Thread Tools
May 16, 2011, 09:31 PM
Registered User
Don't get too fancy. If you aren't handicapped you already own an ok power source for a winch, and if you have an old bicycle you have the transmission and the drum. There's a video someplace of guys launching by winding the line in with a converted bicycle. Looks like it works just fine.
Sign up now
to remove ads between posts
May 18, 2011, 08:42 AM
Registered User
I saw the bicycle powered winch but I have a few problems with it. A very fit cyclist can produce 5/8 HP, we are likely to bring less than 1/2 hp to the table....and the setup looks to be more hassle than that for a regular winch. More importantly, when a sailplane pops off early on launch and starts into that kamikaze loop, I wouldn't want to be the person stuck sitting on an exercise bike in the impact area!
May 18, 2011, 06:02 PM
Proud member of LISF and ESL
I think the RCSD article shows that you could launch HLG with such a winch. Perhaps even a very light 2M, like a Gentle Lady or an Easy Glider. But I doubt it would pull much more than that.

Based on the battery pack recommendations you are probably talking about 40 amps at 14V, max.

That is about 480 watts.

We have measured the draw of the club winches. Under full pedal taking a Supra up into a 10 mph wind we were pulling 500 amps, or about 5,500 watts. So your mini winch would be about 8% of that.

I have also see meters reading winches at about 300 amps for tapped launches of lighter gliders. But that is still about 3300 watts. That puts your mini-winch at about 15% of that number.

8-12 ounce HL glider? Probably, but not real strong and the line drag on the ground might have a significant impact. But perhaps adequate for a HL.

I would put out a light hi-start that can provide 4 pounds of pull instead. Dynaflite has an up-start with 25 ft of light tube and 100 feet of line. I think that would be a better approach. With a light model it might take 150 feet of line.
Last edited by aeajr; May 18, 2011 at 06:10 PM.
May 18, 2011, 11:00 PM
Registered User
It's not necessary to pull anywhere NEAR 500 amps to launch a Supra. Maybe to get a great zoom, I suppose. My own winch is a 12V wind, and not too hot at that. If it's like the 6V winds except for nominal voltage, I bet it pulls several times less amps, but it can still launch an 85 ounce, 134 inch span glider just fine.
May 19, 2011, 04:21 AM
Proud member of LISF and ESL
Quote:
Originally Posted by lincoln
It's not necessary to pull anywhere NEAR 500 amps to launch a Supra. Maybe to get a great zoom, I suppose. My own winch is a 12V wind, and not too hot at that. If it's like the 6V winds except for nominal voltage, I bet it pulls several times less amps, but it can still launch an 85 ounce, 134 inch span glider just fine.
No one said it was. That was used as an illustration of a maximum load launch that we tested. I would say 300 to 400 is far more typical and that would likely be pulsed.


If you averaged it over the launch, maybe 250 to 300 amps for a typical 3M glider. Maybe 100 to 150 for a light 2M glider, like a GL. All WAGs of course.

But even at that you are talking about 1100 to 1650 watts on the 2M glider. The mini-winch is still only about 30% - 40% of that.

So, yes, fine for a HL It would probably take up a very light 2M glider at a not too agressive angle if you floored it for the entire launch of a 25 ounce GL or an Easy Glider.
May 19, 2011, 05:35 AM
Registered User
Neil Stainton's Avatar
Thread OP
I think the traditional direct drive starter motor winch is very inefficient. Looking at the F3J two man tows at the Wilga Cup event recently, I think the towers would have supplied at most 1hp combined, so only 750W. Say the HobbyKing winch can take a 5S pack, and 70A for the short time required, even if it is only 70% efficient the power out would be about 1000W, which may be enough for a larger model.

Neil.
May 19, 2011, 08:20 AM
Registered User
Quote:
Originally Posted by theghosttanker
I saw the bicycle powered winch but I have a few problems with it. A very fit cyclist can produce 5/8 HP, we are likely to bring less than 1/2 hp to the table....and the setup looks to be more hassle than that for a regular winch. More importantly, when a sailplane pops off early on launch and starts into that kamikaze loop, I wouldn't want to be the person stuck sitting on an exercise bike in the impact area!
That's assuming the operator is too dumb to shift it to an efficient range. I'm sure most of the power from a regular winch is wasted. Certainly a lot is wasted when it's bogged down. I'll bet with a proper, variable transmission, a small motor could work impressively well for a winch.
May 19, 2011, 08:59 AM
Proud member of LISF and ESL
Neil. Build it!

What will you use for the drum?

Line?

Bearings - Hummm - what kind of bearings does it have. That is designed for a different kind of load than a winch would impose. Wonder if that would be an issue?


Build it!

Inquiring minds want to know.
May 19, 2011, 02:15 PM
Registered User
mhodgson's Avatar
It really all depends on the sort of launches you want.
I can remember hand towing models where in anything more than a breeze you walked or even ran towards the model. Quite often, even with stronger models, you just stood still after the initial run and kitted the model up.

As for the bearings- if the drum is mounted on two bearings it doesn't matter what the bearings are in the motor case as the drum takes the side (line) loads, the motor only turns the drum.

I gues the real answer is to build one and see. You could always add a more powerful motor if it does not work.
May 19, 2011, 07:57 PM
Registered User
Mark Miller's Avatar
I would say that a comparison between a two man J tow and a winch launch is not exact. The missing component is the stored energy in the mono prior to launch. It takes a lot to stretch that mono and hold it until launch. The towers do their best to retain the stored energy but I do not think they can add an more energy into the equation. Really a J tow is more like a high start launch with a mechanism for keeping the energy in the system as long as possible meaning the towers. Even a B launch there is lots of energy stored prior to launch in the mono unlike TD.

A small motor is a good thing if you are looking for a high start like launch. Want a competition style launch you will need power. Yes you can gear the system but there is a trade off between torque and line speed.

On this side of the pond where we use braided nylon you need the high power motors to keep the power up as there is very little energy stored in the braided line unlike mono. Our launch systems are like they are because they work and no one has come up with better alternatives. If they had we would be there.
May 19, 2011, 10:46 PM
Registered User
Technology doesn't work like that. Somewhere, someone may have a significantly better system that they're not promoting. We all use what we know about.
May 20, 2011, 06:19 PM
Registered User
Mark Miller's Avatar
You would think that if someone had a better system in the past 30 years we would know about it. And be using it. Since no one is building a commercially available American style TD winch there is a market ready and waiting for the next best thing.
May 20, 2011, 09:59 PM
Registered User
Consider this:

Carbon fiber became widely available in the '80s, but it was close to 20 years before dlg's became popular. And I bet that dlg's could have been feasible without it! Maybe not up to today's standard, but far beyond what was common then.

The full scale sailplane world discovered fast airfoils many years before they became common in rc.

I'll bet someone had a fully operational winch brake system back when I started this hobby, but the brakes only became popular some years later. Ditto re retrievers.

Composite construction took a long time to take over the RC sailplane world, even though full scale had gone over quite a while before.

That market is pretty small. If it was several thousand per year, I bet we'd see a great deal more sophistication in winches, and far lower prices.

A new winch design has to become popular enough for some critical mass of people to accumulate experience before it really spreads. Chicken and egg problem.
May 20, 2011, 10:02 PM
Mongo like wind. Wind Good.
V1VrV2's Avatar
Quote:
Originally Posted by Mark Miller
You would think that if someone had a better system in the past 30 years we would know about it. And be using it. Since no one is building a commercially available American style TD winch there is a market ready and waiting for the next best thing.
Dang Mark, I am with you...

I have built TD winches and F3B winches and It will only take the right guy with access to CNC shop equipment and a good solid design (this is a VERY subjective area, as I have found out) to make a good solid winch design. Price point is the key. Most Laymen think winches are just a DC motor attached to a drum. It's much more complicated than that. Our hobby requires a VERY specialized piece of equipment that requires the skills of a machinist capable of tolerances of +/- .001". Not only that, but most builders find that the purchasers/users are extremely critical of their design. One guy says he wants small and light, the other says he wants "line speed", yet another says he wants torque. Most say they just want something that fits every criteria and is "cheap". I bowed out of building SASS winches because (partially) I had to deal with a comittee where everyone had a very different opinion of what was important and I just gave up. I don't think this will ever be a very popular area of manufacture for skilled suppliers because of these reasons. For those that do build and sell winches, be prepared for merciless critiqing from your peers as everyone wants something different.

Hey, I'm gonna go fly now! I love my winch. perfect for me...

L8TR

Tony
May 20, 2011, 10:07 PM
Registered User
I've had that even without trying to sell the winch I built. They won't even try it.They say it's too weak and the switch is weird.


Quick Reply
Message:

Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Is Budget Austerity Modern-Day Hooverism? MtnGoat Life, The Universe, and Politics 0 Apr 25, 2011 02:54 PM
Off Site Call of Duty: Modern Warfare 2 Xbox 360 Wattsup23 Non R/C Items (FS/W) 1 Apr 24, 2011 07:22 AM
Link ParkZone F4U on TV Series (Modern Family) CClark Electric Plane Talk 8 Apr 19, 2011 11:05 AM
Discussion Modern Mega DD equivalents opualuan Power Systems 15 Apr 14, 2011 03:13 PM
Rant Inexpensive home-brew winch? Is it possible? RRRr! e-sailpilot86 Thermal 24 Dec 08, 2004 10:41 AM