Insect Bots for Newbies

 

©Kevin M. Berry

Legendary Robotics, 2004

legendaryrobotics@gmail.com

 

 

Introduction

 Welcome to the world of combat robotics! Bots in this sport range from behemoths weighing almost 400 pounds, down to “insect” classes weighing only 5 ounces.   Most people are introduced to combat robots through TV shows, where a “small” bot weighs 60 pounds. But, it turns out that starting in the smaller classes makes sense, both from a cost, time and safety standpoint.

 For this article, three classes of bots are included:  150 gm (5.3 oz), 1 lb, and 3 lb.  The terms “Ant” (1 lb) and “Beetle” (3 lb, sometimes 2) are fairly universal. Nicknames for the smallest class are a matter of some debate, but the term “fairyweight” is often applied. Another is “U.K. Ant”. Since the author thinks a more insect oriented name is in order, we will call them “skeeterweights” here.

 

Legal Stuff:  Most people are familiar with the popular television show Battlebots.  This is a trademarked and copyrighted label, so for this article the more general term “combat robotics” is used. The one exception is in naming a specific item, the Battlebot toys, a commercially available product. All other product, internet site, and team names are the property of the owners and are published here as unpaid advertising in recognition of their great service to the robot combat community.

 

 

 

 

 Legendary Robotics fighting at The Capital Offense, July 2003.

Photo courtesy of Dales Homemade Robots.

 

 

 

Safety

 Combat robotics is a sport of hobbyists. Like many sports, a core group of “semi-pro’s” is surrounded by an enthusiastic community of general participants. Unlike many hobbies, safety is first priority in almost everyone’s mind. The items described in this article, even though used on the smallest of bots, can (and will) shock, cut, burn, bruise, impale, irritate, and probably poison a soft, squishy human body.

 Because of the community safety focus, virtually no injuries result during the actual battles. However, every builder winds up getting hurt, in shop and pit related accidents.  Power and hand tool safety is a well understood, and poorly practiced, art. Make it your goal to be the first builder to make it to, and through, a competition without as much as a scratch.

 Cost

 Combat robots can cost as much as any other professional sports machine. Numbers like $10,000 or $20,000 are fairly commonly bandied about for the larger bots. One reason many people get into the insect class is their lower cost.  A basic, competitive antweight bot can cost as little as $200, including some “support items”, and an extremely high end beetle can be built for under $500.

  Regardless of size, whether a bot is a 320 pound Super Heavyweight, or a 1 pound Antweight, all bots have the same 5 basic components. These are combined, organized, and named in myriad ways, called by trade names, acronyms, and function, but bottom line; they’re all the same building blocks. Figure 1 is just an introduction; each part will be explained in detail later.

 

 

Figure 1 – Basic Bot Building Blocks

(Alliteration intentional – Most bot builders have a GREAT sense of humor)

 Builders

 This sport draws, in this author’s opinion, one of the finest communities of people. They are fiercely competitive yet committed to the highest levels of sportsmanship. Stories abound of vicious battles in the box, where one bot is completely shredded. Entering the box afterwards, builders will cut pieces out to loan to the other team, either to resurrect their shredded bot, or to allow the victor better chances in their next fight.  Total strangers will stay up all night helping someone else’s machine for the next day’s fight. If you are not prepared to be highly professional and completely selfless out of the box, and committed to winning during fights, this may not be the sport for you.  Age is not a factor. At the recent Battle Beach Lite event, the author watched an 8 year old, twenty fight veteran battle a 50 year old newbie in an intense driving match.

 Communications

 Delphi Forums provides numerous message boards and chat rooms devoted to combat robotics.  In those forums, builders tend to be informally grouped into levels of competence: Newbie, Apprentice, Fully Capable, Pro’s, and Legends (authors classifications, your mileage may vary). In conversations and on the forums, Newbies should be humble and polite, also having done extensive research. In exchange for that, the community culture is such that a self proclaimed, humble Newbie should be “flameproof” and given much tolerance.  Cocky, boastful, or massively ignorant Newbies get roasted Well Done pretty quickly.

 Forum Examples:

 Good:  “I’m a new builder on my first bot. I’ve read the forums for 2 months, hit all the builder sites, and still have an ignorant question. I’m confused as to whether to use Copals or Escaps in my antweight bot”.  This person will get tons of help, including offers to meet in person and share hardware, tools, and data.

 Bad:  “I’m building a bot an its going to kill everyone and when it done i will fite it i wont stop until your all dead where you ly. how do i find a bot to buy and where do i fight it.”    This person will not last in the sport.  (By the way, this is NOT a totally fictitious example. This type of thing is also not limited to unsupervised 12 year olds, but believe it or not, some supposed adults come across this way!)

 Combat Robotics is still at the stage where the televised pro’s will help new builders, fully competent teams publish their designs for others to critique, and everyone is usually very helpful. The few jerks are easily recognized and tend to be policed by the others.

 

Types of bots

 These small bots fall into three general categories: R/C toy hacks, Servo based, and Discreet components.

 

R/C Toy Hacks

 The most basic hack, done by the author for the March 2003 Battle at the Beach, is quick, simple, cheap and fairly ineffective. Take the plastic body off an R/C car, cover the chassis with armor, (in this case a baking pan), and fight it!  These have a large turning radius, and are greatly underpowered.  Very few of this type of bot wins, but getting in the box, pits, and around other builders is a huge first step, so it may be worth the quick loss.

 

The original Fir Darrig (beetle, left) and Chupa Jr. (ant, right) at Battle Beach 1. These were unmodified R/C cars under baking pans. A good paint job helps a lot! While both were underpowered and hard to steer, we managed to win one fight with Fir Darrig.

Photo courtesy of Redneck Robots.

 

 

 

What I term a “second level hack” is using the radio/controller board to drive discreet motors, either directly or via an H-bridge. This avoids the investment in a professional radio and speed controller, but is of the on/off (no throttle) nature, and comes with the problems of interference noted above. There have been some spectacularly effective bots built this way, defying the term “hack.”

 

The second version of beetle Fir Darrig used the back ends of two R/C cars, the receiver/controller board from one car, and a separate battery pack. Fought at High Springs Ant Challenge 1 in April, 2003, it came in 3rd place (of 4 bots) with a 2-3 record.

 Photo by author.

 

 

 

 

 

 

 

 

 A very effective hack is converting a Battlebots toy. Many winning bots have been produced this way. The electronics, motors, and gearbox are used to provide a fairly powerful drive system.

 Used R/C cars, trucks, and Battlebot toys can be bought on line for a very modest price (often under $20). This is by far the least expensive way to get into combat robotics.  Robotdojo has a great lesson on how to hack a Battlebots toy.

 


Figure 2 – R/C Toy Car Hack

 

Servo Based

While there are many kinds of servos in the world, for this sport a servo is an R/C hobby item, usually used in model airplanes or boats to move a rudder, for ailerons, etc. They plug straight into a receiver, and contain a motor, gears, and electronics. They are usually fairly slow and very powerful. They also usually only have a 180 degree (or less) range of motion.

 A fairly simple hack is to remove the nub that restricts the range of motion so they act like a tiny motor and gearbox.  There are several ways to do this, best to search the internet or get advice from a veteran builder.

 These are good “starter” ants and skeeters. They make great pushbots, but can be a little boring to fight in today’s larger arenas. Still, if a person wants to get into the sport with a medium level of expense, this is a good way to start.

 The servos come with standard connectors that plug into the receiver. Battery packs can be bought with the same connectors. This makes the electronics “plug and play”, so only mechanical tasks remain to have a fully functional bot.

Example parts list and prices (new parts, low to middle tech)

 

  • 2 servos    $30
  • Receiver/transmitter $80  (often R/C radio sets come with servos)
  • Wheels   $5
  • NiMH battery pack   $20
  • Charger    $50

 Total, including a charger and transmitter you can use for all your bots: $185

A more realistic, and typical price would be in the $200-300 range, but that can also be offset by buying used items from local hobby clubs, stores, or via the internet (cough cough eBay). I built a bot on the cheap as follows, with used parts from other teams:

 

  • 2 servos, part of a buy of 4, $8
  • JR FM Receiver, 7 channels (overkill but cheap) $20
  • Homemade NiMH battery pack, 1/3 AAA, samples from internet site: $8 including shipping
  • 2 foam wheels, scrounged from another bot:  free, but call it 2 bucks
  • Transmitter and charger – existing
  • Aluminum, tape, Velcro and wire ties - existing

 Total: $38 bucks.  A hundred would be more reasonable to expect.  There are lots of places to buy servos, including Servo City.

 
Figure 3 – Servo Based Bot

 

 Discrete Components

 This is the way that high end combat bots are built. There are a confusing array of parts out there, but here we are going to try to give you a head start on understanding this end of the business.  A typical parts list, with prices, follows. Explanations of the function of each part are in the next section.

 Example parts list and prices (new parts, middle tech)

 

  • 2 Escap or Copal gearmotors $60
  • Receiver & transmitter $200
  • Wheels   $10
  • Hubs $10
  • NiMH battery pack   $30
  • Charger    $50
  • Electronic Speed Controller $80
  • Weapon motor, or actuator  $40
  • Metal $20
  • Servo Leads $10

 

Total, including a transmitter and charger you can use for all your bots: $500.  If you want to use pneumatic instead of electric weapons, you can expect to add up to a hundred dollars more.

 Here is a real price list for a wedge (non-weaponed) antweight bot I built with existing items plus parts I bought used or discounted

 

  • 2 new Copal gearmotors (aggressive favor trading via internet) $30
  • Used Receiver (forum friend) $20
  • Airplane Propeller Adapters (hubs) (new, Chinese hobby site, 2 weeks shipping time) $5
  • Homemade 2/3AAA NiMH battery pack, made from loose cells (aggressive internet shopping) $12
  • Sozbots Speed Controller (brand new from forum friend’s stockpile, older model) $40
  • Servo leads (less cost of 40 mile round trip to save $5)  $5
  • Wheels, Dave Brown Lite Flite (box on workbench)
  • Transmitter (same one from other bots)
  • Sheet metal & aluminum (box under workbench)

 Total out of pocket  $112.

 

Fir Darrig’s next upgrade was to discreet, professional components. This bot went on to take 2nd place at the SouthEast Ant and Beetle Championships held in November 2003. Note the wooden motor mounts – can’t shake the woodworking habit!

Photo courtesy of Dale’s Homemade Robots

 

 

Figure 4 – Discrete Component Bot

 

Another shot of Fir Darrig, now reconfigured with aluminum motor mounts and bottom armor. This version won 1st place at Battle Beach 2 in February 2004. (One wheel is noticeably cleaner due to slipping from a loose set screw. Minor mechanical problems like this caused it to lose 2 key fights at Battle Beach Lite, resulting in a 3rd place finish.)  Photo courtesy of Team Logicom and Battle Beach LLC.

 

 

Components

 

Batteries come in every type, from dollar store alkalines to specialty lithium-polymer cells. Often they are assembled into “ant packs” of various voltages and capacities by vendors or builders.  Selection of the proper battery may require help. Size, capacity, discharge rate, and voltage stability all play into selection. 

 The most popular small bot batteries are NiMH rechargeable. These can be purchased on eBay or from on line stores, as well as in pre-made packs from vendors specific to the sport, like Battlepacks. Li-Poly batteries, which are more expensive, also contain much more capacity. Most pro’s carry just enough capacity to fight one or two times before recharging or changing packs.  An insect bot might need as little as 150 milli-amp hours (mah) of capacity for a 3 minute fight, while it might need as much as a full amp-hour, usually referred to as 1000 mah.  Chargers range from a few dollars for one that slow charges individual cells, to $50 for a mid range charger that will do 8-12 cells at once in a pack, up to several hundred for a top end system.

Packs are often referred to by the number of cells. Each cell (contrary to what off the shelf cells claim) will output at 1.2 volts. The difference between a Nicad dollar store battery and a top end NiMH cell is that the latter will hold at 1.2 volts over the whole discharge period. The disposable cells “sag”, meaning voltage goes down when current is pulled. This really messes up the electronics of a bot, usually turning it into a twitching, useless, expensive target.   So a “5 cell pack” outputs 6 volts, an 8 cell pack outputs 9.6 volts, and a 12 cell pack 14.4 volts.

 Radio/receiver sets for R/C fall into several categories:

  • R/C Toys – Radio Shack remote control cars, Battlebot toys, and other toys are “hacked” to use the AM radio components. These transmit “broadband” signals at 27 or 49 Mhz, and are allowed at most tournaments for insect class bots only. Battlebots toys have some channel selection capability. The lack of specific channels can cause interference problems, so the inexpensive cost trades against this risk. Usually these radios have only 2 channels, one for throttle and one for steering, or else “tank driving” with two channels.
  • “Professional” AM – used for the more sophisticated R/C cars and trucks, this 27 Mhz radio system uses crystals to provide specific channels. Also allowed (usually) at tourneys for small bots only. These may have several channels, and some have more sophisticated adjustment capability.
  • FM – includes a couple of schemes, “PPM” and “PCM”. Suffice to say that these are “general builders” class radios, usable on all sizes of bots. FCC regulations are that ground machines (including combat bots) use 75 Mhz, while model airplanes use 72 Mhz.  Channels range from 3 to 8, and may be “hard wired” or programmable in nature.  Because technology is developed in a commercial environment, not all brands of radios are compatible with all receivers. In general, you are safer having the same brand of transmitter and receiver, (but there are more exceptions than can be listed here.)  Some popular brands are JR, Futaba, Airtronics and Hitech. FM systems, as well as the AM ones mentioned above, are available from stores like Tower Hobbies and Horizon Hobby.
  • IFI Robotics (Innovation First, Inc): A proprietary, computer controlled, 900 Mhz technology that is used by many “Pro level” builders, as well as the Battlebots IQ student competitions. 

 Speed controllers are circuits used to control the motors. The take the signal from the radio receiver, translate it, and use it to vary the current to the motors. On R/C toy cars, they are usually part of the same board as the receiver, and provide “forward/stop/backward” current to the motor, and “left/right” current to the steering. This is done using something called “H Bridge” technology, which is basically an on/off switch.

 On more sophisticated bots, a separate speed controller board is used. There are several manufacturers, but they all work somewhat the same. Bots are steered in one of two ways.  “Tank style” steering uses 2 joysticks, with each controlling one side of the bot. “Mixed” steering uses a single joystick to drive the bot in any direction.  Either way, 2 channels are used. To further complicate the story, mixing may be done in the radio, via a separate board, or in the speed controller. All but the most basic controllers provide throttle (speed) control as well as direction. There are several brands of ESC’s specifically designed for small combat robots, including Sozbots, Barello, and Microbotparts. 

 Motors come in many sizes and shapes. They range from the ones inside R/C toys, to specialty motors “imported” from other commercial fields, to hacked electric screwdrivers. A couple of terms you will hear are “neutrally timed” (same speed forward and backwards), and “turns” (R/C hobby motors may be “10 turn” for example. This has to do with the number of windings, and the power/speed tradeoff). Besides Sozbots, two very popular vendors for motors (and practically everything else) are RobotCombat and Lynxmotion.

 Transmission of power is done in several ways. Many motors come integrated with gearboxes at a set ratio. Other gearboxes can be configured by the user (think of a Chinese puzzle with a zillion pieces). Also, belts and pulleys, or gears and chains are used. <<Photo of motor/gearbox combo>>

 Wheels and hubs are much less specialized than other components. Dave Brown Lite Flite airplane wheels are common, as are products from Lynxmotion, but everything from pulleys with rubber o-rings, to model car wheels, to custom made wheels are used.

 Weapons are the first thing a person thinks of when the topic of combat robotics comes up. However, it is widely recognized by experienced builders that it is a mistake to attempt active weapons on a starter bot. Rarely does a newbie produce a competitive weapon, Just getting a bot to run, steer, and survive is a huge challenge.  Most, if not all, builders mentoring new participants recommend a simple pushy or wedge bot as the first project. If you simply must try a weapon, many teams use Team Delta switches to control them.

 Finding An Event And Competing

Internet searches will reveal a number of team, regional organization, and event sites. Every region of the U.S. has an organization eager to welcome new members. SouthEast Combat Robotics, NorthEast Robot Combat, SouthWestern Alliance of Robot Combat, Western Allied Robotics, and Mid US Robotics Club are some of the regional groups.  The Robot Fighting League, an alliance of Event Organizers, umbrellas many events. An invaluable resource is the Builders Database, a commonly used event registration system.

 Rule sets vary, but tend to be similar in content. They seem overwhelming at first, but as you build your bot, you will find they contain necessary safety restrictions to protect builders and spectators.

 No matter how much planning, internet browsing, and chatting an interested new builder does, there is no substitute for going to an event. Whether you build an R/C toy hack and participate, or attend to learn, you will find everyone eager to offer advice, help, and invitations to discuss combat robot building and fighting.

 About the author: Kevin Berry, of Legendary Robotics, is, in no particular order, a husband, a father, a Christian, a builder of 17 combat robots (ranging from spectacularly poor to pretty good), a Rocket Bureaucrat, a free lance writer with over 100 published articles and columns, a creativity coach, a project management consultant, a home improvement hack, a youth leader, and in no particular order. Kevin, his wife, their 4 children, and an ancient Chihuahua live in Titusville, Florida.

 This article is available for purchase. One time U.S. publication, International publication rights, bulk sales, for either electronic or print rights available.

 

 Links

 WWW.battlebots.com

www.delphi.com

www.robotdojo.com

www.servocity.com

www.battlepacks.com

www.towerhobbies.com

www.horizonhobby.com

www.ifirobotics.com

www.sozbots.com

www.barello.net

www.microbotparts.com

www.robotcombat.com

www.lynxmotion.com

www.teamdelta.com

www.secr.org

www.nerc.us

www.swarc.org

www.westernalliedrobotics.com

www.murconline.com

www.botleague.com

www.buildersdb.com

Last Updated Saturday, 27-Feb-2010 09:35:37 MST Copyright 2002, 2005, 2006 Battle Beach, LLC
Web site production by Team Moon Robotics