Jack Skip

For years I have avoided using servo extensions, preferring to cut and extend the existing servo wires to the length needed. I solder in the new wire and use shrink wrap to insulate the joints. So far I have not had any problems, but have been using this technique in smaller glow and smaller gas planes.

I am now equiping a 33% gas plane and have a question for the experts. I am using digital servos (6 JR 8411s and one 8611 and one digital n the throttle).


I want to ensure the servos get ample voltage and current to use their full available torque.

Is it better to avoid the additional connector in a servo extension and extend the wires?

Should I just add in the servo extension needed?

Thoughts anyone?

Josey Wales

My Feedback: (61)

I also just splice in the necessary length of wire on my 50 and 100cc planes. Works great. 20g wire.

Campgems

My 2 cents worth. Vibration is a killer for a lot of electronic stuff. A soldered wire with little or no stress relied is a canadate for failure. A well crimped wire is less likely to break than a soldered joint. On the other hand, each plug/jack, IE servo connector, will give you a slight loss of signal. This is a very minor problem though when the length of the wires is under 4 feet and the signals are basicly slow speed in electronic terms. I would suggest that the servo extention would be a couple gages bigger wire for the extra length. I would use some contact grease on the pins and then I use some waxed button thread and make a two turn loop around the plug and jack to make sure they stay together. This is more for assembly and replacing parts than for the possibility of the plugh coming unpluged. It add a tenth of a gram at most, so weight isn't an issue. It's cheap, raid your wifes thread collection, (if she sews), or borrow a couple feet of the thread from a neighbor. Worse case, go to a fabric store and buy a spool for a couple bucks and it will last your whole club for a life time.

One other thing I like to do is lace the servo leads into a cable. Where possible.

Bottom line, I wouldn't solder, but use heavy duty extentions. They won't let you down.

Don

aussiesteve

Same here. I avoid additional servo plugs whenever possible- just something else that could cause problems.

Often, I also splice in "Y" pieces for the positive and negative wires so that they get fed directly from the battery(via switches) with a "T" Connector (Dene style plug) that way I don't need to use a power expander and the receivers only supply the signal current.

Jack Skip

Thank you for your input. 2 to 1 for extending the wires.

Thanks Campgens. Good points to think about. But I think I will extend the wires and support them along the fuse so they aren't flopping around in flight. This should also minimize risk of failure due to vibrations.

Rodney

IMHO, solder joint is much more reliable than another connector, especially if the other connector is where it seldom gets exercised (not repeatably disconnected and reconnected). The unplugging and replugging tends to remove any corrosion or oxides that will build up on the contact points. In any expensive plane, I would never use extensions on any critical function.

JohnW

My Feedback: (6)

Best, would be to open the servo case and RX case and solder in a brand new wire from servo to RX... not exactly feasible, which is why we have extensions. Just use good ones. As mentioned previously, soldered wires are more likely to fail under vibration than crimped wires. I make my own extensions using Molex locking ends and crimped gold pins (also called Ashlok) and 20ga wire, 18ga or better on batteries. Never had a extension failure, running 400oz servos on jets and 35%, thousands of flights. Nice part is, I didn't jack up the servo lead like a splice would and replacement/reallocation is a lot easier.

Campgems

John, I've always wondered why the servos didn't have a socket to plug in the lead. That would be so nice. The trouble is where would you put it. Short of opening up the case and soldering new leads, a 1 1/2" pig tail would be great. As they are now, the attached lead is the right size for a 0.25 size plane, but when you approach the 48" span with servos in the wings, the leads will fall short every time. By the time you are through adding extentions, you end up with a foot of extra wire. I like the idea of making my own extentions. I just haven't got to the point of doing that yet.

Given that I will not plug and unplug the aileron leads into the receiver each trip to the field, I use a short extention, 3" off the receiver, and plug my aileron leads to that. This means I have three plug connections to contend with. From 30 years of working on big main frame comuters, I learned a lot about cables and failure modes. The constant plug and unplug is a plan for failure. The gold plating on the contacts has a finite plug cycle, and it isn't in the 10's of thousands, but maybe in the low hundred's. Each cycle will skuff off some of the plating. Soon, the base metal is making contact vs the Gold plating. Coorosion is the next step before failure. The Tin plating is just a cheaper contact metal. Mixing the two isn't usually a good idea for signal voltages as the low voltage, low amp, high speed signal is more prone to signal loss than a battery connection. There is a technique called time delay reflectometry where you can shoot a square wave signal, same as our servos use, down a wire and you can detect every conection on the cable. We used that method to trouble shoot computer room cables where we may have six or eight boxes strung in series. We could see every plug connection. If there were six boxes and you saw seven bumps on the scope, someone had used an extention cable, which was not uncommon. You could tell if there was a high resistance short, or a bad crimp, etc. Each connection distorts the signall slightly. A bad connection distorts it more than a good one. If the square wave takes on a shape other than a solid signal, the servo will get confused as to what it is being told. A good clean signal is very important.

Last point, on servo wires, the wire count is probably more important than the wire size. A single 20ga wire will not take anywhere near the flexing as a 20ga stranded with a high wire count. The softer and more flexable, the longer it will last. It will cost more per foot though.

Who knows, maybe they will come up with Wireless servos some day. Not sure how to get the power to them, but if they could find a way, wouldn't that be nice. Bind each to the receiver and not a wire in sight. Ahh dream on Don

Don

sgillmore

My Feedback: (50)

Is a GOOD solder joint really that susceptible to failure from vibration in a giant scale plane? If that's true our planes are all doomed as they're full of solder joints. Deans plugs are commonly used to connect giant scale batteries and a good solder joint is your only option there.

Now if you don't know how to solder properly and create a cold joint I could see that. But I'm having a difficult time believing that properly soldered wires are just going to vibrate apart. However, I'll admit that you have me thinking about it (and concerned).

Oilsands

I have seen more connectors fail (due to water, corosion, overheating from either a poor connection or too much amps) than I have seen properly soldered connections (joining wires together). These are all on heavy equipment where there is alot of vibration (more than we will ever see on our planes). I have rarely seen any connectors break at where they are crimped onto the pin as well, nor have I rarely seen any connectors break at where they are soldered onto the pin. Pin contacts will wear out with continual pulling apart and putting back together, same as wires that are bent back and fourth will break. I have seen many soldering that was not very good, these will come apart sooner than of course a properly soldered joint or will cause damage due to the increase in resistance from a poor connection.

JPMacG

My Feedback: (2)

I open the servos and replace the original lead with a lead of the desired length. I have been doing this for several years successfully. You do need good soldering skils and tools to do this. Don't make this your first attept at soldering on a circuit board or you may damage your servo.

JNorton

My Feedback: (2)

My two cents.

A properly soldered joint that is covered with heat shrink tubing provides resistance to vibration failures. The wires we use for servos are light weight ie low mass. If you route your wires and secure them you have a superior joint to a connector that is rarely taken apart. Connectors that are not taken apart (so the contacts can rub against each other cleaning themselves) are subject to corrosion failures.

Make bad joints - use losely wrapped electrical tape to cover them and you are better off using extensions.
John

JohnW

My Feedback: (6)

sgillmore, others, I trust both a pinned connectors or a soldered wires in my plane if I did the work. My concern is that many don't have good soldering skills, hence my "vibration" comment designed to scare peeps that can't solder back to using extensions. Now if you know what you are doing with solder, you know I'm full of bunk as you can manage the vibration issue. So, unless you know you are a very good at soldering, find someone who is to do the work and/or teach you how to solder, or get extensions. But, if I showed you some servo wires I saw once soldered by an experienced EE, you'd shudder... scary.

altavillan

My Feedback: (1)

Soldering became extremely easy for me once I found Deans Silver solder. Tower sells it. As well as a nice selection of heat shrink. Dubro has the best choices of size and color. So does my local Hardware store. Finding appropriate wires is a bit trickier. 22 ga from Airwild, 26ga twisted from Cermark. 26ga straight from Radio Shack (strander phone wire, colors match Futaba). Twisted 22 ga Hitech colors from Troybuilt, and servo extensions from places like Sin City Jets or wherever gold plated connector extensions are sold..
I'm fairly confident soldering in the appropriate wire with a good length of heat shrink will be less likely to flex and fail than a connector. The wires end right at the connector with no support, and should fail long before a good or maybe evan not so good solder joint.

pilotpete2

I'll throw in another two cents for properly done soldering
One detail I personally like to use, is to stagger the splices at 1/2" intervals, so that the three joints and heat shrink are spaced out, makes it easier to fit a larger piece of h/s over the whole bundle, neatness counts[8D]
Pete

sgillmore

My Feedback: (50)

I second that! There are as many opinions regarding solder. All I can say is, if you haven't tried the W.S. Deans Racing Solder with ProFlux...you don't know what you're missing. The only problem is that it's just about always sold out. [sm=cry_smile.gif]

JNorton

My Feedback: (2)

Save the "Silver solder" for mechanical joints. If the flux has any acid in it, it will eat the copper wire and cause a break after time. I use Kester 44 Series 37-63 .031" solder with excellent results. I also use a temperature controlled iron.

Most problems come from
1. Material not clean
2. Not tinning the iron tip to transfer the heat
3. Applying the solder to the top of the iron instead of the joint
3. Too much heat
4. Movement.

Here is a pretty good tutor. http://www.curiousinventor.com/guides/How_To_Solder

John

rmh

real problem with HD servos ?
the crimp connectors
we are stuck with em for quite awhile
If you have perfect connectors (std types they are good for
ready ?
3 amps contineous.
I make battery paks for various setups I use and the absolute worst are tin plated crimped - for resistance
Don't believe me?
mwasure the resistances then add some extensions together .
for many models this is a non problem tho

Rodney

Do not use silver solder on electonic parts as the flux is an acid and will soon result in a corroded connection.

rmh

Radio Shack has the right stuff - resin core

sgillmore

My Feedback: (50)

I have silver solder that I use for music wire and push rods. I understand the W.S. Deans Racing Solder to be different. It's designed for soldering silver and gold plated surfaces. It contains "2 percent silver and a high activity no-clean flux." The market it for their battery bars and Deans connectors, so I assumed it would work for any electrical connection.

Here's the description from the W.S. Deans website ([link=http://www.wsdeans.com/products/solder/index.html]http://www.wsdeans.com/products/solder/index.html[/link]):

"Deans Racing Solder with Profluxâ„¢ is the best solder for silver and gold plated surfaces (battery bars and connectors). Silver alloy prevents chemical interaction for stronger joints and less resistance which means more power! ProFluxâ„¢ prepares the surface and leaves no residue. It comes packaged in 1 oz. tubes that fit nicely in your toolbox."

I've been using it exclusively for electrical connections R/C cars, planes and helicopters for 5-6 years and I've never had a problem. Maybe I should do some more research. I'm just starting to get into gas planes (50cc) and I sure don't want to take any chances.

sgillmore

My Feedback: (50)

Any thoughts on this stuff? I picked some up from my LHS the other day because everyone's out of stock on the Deans solder. It contains 3% silver and a rosin core. I've only used it a couple times, but it seems to be as easy to work with as the Deans.

Novak Lead-Free Silver Solder
[link=http://www.shopatron.com/product/part_number=5831/135.0]http://www.shopatron.com/product/part_number=5831/135.0[/link]
"This is Novak’s Lead-Free Silver Rosin-Core Solder. It contains 6 grams of solder, which is approximately 4 feet (1.2 meters), and is the same solder that Novak uses. It is environmentally-friendly and specially formulated for hand soldering. It contains 3% silver for high-conductivity, low-resistance and for strong solder joints at a relatively low melting point. Meets RoHS compliance standards."

JPMacG

My Feedback: (2)

Very good advice. Forget the silver solder, get some conventional electronic solder such as the Kester 44. There are silver solders that are suitable for electronic work, but they have no advantage over the conventional tin lead solder unless you are concerned with lead content. The Novak silver solder is probably fine for electronic work but the cost is outrageous. A one pound roll of Kester will cost 10 or 15 bucks and last a lifetime and is the perfect solder for electronic work. Radio Shack sells the right stuff for electronic work - it might even be repackaged Kester.

Jack Skip

Thank you everyone for sharing your knowledge and experience.

I have another electrical question for you.

If I am using an additional battery to the receiver, is it better to "Y" it into a channel not expected to have much draw (ie. throttle) or to a heavy draw channel (ie. rudder)?

altavillan

My Feedback: (1)

The heaviest draw. That keeps the possible heat away from the RX. And reduces some of the load the buss bar needs to supply.