Heavy duty servo extensions
 

Hello all,
In general when would you begin using heavy duty servo extensions? Would it be at a specific oz torque rating? I'm asking this because at the moment I'm building a Revolver 70 and the manual states additional parts to buy would be 6" HD servo extensions for the wings, but when I bought the servos the LHS said standard are sufficient. I'm using a Hitic HS 645 MG servos rated at 133 oz at 6 volts. What's your opinion/ advice?
Thanks,
Pat

personally, I size extensions on the size of the servo wire. no smaller gauge than what's on the servo, but the extensions don't need to be huge either.
(if the servo has big 'ol thick wire, I use big 'ol thick extensions.) based completely on common sense, I don't have any empirical data :D
(I'd much rather spend an extra $3 on wire than risk a $400.00 airplane)

Hi PDF
I have had some difficulty in that area (servos twitching). As a result I now always use heavy duty extensions.

Depends on the load but more so on the length of the run for me. In general, all my servo extensions are heavy duty. I have a spool of heavy duty wire to make my own extensions from time to time. Just an FYI - the cheaper extensions (standard or heavy duty) sometimes come with tin plated contacts in the connector. If you have two dissimilar metals with current passing through them, corrosion can develop over a few years time frame. I've had twitchy servos because of that. The quick fix is to unplug them and plug them back in. The right fix is to use all gold contacts. Just my opinion.
Edwin

+1 very good point, Edwin and Villa!

I tend to solder custom length whenever possible also, they never wiggle loose that way, standard wire for analog servos,,, heavy duty wire for high torque and digital servos

Thank you for all your replies,
It seems that I can't find the answer of what size wires are used on either the servo or extensions. I'm thinking of to start making my own and be done with it.
Again Thank you,
Pat

Don't use those cheap extensions. Be sure to use the gold plated ones from JR or Futaba.

"Heavy Duty" is in the eye of the manufacturer! I consider 22 gauge to be standard duty; most manufacturers consider 22 gauge to be heavy duty. I consider 20 gauge to start the heavy duty size but that is just my opinion. I use 6 volt or higher batteries and don't think the standard wire many servo manufacturers supply will allow full usage of supplied voltage. I agree that probably the length of the extension is a better determinant of how "heavy" the wire should be than any thing else. I make up my own extensions, soldered to the servo on one end and new, crimped plugs on the other end.

I do the same thing and buy servo wire at my LHS in bulk. Both 20 and 22 gauge.

Yes same here, I never buy extensions I cut the servos lead new or not , in two and cut a custom length with new heavier gauge servo wire to splice into it. Fifty foot rolls are not that expensive.

The major advantage beside losses from excessive lengths of servo wires is reducing an excessive unneeded number of plugs. The plugs from say ailerons that are removed all the time for transport tend to be self cleaning and less resistance but hidden or buried plugs that are never removed can become corroded and cause potential problems.

John

TailDragger RC sells very nice heavy duty extensions

Barracuda hockey, thanks for the info for taildragger rc, those are great deals on the servo extensions.
Thanks,
Pat

First off, no way you *need an HD wire for a 6" extension, especially on a 70" plane. Don't get me wrong, I like heavy duty stuff, but it is totally not needed. I have used plenty of HD servo extensions. If the price is right, length is right, and I'm not trying to save every gram of weight, sure I would use them. But the question is about need. Most of us don't need HD servo extensions.

Wire acts as a resistor. The longer the wire, the more resistance it has. Heavier gage wires have less resistance for the same amount of length. There are fairly simple calculations to determine how much loss in signal power you will lose for a given length of wire. You need to know how much current the servos are drawing. I don't know the answer to that, but I know that the BEC's or regulators I use deliver up to 5A continuous and I don't seem to max them out, so 5A seems like a safe number to use.

I just found this website, they have a chart for wire length vs signal loss for different sized wires:
http://www.securityideas.com/howtocalvold.html

I am building a 78" high performance airplane. I chose regular servo extensions for everything except the elevators - the elevators are getting a 42" extension. I am running one 42" extension plus an additional standard gage signal wire, so the HD power wire is carrying power for two servos. I have 6" plus 3" extensions for the ailerons, none are HD. Servos are probably rated around 150oz-in.

Do you have a source for gold connectors? Also, what gauge is heavy duty?

Try rctimer. Their extensions are reasonable and HD.

Thanks 4*60, and what gauge is HD?

The quality of the connectors is more important than the gage of the wire. If the connector has poor contact between the parts, a large voltage drop can occur in the connector itself, much greater than the drop due to wire resistance. That is why gold plating and high spring tension is very desireable. Also a large mating surface is preferable.

Sure seems painful to add photos, but I think I succeeded. I flew this beast for many years with Futaba 148 servos, and STANDARD extensions with no problems. 84" wingspan, Enya 120 R power.

Les

Granted, but they weren't 300oz servos at 6.6v and you weren't flying 3D :)

600+ oz. rated servos @ 7.4V. flying full on 3D with 150" span and larger airplanes. Using standard extensions in stuff this large is like going bear hunting with a switch...

Bob

It is in my opinion that whatever arms come with the servo, are strong enough to carry the load of that servo. Is a mfg really going to make a 2-3-400 oz-in servo and supply it with arms only strong enough for a 30 oz-in servo? But I will say if I have to go with longer arms then I will go ahead and get the heavy duty or even aluminum.

Servo Extensions (to extend the wire from the servo to the receiver)
not servo output arms (mechanically connecting servo to pushrod)

;)

For the record, here are some H9 aluminum servo arms that I managed to bend on third flight of my 52%er with using 600 + oz. servos, I don't believe the plastic arms supplied with those servos were up to the task either. I replaced the arms with SWB arms and the problem went away.

Bobhttp://www.rcuniverse.com/forum/atta...mentid=1914255http://www.rcuniverse.com/forum/atta...mentid=1914256http://www.rcuniverse.com/forum/atta...mentid=1914257http://www.rcuniverse.com/forum/atta...mentid=1914258

No sensei, we are talking about wire, not hardware.

Les

p.s. With respect to your hardware, if it was me, I would find another supplier. Those things should be T6 condition, and not soft enough to bend. They appear to by 0 condition.