Wilmott Breedon Front Bumper

Steve Welton · Joined: 17 Oct 2013 Posts: 105

I have a Wilmot-Breedon front bumper fitted to my 1935 3 1/2 L .
Thumbing through the technical manual I read that in 1936, following an accident, RR issued a depot sheet recommending safety straps be retrospectively fitted. My CW series car was not modified with one of these.
The mod looks quite big with a saddle and a hole through the apron.

Does anyone know how the bumper caused the accident?
If the lack of the modification is "dangerous" then is there any other way of making the car safe?

I guess the latter would be answered if I knew what the origin of the original weakness/problem.

Christopher Carnley · Posted: Thu Nov 24, 2016 11:37 am Post subject:

The story goes that R-R were testing the 4 1/4 litre prototype, one end of the blade broke away and was trapped under the front wheels. Something broke and the car tipped end over end, all escaped including the diminutive Jack Barclay, formerly a racing drive.

The one pictured is not exactly the Bentley type but shows the principle.

The "bumper" was not intended to be a bumper but a means to damp down the shimmy and tramp from the early chassis which on production had additional strengthening fitted across both the front and below the front engine mountings. The tuned blade then proved to have no real function except as a bumper.

Steve Welton · Joined: 17 Oct 2013 Posts: 105

Christopher,
Many thanks for the information you have provided.

This is consistent with information from down under.

"NZ Rolls Royce and Bentley Club Magazine Issue 08-6, 2008
Front end shake or shimmy was a problem, and a jig was set up to measure this on 1-B-IV. A solution was seen in the installation of a Wilmot Breeden harmonic stabiliser bumper with a lowered front chassis cross member. This bumper was fitted to 4-B-IV, which had been re-bodied as a Park Ward saloon with a special engine of 6.9:1 compression and larger inlet valves, but during road testing by Willoughby Lappin (Lp) with passengers including Jack Barclay aboard, a mounting bolt broke and one end of the front bumper dropped and was run over by a front wheel. The overload on the front axle caused it to fail outboard of the spring, and the car went end over end. Somehow the occupants were not seriously injured, but to ensure that the accident would never recur, By designed neat hooked arms extending from the chassis to fit loosely around the horizontally mounted bumper spring. Interestingly, Ray Drury’s early Thrupp & Maberly saloon B24AH, delivered in April 1934, and illustrated on page 18 of 085, does not have these hooks fitted. Did this car slip through the retro-fitting process, or did it lose the hooks later in its life?"

I now have a better idea on what happened and possibly what caused the accident. I wonder why RR didn't re-engineer the mounting bolt so that it wouldn't break and why instead "By designed neat hooked arms extending from the chassis to fit loosely around the horizontally mounted bumper spring" I don't think it's neat!

Are there any other known instances of the failure of the mounting bolt?

Christopher Carnley · Posted: Mon Nov 28, 2016 10:08 am Post subject:

From as yet unpublished book of complete chassis details.

The bolt projecting from the front of the chassis frame in p 88 is the one that broke off.

Steve Welton · Joined: 17 Oct 2013 Posts: 105

That makes sense. If that bolt breaks then the bumper hits the deck.
As mine has been on the car so long I think for the time being I will give it both visual check and the occasional wiggle to see that all is okay.

These bumpers were fitted to many different cars I wonder if there is any other history of them coming adrift?