Vehicle & Technical > Defender

which prop for lifted defender 2.4 tdci

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SteveG:
The only reason for not fitting the Disco II cardan prop is that it's a sealed unit with no grease nipples. If you start to use it often off-road it lasts about a year. Hence it's a false economy going for the cheaper Disco II one.

Cheers

Steve

thermidorthelobster:

--- Quote from: SteveG on September 06, 2008, 09:42:32 ---The wide angle prop was really bad advice. This just stops it binding at maximum working angles and does nothing for the actual working angles of the prop.
--- End quote ---

Can somebody explain this a bit more?

Surely if it stops it binding at maximum working angles, then by definition the maximum working angles are increased.  Isn't the maximum working angle the point at which it starts to bind?

clbarclay:
David

What he is saying is a simple UJ working at an angle of say 10 degrees is still working at 10 degrees regardless of whether its a standard UJ which or wide angle UJ capable of working at 30 degrees. At a 10 angle the variations in speed and hence viberations are still the same.

To reduce the vibrations in a prop shaft 2 UJ should be paired, correctly phased and working at the same angle to cancel out the speed variations. In a standard setup this should be done by the UJ on each end of the propshaft, but on lifted and castor corrected setups the UJs end up working at different angles.

Eeyore:
Yep, Mr Barclay has it spot on.

Quick point of note though from reading the above:

A single hookes-type universal joint (two yokes, one cruciform) is a 'cardan joint'.
A shaft, with cardan joints at each end is a 'cardan shaft'.
A joint consisting of two close-coupled UJs is a 'Double-Cardan' joint.

Might make a difference if you're on the phone to someone.  ;)

That aside, Steve and RRB are correct with what they're saying - a wide-yoke shaft was not the solution to the problem - a DC shaft was.

thermidorthelobster:
Thanks, Chris and Eeyore, it makes perfect sense now.  Nearly.

If I understand it right, the idea of a CV (Constant Velocity) joint is also to cancel out the speed changes, hence the name presumably.  Do they work in the same way?

And if you have a double-cardan joint (have I got this right?  The thing Chris describes) at ONE end of the shaft, and a normal UJ at the other end, surely you end up with the driven end of the shaft going in and out of phase with the driving end?  I'm thinking...  engine turning at constant speed, driving a double-cardan joint, so prop shaft turning at constant speed;  then prop shaft turns a UJ, which turns the diff, but as the UJ isn't giving constant rotational speed (ok, angular velocity) then the diff is going to be speeding up and slowing down all the time.  In which case doesn't it make more sense to have one at each end of the prop shaft?

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