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).
Investigation into the failure of Lucas Wind Tone Horns due to moisture and dirt.
| Identifier | ExFiles\Box 83\4\ scan0238 | |
| Date | 10th June 1936 | |
| GWH{George W. Hancock - Head Chateauroux}/HFH{Hoppy F. Hamilton}/4/JAB. 10.6.36. To. Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} c to. Sg.{Arthur F. Sidgreaves - MD} c to. [REDACTED] c to. [REDACTED] LUCAS WIND TONE HORNS on B. 56. BN.{W.O. Bentley / Mr Barrington} It has been suspected that wet and foggy weather contribute to the temporary failure of these horns on the road, and tests have been carried out to find if the application of moisture could produce a failure. The horns in question were removed from B.56.BN.{W.O. Bentley / Mr Barrington} and fitted up on a stand, coupled to a battery & switch. They were then subjected to an artificial spray for periods of 10-15 minutes at a time. Contact was then made, and the low frequency horns more often than not failed to operate, but if tapped by hand started to work. This was then replaced by a new one and the same test carried out, neither horn failed. Considerable dirt was found inside the trumpet tube in the nature of mud, flies, etc., this was removed and the inside of the tube cleaned. Again the test was carried out, but this time no failure occurred. The same horn was then put on a car and run at speed into the face of a hard rain storm, only very occasionally did the horns show signs of failure. The following is a suggested explanation :- Rain & fog collect in the mouth of the trumpet and is blown right down to the narrow part of the tubing. Here it collects and forms a wall, and as these horns are dependent on the displacement of air in the tube, no sound is made. If however, the horn is tapped by hand, the wall of water is broken down and the horn again operates. It has been found that both high & low frequency horns fail on occasions, it is suggested that on these occasions the air vibrations are not sufficient to brake down the wall of water. Horns fail more frequently after the car has done considerable mileage, the reason being that dirt driven in by wind & rain collects inside in lumps and assist the water in building up, whereas a smooth surface allows the water to flow away and eliminate choking. If however, these horns are driven at speed into a rain storm, the force of wind is sufficient to hold up the water no matter how clean the inside of the trumpet & tube may be. This will only happen under very severe conditions. A further indication of the probability of the foregoing remarks, is that the same trouble occurs in snow when | ||