Servo extension wires - Is it better to solder or use the supplied connections - RC Groups
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Jul 29, 2012, 01:47 PM
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steve101's Avatar

Servo extension wires - Is it better to solder or use the supplied connections

Is it better to solder or use the supplied connections for servo extension wires. Is there any significant voltage drop across the supplied connections?

Here's my application. Futaba S3010 aileron servos with 12" heavy duty servo extension wires going into a 12" heavy duty "Y". I'm using a Spektrum AR600 receiver powered by a 6v 2600 mAh NiMH battery. The plane is ~17lb.
Last edited by steve101; Jul 29, 2012 at 02:21 PM.
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Jul 29, 2012, 01:57 PM
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steve101's Avatar
I should have added, are there reliability issues with supplied connections due to vibration, corrosion, etc.
Jul 29, 2012, 02:45 PM
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Do you do anything special when you connect the 3-wire extension to a servo wire? To the "Y"?
Jul 29, 2012, 03:03 PM
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If you are fully competent solderer then the best way to extend servo wires is to remove the original wires from the circuit board inside the servo and fit a new lead of the correct length. Otherwise use a good quality servo extension cable with a cable lock.

Jul 29, 2012, 03:42 PM
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Re:Do you do anything special when you connect the 3-wire extension to a servo wire?

Re: Do you do anything special when you connect the 3-wire extension to a servo wire?

I run string through the servo wire next to the connection and then thread the string through the servo wire on the opposite connection. I do this a couple of times with the string, make it tight and then tie it. There isn't any pressure on the wires, only the connectors. Then I shrink wrap the connection.
Jul 29, 2012, 03:44 PM
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Re:If you are fully competent solderer....

Re:If you are fully competent solderer....

I'm not a circuit board competent solderer.
Jul 29, 2012, 04:01 PM
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If you can solder half way decent, just cut the wire any where in the middle and splice in the required additional length. This if far more reliable than using an extension. It is rather common for the extension connectors (after a length of time) to degrade due to corrosion. If you repeatedly disconnect/reconnect this is not as much of a problem as having one of the connections buried where it never gets exercised as the repeated connecting tends to disslodge any corrosion that can occur over time. I would not try to connect inside the servo as suggested above unless you are a really experienced solderer. It is quite easy to just splice in an extended length though as you have an easier time making a good solder connection and will not damage a PC board by over heating a trace. In short, a soldered connection will be much more reliable than an extension will be.
Jul 29, 2012, 04:31 PM
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+1 on using a cable lock with standard connectors for connections outside of the wing's structure. I use shrink tubing for the servo extension connectors that are buried in the wing's structure.
Jul 29, 2012, 07:28 PM
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I'm not keen on "flying" solder joints in the middle of servo wires because on an IC powered model there can be a lot of vibration and solder has a very bad mechanical fatigue performance.

Jul 29, 2012, 10:32 PM
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Mikecam's Avatar
There is a reason you won't find soldered joints on any full scale airplanes, all are crimped. Use the right length extension and heat shrink.
Jul 29, 2012, 10:47 PM
I'm a pilot, 100 yrs too late
Thermalin's Avatar
I have to extend ailerons servo wire on my current build and have always soldered the extra length.. now you have me nervous. I think this time I'll go with the proper length, tie then heat shrink the connection will be inside the wing not accessible unless i pull the wire

I noticed the hitec twisted heavy gauge 24" extension is 2.00 dollars cheaper than untwisted normal gauge...???
Last edited by Thermalin; Jul 29, 2012 at 10:52 PM.
Jul 29, 2012, 11:01 PM
Registered User
Been soldering in my extensions for decades. Extensions tend to corrode with time and require cleaning, how many people take the time each year to pull and clean the servo extensions? You mentioned the Y-Harness, perhaps the most problematic item used in RC. If you have a radio big enough to avoid using them it's a good idea but not everyone has a bigger radio. You do what ya gotta do.
Doesn't take a lot of skill to clip a servo wire and solder in an extension. I buy my servo wire at Hobby People when it comes up on sale. My heat shrink at Lowe's in different sizes.
Jul 29, 2012, 11:47 PM
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Crowfly's Avatar
I've been just plugging them together for years. I havn't had a problem,and I don't think I have ever heard of a problem from anyone I fly with either. But I always try to buy name brand heavy duty. The only connection I put a lock on is the battery. In case it were to shift or fall out. Or maybe just because it makes me feel better for some reason.
The only ones I solder are little foamies,where every gram counts. Or it's hard to wad up the wire and tuck it in.
Jul 30, 2012, 12:05 AM
Suspended Account

Extending servo wires

Hi guys,

Servo connections should never fail.

Any connectors have to be accessible eiher in the fuselage or in a servo bay that has a removable cover.

Never use a connector in an unaccessible location.

If a 36 inches extension is not long enough and no longer extensions are available then the exension has to be soldered. All three soldering should be apart by one inch or so. In other words, each soldering should see the original insulation of the two other wires.

A good soldering starts with a good mechanical joint.
An example of a mechanical joint prior to soldering is two U shapes one into the other or a good twist of the wires before soldering.

Make sure the solder is melted by touching the wires with the solder and watch to see the liquid solder spread out along the joint. This posting is not a lesson in soldering.
I you are not adept at soldereing you should practice with wires that are not used in the model.

Each solder should be insulated with tape even though the adjacent wires still have their original insulation.

A shrink wrap over the whole joints is fine.

Now that joint can be located in an unaccessible location.

Jul 30, 2012, 12:06 AM
Registered User
I do both, soldered and sometimes a tied extension cable. I like my extension cables to be the same gold contacts on both connectors. If you have a mix of contact types (gold, tin, or some other), I've seen phantom woogedyness on control surfaces that were fixed by unplugging and reseating the connector again. I believe this is due to a tiny bit of corrosion leading to higher resistance connections. I have not tried a dielectric greese like I've used on higher current test equipment I've designed in my job, but I suspect it wouldnt hurt. I just need to build up a test plane. Only problem is it can take years for corrosion to cause an issue. Its a hit or miss thing that you really dont want to happen to your prized plane. I've been hit by what I suspect is a corrosion issue twice in 30 years. Fortunately the pre-flight control check on the ground caught both. I'm just speculating here, but at work, using different alloy metal contacts is a no-no.

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