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Author Topic: More travel on a Futaba servo  (Read 1834 times)

Bluechrisp

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More travel on a Futaba servo
« on: August 07, 2010, 10:46:01 AM »

Hello all,

I'm trying to work on a scratch built tug, I am trying to get more play on the futaba servo, is there a way to do this, to allow the thruster to move around until the prop shaft.   {:-{

Any help will duely be received with thanks.  :-))

Chris P
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malcolmfrary

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Re: More travel on a Futaba servo
« Reply #1 on: August 07, 2010, 10:54:17 AM »

Use pulleys instead of arms and rods.  With a larger pulley on the servo and the smaller one on the thruster you get all the rotation you can imagine.
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Mankster

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Re: More travel on a Futaba servo
« Reply #2 on: August 07, 2010, 11:30:50 AM »

You can buy a commercial ' servo strecter' or do the mod yourself http://www.rcexplorer.se/page14/180servo/180servo.html

TAG

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Re: More travel on a Futaba servo
« Reply #3 on: August 07, 2010, 11:58:27 AM »

I have just bought an Action electronics unit P96 "servo morph" which works well. It will extend the servo travel up to 180 degrees and also adjust the speed of travel. Depending on the make of servo you may have to remove the travel limit stops.
Tim
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Bluechrisp

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Re: More travel on a Futaba servo
« Reply #4 on: August 07, 2010, 04:27:25 PM »


Hello all,

Thank you for the top tips, the Servo Morph looks good, the tug on trials did turn abit fast so could go down that route, and the drum idea could be used for something else I have planned.

Always good to stick Qu's on the forum. 
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keven64

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Re: More travel on a Futaba servo
« Reply #5 on: October 08, 2010, 12:26:05 PM »

...there is ANOTHER way to go - which I've successfully done on a few servos of different manufacture...

You will need - a multimeter/ohmeter, soldering iron & solder (!), and various small resistors.

Essentially - this is the 'Servo Morph' in a DIY form - but without the option to slow the servo transit speed.
If tht IS a requirement - then buy a P96 - http://www.action-electronics.co.uk/mixers.php

Assuming that a DIY 'option' is OK for what you want... ( I only want more sheet travel in Footy yachts )

Choose the servo that you want to 'travel more'...!
Make a hole in the centre of a square of card and place it over the servo output shaft - and secure it with small pieces of tape.

Fit a double output arm to the servo - then operate the servo with your transmitter and mark the card with three lines \ | / to indicate the two extremes of travel and the centre position of the arm. Leave the stick trim centred.

Turn everything off and unplug the servo from the receiver - then remove the servo screws and the bottom portion of the case.

Pull out any sticky-foam packing/insulation - and find the three wires connecting the feedback potentiometer ( directly under the servo output shaft ) to the little circuit board.
 
Carefully separate the three wires so that you have the centre and two outer wires easily recognisable.

With side cutters, carefully snip the OUTER wires - and bare a few mm of wire using your nails...
A hand-tool will go right through...! :o

With the two pairs of bare wire accessible - position the servo output arm carefully to one side to the position marked by the first line \  - and measure the resistance in the first wire that you cut - and write it down on the left of a sheet of paper...

Then move the servo arm to the other line /  - and measure the resistance in the other in the second wire that you cut - and write it down on the right of a sheet of paper...

Now move the servo arm carefully again - back past the 'centre' and the \ line - to a position at around[/b] 80 degrees from the centre.
Again - measure the resistance in the first wire that you cut - and write it down on the left of a sheet of paper...

Now - do the same for the other side.
Move the servo arm again back past the 'centre' and the / line to a position at around 80 degrees from the centre on the other side...
and measure the resistance in the second wire that you cut - and write it down on the right of a sheet of paper...

OK - you will then have two figures on the left of your sheet of paper - and two on the right.
Both sets of figures should be similar...

Deduct the smaller number from the larger for each side of the paper - and you will have a figure for the value of extra resistance required to drive the servo arm to the 'new' position.

Simply choose the nearest resistor value for each side - and solder a small resistor in line with each of the wires you cut.
Wrap the whole lot - wire and resistor at each side - with a little piece of tape, tuck everything in carefully and refit any sticky-foam packing/insulation.

Refit the bottom of the case and a couple of the screws - and try it.
If all is done properly - the servo will move faster than normally - for the stick movement - and will end up at a position farther than before.
Fit the other servos screws - and play ! :-))

150 - 160 degrees TOTAL movement is about as much as you should try for.
I've successfully modified an HS-85MG servo for 170 degrees of movement - but that's the max with metal gears, I'd say.

If you are not confident with 'playing about' with electronics and a soldering iron - or if you value your servos - buy a P96.

Keven. :-)
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