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Author Topic: Servo Stretcher  (Read 3861 times)

Bob_V

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Servo Stretcher
« on: January 21, 2007, 07:54:20 pm »

I need to modify a Hitech HS-765HB servo to operate over 180 degrees instead of the standard 90 degrees. I have been trying to locate a supplier for a servo stretcher such as this:-   http://www.servocity.com/html/180o_servo_stretcher.html  Does anyone have any suggestions?

Bob
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Bob Vaughan

gribeauval

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Re: Servo Stretcher
« Reply #1 on: January 21, 2007, 08:25:43 pm »

Look on page 8 of this PDF file. ;)

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Bob_V

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Re: Servo Stretcher
« Reply #2 on: January 21, 2007, 09:10:03 pm »

Hi Gribeauval

I have that article. In fact I am currently building a Fairwind using that as a building guide. Unfortunately my sail servo appears be a more modern version which uses surface mount technology. The printed circuit board is soldered in and up to now I have not found a way to get at it. This is why I am looking for a servo stretcher.

Bob.
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Bob Vaughan

roycv

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Re: Servo Stretcher
« Reply #3 on: January 22, 2007, 12:34:22 pm »

Hi Bob V, I was interested in the servostretcher from servocity last year but the post and packing is very high.  Maybe if a few guys wanted them an order could be put in to save on postage, but then they have to be sent out again.  Nobody seems to import them.
Regards Roy
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Telstar

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Re: Servo Stretcher
« Reply #4 on: January 22, 2007, 05:24:33 pm »

Hi Bob To get into a hitech servo you need to either unsolder the motor connections 3 of them, or attack from the other end and after opening up the gears push out the motor ( push on the end of the motor shaft/cog) and thus push out the pcb still attached to the motor
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Bob_V

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Re: Servo Stretcher
« Reply #5 on: January 23, 2007, 05:58:05 pm »

I have now got a quote from ServoCity for the Servo Stretcher. The price quoted inluding shipping being $27.90 which converts to about £14.

In the meantime thanks to Telstar I have now got the pcb out and am experimenting with different resistor values to get the nearest to 180 degrees that is possible with my particular servo. Will keep you posted as to the final values I settle on.

Bob.
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Bob Vaughan

Bob_V

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Re: Servo Stretcher
« Reply #6 on: January 26, 2007, 11:39:37 am »

I have now managed to modify my HS-765HB sail-arm servo to give me nearly 180 degree operation. For your interest I ended up with 1k resistor in the red wire and 2k7 resistor in the green wire.

This worked for my transmitter/receiver combination (Hitec Ranger II N transmitter with Hitec HP-2RNB receiver). Other combinations may require different values.

Bob.
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Bob Vaughan

BarryM

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Re: Servo Stretcher
« Reply #7 on: February 07, 2007, 02:05:49 pm »

Can anybody say if this is feasible with a Futaba servo and, if so, in which wires the resistors are inserted?

Thanks

BarryM
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Telstar

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Re: Servo Stretcher
« Reply #8 on: February 07, 2007, 11:25:43 pm »

Hi BarryM
Yes it is possible to do the same mod to Futaba servos ( I don't know about these digital servos) The 2 3000 series servo I took apart, ( to reverse the action) had different colour wires on the internal pot, one was red white black, the other red yellow blue, so I can't be sure of that. However the wire that goes to the wiper of the pot, should NOT be altered, just the other two. Hope this is of some help
tom
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BarryM

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Re: Servo Stretcher
« Reply #9 on: February 08, 2007, 09:10:35 am »

Tom,

Thanks for reply; I'll give it a go. If it works Ok then it's simpler than introducing a gearbox.

Given that external stretchers are on the market commercially, I wondered if someone had produced a home-brew version or if one of the mags had published a DIY job.

Thanks again,

Barry M
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