A Special Machine Fitted with an A.B.C. Engine.
We recently came across a most interesting machine which had the general appearance of a Douglas, but was obviously a special model.
Investigation proved that this machine was fitted with one of the 500 c.c. overhead-valve A.B.C. engines, constructed especially for high speed work. We have since communicated with the owner of this machine who is a very keen amateur, and apparently a Douglas enthusiast, for he is said to purchase a couple of these machines every year.
From the illustrations it will be clear that in order to get the engine into the frame the latter had to he specially built. It follows the usual lines of a Douglas frame, but is slightly longer. The machine closely resembles the ordinary T.T. Douglas, but the increased wheelbase has necessitated slightly longer handlebars. The carburetter is a Senspray, which is fitted in a rather unusual manner. As on the lightweight model the jet is horizontal, but in this case the stream of gases passes straight down across the jet, and is then divided by a forked pipe leading to the two cylinders.
The silencer is also slightly different from the standard Douglas type, as two exhaust pipes enter it tangentially from opposite sides. The owner states that it is very interesting to watch the silencer when the two end plates have been removed and the exhaust is smoking, for the gases can then be seen whirling round and round the silencer at a very high speed.
When first delivered there was obviously something wrong with the machine, so with the help of anotherenthusiast the owner checked the timing. It was found that the spark occurred about ¼ in. down the firing stroke at full advance.
Rather novel timing for an engine capable of 5000 r.p.m.! This was rectified, and the spark set to take place at rather less than ¼ in. before the top of the compression stroke on full retard. The difference was extraordinary, and though the owner has not as yet let the machine all out he says that it will easily attain 50 miles an hour with two up and the throttle barely halfway open. This speed is obtained with a gear of 5¼ to 1, which seems to be rather low. The owner informs us that the machine steers in a most wonderful manner, and it is possible to ride with hands off at 50 miles an hour. The fact that a speedometer reading up to 80 m.p.h. has been fitted gives some idea of the owner's expectations as to speed.
Another improvement is the Newtona adjustable pulley, which is delightful to use. It is only necessary to slip off the belt and turn the milled screw until the required gear ratio is obtained. No tools of any sort are necessary. The gearbox is of the usual Douglas pattern, but built slightly heavier than usual.
The increasing popularity of the horizontally-opposed twin, which usually renders such excellent results, gives added interest to this machine. It is now an open secret that several other manufacturers than the Douglas are intending to market a machine of this type in 1914.
To avoid any misunderstanding we would inform our readers that this machine is a special model, built to the order of an amateur, and that Douglas Bros. have no intention of constructing any others on similar lines, as they will concentrate all their efforts on the manufacture of their own 350 c.c. and 500 c.c. machines next year.
From "Motor Cycling" - July 29th, 1913