PROPSHAFT PHASING

jp928

Active Member
#21
Ron, I would need that translated into English as she is spoke by us lay persons. If a shaft with 2 ujs can handle, in phase, input and output axes displaced in one plane (eg vertical, which I think is true?), does another displacement (ie horizontal) cause problems that need the ujs out of phase?
When I used to do race car scrutineering it was common to see driveshafts on open wheelers - short, with sliding joints - out of phase, and different from one side to the other.
 

cobraboy

Well-Known Member
#22
Everybody overlooks the propshaft angles !
Quote from Spicer page, Driveline angles should be equal to or within 1° of each other.
Measuring Angles | Spicer Parts

When I measured the angles on my car the difference was 5 degrees ! How many people bother to check ? none !
And yes the correct spacers were all present. Eventually I got the angles to within 1 degree.
Oh yes the theory behind Rover phasing is interesting, but the shaft is as it is, you are not going to cut it up and change it, but you can do yourself a favour and limit the amount of difference in the flange angles to improve the situation.
Or you can read a load of equations and still have driveline vibration.

All the universal joints have to be perfectly free in all planes without any side to side movement to also ensure smooth operation.
Just throwing in a replacement joint is sometimes not enough, there are different thicknesses of circlip available to set the side to side tolerance on a joint.
 

SydneyRoverP6B

Well-Known Member
Staff member
#24
Everybody overlooks the propshaft angles !

Hi Mark,
That is the angle subtended by the axes of each section that I mentioned in my post and is explained mathematically within the attached pdf.

Ron, I would need that translated into English as she is spoke by us lay persons. If a shaft with 2 ujs can handle, in phase, input and output axes displaced in one plane (eg vertical, which I think is true?), does another displacement (ie horizontal) cause problems that need the ujs out of phase?
When I used to do race car scrutineering it was common to see driveshafts on open wheelers - short, with sliding joints - out of phase, and different from one side to the other.
Hi John,

Imagine two shafts joined by a universal joint. When the axes of each shaft is within the same plane, that is to say that they align perfectly, turning the input shaft to the universal joint means that the output shaft turns exactly in the same way. Now, if we change that orientation by purposely introducing an angle between the input and output shafts in any direction, then as you turn the input shaft you will feel the rotation of the output shaft is no longer the same. For every 360 degrees of rotation of the input shaft, the output shaft will both speed up and slow down which seems impossible, but the impossible happens. The greater the angle between the two shafts, the more pronounced these accelerations will be. To eliminate the effects that not having the two shafts aligned means we need to introduce a specific amount of phase shift into the placement of another universal joint at the far end of the driven shaft. This is what the Rover engineers devised, given that sliding joint, the tailshaft, and the pinion do not all lie in the same plane, i.e., their axes do not align. This phase shift takes into account the speeding up and slowing down of the tailshaft meaning that the pinion will now spin with the same speed throughout each 360 degrees of revolution as the sliding joint.

Ron.
 
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