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!