[TowerTalk] HF winch

[David Robbins]

its not a simple problem because you first have to figure how much force it takes to lift the tower at the attachment point, which 
is more than the weight of the tower already since it is a lever with lots of the weight beyond the lifting point.  then you have to 
figure the force on the cable which will be essentially 1/sin of the angle which at 45 degrees would be about 1.4 times the force 
needed to lift the 10' point vertically.


Feb 3, 2014 09:27:00 AM, nf4l at comcast.net wrote:

Thanks David,

The plan is to have a 10' tall mast, and attach the cable 10' from the bottom of the tower, giving a circa 45 degree pull when the tower is horizontal.

Do you know a formula a non-engineer could use to calculate the pull? The ones I find are all based on Newtons, And not the one I know, Fig.

Mike NF4L

On Feb 3, 2014, at 8:59 AM, David Robbins wrote:

> yes, the pull on the cable goes up quickly as the tower tilts... it can be way more than the weight of the tower, especially if not connected at the top of the tower and if it doesn't have enough height.
> 
> also, think about the pulley system again.. if you go to 2 or 3 to one advantage you also have to handle 2 or 3 times as much cable on the drum... AND have to run the winch for 2 or 3 times longer to wind or unwind that cable. getting that advantage does come with a cost!
> 
> 
> 
> Feb 3, 2014 08:54:30 AM, john at kk9a.com wrote:
> 
> I am not a mechanical engineer, wouldn't the pull on the cable be
> significantly more than the weight of the tower when tilting it? Then you
> plan on running a 55 amp motor with a 20 amp power supply?
> 
> John KK9A
> 
> 
> To: towertalk reflector 
> Subject: [TowerTalk] HF winch
> From: Mike Reublin NF4L 
> Date: Mon, 3 Feb 2014 07:46:27 -0500
> 
> I picked up a 2500 lb. rated 12V. winch from Harbor Freight intending to
> use it
> for tilting my HG-70HD tower. Weight with antennae and rotor etc. is between
> 1200 and 1300 lbs. I was hoping to run it from a 20A power supply.
> 
> I plan on a pulley arrangement that will give me a 2:1 advantage. I could
> go to
> 3:1.
> 
> If I read the specs right, the winch draws 55 amps when the load is 1000 lbs.
> The duty cycle is 45 seconds on, 14 MINUTES off. Mounting is 2 bolts,
> M8-1.25x35 mm.
> 
> Seems a tad sketchy. Your opinion?
> 
> 73, Mike NF4L
> 
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