By Geza-aka-Zombo - Mon Aug 02, 2021 8:29 am
- Mon Aug 02, 2021 8:29 am
#95331
Anyone following this? Brown seems to be convinced that the torsion stress in the driveshaft is opposite if the shaft is assembled in the TT backwards. Several people are trying to straighten him out, but he's too obtuse. As Lt. Col. Frank Slade would say: "We've got a moron here". I think a clear description of what's happening is as follows:
Picture a wrench on the engine side of the driveshaft applying torque in a CW direction (like the engine would), and a wrench on the trans side countering this torque in the CCW direction (when viewed from the engine side), like the transaxle would. Now, while the torque is still applied, move your vantage point to look at the driveshaft from the trans side. Bingo - swapping the side of the driveshaft which is on the engine side does not change the direction of the torque the driveshaft sees. So, the answer to his question is his driveshaft, if in good condition can be reused without issue.
He mentions torsion bars and driveshafts (half shafts) - That these should not be swapped side to side, which I can agree with. In both cases, swapping these does change the direction of the torsion, which impacts fatigue life. If you have a torsion bar, which has been deflecting from 0 to ~20 degrees CW it's entire life (as the suspension moves), then start deflecting it 0 to ~20 degrees CCW, because you moved it to the other side of the car, it's going to reach its fatigue life at a much accelerated rate. So, don't do that.
Summary: depending upon which side of the driveshaft is attached to the engine, the rotation direction of the shaft will be opposite (one side vs. the other), but the stress direction will be the same, either way.
Picture a wrench on the engine side of the driveshaft applying torque in a CW direction (like the engine would), and a wrench on the trans side countering this torque in the CCW direction (when viewed from the engine side), like the transaxle would. Now, while the torque is still applied, move your vantage point to look at the driveshaft from the trans side. Bingo - swapping the side of the driveshaft which is on the engine side does not change the direction of the torque the driveshaft sees. So, the answer to his question is his driveshaft, if in good condition can be reused without issue.
He mentions torsion bars and driveshafts (half shafts) - That these should not be swapped side to side, which I can agree with. In both cases, swapping these does change the direction of the torsion, which impacts fatigue life. If you have a torsion bar, which has been deflecting from 0 to ~20 degrees CW it's entire life (as the suspension moves), then start deflecting it 0 to ~20 degrees CCW, because you moved it to the other side of the car, it's going to reach its fatigue life at a much accelerated rate. So, don't do that.
Summary: depending upon which side of the driveshaft is attached to the engine, the rotation direction of the shaft will be opposite (one side vs. the other), but the stress direction will be the same, either way.
Geza
'87 Porsche 928 S4 Auto (3rd owner)
Original owner of:
'97 Porsche 986 5 Speed
'99.5 Audi A4 Avant 2.8 5 Speed
'16 Ford GT350 Track Pack
'87 Porsche 928 S4 Auto (3rd owner)
Original owner of:
'97 Porsche 986 5 Speed
'99.5 Audi A4 Avant 2.8 5 Speed
'16 Ford GT350 Track Pack