Well after all the discussion about the chainsaw capstan winch, it
turned out to work absolutely even better than we had hoped. All 90 feet
of the Rohn 55 was installed on Saturday and we were done by about 3PM
with a lunch break toward the end. The winch was placed on the tailgate
of a pickup truck and the winch plate was attached to tie points in the
bed of the truck. We had a pulley at the base of the tower that made the
90 degree turn up the tower to the ginpole. I was on the tower and I had
a VOX FRS headset radio and I talked to the winch operator who listened
to me on this handheld using a pair of headphones that covered his ears
and reduced the chainsaw noise. We had no problem communicating. The
control of each tower section was better than any time I have ever put
up sections of tower. We placed each section very precisely and the 100
lb Rohn 55 sections went up the tower very easily and in perfect
control. About the most dangerous thing that happend all day was me
dropping a wrench and noone was under the tower anyway. That particular
winch is set up very well and we did not have any problems with the
chainsaw pulling or twisting around in any way. We set up the throttle
level a little more than 1/2 with the help of a velcro strap around the
trigger. With the capstan the tower section was raised and lowered with
light hand control of the rope and not by the throttle of the chainsaw
(it is the nature of a capstan winch). I was so impressed with the
performance of the winch that I am probably going to buy one for myself.
I can think of lots of simple field and yard applications for the little
winch.
Here is a link to the winch we used. If you have a good chainsaw it is a
very reasonable priced solution.
http://capstanropewinch.com/WinchFrameset2.htm
Here are some comments from the winch owner.
The capstan winch in question is owned by me. I am AC5ZO.
The winch by design has two attachment points that are bisected by the
pulling line of the rope. This maintains a balanced force and the winch
must be allowed to pivot in line with the rope pull force. The ½” bolt
that goes through this mounting area can be attached to a plate, cable
lanyard or nylon strap. The rope goes through a fairlead that guides it
to the input of the capstan. The capstan is large enough to place four
or five turns around it side by side, but that number of turns is only
necessary if you are expecting to pull to the winch capacity of about
2500 pounds. For this operation, we will only use one or two turns
around the capstan which effectively lowers the peak pull force that the
winch will develop before slipping. There is no force on the chainsaw
motor at all other than to support its own weight on the same two bolts
that support the chain guide on the saw when it is used for cutting
wood. We plan to use the cable lanyard around the tree with some wood
strips under the cable to protect the tree. This allows the winch to
pivot around the tree to ALWAYS keep in line with the direction of pull.
This is a proven system. I can understand your questions, but they have
all been addressed in the past.
This winch has been designed for balanced pull with the cable lanyard.
If I mounted it on a plate attached to the receiver on my Hummer, then I
need to make it a pivoting sort of mount so that the winch will align
the capstan with the direction of pull. Otherwise, the concerns that you
had about the rope slipping off the capstan would be realized. BTW, this
winch is geared to pull at a maximum speed of 20 fpm, so it will take
nearly four minutes to hoist a section to the top when we are near
completion. I can control the speed below that from full speed > full
stop > reverse by simply changing the tension that I apply to the rope.
If I stop pulling rope off the capstan, the hoisting stops immediately
and the capstan simply slips inside the rope wrapped around it. The saw
motor speed is regulated to approximately 50% by using the throttle held
in place with an adjustable stop.
I am a mechanical engineer, so please allow me to correct the comments
about the forces. At the pulley at the base of the tower, the rope makes
a 90 degree turn. The vector force on the pulley with a rope tension of
100# is 140# at an angle of 45 degrees to the horizon. The tension
throughout the rope is 100# and the friction in the pulleys is
negligible at these loads. The pulleys are rated for peak loads over
1000 pounds in all cases. The ginpole is a custom designed item. It has
a 1000# pulley in the top of it. The only place in the entire system
where 200# forces are seen is in the ginpole and tower itself. That is
the only place where the tension of the rope running from the tower
section creates a 100# downward pull and there is similar tension in the
rope running down the tower. Thus we have 200# of tensile force in the
ginpole and throughout the tower where it attaches as long as we are
hoisting a tower section. The ginpole was designed to also allow for the
tramming of antennas and will support a load of several hundred pounds
at full extension at a 45 degree angle to the pole, so this is probably
a stronger (and perhaps heavier) ginpole than you have ever seen. It was
designed to build this tower using Rohn 55 sections. The vertical pole
is made of DOM steel not aluminum and is over four times stronger than a
Rohn ginpole.
This is probably not a winch that you are familiar with. It is designed
for hunting, logging, and wilderness construction. It is entirely usable
on this project in the right hands. It is designed so that it does not
need a fixed mounting plate. You can see in the housing that there is an
extension to the rear that has the large bolt with the wingnut on it.
That bolt goes through the housing and is available on both sides of the
housing extension. The hooks toward the front of the winch form a
fairlead that keeps the rope on the capstan no matter what. The rope
cannot be removed from the capstan when it is under tension. The saw
motor is hanging on a bracket off to the side of the winch and is only
connected to the winch gearbox by the bracket and the chain which is
visible to the side of the winch housing in the right side of the
picture toward the front of the saw motor. You control the pull by
applying tension to the rope that is going to the left side of the
picture. The hook on the housing provides a convenient way to apply the
pull out of line with the pull line and provides some friction if you
want to hold a heavy load stopped for a while.
-Dave WD7Z
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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