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).
Outlining calculations and suggestions to eliminate an exhaust boom on a 25 HP model using a variable double resonance unit.
| Identifier | ExFiles\Box 104\2\ scan0018 | |
| Date | 30th May 1932 | |
| 85230 To Hs{Lord Ernest Hives - Chair}/Lid.{A. J. Lidsey} from Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}2/KT.30.5.32. TO ELIMINATE PERIOD ON 25 H.P. EXHAUST SYSTEM AT 40 M.P.H. Engine speed 2000 r.p.m. Exhaust frequency 6000/min or frequency of 100/sec We assume that the boom is at or near this frequency, and wish to have an easily variable double resonance unit to "bracket" the boom at a sensitive place. Let the size of one chamber be fixed at 150 cubic ins. and its conductivity at .4 Let the conductivity of the second chamber be fixed at .4 Now by varying the volume of the second chamber, the response point of the double unit can be varied. We suggest three sizes of the second chamber, which will give the following three response frequencies:- Vol. of second Response frequencies chamber. cu.ins of the double unit. ---------------- --------------------- 108 cu.ins 105/sec 150 cu.ins 95/sec 180 cu.ins 83/sec In case none of these give the required response, a further frequency can be obtained by reducing the conductivity of the passage to the second chamber to .2 and its volume to 76 cu.ins when a response frequency of 120/sec is obtained. To make the conductivity .2 the pipe connecting the two chambers is altered from 2" of 1.25" O.D. pipe to 4" of .9" dia. pipe. Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} | ||