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Author Topic: Sail winch creep?  (Read 741 times)

tonyH

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Sail winch creep?
« on: August 15, 2021, 04:15:47 pm »

Hi,On a current project I have 3 functions running on a single Tx channel. They consist of 2 micro servos and a standard servo sized sail winch. The end point at both ends of travel are determined by one of the micro servos and the EPA has been set on the Futaba 2.4 Tx. The second micro servo and the sail winch have a certain amount of latitude. Both micro servos move smartly and consistently but the 7 turn sail winch turns at about 1 rev per second for the first 5-6 turns then slows to a crawl for the last turn. Is this normal or is it likely that the end point will vary depending on, for example, battery voltage to the Rx? The ESC is one from the late DM and is without BEC, so the power is 4xAA sized NiMh.I've tested the setup a few dozen or so times and all seems well but if it changes, it's one of those situations where strings go twang or it pulls a mast or two over. :embarrassed:
Cheers
Tony
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malcolmfrary

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Re: Sail winch creep?
« Reply #1 on: August 15, 2021, 09:38:02 pm »

The way servos work is that they take their position information from the internal post and compare that with the signal coming from the radio.  If one is different from the other, the electronickery tells the motor to drive the pot to match up.  As the two numbers get closer, the motor speed drops, mostly to prevent overshooting and hunting. 
With a multi-turn winch, this is much more noticeable, and probably what you are seeing.  Unless there is a great deal more load at that end of the travel.  Either a load imposed by the effects of the sails or maybe, if pulling in, things getting a bit crowded between drum and shroud.  Shrouded drums seem to be intended for line about 0.5mm, the more turns, the thinner the line needs to be.
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tonyH

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Re: Sail winch creep?
« Reply #2 on: August 16, 2021, 09:47:46 am »

Thanks Malcolm,The winch fits the profile you mentioned, i.e. it's shrouded with constant load and the line is about the 0.5/0.6mm you mentioned so, hopefully, all should be OK.The installation is rather like cable cars where as one line gets hauled in, the other goes out so both end stops are critical within a smallish tolerance but in this case I can't have a continuous loop.
Thanks again
Tony :-))
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