Can You Just Cut A Prop Shaft And Put In A Universal Joint?

[Heckler]

I can think of several cars that used Hardey Spicer joints in end thrust situations as suspension members. Jags and Triumphs are two. CV joints, of course, not. With the very slight angular variation in a prop shaft, simple Hook's joints (Like HSs) would be fine.

They say ignorance is bliss, it was a 30ft double ended clinker lifeboat convert, with a diesel tractor engine. The UJs took the strain ok
Stu

 

[Bobobolinsky]

I would bite the bullet, if you can't just remove the box, then lift the engine out the way, it is not that difficult to lift a half tonne engine, with a £50 chain block

 

[Avocet]

They say ignorance is bliss, it was a 30ft double ended clinker lifeboat convert, with a diesel tractor engine. The UJs took the strain ok
Stu

A suitably sized UJ shouldn't have a problem with thrust loads. As has been said, Jaguar used them in their half shafts for many years, and the half shaft doubled as the top wishbone, taking a fair bit of compressive load in the process. The bearings on each leg of the cross don't actually "know" what direction the load is coming from.

 

[pohopetch]

The setup of a thrust bearing at the end of the shaft and then a pair of UJs with a short shaft between them connecting to the gearbox is a very common setup in commercial/fishing boats and larger yachts (>40ft) in many parts of the world. It eliminates so many problems associated with direct coupling such as constant adjusting of engine mounts and wear on gearbox bearings. We have a shortened land rover driveshaft on our 43ft steel yacht - the shaft was cut to shorten it to about 400mm between the UJs and an off-the shelf (£10) thrust bearing takes the strain. With UJs you must remember that they can't run in a perfectly straight alignment without abnormal asymmetrical wear on the joints so they must be offset 3 or 4 degrees (can't remember the extra angle). If you currently have a directly straight alignment you will have to raise or lower the rear engine mounts a touch to get things out of line. If you use an Aquadrive marine CV joint then you can go straight but you will pay 5 to 10 times as much.

 

[clyst]

I can think of several cars that used Hardey Spicer joints in end thrust situations as suspension members. Jags and Triumphs are two. CV joints, of course, not. With the very slight angular variation in a prop shaft, simple Hook's joints (Like HSs) would be fine.

Not sure which application you are referring to on the jags and triumphs . Where is the thrust ???? If I'm wrong pl except my apologies .

 

[DownWest]

Not sure which application you are referring to on the jags and triumphs . Where is the thrust ???? If I'm wrong pl except my apologies .

Swing axle Triumphs (Herald, 1 to3 Spitfires) took the wheel side loads straight to the diff via a UJ on the inner end of the shaft. Jags used the driveshaft as the top suspension member as explained above. Ditto the Lotus Europa. I think the s/axle Renaults where the same as the Triumphs.
The UJs used in Halyard and Aquadrive are Homokinetic (sp) as in FWD cars outer joints and can't take end loads, hence the thrust bearing blocks.

 

[davidej]

Not sure which application you are referring to on the jags and triumphs . Where is the thrust ???? If I'm wrong pl except my apologies .

Look at any jag of the 60's/ 70's with IRS - E-type, XK6/12, etc. A lower wishbone and a half shaft (with a U/J at each end) acting as the top wishbone.

 

[fisherman]

A suitably sized UJ shouldn't have a problem The bearings on each leg of the cross don't actually "know" what direction the load is coming from.

This is what I always wondered, but remember a few failures in car engine/gearbox/U/J setups. Maybe it's more to do with intermittent use and the liberal application of salt water. Would concentrated lubrication of the U/J solve the problem? Waterproof grease and grease nipples on each leg?

 

[Lakesailor]

Not sure which application you are referring to on the jags and triumphs . Where is the thrust ???? If I'm wrong pl except my apologies .

Jaguar IRS

 

[DownWest]

Thankyou LS,
From the pic,when weight is on the system, the shafts are in compression. If you have just gone over a hump-backed bridge and are off the ground, there will be tension in them. Cornering will give both, depending on which side.

 

[Avocet]

This is what I always wondered, but remember a few failures in car engine/gearbox/U/J setups. Maybe it's more to do with intermittent use and the liberal application of salt water. Would concentrated lubrication of the U/J solve the problem? Waterproof grease and grease nipples on each leg?

Hard to say really. I guess you'd need to look at the failed units to see whether the little needle rollers inside the joints were rusty. I imagine that there are a whole lot of strange vibrations and / or torsional oscillations in a marine installation that might kill a UJ - even though on the face of it, the UJ was adequately sized. I know our little single cylinder unit will have quite dramatic crank speed fluctuations every time it fires, and I don't know what that would do to a UJ if there was no rubber in the system to absorb that shock. At least there's very little torque, and I suppose that in a system that had to transmit more torque, it would have more cylinders to even out the power delivery.

 

[Lakesailor]

Are you sure about the fluctuations in crank speed? Most single cylinder have pretty massive flywheels to iron out those.

 

[Avocet]

Pretty sure. On many car engines, misfire detection is done by measuring crank speed fluctuations. If the crank speed fluctuates when a V8 petrol engine misfires, I reckon it must REALLY fluctuate every time a single cylinder diesel fires - especially at low RPM!