Regaining the Twenty-four Hours World’s Record for Great Britain.
By CAPTAIN JOHN F. DUFF.
IONG distance endurance trials and record breaking 4 runs have occupied my attention since I disposed of my two racing Fiats in 1922. These cars were extremely fast, but not suitable for long distance work.
It was the result of a conversation with Mr. Hillstead, of Bentley Motors, Ltd., during the course of which he enthused about the staying powers of the Bentley car, that I conceived the idea of going for the ” doubletwelve” record, at that time the accepted ” Supreme Test” of endurance. This first departure into a new form of Motor Racing work appealed to me, and I decided that it was more interesting, as well as more useful, to work with standard (or near standard) cars, and carry out performances which tested every part to the uttermost. I found also that one can obtain more useful and practical knowledge concerning the ordinary touring car in these events than when handling specially built racers, which bear little resemblance to the utility car. During the last couple of years I have competed in several 24 hours road races with varying success.
The high average speed established by the Renault at Montlhery, for 24 hours, drew my attention to this track as a likely place to improve on the figures I had established in the ” double-twelve ” world’s record in 1922.
Remembering at the same time, Le Mans, where I had made a very poor show, owing to a most trivial error of calculation, and feeling that I would not like the 1925 season to close without having one more try at accomplishing something worth while, I decided to go for the World’s 24 hours record on the Montlhery track.
A Question of Mathematics.
Assuming a degree of reliability permitting a car to be run at its maximum speed for twenty-four hours on end, record breaking becomes a matter of mathematical calculation, in which engine revs., gear ratios, lap measurements, wind resistance and numerous other factors play an important part. One result of thy calculations was to convince me that a 3 to 1 rear axle ratio would be needed in place of the ordinary 3.7 to 1 fitted as standard.
As a matter of fact, I had calculated that with my 1926 Speed Model Bentley it would be possible to improve the Renault figures and my intention of doing the twenty-four hours run at an average speed of 95 m.p.h. was announced before the start. The actual speed worked out at 95.02, which proves that the calculations were not far out.
CAPT. Duvr’s BaNTI,Ev WHICH WON THE 24-HOURS RECORD.
Details of the Car.
Of the actual performances on the track there is little to excite the interest of my readers, but I will endeavour to recount such as occur to me in looking back over the event. The car used was my own Bentley, the only alterations being the fitting of two Solex carburettors and Splitdorf magnetos. Weymanns, in Paris, built me a rather special fabric covered body, the whole job, including the preparation of the working drawings, being completed in fourteen days. That is rather a remarkable achievement in body building. In addition to being very light, the body answered just as well as any in which the best metal work construction is used and, I think, explodes any idea that graceful curves are impossible with Weyrnann construction.
Pit Organisation and Drill.
If calculations play an important part in record breaking attempts so does organisation, for unless these details are studied closely the best car in the world would not be likely to succeed in gaining any long distance laurels on the track. Therefore, I took the trouble to Prepare special gear for the petrol and oil filling, supervising every detail of its erection. The pits were also arranged to cope with any unforeseen adjustment that might be needed during the run ; but the trip of September 21st was absolutely uneventful, perhaps disappointingly so from the description point of view, but happily so as far as its objective was concerned. If a slow motion film had been taken of my pit attendants at work in replenishing the car during the stops when Barnato and I changed over, it would have
been rather interesting. For several days prior to the attempt I rehearsed all the process of replenishing the car ” by numbers,” to use a military expression. Each man not only had his particular part of the process to perform, but his every movement was made according to plan. It was rather fun drilling the French mechanics in this way, but they became quite enthusiastic in their efforts to beat the stop watch, with the result that on the record run our longest stop was I min. 40 secs., and most of them about 1 mm. 10 secs.
Baulked on the First Attempt.
The entire organisation was completed in time to start at 7 p.m. on the 9th September, when together with Dr. J. D. Benj afield, the well-known amateur Bentley driver, I started on the first attempt. Talking of three hours each, the Doctor and I took world’s records for 1,000 kilos. in 6 hrs. 23 mins. 31 secs., and the 1,000 miles in 10 hrs. 15 mins. 27 secs. After running with the greatest regularity for 18 hours the engine gave a curious exhaust note for about ten minutes and finally a dismal splutter and stopped. We immediately tore off the valve gear cover, and passing on to the forward engine gears, found that a tooth had broken from the bevel drive at the lower end of the vertical shaft driving the cam shaft. Owing to the inaccessibility of the broken gear the attempt had to be abandoned. Prior to this mishap two turns of three hours each were covered at the remarkable speed of 100.01 m.p.h.
After dismantling the engine and fitting a replacement the car was ready for another try, but Dr. Benjafield was unable to get away from his professional duties, and so Capt. Woolf Barnato was asked to deputise, and gladly consented.
At 6.32 p.m. on the 21st September, we set off again. At the end of six hours a thick mist arose, which gradually became denser until it was impossible to see more than 200 yards ahead. Nevertheless, the average speed was not permitted to drop below that agreed upon at the commencement, although we were only dependent upon the faint lights on the edge of the track for guidance. When daylight came the track was damp and a wind blew across the track, which did not help matters.
The car continued to run smoothly and during the course of the run captured no fewer than twenty-two world’s records. To maintain our average the speed sometimes reached 98 m.p.h. for long intervals, By driving within the maximum speed we had a reserve, should any stops for adjustments have become necessary, but as it happened there was no need to lift the bonnet, a certificate to this effect being given by the Automobile Club de France, whose officials did the timing throughout.
The engine never missed once and the exhaust droned without the least variation of tone until at 6.32 p.m. on Tuesday, September 22nd, when the car was stopped, having covered 2,280 miles in 24 hours at an average speed of 95.026 m.p.h. in twenty-four hours, a World’s record for any size of engine.
Among the spectators who witnessed the attempt were the holders, Messrs. Garfield and Plessier, the Renault drivers, and some members of the Voisin team. The latter made an unsuccessful attempt a few days
later to reduce the Bentley figures. These gentlemen followed the proceedings in a very sporting spirit and were enthusiastic in their congratulations for Capt. Barnato and myself.
Impressions of the Run.
The outstanding feature of the trip was the extreme monotony of driving and the entire absence of incident. The track is much faster and easier than the Brooklands course, higher speeds being possible owing to the absence of gradient such as that from Vickers’ sheds’up to the Members’ bridge. No trouble whatever was experienced with the Dunlop Tyres which ran for the whole distance with only a single change and the K.L.G. plugs certainly deserve several medals, not a single miss being noticed throughout the run.
It is safe to assume that further attempts will be made on this coveted trophy, and in my opinion this record will not be long lived till it has reached the 100 m.p.h. average.
The excellence of the track at Montlhery, and the increasing reliability of the modern car combine to make it necessary for us to reconsider our ideas of speed for long distances.
The figures established by Capt. Bamato and myself were well within our limit, a good reserve being constantly in hand. I was content to put 7 m.p.h. on the existing record to be fairly certain of having no trouble. It is my belief that had we aimed at higher speed, sax 98 or even 100 m.p.h. average, the chances of the car standing up would have been quite good, though I did not consider it wise to force matters unnecessarily, one must always have a bit in hand with which to retaliate when some sporting competitor betters one’s existing figures !