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Old Sep 21, 2011, 08:06 PM
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hornet_dave's Avatar
USA, IA, Cedar Rapids
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Brushless winch experiment

It's a bit flintstonian but here's the mechanical progress so far:
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Old Sep 21, 2011, 09:28 PM
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Evan D's Avatar
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Best of luck. What are you going to use for a ESC and battery?
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Old Sep 21, 2011, 09:46 PM
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Some more details:

On a 12S lipo, the linespeed should be around 18 MPH and pull about 100 lbs at 100 amps. I'm thinking it will be a bit overkill. Drum diameter is .75" as it's going to spin at ~7000 rpm. Drum ends are wood and will be glued to the drum and prevented from shifting outwards by use of shaft collars. Only one machining operation is needed - a lathe is required to drill the hole in the end of the rod where the motor prop adapter screws in.

The ESC will be from my heli (castle ICE 80HV), and it will be controlled by a simple 555 circuit that takes the pedal "tapping" and converts it to a throttle signal. The circuit has been bread-boarded and works fine, next I need to solder it up to a circuit board and put it into an enclosure. If this whole idea works, the next step would be to add a shunt in the battery line that would reduce the throttle when the current gets high. I'm pretty concerned with the potential to burn out ESC's, as high loads and low throttle positions make hobby ESC's go "POP".

The whole winch, including battery, should weigh around 10 lbs. I have no idea how many launches I'll get on a charge.
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Old Sep 22, 2011, 01:04 AM
MrE
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United States, WA, Gig Harbor
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Set the current limiting to "Normal" or "sensitive" on the Castle. It will protect itself.
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Old Sep 22, 2011, 08:36 AM
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7000 rpm's?!!!! Be careful....at that kind of speed, those wooden parts can fly apart (I've had it happen at much lower speeds on my lathe). You need to carefully balance the whole rotating assembly or this thing could be dangerous.
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Old Sep 22, 2011, 11:01 AM
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Thx. I just worked out the calcs for the disks, I only have roughly a 100% safety factor, which does not include the sideloading from the string pressing sideways on the disks. This is not enough for comfort. If I stay with a 12S lipo, I'll have to fabricate new disks of plywood. In the meantime, keeping body parts away from the plane of rotation will be necessary!

Edit -- math error! The factor of safety is closer to 10.
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Last edited by hornet_dave; Sep 22, 2011 at 03:48 PM.
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Old Sep 22, 2011, 03:50 PM
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United States, CO, Colorado Springs
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Quote:
Originally Posted by hornet_dave View Post
Some more details:

On a 12S lipo, the linespeed should be around 18 MPH and pull about 100 lbs at 100 amps. I'm thinking it will be a bit overkill.
I know nothing of linespeed, but the Supra is designed to a 200lb winch load. What size airplane are you launching?
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Old Sep 22, 2011, 04:33 PM
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Quote:
Originally Posted by rdeis View Post
I know nothing of linespeed, but the Supra is designed to a 200lb winch load. What size airplane are you launching?
In that case, you wouldn't need to worry about destroying a Supra as my ESC would die first! In any case, 100 lbs is about the highest I can do with the batteries and ESC I have on hand. If I didn't already have the batts and ESC, I would not have attempted this little experiment. To get up to the 200 lb range, you would need a 150+ amp HV ESC, 30-40C 12S 5000 mah batteries, and a 50CC equivalent motor. I'm flying a 3M woodie so this winch should be plenty for me.
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Old Sep 23, 2011, 01:25 AM
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How are you going to stop the drum after a launch?
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Old Sep 23, 2011, 07:58 AM
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Im hoping its relatively low inertia will cause it to stop itself. If not i will have to turn on the prop brake feature which will make retrieval a pain.
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Old Sep 23, 2011, 09:22 AM
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Isn't it a three-phase motor? If so, you can switch any two leads to reverse the direction it runs. That could be accomplished with a double-pole-double-throw relay when braking is needed.

With such a small hub diameter, it's probably going to be spinning much too fast to stop by itself.
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Old Sep 23, 2011, 08:52 PM
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Miami Lakes, Florida, USA
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Quote:
Originally Posted by rogerflies View Post
Isn't it a three-phase motor? If so, you can switch any two leads to reverse the direction it runs. That could be accomplished with a double-pole-double-throw relay when braking is needed.
That might work with a steady supply of 3-phase alternating current, but not with an ESC. I'd expect the microcontroller to become totally confused and behave unpredictably if the motor leads were suddenly switched.

Using the prop brake feature is probably the best strategy. You'd just have to disconnect the power to retrieve the line.
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Old Sep 23, 2011, 09:05 PM
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USA, IL, Wheeling
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Warning Warning Will Robinson! (arms waving wildly)

Plywood drum endplates? If the line winds up against the endplates, it could blow them right off the drum ... I've seen this happen on 6 volt FLS winches with welded aluminum drums, to say nothing of wood.

Please be very, very careful with your experiments.
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Old Sep 23, 2011, 09:26 PM
MrE
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Quote:
Originally Posted by hornet_dave View Post
Im hoping its relatively low inertia will cause it to stop itself. If not i will have to turn on the prop brake feature which will make retrieval a pain.
Again, your Castle esc will save the day - it has a built in, programmable break function and will stop the motor as fast or slow as you want.

Edit: oops - didnt see MiamiMike already suggested that.
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Old Sep 23, 2011, 09:33 PM
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Quote:
Originally Posted by MrE View Post
Edit: oops - didnt see MiamiMike already suggested that.
In fact our thread starter, hornet_dave, mentioned it himself in his post #10.
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