Bots for Newbies
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.
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.
Robotics fighting at The Capital Offense, July 2003.
courtesy of Dales Homemade Robots.
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.
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.
1 – Basic Bot Building Blocks
intentional – Most bot builders have a GREAT sense of humor)
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.
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.
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.
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.
These small bots fall into three general categories: R/C toy hacks,
Servo based, and Discreet components.
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.
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.
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.”
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.
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
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.
2 – R/C Toy Car Hack
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)
$80 (often R/C radio sets come with servos)
- Wheels $5
battery pack $20
- Charger $50
Total, including a charger and transmitter you can use for all your
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:
servos, part of a buy of 4, $8
FM Receiver, 7 channels (overkill but cheap) $20
NiMH battery pack, 1/3 AAA, samples from internet site: $8 including shipping
foam wheels, scrounged from another bot: free, but call it 2 bucks
and charger – existing
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
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)
Escap or Copal gearmotors $60
- Receiver & transmitter
- Wheels $10
battery pack $30
- Charger $50
Speed Controller $80
motor, or actuator $40
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
new Copal gearmotors (aggressive favor trading via internet) $30
Receiver (forum friend) $20
Propeller Adapters (hubs) (new, Chinese hobby site, 2 weeks shipping time) $5
2/3AAA NiMH battery pack, made from loose cells (aggressive internet shopping) $12
Speed Controller (brand new from forum friend’s stockpile, older model) $40
leads (less cost of 40 mile round trip to save $5) $5
Dave Brown Lite Flite (box on workbench)
(same one from other bots)
metal & aluminum (box under workbench)
Total out of pocket $112.
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
courtesy of Dale’s Homemade Robots
4 – Discrete Component Bot
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.
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:
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.
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.
– 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.
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>>
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.
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
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
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.
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