-SG- The mid-twenties tuning notes issued by the Norton factory and recently put on this website refer to Alcohol Fuels RD1 and 2, and PMS2. Not everyone may be aware that these fuels were not like the alcohol racing fuels we are used to today which - unless my scant knowledge is already out of date - are primarily methanol based. Thirteen odd years back I put an article together which appeared in the VMCC magazine and which covers the introduction of RD1 etc in the early twenties.
Benzole, Alcohol Fuel and Sir Harry Ricardo.
Those who have even a mild interest in racing activities between the wars will be aware that 50/50 petrol/benzole was the obligatory fuel for any machine with sporting pretensions while alcohol fuels were extensively used at Brooklands and for sprints etc. Sir Harry Ricardo, who is well known for his contribution to the development of the internal combustion engine - and to Triumph enthusiasts for the Vintage Ricardo model - was much involved in the introduction of both fuels, in conjunction with Shell, and a recent history of the Shell organisation by Stephen Howarth, entitled ‘
A Century in Oil,’ gives an interesting insight into the background. Shell International Ltd. has kindly given permission to quote verbatim from this new publication, which was commissioned for the company’s centenary.
“ In the earliest days, Shell Transport’s petrol was made simply by distilling crude oil; Marcus Samuel (founder of Shell) would boast that Shell’s Motor Spirit, unlike those of some other companies, was of such naturally high quality that nothing needed to be added to it. But as engines improved, fuels had to improve too and Shell’s work in this field began in 1917, led by that great engineer Harry Ricardo, whose brilliance later earned him Fellowship of the Royal Society.
In 1917, Ricardo was working for the War Office on the development of engines for tanks and encountered many technical problems. Tanks needed engines which, for the time, were relatively large, producing (on Ricardo’s designs) 150 and later 225 horsepower. These engines had to be simple to maintain and free from both tell-tale exhaust smoke and the danger of stalling on the battlefield.
In combating this, Ricardo concentrated on the phenomenon of what we know know as ‘pinking.’ This occurred when the air/fuel mixture ignited (or as he put it, detonated) prematurely, resulting in a loss of power - a common problem with early tanks, mainly because of the poor quality of fuel. Service fuel supplies were allocated by a War Office committee, so one day, Ricardo presented himself before it to ask for better fuel. But he asked in vain:
'I was given to understand that the best quality petrol was earmarked for aviation; the next best for high-speed staff cars, and the lowest grade for tractors and heavy vehicles, and the Tanks, which only waddled along at walking pace, would have to be content with the dregs of the barrels.'
The committee, composed mainly of senor naval and military officers, was chaired by a civilian, Robert Waley Cohen, by then one of Shell Transport’s directors. Since the committee would not, or could not supply him with better petrol, Ricardo asked for benzole or benzene. He explained that it was more stable and less inclined to detonate than a kerosene-based fuel, so with it, he would be able to increase engine compression ratios, which in turn would provide enhanced power, economy and range. But the committee was still not interested and it was not until after the meeting that Waley Cohen took Ricardo aside and said,’What’s all this stuff about benzole and detonation? I would like to hear more about it.’
Waley Cohen had read chemistry at Cambridge and has sensed there must be something in what Ricardo had said. Over dinner the two men agreed that Shell should send some samples of its different petrols to Ricardo for evaluation. Ricardo found that one of these - from Borneo - could give an engine at least 20% more power - ‘far and away better than all the others,’ he noted. This was so astonishing that he repeated all the tests with another sample of the same fuel, and obtained identical results. Yet what had Shell been doing with it? Burning it as waste, by scores of thousands of barrels, because its specific gravity was deemed too high to be of commercial use. Armed with this revelation, Waley Cohen promptly cabled Borneo to stop the waste and took Ricardo on as a consultant.
So began Shell’s continuing programme of matching fuels to engines and some of Ricardo’s other investigations showed that brilliance can promote both heroism and harmless pleasure, as well as sound business-like products. On his suggestion, Shell’s Borneo petrol was used to make a super aviation fuel. Doing this was costly and quite wasteful, and the product was too scarce for normal aviation use; but it did provide 10% more power from 12-15% less fuel - and it was this fuel which Alcock and Brown used for their pioneering non-stop transatlantic flight in 1919. As Ricardo remarked, they said that even a small increase in power or fuel economy might make all the difference between success and disaster for their enterprise, for it was touch and go whether they could take off with enough fuel for the crossing...
It is easy to imagine the thrill and satisfaction derived from being involved with the success of that historic crossing, and just as easy to understand the enjoyment that came from another of Ricardo’s suggestions. Thinking ‘it might be amusing to concoct a special fuel mixture for racing cars and motor-cycles,’ he put the idea to Robert Waley Cohen, ‘who had no objection; in fact, he, too, thought it would be rather fun.’
From this whim, ‘Shell Racing Spirit’ was developed. It was a blend of ethyl alcohol (supplied by the Distillers Company), benzole, acetone, water and 2% castor oil. The formula was kept confidential, partly because Ricardo wished to patent it and partly because the ‘secret composition’ was a splendid marketing device. But applying for a patent produced a hitch: any competitor could simply analyse the fuel, work out its components and their proportions, and by adjusting these proportions very slightly could make an equally efficient fuel without breaking patent law. Shell Transport’s chief chemist, James Kewley, decided to ‘find some complex organic substance which could both defy analysis and give to the exhaust a peculiar and characteristic smell.’ The answer was to add to the mixture - of all things - a small pinch of finely powdered bone meal!.
It certainly gave the exhaust a distinctive (‘and,’ said Ricardo, ‘I am afraid, a rather repulsive’) odour. It also provoked enormous speculation among competitors, who mostly reckoned a secret wartime development, probably a high explosive, must be involved. Speculation and theories increased when, with Shell’s agreement, the Distillers Company began marketing ‘Discol R,’ a ‘rival fuel,’ - which, in fact, was exactly the same thing but in a differently coloured can. The invented rivalry proved another good marketing device, and Ricardo much enjoyed hearing riders extolling the virtues of one fuel against the other. The deception was an innocent one, because, whatever the can’s colour, the fuel worked outstandingly well: it could produce as much as 30% more power than anything else available. Indeed, with motor-cycles, it was so efficient that after one season of use, in which a Shell-sponsored rider took every prize that was going, the authorities at Brooklands banned it. It cannot be often that a company produces something which is just too good.
After-word: Although the final part of this extract makes a good story, it is not quite a full reflection of the facts! The truth is that alcohol fuels of various types were used at Brooklands throughout the twenties and thirties. What did happen, was that they were banned for use in major UK road races, including the TT, with effect from the end of 1925, although for some now obscure reason, alcohol fuels were permitted again during the thirties in the Manx Grand Prix events. The late Joe Craig expressed the opinion in 1948, that this factor - the banning of alcohol fuels - did much to encourage the development of reliable high performance engines which would run efficiently on petrol - or petrol/benzole.
Writing in 1992, the late Dr. Joe Bayley told me that alcohol was used at Brooklands prior to the Great War, both as a fuel and as an additive. But he went on to say that it was towards the end of the 1922 season that Discol really became popular. RD1 (RD= Racing Discol) was made up of 80% Ethanol, 10% acetone and 10% water. It was mainly used for short races. RD2 was 80% Ethanol, 10% Benzole and 10% Acetone - used mainly for longer races - while PMS2 (Pratt’s Motor Spirit), which JB considered probably the best of the three, was a simple mixture of 80% Ethanol and 20% Benzole. Towards the end of the twenties, Laurence Hartley, the well-known tuner and Ariel exponent, apparently started marketing a racing fuel of his own, based on a very high purity methanol (M100), which gave better results that any of the alcohol fuels mentioned. It was widely used in many branches of motor-cycle sport with much success.
-Simon Grigson, 1999-
Postscript: Roger has kindly been in touch to add some very worthwhile comments. He has carried out considerable research into the matter and this is contained in the relevant section of
his book. He adds:
Discol was the product of the Hammersmith DIStillery Co. Ltd and their January 1923 letter to Motor Cycle must be regarded as authoritative in terms of the meaning of PMS as Power Methylated Spirits and of their composition. They were probably the sole source of supply of the rectified spirit for use in fuels using the Discol name but which were mainly hydrocarbon based in much the same way as modern petrol. I am not sure whether RD1/2 were available before PMS1/2 but certainly the letter confirms that PMS1/2 were available from 1922 and initially contained neither castor oil nor acetone. I suspect that Shell marketed PMS as Shell R and that Ricardo developed RD1/2 with the additives after that. I also thought that RD stood for Ricardo Discol.
The mixtures evolved with time and by the thirties incorporated methanol and acetone. RD2 would have used around 25% benzole which is why the acetone was introduced to maintain miscibility. Methanol tends to absorb water which is why it needs the acetone which would also allow water to be added to give a greater charge cooling effect.
