Beautiful. I suspect that the multiple mounting points for each CIM are to vary the belt tension? Also curious on what you did to manufacture the plate with a gradual and accurate bend. The details on this gearbox are amazing!
Wow, almost thought that was a render at first. Neat idea using pulleys for your first stage of reduction - I’m guessing that was to allow you to locate your output shaft off to the side like it is (motors over the wheel well?).
Beautiful gearbox, as usual.
Firstly, thank you! Your guess is exactly what they are, they adjust the CIM’s C-C Distance from +0 thou to +50 to account for manufacturing tolerances. As for the shield, the one pictured was actually manufactured by one of our sponsors but we are in the process of making a rig to bend the plates. Once they are completed/anodized we will be replacing them with ours. (We are testing different curves for bending so that once the plate springs back from the bend it will be in the correct shape)
I did use belts on the initial reduction so I could put the motors wherever I wanted and the motors do hang over the center wheel.
I’ve yet to see a gearbox from you guys that isn’t a work of art. Such s nice gearbox
Just incredible, so compact and light. Never thought of using belts on the motors, the weight savings must be huge.
That has just been the past few years. Glad to see a tradition getting started though!
Would love to see the other side with the gear shifting layout. Is there a encoder on the transmission? Neutral?
Unfortunately I’m not sure when I will be able to post a side view as, but I can give you a some details and will post a picture once the others are assembled.
The gearbox features a custom ball shifting mechanism running at 19.5 ft/s and 8.5 ft/s with VexPro (originally 1/2" Hex) Gears on R10 Open bearings from USA Bearings and Belts (unlike the bushing in the VexPro gearbox). There is an encoder from US Digital encoder (S4-120-250-N-S-B) on a 3D printed mount connected to the shaft with the two black plastic pulleys via a section of 1/4" ID surgical tubing.
I am surprised you opted to have the 2 CIMs with the pulleys at the shaft tips and the one with the pulley at the bushing.
Is there any specific reason for this? I would have thought the other way around would be better.
The main reason reason was so that the various mounting holes for the motors were not covered up by a belt, also I prefer having the longer lengths of belts closer into the plate.
Another thing I forgot to mention, the gearbox actually is 2 CIMs and 1 MiniCIM, with a CIM and MiniCIM sharing a belt.
You guys have certainly elevated drive train gearboxes to an art form. I think the thing that strikes me about them is the level of detail and thought put into them is not often seen in a six week design window, even from the great teams. Good luck this season
I believe they at least partially develop thse gearboxes in the fall.
Champions are made in the offseason.
What size belts and pulleys did you use? Have you seen any issues with the belts so far?
Over the past few years, prototypes have been built in the fall to test the new ideas and designs that are part of each gearbox. This has been very important because over the last three years the gearboxes have used untried and unproven concepts. The construction techniques and gear choices of the worm and bevel gearboxes were new and needed to be proven to work before we could decide to use them duing the season. This year the main thing that needed to be proven was the redesigned ball shifting shaft. We liked the ball shifting concept but thought the vex design could be improved. This design has as single piece output shaft, and use open bearings in the gears instead of the bushings.
The belts are 9mm wide, 3mm pitch Gates GT2 belts. The pulleys on this gearbox are 20T aluminum and 48T nylon filled ABS. I don’t know how they’re preforming on this gearbox so far but we used the same belts on last years drive gearbox, shooter gearbox, and the prototype for this gearbox with no problems when the belts are tensioned.
You’ll be happy with the belts in that application. They’re plenty strong.
Hard to say how I feel about the engagement on the two CIM belt though.
Yeah, I expect no problems with the strength of the belts.
The prototype used 16T pulleys and an idler to get proper tooth engagement. That was stepped up to 20T to hopefully make an idler unnecessary and still have enough engagement.