From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Analysis of starter unit pinion engagement, detailing spring modifications and a solution for clutch slipping due to excess oil.
| Identifier | ExFiles\Box 40\5\ Scan196 | |
| Date | 1st November 1927 guessed | |
| contd :- -2- the momentum of the unit is such that the pinion fails to engage at the moment the teeth are opposite, thereby we get the grinding of the two sets of teeth together. Strengthening up the spring D.51133 overcomes this trouble and a satisfactory engagement of the pinion is obtained. Spring D.51545 is now incorporated giving an increased load. If we go a little further into the question of the starter unit, we find that the question of the strength of this spring D.51133 is further demonstrated. When the pinion is fully engaged the spring D.51133 having a load of 7 lbs. is opposed by the return spring D.51144 of 9½ lbs. therefore we have a force of 2½ lbs. which is trying to push the pinion out of engagement and with a free unit does actually push the pinion back .250". With this condition and the flywheel teeth slightly taper due to wear, the tendency of the pinion under load is to disengage. During our tests we found that by increasing the spring D.51133 to 10 lbs. and reducing the spring D.51144 to 8½ lbs. we obtained an all-round improvement of the starter unit. In investigating the slipping under load condition, we find that by increasing the initial load of the spring D.51376 from 31.5 lbs. to 50 lbs. we obviate the slipping. Our explanation of this is that the slipping occurs before the pinion is fully engaged, when the load applied to the clutch discs is little more than 38.5 lbs. which is insufficient for the load imposed upon the starter in this position. By increasing the strength of the spring to 50 lbs. we prevent this slipping and the rating of the spring is not too high to prevent the nut winding up to its full movement, thereby getting the maximum load imposed upon the clutch discs when pinion is fully engaged. In further investigation, we cured the slipping caused by excess oil getting on the clutch, by having 6 grooves ground on the face of the operating bush D.51134 which wipes the excess oil off and is thrown clear by the centrifugal force when the motor revolves. This is now on production and giving good results. With this scheme the unit is well lubricated with Price's Motorine 'C' oil which facilitates the working of the unit. The cork washer should not be less than .187" in thickness. The new springs incorporated are :- D.51545 - Engagement spring. D.51546 - Disengaging spring. D.51544 - Damping spring. | ||