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).
Graph showing the results of tests on a Smith's Calorstat, comparing performance with and without a return spring.
| Identifier | ExFiles\Box 39\4\ Scan188 | |
| Date | 9th September 1930 | |
| 9-9-30. SMITH'S CALORSTAT TESTS. LOADS REQ'D TO JUST RAISE SYLPHON FROM BOTTOM OF CASING. AND ALSO TO HOLD BELLOWS AGAINST STOP. NO GUIDE BUSH. WITH RETURN SPRING JUST OPENING WITH RETURN SPRING FULL OPEN RETURN SPRING 19 LBS INITIAL 22 LBS FINAL WITHOUT RETURN SPRING JUST OPENING WITHOUT RETURN SPRING FULL OPEN ROAD TESTS WITH RETURN SPRING SHUTTERS FULL OPEN 72 1/2 °C {65-63} SHUTTERS FULL CLOSED 62 1/2 °C {45-50} RETURN SPRING DELETED PULL LB. PUSH LB. TEMP °C LOAD TO CLOSE SHUTTERS 5 LBS LOAD TO OPEN SHUTTERS 10 LBS | ||