Rolls-Royce Archives
         « Prev  Box Series  Next »        

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).
Suspension modifications and a novel method for measuring rear-seat ride comfort.

Identifier  ExFiles\Box 72\2\  scan0041
Date  28th August 1926 guessed
  
- 2 -

in most cases been arrived at on cars fitted with high pressure tyres, Hartford Shock Absorbers at rear and R.R. old type friction shock absorbers at front, and I find that when one comes to the later type cars with low pressure tyres and with hydraulics at the front these percentages need modification approaching to plus a percentage of 5 for front and minus a percentage of 30 for rear springs. This is partly due to the fact that the FWBs have already sent up front spring poundages.

The above remarks apply only to 40/50 H.P. cars. We have cars out here used regularly on the city streets, about which we have not had any complaints, sprung as lightly as no added percentage to front springs and less 35% for rear springs by the above method of calculation, while we have the other extreme in the case of a light sporting bodied car used regularly at high speeds over rough roads where the calculation works out as plus 20% for the front and minus 2½% for the rear.

I think that for the present if you can get Test Department to accept plus 10% for front and minus 20% for rear we should get excellent results, and I have every hope that, with the adoption of low pressure tyres and hydraulic shock absorbers allround together with the recent marked improvement in Australian roads and the expected improvement in weight distribution in the near future, we shall gradually tend towards lighter springing approximating to that acceptable in England.

Our biggest troubles recently have been with the 20 H.P. car upon which the stiffer type springs with reduced bump clearance have not been a success. The crying need here on the 20 H.P. is a somewhat increase in bump clearance particularly at the front where I consider anything under 3" to be useless.

I endeavoured to arrive at something definite in the way of comparative figures in the matter of actually measuring the discomfort on the rear seat of the various cars, which I did as follows:--

I arranged a cylindrical sheet metal vessel to hold one gallon measuring 11-3/16" deep and 5-15/16" in internal diameter and sweated to the base of same and concentric with its walls another cylindrical vessel having a depth of 7-1/16" and an internal diameter of 2½" with a capacity of one pint. This gadget I screwed down upon a piece of board so arranged that a passenger could sit upon same in the centre of the rear seat board with cushion removed and having the vessel gripped vertically between his thighs. The inner vessel was filled with water carefully measured in c.c. and was provided with a lid{A. J. Lidsey} which was a snug fit but quite easy to remove. I then took the car over a piece of rough road and at a predetermined point the lid{A. J. Lidsey} was snatched off, permitting bumps of car to displace water from the inner vessel into the outer one. At another predetermined point the lid{A. J. Lidsey} was replaced and the car slowed down, stopped and the amount of water displaced carefully measured. The same test
  
  


Copyright Sustain 2025, All Rights Reserved.    whatever is rightly done, however humble, is noble
An unhandled error has occurred. Reload 🗙