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).
Cost comparison between die casting and sand casting for the Wraith III gearbox, part number GW.1890.
| Identifier | ExFiles\Box 148\5\ scan0399 | |
| Date | 3rd August 1938 | |
| RHC{R. H. Coverley - Production Engineer}/JWW.1/HM.{Capt. W. Hallam - Head Repairs}3.8.38. Wraith III. We have been investigating the major die castings that can be produced on Wraith III, and we append herewith a preview of the situation. This preview indicates the prime savings that can be traced by this Department. A comparison is first shown of moulding and die casting times, and then the total cost of castings in different classes of material. Against the tool expenditure is indicated the approximate date of die completion and the number of castings that must be produced to balance this charge. These savings are based primarily on the difference in direct Foundry charges. No use has been made of the reduced times that will come into line in machining, inspection, etc., the reduction of scrap and the elimination of hand filing, scratch brushing, matching with covers etc. The matter of pattern equipment cost and pattern maintenance is being investigated and these charges will be compared with the die charges, which will enable us to give a further reduced quantity of castings to defray the expenditure on the die. As a matter of interest we are obtaining check quotations on all these pieces from outside suppliers. These details will then be incorporated in the second review that will be forwarded of this proposition together with the above mentioned saving on pattern charges, etc. Gear Box, Part No. GW.1890. Die Casting Costs. Direct Labour. Core-making 8 Hrs. Casting 1 " Fettling 1½ " ------------- 10½ " Labour Cost @ .8s per hour = 8.4 shlgs. Sand Costs. Direct Labour. Moulding ) Core-making) 19 Hrs. Fettling ) ------------- 19 Hrs. Labour Cost @ .8s per hour = 15.2 shlgs. Labour Cost Saving = 6.8 shlgs. Material: Die cast weight = 21 lbs. Die Cast Saving = 1.75 lbs. Material. Sand Cast Weight = 22.75 lbs. Total Saving as a % A.RR50 @ 1/3d per lb = 10/9d. = 22% B.ACM @ 5d per lb = 25/8d = 60% C."L8" @ 7½d per lb = 23/- = 53% Total Cost. Material = 28.4 shlg (No oncost) Labour = 15.2 " ------------- 43.6 " 1. | ||