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© Gary Keeling 2004 - 2008 All images and content are copyrighted © by their respective owners/creators. |
Letter from PV
1st August 1950
Dear Rollie, As before we only had a short 1,600 yard aerodrome runway to use, but in this space the machine, running on a 3.1 to 1 gear, easily reached 135 before being changed into top and then proceeded to accelerate very hard in top gear before it had to be cut. The tester, who is very experienced with our “Black Lightning” models, formed the opinion that the machine was very definitely considerably under-geared and would pull a very much higher gear quite satisfactorily. Since the engine appeared to be developing its main power at over 6,000 R.P.M. , when a distinct megaphone effect became apparent in the higher revolution range in the form of a greatly increased surge of power, we have little doubt that this machine is capable of traveling very much faster than the last one which we sent to you. At this point I must interject a very serious note of warning because we have fitted our latest type of cylinder heads and carburettors and large inlet valves as used in the single cylinder T.T. models this year, but due to the fact that we have had no chance to carry out the necessary experiments with a twin cylinder model, we have not dared to fit our newly designed big end which will stand almost unlimited revolutions from the engine. A failure of the crankpin at very high speeds was too dangerous to be contemplated, so we have had to play safe and fit the same type roller big end as you had on the other machine and as we fit as standard to all models. This big end, wilst very good at all usual speeds has a very short life at speeds over 6,400 R.P.M. It is therefore essential that you should gear the machine so that you will not exceed 6,400 R.P.M. on top gear, and that you should watch your tachometer and change up in plenty of time before the danger mark is reached. The change over to the new type big end when we have had an opportunity to test and prove its security in the twin cylinder engine, is relatively simple for any precision machine shop, and we hope in due course to be able to send you the necessary new crankpin parts, together with a drawing showing the necessary alterations to your flywheels so that by next year you can have the machine equipped with the new type big end. We shall be shipping the machine through our usual Shippers, Messrs. Morison Pollexfen & Blair Ltd. , 90, Fenchurch Street, London, E.C.3., and the transit forward from New York will be handled by their New York Office, Messrs, J.J. Murphy & Co. Inc., South Ferry Bldgs, 44, Whitehall St. No doubt Mickey already knows quite well their Broker in Los Angeles. The machine has not yet actually left the works but we are hoping to have it away within the next two or three days. There is one other word of warning I must utter, this being that these special cylinder heads fitted for the sprint mile are still in the experimental stage and we cannot rely on an exhuast valve life greater than about 250 to 300 miles. This is a matter that is under going investigation at present, but time has been too short to arrive at any conclusion due to the extreme pressure on all departments of our business at present. The machine has already covered some 125 miles or more on test but, of course, most of this has not been at racing speed. you should therefore be perfectly safe for at least another 120 miles before running any risk of valve trouble, but meanwhile we are having two more valves prepared and hope to pass these foward to you within the next few days so that should you have to carry out a great deal of practice you can change them before you run into trouble. For any duration records that you may decide to attempt we are enclosing two standard type “Black Lightning” heads and two smaller, standard size, carburettors, and these must be substituted for any appreciable distance runs. For this purpose, of course, they will be more than adequate since you will be running at very much lower speeds. I am writing to-day to the A.C.U. to ask what progress is being made regarding the permit for the A.A.A. to check your record attempt. I am very sorry for the delay that has arisen but we have been simply swamped with work. Sales output and deliveries are breaking all records and there are so many special parts that have had to be made for this machine that the toolroom, which is already overburdened with work, took longer than was expected. However, it is now, as mentioned earlier, complete, and I trust that it will arrive quite safely in time, and that every success will attend your efforts.
Wishing you the very best of luck, For THE VINCENT H.R.D. COMPANY, LTD. p.s. The machine is being crated with sprockets that give a high gear of 2.43 to 1 also alternative sprockets for lower gears. |