Outdrives - Weak point or bad luck?

[glypo]

Down Newbury last night there seemed to be a little bit of a problem with outdrives on the CATs. As far as I was aware 3 CAT SX's were racing (not bad going) and all 3 broke outdrives. Two of which (mine included) had limiters on to stop the driveshafts fouling the cups. Oddly I broke a front out-drive and on the front my driveshafts are well clear of getting stuck.

I think mine can be put down to impact perhaps, but still you would expect a wishbone or something to snap before the differential outdrive - so very odd. The other two cats snapped rear outdrives, so appears to be a case of driveshaft causing the damage.

I just found it very odd that on mine, with the setup on the front my driveshafts should have been well clear of getting stuck, yet I still broke an outdrive yet not anything else.

After doing some modifications I ran the rest of the evening rwd - good news is that the CAT handles fine in rear wheel drive mode

[MattW]

It's a strange one really. The reason i say this is I haven't broken one all year, don't think Si or Grant have either - so it wasn't on the radar at all when the car was launched.

So for me on a personal level there isn't an issue, but clearly there are odd people that are suffering, and i'll be honest and say i don't understand how. I think it is probably a collection of "small" things - as was listed at the top of the built tips thread.

Don't think that answers the question!! I believe they are looking at making modifications for the next batch to try and eradicate, but we'll see i guess.

[AmiSMB]

I was one of the drivers whos rear output cup broke on Friday and mine went when I had a car hit me from the side very hard as he came over the table top and missed the down ramp! My car was his buffer for a soft landing!! I was running one o-ring on the shaft to stop the drive shaft from hitting the cup but think that I may have to run two or even run a 2mm limiter from my Losi xx-4 to stop this from happening again. I also have one of the other drivers diff which also went and have noticed that the two diffs I have here that have failed are the female output cups U3336. Glypo did your female side go as well?

Upon examination it also looks as though the output cups may have been hardened too much as the metal has fractured straight across where the slot has been machined for the dogbone and there is also tiny amounts of metal that have fractured off where the dogbone pin runs inside the slot. I have included some pictures in this post.

[glypo]

Looks like mine fractured differently to yours.



This is the male side as well. Does look to be a brittle fracture, so over hardening is certainly likely - and explains why team drivers like Matt have no experienced problems.

[telboy]

Hmm, I didn't have any issues with mine at all on my first run with it. And I'm not running any limiters. For some reason, straight out of the box, mine didn't catch on the outdrives.

Maybe with cars hitting them, it a problem when they have force applied from an unfamiliar direction?


Strange

[glypo]

My cat was fine first time out too. It was still awesome handling last night until it went snap. Mine was a definite impact situation rather than the driveshaft catching on it. Sounds like Grant has a similar issue judging by what he said above.

I just found it odd that the outdrive could snap but not something like a wishbone which you would expect to go didn't. Well... not until I smashed a wishbone when my cat was in rear wheel drive mode lol.

[robknasel]

Hello,
Be sure to order a few of these parts for your CAT SX, Also front arms, the plastic and non composite front arms will hold up a little better.