Quote:
Originally Posted by Lil' Lavery
Simply put, my question is... why?
I can understand possibly adding a set of 3rd wheels in the middle between the mecanums for helping stability (assuming they're all coplanar), but 10-wheels is excessive.
More wheels doesn't equate to more traction (or more pushing power).
The most glaring flaw of all is that those big, heavy, expensive mecanum wheels are nothing but giant, efficiency (and "pushing power") robbing wheels in this drive system.
You have each side linked via chain, meaning each side of the drive train acts as one. In order to get strafing motion out of mecanum wheels, you need for each to be independently powered. In this configuration, each mecanum wheel is diverting some of your force in unused directions, costing you pushing power without giving you the maneuverability advantages.
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1.) More wheels can support more weight and still have omni-movement in a non-FRC application
2.) More wheels = more traction in a dynamic environment where actual amount of surface contact is unpredictable. Why? More wheels = higher probability that you will get a better mate of carpet and rubber at any given contact point. Tonight I'll try to find the link where some Japanese researchers showed this relationship when determining tread design for shoes that wouldn't slip when going up/down carpeted stairs. Essentially, the shorter the carpet and finer the threads the less this is an issue but it could explain the anecdotal evidence some teams claim they've seen.
3.) The ball differential in the middle allows for strafing as a normal mecanum would move.
4.) Why? Because he can. I think this is a spectacular representation of engineering outside the box in FRC. Pushing the boundaries of transportation systems has always been met with a 'why' or 'that's not needed', and I thoroughly enjoy seeing fresh ideas, regardless of whether or not it applies to this or previous years' games.
Though I agree, it's overkill for an actual FRC game where the conditions for every 'feature' aren't met. On the four additional omni wheel sets, the chassis may be able to get away with 1 omni instead of a pair of omnis in order to save weight. Additionally, I would recommend teflon-coating the bearings/sprockets/chains because even with 99% efficiency per wheel, 0.99^10 = 10% torque loss overall. Then take into account the fact that you can only put 1/sqrt(2) torque going in the 'forward' motion (i.e. ~70% of total torque, due to the 45 degree angle of the rollers) and it's easy to explain why this setup may not live up to pushing power and/or acceleration expectations.