pic: Spectrum Fall 2013 Drivetrain

[AllenGregoryIV]

Originally Posted by DampRobot

I'm a skeptic. Why should I like geared drivetrains?

At least in my mind, a timing belt drivetrain is both lighter and more efficient, and a chain drive is much easier to build and quicker to fix. I do see that chains and belts becoming de-tensioned is a disadvantage, but the solution to this is a cam or exact c-c system. Is there some specific advantage that gears offer over belts or chain that can't be attained in either system?

I can't tell you why you should like it but I can tell you what's attractive to us.

Off The Shelf Parts
Outside of the sheet metal which we get produced by our sponsor, every piece in this is off the shelf and can be assembled with little to no modification. Nothing requires a lathe or a mill. Seeing as we don't have access to either (yet), this is an important feature. It's currently near impossible to meet this requirement with belts.

Narrow
The new robot dimensions (assuming they stick around) make the standard kit bot way of doing chains seem really large, the kit bot or VEXpro drive in a day are good examples. For reference those are the types of drives we have used before. A WCD might be a bit thinner but we don't have milling and welding resources but we have a great laser cutter/sheet metal sponsor.

No tensioning or ever throwing belts/chains
A good drivetrain has a great tensioning system and never throws belts or chains. I am not confident enough that we can build a drivetrain that will meet those requirements. The gear drive solves that problem.

No need for access from the top of the box
We now have the entire width of the robot for our game playing elements. We can cover the entire top of the drive train and not worry about having to ever reach in a fix a chain or belt. We can replace wheels extremely quickly with just one bolt each. This also might be marginally safer as it is harder to get a finger or drop something in the drive.

Can change wheel configurations easily
10, 8, or 6 wheel configurations are all available with this robot without changing much of anything except removing a wheel or two. You could build the same thing into a chain/belt system but that would be a lot of tensioning.

It's a prototype
And the last reason is it's a prototype and it's different. In 3 months I might be completely on the other side of this issue and telling people to never build gear drivetrains ever. If that does end up being the case, we'll have with a nice stock of gears to use for future gearboxes and a story to tell.