I just happened to remember there is a relatively easy way to maintain
equal tension on dual tram lines.
As an aside, for stability, remember to hang the load under the lines
with pulleys of adequate strength riding on the tram lines.
Going way back to the "horse and wagon days" and borrowing some of their
advanced technology it's relatively easy to maintain equal tension on
any "equal" number of tram lines. It can be done for an odd number too
but I'll stay away from that one for now.
When using a team of horses to pull a wagon they used a simple device
called an "evener". The evener is simply a bar with one horse
connected on each end with the load connected to a pivot point in the
middle. Replace each horse with a tram line and hook a come-along to
the pivot point using a clevis. The only critical dimension, assuming
the bar is strong enough to hold the load, is the attach points for the
tram lines much be equal distances from the pivot point. In this case
the attach points will be the same distance apart as they are at the
top. The tension on the come along will be twice the tension of either
tram line or rephrased, the tension of each tram line will be half the
tension on the come along.
Roger (K8RI - ARRL Life Member)
N833R (World's oldest Debonair)
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