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View Poll Results: How mecanum drive effects a teams position on your pick list
Automatic DNP 34 11.07%
Moved lower 84 27.36%
Depends on performance 161 52.44%
Nothing (does not effect position) 22 7.17%
Other (please explain in thread) 6 1.95%
Voters: 307. You may not vote on this poll

 
 
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Unread 21-08-2014, 21:22
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Sam_Mills Sam_Mills is offline
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Re: Penalizing mecanum wheeled robots durring alliance selection.

Quote:
Originally Posted by Rypsnort View Post
I have not personally been a part of selecting teams, but I have noticed that you have to have a strategy in your alliance that accommodates a mecanum drive bot. Mecanum is good for being evasive (if built and driven well) but is bad for being physical and getting in pushing matches. If you don't have a need for it don't pick it(mecanum drive).
Not to call you out specifically, but you mentioned something that is frequently spread around, and not quite true. Mecanum is often touted as being good for being evasive, but due to the fact it must be geared slower (for more torque) to strafe well, they typically can't outmaneuver a tank drive (this is especially true in the 6 CIM era). If you want an example of this, look to Ultimate Ascent;

There was a very small handful of robots able to complete 7 cycles, which was a task that required nearly no pushing, and all maneuverability. If mecanum wheels were more maneuverable, you would expect the best cyclers to be mecanum robots, but this was not the case. 118, 469, 610, 245, 868, 11, etc., were all tank drive robots.

Quote:
Originally Posted by SeanFitz View Post
I think it really comes down to how big your wheels are. In 2013 we bought big 8" diameter, 2" width wheels and were actually one of the better pushing robots out there (didn't get picked, but that was mainly because our shooter was awful). In contrast, we used 6" diameter, 1" width wheels in 2010 and got pushed all over the place.
"Pushing Power," is a function of coefficient of friction with the floor, robot weight, and torque. Wheels sizes (widths) can influence coefficient of friction, but tread material is typically a more important factor. Wheel diameter can also affect coefficient of friction by changing the size of the flat patch you have on the carpet, but this has a pretty minor effect. Torque is a function of your gear ratios and wheel diameter together, as well as the efficiency of your transmission, but you can gear for as much toque as you want, regardless of wheel size.

TL;DR: You can push with small wheels if you want to, just be aware of the variables at play.
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