Zero CV joint angle

[BrettL]

Just wondering what the pros/cons are with setting up a driveshaft with zero angles through the CV joints? Should one end of the shaft be slightly offset to intentionally create an angle through the CV or is it ok to run a CV at small to no drive angle?

 

[MikeHalloran]

U-joints die early if their internal needle bearings don't roll far enough to distribute the lubricant, e.g. far enough that their tracks overlap.

Minimum angle in degrees = 360 / number of needles




Mike Halloran
Pembroke Pines, FL, USA

 

[BrettL]

Sorry Mike, should have specified that I was talking about ball type CVs on front wheel drive or IRS applications. Thanks.

 

[MikeHalloran]

Take 'em apart. You'll find needles.



Mike Halloran
Pembroke Pines, FL, USA

 

[patprimmer]

Mike

I think this is what he is talking about.

http://en.wikipedia.org/wiki/Constant-velocity_joint

Regards

eng-tips, by professional engineers for professional engineers
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[MikeHalloran]

Ah. I thought he was talking about double- Cardan or two- ball or tripod joints.

The Rzeppa joint is different. It needs even more angulation to avoid false Brinelling than do joints with needle bearings.

If he's talking about an _axle_ shaft, where angulation is guaranteed by suspension travel, then the static angle doesn't greatly affect joint wear.

If he's talking about a _drive_ shaft, which is what he said, then the Rzeppa joint wouldn't be my first choice.



Mike Halloran
Pembroke Pines, FL, USA

 

[BrettL]

Sorry guys, yes I'm actually talking about an axle shaft and Pat's link is the type of joint I'm talking about. So I take it from what you're saying Mike, suspension travel should be enough to overcome any problems that may arise from having little or zero static angle? Having said that, I guess it wouldn't hurt to have some offset at one end of the shaft to ensure articulation of the joint??

 

[patprimmer]

If the height of the diff is set by ground clearance and interior space or CG requirements so it's output spline or flange is at wheel centre height, fore and aft displacement also works and may even benefit total possible suspension travel if it is thought relative to the fore and aft movement of the wheel during suspension travel.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[MikeHalloran]

It shouldn't hurt.





Mike Halloran
Pembroke Pines, FL, USA

 

[GregLocock]

In production cars, with say +/- 20 degrees of suspension articulation, our usual problem is running out of articulation, as opposed to needing more.

For a race car I wouldn't sweat it - you'll get more than a season out of a stationary CV joint, at a guess.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[Fabrico]

I doubt offset will change things much in that situation. Suspension movement should be enough. The AWD Jeep Grand Cherokees have a Rzeppa front joint with no visually detectable angle at ride height. It's actually a fairly long shaft so I don't really know why they went that route. It may very well have been done due to the lack of angle.
Still being very tight at 180,000 miles suggests that they made the right decision.

 

[BrettL]

Thanks for the help guys... much appreciated.

Cheers, Brett.

 

[GregLocock]

Fabrico - steering lock

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[Fabrico]

Steering lock? It would be obvious on axle shafts. Can you shed some light on how it relates to the drive shaft?

 

[GregLocock]

Oh, I hadn't realised you meant the prop shaft. I call them prop shafts and half shafts.

You'll notice alot of propshafts run very small angles in their joints - and I really don't know why we get away with it.

Historically some companies offset the diff in plan view on IRS installations.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[Fabrico]

The Jeep is solid front axle, so there is some up and down on the prop shaft(!). The forward facing 4-link makes the slip joint, just behind the CV, virtually not move at all.

 

[MikeHalloran]

By an odd coincidence, my 2002 Explorer (Eddie Bauer V8 2WD) developed a new noise/ vibration from the rear axle (IRS), a munch/crunch at driveaway that is more pronounced if the front wheels are turned. It goes away at a couple mph, and there are no symptoms at highway speeds, except maybe a little more gear noise on float than I remember from last month.

It was just noticeable and not localizeable until halfway through a 1500 mile trip, wherein it's gotten progressively worse. Examination showed the left halfshaft can be moved radially a mm or two. This does not seem like a good thing.

The last 200 miles of the trip was in hilly country, and the noise seems to have abated, at least temporarily.

IN MY IMAGINATION, it's the sort of noise/ graunch/ vibration that a Rzeppa joint would make if the ball cage were fractured. I DO NOT KNOW if there is in fact a Rzeppa joint in the halfshafts. The inner joints are Tripods; the outer joints are smaller, and of course enclosed.

We are taking it to the Ford dealer on Monday for diagnosis. In the meantime, anyone care to speculate?



Mike Halloran
Pembroke Pines, FL, USA

 

[Fabrico]

I hate to keep mentioning the Jeep, but they can bang/munch/crunch if you change rear lube without adding the proper type and ampount of additive for the anti-slip differential. At very low speeds, it can feel like someone bumped the car from behind, even while moving in a straight line.

 

[MikeHalloran]

I've lived with a Posi. Not this problem.

It feels like a Cardan joint with missing needles, at a crawl, then it goes away as you get rolling.






Mike Halloran
Pembroke Pines, FL, USA

 

[Fabrico]

Let us know what they find.