?? 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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