pic: Welded VP carrier



We modded this Versaplanatary carrier by welding the pins because we had issues with them backing out and seizing the carrier from rotating. It’s a pretty simple fix, and we’ll probably be doing it on all our Versas next season

Why not just peen the pin?

Have you considered: not overloading the gearbox.

The pins backing out was never a load-case for us. Seemed to be happening with VP’s that are subject to constant start-stop loads.

Peening is just striking the pin with a chisel or drift in order to “notch” the pin into place. Usually if the pin is slipping slightly, but not outright failing, just a little more mechanical engagement is enough to lock it in place for good.

This post comes across as really snarky and unproductive. CD already has too much of that these days.

Anyway, this failure mode isn’t exclusive to overloaded gearboxes, and is something that’s been done before and posted about on CD to strengthen the 10:1 stages specifically.

Having been on a team that did this… I believe it’s more peace of mind. If you have the ability to weld it’s a no brainer, who wouldn’t want to fix arguably one of the only flaws with the VP?

I’ve never seen that failure mode on a VP gearbox. The discussion so far leads me to believe it’s pretty common though. What applications are you guys using them in that lead to the pins backing out?

This is more correctly called staking. Use something similar to a Starrett 264C center punch to displace the pin end outward diametrically, which will create a short interference fit.

Peening is a surface treatment process to induce compressive stresses, and strain hardening. (shot peening)

Thanks for the correction, I was searching for the word before having coffee.

I had this happen on a 90:1 (10:1 followed by a 9:1) on an arm in 2016 with about 120in-lbs of static torque. It did reverse fairly often and had other issues, but ultimately the pins in the VP did back out. Pressing them back in with some loctite (not sure if the loctite helped) seemed to fix it for the rest of the season.

I do this with all VP stages I use, as Harrison said, it’s peace of mind.
The VP is still one of my favorite VEXpro products, this is just an easy way to make it even better.

-Aren

Welding these, while not universally ideal and possible evidence of an inelegant application, is a lot less potentially harmful than constant disassembly and reassembly of the VPs.

1 Like

Wouldn’t this mean that they are modified and therefore not COTS and not able to be used next season? (If that rule still stands for 2018)

Correct. But what price are you willing to pay for reliability in a match?

Given our budget, likely enough to settle for one of the AM PG gearbox options or a banebots power of 4:1 that we can reuse next year over a VP that we have to modify such that we cannot reuse it. In my rules of thumb, modifying a COTS part beyond reuse costs twice as much as buying it in the first place.

This isn’t necessarily a fault of the versaplanetary transmission; those other transmissions have failure points too. Designing a mechanism to put minimal stress on a gearbox will help the gearbox live longer. I would trust a versaplanetary a lot more than a banebots transmission.

I still haven’t seen the pins fall out of a carrier plate in person, but maybe we’re too easy on our gearboxes.

Banebots P60 transmissions are actually pretty reliable, people put like 1-2kW of brushless power through the low reduction ones and they hold up well.

But it is definitely true for the AndyMark Planetary Gearbox, I really don’t want to see the result of a PG71 or PG188 being coupled with a 775pro, I expect it wouldn’t have a chance of surviving the motor at stall or even in normal use.

If you built a 71:1 and 188:1 VersaPlanetary( not possible to make) and fitted it with a AM 775 you would never get close to breaking it and no modifications would be necessary unlike the PG 71 and 188 which have cheese internals.

Also modifying the gear kit, doesn’t write off the entire gearbox rather just the $15 gear kit.

Interesting, my team has had a few pins back out and the best explanation we could come up with was overloading (it was on a stupidly high torque mechanism, the whole thing was a bad idea by the time it was all said and done). Since then we’ve tried to reduce the amount of reduction done through the VP and add a secondary (or tertiary) reduction via gears, belts, or chain after the VP stage.

This wasn’t my intention, I was trying to make a joke (apparently not a good one).

My comment was based on observations from my experience. The only time I’ve seen pins back out was on very very high torque mechanisms.