pic: Octocanum Module

[wmarshall11]

Going from one 4x2 to two 2.5x1.25 Colsons would save 0.4lbs per module on wheels. Probably a little over a half pound per module with resulting gearing changes.

[wilsonmw04]

why articulate the motors? It would seem simpler to just move the wheels and leave the motors stationary.

[GeeTwo]

Originally Posted by wilsonmw04

why articulate the motors? It would seem simpler to just move the wheels and leave the motors stationary.

To do that, you'd have to drive the articulated wheel from the pivot wheel. This would mean either adding belt/chain or an intermediate gear that would engage both the gear on both wheels. To keep the speed ratio spread, you might need three such gears.

Since the force to articulate the wheels has to be sufficient to lift the robot, the extra amount necessary to move the motors is insignificant.

[Nathan Streeter]

Very innovative design; I don't think I've ever seen something similar!

The design seems generally very good. Obviously you have a pretty high weight per module, but it's not bad at all considering you have a mecanum, 2" wide colson, all your gearing, and a CIM and MiniCIM. You could easily drop MiniCIMs on the front or something like that to save an easy ~5 pounds on the robot. I'd say to keep the 2" colson... if you're bothering to have a high-torque traction mode, I'd say don't skimp on it. Now, a fair question could be, "how much do you really need the traction mode?" I think many teams (my own included) tend to want to add all the 'bells and whistles' without really doing the strategic game analysis.

My one comment about the integrity of the design is about the idler axle. I've never used a single bearing on an axle like that... does anyone else have some experience with an idler shaft with gears on each side supported by only one bearing? You could always put a .875" press fit on the back side so you could put a turned down shaft through through the module if you need more support. Seems like 3/8" aluminum would be more than enough for that.

EDIT: I'm guessing you're fully aware, but your mecanum mode is geared pretty high. It may end up working well for you (particularly in some games), but I'd honestly only gear a >110lb robot that high in 2011 and 2014 of the games since 2005 (although I think fair cases could be made for 2006 and 2008). I realize a fair bit of this is a 'strategy/design style' though. :-)

[cad321]

Originally Posted by Nathan Streeter

My one comment about the integrity of the design is about the idler axle. I've never used a single bearing on an axle like that... does anyone else have some experience with an idler shaft with gears on each side supported by only one bearing?

I only just noticed this after you pointed it out. I too am interested on what people think about this. On one hand there are so many constraints on the shaft from the meshing gears that it may be alright. On the other hand though, the amount of play in a single bearing (put a shaft through 1 bearing and try to wiggle it up and down) is quite significant.

[fargus111111111]

As far as the idler is concerned, I think it would work but would be quite loud due to almost constant minor imperfections in the meshing.

[Electronica1]

Originally Posted by wmarshall11

Going from one 4x2 to two 2.5x1.25 Colsons would save 0.4lbs per module on wheels. Probably a little over a half pound per module with resulting gearing changes.

Plus, the module itself gets smaller.