"Bob Johnson" wrote in message
news:cTpod.1733$3I.752@okepread01...
Bad error, I used torque arm instead of diameter for the drum. We are
actually doing 12.7 ft/rev, 460 rpm, 1000 lb estimated line pull, and 45
sec
to release, making the power to rotate the drum 236 hp.

The 236 hp at the drum is compared to the 75 hp required to raise the 1100
lb glider 1700 ft in 45 sec. The difference must be due to aerodynamic
drag
losses. We'll need an aerodynamicist to check that out.

The altitude-derated 180 hp provided by the 454 c.i. engine is compared to
236 drum hp. Either the rope pull was overestimated, or those 454 engines
are way stronger than we thought.

If we estimate the rope pull at 686 lb, the drum power drops to 162 hp
which
equates to estimated mechanical losses through the drive train at 90
percent, which seems about right.

So the aerodynamic drag losses must be in the order of 162 minus 75, or 87
hp.

Nicht wehr?

Bob Johnson


What your data says is that winch launch is a very lossy process
mechanically and aerodynamically. That's true.

However, since a 40 second launch only consumes about a quart of regular,
doubling or tripling the efficiency isn't going to decrease costs much.

The solution for the winch designer is to overcome these inefficiencies with
sheer power. That's why you see 350 to 800 HP winches in Europe. Most
winch fuel is consumed while the engine is idling. Diesels idle very
efficiently.

Bill Daniels