The P. & M. Panthette
I have been very interested in reading comments concerning the Panthette in your last two issues. I owned one of these machines some thirty years ago, and within six months of ownership I concluded that this was a very advanced design, spoiled by several features which were contrary to normal engineering practice, even in those days.
It may be of interest to enumerate one or two of the failures experienced and which, with a little foresight could have been avoided. Valve stem failures occurred at frequent intervals at the end of the threaded portion for the operating collar; the thread terminated very abruptly with a sharp incision from the forming tool to create a stress raiser from which a fatigue quickly propagated. Being an o.h.v. engine the piston suffered somewhat as also did the other cylinder due to debris travelling up the inlet tract into it.
The second failure was of the lubrication system which consisted of a metering type pump which had to draw oil from the sump, the oil level of which was some 6 in. below the pump, and with the very small volume metered by the pump considerable time elapsed before the pipe filled. In some cases it did not fill up quickly enough and the result was a piston seizure. When the lubrication system was in operation the engine suffered from over-oiling on one cylinder in the manner of many vee-twins of that period.
A third bad feature, which although it did not result in mechanical failure, was the type of gear change employed and which was quite unsuitable for a motorcycle. This gear change lever was the conventional car type and was operated by the right hand which meant that there was no control of the engine throttle whilst making gear changes. The flywheel inertia of the engine was extremely low, and when making upward changes the engine speed would fall to idling long before the change had been completed. This feature, combined with a slight amount of clutch drag, resulted in some spectacular noises from the gearbox.
The noise generated by the bevel gears at the back of the gearbox was reminiscent of a vane-type compressor and the Panthette would announce its arrival with an car-splitting shriek from these gears, some half-mile away from its destination.
The Panthette was a very interesting little machine which went very well, was economical, and had handling characteristics very much better than contemporary machines, and it seems a great pity that more development time was not spent upon it to make it free from the few serious troubles which were inherent in its design.
I am, Yours, etc.,
Derby. C. B. TAYLOR.