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).
Extract from a report on the characteristics and calibration of carbon-resistance and 'Ess-strip' strain pick-ups.
| Identifier | ExFiles\Box 168b\1\ img168 | |
| Date | 13th February 1939 guessed | |
| Extract from "Report National Advisory Committee for Aeronautics" (page 38). "A second type of strain pick-up on which "considerable work was done at the Bureau is the strain "pick-up of the carbon-resistance type developed by "A.V. de-Forest. Static and dynamic calibrations were "made on 20 carbon resistance strips, 5 of them of the "granular" type used at the Hamilton Standard Propeller "Company, and the remaining 15 of the so-called "Ess-strip" "type. A report describing the results of these tests in "detail has been forwarded to the Bureau of Aeronautics "of the Navy Department. The report gives quantitative "results for the effect of frequency, strain amplitude, "time under load, and temperature on the calibration of a "number of these strain pick-ups. "The best dynamic characteristics were found for the "gages of the "Ess-strip" type. These gages showed a "resistance amplitude that was nearly proportional to the "strain amplitude up to strains of 0.001 (corresponding to "stresses of about 10,000 pounds per square inch in "aluminium alloy). The calibration factor calculated by "dividing the constant of proportionality by the direct- "current resistance of the gage was independent of "frequency between 30 and 100 cycles per second within "± 10 per cent, independent of temperature between -10°C. "and 40°C. within ±10 per cent, independent of time for "one day within ± 5 per cent and for 40 days within "±9 per cent. | ||