pic: 865 flipped CIM WCD gearbox



We really liked the versablock style mounting of WCD gearboxes but the implementation on the 3 CIM ball shifters left a lot to be desired as the 8-32s connecting the versablock to the ballshifter would inevitably loosen and become impossible to access at the worst of times. This alone would not be enough of a reason to use a custom solution but we liked the idea of a clean bellypan left by a flipped CIM gearbox.

The gearbox uses a 15mm GT2 belt on HTD pulleys as a second stage to improve compactness at the reduction we wanted. Half of the versablock is integrated into the front plate.

Belt run: https://fbcdn-sphotos-h-a.akamaihd.net/hphotos-ak-xfp1/t31.0-8/s960x960/10957713_10155200002215576_2366719353887078451_o.jpg

Versablock integration: https://fbcdn-sphotos-a-a.akamaihd.net/hphotos-ak-xpa1/t31.0-8/10991492_10155200000980576_856114348624306083_o.jpg

The gearbox was designed by a student who hadn’t used solidworks before build season (our drive coach).

I like it :slight_smile:

What are the tooth counts of the belt and pulleys you’re using?

Also, are you doing anything to protect the cims from impact?

Definitely loving the compactness. I’ve always been a bit nervous to use belts in a drive transmission, but it looks like you’ve pulled it off pretty successfully. Props to you for this great design! Is there any reason you didn’t lighten the plates?

Thanks,
the pulleys are 24 and 30 tooth and the belt is a 50 tooth.

The omni sticks out past the CIM motor by about a 1/4 of an inch so that should give it some protection from side impacts. We’ve been considering some sort of “splitter” to prevent something getting in front of the gearbox or a polycarb bumper outside of the transportation area.

Ah ok cool, in the pic it looks like the cims stick past the wheel so I was worried. I just noticed you said the belts were gt3, were did you sorce them?

We were originally going to have the CIM mount plate waterjet cut where ON/OFF cycles are a big factor of machine wear. While we ended up laser cutting them we decided against a lightening pattern due to minimal weight savings and the potential of impact to the gearbox.

My mistake, the belts are GT2 from SDP-SI

I thought I’d update this post with a long term review for those who are looking to do something similar.

I’m happy to report that we had zero issues with the gearbox after three competitions. There doesn’t appear to be any significant belt wear and the CIMs have held up fine after bashing them numerous times.

We also added grayhill encoders for our 3rd competion using the “cheesy poof method” into the input reduction shaft.