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No electric to HS-81 aileron servos. Is the wiring too thin and/or too long?

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No electric to HS-81 aileron servos. Is the wiring too thin and/or too long?

Old 08-30-2016, 03:53 PM
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rustyrivet
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Default No electric to HS-81 aileron servos. Is the wiring too thin and/or too long?

This is not the first plane that I've built with an individual servo out on each wing half to each aileron. But this is the first time I'm using Hitec micro HS-81 servos and experiencing electric loss. When I shorten the length of wires to each servo, then they seem to work fine. So then from that test, I can only assume that the micro HS-81 servo wire is just too thin to carry enough current to the servo motor. With the wire harness and extensions and the servo lead tunneling through wing, it adds up to about 40" of wire on each wing side. Would I do well to cut and remove most of the flimsy thin servo wire on each of the two servos and replace it with a heavier gage wire? ......and also remove about 10-12" of excess wire off of the Y harness?
Old 08-30-2016, 04:42 PM
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speedracerntrixie
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I run 50" wires with a pair of HS 81 servos in a sailplane without issue. Then again I don't use extensions. I solder in the correct length of 24 ga servo wire.
Old 08-30-2016, 07:34 PM
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52larry52
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If this is on a glo powered plane (not an electric) and you are using a 4.8 volt RX battery, try it with a 6.0 volt RX battery.
Old 08-31-2016, 05:28 AM
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Dittos to what Larry has said about using five cell batterys also note what SRT said about eliminating extra plugs from using a custom soldered harness. Even soldering your own Y cord will eliminate at least one plug set.

What worries me Rusty is a total of near 80 inchs of cable run indicates a rather large airplane if it is not some sort of glider and may indicate that what may be a better choice in aileron servos would be a jump to the HS-225 mighty mini. I have experimented with the HS 80/81/85 a lot on ailerons and the choices are limited.

So rusty giving a through description of the airplane and its intended use would net you better answers instead of keeping the responders guessing.

John

Last edited by JohnBuckner; 08-31-2016 at 05:34 AM.
Old 08-31-2016, 06:31 AM
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rustyrivet
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It's a scratch built 50" Kadet electric trainer with a lipo and ESC that generates 5.1V at the servo. I didn't think a Seniorita reduced from 63" to 50" needed much power at each aileron. Each wing half at 25" is not very long, but by the time you snake extension wires through the tunnel, and leave yourself some room to connect and disconnect the wing with a 12" extension wire at the receiver, it all adds up to a long and thin wire. From the input I'm gathering here, I think I need to solder up some direct leads to reduce all the joints.

On that topic, can anybody tell me what gage wire I should be looking for?
Old 08-31-2016, 09:09 AM
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I use plenty of HS-81 servos and never had a problem with extensions up to 24"; I've never needed more.

The extensions I use are Futaba or Hobbico, 20AWG.

Maybe try twisted pair?
Did you isolate the problem with individual servos and remove the Y-harness from the equation?
Did you test the system outside of the airframe to determine any interference?
Did you try a different wiring harness AND Y-harness combination?

Good luck

-PD
Old 08-31-2016, 10:16 AM
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JohnBuckner
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OK now we are getting the full picture. Rusty you said in the first post that you have up to a total of 80 inchs of cable run and that in the last post that it is a reduced size Seniorita down to a 50 inch span. Remember most people don,t place their servo at the wing tips so it likely you have the servos at a total distance between the two at forty inchs. How can a servo span of forty inchs require eighty inchs of cable?

OK I understand that since you are talking about tunnels that the wing is likely a foam core wing but look the tunnels need to run directly from the servo to the center of the fuse compartment and not some squared off cable consuming indirect route and the same for inside the cabin compartment.

I actually have a Seniorita with standard span that flies as a twin with two OS FX .25's or with the removal of the nacelles by two bolts each becomes an aerotowed glider and it uses two HS 85's with soldered extension wire of the stock cable and the total length of extension from each servo is about 28 inch with an additional 6 incher from the receiver and one plug set per servo.

Last edited by JohnBuckner; 08-31-2016 at 10:28 AM.
Old 08-31-2016, 04:32 PM
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rustyrivet
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OK.....I spent about an 3/4 of an hour jacking around experimenting to find two different problems ocurring at the same time;
A) One of the two new HS-81 servos was defective right out of the box and kept turning when it would work at all. B) The Y harness was bad too.

Changed out the two and now both ailerons are working fine with about 50" of wire to each servo!! Thanks gents fo the help. This is the first time I ever got a defective servo NIB with any brand. I don't recall defective servos NIB with Futaba and JR, and I'm wondering if this is normal for Hitec. Not impressed.
Old 08-31-2016, 05:23 PM
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52larry52
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Bad servo?...........Not normal, but "stuff" happens. Carry on, glad you fixed it.
Old 08-31-2016, 07:37 PM
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Originally Posted by 52larry52
Bad servo?...........Not normal, but "stuff" happens. Carry on, glad you fixed it.
As you suggested, I'm also going to experiment and see about changing the ESC up from the current 4.7 volts it's delivering, to 5.5 volts. It has 3 programming optiions of 4.8V, 5.5 and 6V. I feel like these small motors with long wire leads could do better with a little more juice. Thanks again.

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