To be continued… (update from Hartford Regional)
Excellent work and a rousing cheer!!! It’s always good to hear teams solving problems on their own, especially these troubled transmissions.
ya we saw that to the problem was that a tolerance was - not + on the holes
welding has worked very well for us… those carrier pins are not going anywhere.
While welding the pins is a great idea and solution to the problem it still doesn’t help the fact of the tolerances on the gearbox aren’t great and that some teams are asking way too much of these motors. Props to 237 though on comming up with some sort of solution.
To add what I forgot to tell elgin:
That picture of the pins out are of a NEW carrier plate, not the old one. The plates were installed friday morning and the gearboxes were opened that afternoon to change to a dual transmission setup. I think that comes to only 6 matches played with the new plates in.
We measured the top of the hole, and the bottom of the hole. the top of the hole were the pin was allowed to move was ovaled out and .02 inch different then the bottom of the hole.
Hopefully this fix helps some of you, I would recommend taking a peak into the gearbox to see if you have this situation before it becomes a serious problem.
…wish we had access to a welder…
Hopefully there is one (or more) at your only source of repairs on site at a competition, your “FIRST approved machine shop”.
There is usually a TIG welder available at the machine shop
provided in the competition venue. The replacement parts
desk will have a bag of hardened carrier plates for teams to
swap into their transmissions. As soon as you arrive at the
pits, dispatch someone to get two carrier plates and line up
at the welding station to have the pits tacked into place.
It will only take a minute or two with the welder. You can
service the gear boxes on Thursday evening before the
competition matches start.
Not a bad idea. It’ll take a few hours to pull the trannies and then the plates, deliver them to the shop - then I need to hope the shop gets them back to us in time to reassemble everything & get to inspection.
Honestly, I’m really not sure we have the time.
When the plates went in, we did check the pins really carefully, they were all a press fit.
In any case, it’s not my decision, I’m just a consultant - the students need to think this out and decide what they want to do.
Read my suggestion more carefully.
Do not run with the hardened plates without at least welding the pins. Get replacement plates and have someone wait while you’re pulling the trannies. You should be able to disassemble from the front mounting plate if you can get at all 4 retaining screws. you shouldn’t have to take out the front mounting plate/output shaft. This may simplify you changeover. Then be certain the tranny housing is pushed up square to the front mounting plate before lightly tightening the retaining screws, turn the driveline to help center the housing with the front plate and tighten screws carefully. Check that the sytem is turning easily, as any misalignment will cause binding in the gears. Good Luck!!
I really wish I knew the pins would fall out before today. We had them fall out on one drive after the third match at finger lakes.
How common is this failure?
We ran all of our seeding matches (8) and then the quarter finals with the hardened plates… that were not welded. Without any problem. We are using 4 gearboxes - one on each of our mecanum wheels.
But we have not pulled them to inspect them. Maybe we have just been lucky.
The holes on the plate were too large, and tapered, so the engagement is only about 1/3 the thickness of the plate. That coupled with the fact that the pins are shorter than the orginal, will allow them to work out toward the thrust plate, and come loose. It’s only a matter of time before they will fail without warning. Be prudent, and get a set welded at the machine shop, and replace them when you have time. We took the hardened plates, re-drilled and reamed new holes in between the original holes, and press fit proper length pins into the plates with Loctite. Until we can change them at Chesapeake, we are running the original softer plates because we can monitor the Double D hole failure by checking backlash in the drive to see if it increases.