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 build-up.
| Identifier | ExFiles\Box 166\9\ img006 | |
| Date | 10th June 1936 | |
| COPY. To Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} c. to Sg.{Arthur F. Sidgreaves - MD} c. to E.{Mr Elliott - Chief Engineer} c. to Ev.{Ivan Evernden - coachwork} GWH{George W. Hancock - Head Chateauroux}/HPH/4/JAB.10.6.36. 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 and 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 occured. The same horn was then put on a car and run at speed into the face of a hard storm, only very occasionally did the horns show signs of failure. The following is a suggested explanation :- Rain and fog collect in the mouth of the trumpet and is blown 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 and low frequency horns fail on occasions, it is suggested that on these occasions the air vibrations are not sufficient to break 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 and 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. | ||