Futaba 2.4 Ghz SAILBOAT winch problems? Solutions? - Page 4 - RC Groups
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Aug 11, 2017, 09:47 PM
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There is a difference in claimed stats and real stats with winches. In your case of needing 9 1/2 inches (240mm) of travel it would take 3.19sec for the drum to take up that line with a 500gm constant load which is excessive for a 1m yacht.

If you are considering a arm winch remember that the manufactures torque figure (may or may not be accurate) is quoted at 1cm from the pivot point. If you use a 100mm arm the torque at the end is calculated by the quoted torque/10. The reference to aligning the line over the length of arm is a good one and saves a lot of stress on the servo.

Search on closed loop winch systems for another way but they are not going to give you a mechanical advantage.

Using pulleys you can get.

twice the speed/half the torque or half the speed/twice the torque

Many ways of installing a winch system.
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Aug 12, 2017, 01:10 AM
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tugboat,

Yes I could use a little more speed on the winch I have, but not at the end points. So I'm useing the TX to slow down the end points in the interest of trying to get more accuracy for going to weather. It is real easy to over sheet in light air. so this is my way of trying to fight the urge to honk down on the sails too fast and too tight for the conditions, Even in the full sized boats I would sometimes sheet in too soon and too hard, It is a natural tendency I guess. The boat will accelerate for a short time but then slow down again if you are pointing too high, and the boat will want to pinch too much if the main and jib are sheeted in all the way and the adjustment is set too tight for the conditions.

So Tonight i took the winch out of the boat and pulled the covers off of it to see if there was anything visible that could cause it to act crazy and I could not find anything at all. No water damage and no burned components. Close tolerance parts and well put together I must say.

Have you tried drum winches before and decided that they were not for you? I know they are a bit slower, but they have more torque for the last inch if you need that.

It would take some doing to go back to an arm servo for this boat. All the internal brackets are set up for a winch right now. They must mount an arm type servo on one side or the other? that would give more room for the arm to be longer and move further.

Have you had any trouble with snagging on things inside the boat with that Hitek?

And how big is the battery? Are your batteries inside a plastic jar?
Aug 12, 2017, 01:18 AM
Registered User
I don't know what you mean by "aligning the line over the length of the arm"? do you have any pictures? and the torque values are all relative and I don't believe anything until I see it for myself.

I think with an arm servo the last few degrees would have a lot more grunt if you had the arm almost pointing towards the bow at the end of the travel. the leverage is much greater there for an arm servo if it is set up that way, but you would need to still make it a 1:2 with a pulley because you need a lot of travel in the line and the arm would only be about 5 inches long max. Am I getting close to reality?
Aug 12, 2017, 01:23 AM
Registered User
For my boat I have to clear the fin box and that requires the arm to be mounted way in the back or way in the front. I think I would prefer the back because of the tendency to nose dive in a downwind puff. So putting any extra weight somewhere would be better off back there.

There was no info in the building plans about an arm winch at all, so I have the feeling that the Bantock designer was favoring winches at the time he designed this Nimbus model.
Aug 12, 2017, 01:34 AM
Registered User
I don';t know how hard it would be to design a linear actuator or at least a self contained endless loop that was servo controlled. That way you could mount it all under the deck and be fairly sure that it would not come apart or get fouled on something. Just put a tension spring in the double pulley or in the line somewhere on the slack side of the loop. If your pulley had a rubber outside liner for the drum and you needed to adjust the throw, you could put a little slack in the loop and put it back in calibration easier than I can mine.

They are also making a toothed belt in small sizes now that runs on a toothed pulley. So that would be a lot simpler than all that string and having two dead ends to avoid.
Aug 12, 2017, 01:43 AM
Registered User
If I have any more trouble with the winch loosing it's trim limits I may have to cook up a clutch or adjustable winch drum. That way I could keep the tension on the loop and just wind the bobbin in the direction it needed to go to get back to the close hauled position with the endless loop. Much better than pulling the winch drum off the servo output shaft and then trying to keep the slack out of the lines while they try to fall off the drum sheaves! Not my favorite way to spend the afternoon!
Aug 12, 2017, 03:14 AM
Registered User
Is it the winch or a component in the radio supplying the winch with information? A calibrated servo tester would help determine which tree you should be barking up. Just mark the tester control to show where the set limits are, after they appear to have shifted, retest. A further thought - is the electronics in the winch getting it wrong or is the drum just moving relative to its output shaft under strain? I've seen an arm do just that after the boss gained a crack during some misuse. It gained the ability to hop over a spline or so.

"Aligning over the length of the arm". Setting things up so that when the servo arm is as close hauled as you want, the line actually runs almost along the length of the arm. The last 45 degrees of travel gives less linear travel of the line, but much more torque. If the space available dictates that there is only one position for the servo to swing the arm, you have to rearrange the line feeding point to suit and still maximise the actual travel.
Just a personal view, but I think drums are much easier, especially shrouded ones. The mount for an arm type needs to be much stronger and stiffer since all of the twisting moment is passed into the mount and whatever the mount fixes to, whereas the drum just pulls in one direction.
Aug 12, 2017, 10:42 AM
Registered User
mfr02,

Those are good questions. The radio is supposed to be supplying the winch with information. This winch, like 99% of all winches is running off of the PWM signals passed to it by the rcvr. And actually, the winch has been working fine except when the RX battery voltage went somewhere south of 4 volts. The old NiCad pack was only a 4.8 volt unit, but it would come off the trickle charger at close to 6.2V so I was thinking that the Nicad was fine. Now I think I was wrong about that.

So I removed the Nicad for a test and hooked up a 4 cell Alkaline pack that I made out of parts I had laying around in the shop. It was running at around 6 volts initially and I hooked it into the RX wiring harness. After that the winch has behaved and not lost it's close hauled physical position point in relation to the deck fittings where the line enters the thru deck pulley.

I also did an inspection of the winch itself last night. It looks fine inside and there is no water or smoke damage that I could see with my jeweler's magnifier and a strong light, so I am assuming for now that the servo itself is OK.

I wish I had a servo tester like you mentioned. If I could get one for under $40.00 or so that would do the job, it would probably be worth it. I don't have any other winch servos that I can swap out with the Futaba S 110, or I would have already done that.

It would also be nice to have an adjustment on the winch drum itself so that you could re-calibrate the close hauled point without taking the drum off of the winch shaft. This would be some kind of a 3 piece stack of parts that would allow both of the sheaves to be independently turned so as to allow the starting position of the loop to be adjusted without loosing all the tension in the system.

As far as the drum slipping on the shaft, I cannot feel any looseness and each time I removed the drum from the shaft it was always engaged with the splines on the servo output shaft so that there was no perceptible play. The inside of the drum center is also splined to match the servo splines.

The gear train on the servo also appears to be in good shape because of the lack of slippage when and if the close hauled limits are ever exceeded.

I am pretty well convinced that all this was due to the low (as low as 3.2v) Rx Nicad battery pack influence on the RX. At one point while on the shore, I was testing and did not know what the RX voltage was, because I was all buttoned up, and the rudder and winch channels (rudder and throttle) were trying to influence each other.

So what you would see is that the rudder would move if the throttle stick was moved.

But why this would cause the close hauled position to shift is still a total mystery right now.
I ran the in-out cycle about 50 times and it always returned to the limits that I had set in the TX, so except for maybe an 1/8" of change due to the way the string lays in the pulley grooves on the winch drum it has not changed again.
Aug 12, 2017, 04:56 PM
Registered User
Just got my new 5 cell Lipo batteries and tried them out on the water. No problems now! And the Rx/TX is relaying the RX battery voltage back to me now, so this problem should not have a chance to re-occour

Maybe the 2.4 is not so bad after all?

Thanks for all your help and suggestions!

Now what is the best way to do a single battery? With the winch wanting it's own supply do I need a BEC? I don't know anything about Bec's so this might take a while.
Aug 12, 2017, 05:14 PM
Registered User
hiljoball's Avatar
A 'Y' harness is the usual method. One leg to the battery, one leg to the winch, and one leg to the Rx.


example

https://hobbyking.com/en_us/twisted-...24awg-5pc.html

John
Aug 13, 2017, 02:54 AM
Registered User
I assume you mean running Rx and both servos off the same battery.

Plug your new battery into the "bat" port of the Rx or any unused channel. As I said before the battery pins are all commoned in the Rx. Then plug your servo plugs into the ports you use as usual. Port number depends on what Mode you are using.
Aug 13, 2017, 03:38 AM
Registered User
Her are a couple of more answers to some questions you posted.

First the method of aligning the winch line on an arm winch when the booms are fully hauled in that mfr02 referred to. Refer to the attached photo which is just a mock up but you can see that there is no rotational force from the winch line on the arm. Even with the booms let out a bit there is little force. The maximum force is when the arm is at 90 degrees to what shown.

I don't use a waterproof battery holder but rely on a dry hull and water proofing of the battery pack itself if there is any water ingress. I make my own battery packs and each is designed to suit the yacht it is going in. Pictured is a pack that is designed to lay on the centre line of the hull.

If you want a bit more speed and slightly less torque you can look at getting a slightly larger drum for the winch servo.

I use closed loop and tensioned winch drum systems but are going to probably use a tensioned arm system in the future.
Aug 13, 2017, 10:05 AM
Registered User
Quote:
I wish I had a servo tester like you mentioned. If I could get one for under $40.00 or so that would do the job, it would probably be worth it. I don't have any other winch servos that I can swap out with the Futaba S 110, or I would have already done that.
Servo testers are cheap -
https://www.ebay.co.uk/i/28258573185...1899408&crdt=0
Obviously, fleabay knows where I am and stuff gets priced accordingly, but unless the dollar has taken an almighty dive, your cost should be achievable.
Aug 13, 2017, 01:48 PM
Registered User
I have a servo tester on order. https://www.ebay.com/i/222257107374?chn=ps&dispItem=1

I hope that one will work. The price is right anyway. I don't know if it can "read" the output of the rcvr and give a digital count of the signal being fed to the servo, but at least it can command a given pulse width count out to the servo and if the servo does something strange with the info, you know the servo is questionable.
Aug 13, 2017, 02:02 PM
Registered User
Tugboat,

Those battery packs have to be the ultimate in low CG! (as long as they don't get wet)

And with the very small cross section you probably can snake them down into the bilge thru a fairly small opening in the deck?

Are you charging them "in place" or pull them out of the boat to charge them?


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