pic: 4587 Wheel and Chain in Tube Drive

I took a few of the ideas that have been posted the last couple of weeks and compiled them into one drive train. Wheels and Chain are both in the tube. Largely designed off of what our team is capable of machining.

Uses 1/16th 2x1 and 1/8th 2x2.5
4x.875 Colson wheels
16t or 17t Sprockets (Haven’t decided, there are reasons to go either way)
2 cim 3 stage Ball shifters
Thunderhex, and Thunderhex Bearings
27x35" built with the 2012 game in mind, to try to design mechanisms with small round game pieces in mind.
Feel free to ask questions.

Live axles or dead axles and why?

Considering there are bearings in the tube where the wheel axles go I would assume live.

Considering that he’s using 4x.875 colsons, he’s probably using the hex bore ones from Vexpro, so it’s probably live axle.

How is the gearbox + wheel going to be assembled onto the robot? It looks like a pain to me, because the colson would cover up the lower 2 gearbox mounting holes.

You attach the gearbox using the 4 upper holes.

live axles, with all of the cots parts available now days, it makes the most sense and it’s easier to assemble in my honest opinion requiring less parts and bolts assuming you replace the parts I’ve used with similar vex parts.

Also the cool thing with a 3 stage ball shifter gearbox is that the third stage actually isn’t “part” of the gearbox the way it’s assembled makes it fairly easy to mount the gearbox. Additionally given the good track record vex parts have had I don’t expect much maintenance ever to be needed, only in worst case scenarios which can’t be avoided.

Cool design! When our grade11 students showed me their preseason drive train, I envisioned something like this, but they were reluctant to hide the chain, and probably for good reason. Repairs if something goes wrong with the chain would be difficult. Also, I would be wary of using these wheels in a drivetrain, especially one like this where replacing them would be a bit of a challenge. We ordered some samples, and they are tiny! The narrow width means the tread will wear pretty quickly.

Has anybody run these wheels on a drive train before? I’d be interested to see how quickly they wear.

I’m not sure hiding the chain is as big of a deal as you are making it out to be. Several teams have run chain in tube for several years now with good results. We did it this past year (of course no defense so not a lot of stress) and had no problems. In the 4 years that we’ve run #25 chain on our drive train we have never broken a chain nor had significant chain stretch.