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).
The testing and analysis of a Jaeger Speedometer, type 6193.
| Identifier | ExFiles\Box 165\4\ img023 | |
| Date | 24th July 1928 | |
| X4665 24.7.28. JAEGER SPEEDOMETER TYPE 6193. NO. 513402. It may be assumed that, as in the case of instrument No.516501, the reading is unaffected by temperature. In order to check revolutions per mile of the instrument, it was driven for various periods and the total and trip mileages recorded compared with the recorded (by counter) revolutions of the spindle. In this way the revolutions per mile were found to be 1595 (i.e. 5 x 11 x 29), the total and trip mileages being in agreement. This does not agree with the statement given for instrument No.516501 that correct reading at 1200 r.p.m. is 42.5 miles per hour which corresponds to a revs.per mile of 1200 x 60 / 42.5 = 1694. At 1595 revs. per mile the indicated speed at 600 r.p.m. should be 600 x 60 / 1595 = 22.6 m.p.h. and at 1200 r.p.m. should be 45.2 m.p.h. (Query, is 42.5 an error for this). The actually observed speed indications of this instrument were :- At 600 r.p.m. exactly 21.0 m.p.h., which is slightly low to correspond with 1595 revs.per mile and at 1200 r.p.m. exactly 45.5 m.p.h., which is nearly right to 1595 revs.per mile, but rather high to 1694 revs.per mile. EFC. | ||