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).
Letter from Cambridge Instrument Company regarding the failure of a dial thermometer's electrical contacts due to excessive current.
| Identifier | ExFiles\Box 175\4\ img068 | |
| Date | 12th August 1927 | |
| TELEGRAMS: INSTRUMENT, CAMBRIDGE. CODES: A.B.C. (5TH AND 6TH EDITIONS); WESTERN UNION: BENTLEY'S. TELEPHONE: CAMBRIDGE No. 615. CAMBRIDGE INSTRUMENT COMPANY, LIMITED, HEAD OFFICE AND SHOWROOMS: 45, GROSVENOR PLACE, LONDON, S.W.1. WORKS: LONDON AND CAMBRIDGE. MANUFACTURERS OF MECHANICAL & ELECTRICAL INSTRUMENTS OF PRECISION. REGD. TRADE MARK. YOUR REF............... Hs{Lord Ernest Hives - Chair}/Rm{William Robotham - Chief Engineer}4/LG. CAMBRIDGE, ENGLAND. IN REPLY PLEASE QUOTE WGC/MV 12th August, 1927. Messrs Rolls-Royce, Ltd, Derby. Dear Sirs, Dial Thermometer with Electrical Contacts. We acknowledge receipt of your letter of the 10th instant, and note that you feel the construction of the contact portion of this instrument is not sufficiently robust. On careful examination of this contact, however, we find that it has had a very heavy current passed through it, certainly not less than 3 amperes, whereas in our letter of May 31st, 1926, we stated it was not safe to pass a current exceeding half an ampere through the contact. The platinum has been fused completely asunder at one point and has run up in globules. It is, therefore, quite impossible to meet your conditions of making but little effect on the last divisions on the scale if this contact be made so heavy as to carry several amperes without fusing or damage. Moreover, we think it is almost impossible to construct a contact for use under such conditions to carry such a heavy current that shall last for any appreciable length of time. In the meantime we should be glad to have your further remarks on precisely what results you require and in what way you suggest the design can be altered to improve the instrument. We are | ||