Your winch no longer needs a V-belt brake.

[rogerflies]

In my quest to make a simpler winch (hee hee), I've come up with another great idea that works really well.

I ran across something called a "plugging switch". It's a switch that is used on industrial machines that need to stop quickly between various parts of an operation. It does this by applying reverse power to the motor until the armature stops, and then removing the power before it starts rotating in the other direction. It's also called a "zero rotation" switch.

I realized that's exactly what I need to stop the winch at the end of a launch as the line goes slack, so I built one from some stuff I had in the shop. There's a steel disc attached to the brush end of the motor armature. Next to that is a plastic support plate that holds an electromagnet and a microswitch.

At the end of a launch, the disc will be rotating CW. When the winch line goes slack, power is applied to the electromagnet, causing it to drag on the rotating disc. That causes the support plate to move up, the microswitch closes, and power is applied to the motor. As soon as the motor starts to rotate in the CCW direction, the support plate moves down, the microswitch opens, and the motor stops. A simple timing circuit removes power from the electromagnet several seconds later.

The electromagnet only drags on the disc for several revolutions during each launch cycle, so there's not much wear on the parts.

I've got it installed and working on a clutch winch, but it could also be used on a regular winch. With some minor changes, it will work with a retriever, too.

Now you can do away with the V-belt, and the drum doesn't need to have a belt groove on one end. You'll still need an arm to sense line tension, but it can be much lighter since it doesn't have to pull the belt against the drum.

I'm pretty sure I can make the plugging switch a little smaller, and I know I need to put a cover on it. I just couldn't wait to show it off.

Roger

[mlee8249]

Hi Roger,

This is a scheme known to electric car racers as dynamic braking, and is something I have been very curious about applying to our winch motors. I talked with Bob Novak of Novak Electronics some years ago on this, and the biggest problem we needed to overcome was the fact that our winch motors have almost no magnet in them. In R/C cars, the magnetic field is huge in comparison to the motor size. That allows the car motors enough dynamic braking to lock up the tires. The other thing we tried to figure out despite the magnet issue, was the application of power to the motor to cause the braking effect because there was not enough magnet. In the car motors, we are using the coasting motor to generate power as a dynamo. That power is then fed back to the motor in reverse polarity to get the motor to attempt to run backwards, thus giving us the brakes. As the motor slows down, so does the braking effect, making for very linear braking. In your scheme, I see that you are drawing power from the battery to feed to the motor in reverse for braking. I don't see this as being a significant amount of power and therefore not a big drain on the battery for the day. I'm really interested in what you are doing and would very much like to try this out.

Thanks!
Mike Lee

[Miami Mike]

The device in the photos is very nicely made!

I saw this post last night and I've been wondering since then how the rest of the circuit is going to work. It'll take a heavy-duty relay to carry all that current, and it'll have to have several sets of contacts. Have you gotten that part to work yet?

[rogerflies]

Yes, it's fully operational. I used it six times Sunday to launch my Lovesong.

Mike, you're right about the typical starter motors having no residual magnetism. The bad thing is that even putting a fair amount of current through the field windings creates almost no magnetic field that can be used for regenerative braking. Buit they sure make a good motor!!

I've tried everything I can think of to use the motor as a brake, but nothing has worked before this. I rigged up one motor so the field coils could be reversed when braking was needed. I looked like Frankenstein with all the wires hanging out, and it needed four extra solenoids to make it work. Totally impractical.

I do have one clutch winch that has a Bosch permanent magnet starter for an outboard engine. Think Little Big Winch. It works fine as a regenerative brake if you just short the armature.

The microswitch in the photo controls the flow of current to the coil of a regular starter solenoid like we all use on out winches. Since full motor power isn't needed for braking, I've got a water-cooled resistor in the circuit with that solenoid. I'm only using about 25% of the normal motor power, and it's only on for a few seconds. The added battery drain is very small. I already use the water-cooled resistor when I'm spooling up the line, so it's doing double duty.

I'll have to draw up a wiring diagram for the control system. It uses two readily available DPDT 12V relays for switching, and a couple capacitors for a timing circuit. Nothing that's hard to find, and it only takes about an hour or two to assemble it into a little Radio Shack project box.

Roger

[rogerflies]

Well, guys, I'm an idiot.

I just realized that the motor on a clutch winch NEVER needs to turn in the reverse direction. Whenever the line needs to come off the drum, the clutch is disengaged, and the drum freewheels. I think it may be turning in reverse just a little between pulses on the winch during a launch, but it doesn't really need to do that.

So, I can just put a one-way bearing on the motor, and it doesn't need a release knob like on an F3B winch.

I can do away with the brake belt, rotary solenoid, etc. I don't need the extra solenoid or the plugging switch, and the control system is going to be simpler.

Best of all, it's a machining project. That's a lot more fun than messing around with electrical stuff.

Roger

[regis]

Keep us posted!

[Whorges]

Correct me if I'm wrong here but doesn't the motor turning against the applied magnetic field actually charge the battery while the brake is applied?

[Miami Mike]

Roger, what ever became of that microprocessor-controlled braking project from last January?

http://www.rcgroups.com/forums/showthread.php?t=460181

Winch Solenoid Safety Buzzer (http://www.vvsss.com/buzzer/index.html)

[mlee8249]

Whorges,

Any motor will produce electricity as long as there is a magnetic field, and this is the dynamo effect that occurs when you turn the shaft by mechanical means instead of electrical means. Think of your basic hydro-electric plant. Water turns the turbine which turns a dynamo shaft and you light up the town. Sure, you can charge back the battery, or you can turn that power back on the motor itself and cause a braking action, known as dynamic braking.

MIke Lee

[rogerflies]

Miami Mike,
Althought the simulator worked quite well, I had problems with the clearance between the targets on the drum and the Hall-effect sensor. The drum shifts as the clutch engages, and that upset the accuracy of the counting.

It took me a while to solve that, but by then I had realized that the microprocessor and associated stuff was going to need a separate power supply to avoid the transients on the winch battery. It got more and more impractical as something to carry around in the back of the truck and use without having to pay it too much attention.

I used the same winch I built for the microprocessor to check out the plugging switch, and it's also going to be the test bed for the one-way bearing. I had to make and install a bar for sensing line tension, which was easy enough. I've already figured out the modifications required to install the one-way bearing, so I'm getting ready to order the bearing.

Whorges,
You can use the motor to charge the battery, and that's called regenerative braking. That's what's used on most electric vehicles. I was shorting out the armature, which just produces waste heat. I don't think it's called regenerative braking (as I said above), but I don't know what the correct term is.

Roger

[lenrev]

I believe the Little Big Winch uses dynamic braking. Walt has come out with a mechanical brake as an ad-on. I've spent more than a few minutes untangling my LBW line with the dynamic brake but he may be a good information source for your project..

[rogerflies]

That's the term I was looking for earlier: dynamic braking

I used it on a bunch of winches I built in the early '90s that had permanent magnet starter motors from outboard engines. It's also what I'm using for braking on the clutch winch I have for sale here: http://www.rcgroups.com/forums/showthread.php?t=576527

The first winch I built with a PM motor had the 'brake' stay on any time power wasn't applied to the motor. That made retrieving the line a llittle hard, so I came up with a way to automatically turn the brake off if the output from the rotating armature wasn't over about 5 volts.

That setting gave good braking to prevent backlash and easy retrieval of the line as long as I didn't run the chute back to the winch.

Roger

[SoCalGliderFlyr]

"Water cooled resistor"; I want to know if it can make a good cup of coffee.

[rogerflies]

The water will probably taste a little like hot plastic insulation and butt connectors, so you won't need as much coffee.

Oh, a Gatorade bottle with a wide mouth works better than the DP water bottle mentioned on the sketch.

Roger

[rogerflies]

I just got back from trying out the clutch winch with the one-way bearing installed. It worked really well. I couldn't tell much difference during the climb while pulsing the switch. The braking action was surprisingly quiet and smooth, despite being VERY quick. It's a nice improvement over the belt brake on the other clutch winch. Now I need to package the control system components neatly in a box.

The next project is to redo the other clutch winch by removing the belt brake and installing a one-way bearing.

If anyone is interested in building a plugging switch and removing the belt brake from their winch or building a clutch winch, I'd be glad to share what I've learned and help with the project.

Roger

[regis]

I have one of your winches (not clutch) - picked up a few years ago - and would be interested in removing the belt brake. :cool: Regis White regis@computer.org

[jbrandon]

Roger,

I’m looking forward to seeing the video of the brake you are adding to the winch. I am very seriously thinking of converting mine to the braking you are using to get away from the belt system.

Are you going to post details or will you share as people want the information?

[rogerflies]

I can do away with the belt on the clutch winch by installing a one-way bearing on the motor shaft. I stop the drum by engaging the clutch, then release it before the line is retrieved. It's all automatic, so I can just walk out into the field after launching. The drum freewheels when I'm pulling the line back for the next launch.

On a regular winch (one without a clutch) I can install the plugging switch. When the line goes slack, the plugging switch operates a solenoid to apply power to the motor. That stops the drum, just like tapping the pedal would. However, the plugging switch is designed to shut the motor off as soon as it starts to turn in the take-up direction. Several seconds later, the plugging switch circuit is deactivated, and the line can be retrieved in the normal manner.

I believe I can connect the control circuit for the plugging switch to retriever motor so it will work with a retriever, too. I don't have a retriever, so I haven't tried that, though.

Roger

[rogerflies]

Here's what the control box for the clutch winch with the one-way bearing looks like. Everything fits inside a Radioshack 4"x2"x1" project box except the 2 relays.

On the inside are 2 resistors in series on either side of the relay sockets and six capacitors connected in parallel. The resistors are used to soften the engagement of the clutch when it's used to stop the drum. The capacitors are used in conjunction with one of the relays to keep the clutch engaged for several seconds after the line goes slack.

The 3-prong plug provides power, ground, and a signal that engages the clutch when the first of the two solenoid relays closes. The solenoid relays are mounted next to the battery at the front of the truck bed. The clutch stays engaged while I pulse the winch during the launch, since I only let up part way on the truly-redundant footswitch.

The two white wires connect to the line tension switch, which closes when the line starts to go slack, and that starts the 'braking' sequence to stop the drum.

The black wire goes to the clutch coil. The other side of the coil is connected to the motor case for a ground.

Roger

[SoCalGliderFlyr]

Schematic?

[rogerflies]

Here it is. The sequence of operation is:

1. As the footswitch pedal is depressed enough to close the first microswitch, the first solenoid #1 closes. Power is applied to the coil of the relay #1, which closes and applies power to the clutch coil and the capacitors.

2. As the pedal is depressed all the way, the solenoid #2 closes, applying power to the motor.

3. As the pedal is pulsed during the launch, solenoid #1 remains closed, the clutch remains engaged, and solenoid #2 controls power to the motor.

4. When the pedal is let up all the way at the end of the launch, both solenoids open to cut power to the motor, relay #1 opens, power is removed from the clutch coil, and the capacitors are connected to the coil of relay #2. The drum freewheels to relieve tension on the winch line.

5. When the winch line gets slack, the bar drops down closing the line tension microswitch. This grounds the coil of relay #2, and it closes. One set of contacts on relay #2 is a latching circuit to keep the relay closed until the charge in the capacitors drops below what is required to energize the relay coil. That takes about three seconds. The other contacts in relay #2 apply power through the reisistor to the clutch coil, and the clutch engages to stop the drum, since the motor shaft cannot turn in the outbound direction.

6. When relay #2 opens, the clutch releases, and the drum freewheels while the line is retrieved for the next launch.

The latch is necessary to keep the clutch from chattering as the drum comes to a stop, since the momentum of the line coming off the drum is enough to raise the bar when the drum stops quickly.

I hope all that's clear enough.
Roger

[Ich Bin]

Another Roger thread subscribed too. Great idea for eliminating the v-belt on a winch. Man I am becoming a Roger groupie I think.

E