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 to a supplier regarding complaints and specification ambiguity for calorstats.
| Identifier | ExFiles\Box 156\2\ scan0139 | |
| Date | 6th October 1938 | |
| 1328 EXPERIMENTAL DEPARTMENT. Rm{William Robotham - Chief Engineer}/Std.4/JH. 6th October, 1938. Messrs. S. Smith & Sons Ltd., Cricklewood works, LONDON.N.W.2. For the attention of Mr. Eckford. Dear Sirs, The writer has had some complaints of incorrectly set calorstats supplied by you and on investigating this, has discovered one or two facts which do not quite make sense. In the first place the drawings of these calorstats E.80893, EB.346 and E.87157 specify the temperature conditions as follows "The calorstat stem should start to move when a temperature of 75°C ± 1 is reached and give the full .425" travel unloaded, also from the inner stop where a temperature of 90° is reached, the stem should move a load of 27½ lbs ± 2 lbs. It will be seen that the first paragraph of this specification is not very clear, since it does not specify at what temperature the stem is to have travelled .425" unloaded. Further we find that our production inspection people here have taken it to read that the calorstat stem must have completed its full .425" movement unloaded by the time the calorstat temperature has reached 75°C, and are checking and passing units on that basis. Since they are returning very few new calorstats as defective and we have checked one or two new units to agree with this, it follows that you have put the same interpretation on the temperature specification as on our drawings. Will you please confirm that this is so i.e. let the writer know the precise temperatures which you work to in setting these units - we will then alter our drawing to indicate clearly what is required. | ||