Almost perfect payout winch launch.

On Tuesday, May 21, 2013 8:10:22 AM UTC-6, WB wrote:
In article ,

Chris Nicholas wrote:



It is possible and highly desirable to fit a guillotine to a pulley system.

My club had considerable experience with reverse pulley for many years when

we had a hard runway, and developed it to a great degree.



Method: We had 2 pulley wheels in a frame which pivoted about a horizontal

axis, and also mounted so that it could swing sideways. This enabled the

cable to run true from glider to one pulley, and from the other pulley to the

tow vehicle. Both pulleys were framed in lead-in guards. The horizontal pivot

was hollow. A spring loaded chisel-edged cutter ran through it. This could be

released from the cab of the truck on which the pulley system was mounted. It

would hit the cable, against an anvil mounted between the two pulleys. It

worked.





Sounds like an excellent setup. If we ever do groundlaunch again, we

will have to put together a guillotine system like that. Your guillotine

sounds almost identical to the one Glen Lawler put on the Eagle Winch.

It was a spring loaded chisel firing against an anvil. A hydraulic jack

was used to cock the thing. Made a heck of bang when fired. It would

shear steel rope like it was made of air. Not sure how well it worked on

Spectra, but I would expect that it had no trouble with it, especially

with any tension on the line.

I suggest a cheaper and safer guillotine is a simple air cylinder powered by a portable air tank. I bought a new 2" bore Bimba cylinder on eBay for $15 and an air tank with pressure gauge from Harbor Freight for $25. A "pop-open" push-button air valve and some air hose completes the system.

A 2" cylinder produces exactly 3.1316 pounds-force for every PSI. The tank holds over 100 PSI so the cylinder can drive a chisel blade with at least 313 Lbs-F which WILL cut a rope. Checking the gauge on the tank assures you have air pressure. If necessary, refill with any shop air compressor. Unlike a steel spring, compressed air doesn't rust or lose strength with age..

Why is it safer? You can de-energize by just removing the air hose to the guillotine so there's no chance of losing a finger. Spring powered guillotines resemble bear traps and have to be relaxed VERY CAREFULLY to work on them.

On Tuesday, May 21, 2013 8:10:22 AM UTC-6, WB wrote:
In article ,

Chris Nicholas wrote:



It is possible and highly desirable to fit a guillotine to a pulley system.

My club had considerable experience with reverse pulley for many years when

we had a hard runway, and developed it to a great degree.



Method: We had 2 pulley wheels in a frame which pivoted about a horizontal

axis, and also mounted so that it could swing sideways. This enabled the

cable to run true from glider to one pulley, and from the other pulley to the

tow vehicle. Both pulleys were framed in lead-in guards. The horizontal pivot

was hollow. A spring loaded chisel-edged cutter ran through it. This could be

released from the cab of the truck on which the pulley system was mounted. It

would hit the cable, against an anvil mounted between the two pulleys. It

worked.





Sounds like an excellent setup. If we ever do groundlaunch again, we

will have to put together a guillotine system like that. Your guillotine

sounds almost identical to the one Glen Lawler put on the Eagle Winch.

It was a spring loaded chisel firing against an anvil. A hydraulic jack

was used to cock the thing. Made a heck of bang when fired. It would

shear steel rope like it was made of air. Not sure how well it worked on

Spectra, but I would expect that it had no trouble with it, especially

with any tension on the line.

http://www.coloradosoaring.org/think...ey/default.htm

No guillotine, wire and tackle pulled through the 'pulley' apparently.

On Monday, May 20, 2013 8:26:41 AM UTC-6, Tony wrote:
On Monday, May 20, 2013 9:19:03 AM UTC-5, WB wrote:

In article , Martin Gregorie wrote: I wouldn't accept a winch or auto-tow launch if there wasn't a functional guillotine installed so that its release was instantly accessible to the driver and/or the person monitoring the launch. We used to do a lot of ground launching via the "pulley method". We always had an observer in the tow car watching the launch. Our "guillotine" was a sharp machete in the hands of the observer. Of course we were also taught to immediately bank into a tight turn and circle the tow vehicle if we could not release. I always had my doubts about recognizing the release failure in time to cut the line or to turn and get tension off the line before things got out of hand. All the pulley launch rigs I have seen are just a bare pulley, usually a truck rim mounted an a trailer hitch. No fairleads or other structure. I guess a guillotine could be mounted to such a rig. Would be a good Idea, I think.



If you're using a pulley why not just have a release on the tow vehicle?

http://framework.latimes.com/2013/05...hed-sailplane/

On Tuesday, May 21, 2013 5:20:21 PM UTC-6, Frank Whiteley wrote:

http://framework.latimes.com/2013/05...hed-sailplane/

Bad Photoshop job. You can see the real rope going past the horse to something out of the frame that's really launching the glider. However, it would have to be a gentile something - that's a Baby Albatross with a, IIRC, 65mph Vne.

Bill D wrote:
On Tuesday, May 21, 2013 5:20:21 PM UTC-6, Frank Whiteley wrote:

http://framework.latimes.com/2013/05...hed-sailplane/

Bad Photoshop job. You can see the real rope going past the horse to something out of the frame that's really launching the glider. However, it would have to be a gentile something - that's a Baby Albatross with a, IIRC, 65mph Vne.

http://www.youtube.com/watch?v=86rOfjhsIIM

I suggest a cheaper and safer guillotine is a simple air cylinder powered by
a portable air tank. I bought a new 2" bore Bimba cylinder on eBay for $15
and an air tank with pressure gauge from Harbor Freight for $25. A
"pop-open" push-button air valve and some air hose completes the system.

A 2" cylinder produces exactly 3.1316 pounds-force for every PSI. The tank
holds over 100 PSI so the cylinder can drive a chisel blade with at least 313
Lbs-F which WILL cut a rope. Checking the gauge on the tank assures you have
air pressure. If necessary, refill with any shop air compressor. Unlike a
steel spring, compressed air doesn't rust or lose strength with age.

Why is it safer? You can de-energize by just removing the air hose to the
guillotine so there's no chance of losing a finger. Spring powered
guillotines resemble bear traps and have to be relaxed VERY CAREFULLY to work
on them.

I don't think we had to worry about the spring losing strength. It took
around 500 lbs to compress it IIRC so it had some margin. Valve springs
on cars sit compressed for long periods without losing strength. Might
get rusty, but the winch was only outside when being used. No argument
about the bear trap. We did not put our fingers anywhere near that thing.
We "relaxed" ours by firing it. Not a gentle process, but worth it in
entertainment value! We never fired it in anger, not sure about
subsequent users.

I drove about 2000 launches with that winch and I miss it!