pic: Wheel problem.


Is any other teams having a problem with the rover wheels breaking easily??

How exactly did this happen? Did you do it while driving or did you drop the wheel?

I suggest finding the “macro” option on your camera. It takes clearer pictures up close.

All of ours are holding up fine, but we haven’t driven around yet.

We were drifting and the robot went from the Regolith to the wood floor and back on and then we found the plastic cracked when we were checking the robot.

Forgive the quality, that is what we get with a camera phone, what you may not see are some cracks in the black plastic.

We were driving and when we stopped we found this, supposedly from when we went off of and back onto regolith.

Where these wheels being driven by some sort of hub? They are the same hub as the previous andymark wheels.

And after i noticed this wheel thanks to our team members, i quickly checked the rest of the wheels. and sure enough the other back wheel is ready to give. The front 2 wheels are cracked but they didn’t shatter yet. Could this be a huge issue during competition between the regolith and the carpet?:confused:

I’ll also try to get you guys some photos of the rest of the wheels. Almost like a before… during… and after stage.

Its just using the bearings provided with the wheels and the wheel was driven by a chained sprocket.

were u drifting onto the wood floor? and does the wood floor have a lot more friction? idk maybe the sliding sideways is fine on the regolith but when they go onto something of greater friction the wheels cant take it. i wouldnt think that would cause them to fail but its a possibility

o wait is the hub broke? maybe too much sudden torque like changing directions very quickly

It might be a general stress fracture, considering the wheels (hub and tire) have ZERO give when it comes to bumps, such as driving onto a panel. I sure hope it isn’t common, and that you guys get replacement wheels soon.

can you post a picture of a wheel “as assembled”?

are you using a plate sprocket, or one with hubs?

if you are using a plate, is there enough clearance between the chain and the wheel material, or is there some rubbing?

We have been driving the new wheels for about 2 weeks on a practice chassis (with #35 chain, KOP bearings, fixed axles and aluminum sprockets) and have not seen any issues at all.

it might be the shock from the regolith to the wood… kinda like skidding out on ice then sliding onto pavement.

Don’t use LocTite on you wheels… It dissolves the plastic. Your picture is what our wheels looked like a day after we tapped the wheels for the 10-32 screws and applied LocTite.

Bummer! :eek:

Well we did not locktite the wheels. It was hard enough to get those screws in there after we tapped the holes. But i do know that there is not a lot of friction on the wood. Its a gym floor. basketball court. whatever you want to call it. Theres no hub, just a sprocket spaced by the spacers provided with the wheels. Theres a ton of clearance using #35 chain. So… i hope it was a bad batch or something… because this competition requires drifting and sliding. Who knows what went wrong…

Yeah, a pic of how you mount your wheels to the sprocket would be helpful for advice; however, I’m guessing its how you screwed the sprocket onto the wheel… What I would suggest doing (what has worked for our team this year, and with the past KOP AM wheels) is using a 2" long 8-32 going on the sprocket through the entire wheel, with a nylock on the other end. Tapping may seem like a weight savings, but its a little more work, harder to repair/replace, puts the weight in a smaller area, and may loosen if you don’t use LocTite, which can weaken the plastic!
So, I don’t know what your team was doing, but I think if you reconsider the wheel mount and buy replacement wheels you should be fine!

Yup! i thought about that… I was a little tired after the first 2 wheels we did. So we might end up doing that for competition. Thanks!

If you tapped the wheels to install screas to hold the hubs, you probably waekended the plastic enough to cause this after running.

As suggested above, #8 screws and nylon insert lock nuts work very well and would save you a lot of time.

we were puttin our wheels together on a test bot and one fell off the table to the floor(a 3ft fall) and cracked the white part of the wheel

It shouldn’t be that hard to insert screws after tapping. Maybe you didn’t tap it correctly?

Our wheels are tapped and we haven’t had this problem (although, we haven’t had a lot of drive time either). How far did your screws go into the wheel? Using longer screws might eliminate this problem.