drivetrain disaster during testing

[drywater]

http://i536.photobucket.com/albums/ff330/blackbrains7/28062008907.jpg
guys
if you look at the image you will get a fair idea of what had happened
during the testing of our car prior to the formula student competition at uk this year we encountered this
the driver heard the slipping of the chain ,he stopped and then we saw that inboard boot of the cv joint had tore apart completely.When i opened the cv housing i found that the lock of in one of the bearings of tripod had been broken and the bearing was about the come out..but was still in place.
what my query is why had this happened
was this because of false positioning of the boot on the driveshaft(we had used taylor race cv joints and boots)?
or was it the broken seal on the tripod?
after that night i got the tripod repaired and set the boot at a new position .luckily that problem didnt occur again and we ran successfully at the event

[drywater]

http://i536.photobucket.com/albums/ff330/blackbrains7/28062008907.jpg
guys
if you look at the image you will get a fair idea of what had happened
during the testing of our car prior to the formula student competition at uk this year we encountered this
the driver heard the slipping of the chain ,he stopped and then we saw that inboard boot of the cv joint had tore apart completely.When i opened the cv housing i found that the lock of in one of the bearings of tripod had been broken and the bearing was about the come out..but was still in place.
what my query is why had this happened
was this because of false positioning of the boot on the driveshaft(we had used taylor race cv joints and boots)?
or was it the broken seal on the tripod?
after that night i got the tripod repaired and set the boot at a new position .luckily that problem didnt occur again and we ran successfully at the event

[FryGuy]

The most likely cause is too high of misalignment in the bearing. The max angle for the Taylor race bearings is 20 degrees (i can't remember if that is total or each way). If you have more than that you will likely overstress the bearing balls and break the clip. I doubt the boot had anything to do with it.

[VFR750R]

Seeing the grease on everything, i concur the boot being ripped did not cause this particular failure.

Street car cv's fail when the grease is washed out after a tear in the boot. You didn't put nearly enough miles or drive in nasty enough conditions (water/salt) to wash out the grease and cause that type of failure.

If your designed halfshafts angles stay at less then 20deg throughout the a-arms motion, also consider deflection of all related parts. Sometimes stack up of tolerances/deflections can be enough to see failures where theory says there is plenty of saftey factor.

[Magnarama]

Hard to tell from that picture but it looks similar to what happened to us last year during testing. When we looked at ours it looked like the most likely failure mode had been that the retainer for the bearings had failed, which then let the roller bearings loose and then everything went up shit creek.

I'm not convinced that it was a misalignment issue either, as we've run that car pretty hard at comp and for driver training and hillclimbs since replacing it with no issues. We recently did a bit of a teardown on the CV's for interest's sake and the tripod housings hadn't shown any extraordinary wear and the bearings all seemed fine.

Would definitely agree that the torn boot shouldn't have been an issue, looks like there's still enough grease in there to prevent failure.

[Brett Neale]

We had a similar failure on one of our TRE tripods last year. They were run at quite an angle, but nowhere near 20deg. We found that the clips on the end that hold the needle rollers in (those pressed sheetmetal things) could be replaced with a properly sized circlip, being sure to keep the needle rollers from coming out when you replace them. We pretty much concluded that this sheetmetal clip failed on ours causing all the needles to fly out and chew everything up...

Of course, this isn't really TRE's fault, as they recommend minimising driveshaft angles to prevent this sort of failure.

EDIT - hehe thanks for that Tommo... you post ninja you...

[drywater]

thanx all of you
i think i can conclude that it was due to high angles of the halfshaft and the depressing condition of the tripod bearing retainer clip.

[Thrainer]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Brett Neale:
We had a similar failure on one of our TRE tripods last year. They were run at quite an angle, but nowhere near 20deg. We found that the clips on the end that hold the needle rollers in (those pressed sheetmetal things) could be replaced with a properly sized circlip ... </div></BLOCKQUOTE>

Hi there,
we're having the same issue with the Taylor tripod's needle retainers. Even though we didn't have an incident, each tripod had one retainer that was bent.

That's an interesting solution, using a circlip, but I'm not sure if it's more or less risky.
Do you still have the same angle in the driveshaft? How long have the circlips held up? Did you do any modifications to the circlips?

I keep reading these tripods can handle up to 20?. That simply doesn't seem to be true. I've heard of several teams, including ourselves, that had severe issues at around 10? max.

Regards,
Thomas
AMZ - ETH Zurich

[drywater]

@Thrainer
we had the same angle witht driveshaft ,instead of a circlip i placed a alumunium plate as a retainer .its far better than a stock retainer.
i will post a picture as soon as our car is back to india.

[FryGuy]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Thrainer:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Brett Neale:
We had a similar failure on one of our TRE tripods last year. They were run at quite an angle, but nowhere near 20deg. We found that the clips on the end that hold the needle rollers in (those pressed sheetmetal things) could be replaced with a properly sized circlip ... </div></BLOCKQUOTE>

Hi there,
we're having the same issue with the Taylor tripod's needle retainers. Even though we didn't have an incident, each tripod had one retainer that was bent.

That's an interesting solution, using a circlip, but I'm not sure if it's more or less risky.
Do you still have the same angle in the driveshaft? How long have the circlips held up? Did you do any modifications to the circlips?

I keep reading these tripods can handle up to 20?. That simply doesn't seem to be true. I've heard of several teams, including ourselves, that had severe issues at around 10? max.

Regards,
Thomas
AMZ - ETH Zurich </div></BLOCKQUOTE>

Keep in mind that it is 20 deg. of full misalignment, not just up and down. If your axles are angled forwards or backwards, that adds to your misalignment and needs to be considered. Im not saying that's your problem just that its something that needs to be considered.

Regardless, the tripods are going to work best and most reliably if angles are held to a minimum.

[Scotty]

Guys,

I am sorry to hear about all of these issues.

I have said before that Max angle of the tri-pod is 22 deg.But that might get you across the parking lot.
The closer to zero the better. I would max them out at around 12 to 14 deg.

If there are small flat spots on the retainer,then this joint is coming in contact with something.Is the axle too short ,and coming out of the housing ,
I need to know from the teams that are having issues,,Is it with our housings,or housings that you have machined.

Please send me pictures of the T.P and housings.
Lets see if we can figure this out.

scotty
scotty@taylor-race.com

[Erich Ohlde]

we had a similar problem that we traced to an incorrect plunge setup. We basically were allowing the axle to float. We fixed the problem by pinning one of the plastic plungers under one of the tripods and allowed the other end to be free floating (with the plastic fill rod and spring of course). We are running pretty high misalignment (i think more than 10 degrees)

[Brett Neale]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Scotty:
I need to know from the teams that are having issues,,Is it with our housings,or housings that you have machined. </div></BLOCKQUOTE>
Our housings were in-house aluminium outers and EN26a inners, using 16deg maximum total angle at full bump, and we were fully prepared for any problems we thought we may encounter. However we only had one failure for the life of UARC07 (which probably has about 60 hours of testing, tuning, competition and hillclimbs on it by now).

If you're looking into using between 10 and 15deg driveshaft angle with aluminium CV housings, then I would highly recommend inspecting them often. We committed to a few inspections over the course of the car's life, as if you can pick up one of these failures before it does more damage then you'll thank yourself later. If you go this route, be prepared for issues, design/machine your housings properly and TEST before comp!

[drywater]

hey guys
we had the the taylor race tripod as well as the taylor race cv housings(4340) and custom made stub axles,although we didnt have a plunger system at all and the drive shafts were around 10degrees.all our tripods(four in number) had the same problem witht he needle retainers.But one issue was that we reused our tripod from our last year car.the retainers were very bad in shape.

[Wesley]

So you'll have to excuse my ignorance, but what actual purpose do the plungers serve? Are they simply to prevent axle walk and bottoming out the tripods in the hubs? I suppose they'd have to be sprung if that were the case to prevent bending an axle due to suspension motion...

I think I may have just answered my own question...

[Drew Price]

Exactly. The bearing surface of the tripod housings is straight, so there is nothing to keep the bearing and the housing at the same 'plunge position.' The plungers push against each other and center the halfshaft between the two housings.

It's my understanding of the R-Zeppa / VW constant velocity joints the way that the curved races for the balls are shaped they naturally center the inner race to the outer as you apply drive torque. The drive shafts have to be pretty close to the correct length though, or I think it will wear the joint out faster, with the inboard and outboard joints fighting each other. There is less available plunge too.

Best,
Drew

[Scotty]

Drew,

You are correct sir....

A CV joint will self center itself .
The non-plunging CV is used at the upright in front drive cars where high angles are needed.
The CV on the diff is the plunging side.This is why a CV are popular in street applications.They are simple...
A tri-pod will not center by itself.Without a plunging system..the axle will shutter back and forth during differant speeds.

scotty

[Drew Price]

Scotty,

Without a comparably sized tripod and CV joint in front of me, could I assume that the tripod would be lighter, and have less rotating inertia than the CV? Less friction too I imagine.

Best,
Drew

[Scotty]

Very much Drew.

One of our lightend 94mm CV joints with an outboard stub , boot and 6 bolts will be in the neighborhood of 3.5 pounds.And an O.D of 3.700 inches
The same type of stub axle in tri-pod form will be around 2.3 pounds with a OD of 2.500 inches.

scotty

[Drew Price]

Thanks for the numbers Scotty.

Best,
Drew