Mecanum wheel wobble (not runout)

[DougJensen]

Hey folks - We seek advice on mecanum wheel wobble/precess (not runout). Our brand new set of 8" AM wheels produces about 1/8" left/right wobble at the wheel radius when assembled using the supplied internal spacer and a 550 plastic spacer/sprocket.

Not having prior experience with this drive, I'm not sure if this is a problem, but it seems odd to have so much - and this wobble translates into a sprocket wobble (although about half as much at the sprocket radius) - that is way more than I'd accept on a standard linear wheel mounted sprocket.

We've had several MEs look at this and try the assembly process themselves, along with using a torque wrench to properly tighten the sprocket in a proper bolt cinching pattern. All result in the same amount of wobble/precession. Any help would be appreciated, but we do not have the luxury of moving away from a sprocket drive.
Thanks! Doug

[DavidGitz]

We have been using the 6" Mecanum wheels for a while and have not had any trouble. With the 8" wheels did you get the kit to assemble them yourselves? Pictures would be helpful.

Are you supporting both of the Mecanum plates? We are running dead-axle's so we have a 3/8" ID bearing on each side of the Mecanum along with a sprocket spacer and then a #35 22 tooth sprocket and they work great.

[pfreivald]

We've used them for several years, direct-driving off of p80 gearboxes using AM .5" keyed wheel hubs, and have never had a problem.

[ToddF]

We used the 6 inch wheels last year, and had similar issues. We got our order for wheels in just a little late, and the lightweight wheels were sold out. We bought a set of the heavy duty wheels while the lightweight ones were on backorder. We used the heavy ones for development with no problems, and swapped the lightweight ones in when they arrived. Since they had already done one set of wheels, I left our rookie kids to assemble and install the lightweight wheels when they arrived, with little supervision. When everything was installed, they were so wobbly they wouldn't turn without hitting neighboring support structure.

Fixing the wobble involved loosening screws, racking the wheels straight by hand, and retightening, and then doing that again and again until they stayed straight. It took hours, and we never got them to run perfectly true. They were straight enough to function, though.

My advise would be: if your support structure give you enough clearance, test them with the wobble. If they work, put fixing the wobble at the bottom of your list of priorities. Then, when someone doesn't have something to do, and is goofing around, assign that person to true up the wheels.

[petey6698]

We had a similar problem on our first build day. What we ended up doing is just cutting new sprockets for our wheels and replacing the old ones. after that the wobble was gone. hope this helped. Oh and why did a medical examiner look at your wheels?

[Chris_Ely]

Is the frame level? We had a similar problem with ours last year, which was easily corrected by leveling the frame. Also make sure that the wheels are at the same height. Think of a chair with one leg too short.