Mark :
Although I think I disagree with some of Barry's details, I believe his
explanation is correct in essence, and that the two driveshaft (prop shaft
if you prefer) yokes should be in the same plane.
I'm not sure I can explain any better than Barry, but :
Think of an input shaft and an output shaft, running at right angles to each
other. If they are fitted with bevel gears, it should be obvious that the
gears mesh in a plane exactly between the axis of the input and output
shafts, giving a constant radius from the point of contact to the axis of
each shaft. If the gears are the same size, the input shaft and output
shaft turn the same speed (within the limits of the contact point moving
across a tooth face).
Now, imagine a U-joint in the same situation. (Ignore for the moment that
U-joints don't work well at right angles.) The virtual point of contact no
longer moves in a plane, but moves back and forth from one side of the plane
to the other, as the leg of first one yoke then the other moves into the
common plane of the two shafts. As it does, the radius to each shaft axis
changes in turn, which changes the effective ratio between the input and
output shaft, so that either the input or output shaft must alternately
speed up and slow down as the joint turns, to keep the other shaft turning
at a constant speed.
However, if we turn the input shaft at a constant speed with the engine,
then run the varying speed output shaft (drive shaft) through another
U-joint, operating at the same angle and in the same phase, the speed
changes imposed by the first joint will exactly cancel out the speed changes
imposed by the second joint, and the input to the differential will turn at
a constant speed.
BTW, although I haven't seen a response from Brian, this problem (and the
'same plane' solution) is written up on the PowerBritish Tech tips web page
at http://www.pond.com/~britcars/techtips.htm
Hope this helps.
Randall
> -----Original Message-----
> From: Evans, Mark
> Sent: Wednesday, January 19, 2000 7:42 AM
> To: 'triumphs@autox.team.net'
> Subject: Drive shaft phasing consensus
>
<snip>
> Please,
> any of you that
> haven't responded, please do so. An on-list discussion might
> be helpful to many.
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