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Author Topic: Dumas Star30 Which winch servo? need advice pls  (Read 304 times)

danielcardona

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Dumas Star30 Which winch servo? need advice pls
« on: December 01, 2017, 01:08:33 PM »

Hello everyone


 I started a thread in this forum (beginners section) of my Dumas Star30 build, So far i Think it's going Ok but soon enough I need to choose a winch servo for it.


I have a dilemma with these two:


Hitec HS-765HB


Hitec HS-815BB


Which one should be enough for my star30?


Regards
Daniel






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xrad

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Re: Dumas Star30 Which winch servo? need advice pls
« Reply #1 on: December 04, 2017, 12:53:18 AM »

Either one will work. For 5$ difference get the BB. It has almost x2 amount of torque.  I use one of the original gearboxes in my S30...works fine, don't know the torque.  I use a 5cell 6v 1200mah 'hump' nimh pack. 
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roycv

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Re: Dumas Star30 Which winch servo? need advice pls
« Reply #2 on: December 04, 2017, 10:28:29 PM »

Hi there are some high powered standard size servos now that will easily do the job and they are cheaper as well.
Roy
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danielcardona

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Re: Dumas Star30 Which winch servo? need advice pls
« Reply #3 on: December 05, 2017, 01:43:44 PM »

Hi there are some high powered standard size servos now that will easily do the job and they are cheaper as well.


Roy


You mean I can use any high torque servo that I can find? I always thought that servos dedicated to sails have more throw compared for example to a standard one used on model aeroplanes.
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roycv

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Re: Dumas Star30 Which winch servo? need advice pls
« Reply #4 on: December 05, 2017, 04:07:24 PM »

Hi No problem as long as you are using an arm for the sails.  Just construct an extension arm and attach it to a servo top and screw it on.  You will have 90 degrees movement which can sometimes be extended.
That is what I do for small yachts.
regards Roy
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xrad

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Re: Dumas Star30 Which winch servo? need advice pls
« Reply #5 on: December 05, 2017, 07:53:32 PM »

regular servos (90 degree) have less throw than 'winch' type servos. Depending on  your Tx, you can adjust up to 150% of throw in each direction on a standard servo, which may be enough with arm attached.  For a winch servo, you would have to reduce throw to maybe say 25% to get 180 degrees of arm tip motion. The winch servos use a different potentiometer output to determine position, in other words, they can do (0 to 6.3) x 360 degrees (depending on model of servo and Tx setting). But not all Tx's can do this.  I use a Spektrum Dx6e which does NOT have a spring return lever on the 'throttle' stick (up down left side) which is used for winch control, thereby 'holding' the winch at correct spot. And it has easy adjustability 0-150% servo travel.

I just set up a turnigy 14kg 'winch' servo to do 6+ turns for a large sailboat(xrad's ec12). Tx set at 150% travel for servo.  If i set it at 75% throw, it will do 3 turns, etc...
https://hobbyking.com/en_us/turnigytm-tgy-6114md-digital-sail-winch-servo-drum-type.html

Or you can modify a standard digital servo by adjusting the resistors for the pot:
https://learn.adafruit.com/modifying-servos-for-continuous-rotation/overview

Basically,  the PWM Rx 1-2msec signal tells the servo where it needs to be, and the potentiometer in the servo keeps it there. You fool the servo by altering the pot signal.
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danielcardona

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Re: Dumas Star30 Which winch servo? need advice pls
« Reply #6 on: December 06, 2017, 07:40:19 PM »

so standard servos have 90 deg of travel, winch servos (drum) have 360 and sail servos (those with a very long output arm) have 180 deg. Am i correct? thanks for the link to modify a standard digital servo, a very interesting read.

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xrad

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Re: Dumas Star30 Which winch servo? need advice pls
« Reply #7 on: December 07, 2017, 12:35:02 PM »

Standard: 90 degree


Winch: (0-360 degrees) x 1-6+ turns  = 0 to ~ 2160 or more degrees (varies by model/manufacturer/settings)


'Arm' servo = varies by manufacturer , could be 90, 140, 180...etc
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roycv

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Re: Dumas Star30 Which winch servo? need advice pls
« Reply #8 on: December 07, 2017, 12:51:00 PM »

Hi just to clarify using a standard servo as a sail arm winch.  I fit the arm on so that it is extended in line with the sail sheeting when the sails are fully extended. 
This stops an unexpected gust of wind pulling the servo arm against the gears etc. 
I find 90 degree movement fine, the pull on the sheets can be doubled by fixing a pulley sheeve on the servo arm.
In an old yacht I have built when the standard servos were less powerful I have 2 servos, one for the main and one for the jib.  The servos work together from a Y lead connected into a single receiver socket.  The main and the jib should go in and out in parallel.  This means that the sheet connection to the jib boom and the main boom should be of equal distance from the pivot point or gooseneck fitting.
Most operators have the sails on the left hand stick, pushing it away from you is 'sails out' and pulling it towards you is 'sails in'.
Hope this helps,
regards Roy
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danielcardona

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Re: Dumas Star30 Which winch servo? need advice pls
« Reply #9 on: December 07, 2017, 05:49:33 PM »

Hi just to clarify using a standard servo as a sail arm winch.  I fit the arm on so that it is extended in line with the sail sheeting when the sails are fully extended. 
This stops an unexpected gust of wind pulling the servo arm against the gears etc. 
I find 90 degree movement fine, the pull on the sheets can be doubled by fixing a pulley sheeve on the servo arm.
In an old yacht I have built when the standard servos were less powerful I have 2 servos, one for the main and one for the jib.  The servos work together from a Y lead connected into a single receiver socket.  The main and the jib should go in and out in parallel.  This means that the sheet connection to the jib boom and the main boom should be of equal distance from the pivot point or gooseneck fitting.
Most operators have the sails on the left hand stick, pushing it away from you is 'sails out' and pulling it towards you is 'sails in'.
Hope this helps,
regards Roy


Hi Roy, thanks for chime in. The pulley sheeve that you were refering to, is it a kinda of mechanical advantage? Would love to see some photo's or drawings explaining that. Many times I see photo of builds showing the radio installation inside a sailboat and its fascinating how many builders come up with different ideas. Seems everyone have there personal setup. I myself if I didn't had any instruction photo's what to do in build I really dont know were to start :embarrassed: . Probably I would just copy my dragon force RG65 boat setup.


Regards
Daniel
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roycv

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Re: Dumas Star30 Which winch servo? need advice pls
« Reply #10 on: December 08, 2017, 12:28:45 PM »

Hello Daniel, I think the best thing is to read through this explanation.

http://www.explainthatstuff.com/pulleys.html

If you have a problem perhaps send me a PM.
kind regards Roy
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