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Old Nov 06, 2005, 04:56 PM
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Thomasville, GA 31792
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Look Ma!! No (visible) brake!! My latest winch...

I just finished my latest ClutchWinch. The brake is the motor. It's a permanent magnet starter motor for a 250HP outboard engine. By shorting out the armature, the motor acts like a generator under heavy load. It stops the drum almost as quickly as the solenoid operated belt brake I have been using up till now.

Doing away with the external brake eliminates the belt, brake solenoid, and some other parts. In the works is a way to do away with the tension sensing arm that rides on the winch line.

Roger
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Old Nov 06, 2005, 05:14 PM
Think Thermals!!!!
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Costa Mesa, California
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How much is the motor?
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Old Nov 06, 2005, 05:36 PM
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I paid just over $100 for a new one on eBay. I think it's more powerful than the similar motor used in the Little Big Winch. It doesn't seem to be as powerful as the little Chevy motor in my last winch, but it's just right for my Lovesong.

Roger
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Old Nov 06, 2005, 07:58 PM
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Joined Sep 2005
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So I'm confused. If I understand correctly, you're using an electric starter motor for your winch.
1. It looks like you're pluged into an AC outlet???
2. It's clutched? Is this clutched by the spring loaded gear like most electric starters in cars?
3. If the aswer to #2 is yes, isn't the motor disengaged because the cluth lets go when you come off the pedal? Doesn't that mean the motor doesn't brake the system b/c it's disengaged?
4. What size planes are you towing with this?
5. Can you provide some details so I can build my own?
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Old Nov 07, 2005, 12:57 AM
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"So I'm confused. If I understand correctly, you're using an electric starter motor for your winch.
1. It looks like you're plugged into an AC outlet???"

The AC plug is used to provide 12VDC power and a signal input to the control box on the winch. The control box has some small relays and capacitors in it.

"2. It's clutched? Is this clutched by the spring loaded gear like most electric starters in cars?"

The elecrtic clutch is from an automobile air conditioner compressor. It's not the over-running clutch in the starter Bendix.

"3. If the aswer to #2 is yes, isn't the motor disengaged because the clutch lets go when you come off the pedal? Doesn't that mean the motor doesn't brake the system b/c it's disengaged?"

When you come off the pedal at the end of the launch, the clutch disengages, and the drum freewheels until the line goes slack. Then the relays in the control box engage the clutch and short out the armature at the same time.

The footswitch has two microswitches which operate in sequence as the pedal is depressed. When the first switch is closed, the clutch engages. When the second is closed, the motor runs. When you're pulsing the winch, you only let up enough to open the second switch, so the clutch stays engaged during the climb.

"4. What size planes are you towing with this?"

I use the winch to launch my Lovesong (74 ounces, 134" wingspan).

"5. Can you provide some details so I can build my own?"

There's a bunch of photos of my winch stuff here:
http://photobucket.com/albums/1003/winchman/

I'll be happy to answer any questions. Just email me.

Roger
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Old Nov 07, 2005, 01:18 AM
Think Thermals!!!!
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Costa Mesa, California
Joined Mar 2004
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That is a lot of effort just to get a sailplane in the air. My first winch as a six volt ford starter motor in an old wood tackle box with the battery. The shaft stuck out the side with a drum made of part of a rolling pin with masonite end plates. Anti backlash was the side of your foot as you took it off of the salvaged Singer sewing machine pedal.
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Old Nov 07, 2005, 02:25 AM
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I'd have to agree with anyone that said I go overboard on the winch stuff, but I enjoy the challenge of mechanical design and machining almost as much as flying. I made my first winch using a generator from an old VW as a motor. Talk about crude!!

I "retired" when I was 46, so I've had plenty of time to pursue a wide range of hobbies, most of them related to RC in some way. Machining is one of my favorites, and the only one that has paid for itself.

Roger
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Old Nov 07, 2005, 11:46 AM
Think Thermals!!!!
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Works of art to be sure!

I've always wanted to explore a gear belt driven drum with the motor below and to the back side of the drum. A bit more elaborate dynamic braking. Possibly processor controlled. I don't see any way to get rid of the arm riding on the line. It's the discharge angle of the line that is a direct relationship to line tension.
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Old Nov 07, 2005, 02:45 PM
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"I don't see any way to get rid of the arm riding on the line. It's the discharge angle of the line that is a direct relationship to line tension."

Actually, I'm working on that aspect of the winch now. Here's how:

I figure there's also a direct relationship between drum acceleration and line tension. The drum will continue to accelerate until the tension on the line is about gone.

If you set up a magnetic or an optical sensor and a microprocessor to monitor the rotation of the drum, the change in the interval between pulses would tell the MP when the drum had stopped accelerating. The intervals would be decreasing, then become constant. At that point, the MP would activate a switch to apply power to the motor (and engage the clutch on a CW).

The MP system would continue to monitor the rotation of the wheel, but now it would be looking for the wheel to be nearly stopped. The intervals would be increasing, then reach a preset value. At that point, it would open the switch, and power to the motor would be turned off.

Power would be applied to the motor only long enough to stop the rotation of the drum, probably a fraction of a second in most cases. I'm pretty sure you could get it close enough to stopped to avoid tangles, and that's all that's needed. A couple RPMs either way isn't going to be a problem.

On a conventional winch, this would eliminate the sensor bar that rides on the line, the brake belt, and the part of the drum that the belt drags on. That would be a significant improvement, if the MP system wasn't too expensive.

Roger
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Old Nov 07, 2005, 03:39 PM
Think Thermals!!!!
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My experience with line tensioning is from designing in line coating units integrated into printing lines. Mostly plastic packaging like bread wrappers. The easiest and thus most dependable is a roller arm riding on the printing stock (referred to as a web).

Keeping track of the hub rpms is a good idea. Just need one of the optical rpm units used for power planes. A radially marked end plate on the hub would be sufficient. Could just paint the lines on. However this is not line tension. May be able to use hub rpms with the motor load to find line tension. I would investigate what is currently available for web tensioning.

Take a look at http://www.anaheimautomation.com or http://www.minarik.com .
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Old Nov 07, 2005, 05:33 PM
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I agree that the system I'm suggesting won't be measuring the tension directly, but it will be measuring the effect the tension has on the rotation of the drum. A lot of tension will cause high acceleration, less tension a lower acceleration.

The MP in the system will compare the last interval (between pulses from the sensor) to the previous interval to determine if the drum is still accelerating. As the tension decreases, the acceleration will decrease, and the speed of the drum will become nearly constant. When the difference between the intervals falls below a certain amount, it will be an indication that the tension nearly gone, and it's time to stop the drum. Hopefully, we'll be able to adjust the set points to fine tune the system.

Anyway, the fellow that's helping me with the selection of components and the programming seems to think it will work, so I'm going to give it a try. It involves stuff I haven't worked with before, so I've got a lot to learn.

Roger
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Old Nov 07, 2005, 05:57 PM
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Radian's Avatar
Coral Springs FL
Joined May 2002
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Line tension measuring

Why don't you just use a piezo pressure sensor attached directly to the drum spindle mount on the frame in such a way that line tension on the drum presses on the transducer? When line tension drops, so will the pressure on the sensor.

Radian
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Old Nov 07, 2005, 06:00 PM
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Coral Springs FL
Joined May 2002
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Another way

Thinking about it more, How about some hydraulic circuit like surge brakes on a trailer?

When there is line tension, the brake is off (like pulling on the trailer). When there is no tension, the brake is on?

Radian
www.phflyers.com
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Old Nov 07, 2005, 06:09 PM
Think Thermals!!!!
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Good luck. Drum rotation speed alone does not indicate line tension.
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Old Nov 09, 2005, 08:51 AM
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Thomasville, GA 31792
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"Why don't you just use a piezo pressure sensor attached directly to the drum spindle mount on the frame in such a way that line tension on the drum presses on the transducer? When line tension drops, so will the pressure on the sensor."

The problem with that approach is that the tension on the line creates a torque on the drum. If the drum can rotate freely (as it does when there's no power on the motor), the pressure on the transducer will be much less than the tension on the line, because most of the tension is causing the drum to accelerate. You can prove this by wrapping some string around a pulley. Hold the axle while you pull on the string. If the bearings are decent, the pulley will spin up, but you won't feel much pull on the axle. Most of the force will go into accelerating the pulley.

I made a winch one time with the motor mounted on a rocker arrangement. When the motor was runnning, the motor would move forward on the pivots. As soon as I came off the switch, the motor moved back, even though there was still quite a bit of tension on the line.

You suggestion could be used to make a winch that shut the motor off if the tension got above a set amount, though. That might be something to play with if you get tired of pulsing the footswitch.

"Good luck. Drum rotation speed alone does not indicate line tension."

Thanks. I agree. Drum rotation speed alone does not indicate line tension.

However, drum ACCELERATION does indicate line tension. The speed of the drum can not increase if there is no tension on the line. Conversely, (disregarding bearing drag, windage, etc) the speed of the drum will continue to increase as long as there is tension on the line. I don't care how fast the drum is turning. I just want to know if its speed is still increasing.

Roger
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