Christian S. Hansen
Post Number: 692
|Posted on Wednesday, 31 January, 2018 - 08:08 pm: |
1930 Springfield Phantom I S426MR
All of the RR and B vehicles with manual transmission that I have ever had (pre-war and early post war, small and large horsepower) exhibit a "whine" in first gear which has no synchromesh. Even worse, the Springfield cars have a three speed crash box without synchromesh on ANY gears which is an unfortunate tradeoff when they designed the left hand steer chassis.
What is it that causes this "whine"? On all the other four speed Derby transmissions once you get above first gear, the shifts are is silky smooth and run quiet. What is it about the first gear??
The Springfield three speed crash box even has "whine" in second, but third speed is quiet. Why would there be "whine" in second, but not third in this particular case?
Post Number: 148
|Posted on Thursday, 01 February, 2018 - 04:06 am: |
All gears make some noise. First gear is a straight cut tooth whereas synchromesh second and third gears are helical cut (at an angle) so the first gear has much less surface area to carry the load. The load is also much higher on first gear due to the gearing ratio and force acting upon the gear teeth. These two factors are why the whine is much louder on first gear.
Third is quiet in a straight cut (or helical) third gear in a three speed transmission because the load is not being transferred through the laygear. Third gear is locked in with the synchro hub so the engine torque is transmitted straight through the mainshaft to the tailshaft. First and second transfer the engine torque from the input shaft down to the laygear then back up to the tail shaft. In third gear there is no load on any of the gear teeth.
SRH8505 SRC18015 SRE22493 NAC-05370
Christian S. Hansen
Post Number: 693
|Posted on Thursday, 01 February, 2018 - 06:57 am: |
Thanks for reply.
"All gears make some noise"
Yes, but while that may be true, you know what I am referring to...that typically the noise made by gears other than first is (unless there is something wrong) below the minimum acceptable noise level and thus not noticed, whereas there is never ANY mistaking the noise generated in first gear.
So...that first gear noise is due to the design of the gears rather than wear from crashing the gears over time? That is, when delivered by the factory, first gear made the whine because of the gear tooth design, yes?
Second question regarding second gear whine: Given that the Springfield three speed (specifically) is a total crashbox with NO synchros ANYWHERE either shifting up or down, it is almost impossible to shift either up or down without a bit (or a lot) of gear gnashing. Therefore is it possible that the second gear whine is due to wear rather than gear profile design?
Posted From: 22.214.171.124
|Posted on Thursday, 01 February, 2018 - 03:53 am: |
It is because they are old men and old men whine.
Actually it is due to the fact that the gears are straight cut, the driven gear width is quite small and the tips squeeze the oil out. There is also quite a bit of back lash.
Top or 3rd on the 3 speed box is direct drive where the 2nd speed gear dog is rammed into the input shaft. The only gears then connected in drive are the constant mesh input and lay gears which are helical cut.
The 3 speed gearbox is the principal cause for the failure of the R-R 40/50 in the 1912 Alpine Trial, when driven by James Radley. It stalled on the Katschberg Pass in Austria, and failed to restart. The car was overweight.
R-R re-installed more developed 4 speed boxes, in 4 lightened chassis with more powerful engines, for the 1913 romp and took the first 4 places. Alpine Eagles.
Carlos de Salamanca won the Spanish GP in June 1913,over the mountains, 90 in the shade driving a similar car,Eric Platford came 3rd.
(Message approved by david_gore)