David L. Thompson wrote:
> This is a good idea as the big mechanisms sold by the tower Mfg add $$$ to
> the cost ( up to $3,000). The first commercial attempt was Tow-Tec (a W2).
> Perhaps the Sears drill motor is faster than the Tow-Tec (sold to The Hazer
> people 10 years ago) which took 30 minutes for one ham's 64 foot alum crank
> up to come down and nearly 50 minutes to crank up..
>
> Perhaps Henry WA0GOZ could tell us how fast the sears drill motor works
> and how he adapted it to the winch crank handle?
>
> Towers are work, but fun!
>
> 73, Dave K4JRB
It is some time since I did the calculations for my motorised tower system, but
50
minutes does seem quite ridiculous. I calculated the 'work done' in raising the
tower
from the nested position to full height. (I have a heavy 60 feet 3-section
crank-up) I
then decided how long I was prepared to wait.... 3 or 4 minutes as I remember
and
divided the work done (in Joules) by 180, the time in seconds. This told me the
power
required in watts. Although I am not an engineer (I am trained to do 'sums') I
then
applied sound engineering practice and put in a safety factor... probably x 5,
again
cannot remember.
In the end I bought a 3/4 hp (non-metric!) 1400 rpm, capacitor start motor . I
used a
worm gearbox and a pulley system to gear this down 80:1, giving a little under
20rpm.
The winch needed 60 turns to raise the tower. There you have it, three minutes
to
raise. Very cheap because I didn't have to buy the gearbox. No interlocks etc.
I go
outside and stand by it to watch that no cables get caught.
Total cost $300 (guessing $150 for the gearbox).
73,
Chris
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Chris Pedder G3VBL/8P9EM
E-mail g3vbl@netcomuk.co.uk
AX25-mail g3vbl@gb7bnm.#45.gbr.eu
DX-Cluster g3vbl > gb7dxd
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