24-07-2018, 08:21 AM
This whole topic has been interesting.
For a start , based on a very small sample, I understood the distributor drive pair of gears to be not hardened originally. The loading is very low, intermittent and the rubbing speed modest. The original gears in my car failed at about 70,000 so cannot be many original left, but does anyone know for sure what was used?
I am staggered by the degree of wear experienced with the dynamator drive gear. I wasted a couple of hours burrowing through various ancient tomes acquired from 2nd hand shops over the decades. It seems the term skew gears is a misnomer. Screw gears correct. Of possible interest, if of no practical help, but one book had this to say abbreviated, ”Because of the point contact of screw gears, even light tooth loads set up very high stresses at the point of contact. ...Wear can be considerably reduced ...if the gears are first broken in by operating under light load...and if extensively broken in load capacity can be very considerably increased.” Soft steel on self was given a very low load rating, medium steel on medium steel or on cast iron about 3 plus x better, and ci on ci 4x better! No figs for soft steel on ci.
“In general to avoid scuffing soft steel and ci should not be used (paired or together?) if the pitch line velocity of either(?) gear is considerably over 1,000 fpm “(which with Seven it is) “Screw gears for significant powers should run in oil.”
Starting out with high watts load dubious.
Has it been established what the dynamator drive gear was cut from?
What would be the likely worst material? Free machining m.s? Or ordinary m.s, or tough steel?
I was surprised at the damage. Would reasonably expect a wide tarck to develop and wear then slow.
The life of ci gears remarkable, esp as many bedded in on other cars and at slightly different mount angles.
Can any gear experts comment?
For a start , based on a very small sample, I understood the distributor drive pair of gears to be not hardened originally. The loading is very low, intermittent and the rubbing speed modest. The original gears in my car failed at about 70,000 so cannot be many original left, but does anyone know for sure what was used?
I am staggered by the degree of wear experienced with the dynamator drive gear. I wasted a couple of hours burrowing through various ancient tomes acquired from 2nd hand shops over the decades. It seems the term skew gears is a misnomer. Screw gears correct. Of possible interest, if of no practical help, but one book had this to say abbreviated, ”Because of the point contact of screw gears, even light tooth loads set up very high stresses at the point of contact. ...Wear can be considerably reduced ...if the gears are first broken in by operating under light load...and if extensively broken in load capacity can be very considerably increased.” Soft steel on self was given a very low load rating, medium steel on medium steel or on cast iron about 3 plus x better, and ci on ci 4x better! No figs for soft steel on ci.
“In general to avoid scuffing soft steel and ci should not be used (paired or together?) if the pitch line velocity of either(?) gear is considerably over 1,000 fpm “(which with Seven it is) “Screw gears for significant powers should run in oil.”
Starting out with high watts load dubious.
Has it been established what the dynamator drive gear was cut from?
What would be the likely worst material? Free machining m.s? Or ordinary m.s, or tough steel?
I was surprised at the damage. Would reasonably expect a wide tarck to develop and wear then slow.
The life of ci gears remarkable, esp as many bedded in on other cars and at slightly different mount angles.
Can any gear experts comment?