Technicalities
TECHNICALITIES
GORDON H. JENNINGS
BRITAIN’S BOFFINS are in a tremendous stir these days. There, as everywhere, it is the bright dream of every motorcycle designer to be permitted a try at building a really advanced Grand Prix road racing machine. Unfortunately, in recent years the English engineer has been given scant opportunity to move in that direction. The “big boys” of England’s motorcycle industry will not even discuss the matter, and the small-fry clearly do not have the funds or facilities. And, until quite recently, it appeared that any ideas would have to remain just that: ideas. Now, quite suddenly,
everyone has been given hope. There is a scheme underway to divert a portion of the funds collected in the Manx Hospital Lottery for the design and development of a British “world-beater.”
As we understand it, there is to be an initial grant of £10,000 ($28,000), with a like amount to be forthcoming after one year. The money will not be given to any particular motorcycle manufacturer; instead, it will be used to hire a design team drawn from (hopefully) the best minds available. This is a noble aim, inspired by an understandable desire to bring Britannia once again to the fore, and to that extent we have only praise for the project. Unfortunately, it is not likely to accomplish its purpose — for reasons I will outline.
First off, there is the matter of who is to administer the fund. Ideally, this would be someone with a considerable background in both engineering and management, who would be able to determine which person should do what, and when. To our knowledge, no such person has been found, and if we take into account the fact that the administrator will have to say “no” a thousand times for every “yes,” and will therefore become a highly unpopular figure, the right person will probably be too smart to take the job.
Then, there is the problem of putting together a design team. Already, it is abundantly clear that everyone is trying to get into the act, but there is no evidence that anyone properly appreciates the enormity of the task. The men at Weslake and Company, Ltd., claim to have the proper power unit right now: a “research” engine with two cylinders and 355cc displacement that produces 56 bhp at 10,400 rpm. Certainly, this is an interesting design, with twin overhead camshafts, eight valves and fuel injection. But, it seems highly unlikely that a “twin” offers the necessary scope for development. It may be that data collected with this test unit could be applied to a new design, but the test unit itself will not translate directly into an effective racing engine — as has been suggested.
We also note that Bertie Goodman, of Velocette, has offered a collection of drawings and castings for a liquid-cooled 500cc “four” (54mm bore and stroke) started by his firm in 1950. From all indications, this engine could be brought to readiness very quickly, but no matter how advanced the concept may have been in 1950, it is most unlikely to offer much at this time, some 15 years later.
Peter Barthon, primary architect of the BRM racing cars (we are not sure what sort of recommendation that is), designed a 500cc, liquid-cooled “four” for Norton, and this project was well along when Norton withdrew from racing. A 125cc testbed single was built, and run, and most of the parts for two prototype “fours” were produced. A little time given to finish-machining and fitting would give England a usable, if not world-beating engine.
And then there are the sky-blue schemes. Phil Vincent, of the Vincent-HRD, wants to build a 250cc V-8 two-stroke, which would have uniflow scavenging. The mixture would be admitted to the cylinders through piston-controlled transfer ports, and exhausted past poppet valves — four per cylinder in the cylinder heads. Vincent also plans to have a sealed pumping chamber under the pistons, so that the crankcase will not be used as a scavenging pump. He plans to patent this feature and keeps details secret. Quite frankly, we mightily mistrust this sort of far-out thinking. Historically, they are a bad bet, because even when they can eventually be made to work, the development time almost invariably runs into years, and in racing, time can be an even more precious commodity than money.
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Quite possibly the most important decision to be made in connection with the whole British-World-Beater scheme is that of picking a displacement category, and this is where the arguments wax heavy. The least sensible suggestion I have encountered says that England should construct a 500cc “four,” then (in effect) whack it in half for a 250cc “twin” and finally down to a 125cc “single.” The existence of Honda’s 125cc 4-banger and their 250cc 6-cylinder makes further comment on this unnecessary.
Equally silly, in our view, is the suggestion that efforts be directed at producing a 250cc-class machine. It can be argued that, theoretically, England has the talent for an assault on this most impressive of Japanese strongholds; but, in view of the limited financing available, there is no hope of success in that class. There is no need to bother with other arguments, pro or con, because the lack of money is enough to dismiss the whole idea.
More promising is the suggestion that attention be turned to the 500cc class. Here, there are only the obsolete MV and Güera, and it would be relatively easy to secure a position of dominance. Those arguing against this plan say that there is no prestige in winning over limited opposition, in a virtually uncontested class. They overlook the fact that there is even less prestige in going up against the highly-developed Japanese 250s and getting soundly trounced. They also overlook the fact that no matter how fast the 250-class machines may get around a race circuit, it is the big, booming MV that makes the public pulse beat harder. True, to make a really lasting impression, the 500 must lap faster than all the smaller-displacement bikes, but if one cannot build a 500 that is quicker than a 250, then it is time to forget the whole affair. Finally, if England should produce a really fast 500, with or without effective opposition, it will surely capture the public fancy, and those now competing in the small classes will have to go after the 500 class, for that is where the prestige will be.
As a matter of fact, we can almost promise that the 500 class will not go uncontested. Honda is, as a matter of record, going to introduce a 500cc touring machine, and that will virtually insure their interest in 500cc-class racing. If no one else of consequence was active in that class, Honda might be inclined to ignore it, but the presence of any really first-rate machine would bring them out in a flash. What better plan could be devised than to move in now, and gain strength and experience, so that when Honda builds a 500, they will be forced into the position of a challenger going after an already strong and seasoned champion; which would be the reverse of the situation in the 250-class. Also, I am inclined to think that the appearance of a technically advanced, very fast, British machine would encourage others to have a try at it.
Assuming that what I have said about arousing the interest of others is true, England will then be faced with strong opposition within perhaps no more than a year after their initial appearance. This means that they must start with a design that offers plenty of scope for development, for otherwise they would be overwhelmed within a very short time.
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Obviously, simply saying “plenty of scope for development” and actually creating a machine to suit are two entirely different matters. There is such diversity in motorcycle design that it is difficult to settle on anything specific as being that which offers the most promise. However, when confronted with limited resources, one’s field of choice narrows down considerably. For example, in the selection of two or four-stroke operating cycle, limited time and funds virtually eliminate the two-stroke engine. At very high specific power outputs, the two-stroke engine becomes a most uncertain performer, prone to loss of power for no apparent reason. Those with development background in racing two-strokes have trouble enough coping with the problems that arise; any design team that lacked direct, recent experience in this field would be hopelessly behind. Also, there is the fact that it is relatively easy to design a 4-stroke engine to a given “target” power output. Most of the factors are reasonably well understood, and one may be confident that a 4-stroke engine will produce something fairly close to its design horsepower. Thus, prototype development time will be restricted, for the most part, to insuring reliability.
Having decided to build a 4-stroke engine, one must then settle on the number of cylinders, and the basic engine configuration. For a 500-class machine, I would opt for a V-8. Even should the detail features of such an engine be held to what is already well proven, there should be at least 80 bhp available fresh from the drawing board, and probably something near 100 bhp after the usual period of refinement.
Another feature of this hypothetical engine would be water-cooling, which would help to reduce the bulk of the unit and give improvements in both power output and reliability, relative to air-cooling. There would be some disadvantage, in terms of weight and complexity, but I very much doubt that the possible disadvantages would offset the absolutely certain benefits.
For various reasons, largely emotional, people in England seem to specify 4valves-per-cylinder no matter what the displacement or number of cylinders. I question the wisdom of this. The 4-valve configuration does give the valve-gear designer an easier job, but it has never been very impressive with regard to flow capacity. Also, the combustion chamber becomes rather convoluted and combustion control is a problem. It might be better to direct efforts toward a 2-valve layout, with “desmodromic” valve actuation. Mercedes demonstrated that the “desmo” valve system, in which pairs of cams open and close the valves without the aid of valve springs, is practical. Proper application of the principle might well provide us with the deep-breathing qualities of the twovalve layout, together with the high-speed capabilities presently associated only with Honda’s 4-valve system. In any case, it is relatively easy to experiment with cylinder heads, and the valve layout should be finalized on the basis of dynamometer results.
Borrowing from experience with contemporary Grand Prix cars, England should be able to produce a workable fuel injection system for their world-beater engine, and I would consider this virtually a “must” to get proper mixture distribution. Eight carburetors, and their float chambers, would occupy far too much room, and I fear that compromises made to get everything into the available space would have a bad long-range effect.
Although it might be possible to “get by” with a 4 or 5-speed transmission, it is safer to make provision for 6 or 7 speeds. Engines’ power ranges always narrow as operating speed and output rise, and we must look ahead to the time when we will no longer be able to afford a wide range. Power losses tend to be rather high in many-ratio transmissions, but by keeping the gears up above the oil supply, and lubricating them with just a dribble, we can limit the losses considerably.
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As for the rest of the motorcycle, it should not present England’s engineers with too serious a problem. They can call upon the best, most experienced test riders in the world, and England has already demonstrated the ability to build-in excellent handling. British suspension units and tires are almost universally used in racing in any case, so there should be no difficulties here. Then too, that country has been very successful with disc brakes on their racing cars, and these could be applied (and should be) to the GP motorcycle.
There is every reason to hope for success with a layout such as I have described. All of the techniques and data are available for building the V-8, and considering that the BRM and Coventry-Climax 1.5-liter V-8 racing engines are reliable up to about 12,000 rpm, then there would seem to be little question that England has the capability for producing a scaled-down half-liter V-8 with reliability up into the 14.000-16,000 rpm range.
Unfortunately, it is debatable that the funds being offered are sufficient. If the design and construction group finally assembled receives salaries commensurate with the ability they will need, and if full price has to be paid for all materials and services, then there is little likelihood that the job will be done. On the other hand, and this is a faint hope, with support from segments of British industry (and not only those directly involved in motorcycles) there is a good chance for success. It would all be a grand thing for British prestige, and for the sport, if something were to come of all the conversation. Even more grand, from our point of view, would be American participation in international motorcycle road racing — but that is not likely to happen. So, I must confine myself to telling the British what they should be doing with their time and money — which will doubtless increase my popularity in that country something fantastic. •
