I think when they are assembled correctly, they ought to be able to articulate AND "plunge" (i.e. they should be abl to "steer" and the inner cage and balls should be able to move in and out of the outer cage slights (to accommodate slight changes in driveshaft length as the suspension moves up and down).
98 Peugeot Boxer Outer CV Boots Splitting
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Don't the splines do that?
John
John
No, I think they'd either bind up or the wear on them would be too great. If you imagine accelerating hard and hitting a bump, there's a big torque on them right when you'd expect them to slide, so I think the clever bit about the CV joint is the way the joint can take torque, angle and plunge simultanously. At one car manufacturer I used to work for, they pressed the CV joints on to the splines with a press. They weren't sliding for nobody! The splines were machined in a microscopic spiral to make sure they went on tight so that they didn't chatter.Don't the splines do that?
John
An interesting post! I see exactly what you are getting at.
I have wondered - without any particular commitment - that driveshafts with non removable CV's were allowed to adjust their length fractionally by the diff spline connection.
Therefore with RWD applications, the same movement must apply - as the axle rises and falls the splines on the propshaft must accommodate that change in length, tiny though that may be.
John
I have wondered - without any particular commitment - that driveshafts with non removable CV's were allowed to adjust their length fractionally by the diff spline connection.
Therefore with RWD applications, the same movement must apply - as the axle rises and falls the splines on the propshaft must accommodate that change in length, tiny though that may be.
John
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Yes. This was a powerful RWD sports car that we had to press the inners on to the splines for. After a few dozen 0-60 standing starts with huge sticky tyres on them, the splines would have been well and truly "mullered"! The same is true for FWD though. Typically, most independent suspensions move in an arc as they go up and down, so the driveshafts on a FWD would also have to be able to accomodate plunge - maybe 5-10mm something like that. The thing is, as the balls and the cages are already hard enough (and have a big enough surface area to slide relative to each other in order to steer), they may as well use the same bearing surfaces to take up the plunge movement too. The bearing area of the splies is pretty tiny and I don't think would last long if sliding with a big torque superimposed.
Isn't it the inner joints on front wheel driveshafts that allow for the plunge? Ie, joints that use bearings rather than 6 balls? As in this image? And bearing in mind (pun alert) that the angles are nowhere near as extreme as the outer joints.
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That's certainly one way of doing it. "pot" joints - sometimes called "Tripod" joints. Popular on French cars. Not all cars use them though. Some (mine for example) have the same CV joint on both ends of each driveshaft (which is handy because as you say, there's much less movement on the inner one so you can swap them end-for-end every 50,000 miles to even out the wear on them... if you're stingy enough...)!
I thought it would be really easy to go online and find an animation of one, but it's remarkably tough! Here's the best I could find. Scroll down to the "VL Monobloc Tubular shaft" animation. You can JUST see the small amount of slide in the outer joint as the suspension movs up and down. The grooves in the inner static part are elongated so that the balls slide in and out. This happens either when there is an angle between the input and output shafts so that at one point on the circle each ball is near one end of the slot and at the other side of the circle, it's near the other end of the slot. It can accommodate plunge by shifting that range of movement inboard or outboard along the slot. You can just see the inner static part peeping out from isnide the outer part at each end of the suspension travel.
http://www.gkn.com/driveline/our-solutions/cvj-system/sideshaft-solutions/Pages/default.aspx
It also shows other ways of doing it (such as the "pot" joint already discussed and the "ballspline" - which I hadn't seen before, but clearly, there's a limit to how much plunge a CV joint can accept)!
http://www.gkn.com/driveline/our-solutions/cvj-system/sideshaft-solutions/Pages/default.aspx
It also shows other ways of doing it (such as the "pot" joint already discussed and the "ballspline" - which I hadn't seen before, but clearly, there's a limit to how much plunge a CV joint can accept)!
Yes of course, quite obvious really if you've ever rebuilt one! (As I obviously have) Not a huge amount of movement but yes, the spider is effectively locked to the driveshaft, but as it contains ball sized grooves I could see how it could accommodate some plunge motion. There didn't seem to be any though, while I had the driveshaft clamped in a vice, they seem pretty solid when checking that the snap ring has seated properly. I didn't apply any great pressure mind. I'm happy to report that my Boxer is operating normally now though having been reassembled. Hopefully these boots will outlive my use of this van which to be fair is getting a bit rotten. I fancy getting another one soon with an extra row of seats.
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