"Tony Verhulst" wrote in message
...
Bob Johnson wrote:
Actually, Craig is being too modest. In a few months of spare time work
this
spring, he single-handedly engineered and built a double drum machine...

Whats the point of the second drum? Great pics, BTW).

Tony V. (aero tows ~1300, winch tows)

http://www.soarcsa.org/pdf/winch_proposal.pdf

Have a look at page 10. Look at the number of vertical feet a two drum
winch can achieve. No tow plane can match this. Here's a good example
http://www.cotswoldgliding.co.uk/ of 200 members using winch launch, but
with a tow plane for wave tows. There are also a substantial number of
private gliders in the club. Prior to using the winch, they using reverse
pulley auto tows.

Launch rate is important, given a large number of gliders. Dragging two or
more wires to the launch point is the only sensible way to do this.
Differential are not really the best solution as they do burn up fairly
quickly if one side is locked. Transfer cases and dog clutches are fairly
common solutions.

Frank Whiteley