This is our practice chassis that we finished last night. Check out http://www.youtube.com/watch?v=CGZBtZbZ714 to see it in action.
Looks awesome! The modules look very robust and pretty. Some plating on that thing would make it look like a beast.
I have some questions though. Did you notice any flex in the frame when driving? It looks to me like it is all bolted together. I know people have had problems with frame flex in mecanum drive trains. One of the wheels would lift off the ground, messing up the resultant total force vector, sending the robot in another unforeseen direction.
I beleive that they have a suspension (similar to 40’s) on each wheel module to attempt and accomodate for any bending, imprecision, or minor terrain features.
Certainly a great looking protoype, how much does it weigh?
Check out http://www.chiefdelphi.com/forums/showthread.php?t=49213 for a better description.
Each wheel/gearbox pod pivots. The tennis and racket balls are what we are testing out for suspension springs. Right now, we are having more of an issue making the friction in the drive pods equal (we had one really beat up CIM in this chassis). If one wheel takes a second longer to start spinning then the same issue occurs.
Overall though our drivers were starting to be able to compensate for the quirks in the movement, so when we get it nice and tuned it should only get better 
Looks very nice.
How well does it handle stairs? 
-dave
It’s too much fun to drive and a lot of fun to watch. If it needs to climb stairs, I’ll make it climb stairs.
Lavery as in this years game is going to have stairs!? Just playing, thats a really nice frame and set up.
Beautiful moves! I can’t wait to see what the drivers can do with some more practice. One question, any idea why it seems to be so noisy (in the video?) With your custom gearboxes I figured they would be nice and quiet. Or, are the AM Mecanums just that loud? (Sorry for the insinuation Andy/Mark…)
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Dave, it’s about that time of the year when the real hints start coming our way. Is this your first “plant” here at the forums for us to deal with?
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Please keep us update with both your mechanical tuning and software tweaking (and methodology, if you will…) Thanks!
BEN
The first gearbox we assembled is markedly louder than the remaining three and it’s also the one that’s slowest to start, so we’re going to tear it down and rebuild it. We think the first handful of shafts we made are inaccurate, so the gearbox isn’t square and that’s contributing to some binding. The chain is also a bit loose and I screwed up the tensioning mechanism some, so that’ll be fixed in the next iteration – whenever there’s time for that.
The wheels, even on carpet, are a bit bumpy because the roller profile only approximates an elliptical shape. More weight may sink the chassis deeper into the carpet and alleviate some of the uneven ride; but that’s also contributing to some of the noise you hear. Right now, sans battery, I’d say it weighs about 50 pounds. We’ll get an accurate measurement of that tomorrow, we hope.
Edit: There’s also no grease in the gears. We need to fix that, too.
HINT HINT OMG HINT!!!
lol something that could climb stairs hmmm
tears apart an iBot MINE CAN NOW
I’ll never get tired of watching one of these guys move. Excellent job getting to this point for sure. As for Dave and the stairs, just ignore him like the rest of the FRC GDC does… 
I was looking at the full-size version of the picture, and it looks like the actual frame is just four lengths of box tubing and two C-channels bolted together. I like the layout–is there more to it, or am I just not seeing it?
Could you please provide an up close picture of your suspension or explain it in a little more detail (I’m new to suspensions). Thanks a lot!
Nope, thats it! The underside of the C channel is milled out to accommodate the suspension, holes were drilled for where the drive pods rotate, and 8 holes were drilled to bolt the tube and C channel together.
How durable is that setup?
That appears to be the max size of a drive base according to last years rules, right? For a competition bot, would you scale that design down somewhat in order to add a protective structure around the outside? or would you just rely on the fabric bumpers? It would seem to me that the channel used on the outside would bend/dent easily, and no amount of suspension will keep a Mecanum drive operating correctly if one or two of the wheels are suddenly bent at some odd-angle. The video looks very nice indeed, and I can’t wait to see what the drivers can do with a bit of practice
It hasn’t broken yet 
The frame seems plenty rigid and sturdy. We have not really ran into anything yet, but with bumpers and such it should be fairly protected. How it deals with the strains of the rest of the weight of the robot we still have to evaluate.
The chassis is about an inch short of last year’s maximums in all directions. If you look at some of our past work, you’ll see that I don’t typically add structure to things for protection, but since these wheels are quite expensive, this chassis was kept simple to facilitate accepting bumpers. Also consider that it’s for practice and won’t be seeing competition, so there was no use in wasting time and resources on making it stronger than it needs to be for learning, practice and demonstrations.
I wanna see a Mecanum drive at Portland this year! I could spend hours looking over this robot in the pits.
alright, some things to try:
See what effect tightnening the rollers has compared to haveing them loose.
Drive up some ramps.
Drive up some stairs!
Oh, and did you incorperate the suspention system? I can’t tell from the picture.