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How do you set up the pinion angle on an IRS?
I figure you can not have the rear pinion to point the normal 3 degrees upwards on an IRS setup, because then the up and down wheel movement will not be vertical?
And then the engine must stay horisontal too? To avoid vibrations?
Or am I wrong here?
Pinion angle really has no bearing on an IRS. The housing is mounted solid to the frame so it doesn't move with the suspension. There may be some designed into the housing to frame mounts but this would be minimal and only for u-joint longevity.
"Rotating" the housing, as you say, for pinion angle will have no bearing on half-shaft or wheel movement as this is controlled by the suspension arms. You could actually have the pinion pointing straight up and the half shafts wouldn't care...
Mark
My english could probably be a lot better.
I've been told that to avoid vibrations in the drive shaft, the pinion angle should be parallell with the outgoing axle from the transmission (parallell does not mean at the same high.) This isolated fact has nothing to to with what kind of rear axle is used. A drive shaft who wibrate because of zero degree on the rear halfshaft and 3 degrees on the front halfshaft, will do so no matter live or independent axle, I suppose.
Normally a CSB motor leans back with app 3 degrees. That mean the pinion angle must point app 3 degrees upwards to avoid those vibrations.
On a live axle a given pinion rake does not affect the up and down movement, but on the Jaguar independent rear axle the the pinion is horisontal when the wheel moves vertical. That's the issue.
You want the center line of the engine, transmission to be parallel to the center line of the pinion or main shaft if it is a quick change. If you are building your chassis on a frame jig and the frame is level just figure the amount of rake you will have in the car at ride height and how much angle you want in the engine, then set the rear end mounts accordingly and weld it in. Sounds simple, be careful.
On a street car, IRS or not, set your pinion up 3 and your engine down 3. This helps with vibration, but it also "exercises" the U-joints, and prevents the bearings from galling.