Winch Hardware - To swivel or not swivel

[John G. Harte]

Our club is fortunate enough to have a winch, and a large number of ground
launch endorsed pilots.

We use a steel cable and encounter some kinking and twisting at the glider
end of the setup. Last weekend we installed a swivel in line before the cg
hook and were initially pleased with the first several launches; however,
after several more, we encountered even more twisting and kinking, but,
alas, the kinking and twisting occurred in that portion of the cable that
was descending after release.

Has anyone had experience with swivel installations?

Input would be greatly appreciated.

jgh

[John Wilton]

John,

If you are using a free-running swivel with stranded cable I believe that
the problem is that as the cable is put under tension the six outer strands
will try to unwind from around the inner strand. Unfortunately in their
unwound state they are now longer than the inner strand so they shed their
load onto the inner strand which will probably break - trashing the cable.
A better option is to use a lock-up swivel that will not rotate when under
launch tension but will rotate after release to allow the cable parachute to
spin (as they do) without winding up the cable.

Hope this helps,
John Wilton


"John G. Harte" > wrote in message
link.net...
> Our club is fortunate enough to have a winch, and a large number of ground
> launch endorsed pilots.
>
> We use a steel cable and encounter some kinking and twisting at the glider
> end of the setup. Last weekend we installed a swivel in line before the
> cg hook and were initially pleased with the first several launches;
> however, after several more, we encountered even more twisting and
> kinking, but, alas, the kinking and twisting occurred in that portion of
> the cable that was descending after release.
>
> Has anyone had experience with swivel installations?
>
> Input would be greatly appreciated.
>
> jgh
>

[Bill Daniels]

"John G. Harte" > wrote in message
link.net...
> Our club is fortunate enough to have a winch, and a large number of ground
> launch endorsed pilots.
>
> We use a steel cable and encounter some kinking and twisting at the glider
> end of the setup. Last weekend we installed a swivel in line before the
cg
> hook and were initially pleased with the first several launches; however,
> after several more, we encountered even more twisting and kinking, but,
> alas, the kinking and twisting occurred in that portion of the cable that
> was descending after release.
>
> Has anyone had experience with swivel installations?
>
> Input would be greatly appreciated.
>
> jgh
>
My experience is that swivels just don't help that much. Stranded steel
will twist and kink and then break at the kinks no matter what you do. It's
just really mean stuff.

The best idea is to convert to Spectra/Dyneema. Since it is a hollow braid
it doesn't twist or kink. The bonus is that you get 15 - 20 % higher
launches. No one who is using it would ever go back to steel.

Bill Daniels

[F.L. Whiteley]

John G. Harte wrote:

> Our club is fortunate enough to have a winch, and a large number of ground
> launch endorsed pilots.
>
> We use a steel cable and encounter some kinking and twisting at the glider
> end of the setup. Last weekend we installed a swivel in line before the
> cg hook and were initially pleased with the first several launches;
> however, after several more, we encountered even more twisting and
> kinking, but, alas, the kinking and twisting occurred in that portion of
> the cable that was descending after release.
>
> Has anyone had experience with swivel installations?
>
> Input would be greatly appreciated.
>
> jgh
Tost recommends that the swivel only be used when pulling out the wire rope,
not under launch tension.

I've found that putting a 'set' into the wire rope when new and every few
hundred launches also helps. We attach the wire rope to a vehicle and give
it a good hard static load.

Frank

[Bill Gribble]

F.L. Whiteley > writes
>> Has anyone had experience with swivel installations

I'm no expert, and I'm sure somebody else from my club will correct me
if I'm wrong, but I believe we use three locking swivels in our setup,
one between the plastic-sheathed strop and the thick connecting rope,
another between the rope and drogue chute, and the third between the
drogue and the stranded steel cable used by our Skylaunch winches.

I do know, within my experience at least, that the setup appears to be
very effective in that we don't have any problems with twisting or
kinking in the cables.

--
Bill Gribble
http://www.scapegoatsanon.demon.co.uk
- Learn from the mistakes of others.
- You won't live long enough to make all of them yourself.

[GM]

John G. Harte wrote:
> Our club is fortunate enough to have a winch, and a large number of ground
> launch endorsed pilots.
>
> We use a steel cable and encounter some kinking and twisting at the glider
> end of the setup. Last weekend we installed a swivel in line before the cg
> hook and were initially pleased with the first several launches; however,
> after several more, we encountered even more twisting and kinking, but,
> alas, the kinking and twisting occurred in that portion of the cable that
> was descending after release.
>
> Has anyone had experience with swivel installations?
>
> Input would be greatly appreciated.
>
> jgh


John,

our club had a free swivel installed on the retrieve vehicle's hookup.
The drouge chutes were detached and only the cables were hooked up.
Retrieving the cables with a slight drag on the drum allowed the cables
to unwind, if they wanted.
What kind of cable are you using?
I guess it also makes a difference how you transfer a new cable from
the factory reel to your drum. We would suspend the cable reel in front
of the winch between two saw-horses and slowley take it up onto the
drum. Our winch picked up the cable over the top, so the factory reel
paid it off from the bottom. Theory here was to try to counter the
natural curl. The cable was then paid out and retrieved around 10 times
with the swivel installed and the resistance gradually increased to
pre-stretch it. As far as I can remember, we did not see the kind of
kinking you are describing.

Safe winching,

Uli Neumann

[Nick Hill]

Bill Gribble wrote:
> F.L. Whiteley > writes
>
>>> Has anyone had experience with swivel installations
>
>
> I'm no expert, and I'm sure somebody else from my club will correct me
> if I'm wrong, but I believe we use three locking swivels in our setup,
> one between the plastic-sheathed strop and the thick connecting rope,
> another between the rope and drogue chute, and the third between the
> drogue and the stranded steel cable used by our Skylaunch winches.
>
> I do know, within my experience at least, that the setup appears to be
> very effective in that we don't have any problems with twisting or
> kinking in the cables.
>

I believe the swivel on our winch cables lock under tension, i.e. locked
during a launch but free once the glider is off the cable to allow the
drogue chute to rotate without twisting the cable when winding in.

Nick Hill

[Stefan]

From the Tost homepage:

"Use swivel only if necessary, and then only for unwinding cable, never
while launching."

Stefan