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).
Design and manufacturing process for front and rear dumb irons on the 'Goshawk II'.
| Identifier | WestWitteringFiles\F\January1921\ Scan78 | |
| Date | 28th January 1921 | |
| To E.F.G. from R.C.W. JAN 29 1922 E.F.G. REC'D X.4060 ORIGINAL. RE FRONT AND REAR DUMB IRONS - "GOSHAWK II". N. SCHEME 689. Referring to the above, we send you herewith drawing No. 39 showing how Mr. Royce would like the front dumb iron made. The stem portion of the dumb irons should be drop forged solid and then roughed out with a large milling cutter, and the inner profile shown, finished with an end-mill. This scheme allows the dumb irons to have a channel section which can be rivetted as shewn, to the channel section of the frame. The corners of the dumb irons need not fit the corners of the frame, but can be chamfered away with a cutter, or shaped away in the forging. We think it is just possible to get the rivets in at the front end. This drawing gives you more exact particulars of the shape of the front end of the frame and front spring. The front spring has 1/4" camber, and with the link at the rear having 1 1/2" centres, and with the usual "U" bolts and clamping plate, the metal to metal bump is 3.250. Mr. Royce, however, wishes to use a special form of clamp for holding the front spring, which will prevent parallelogramming of the leaves consisting of an inverted "U" box having bolt bosses in the sides and secured to the axle by four bolts. The box engages with the spring bolt head at the top and the bolt stems at the bottom acting in shear, prevent the parallelogramming action. [Handwritten Note with Sketch] RUBBER STRIKES IN CENTRE OF BOX BETWEEN BOLT HEADS BUT BOLTS CAN HAVE COUNTERSUNK HEADS IF NECESSARY [Stamp] Da.{Bernard Day - Chassis Design} JAN 28 1921 RECEIVED | ||