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).
Letter discussing connecting rod design, materials, and production considerations.
| Identifier | ExFiles\Box 170\1\ img055 | |
| Date | 18th January 1939 | |
| Continuation of letter to :- W. A.{Mr Adams} Robotham, Esq. Page 3. 18/1/39. We have reduced the connecting rod bolt stresses from 30,800 lbs. per sq. in. to 24,200 lbs. per sq.in. at 5,000 R.P.M. We suggest that you run the gudgeon pins straight in the aluminium without small end bushes. The type of countersunk screw we show for the big end bolts has been used successfully on aluminium connecting rods for the Lagonda and elsewhere. Its object is to reduce the stress concentration round the head of the bolt. We have transferred the dowel to the steel bottom half to avoid the tendency to crack which would be present in the aluminium. As I think I explained to you before, I do not recommend an all-aluminium connecting rod and cap, as in my experience there is some difficulty in preventing rattle of the big ends at light throttle when the engine is hot. Whilst this rod is not so strong as your present steel one, we think it amply strong for the job you have in hand. It may be necessary for you to cut or cast slots in the bottom ends of the cylinder bores to miss the shoulders of the connecting rods. I am having estimates prepared of the cost of the dies and the probable cost of the stampings, and will let you have these as soon as possible. The connecting rods we can price with some certainty from experience, but the pistons are rather more difficult as we have no experience yet on production processes and equipment for pressing these pistons. Cont'd ... ... ... - 3 - | ||