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).
High-speed vibration issues in the Goshawk 11 engine, focusing on its unique crankcase design and suspected weaknesses.
| Identifier | ExFiles\Box 74\3\ scan0263 | |
| Date | 1st February 1922 | |
| To Hs.{Lord Ernest Hives - Chair} from E.{Mr Elliott - Chief Engineer} X4221 E2/M22, 2. 22. X.4221 X.4220 X.3431. The high speed vibration on the Goshawk 11. seems to be an effect we have not got on any other RR. engine, and it is significant that Goshawk 11. crankcase is different to that on any other RR. engine. It has not got the side stiffening flanges of the Falcon, Eagle, Hawk, and 40/50, and it is not made like the Condor and Goshawk 1, with the main bearings solid in each half. The crankcase as originally arranged by Mr. Royce had a bottom half with vertical webs well attached by stiffening flanges opposite each main bearing with a view that when the 2 halves were bolted together the structure would be as far as possible a beam of box section for resisting side loads. This scheme is not so good as the Condor, but is easier to produce, and more convenient to handle. At Derby's suggestion for facilitating production it was agreed to reduce the webs to two plain ones in the bottom half, but we now fear that has resulted in leaving the crankcase weak sideways. Calculations indicate that there is a live bending moment of 12,000 lbs.ins. in the middle at 3,000 r.p.m. and that the crankcase with a flabby bottom half is overloaded. It might be useful to confirm this with a static test by laying a complete crankcase on its side, supported at each end opposite the front and rear arms, and measuring the deflection with loads increasing to at least 3,000 lbs. (Roughly this is normal load at 3,000 r.p.m. assuming reversal of load multiplies contd:- | ||