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Hello,

I am curious about the feasibility of building an electric winch to tow hang gliders. I apologize if this is a little off-topic, but I figured that the EV community would be the most relevant source of information!

Typically glider tow winches use an ICE driving a hydraulic pump+motor which pulls in 1000's of feet of line while pulling the glider attached to it into the air. Electric could be much more efficient, however, considering the short duty cycles of the winch. Following is a little background on what is needed:
  • Max peak power needed at the winch drum (after any gear reduction,etc) would be around max 350ft-lbs of and max 650rpm drum speed, so about 45hp peak. This much power would only be needed rarely for a heavy tandem glider flying in no wind. An more typical tow with a normal breeze might be 125ft-lbs of torque at 200rpm and last 1 minute.
  • Line Tension (torque) control is how a winch needs to work. The drum (ie motor) speed needs to automatically and constantly change (because of changes in wind speed) to maintain the desired line tension. Towing in strong winds can means that the winch drum goes from +100rpm to 0rpm to -50rpm in order to maintain the same line tension as wind increases.
  • A tow lasts about 1 to 3 minutes, with usually at least 10 or 15 minutes off-duty until the next tow. 100 minutes total would be a high estimate for cumulative on-duty winching time on the field before it is brought back to charge at the end of the day. A generator could be run to charge the batteries through the day, possibly cutting down greatly on the number of batteries needed.
  • Weight is not an big issue, as the winch is parked in one spot and pulls the glider in.
Based on this information, I am looking for advice on the following questions:
  1. Are there controllers that can regulate a motor (amps I assume) so that it will maintain a fixed torque output? So, for example, the winch can be set to 100lbs of line tension, and the motor will vary its speed in order to hold this tension (torque), even allowing the motor to turn backwards if needed? If not, rope tension may need to be sensed and inputed to a programmable controller.
  2. With these specs, what would a rough dollar estimate be to get the motor, controller, battery, etc?
  3. What would be the most cost effective way to do it? Would a fork lift motor work, etc?
Any answers or advice are greatly appreciated!

Cheers,
Ryan
www.instinct.pro
 

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Are there controllers that can regulate a motor (amps I assume) so that it will maintain a fixed torque output? So, for example, the winch can be set to 100lbs of line tension, and the motor will vary its speed in order to hold this tension (torque), even allowing the motor to turn backwards if needed?
Hi ryan,

Yes, this is much like an industrial process control application where the tension on a web or belt is needed to be kept constant. Most of those do not go backwards, but I do not see that as a big issue. I think the motor/drive choice would be an induction motor running in flux vector mode in 4 quadrant torque control.

Regards,

major
 
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