New winch height record

On Nov 29, 2:57 pm, "Bill Daniels" bildan@comcast-dot-net wrote:
We actually tested the power required to retrieve Spectra and the starter
motor is way more powerful than needed. Not sure what your problem is at
Lasham.

Derek will answer for himself, but I expect they retrieve against the
pay-out brake on the winch, as per normal operation. If you don't, the
drum will keep turning under its own momentum when the retrieve stops
and you'll get cable everywhere. Not good.


The cost of Spectra is more like three times the cost of steel not 5 times -
I checked the prices this morning. It takes a LOT of power to pull steel
cable across an airfield - I can pull a mile of Spectra with one finger.

We need verifiable data from retrieve winches. Your tests at Lasham are not
verifiable since you did no controlled experiments.

Having been to Lasham myself and talked to people there (though not
yet witnessed the retrieve winch itself operating), I'm perfectly
satisfied that what Derek says about the performance of both UHMWPE
and retrieve winches is correct.


Dan

"Dan G" wrote in message
...
On Nov 29, 2:57 pm, "Bill Daniels" bildan@comcast-dot-net wrote:
We actually tested the power required to retrieve Spectra and the starter
motor is way more powerful than needed. Not sure what your problem is at
Lasham.

Derek will answer for himself, but I expect they retrieve against the
pay-out brake on the winch, as per normal operation. If you don't, the
drum will keep turning under its own momentum when the retrieve stops
and you'll get cable everywhere. Not good.

Yes, they certainly pull against the heavy payout brake - they have to,
they're using steel cable. You have to keep steel under tension to prevent
tangles. Spectra/Dyneema doesn't need that tension.

Spectra/Dyneema doesn't ball up and tangle like steel so you use much
lighter braking force. In fact, with tension control used for braking, very
light reverse torque is more than enough to prevent problems so very, very
little force is needed to pull out a Spectra cable from a winch designed to
take advantage of Spectra/Dyneema.

To get all the benefits of Spectra/Dyneema, you have to not only modify the
winch, you have to change operational techniques. Just throwing it on an
old steel cable winch and using steel cable operating techniques is
guaranteed to fail - as it did at Lasham.


The cost of Spectra is more like three times the cost of steel not 5
times -
I checked the prices this morning. It takes a LOT of power to pull steel
cable across an airfield - I can pull a mile of Spectra with one finger.

We need verifiable data from retrieve winches. Your tests at Lasham are
not
verifiable since you did no controlled experiments.

Having been to Lasham myself and talked to people there (though not
yet witnessed the retrieve winch itself operating), I'm perfectly
satisfied that what Derek says about the performance of both UHMWPE
and retrieve winches is correct.


Derek says Dyneema doesn't work because it's too expensive, wears out faster
than steel and doesn't provide any aditional height. Evedence from many
other sites successfuly using Dyneema is to the contrary on all points. The
difference is that successful sites did their homework and made all the
neccessary changes.

Bill Daniels

On Nov 29, 5:38 pm, "Bill Daniels" bildan@comcast-dot-net wrote:
Yes, they certainly pull against the heavy payout brake - they have to,
they're using steel cable. You have to keep steel under tension to prevent
tangles. Spectra/Dyneema doesn't need that tension.

The pay-out brake is not to keep the line under tension, it's to stop
the drum when the retrieve stops, or the drum keeps turning and paying
out cable which forms great big loops hanging down from the drum. A
drum of UHMWPE will of course be much lighter than a steel one, but
the drum itself is heavy enough. If the brake is weak you have to tow
very slowly, which is frustrating.


Derek says Dyneema doesn't work because it's too expensive, wears out faster
than steel and doesn't provide any aditional height. Evedence from many
other sites successfuly using Dyneema is to the contrary on all points. The
difference is that successful sites did their homework and made all the
neccessary changes.

Lasham isn't the only club that tried UHMWPE and abadonded it.
Pocklington tried it too - with a brand new Skylaunch winch - and also
abandoned it. Another club I know well is only using up their current
stock of it before reverting to steel. A number of sites had initially
very favourable results with UHMWPE but I've never seen any follow-up
results, which were promised by the BGA but have never materialised
(afaik).


Dan

"Dan G" wrote in message
...
On Nov 29, 5:38 pm, "Bill Daniels" bildan@comcast-dot-net wrote:
Yes, they certainly pull against the heavy payout brake - they have to,
they're using steel cable. You have to keep steel under tension to
prevent
tangles. Spectra/Dyneema doesn't need that tension.

The pay-out brake is not to keep the line under tension, it's to stop
the drum when the retrieve stops, or the drum keeps turning and paying
out cable which forms great big loops hanging down from the drum. A
drum of UHMWPE will of course be much lighter than a steel one, but
the drum itself is heavy enough. If the brake is weak you have to tow
very slowly, which is frustrating.

I bet it's frustrating. Why don't you re-engineer it so it works right.

You need to re-think tension. Steel needs to be kept under tension any time
you are moving it. If it is just laying in the grass, it's still under a
little tension due to friction with the grass.

If it takes 70hp to pull out the cable, you're using way too much brake.
Tension control winches use the hydraulic motor to provide light reverse
torque, not a brake. It takes very little reverse torque to prevent over
runs with UHMWPE.



Derek says Dyneema doesn't work because it's too expensive, wears out
faster
than steel and doesn't provide any aditional height. Evedence from many
other sites successfuly using Dyneema is to the contrary on all points.
The
difference is that successful sites did their homework and made all the
neccessary changes.

Lasham isn't the only club that tried UHMWPE and abadonded it.
Pocklington tried it too - with a brand new Skylaunch winch - and also
abandoned it. Another club I know well is only using up their current
stock of it before reverting to steel. A number of sites had initially
very favourable results with UHMWPE but I've never seen any follow-up
results, which were promised by the BGA but have never materialised
(afaik).


The start of this thread was about some very talented folkes in Belgium who
set a release height record using UHMWPE on a winch designed for it. UHMWPE
is a spectacular success as a winch rope. It beats steel on all counts
including wear and life. In fact it lasts long enough to actually be
cheaper than steel on a per launch basis. BUT, you have to understand it
AND you winch has to be designed for it.

Skylaunch is a great steel cable winch. However, it would need a lot of
modifications to make it a successful UHMWPE winch. I sincerely hope they
do this since it would be easier than trying to convince the world that
UHMWPE doesn't work.

UHMWPE has never failed anyone but some people trying to use it have failed
to use it properly. If you want to know how to use it right, talk to the
people who succeeded not the ones who failed. Make a call to Belgium.

Bill Daniels