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 cork clutch and starter pinion engagement failures and their resolution.
| Identifier | ExFiles\Box 178\1\ img217 | |
| Date | 24th June 1927 guessed | |
| Cont'd.{John DeLooze - Company Secretary} -2- Hm.{Capt. W. Hallam - Head Repairs}59. Several cases have been found whereby the cork clutch had insufficient friction to convey the inertia of the mass of the unit, and would not run up the thread and so engage. The chief cause of this is the poor co-efficient of friction of the cork. It does not appear to be the effect of too much oil, as the cork discs which failed were to all purposes in a moderately dry condition, similar to others which were O.K. In investigating this we found that the outer spring D.51133 was one of the minimum poundage allowed, i.e. 6 lbs., and by fitting the maximum spring, i.e. 8 lbs., it overcame the slipping and engaged without trouble. The trouble experienced with the false engagement or crashing, i.e., the pinion teeth rubbing on the edge of the flywheel teeth and not engaging, is entirely due to the spring D.51133 being on the weak side. It will be seen by looking at the sketch, that when the pinion unit has climbed the thread as far as the flywheel teeth, when starter motor is in position, it leaves the pinion with a free movement of .250" and is controlled by the load imposed by the spring D.51133. If the spring is on the weak side, the momentum of the unit is such that the pinion fails to engage at the moment that 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 9 1/2 lbs. Therefore we have a force of 2 1/2 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. Cont'd.{John DeLooze - Company Secretary} | ||