Pawnee with Tost internal tow rope system

On Saturday, December 9, 2017 at 4:26:53 PM UTC-5, wrote:
On Friday, February 6, 2015 at 10:12:01 AM UTC-8, kirk.stant wrote:
Our club (in the US) is looking at a Pawnee that has the Tost cable retractor winch system and we are curious about it's operation.

For example, it appears that the rope requires a Tost weak link assembly at the glider end, but none at the towplane end. How are US operators setting it up? Tost weak link for glass and a "straw" for Schweizers?

How is the rope deployed on the ground? Does the ground crew just grab the rope end at the tail of the towplane and let the towplane taxi away?

Anyway - any info on club operating procedures with this system would be appreciated.

Cheers,

Kirk
66



On Friday, February 6, 2015 at 10:12:01 AM UTC-8, kirk.stant wrote:
Our club (in the US) is looking at a Pawnee that has the Tost cable retractor winch system and we are curious about it's operation.

For example, it appears that the rope requires a Tost weak link assembly at the glider end, but none at the towplane end. How are US operators setting it up? Tost weak link for glass and a "straw" for Schweizers?

How is the rope deployed on the ground? Does the ground crew just grab the rope end at the tail of the towplane and let the towplane taxi away?

Anyway - any info on club operating procedures with this system would be appreciated.

Cheers,

Kirk
66

I'm building up 10 Wakerly-Walls winches. They are for PA 25 only. It is installed in front of pilots feet. Been used for over 50 years with NO PROBLEMS and no accidents. They will be FAA approved shortly and for sale then. ha12Aatt.net

Approximate cost?
Uli
'AS'

On Saturday, December 9, 2017 at 1:26:53 PM UTC-8, wrote:

I'm building up 10 Wakerly-Walls winches. They are for PA 25 only. It is installed in front of pilots feet. Been used for over 50 years with NO PROBLEMS and no accidents. They will be FAA approved shortly and for sale then. ha12Aatt.net

I made three front mounted tow reels for SoaringNV's PA-25's. I used the basic design from the reels made by Jim Indrebo, followed by Rex Mayes. Their reels uses a 1/4 urethane tube for the drive belt and Hall effect sensor for reel keep-run and auto-off.

I further refined the design by using a stronger mount to spread the load better at the gear cluster, a chain drive to eliminate slippage, a much more powerful motor so rewind would be fast and efficient at any speed (with the belt drive one would have to slow to pattern speed to retract - redline?, no problem with mine. In fact I tested it by towing my golf cart toward the chocked Pawnee!

I made the electronics box modular, so you could swap or replace the electronics box (2 screws in nut plates and two plugs) for service or troubleshooting. No need to remove the whole unit.

The tail fitting was more robust, and used a brass sleeve slide fitting on the stinger to allow for tailspring movement. And rather than a Delrin funnel (which the rope wore grooves in, I made the funnel of anodized aluminum that could rotate on the stinger for even wear.

The motor was shorted with an approx. 2 ohm resistor dynamic braking of rope pay-out, so the line person had a small amount of resistance to prevent overrun. This also keeps the rope from paying back out after retract in flight.

The Hall sensors allow for one button "start and forget" retract. A relay prevents "bounce back on" if a reel magnet should happen to line up with the hall sensor on full retract.

I did not build or design the guillotine. Rex had a few extra and we purchased those from Williams Soaring. The motors were sealed, purchase from Surplus Supply, and were from a robotics over run of some sort - they were excellent. The rig hauled in 200 feet of line in little more than 20 seconds IIRC.

As with most everything I've ever made or designed, there's always improvements I think of only after MKI. Guess that's why there was a MKIV yaw string (now owned by Wings and Wheels who's doing a great job BTW!). There was a new, easie to make MKV yaw string a couple of years back that few people know about - an abject failure . . . so it may stay with just a few people knowing about it :c)

Fred was right about my lack of desire to make more of the reels. I built one, then two more at the same time, not much mass production time savings. Each took about 80 hours I think. Could be done faster with plans, and if Piper built their frames exactly alike . . I didn't design the mount to be adjustable, so they were fitted to each ship.

On Friday, February 6, 2015 at 10:12:01 AM UTC-8, kirk.stant wrote:
Our club (in the US) is looking at a Pawnee that has the Tost cable retractor winch system and we are curious about it's operation.

For example, it appears that the rope requires a Tost weak link assembly at the glider end, but none at the towplane end. How are US operators setting it up? Tost weak link for glass and a "straw" for Schweizers?

How is the rope deployed on the ground? Does the ground crew just grab the rope end at the tail of the towplane and let the towplane taxi away?

Anyway - any info on club operating procedures with this system would be appreciated.

Cheers,

Kirk
66