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A long time ago I bought a used glider winch at an auction held
by the Prince Georges Radio Club, in Maryland. It cost me somewhere
around $25, which was a lot for me in the mid 1970s. The motor and
control circuitry was contained in a plywood box, with a jack for
the foot switch and terminals to clamp jumper cable to from a car.
In looking at these plans for the AAM Glider Winch shown here from
the April 1973 American Aircraft Modeler, it looks a lot like mine,
only in a box. It worked extremely well for my 99"
Windfree and
99" Aquila sailplanes.
Unfortunately, I sold it shortly after getting married in 1983 (couldn't
eat the winch). I would love to have it back.
AAM Glider Winch
Lightweight six volt winch for three-pound RC gliders uses turnaround
pulley for convenient pilot operation. Can hoist the big gliders
on 12 volts.
GEORGE STEINER
Complete winch. Note position of anchor pins
balances the 'pull of the line during tow. This complete winch weighs
only 53 lb.
Winches, winches, winches. You see one, you've seen them all.
This one pre-sented here is what I consider a little more refined
than the average run-of-the-mill type. This winch wasn't conceived
by one person. I made observa-tions for a long time at various meets
and flying fields and then created what I believe are improvements.
Many people with different ways have approached the idea of shooting
a glider into the air. I have worked with Gerry Wolfram of the South
Bay Soaring Society on winching problems and want to give credit
to him and others for their basic ideas.
This winch is ideal for the Sunday fly glider buff-about as light
a battery-operated winch you will be able to find (53 lb.). Most
others are well over the 75-lb. range. It can be constructed in
your own hobby workshop, as there is no machine work involved. If
you are a modeler you shouldn't have any trouble with this project
by using already available materials. Basic construction is straightforward
and general information on materials can be taken from the drawing.
Specifications: (1) six volt battery. (2) 12 volt starter motor.
(3) Speed (no load with starter motor modified, remove third field):
3400 rpm. (4) Speed (under average load, hoisting a three lb. glider):
2000 rpm. (5) Average current on no load condition: 45 amps. (6)
Hoisting line speed under load (average three-lb. glider): 1316
ft./m in. (7) Hoisting glider speed with a two- to three-lb. glider:
18 mph.
Beginning final assembly of the system. Note
the long shaft on the old starter motor which was resurrected from
a junk yard.
The basic layout of the 1/2" ply-wood is simple enough; decide
at this time what size battery to use. I used a small VW type 6-3/4
x 8-3/4 square, the smallest auto battery to be found. It works
fine but not for contest work. After nearly 35 to 40 hoists into
the air it will need to be recharged. If in doubt, make the winch
box the larger size as noted on the drawing; this will allow you
to use almost any larger size battery and fly for several days without
recharging. There will also be enough space to store the anchor
pins and foot switch if desired.
After cutting out the basic frame-work, do the detail work on
part "E" board before gluing and nailing it together. It will be
much easier to drill the holes this way. In positioning the starter
on "E" you may place the starter in any circular position desired.
The position shown on the drawing will place the starter hot terminal
on top. If you think you will have problems with the cables in such
close quarters, I suggest you rotate it 180 degrees.
After making sure the starter will fit board "E" with the mounting
bolts, remove and continue with the whole assembly, making sure
not to use nails that are too large, as they will split the wood.
Use a small finish nail such as No. 16 gauge 1-1/4 to 1-1/2" long.
A couple of coats of urethane varnish on all woodwork is a good
idea. It helps cut down on the splinters and gives a finished product
look to your winch.
The complete system. Foot switch operated by
the pilot. By pulsing the switch the tow strength can be modulated
to suit wind conditions.
The wood pulley assembly is made up of a household rolling pin
and a 6 x 12" piece of 1/4" birch plywood.
The end plates were rough cut on a jigsaw. Drill a 5/8" hole
in the middle. Take a short piece of 5/8" dowel about eight in.
long and place the two end plates through the holes. To true up
the end plates, place the 5/8" dowel in a small vise near a bench
grinder. Position the vise so the two end plates can be rotated
against the grinding wheel. After several rotations around the 5/8"
dowel and against the grinder, you will have very true rotating
end plates.
The rolling pin from the hardware store will have to be disassembled
by knocking off the handle at one end. Remove the steel shaft and
keep for one of the anchor pins. Make sure the hole through the
rolling pin is 5/8". Of the three kinds I had, the best one was
made by EKCO Housewares of Franklin Park, Illinois. Cut to size
using a power bench saw. Do not try to cut it by hand because it
is almost impossible to get a square surface. You want as little
wob-ble in the end plates as possible. Out of round and poor balance
of this pulley will hinder your winch rpm as much as 50%.
Use the 5/8" dowel as a jig to center the end plates on the rolling
pin while you epoxy and screw in place. This will assure more accurate
alignment to give a better and more true pulley.
Drill a 1/4" hole 1-1/4" in from the side for your 1/4" dowel
shear pin. This shear pin is a good safety feature in case the pulley
becomes locked up. Only once did it break for me, and I was pleased
that it did. If a steel pin is used it will more than likely split
the wooden rolling pin in half and cause other dam-age to be sure.
The heart of the lightweight all-wood pulley
is a section cut from an ordinary rolling pin.
The remote pulley (otherwise known as the turnaround pulley)
is made from a Schwinn bicycle front hub. It is ideal for this kind
of application because it is so easy to mount. Having ball bearings
and the sturdiness of its construction makes it perfect for this
application. One shouldn't have any problem assem-bling this unit
off the drawing. Be sure to epoxy the large 3/16" wire loops in
place. Don't forget to cut the slots out for the hub axle in F2
and F3 before you glue the nail to Fl. This will make a better fitting
job.
The wire guides over the bicycle hub are necessary to keep the
line from be-coming tangled when some gliders veer off to left or
right extremes under tow. The line falling back to earth will some-times
end up behind the turnaround pulley. When retrieving the line, it
could get caught in the assembly if it didn't have some sort of
protection to keep the line out of the bicycle hub. If the line
gets hung up in the axle, you are not going to get altitude on the
next flight-that's for sure. If the line pulls hard back to the
winch after a launch, check the turnaround for some kind of line
entanglement-it could be hung up on the anchor pins.
To bring the tow ring down after a release, a
model rocket parachute is ideal.
The winch line guide is made of spring steel wire from your
local hobby store. To get it formed, I used a one-in. socket
gripped into a vise. Start somewhere in the middle and start
twisting. A suggestion is to practice with a piece of soft wire
like a coat hanger. This should give you some practice in the
technique to be used for the hard-to-bend spring steel wire. Cut
off the excess to give the
seven-in. length to fit into board "E" brass tubing. Do not epoxy
the guide in place because it will be unhandy in transporting. Keep
it so it can be removed after a day's flying. Remember the notation
"Caution" on the drawing. Cut off the excess to give the seven-in.
length to fit into board "E" brass tubing. Do not epoxy the guide
in place because it will be unhandy in transporting. Keep it so
it can be removed after a day's flying. Remember the notation "Caution"
on the drawing.
The secret to using a light wood pulley is the use of this winch
line guide. If the guide is forgotten, the pulley will shatter on
your first tow. The advantage of using a light wood pulley virtually
eliminates any flywheeling action. A heavy pulley will cause nothing
but trouble. The backlash will be so bad you will spend hours un-tangling
the winch line after each tow. Keeping the pulley light is the key
to eliminating backlash action. A heavy pulley will cause nothing
but trouble. The backlash will be so bad you will spend hours untangling
the winch line after each tow. Keeping the pulley light is the key
to eliminating backlash problems.
The starter motor is a Ford 12 V 1954 to '64 long shaft vintage.
The wrecking yard is a good place to start looking for one. Be sure
the bearings are good and the armature isn't dragging the fields.
A modification to the starter should be made in order to increase
its efficiency by removal of the third small speed-limiting field.
This is done by cutting one of the lead wires to it. It is easy
to recognize which one. Observe the third field winding in the
starter re-moving the electrical connection on the smaller field
of the three. I found that this modification increased the rpm by
33% and lowered the current drain by 15%. The no load rpm should
be checked on six volts. If you cannot get over 3400 rpm, something
is binding or out of balance and should be corrected. This is important
because when hoisting the three- to four-lb. or more gliders you
need all the power you can get. A handy instrument in checking the
rpm is the Heathkit Thumb Tach. This can be done by placing a piece
of black tape across one end of the wood pulley as a light source
interrupter.
The starter solenoid can be picked up at a local auto parts store.
Be sure it is a six volt unit, otherwise intermittent operation
will result.
At least at one time, the AMA Plans Service offered a full-size
plans of the AAM Glider Winch and other models at a very reasonable
cost. They will scale the plans any size for you. Try out my
Scale Calculator for Model Airplane Plans.
https://www.modelaircraft.org/plans.aspx
Posted August 1, 2010
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