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Old Dec 14, 2006, 02:04 PM
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rogerflies's Avatar
Thomasville, GA 31792
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F3B winch rules interpretation -- Would a clutch-winch be allowed?

I've read that the drum on a F3B winch must be driven directly by the motor. I was wondering if having an electro-magnetic clutch between the drum and motor would be acceptable if the clutch engages automatically when power is applied to the motor, remains engaged throughout the launch, but releases several seconds after the launch is completed.

My idea is to have the one-way brake installed on the motor shaft. After the launch is completed, the clutch would automatically disengage so the motor would not turn during retrieval of the chute for the next launch. It would do away with having to unlock the one-way brake after each launch, it would save wear on the motor brushes, and it would make retrieval of the line much easier since the drum would be freewheeling.

I think the rules were written to preclude the use of reduction gears or other means of torque multiplication. My idea doesn't do that, but will the rules allow the use of a clutch?

Roger
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Old Dec 14, 2006, 03:52 PM
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I do not think so Roger, if it was I am sure you would see some out there now and you do not. The latest and greatest B winches do not have anything like it.

Marc
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Old Dec 14, 2006, 04:32 PM
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You are supposed to pull the chute down almost to the turnaround after launch to make sure everyone else can launch.

You don't always want to run the motor continuously on launch. For higher wind conditions or crosswind, there are times where you will fly the model without pulling in any line.

So I don't think the engage when you run the motor deal will work correctly.
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Old Dec 14, 2006, 04:33 PM
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No, I think that would be illegal. You could concievably kite out the plane in high wind, gaining extra line for your launch.
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Old Dec 14, 2006, 04:51 PM
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USA, CT, Hamden
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Roger,
People use coupling devices.
It's OK to stop the motor.
No line can pay out of the drum until the launch is complete.
If everytime you take your foot off of the switch, the drum locks, then you're OK.
Sounds like the one way should be on the drum, not the motor.
If the motor disenages, it shouldn't have to be held stopped.
Not having the motor turn backwards would be nice on the brushes.
The drag on the line isn't that much, its pretty easy to bring back four lines at once.
The problem is bringing them back to the correct winches and not having lines crossed on the way back!
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Old Dec 14, 2006, 05:20 PM
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Thomasville, GA 31792
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"You could concievably kite out the plane in high wind.."

No, the one-way bearing on the motor shaft would prevent reverse rotation, and the clutch would be engaged during the entire launch and for some period of time after the launch was completed. I'm thinking the clutch would remain engaged for about twenty seconds after the last tap on the pedal, but it could be longer if necessary.

I don't see how you could launch without putting any tension on the line, and you have to run the motor to do that. That would engage the clutch, and the drum couldn't turn to let any line out for at least twenty (or more) seconds.

The clutch would have not prevent you from running the chute down to the TA after the launch.

The pilot won't be able to tell the difference during the launch, but he won't have to remember to unlock the one-way bearing, and retrieving the line will be much easier.

Roger
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Old Dec 14, 2006, 05:28 PM
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Quote:
No, the one-way bearing on the motor shaft would prevent reverse rotation, and the clutch would be engaged during the entire launch and for some period of time after the launch was completed. I'm thinking the clutch would remain engaged for about twenty seconds after the last tap on the pedal, but it could be longer if necessary.
Well, that explains it a bit. Nothing about a delay or hold in the first post.
Not have to release the one way? GREAT!
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Old Dec 14, 2006, 05:35 PM
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If you put the lock on the drum, you have to remember to unlock it. I had a winch like that once, and I (and everyone else that used it) had trouble remembering to unlock the brake. It was a real PITA. From then on, all the winches I built had completely automatic braking.

The one F3B style winch I've built had a newly rebuilt motor. The buyer was very unhappy with the heavy pull required to retrieve the line. All the drag was in the brushes, since the motor was fitted with ball bearings on both ends, and it turned quite freely with the brushes removed.

Most of my winches have been built with Chevy starter motors, and they have more brush drag than the Ford longshaft motors. That's what got me started on the idea of using a clutch between the motor and drum in the first place, but I soon realized there were other benefits to the idea.

Roger
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Old Dec 14, 2006, 05:36 PM
F3X
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Quote:
Originally Posted by rogerflies

The pilot won't be able to tell the difference during the launch, but he won't have to remember to unlock the one-way bearing, and retrieving the line will be much easier.

Roger
That usually only happens once Then you learn...
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Old Dec 14, 2006, 07:09 PM
MDM
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If your not launching in a contest, you dont have to lock it, I never do.
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Old Dec 14, 2006, 09:23 PM
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Hmmm,
Better watch out Mike, the F3 Police may be looking for you!
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Old Dec 14, 2006, 11:28 PM
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Quote:
Originally Posted by F3X
That usually only happens once Then you learn...

I only forget once a day. Then next week at the field, I seem to forget again. The 400 meter round trip is good for the gut.
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Old Dec 15, 2006, 08:18 AM
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Roger -

You would need to have an emergency clutch and one way bearing release when you would want to kite out line; like when the line wraps around the plane during launch.

Secondly, is the clutch electrically actuated? If so, it would have to have minimal drain on the launch battery since CCA is limited by the rules and you would want every last joule going to the motor.

- Felix
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Old Dec 15, 2006, 01:43 PM
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An emergency clutch release would be a switch that cuts power to the clutch coil. That's easy enough to install, and it wouldn't interfere with the normal fully automatic operation of the winch.

The clutch is electrical, but the current draw is less than three amps. I'm pretty sure it could be wired up so the current going through the clutch coil would also go through the motor. I've seen some starter motors with the solenoid hooked up that way. It's a possibility, but I'd have to try it to be sure.

Roger
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