How fast does a winch turn/pull ?

[gyrokiteguy]

How fast do the 12V and 6V long shaft starters turn ?

What is the linespeed of the glider tow line ?

I think a 12V winch runs at 3,000 RPM. Is that right ?

How fast would a 6V winch run ? 4500 RPM ?

The inner wrap of the drum is 2 inches in diameter.

3000 RPM x 2 x pi = 18,849 inches per minute = 1570 feet per minute = 17.85 MPH

Are these numbers right ? They seem slow. Shouldn't the line speed be faster ?

[slopemeno]

2-man tows in F3J (right...F3J?) can make a plane really go up the line- how fast does the average 30-something guy sprint?

For instance, back when I was just starting out I had a Gentle Lady and still hadn't got my high-start, so I convinced a friend to hand tow it, and it went up like there was no tomorrow.

[rogerflies]

The line speed numbers are misleading since that's the "sink rate" of the plane as it's being pulled toward the turnaround.

The forward speed of the plane will be whatever it would go if you added ballast to bring the weight up to the tension on the line, and flew it in level flight. You'd have to make adjustments for the angle of the climb x gravity, and maybe for the line drag.

From my experience with the Briggs engine-driven winch, I'd put the shaft speed of a strong winch launching a moldie at around 3500 rpm. I had the Briggs winch running at it's top speed of 3000 rpm (limited by the governor according to the engine specs) when we launched a moldie, and it looked a little slower than an all-out launch with my friend's electric winch. Both winches have 2" hubs on the drums.

Roger

[jtlsf5]

We did a test of actual line speed in preparation for an event where we would use vehicles to relaunch XC planes on course. The actual line speed for these launches was 22 mph. This was done using winches with a piece of colored tape on the down line, with a truck pacing the marker during launch. Turned out to be just right for the car tow too.

[dephela]

Its not the "no load" speed that's important but the rpm's while under load, which varies.

[podrieger]

I remember reading that a 6 volt Ford starter motor turns about 3,400 rpm on 6 volts with no load. This is increased to 5,200 rpm with 12 volts and a set of "Real Ball" end plates.

A lot has to do with how much line in on the drum at the start.

Our think our winches are between 3 and 4 hp.

Maybe the Winch Doctor could chime in as he is the expert.

Phil

[gyrokiteguy]

Very interesting. Thanks for the information.

It sounds like a winch should be designed for a WOT line speed of 20 to 25 MPH for the performance planes. I would have thought it to be much faster than that.

Has anyone launched a large scale ship/ fast slope soarer with a winch ? Like the 2.5 or 4m Chinese models ? What sort of line speed do they need ? They seem to have a faster stall speed, so I assume they would need a faster tow line speed ? I guess if a running man can throw one and make it glide, the stall speed can't be that high. Or can it ?

Thanks !

[tkallev]

A 4+ meter scale ship will be difficult (if not impossible) to hand launch, I would recommend ROG. Also understand that most of these ships have deep fuselages and a towhook on the bottom of the fuse is a long way from the center of pressure of the wing which will result in a very large pitch up when it breaks ground, be ready with copious amounts of down elevator. The smaller sailplanes might be hand launched successfully, throw hard and level, don't just tension up and let go :eek:

A technique used with good results in the past has been to use a tow bridle with the hooks attached to the bottom of the wing or the side of the fuselage near the bottom of the wing to reduce the amount of pitch up on rotation. Tie a knot in the bridle so that the yoke of the bridle cannot slip over the top of the fuselage ... that, too, can result in some ugliness.

Do not expect the launch of a scale plane to get the same altitude a competition plane will get, the drag of the large cross section fuselage and long skinny wings will not let you load up the line like a moldie. Use a conservative tow hook location or else tip stalls may be in your future.

Winch launching can be done safely and with good results, but aerotow is a better alternative.

tk

[gyrokiteguy]

Sure aero tow would be nice. But then we would have to build a tow plane. I've been discussing this matter here:
http://www.rcgroups.com/forums/showthread.php?t=1052936

As far as the tow point is concerned, why couldn't one put the hook near the nose ala the real scale plane ? Then the pilot could control the pitch of the plane ala the real scale plane ?

I did some calculations.

Launching a 20 pound scale model to 1000 feet is 20,000 foot pounds of work neglecting drag, motor inefficiencies, etc. Given that sailplanes have lift to drag ratios of 30+, that isn't a bad assumption. We can adjust for inefficiencies at the end.

Lets say it takes 20 seconds to reach 1000 feet. The *average* power to do that is 20,000 ftlbs / 20 seconds = 1000 ftlbs/sec. 1 HP = 550 ftlbs per second.

100 ftlbs/sec / 550 ftlbs per second = <2 HP.

I am designing a special winch with adjustable speed and torque (line pull limiting) to launch said 20 pound gliders. Stay tuned.

[mlee8249]

Hi Gyrokiteguy,

There are many variables you are dealing with in this set of questions. As mentioned by dephela, it doesn't matter the no-load speed, but the RPM under load is what matters. That's only one factor. Other factors include:

* Winch drum diameter: Diameter varives from 1.5 inch to 3-inch diameter. A smaller diameter gives you a lot more torque (line tension) versus the larger diameter giving you a lot more speed (it pulls in line faster, but you lose torque). Along with this is how much line you have on the drum as it reels in. The drum diameter changes constantly as the line gathers on the drum during launch.

* Size of the model: A larger and heavier model may use up more energy than a smaller model. More energy means more tension is needed to achieve satisfactory climb angle and speed.

* Set-up of the model: If the model is well tuned to a maximum performance winch launch, it will absorb a lot of power with a launch that is very steep. If poorly set up, it may launch flat and not require a lot of power and then the winch may have to provide a lot of RPM just to stay up with it.

* Winch set-up: There is a lot to be said about a winch set-up, from the proper gauge wiring to a good strong battery and solenoids. Sport flying pilots probably won't worry too much here, but competition pilots will, as they strive to get maximum performance from the launch. Note that a poorly set-up winch will do things like stall out easily, fry a terminal because the connection is not solid, will not come up to RPM because it can't get enough amperage, or it might even burn up the motor. Having a darn good battery is also golden. I changed to using the Optima battery from a standard deep cycle type, and my winch runs completely different...for the better!

* Who's using the winch and how. Some guys tap the winch pedal like a rock and roll drummer on a hot set. Others just stomp on down and hold it that way until the plane pings off. Really good pilots know how to use just enough pedal to get the most efficient launch.

There really is no magic number or thing like that to get the perfect speed or RPM setting. If the planes you launched were all the same, and you wanted the best winch set up for those planes only, you might be able to do something like that. But the perfect speed and perfect amount of torque for 100-inch Sagitta will not be good enough for a Pike Perfect.

Mike

[gyrokiteguy]

mlee: I know there is no one answer. I was just asking what the current systems use. That is a starting point. As I stated, I'm designing mine to have settable maximum current (line pull) and speed. This would allow people to hook on their gliders and gradually increase the settings until they get the tow they like.

Right now none of the winches are the same. Holding the pedal down on one winch will break the wings while another will get the model launched so so. And there is no way to regulate the winch itself, save the actions of the pilot running the foot switch.

As far as the drum diameter changing speed and linepull as the line reels in, one could program the winch controller to account for that.

The reason I harp on the controllable speed and linepull is that large scale gliders aren't built for 10g of pull and I think they will need to be handled much more gently than the competition gliders. Thus I need a very powerful winch, but also a gentle, controlled winch.

[gyrokiteguy]

How many starts will a fully charged 12V heavy duty battery give ?

Thanks !

[rogerflies]

That sounds like a really interesting project. I'm eager to see more about it.

Roger

[slopemeno]

You could always build a "scooterzilla"

[gyrokiteguy]

Here are the details.

I'm not going to have time to work on it for a few months. It would be great if you started working on it, Roger. I'll CAD it up and do the software if you want.

It will be really simple to build, but a bit expensive if one does all the optional things.

Details

- isolated drum, ie drum runs on its own pillow blocks, one at each end
- use a flex couple to connect the drum to the motor. Can't transfer any radial loads to the motor bearings. Torque only.
- drum inner diameter to be 1", from solid steel stock to prevent bending under pull. 4130 steel would be nice, but not necessary. Aluminum would work if the drum width is kept small.
- this inner drum diameter (1") is chosen to get about the right drum speed, although the ultimate drum speed can be controlled with the controller.
- lest anyone wants to start talking about rotating weight, look up moments of inertia and notice the diameter of the shaft.

Motor
This 7KW peak outrunner motor.
http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=5139&Product_Name=HXT_80-100-A_180Kv_Brushless_Outrunner_(eq:_70-55)

No more brush maintenance !

7 Kw is way more powerful than the Ford longshaft starter motors. The most I have heard them taking is 12V x 400a = 4.8 Kw and their efficiency is probably terrible at that power level.

Controller
This 150A controller.
http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=9102&Product_Name=TURNIGY_K-Force_150A_OPTO_2-6S_Brushless_ESC_(DE_Warehouse)

It can be programmed for all sorts of things, such as start hardness, braking, etc.

Cooling
The motor and ESC may require a bit of airflow in the form of a small computer fan to cool them down if the launches are really frequent and hard.

Batteries
Here is where the options start. This winch could be run on 3 12V batteries OR a 12S 10,000 ma lipo pack. The reason for using the lipos is that the all up weight of this winch with lipo batteries will be less than 20 pounds, probably more like 15 pounds with judicial use of materials and conscious component selection. Very portable.

The 12S lipo pack has comparable energy to a single HD 12V battery. 44v x 10ah = 440 watt hours. 12v x 50 ah = 600 watt hours. The outrunner motor will probably be more efficient than the starter motors as well. Given all this, the lipo back should last just as long as a HD 12v battery.

The lips would be really nice for fields that store their winch on site and yet have to take the batteries home at the end of the day to charge. No more lugging around a 60 pound battery !

Foot controller.
One will need a BEC and a foot controller with a rheostat in it. The output of the rheostat will be fed into the ESC just like a receiver would feed it. Thus the operator would have full variable speed control over the motor.

Furthermore, the motor controller has a governor function for those that would like constant speed operation.

Additional Control
A microcontroller with LCD could be placed between the foot switch and the ESC. It could do all sorts of things such as:

1) Allow the user to set various winch tow parameters such as speed, max line pull, etc.

2) Monitor the battery current and adjust the speed setting to control the line pull during the launch. This would probably save a few planes over the life of the winch.

3) Count the revolutions of the drum, knowing the line length at all times, thus giving the user some indication of how high the glider is when he releases.

4) Monitor and report the battery state.

5) Allow programming of custom parameters such as soft starts, increasing line pull as the tow goes on, slowing down linespeed as the tow goes on, etc.

6) Killing the motor in the case of a broken tow line. Stopping the motor instantly in case of an emergency.

7) Turning the ESC/ Motor cooling fan on and off.

etc.

Remote Control Operation

A wireless link such as this could be put between the foot control/ micro controller thus allowing the pilot to be placed anywhere he wants. This would also allow the winch to be placed at the far end of the field, allowing half the line to be used and doing away with the return pulley entirely.

http://www.sparkfun.com/commerce/product_info.php?products_id=559

I bet 3/4 of the breakages of the tow line occur in the line span that runs along the ground between the winch and the return pulley. This would do away with most of that wear.

Comment on Motor Power and Battery Life

Launching a 20 pound glider to 1000 feet in 30 seconds takes 30,000 watt seconds at 100% efficiency and an average power of less than 2HP or 1.5 Kw.

A fully charged set of 12S 10a lipos should hold 440 watt hours of energy, enough for 48 tows of the 20 pound glider to 1000 feet, again at 100% efficiency. In real life, one would probably get half that many or 24 tows.

If the winch is constantly being used to launch 20 pound gliders to 1000 feet, it should be run from 3 12V batteries. But for launching regular gliders to more regular heights, it will probably run all day without needing to be recharged.

7.5 Kw is more than enough to launch even the largest glider. The motor chosen will produce 25 pounds of thrust running at 50% power turning a propeller, enough power to take a 20 pound glider vertical. It will be 4x that powerful when pulling on the towline.

The thing about a winch is that it can launch many models every hour. With aerotow, the tow plane climbs out much slower, has to do a circuit, land, etc. With a winch, as soon as the towline is returned to the flight line the next model can be attached and towed. No pilots are needed. Everyone gets to fly sailplanes.

Many soaring locations have banned IC planes. Furthermore, many glider pilots don't want to listen to a swarm of chainsaw engines working hard all day. That means the tugs must be electric.

But that is difficult to implement because of how fast the batteries in the tow plane will run down pulling big gliders and how many tow planes are needed to service a fleet of gliders looking for aerotows. A super winch or two would be much faster and more efficient than a fleet of tugs.

What I want a superwinch for is launching my own large scale gliders. I want it to be super portable so that I can make use of just about any impromptu field, all by myself. I especially like not having to use the return pulley so that one doesn't need to worry about having a nice clear path between the winch and the return pulley. Once the plane has the line off the ground all the wear on the line has ceased.

I look forward to your feedback on all this.

[tonyestep]

The line speed of about 20 mph is in the right ballpark, depending on drag through the grass, battery condition, etc. However, as the plane goes up the line, it gets going faster; its speed is line speed / cos(tow angle). So if you're pulling in line at 20 mph and the plane's flight path is at 60 degrees to the towline, the plane is traveling at 40 mph.

[gyrokiteguy]

The line speed of about 20 mph is in the right ballpark, depending on drag through the grass, battery condition, etc. However, as the plane goes up the line, it gets going faster; its speed is line speed / cos(tow angle). So if you're pulling in line at 20 mph and the plane's flight path is at 60 degrees to the towline, the plane is traveling at 40 mph.

If one uses the microcontroller option, you can program the line speed to be whatever you want it to be.

To gain 1000 feet in 20 seconds, the line speed needs to average 34 MPH. To do it in 30 seconds, it needs to be 25 MPH. One could incorporate a line angle sensor on the line guide arm and adjust the speed of the line automatically on the go.

As soon as we go with a brushless motor and controller and a microcontroller there are so many more things you can do to optimize the system for proper launches. For those that aren't aware, the steam catapult systems on aircraft carriers are programmed for every aircraft they launch. Why should our glider launch systems be any different ?

[tonyestep]

To gain 1000 feet in 20 seconds, the end of the line has to ascend at a rate of 50 ft/sec, or 34 mph. But that is not the same thing as the line being pulled in at 50 ft/sec. The end of the line is in effect climbing a ramp. How far it climbs for a given horizontal travel depends on the steepness of the ramp, i.e. the flight angle of the plane relative to the line. The thing to regulate with the microcontroller might be line tension. You can figure out the allowable pull (for example, F3J planes are built to withstand 150 lb pull, F3B to withstand 200 lb), then crank the winch fast enough to maintain that through the launch.

[rogerflies]

I spent a bit of time thinking about having a winch on the far side of the field, and I pretty much gave up on the idea.

It would work fine IF you flew straight up the over the winch so the line was always 90 degrees to the drum axis with no crosswind. Once you fly off to one side, the line starts to pile up on that side of the drum. A crosswind would also push the line to one side of the drum.

So you'd still need a pulley to keep the line at 90 degrees to the drum. It could be in front of the drum, but that reduces the effective width of the field. The line might also get tangled on the pulley/stake if it fell between the winch and the pulley. If the pulley is behind the winch, the line will get caught on the winch at the start of a launch and during a retrieve.

I suppose you could put the winch off to one side with the pulley 50(?) feet away. The ground line would be at (or close to) 90 degrees to the air line. The anchoring of the pulley could be a problem, since the direction of pull is going to change considerably during the launch. The pulley is going to have to have a great deal of freedom in how it moves around

Roger

[rogerflies]

That motor sure is pretty!!

http://www.hobbycity.com/hobbycity/store/catalog/C80-100-A.jpg

I don't see anything in the specs about how many poles it's got. The controller gives some info on maximum motor speed according the the number of poles:
Max Speeds;
2 Pole: 210,000rpm
6 Pole: 70,000rpm
12 Pole: 35,000rpm

Is there any info available on how it's going to perform at much lower speeds with high power input?

Roger

[gyrokiteguy]

To gain 1000 feet in 20 seconds, the end of the line has to ascend at a rate of 50 ft/sec, or 34 mph. But that is not the same thing as the line being pulled in at 50 ft/sec.If you assume the glider goes up at an average of 45 degrees, then it is. Lets say we start the tow with 2000 feet out. And we end the tow directly overhead of the winch at 1000 feet. We had to pull in 1000 feet of line to do that. Obviously the end of the line itself is moving faster, but that is because the glide of the glider is moving it.

The actual distance the glider travels, if we assumed a straight line which it IS NOT, would be 1414 feet, for a velocity of ~70 feet per minute.

If we have a less effective tow with a lesser angle then the line has to move faster. If we start with 2500 feet out and end up 1000 feet overhead of the winch, we need to pull in at 1500/20 = 75 feet per minute.

The end of the line is in effect climbing a ramp. Its actually an arc of decreasing radius.

How far it climbs for a given horizontal travel depends on the steepness of the ramp, i.e. the flight angle of the plane relative to the line. Yes.

The thing to regulate with the microcontroller might be line tension. You can figure out the allowable pull (for example, F3J planes are built to withstand 150 lb pull, F3B to withstand 200 lb), then crank the winch fast enough to maintain that through the launch.

Line tension will be proportional to torque which is proportional to the radius of the line on the spool and the motor current. Its pretty easy to regulate it.

[gyrokiteguy]

That motor sure is pretty!![quote]
:smile: Pretty light compared to a starter motor and 12V battery.

[quote]
I don't see anything in the specs about how many poles it's got. The controller gives some info on maximum motor speed according the the number of poles:
Max Speeds;
2 Pole: 210,000rpm
6 Pole: 70,000rpm
12 Pole: 35,000rpm


I'd guess in the 15 region. The Kv is 180 rpm/volt, so at 48V it will run 8640 RPM. The controller has lots of capacity to handle it speed wise.


Is there any info available on how it's going to perform at much lower speeds with high power input?

Nope.

Torque will vary directly with current. Motor speed will vary with voltage.

It says 150A maximum, but one could probably pull more if the voltage was dropped, ie it was running slower. Commercial brushless motors have a "constant power" portion of the curve ie when voltage/RPMs fall, the current can climb up, up to a certain maximum current and then they have a max torque, increasing power portion.

If this motor doesn't provide enough torque, you can add a second one onto the other side of the output shaft because it goes straight through the motor. Or you could add another motor on the other side of the drum. Or both. 28 Kw winch, anyone ?

[rogerflies]

Looking at the speed controller:
http://www.hobbycity.com/hobbycity/store/catalog/KF150A-1.jpg

I see two three-wire servo-type leads going off to the right. Normally, one must go to the throttle channel on a receiver. What's the other one for? USB connector?

How will the foot pedal be connected to the controller? I guess you could use a servo driver similar to this:
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXWGJ7&P=7

I don't have any experience with electric planes, so I'm trying to get an idea of what I'd have to buy to try out your idea. So far, the list includes:

motor $150
controller 100
two 12-volt batteries 75 (I've already got one)
safety switch (on hand)
servo driver 25
cooling fans (I've got two out of computer power supplies. Are they big enough?)

What else??

Roger

[gyrokiteguy]

Looking at the speed controller:
http://www.hobbycity.com/hobbycity/store/catalog/KF150A-1.jpg

I see two three-wire servo-type leads going off to the right. Normally, one must go to the throttle channel on a receiver. What's the other one for? USB connector?
I don't know.

How will the foot pedal be connected to the controller? I guess you could use a servo driver similar to this:
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXWGJ7&P=7

Either use something like that or a micro controller would read the foot pedal and drive it.

I don't have any experience with electric planes, so I'm trying to get an idea of what I'd have to buy to try out your idea. So far, the list includes:

motor $150
controller 100
two 12-volt batteries 75 (I've already got one)

2 to try it out, 3 or 4 to run it at full power. The motor needs 48V to run at full power.

safety switch (on hand)
servo driver 25
cooling fans (I've got two out of computer power supplies. Are they big enough?)

Probably. I don't even know if they will be needed. The motor will only run at full power for ~10 seconds on a tow.

What else??
Drum, bearings, etc.

[rogerflies]

If I understand correctly, the speed controller needs to be returned to idle each time the power to it is turned off and back on. Is there any way to disable that feature? Could a time delay be be incorporated so you had several seconds of off time before a complete reset was needed?

I was thinking about setting the speed controller for the desired launch power, and holding the pedal down for the entire launch. However, that wouldn't work if you let off the pedal. The motor wouldn't start running again until the controller was returned to idle and then advanced.

Even with the constant speed engine-driven winch, I often get off the pedal during the launch if the plane looks like it's going too fast as the result of a gust.

I don't want to connect the pedal directly to the servo driver so it moves with the pedal. I just don't think it would last very long. Expecting people to learn to use the pedal like an accelerator is a real stretch in my opinion, too.

What did you have in mind for the interface between the pilot and the controller?

Roger

[gyrokiteguy]

If I understand correctly, the speed controller needs to be returned to idle each time the power to it is turned off and back on. Is there any way to disable that feature?

Could a time delay be be incorporated so you had several seconds of off time before a complete reset was needed?
I don't know on either count. I'd have to look closer at it.

Here is a page on servo driving basics.
http://www.geocities.com/bourbonstreet/3220/servobasics.html

I think the motor controller speed would go to zero if you put the servo output to DC, ie 0%. But I am not sure. Someone would have to test out the controller.


I was thinking about setting the speed controller for the desired launch power, and holding the pedal down for the entire launch. However, that wouldn't work if you let off the pedal. The motor wouldn't start running again until the controller was returned to idle and then advanced.

Why wouldn't it work ? I'm thinking of having the switch on the output of the pulse generator, not depowering the pulse generator or the motor controller. See below.

Even with the constant speed engine-driven winch, I often get off the pedal during the launch if the plane looks like it's going too fast as the result of a gust.

That makes sense to me.

I don't want to connect the pedal directly to the servo driver so it moves with the pedal.
Did you mean rheostat here ?

I just don't think it would last very long. Expecting people to learn to use the pedal like an accelerator is a real stretch in my opinion, too.
I am not sure about the later. It seems to me we can control cars and sewing machines that way. Maybe for beginners we could just set a max and then leave them pin it ?

What did you have in mind for the interface between the pilot and the controller? A variable speed pedal. An on/off pedal would be fine too.

Here is how I would set it up for on/off operation if I were you. I would use the servo pulse generator you found. I would put a single throw dual position switch on the foot switch and connect the center terminal to the servo wire that goes to the controller. I'd connect the top terminal to the signal that comes from the servo pulse generator. I'd connect the bottom terminal to ground.

The power and ground wires from the servo pulse generator pass right through to the controller with the exception of connecting the ground wire to the bottom terminal as mentioned above.

So in one position the switch will connect the servo generator pulse to the controller. This should have the effect of running the motor at the speed one sets on the servo generator box.

In the other position the servo signal will be connected to ground. This should have the effect of stopping the motor. Ideally one would use a 1ms pulse, but we don't have one handy. Hopefully the motor controller won't complain at having a 0 ms pulse, ie DC.

The motor controller will remain powered up the whole time. Thus there will be no reset required.

I am ignoring the issue of switch contact bounce. I don't think it will cause a problem.

It would be very easy to use a microcontroller to read a pedal position and generate the servo signals.