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Author Topic: Sail servos  (Read 2275 times)

hover tim

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Sail servos
« on: December 23, 2007, 08:58:11 AM »

Do sail servos have more movement then normal servos as i am building a hovercraft with a well deck ramp and i need to move the ramp up and down folow this link for a picture http://www.flickr.com/photos/19759955@N07/2095151955/
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tigertiger

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Re: Sail servos
« Reply #1 on: December 23, 2007, 09:19:06 AM »

Sail servos geenrally have more torque. I think many standard servos are about 3kg/cm torque.
Sail arm servos can be between 7kg/cm and 25kg/cm

There are sail arm servos and sail winch servos.

Most sail arm servos only have 90degrees of movement, some have 140 deg. Howver all servos can be modifed to give more turn.
I am not sparky, so I could not tell you how it is done, but there are otehr thread on this form. Give it a couple of hours and you will have more answers on how, if you want.

Sail winch servos have a a drum that turns up to about 3.5 turns. Bigger drum means more line pulled in.


But if you are using a sail arm, you can pull more cable by haveing a longer servo arm attached.

Looking at your picks 90degrees is plenty. and I doubt you would need the extra torque of a sail arm servo.


If you do a sketch of how you plan to open/close the ramp it would help. Are you thinking of running a cable system, directyl attach servo to ramp, or what?
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HS93 (RIP)

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Re: Sail servos
« Reply #2 on: December 23, 2007, 10:50:02 AM »


A simple way to do it is to use a old  standard servo, remove the stops inside and on some you have to play with the pot and fix the gear of a rack and pinion on the top and use a rack , you can then get as much movement as you want. I did something like this some years ago and when fixing the pinion I used a small servo disk and a long bolt with a spring so as to form a clutch so you don't need  to worry if you go to far.

Peter


http://www.maplin.co.uk/Module.aspx?ModuleNo=11948&C=Froogle&U=11948&T=Alias&MA=pinion
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FullLeatherJacket

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Re: Sail servos
« Reply #3 on: December 23, 2007, 12:37:49 PM »

Tim
Another method might be to use a small motor and gearbox (e.g. a servo with no electronics), operated by a switcher or micro speed-controller and controlled at each end with miniature limit-switches and diodes. There's an article in the latest Model Boats which features a similar arrangement for the sail winch in a Lilla Dan. I've tried this system in a test-rig, using both an ESC and a switcher, and it works a treat. PM me if you want further details; it's not rocket-science!
FLJ
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hover tim

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Re: Sail servos
« Reply #4 on: December 23, 2007, 12:59:06 PM »

the following is a link to some pics of the origonal hand winch set up i would like to replecate this if possible but using a sail servo but not sure how

http://www.flickr.com/photos/19759955@N07/
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HS93 (RIP)

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Re: Sail servos
« Reply #5 on: December 23, 2007, 02:56:55 PM »

same way , If you use the same set up for the servo as described you may have to wrap the rope around a few more times
Peter
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hover tim

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Re: Sail servos
« Reply #6 on: December 23, 2007, 04:37:12 PM »

you have hit the nail on the head there just to cheak this is not a modifid servo or is it
 so wheres a good shop o get this stuff as my local shop is a plane shop so they do not stock much on boats
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HS93 (RIP)

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Re: Sail servos
« Reply #7 on: December 23, 2007, 07:41:41 PM »

unfortunately it would have to be moddedunless you could get a large gear on the servo and a small gear on the drum for the rope and a big enoughdrum within scale to pull enough rope. if you incorporated another gear it would be no problem with an UN modded servos where not talking about needing a lot of power to lift the door what you need to do is work out how many turns you need for the drum and with the rope and that will tell you the gear ratio ( don't forget to double it as your servo only turns 180 ish deg)

Peter
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tigertiger

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Re: Sail servos
« Reply #8 on: December 24, 2007, 02:27:26 AM »

Another method might be to use a small motor and gearbox (e.g. a servo with no electronics), operated by a switcher or micro speed-controller and controlled at each end with miniature limit-switches and diodes. There's an article in the latest Model Boats which features a similar arrangement for the sail winch in a Lilla Dan. I've tried this system in a test-rig, using both an ESC and a switcher, and it works a treat. PM me if you want further details; it's not rocket-science!
FLJ

FLJ. Are you going to do a kit then?   :) O0
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FullLeatherJacket

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Re: Sail servos
« Reply #9 on: December 24, 2007, 08:38:01 AM »

FLJ. Are you going to do a kit then?   :) O0

I'd be happy to supply a drawing and the requisite diodes and microswitches to suit one of our exisiting ESCs or switchers, but I haven't the heart to sit gutting servos! You can buy them for the square root of naff-all on E-Bay, I understand, or try Steve Webb (The Servo Shop) for truly silly prices on cheapo micro servos.
I'll try to remember to put the diagram on the new ACTion website, which is getting closer by the hour  8)
FLJ
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