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Old Feb 04, 2014, 05:54 PM
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Question
Servo Resistance Shutoff?

I have somehow grown to almost adulthood with no knowledge of electronics whatever. I am attempting to design a very specialized set of retractable landing gear. It will require the use of a continuous rotation servo, perhaps the Parallax (Futaba 148).

I cannot seem to find any continuous servo that has, already incorporated, a current surge detector, or something that detects when a servo motion has encountered a mechanical stop and will stop the servo at that position before it destroys itself. Want to run out of a standard 4.8v aircraft receiver.

Is anyone familiar with such a servo, or, failing that, a modification to a servo that would accomplish this end?
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Old Feb 04, 2014, 06:05 PM
No bounce, No play.
davidmc36's Avatar
Canada, ON, Ottawa
Joined Oct 2010
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Maybe you could cannibalize these. They have micro switches to stop the jackscrew mechanism at the end of normal travel and safety shut-off if they jam on something and the current goes high they shut off after like a second or so.

http://www.e-fliterc.com/Products/De...ProdID=EFLG330
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Old Feb 04, 2014, 06:09 PM
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Quote:
Originally Posted by davidmc36 View Post
Maybe you could cannibalize these. They have micro switches to stop the jackscrew mechanism at the end of normal travel and safety shut-off if they jam on something and the current goes high they shut off after like a second or so.

http://www.e-fliterc.com/Products/De...ProdID=EFLG330
I will examine that closely, but of course they are very expensive for cannibalization!

Will be looking for about 2 1/2 inches of travel on a worm drive, so there will be a lot of rotations between endstops.
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Old Feb 04, 2014, 06:34 PM
No bounce, No play.
davidmc36's Avatar
Canada, ON, Ottawa
Joined Oct 2010
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IC. That would be a lot more travel than the Eflight retracts would have.

These would be pretty much ready to go but not cheap either. Not sure what your size range is.

http://store.firgelli.com/category_s/1821.htm
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Old Feb 04, 2014, 06:55 PM
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Quote:
Originally Posted by davidmc36 View Post
IC. That would be a lot more travel than the Eflight retracts would have.

These would be pretty much ready to go but not cheap either. Not sure what your size range is.

http://store.firgelli.com/category_s/1821.htm
Holy Smoke David, though those are expensive, they do seem to be a "right out of the box" solution! They come in various throw lengths and speeds, and would eliminate the need to fabricate a worm drive.

The prototype gear will be one of four supporting a 10-11 lb. aircraft. That is the best thought I have seen so far, despite the cost. Only two of the four gear will require this long throw.
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Old Feb 04, 2014, 07:05 PM
No bounce, No play.
davidmc36's Avatar
Canada, ON, Ottawa
Joined Oct 2010
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They sure do look like the thing to use for custom gear. I plan to use them when I get to the ATR-42 scratch build. I want to make a scale-like gear for it. With all the length and gear ratio choices you should be able to fit any size model. It will be a seven foot wing-span model.

Also with the PWM actuated variety you could program the speed with servo speed function of your radio, not like the E-Flight that just go at their own speed once activated.
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Old Feb 04, 2014, 07:42 PM
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I am pretty excited about the possibilities of these David. I found this impressive video on them:

JRP RC - Firgelli Linear Actuators L12-R First Look and Tests (5 min 56 sec)
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Old Feb 04, 2014, 07:45 PM
No bounce, No play.
davidmc36's Avatar
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They are sweet devices.
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