Text From The Aeromodeller

October 1961


Chas. Taylor

Britain's most experienced team race pilot offers all his 'gen' on Class B racing with his fast, monowheel

RAZZAMACHAS

including tank detail and engine modifications


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Things have come quite a way since the commencement of Team Racing in this country. We can well remember, in our first race, being trounced by the Editor and his E.D. 3.46 model pitted by his wife and H.J.N. That takes quite a memory, but by gum, it was really good fun, in the days ten years ago when 80 m.p.h. was really going, and not a single pilot so much as poked a friendly elbow in another bod's ear! However, the price of progress is bound to be more cut-throat competition, and well worth it to gain the satisfaction of a good, fast time.

It is a constant struggle to keep somewhere at the top in "B" as with any branch of our sport, but the fact that the West Essex Club have managed to win and place in quite a few races is due entirely to persistence, really hard work, and always the search for the little something that will give a few more m.p.h., that extra lap, and a second saved on a pit-stop. The means are at everyone's disposal to win, and if any tip this article contains may assist some aspiring future National winner, then a decade will not have passed vainly.

The greatest advances have been made with motors and fuels. The model itself has remained more or less the same since the introduction of the present rules some nine years ago, and provided it is of clean design, of reasonably light, though tough construction, and flies steady as a rock in any weather, no fantastic advance appears possible.

Monowheel undercarriage has mad its appearance, and would seem to be a necessary evil whilst such a landing gear is permitted by the rules Having tried both single and dual leg on the "Razzamachas", we know that the disposal of one leg and wheel does add at least 3/4 m.p.h. on a 100 m.p.h. plus model -which could mean about 12 sec. on a 7 minute race (5 laps) - which is a comfortable margin by which to win these days. We do feel that it might be a good thing if monowheel were outlawed, but while it is not, then we must use it.

One most important item on the model, of course, is the tank. Here opinions are divided between the single cell tank and the "chicken-hopper" 2-cell type. We have used both once again, and far and away our best result has been obtained with the "old-fashioned" single-cell. Certainly it has proved the more consistent, but of course it must be of the correct shape, and perhaps even more important, be positioned correctly in the fuselage. The tank design we use is shown on the plan, and has been used in all our models for the past 4 or 5 years working perfectly each time, proving that it is not suited to one model or motor only.

It should not be assumed that all the foremost Class B teams use motors of the "Special" variety that are not available on the open market. Obviously, if one reworking of a standard motor can improve performance it should be carried out, but there is a limited amount that can be done by the average modeller without access to any sort of precision machinery or the skill and experience to carry out a complete rebuild. A well-known example of contest success with a standard motor was the 7 mins 9 secs. set up by John McNess at the 1955 Nationals, a time that was not bettered until 1960. Then there is Ray Tuthill, past Nats. winner, who has put up the very good time of 6:44, once again using a perfectly standard ETA 29, this motor certainly appearing to be the best bet in this country at the moment.

We have recently carried out some trials with a Merco 29 and found it to be most economical, the model doing 60 or so laps, although the speed was obviously down a bit, at 95. The model itself was a heavy (35 oz.) battered old test-bed, so there does seem a good chance that, given a new, very much lighter model, say in the region of 20oz., it would not be beyond the bounds of possibility do the 70 laps non-stop at around the 100 mark. We are sufficiently interested to be getting such a model construction to investigate further, but for the moment, the ringed piston racing motor is tops, it being unfortunate that the ETA Vlc very good though it is, is the only one of style and capacity manufactured in this country.

We ourselves have been using both the ETA and the McCoy 29 for some time, and carry out no mods to the standard ETA at all. The running-in however, on this motor, we do carefully and most religiously, until the motor has had at least 1.5 hours running. With the McCoy four basic mods are made. The cylinder head is scrapped and replaced with another having a hemispherical combustion chamber, with a cut-away for the deflector on the piston crown, as is now incorporated on the new Wisniewski K. & B. 15 and 29. The alloy disc-valve is replaced by one made of "Tufnol", recessed on the rear face to reduce friction, and the "open" needle assembly is replaced with a single-hole spray-bar. The only remaining mod is to polish the transfer passage as munch as possible, using a piece of emery cloth on the end of a shaped piece of wood (with the cylinder removed),

On the bench, we have found that, generally speaking, one of our motors will turn an 8 x 8 "Power" prop at 14,000 r.p.m. or more, using any of the usual team-race brews incorporating 20 per cent. nitro methane, then it should be good for at least 105 m.p.h. But we have one notable exception which will do no more than 12,200 on this combination, yet musters 110 m.p.h. in the air, so where does one go from there? The moral, of course, is to treat bench readings a little skeptically as far as performance in the model is concerned-and fly the darned thing!

To do a fast time -something like 3:20 in the heat, 7 mins or under for the final,- it has become absolutely necessary to do no less than 1/2 distance on one tank full in the heat-preferably about 40 laps, allowing a good margin for safety. Up to about 18 months ago we found this most difficult to achieve consistently, but since that time have been able to do so with regularity, due to a great deal of research on fuels, both theoretical and practical.

An article on Class B fuels, giving details and reports to all our past and present formulae, including that used in the Razzamachas when the present fastest time of 6:42 was established (in a race), will appear in next month's AEROMODELLER, and should be of considerable interest and assistance to those seeking either extra laps or extra "urge". Till then-the best of luck mates!

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