On Fri, 19 Mar 2004 08:24:24 -0700, "Bill Daniels"
wrote:


"Mark James Boyd" wrote in message
news:405aa3e8$1@darkstar...

I'd love to see a winch design that uses a 100hp or less engine,
can be easily bolted on the back of an old pickup, and has engine
and parts that are low maintenance and (especially engine) easy
to acquire (either locally or via shipping).

Alternately, how about a "spare tire" that is really a winch drum.
a stable sturdy "jack" and some way to route the cable
to ensure it winds up nice.

Might not work (thoughts of side loads tipping my car
over come to mind!), but it sure is fun to play with the
thuoght!
--

------------+
Mark Boyd
Avenal, California, USA

Mark, unfortunately, the physics of a winch launch says that it takes about
1 kWh or 3,600,000 Joules to launch a glider. The peak power demand places
yet another constraint on the minimum HP that must be available. Those
numbers point to a 400 to 500 HP engine to be able to provide launch service
to any glider in the existing fleet. Although the initial cost of a well
engineered winch is high (nearly as much as a tow plane) the long term costs
are only a few percent as much a tug.

The good news is that the total energy consumed for one launch (About 1
liter of diesel fuel equivalent) is tiny compared to any other launch method
except bungee launch. (Excluding, of course, the beer you have to provide
the bungee crew.)

A glider winch is a highly specialized piece of machinery that needs the
kind of engineering Ulrich is asking for. Please avoid the temptation to
cobble some junk together to make a barely workable winch. That sort of
thing has given winch launch a bad name in the USA.

A well run winch operation is very attractive to newcomers to the sport. It
shows a lot of ground activity that is visible to the onlookers and the
rides are a real thrill. Lets get winching!

Bill Daniels

If you have a diesel driving through a fluid flywheel you don't need
that much power: we have a Supacat with a 245 hp Deutz V8 aircooled
industrial diesel and torque converter (no gearbox). This can launch
an ASH-25 or just about any Nimbus. With a 15 m glider, K-21 or Grob
you'd expect 1200-1400 ft on a 1000m run in calm conditions and over
2000 ft if its blowing a bit.

I'd agree with everything you've said about the specialised nature of
a glider winch, the heavy duty engineering and the costs.

--
martin@ : Martin Gregorie
gregorie : Harlow, UK
demon :
co : Zappa fan & glider pilot
uk :