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 failure of a coil on chassis 3-PP, discussing potential causes related to earthing and insulation.
| Identifier | ExFiles\Box 46\3\ Scan174 | |
| Date | 2nd March 1920 | |
| X.3445. BY.{R.W. Bailey - Chief Engineer} FROM EF. c. to Sir H.{Arthur M. Hanbury - Head Complaints} c. to Mr.Brock. c. to CK.{Mr Clark} EP{G. Eric Platford - Chief Quality Engineer}14/F2.3.20. X.3445 RE. FAILURE OF COIL ON CHASSIS 3-PP. X.3716. I was pleased to receive copy of Mr.Brock's report on the above, which has caused me to be alarmed in so far as I foresee other cars giving trouble after delivery with a similar failure. You will remember that I have in the past had occasion to return to the works several coils, owing to the earthing which took place between the ballast resistance and its aluminium cage, and although when the car came on test they seemed quite satisfactory in this respect, the shorting evidently developed whilst the coil was in use during the testing of the car. It is quite possible, therefore, that these shorts may continue to take place after the car is delivered. With regard to the coil being tampered with, I quite appreciate that this can take place even after the car has been delivered, as whatever has failed, you can rest assured this has taken place after delivery, as our final check of the car is to check that the current taken by the coil at 12 volts with the make and break not moving, does not exceed 4 amperes (starting up cold usually about 3 1/2, and settles down to about 2 1/2). We must appreciate, however, that a certain amount of dismantling of external parts will take place on our cars when in the hands of ordinary drivers, and if this ordinary handling is going to cause such failures as this, it is doubly certain that some better scheme is required so that such complete failure cannot take place so easily. The chief weakness I consider in this coil is that the insulation of the ballast resistance is not sufficiently sound and satisfactory, and in view of the above experience, I bring this point forward to you and CK.{Mr Clark} for consideration re. improvement in this respect. In the meantime, it seems absolutely essential that the insulation of this ballast resistance to the frame, etc. should be a point of very careful inspection by the works before the coils are passed as being satisfactory for delivery. The actual test I do not think good enough. What must be done is to make sure that the ballast coil itself has ample clearance between it and the cage, since the vibration and heat to which it is subjected whilst on the car will soon | ||