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).
Kestrel connecting rod failure, comparing the performance of lead bronze and white metal bearings.
| Identifier | ExFiles\Box 179b\3\ img149 | |
| Date | 6th February 1933 | |
| γ ORIGINAL To R.{Sir Henry Royce} From Hs.{Lord Ernest Hives - Chair} c. to Sg.{Arthur F. Sidgreaves - MD} Wor.{Arthur Wormald - General Works Manager} c. to Rg.{Mr Rowledge} By.{R.W. Bailey - Chief Engineer} c. to S. Hs.{Lord Ernest Hives - Chair}2/WJ.6.2.33. X3859 X4117 KESTREL CONNECTING ROD FAILURE. You will see from the attached report that we have had a connecting rod failure on the Goshawk 1 type articulated rods. We were attempting to run a similar test to that which we completed a short time ago on the present standard rods with lead bronze bearings. The bearing which failed was No.2, which is the number which has frequently failed. When we were doing a high power test some weeks ago on the Standard engine with white metal bearings we smashed up No.2 connecting rods due to the bearing going. At the time we assumed it was the bearing block which cracked first which caused the bearing to go. In view of the recent experience however we should say that it was the bearing running out which was the chief cause of the failure. These tests confirm that there is a risk of bearing failures apart from any aerobatics. We think it is probable that the aerobatics are the last straw which causes the collapse. We are gaining a lot of confidence with lead bronze bearings. We are coming to the conclusion that in the case of the seizure or a run out bearing it is much safer than white metal. What happens is that when the lead bronze bearing becomes over-heated the lead runs out, this protects the shaft. After the lead has run out there is then an increase in clearance, but the copper is still adhering to the bearing shell and this is much kinder to the shaft than in the case of a white metal bearing which runs out and leaves steel against steel. In the case the other day where the big end bearing went on a hardened shaft no damage at all was done to the shaft and no damage to the rod. The fact that we have had lead bronze bearings fail on articulated rod confirms the point that none of the modifications in hand with modified rods and types of bearings are going to overcome the epidemic which we have recently had. It is certain that it is the lubrication side which is causing these failures. Hs.{Lord Ernest Hives - Chair} Att: Hs{Lord Ernest Hives - Chair}/Pmr.3/WJ.6.2.33. | ||