spinner Weapon FAQ</a> for considerations in evaluating spinner speed. Note in particular the section about drums/beaters going 'weapon-to-weapon' against similar designs. </ol></font><hr class="box"> <font color="#C22222"> Q: What type of screws have the best hold in UHMW polyethylene? Can I tap threads and use machine screws? [Hershey, Pennsylvania] </font><p> A: <font color="#116644">[Mark J.] Depending on your specific needs, you have multiple options: <ul class="x"> <img src="pic2/barrel_nuts.gif" border=0 style="float: right; margin: 0px 10px 10px 30px;" title="cross dowel barrel nuts"> <li> The popular solution for structural joints is wood 'deck screws'. The coarse threads hold well in soft plastic. Drill a pilot hole and run 'em in. <li> Specialty 'Plastite' screws are great in firm plastics, but are harder to find and may not be worthwhile for soft UHMW. <li> Polyethylene is poor at holding fine tapped threads. If you want the strongest possible hold with machine screws you can cross-drill and insert <a href="https://www.amazon.com/s/?url=field-keywords=cross+dowel+barrel+nuts">cross-dowel barrel nuts</a>. This is way too much effort for a small 'bot, but might be handy for larger builds. <li> There are <a href="https://www.amazon.com/Threaded-Inserts/b?ie=UTF8&node=16410701">threaded inserts</a> to drive into soft plastic that then take machine screws. They're useful for screws that must be removed frequently. <li> <a href="https://www.amazon.com/s/field-keywords=heat+set+thread+insert">Heat-set threaded inserts</a> are not recommeneded for UHMW combat uses. </ul></font><hr class="box"> <div style="display: table;"> <font color="#C22222"> <img src="pic2/hats2.jpg" border=2 style="float: right; margin: 0px 10px 10px 30px; width: 360px; max-width: 50%;" title="Hats from Team Run Amok, Team Force, and Team Whyachi"> Q: hi mark. i was watching season 1 of "robotica" recently. is it pure coincidence that the ram force and whyachi teams have the same uniforms? [Philadelphia, Pennsylvania] </font><p> A: <font color="#116644">[Mark J.] Yes, kinda. Team Force made their TV appearance on Robotica a few weeks before Team Whyachi appeared on BattleBots, but neither team had seen the other when the shirts were selected. <p> When you order embroidered hats and shirts you typically pick from a selection of 'stock' clothing on which to put your logo. The red/white/black 'Pit Crew' shirts were common stock items at the time, and both teams independently picked them out of the catalogue.The Team Whyachi and Team Force hats, however, were quite different -- I have one of the 'Team Force' hats in my collection. </font></div><hr class="box"> <font color="#C22222"> <img src="pic2/malfunction.gif" border=0 style="float: left; width: 200px; max-width: 40%; margin: -10px 20px 0 10px;" title="Robot malfunction"> Q: Are Auto reset breakers a good idea for Amp spikes In a combat robot? [Hagerstown, Maryland] </font><p> A: <font color="#116644">[Mark J.] A better idea is to design your robot with components spec'd to handle the current loads -- with some to spare. You <i>really</i> don't want to be a sitting duck for 15 seconds while your breaker resets. <p> <span class="g">Additional Problem</span> Auto reset breakers are not designed for the physical shock loads combat robots experience. A sharp impact will trip the breaker well below its current rating, which makes them worse than useless. <p> <div class="framed" style="width: 96%;"> <span class="g">General Rule</span> Unless tournament rules require, don't put ANYTHING into combat that can shut down the robot without your intervention. This includes battery voltage cutoffs and any type of fuse. Audible warnings or telemetry alerts are fine 'cause they leave the critical decision to stop or continue with the driver. </div> Put in all the safegards you like for testing, but I'd much rather get a few more seconds out of a component and risk it failing than save the component and lose the match. If your budget is so low that you can't aford to burn a few components for a win you're in the wrong hobby. </font><hr class="box"> <font color="#C22222"> <img src="HOF/LM200.jpg" border=0 style="float: right; margin: -10px 10px 0 20px;" title="Hall of Fame wedgebot 'La Machine'"> Q: So I was thinking to start building an antweight for Massdestruction. I was thinking a overhead grappler (not a crusher) and a wedge. This is gonna be my first combat robot and I'm not even sure she I'm gonna build it. Is this a good one for beginners? Thanks! <nobr>[Turks and Caicos Islands]</nobr> </font><p> A: <font color="#116644">[Mark J.] I really ought to put this in the <a href="AskAaron/FAQ.html">Frequently Asked Questions</a>...</font> <div class="framed"> Your first combat robot should NOT have an active weapon; no spinner, no lifter, no flamethrower, no crusher. Keep it simple -- build a wedge. This is standard advice from multiple sources, and it is both for your benefit and the best interests of the sport. See <a href="AskAaron/events.html#firstbot">this post</a> in the Ask Aaron archives for a summary of the reasons. </div> <font color="#116644"><span class="x">Update</span> I've tucked this in as part of FAQ #8. </font><rem hr class="box"> <REM ========================================================> <hr style="border: 3px solid #55a; color: #ffffce; background-color: #ffffce; height: 7px; margin: 30px 0 5px 0;"><br> <img src="pic2/killer.jpg" border=2 style="float: right; width: 22%; min-width: 230px; margin: 10px 20px 10px 20px;" title="Killer Robot drawing by Garrett Shikuma"> <table border=0 bordercolor="#C0B090" style="margin: 0px 10px 5px 0px; border-collapse: collapse;"> <tr><td> <table class="top"> <tr><td rowspan=2> &nbsp; &nbsp;</td> <td> <B> <font size=+2 color="#4852C5">Remembering Aaron&nbsp;Joerger, 1991&nbsp;-&nbsp;2013</font></b><hr align=left size=4 noshade width=96%> </td> </tr><tr> <td><font color="#444444"> The 'Ask Aaron' project was important to Aaron, and I continue the site in his memory. Thank you for the many kind messages of sympathy and support that have found their way to me. <a href="obituary_Aaron_Joerger.html">Aaron's&nbsp;obituary</a> <div align=right style="margin: 5px;"><i> -&nbsp;Mark&nbsp;Joerger&nbsp;&nbsp;&nbsp;</i></div> </font> </td></tr></table> </td></tr></table> <div class="box" style="text-align: left; background-color: #FCFEFF; margin: 10px;"> <font color="#C22222"> Q: how can robots help us deal better with hurricanes and why? [Ontario, California] </font><p> A: [Aaron] Few people in Nebraska are threatened by hurricanes, so send a swarm of killer robots into low Atlantic and gulf coastal areas to drive the puny human inhabitants toward Nebraska. Problem solved. <p> <i>Robot haiku:</i> <table class=haiku><tr><td> That's obviously<br> A question from your homework.<br> Do your own research. </td></tr></table> </div> <p> <center> <span class="stack"><nobr><a class="span" href="AskAaron/greatest.html">Aaron's Greatest Hits!</a></nobr></span> <span class="stack"><nobr><a class="span" href="aaron_poems.pdf">More of Aaron's Poems</a></nobr></span> <span class="stack"><nobr><a class="span" href="https://www.youtube.com/watch?v=fEb-JnjCUUo">Aaron's Minecraft High Dive Video</a></nobr></span> <span class="stack"><nobr><a class="span" href="wowguide/wowguide.html">Aaron's World of Warcraft New Player Guide</a></nobr></span> </center> <p> <REM =================== Question ===================> <a name="question"></a> <hr style="border: 3px solid #55a; color: #ffffce; background-color: #ffffce; height: 7px; margin: 15px 0 25px 0;"><p> <p> <table><tr><td width=17% valign=top> <img src="pic2/questions2.gif" width=100% border=0 style="margin: -5px 0 0 0;" title="It's a mystery!"> </td><td> <font color="#444444">We welcome combat robot questions. Please search the <A href="AskAaron/FAQ.html">Ask Aaron Archives</a> first to see if we've already answered your question. Recent Q&A are posted above. Type your question in the box, attach file if needed, then click: 'Send'</font> <p><center> <form method="POST" enctype="multipart/form-data" action="http://plus.allforms.mailjol.net/u/1bab68b1.php"> <textarea name="Question"></textarea> <p> Attachment (optional): <input type="file" name="attachment" size="25" style="background-color: #FFC; color: #00F;"> <input type="submit" value="Send" name="submit" style="background-color: #44A; color: #FFF; font-weight: bold; margin: 10px 5px 0 10px;"> or <a href="javascript: void(0)" onclick="window.open('cheerleader.html','CheerWin', 'toolbar=no,top=110,left=70,width=700,height=370,menubar=no,resizable=yes'); return false;"> <input type="button" value="Cheerleader" name="cheerleader" style="background-color: #A02; color: #FFF; font-weight: bold; margin: 10px 0 0 5px;"> </a> </center> </form> <br> <center><a href="AskAaron/team.html#cheer">Why is there a '<font color="#AA0022">Cheerleader</font>' button?</a></center> </td></tr></table> <hr style="border: 3px solid #55a; color: #ffffce; background-color: #ffffce; height: 7px; margin: 15px 0 5px 0;"><br> <center><font color="#D22222"><b> Thousands more robot combat questions and answers in the searchable Ask Aaron archives.</b></font> <p> <!-- Google CSE Search Box Begins --> <form action="http://www.google.com/cse" id="searchbox_000217970424490523997:sufgum6k5ic"> <input type="hidden" name="cx" value="000217970424490523997:sufgum6k5ic" /> <input type="text" name="q" size="30" /> <input type="submit" name="sa" value="Search the Archives" /> </form> <!-- Google CSE Search Box Ends --> <p><HR class="dark"><br> <A name="MAP"></A> <table width=90%><tr><td><center> <A href="robotica.html"><img src="RAHome.gif" border=0 title="Run Amok Combat Robotics homepage"></A> <br><font size=-1><b>Copyright 2009, 2018 by Mark&nbsp;Joerger<br>All rights reserved. </b></font></center></td> <td> <rem whointheworld></td></tr></table> <font color="#FFFFCE">how to design and build a battlebot</font> <!-- Start of StatCounter Code --> <script type="text/javascript" language="javascript"> var sc_project=243145; </script> <script type="text/javascript" language="javascript" src="http://www.statcounter.com/counter/counter.js"></script><noscript><a href="http://www.statcounter.com" target="_blank"><img src="http://c1.statcounter.com/counter.php?sc_project=243145&amp;java=0" alt="counter" border="0"></a> </noscript> <!-- End of StatCounter Code --> <hr color="#ffffce" size=600> </td></tr></table> </BODY> </HTML>