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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).
Modifications to front spring designs for Australian road conditions.

Identifier  ExFiles\Box 67a\1\  scan0286
Date  18th March 1927
  
x8410

Whr.{Mr Wheeler}

Ptl/WP.18.3.27.

Re: Springing

So far as springing for Australian road conditions is concerned I honestly think that it is not so much strength of springs that matters as the need for a spring of entirely different design to that which we have been accustomed to fitting.

I do not think that I can express my views better than by telling you of my experience some three or four years ago, when there was an epidemic of main leaf breakages of front springs fitted to "Silver Ghost" models in Australia, when I was at my wits end to counteract this trouble and gave considerable thought to the matter, culminating in experiments I will endeavour to describe.

The ultimate result was that I took a front spring of approximately the same strength as is standard for a given load for English road conditions, and having opened this spring up I set up the initial camber so as to give a ½" of increased positive camber when the spring was underload, that is when it was supporting the weight of the car and passengers. The object of setting up to obtain this extra ½" on bumper clearance will be explained later. I then had two extra plates made, the first being of the same length as the first supporting leaf under the main leaf and the second being the same length as the second supporting leaf of the main spring. These two leaves had projecting eyes forged at their extremities, drilled for the attaching of 'U' bolts and had very little 'snap' or 'draw' on them over and above the ½" positive camber of the main leaf of the loaded spring, that is to say their initial camber was only in the neighbourhood of ¾". The two leaves were then fitted above the main leaf of the spring and longer spring clips were fitted. This increased the overall depth of the spring by roughly ½" and would have decreased the bumper clearance by the same amount had I not set up the spring ½" as described above.

Small 'U' bolts were then used to anchor the longer of the two rebound leaves to the first supporting leaf of the main spring. These 'U' clips being provided with shoulders to enable same to be pulled up tight against the underside of the eyes of the rebound leaves just short of being tight on the lower leaf so that a feeler gauge could be passed between the upper face of the 'U' clip and the lower face of the supporting leaf, thus preventing the anchorage being sufficiently tight to set up excessive friction between leaf surfaces. The same procedure was followed with the shorter of the two rebound leaves which was anchored similarly to the second supporting leaf of the main spring.

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