PLANET WHEEL CHAINS.
�575
�For distinctness' sake I have added the names of the links in
the formula, and also the numbers of the pairs. The formula
makes the symmetrical construction of the chain very distinct.
The lengths of the links can be altered within the widest limits ; so
��long as the closure be not made either lixed or unconstrained, any
link may be fixed and any other made at the same time as the
driving link, and in this way we can obtain from the chain most
���Fie. 433.
�FIG. 434.
�various mechanisms. We shall examine briefly a few important
cases. For simplicity's sake I have omitted the teeth of the wheels
and shown only their pitch circles in the figures.
(1.) Let the length T5 be made =0, the pairs 1 and 5 then
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