Vex Pro Single Speed Dual Reduction


#1

Hello everyone!

It’s been a good while since I’ve written anything.

Before I post my question, I think it’s valid to say that while I have been a mentor of FIRST Team 3337 for the last nine years, I’ve acted in the capacity of a Business Coach and Facilitator for most of that time. I’ve become decent at understanding design and a few other build areas but I’ve found myself as the full time build mentor as well… at least until I find someone who can replace our recently retired Build Coach.

I’ve also realized how many parts have been bought over the year that haven’t been used again or were never used in the first place and due to our organizational structure (or lack thereof), we’ve been reconstituting a lot of these parts for our use. So - with all of that in mind. . . I have two VexPro Single Speed Dual Reduction Gearboxes that we are using on our WCD styled drive train this year but I can’t seem to find the best way to mount these to the frame.

Any suggestions?

Thanks so much!
Daniel


#2

We had considered those ones before settling on the Toughbox Mini. But perhaps something similar to our setup would work for you. It’s hard to know, without knowing the design limitations or what aspect, specifically, you’re having trouble with!


#3

Good to see the twisted wires! Great job!


#4

My former team (781) used the same gearboxes in the past. We made our own custom face-plates for the gearbox out of 1/4" aluminum plate and made tapped holes to allow for us to use the WCP bearing blocks on the outside of the frame. I wish I could provide you pictures but unfortunately I am at university in another city and no longer with the team.


#5

Based on the name, I assume you mean this gearbox from Vex.

We used these as drivetrain gearboxes for years without any issues. They are a nice compact, lightweight, and fully enclosed solution for single speed with 2 CIM’s.

We always prefer to direct drive one wheel, so no chain failure is enough to take out the ability to drive. We also often move the outermost bearing out into the drive rail (eliminating the bearing in the outer face of the gearbox), so the shaft is supported closer to the wheel, then make up the difference with spacers to keep the gears and sprockets in place.

Our method to mount them to the frame was to create spacers out of either delrin or aluminum, ~ 0.75 - 1" OD, .257" ID, then mount straight to the frame rail with 2x 1/4-20 screws. The spacers stand off the gearbox to make room for sprockets.

Below example was from our 2015 robot. It was H-drive, so only one sprocket. Longer spacers can be used to make room for two. At some point (wider wheels?), a custom output shaft may be needed for this configuration - but I think stock was long enough in our cases.


#6

@Jeffrafa did you include anything to support the motors or rear side of the gearbox? That’s a lot of weight cantilevered off of two #10 (or 1/4-20?) bolts and is likely thus putting a decent load on the output shaft as it passes through the bearing.


#7

With other gearboxes we always do include brackets connecting across the top of the two gearboxes, but I can’t find any evidence we did with these in 2015. By the looks of it, we used Mini-CIM’s, so that keeps the cantilevered weight down somewhat.

The bolts are 1/4-20, and we made the OD of the spacers as large as we reasonably could while still clearing the chain, so this gives a larger bearing surface at the mount point to take up the cantilevered motor weight. Also, since there is a bearing in the frame rail adjacent to the wheel, the bending moment loaded on the gearbox from the robot weight is also significantly reduced.

The other year I recall specifically using these gearboxes was in 2013, where we ran kiwi with the gearboxes flush mounted to the 1x2 frame rail. No additional support, and I think we just ran with stock bearings in the gearbox (no bearing in the frame) but the flush mount reduces the cantilever.


#8

We love these gearboxes. We’re doing it like this so we can tension the chains by sliding them in the slots.