Open Frame and Sporting Models.
FOR 1916 the Metro Manufacturing and Engineering Co. are concentrating their energies on the 2½ h.p. two-stroke sporting model, which will not be altered radically from the 1915 design, and also an open frame model, which we illustrate.
The engine has a bore and stroke of 70 mm. x 70 mm., giving a capacity of 269 c.c. Very large air cooling ribs are used, with further transverse ribs across the top of the cylinder, curving downwards in the centre to receive the pressure release valve and its separate small pipe. The fins taper towards the base, and give the cylinder the modern pear-shaped appearance first familiar with the Gnome aviation engine. Every care is taken, both in manufacture and erection, to prevent the escape of oil from any of the joints, a trouble rather frequently encountered even with modern two-stroke engines. The flywheel is external and of large diameter, with the weight massed at the outer edge. The crank pin is solid with the webs, and the big end of the connecting rod is, therefore, split to take the two gunmetal halves of the bearings.
Hence, it is easy to remove the connecting rod and piston when it becomes necessary to adjust the bearings, and there is no necessity for fresh bushes when the ones originally placed in the engine may have become worn.
Two rings only are used for the piston, the gudgeon pin being secured in phosphor bronze bushes by a small set screw firmly locked in position when it has once been screwed home.
There is an external transfer passage cast as part of the cylinder and delivering mixture from the crank case to the combustion space when the piston falls below a port cut in the cylinder wall, there being the usual sharp-edged baffle plate on the top of the cast iron piston to direct the incoming mixture towards the head. A Senspray carburetter is bolted to a port behind the transfer passage, and feeds the crank case through a cast passage, divided from the transfer passage by a wall. The carburetter is at the rear of the cylinder, while the exhaust pipe, which is of large diameter, is taken in an easy curve from the front of the cylinder to a large circular silencer secured below the magneto platform. Oil is led from the tank through a large Best and Lloyd sight feed lubricator and adjustable drip feed to a pipe connected to the inlet passage from the carburetter, oil being sucked into the engine with the incoming gas, a method which tends to keep the carburetter cleaner, and, in some measure, to prevent oil being blown from the air intake of the carburetter all over the machine and its rider.
An Attractive Petrol Tank.
In the sporting model the top tube of the frame is inclined from steering head to seat pillar, and the tank is therefore of wedge shape. In order to increase the capacity of the latter, however, it also widens gradually towards the forward end, being in shape somewhat like the Tourist Trophy tank fitted to the Douglas machines, and giving this sporting model a remarkably neat and workmanlike appearance. Brampton biflex front forks are fitted.
There is a heel-operated rear brake on the left-hand side of the machine, the pedal being on, the footrest tube, while the brake acts on the belt rim below the chain stays. The Bowden operated hand brake acts as usual on the front rim. We understand that the special compression release shown in the sketch is manufactured and fitted under licence from the Triumph Company, although it is of slightly different form from that on the Junior Triumph. Every effort has been made to stop oil diffusing from the end of this tube and spreading about the engine and machine.
Both the oil and petrol fillers are large enough to enable the rider to do without a petrol funnel should this be necessary ; 26in. wheels are fitted.
The Motor Cycle November 18th, 1915. Page 494
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