grosbeak

I am trying to create a mechanical solder joint - two elevator pushrods with a threaded rod between them. It's well wrapped in thin copper wire but I'm not getting the results I'm after. Solder pools on the wire but does not wick into the joint. I'm using a 60W pencil iron with a flat tip, and it doesn't seem to matter how long I apply heat the joint... the result is the same.

I'm wondering if I need more flux - is there such a thing as too much?


Cheers.

scale only 4 me

My Feedback: (158)

A lot of good advise on the same subject here

http://www.rcuniverse.com/forum/m_10767067/tm.htm

speedracerntrixie

My Feedback: (29)

How did you prep the wire? Did you clean, sand and clean again?

DMcQuinn

My Feedback: (13)

I think you may need more heat. I use a propane torch when soldering up large diameter (e.g. 1/8) music wire. Also sand the wires clean before you start. And as far as flux, use plenty. I don't think you can use too much, because the excess will just run out anyway.

JPMacG

My Feedback: (2)

For steel wire you will need an appropriate flux. The flux core in electronic solder is not the right thing. I use a liquid zinc chloride flux called "Stay Clean". There are lots of others on the market that are suitable.

Of course, you must remove all corrosion, dirt and oil before you solder. I clean the parts with Skotch Brite then wipe everything off with alcohol.

I think it is easiest to use a soldering iron. A small torch will work but it requires more skill. Once you get everything right the solder will flow into the work very easily.

JohnBuckner

My Feedback: (1)

Sounds as if you trying to use rosin core solder on piano wire. Acid core solder works far better with piano wire, Just be sure to never use acid core on wiring or electronics.

John

grosbeak

I'm trying to solder a Du-Bro 4-40 threaded rod between two Du-Bro 4-40 push rods, like so:

jetmech05

Not enough heat...Youre gonna need a bigger iron

Kaos Rulz

Ditto. Try a Weller gun, or small butane torch.

Rotten40851

My Feedback: (2)

The torch will work best, clean wires to be joined with emery cloth and ""do not touch the wirewith your fingers after you cleanit"" the last thing to touch the wire before you solder it should be the emery cloth. Put your three pieces together the way you want them joined and wrap them well with the thin copper wire. Hold work in the vise and heat a little bit with the torch, apply the Acid core flux and it should sizzle a little bit. you are now ready to apply heat to the work NOT the solder. Use silver solder not rosin core solder, apply heat to the work until the solder melts on it when you touch it about a 1/2 inch away from the heat source. do this down the length of your joint moving the torch and solder accordingly, hope this helped you out.

grosbeak

The threaded rod is Du-Bro #379 4-40; their website notes that it's made of stainless steel. The two push rods are Du-Bro #145 4-40 but the metal is not specified. The copper wire is from 14GA speaker cable, but I stripped it a couple of weeks ago and it's probably well oxidized by now.

I've alternated between two types of solder and two types of flux with similar results.




One type of solder is Kester 60/40 Rosin core - the solder is fairly thick and the spool is probably at least 20 years old (leftmost in picture). The other spool is also Kester; the solder is much finer but the content is not specified (one from left).
The flux I used is for Lead-Free solder, which in retrospect seems like a bad idea - 60/40 solder is part lead, right (one from right)? I did try a bit of another type of flux as an experiment and it seemed a little better (rightmost).

The end result is very strong, but it looks like $#!+.





After reading a lot of replies on various forums I've identified some possible trouble spots:

1. Rods not clean enough
2. Copper wire not cleaned
3. Wrong solder type
4. Wrong flux type
5. Too little flux
6. Too much flux

LesUyeda

May be strong, but it does not look like the threaded rod is soldered, just captivated in solder.

Stainless stell will NOT solder with normal solder of any kind. It takes a special flux; as I recall I used a stuff called Alpha 90. The last time I went to get some, all I could find was in gallon containers.

Les

ARUP

Ovalized brass tube sections in lieu of wire wrap work great for these apps.

jetmech05

Looks like a cold solder joint to me....I'd heat it up until it flows better

JPMacG

My Feedback: (2)

The solders and fluxes shown in the photo are not the right thing. You need to get some flux that is proper for stainless steel. Plumber's tin-silver alloy solder is stronger than the electronic tin-lead alloy solders shown in the photo, although they will probably work OK with the right flux. Also, cleaning the threaded rod may be a problem because the inner diameter is inaccessible. Maybe a wire brush would work. And I agree with the previous posts, 4-40 rod is probably too large for a 40W iron.

I think we have now all thoroughly beat this subject to death.

Propworn

My Feedback: (3)

The best solder for that application is Stay Brite Silver Solder. It comes as a kit at most hobby shops and contains the solder, flux and instructions. If you are going to use a standard solder use a liquid acid flux like you would find at hardware stores for soldering plumbing. Like has been mentioned before find a short piece of brass or copper tubing that all 3 will just barely fit inside. Clean all the components and fit all three rods inside in the positions needed. Now squeeze with a vice or pliers and slowly flatten it with all three inside while guiding your threaded rod so it rests between the other two in the center. Liberally apply the liquid flux and apply heat and solder together. The soldering iron you are using is not going to get the joint hot enough. I see you live in Canada so if you check at Canadian Tire you will find a much heavier duty iron with a large tip for under $30 I have used mine to solder 1/4 wire together. If you insist on wrapping the joint with wire rather than copper wire for joining smaller rods you can use common picture hanging wire from any hardware store. Sand it clean then wrap tightly around the wires and with the application of the acid flux the joint should accept the solder.

Dennis

mighty9

My Feedback: (10)

Great tips guys. Although this topic isnt close to beaten to death lol .I know a site where there is 2,309 replies to using a water bottle for a fuel tank. Now thats beaten to death.

grosbeak

Since I posted this problem on multiple threads late last night there's been a great response. I couldn't possibly do what everyone suggested, so I had to look through the replies to come to my own conclusions. I'm very pleased with the results.





So what did I do differently?

- Coupled the threaded rod to a push rod and soldered to the pushrod
- Configured the three push rods in a triangular stack instead of a "flat pack"
- Sanded and tinned all three push rods before assembly
- Sanded the copper wire and wound with pliers instead of fingers
- Assembled, wound and soldered in a vise instead of in the airplane

I used the 60-40 Kester solder with a little of the Kester flux. This time it flowed into the gaps perfectly; I (a) heated a spot with the iron for a few seconds, (b) applied solder to the joint about 1/4" away, (c) moved the iron over 1/4" inch, and repeated.

Thanks for your replies - I learned a lot!

jetmech05

Now that looks like a good solder joint...way to go

TheRickster

My Feedback: (12)

Just another point of interest.. At full travel you will be inducing uneven elevator travel with the servo mounted as it is. As the servo arm moves through it's arc of motion it will put more travel into one pushrod than the other.. If you lay the servo arm on it's side then it will be on the same axis as the elevator and will retain even travel through it's arc..


Rick

grosbeak

Hi Rick,

Do you mean that the whole servo should be mounted on its side?

jerrya

My Feedback: (4)

Try some Staybrite Silver solder next time. It melts at 430 degrees and is stronger than regular solder. Kit comes with some special flux, but rods should still be cleaned. The correct way to use solder is to get the metal hot enough to melt the sloder as its applied, not to use the iron to melt the solder onto the metal.

1320Fastback

Heres one I put together.

For flaps on my Avistar. I hit the push rods with sanding drum on my dremel and used a Weller gun to heat it up.

For the very limited throw I need it works well.

Rotten40851

My Feedback: (2)

Very Nice job, I'm sure you will have no trouble in the future soldering.

RealFly

Also if you are going to solder anything with that much mass you need more heat.  I suggest that you buy a Weller (good common brand found in home supply stores) soldering gun.  I use it anytime I am soldering push rods or other non-electrical connections that are relatively large.  The size you want is one that has a trigger that gives you a 100w and a 140w setting.  It will provide more than adequate heat and does not have the issue of an open flame.  It's a great investment and will last you a lifetime.  The tips are cheap.  I also agree with the Stay-Brite - great stuff.