Sorry, I read quickly and thought you were talking about capstans in
general. I've never been a sailor. Been on a few wild rides though, and
appreciated the skill involved.
There was one notable accident with a capstan which was mounted on a
swivel base, where the base lock pin failed, the capstan rotated, the
rope came off the drum, and a bad situation ensued. Swivel bases are
frowned upon. The attraction to them is that you can easily position the
capstan to be lined up properly. But it's easy to jockey a truck around.
Even better is to use a redirection block hanging off your ladder rack
so it doesn't matter which way the vehicle is positioned. This is all
assuming you are using a receiver hitch mounted capstan - the only way
to go BTW for regular tower work.
-Steve K8LX
On 9/13/2017 15:01 PM, Grant Saviers wrote:
?? I think I point out that self tailing (sailing) winches are a bad
choice. And capstans are a good choice, particularly if they have
reversing. Lot's of them in use as you mention.
Do the problems I mention never happen on capstans? The original
post question was basically "what can go wrong using a capstan?"
Grant KZ1W
On 9/13/2017 11:05 AM, Steve Maki wrote:
Grant,
I can only say that if the sudden load movements and other
undesirable occurrences you describe were common happenings in the
tower industry using industry standard catheads, they would not be
industry standard equipment.
The AB Chance catheads in particular were designed for the overhead
line industry, and have been used safely for decades for
installing pole transformers and HV lines.
I wonder what type of capstan you were using while sailing. It
doesn't sound like the right gear for tower work.
-Steve K8LX
On 9/13/2017 12:28 PM, Grant Saviers wrote:
Years of sailing with winches large enough to pull 2+ tons taught
me a few lessons about self tailing and hand tailing.
Fortunately my or others screw ups resulted only in flailing
sails, not the disaster that can happen with heavy vertical
lifting. Although an out of control boom can be a lethal device
as a friend was killed by one.
I would never use a self tailing winch for overhead lifting.
While the grip systems usually work, "usually" is not safe
enough. They are also sensitive to the size, type of line and
its condition. Then the release from the self tailing mechanism
requires actions which often cause a jump in the load part of the
line. The person releasing the line is in an awkward position to
control the line and has fingers close to the drum.
The person doing hand tailing needs to be thoughtful, alert,
communicative, physically capable, and trained. Just as any
other ground crew member. The functional problems I encountered
with sailing winches were overruns, jams, and run-offs. An
overrun is when a line gets under a turn nearer to the load
(basically a half hitch knot). These can be very hard to safely
or slightly release. A jam can happen when the turns get so tight
together (or too many turns on the drum) they need hand massaging
or a turn unwound to release and slip. Run-offs are when loops
slip off the open end of the capstan and the tailing load jumps
or becomes the total load. These are sometimes caused by the line
handler not paying attention to the angle of the free line to the
capstan, or jumps in the load.
Is a spool drum winch better? - it depends. Different kinds of
jams occur for winches of the type used on vehicles and tractors
(experience with this), which btw are not overhead load rated. A
crane winch spools wire rope with perfect lays to not have those
problems. Like my HDX589's feeder to the spool. However,
working with wire rope has a lot of downsides for handling and
rigging. Not the way to go IMO for amateur radio sized towers
and loads especially with the rope technology now available.
The pro team that did my big tower used ropes and a capstan with
power up/down. That capability with a good operator avoids the
problems mentioned with lines on capstans. The loads were up to
350# antennas and controllable in less than a inch up/down. A
convenient tie off on a cleat was on the winch mount and that was
backed by a safety tie off. The tower sections weighed up to
1000# and went up with a crane. Although they had the gin pole
and winch capacity for them the crane was faster, cheaper, and
safer. For more than 25G towers and bigger than tribanders, I
think these are the ways to go.
Grant KZ1W
On 9/12/2017 19:23 PM, Richard (Rick) Karlquist wrote:
I have been reading about how nice capstan winches are, but I
have no experience with them. They seem very dangerous since
the line comes loose and the load falls down in case the line
handler's attention wanders for a second. It seems especially
dangerous to be lowering a heavy load when the handler has to
pay out the line just fast enough, but not too fast. A foot
switch is suggested, but it doesn't work as a dead man safety.
The winch stops but the line still slips if not held back.
Seems like an accident waiting to happen, like free climbing a
tower. Can someone with experience explain how these capstans
could possibly be safe?
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