Servo - November 2009

mounts on the gearboxes.

The design of these mounts will vary. If the builder is using the latter method, then the design itself can be as simple as a metal plate. This piece would connect to both the gearbox and the frame so that it can be easily removed, but conversely remain firmly attached. If the builder uses the first method mentioned, the design is slightly more complicated. In this case, if the builder requires the motors to be encapsulated rather than just dangling from the gearboxes, the simple plate design will have to be expanded based off the reason.

First, the builder may need to protect the motors or the surrounding components from vibration or buckling. In this case, the plate design would only need to be modified by extending the piece, such that it continues under the motors. If the plate, however, is not placed on the base of the gearbox but on its face, then it would only need to be modified with a second larger piece on the base of the gearbox. Or, use one piece with a right angle bend in it. In both cases, the extended plate under the motors would provide more mounting holes on the base of the frame, as well as the base to mount pieces to both absorb vibration from the motors and protect them from buckling out of place.

A second reason for a builder to opt for a more complicated mount might be for adding more armor around the gearboxes and motors. In this case, the plate design would need to be modified by adding separate plates or framing around the motors and gearboxes in order to mount the needed armor.

One last method I have seen used in modular drive trains is what is usually called drive pods. If you have ever looked at combot kits, you have probably seen them before. The basic idea is to take the motor and gearbox assembly and then attach it to the driven wheel and reduction area of the bot. As

one unit, you would only need two of these assemblies and you would have almost your entire drive system done. Your chassis will get less complicated, as it will simply become a box to hold everything else in.

Setting Up

The Electronics

As opposed to the drive system, a modular electronics system is far easier to set up in your bot. The first thing to consider is exactly where you will need to place the wiring, and most of your work is finished. Quick release connections are important since you will want to be able to take out and put back this module quickly, without destroying your wiring. The module itself is meant to contain the electronic components, such as your speed controllers and the programming board. A simple way to do this is to mill out slots in material such as UHMW that fit the dimensions of those components and screw these pieces directly into the material. From there, make sure you have milled out the proper channels for the wiring you need and make the material deep enough. Then, put one cover over the entire module, thereby covering your components, and you are finished. If you are already protecting the components by your combat armor, it might be nice to use clear Lexan as a cover in order to be able to quickly see inside without having to take off the cover each time.

The Weapon System

A modular weapon system can be easier or harder than the other two assemblies, depending on the type of bot you are building and what kind of changes you want to be able to make. Beginning with the easier end of the spectrum, thwack and wedge bots are the simplest to modify. If you are staying within these two confines, it’s simple to modify a variety of wedge ramps

and thwack weapons to switch in and out, depending on the opponent. Also, if you are planning to switch between those types, with simple planning it should be easy enough to turn your wedge into a good thwack bot, and vice versa.

More difficulty comes when you are working with spinner types, such as shell and drum bots. It wouldn’t be too hard to switch a spinning blade for a spinning shell as long as you design your chassis accordingly, but to switch out a spinning bar for something like a drum would be difficult. That would require not only having the proper mounts in place ahead of time, but weapon and motor assemblies that can be pulled out and changed in terms of orientation. One example I have seen was a team switching from a drum to a wedge after the team’s drum was destroyed. That is a good precaution, but one that requires specific circumstances.

That’s A Wrap!

A modular combot has a lot of benefits, but like all things, only if done properly. I hope this article helps you the next time you are thinking about the versatility of your robot. SV