This is one of the few occasions, if not the only one, when the
Wrights chose the more complex solution in connection with a major
part--in this particular case, one with far more bits and pieces.
However, it did carry with it some quite major advantages. The common
spark plug, always subject to fouling or failure to function because
of a decreased gap, was not very reliable over a lengthy period, and
was undoubtedly much more so in those days when control of the amount
of oil inside the cylinder was not at all exact. Make-and-break
points, on the other hand, were unaffected by excess oil in the
cylinder. Because of this resistance to fouling, the system was
particularly suitable for use with the compression-release method of
power control which they later utilized, although they probably could
not have been looking that far ahead at the time they chose it.
High-tension current has always, and rightfully so, been thought of as
a troublemaker in service; in Beaumont's 1900 edition of _Motor
Vehicles and Motors_, which seems to have been technically the best
volume of its time, the editor predicted that low-tension
make-and-break ignition would ultimately supersede all other methods.
And finally, the large number of small parts required for the
make-and-break system could all be made in the Wright Brothers' shop
or easily procured, and in the end this was probably the factor, plus
reliability, that determined the decision which, all things
considered, was the correct one.
There was nothing exceptional about the exact form the Wrights
devised. It displayed the usual refined simplicity (the cams were made
of a single small piece of strip steel bent to shape and clamped to
the ignition camshaft with a simple self-locking screw), and
lightness. The ignition camshaft (38, Figure 5), a piece of
small-diameter bar stock, was located on the same side as the exhaust
valve camshaft, approximately midway between it and the valve boxes,
and was operated by the exhaust camshaft through spur gearing. That
the Wrights were thinking of something beyond mere hops or short
flights is shown by the fact that the ignition points were
platinum-faced, whereas even soft iron would have been satisfactory
for the duration of all their flying for many years.
Public-domain text, read in full here on John Shaqi.
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