Battle Hardening the Inside of Your Bot

Posted in Uncategorized by Near Chaos Robotics on April 12, 2015 No Comments yet

When most people are designing and building their bot they focus on the armor, weapon, and drive system. Making sure these are all in good order is important, but there is something that is often overlooked: The internal systems. A good number of knockouts at robot events aren’t due to catastrophic damage, but due to a single small failure at an inconvenient location. Many of these failures can be avoided by doing what is often referred to as “Battle Hardening”.

Cover Your Exposed Receiver Plugs

Small receiver wrapped with electrical tape.

Most 2.4ghz receivers use a bind plug to put the rx in bind mode. This is done by connecting the signal and negative leads of the Batt/Bind port on the rx. If your rx has exposed prongs for these ports it is possible for conductive material to contact these plugs during a match, putting your rx into bind mode. Your bot will stop moving and in all probability, and there are only two was to get the bot out of bind mode- power cycle the receiver, or bind to it. The first isn’t doable during a match and the second may well take longer than the 10 seconds you’ve got before you’re counted out. This can be avoided by wrapping the exposed prongs with electrical tape. It’s a quick, nearly weightless way to minimize the chances of this ending your match.

Wrap Your Connectors

Wrapping your plugs with tape absorbs shock.

Most common connector types (Deans, JST, Powerpole, etc…) feel like they plug in pretty securely, and really, they do. However, robot combat is a rough sport and there’s a good chance your bot will see some serious forces in the arena. These forces, when experienced at the proper angle and in the right order can be enough to unplug your connectors. A quick wrap of electrical tape is typically enough to absorb the initial shock of the impact and keep your connections together.

Restrain Your Wires

Restraining your wires will help ensure your robot doesn't eat its wires.

Another potential danger caused by the shock of combat (or just putting the top armor on your bot) is that the wires might find their way to a moving component. When this happens, there are a few potential results: You could have the thing its touching grind/rub away at the insulation until the bare wire is now in direct contact with your chassis, you could have it cut the wire, or you could end up with it grabbing hold of the wire and trying to pull it free of its connections, along with anything that’s tangled up with it. None of these are good, and taking a bit of time to tie down your wires now can save hours of rewiring at an event.

Tape or Shrink Wrap Your Exposed Connectors

A bit of well placed shrink wrap can prevent shorts.

This part is pretty simple, the less exposed metal that’s part of the electrical system of your robot, the better off you’ll be. Exposed connections mean you’re at risk of a short, and a short likely means you’ve burnt up something expensive.

Pad Your Batteries

A little foam can save a lot of problems.

Batteries are relatively fragile things, LiPo batteries to an even greater extent. You should take care to minimize the shock that gets transmitted to your batteries. Rigid mounting is a recipe for damaged cells or a battery fire. When dealing with LiPo batteries, one thing I’ve found that helps greatly with their longevity is to put them in a padded foam enclosure. This allows the packs to swell while under heavy draw without reaching any solid barriers and gives them the best chances of survival.

Use Loctite – Seriously, Use It!

If you’ve got bolts going somewhere that you never want to get out, use red Loctite. If you might want to get them out some time in the future, use blue Loctite. If you’re removing them after every fight to get to parts, you can probably skip the loctite, but make sure they’re nice and secure before each match.

Use Connectors On Parts You’ll Potentially Need to Replace

Just about every connection uses a polarized plug.

When doing the wiring for your bot, it may add a bit of cost and a tiny amount of weight to the system but it’s typically worth it to have each element of your system able to be removed and replaced without soldering. Use polarized (ie Deans) connectors wherever possible to minimize the risk of reversing the polarity on a critical system. Use bullet connectors on parts where you’d potentially need to reverse the polarity quickly. (Typically spare drive motors)

Have A Common Power Distribution Point

For both the positive and negative leads coming from the battery, have a single point where the power is transferred to the rest of the robot. Typically, the positive portion of this will be on the far side of the power switch from the battery. For the negative side I tend to prefer high current connectors bolted together and wrapped in tape. These distribution points should be placed as close to the battery connection as is practical in your robot as that will keep the peak current in most of the wires in your robot as low as possible. Lower current means less heat, and less heat means less risk of meltdown. It also means you can use smaller gauge wire throughout the rest of your system as it doesn’t need to handle as much power which can reduce weight.

Practice Soldering

There aren’t many ways to build a bot without soldering somewhere, which means you’ll want to ensure you’ve got strong solder connections. There are a few keys to strong solder connections: The correct solder, the correct iron, good solder flow, and keeping the iron/heat in place long enough that you’ve got the connection reasonably covered. There are plenty of opinions on what is “right” so I’ll leave it at what I use, which has proven to be good enough for bots ranging from 150g to 30lbs for quite a long time.

Solder: Solder with Rosin Flux Core
I bought a spool of this in 2010 and still have plenty left.

Soldering Iron: Weller W60P 60Watts/120V Controlled Output Soldering Iron
This iron with the widest tip I could find has worked very well for me. Weller CT5D8 tip

Getting good flow with flux: Lucky Bob’s Acid Flux
This stuff’s a bit nasty and you’ll want to make sure you burn it all off when you’re using it or else it may corrode your wire over time, but it’s part of the recipe for a strong connection. The process I use is: Brush acid flux on bare wire, coat tip of iron in rosin cored 60/40 solder, touch coated iron tip to wire on all sides.

Helping hands to avoid charring your fingers: Something like this
I tend to not use them, but these are a huge help while you build up a tolerance for hot wires.

Battle Hardening Small Motors

http://www.teamrollingthunder.com/Kitbots/Battle_Harden/body_battle_harden.html

Pete Smith wrote up a guide to battle hardening the Kitbots 1000rpm motors. These techniques can be applied to all similarly designed gearboxes with minimal modification.

Thanks for reading, if you’ve got questions or requests for future articles send me an email at MikeNCR@gmail.com or post it over here: http://sparc.tools/forum/index.php?topic=5.0

Combat Robot Building – Micro Bots

Posted in Uncategorized by Near Chaos Robotics on March 28, 2015 No Comments yet

This post is meant primarily to supplement the Combat Robot Building – Micro Bots class at Freeside Atlanta on March 28th, 2015.

The presentation can be downloaded at http://NearChaos.net/CRB-MB.rar or http://NearChaos.net/CRB-MB.zip

If you’ve got any additional questions, feel free to send them to MikeNCR@gmail.com or head over to the SPARC Forums.

During the class it was asked if there was a good book on robot combat. At the moment, the best “book” to go with is from Riobotz- Downloadable PDF, Physical Book

Unrequested Advice: Drive Better

Posted in Uncategorized by Near Chaos Robotics on March 15, 2015 No Comments yet

There’s been one constant in robot combat since the beginning. No matter how tough your machine, how destructive the weapon, or how sound your strategy you won’t be able to get the best out of it if you’re not able to drive it well. With that being said, here are a few things you can do to become a better driver:

    Target Practice

Just driving your bot around isn’t typically enough to get good at driving it in a combat environment. Sure, you’ll learn how to drive in a straight line and how to make turns, but what you won’t do is learn how to chase a moving, often erratic target.

If you’ve got someone who’s willing to drive a moving target (for example, a cheap RC car) then you’re all set. The target tries to keep away from your bot, you try to catch the target with your bot. If possible, find a way to set up a specific area to do this in to replicate the perimeter of most combat arenas.

A small test area built onto a pallet.

If you don’t have a willing target operator one thing I’ve found that is fantastic for small bots is a Weazel Ball.

Tailless Weazel Ball

It is advisable to remove the tail to avoid it becoming stuck in the rotating parts of your robot.

If you intend to do any of this drive testing with an active spinning weapon you should do it in a safe manner. For most bots, this means the creation of a test box. With a spinning weapon there’s no way to be certain of what will go where when you hit something. A test box is the best way to go about this, and if you’re willing to scrounge a bit it can be made fairly inexpensively. As robots get larger, it is more difficult to properly contain them in an enclosure that will also allow them to be driven in a manner similar to combat so for those systems I recommend doing weapon-off driving practice.

Small test box with a full lid to prevent flying debris from exiting the test area.

The more practice you can get in before an event the better off you’ll be. With enough time, you won’t be thinking about what your thumbs need to do during a match, but what the bot needs to do.

    Throttle Control

Unless you’re using relays for drive, you’ve got a lot of throttle range to play with. Most people seem to only drive with the edges of the travel range. They’re either up against the edge of the sticks throw or they’re not on the throttle at all. This makes for a bot that moves quickly, but often not in the intended direction. The benefits of proportionally (or exponentially) controlled drive systems is that you can opt to move as fast as possible or move more slowly but in a much more controlled manner.

Transmitter stick.

I like fast bots. Most of the bots I run at events are easily in the top 10-15% of the class when it comes to speed. If you watch my fights, though, you’ll often see my bots driving slower than the opponent for noticeable stretches of the match. Unless I’m lined up on the other bot or in contact with them, I’ll often be at 50% throttle or less while driving.

Why slow down? It’s simple, you don’t need to go fast to score points on aggression, you don’t need to go fast to get lined up for an attack, and you don’t need to go fast to take control of the fight. Speed is a useful tool, but it’s only part of the kit you’ll need to do well. If you charge full on at the other bot and miss, then you’re about to run weapon first into the wall or off the ledge or down the pit. Best case there is you’re now facing the wrong way and stopped. Worst case, you’ve already lost the fight. Speed is great, accuracy is better.

Take some time and acquaint yourself with the other 80% of what your drive system is capable of. It’ll pay off in the long run.

Video from Motorama 2015

Posted in Uncategorized by Near Chaos Robotics on February 25, 2015 No Comments yet

Playlists for Motorama 2015 are up:

http://sparc.tools/forum/index.php?topic=76.msg644#msg644

Instructable for Nyx v2

Posted in Uncategorized by Near Chaos Robotics on November 12, 2014 No Comments yet

The instructable for the new Nyx is live.

http://www.instructables.com/id/Nyx-30lb-Fighting-Robot-Re-Made/

Instructables Posts

Posted in Uncategorized by Near Chaos Robotics on November 8, 2014 No Comments yet

I’ve done Instructables on several of our robots, they can be found here: http://www.instructables.com/member/MikeNCR/

Keep an eye out for the upcoming Instructable on version 2 of Nyx.

If you want to skip the reading and go right to the CAD files, here’s all of the CAD files for Nyx v2: http://nearchaos.net/NyxCadFiles.rar

YouTube Playlists

Posted in Uncategorized by Near Chaos Robotics on November 8, 2014 No Comments yet

Playlists from a huge number of past events as well as testing video of our robots can be found at https://www.youtube.com/user/mikencr/playlists?sort=dd&view=1

Chaos Hubs

Posted in Uncategorized by Near Chaos Robotics on November 8, 2014 No Comments yet

Chaos Hubs are available now. To order, send an email to MikeNCR@gmail.com with sizes and quantities.

Assembled3inch

HubPile

After seeing a complete lack of decent Colson hubs on the market for a 1/2″ keyed shaft I made my own.

The initial run of these was fairly small, however if they’re popular I’ll be stocking larger quantities in the near future.

General Specs:
Press fit for 1-3/16″ bore
Intended for 1-1/2″ wide Colson caster wheels, able to be adapted to 2″ Colson caster wheels that have the same bore.
Overall Width: 1-3/4″ including 1/8″ flange
Material: Delrin
Bore: 1/2″ with 1/8″ keyway
Includes slot for 1/4″ key on OD. For purchased wheel assemblies the Colson wheel will be broached and installed with a 1″ long key.

Bare Hubs: $10
1-1/2″ wide wheels
3″: $20.50
4″: $20.00
5″: $20.00
6″: $21.00
8″: $26.50

Current stock sits at 110 hubs, (10 in black, 100 in white) 4x 6″ Colsons and 6x 4″ Colsons.

Review By Pete Smith published in Servo Magazine:

“The 1.5″ and 2″ wide Colson wheels have been popular in the 30 lb+ weight classes in combat robotics for many years, but builders often had to make their own hubs to mate the large bore of the Colsons with the standard 1/2″ keyed shafts that come on drive gearmotors like Banebots P60s.
Near Chaos Robotics has filled that gap in the market with their new “Chaos Hubs.”
Machined from Delrin — a tough but light plastic — the hubs have keyways to lock the hub to the shaft and to the wheel.
A shaft clamp (not included) could be used to keep the hub and wheel from sliding off the shaft.
The basic hub weighs only 1.5 oz (44 g) including the key, and are a perfect fit with the 1.5″ wide Colsons. They can also be used with the 2″ wide wheels. A complete 4″ x 1.5” wheel assembly weighs only 9.2 oz (262 g).”

Starting fresh after DB issues

Posted in Uncategorized by Near Chaos Robotics on November 8, 2014 No Comments yet

Some issues have resulted in the majority of posts being lost, so I’ll be restoring the more important posts over the next few days.