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).
Tests conducted on a 20-HP vehicle regarding issues with rear engine mounting, frame jellying, and carburettor performance at different water temperatures.
| Identifier | ExFiles\Box 5a\2\ 02-page053 | |
| Date | 22th January 1929 | |
| To: Hs.{Lord Ernest Hives - Chair} From: G.W.H. X5840c Hotel de France, Chateauroux, Indre. January 22nd. 1929. We have been carrying out tests to-day on the 20-HP. Firstly we found that the rear engine mounting was too flexible. We tightened up the centre bolt approximately 6 full turns of the nut which as far as we can see compresses the rubber blocks. The results on the road was the engine movement at the rear was considerably reduced. We have not got a drawing of the rear engine suspension and cannot see exactly how it is mounted. We know that there are special soft rubber blocks that have been fitted, and it would appear that they are too flexible for the rear mounting, especially as it is a 3 points suspension. We have been carrying out further tests on the jellying of the front, the tests carried out have been in the following order: Firstly we disconnected the front shock dampers, slacked off the torque reaction dampers and ran with tyre pressures 35 lbs. all round. Under these conditions the jellying of the front is very bad. The steering is very much inclined to wobble, but does not do so. Secondly we coupled up the shock dampers. This gives about 20% improved non-jellying of the front. Thirdly we tightened up the torque reaction dampers choc-a-bloc. This made the biggest improvement we should say 50%. We have tried to observe where the frame starts jellying, but cannot see anything definite. It gives the appearance that the base of the movement is somewhere midway between the cross in the frame and the rear engine supports, but as stated it is very difficult to locate riding on the front of the car. We did notice however that the whole frame rides as if it was pivoted in the centre, and as the front jellies so it is transmitted vice-versa to the rear. It would appear from our tests that the most important part of the frame to hold solid is as near the front dumb irons as possible, and the rear to be strongly embraced. We also carried out tests this morning of starting the engine up from dead cold. With the carburetter reset as stated yesterday, the engine starts up readily and can be opened up fairly quickly with mixture strong. The chief trouble that is experienced with the water-heated throttle is that whilst you are running on the road the carburation is considerably affected by the water temperature. For example, if you are running with a water temperature of 85°C, you can with the mixture lever normal, accelerate up from low speeds and generally the carburation is right, but if the temperature drops to 65°C. and the speed of the car is reduced, you immediately get the firing-back in the carburetter and the engine will not accelerate. To get away without any blow-back under this condition it is necessary to run in full strong position. This is a feature that is met with considerably during any tour, and from the results we say that the water heated throttle is not satisfactory, without it is definitely pointed out to the owner that he must keep the water temperature up to 85°C. | ||