Tost reel system

There is another option. A tow reel that addresses the shortcomings of the Tost system while building on its advantages. The Tost system mounts in the fuselage behind the pilot, a slug on the tow line, near the tow plane end, transfers tow line load to the tug's tail fitting. But as mentioned, if there are tangles, it's possible to have the reel mount tear loose and head down the fuselage towards the tail (or so I've heard).

I believe Jim Indrebo (last of Crazy Creek Soaring - now closed and Jim retired) first came up with a tow reel that mounts ahead of the pilot to the tubing supporting the gear cluster and more that capable of handling all towing loads.

Rex Mays, (Williams Soaring Center) improved upon the design as well, but his used a 1/4" polyurethane tubing "belt" to connect motor pulley to spool pulley. The belt tended to slip and belt maintenance was a bit of a pain. This system used a sensor to monitor spool speed to shut down the motor upon retraction when the spool slowed. The rope passed through a guillotine mounted to the floor in front of seat, the handle at the left side of instrument panel. The rope then goes through a conduit to the tail fitting that's mounted to the tail wheel spring forward attach with a pivoting/sliding mount on the spring body further back. Jim/Rex used black plastic (Delrin?) for the tail fitting - this was a wear item due to rope friction. Mine used anodized aluminum for this fitting and was mounted to the tail "stinger" so it could freely rotate to equalize wear.

I made several other "improvements" on the Bumper version, chain drive, much stronger motor (adapted from a surplus robotics motor, this allowed retraction at any tug speed as with the belt drive one had to sometimes slow to pattern speed). In ground testing, the initial reel in was measured at approaching 200 lbs - it would rapidly pull my golf cart (the load), towards the back end of the Pawnee!

Electronics were housed in a modular/swappable plug in box for easy troubleshooting and to allow in-field replacement, hall effect sensor is used to shut off motor at full retraction. A momentary push button retract switch starts the automated retract and if held in, overrides the auto function to serve as an emergency rewind if the push and forget function failed - it didn't.

Pay-out rope "breaking" to prevent overspool tangles, is provides by motor control relay shorting out motor with a 2 ohm power resistor in series - resistor size can be changed to vary pay-out tension.

I built 3 of these the reels for SoaringNV, took at 80 hours each! And as with Rex Mayes, before me, I made a promise to myself that I would not be making any more. We got field approvals for the reels, there is not STC. I believe Soaring NV has the documentation.

The first two I made worked nicely. I goofed on the third, making the spool two inches too wide. Not realizing the impact that a wider spool would have, I proceeded to build it that way when I could have easily corrected the error while still under construction. We found with a wider spool, rope builds up in the center and when this build up collapses off to either side, it introduces slack areas in the rope that can overlap and potentially cause tangles. A narrower spool offers side support to the rope and prevents this.

bumper

On Wednesday, April 26, 2017 at 7:54:44 PM UTC+3, bumper wrote:
There is another option. A tow reel that addresses the shortcomings of the Tost system while building on its advantages. The Tost system mounts in the fuselage behind the pilot, a slug on the tow line, near the tow plane end, transfers tow line load to the tug's tail fitting. But as mentioned, if there are tangles, it's possible to have the reel mount tear loose and head down the fuselage towards the tail (or so I've heard).

I believe Jim Indrebo (last of Crazy Creek Soaring - now closed and Jim retired) first came up with a tow reel that mounts ahead of the pilot to the tubing supporting the gear cluster and more that capable of handling all towing loads.

Rex Mays, (Williams Soaring Center) improved upon the design as well, but his used a 1/4" polyurethane tubing "belt" to connect motor pulley to spool pulley. The belt tended to slip and belt maintenance was a bit of a pain. This system used a sensor to monitor spool speed to shut down the motor upon retraction when the spool slowed. The rope passed through a guillotine mounted to the floor in front of seat, the handle at the left side of instrument panel. The rope then goes through a conduit to the tail fitting that's mounted to the tail wheel spring forward attach with a pivoting/sliding mount on the spring body further back. Jim/Rex used black plastic (Delrin?) for the tail fitting - this was a wear item due to rope friction. Mine used anodized aluminum for this fitting and was mounted to the tail "stinger" so it could freely rotate to equalize wear.

I made several other "improvements" on the Bumper version, chain drive, much stronger motor (adapted from a surplus robotics motor, this allowed retraction at any tug speed as with the belt drive one had to sometimes slow to pattern speed). In ground testing, the initial reel in was measured at approaching 200 lbs - it would rapidly pull my golf cart (the load), towards the back end of the Pawnee!

Electronics were housed in a modular/swappable plug in box for easy troubleshooting and to allow in-field replacement, hall effect sensor is used to shut off motor at full retraction. A momentary push button retract switch starts the automated retract and if held in, overrides the auto function to serve as an emergency rewind if the push and forget function failed - it didn't.

Pay-out rope "breaking" to prevent overspool tangles, is provides by motor control relay shorting out motor with a 2 ohm power resistor in series - resistor size can be changed to vary pay-out tension.

I built 3 of these the reels for SoaringNV, took at 80 hours each! And as with Rex Mayes, before me, I made a promise to myself that I would not be making any more. We got field approvals for the reels, there is not STC. I believe Soaring NV has the documentation.

The first two I made worked nicely. I goofed on the third, making the spool two inches too wide. Not realizing the impact that a wider spool would have, I proceeded to build it that way when I could have easily corrected the error while still under construction. We found with a wider spool, rope builds up in the center and when this build up collapses off to either side, it introduces slack areas in the rope that can overlap and potentially cause tangles. A narrower spool offers side support to the rope and prevents this.

bumper

When was this, and what kind of electronics were used?

When was this, and what kind of electronics were used?

I built the tow reels guessing 5 years ago. I designed the electronics, a very simple circuit.

A single pole double throw power relay to drive the motor when energized, the NC (de-energised) contact put the motor braking resistor across the motor. The power relay was driven by an ELK924 sensitive relay. The input current required for the relay is low enough so that a simple RC time constant circuit, triggered and kept charged by a Hall effect sensor with 4 magnets embedded in the aluminum side of the drum, would keep things energised until rope reeled in. Push button to start, hall effect takes over until end of rope, RC circuit drops out and motor stops.

The sensitive relay was wired using both sides of the relay, one to drive the power relay, and the other to act as a anti-bounce back circuit. The reel slowing would drop the sensitive relay, but if the reel bounced back to align a magnet with the hall effect sensor, motor prevented from being energised again until the retract button again pushed.

All the documentation went to SoaringNV. I may have a schematic with the circuitry somewhere, though not on this computer, sorry.

bumper