pushrod soldering questions

Rosin core solder is fine as long as the steel parts are mechanically cleaned (sanded with fine sandpaper). A heavy soldering iron is fine if it can heat the wire quickly enough. A torch is my second choice since it is much easier to overheat the metal and lose its temper.

The clevis should be a snug fit on the wire. The closer the fit, the better the connection.

If you clean the connection real well after, there is a product called Sta Brite that works very wel. It is an acid flux and if it gets trapped in the oint it can lead to corrosion.

Yes. A small soldering iron will probably not work, but a "gun" type will do nicely. I use a 75 watt gun for this work.

Use standard resin core electronic/electric solder.

Sand the pushrod with 100 grit sandpaper to roughen it. You can cut a couple of grooves in it with a file, but I haven't found that to be necessary.

If you make a nice, shiny solder joint, it will be fine. I've used this method on competition fun fly models, and giant scale aerobatic models, too. It's easy, strong, and neat. If you want to test, pull on the assembly with two pair of pliers.

Sand the pushrod. Wipe everything clean and tin the rod. Assemble the joint and heat by holding the gun at the end of the clevis/rod joint. Apply a little more solder at the end of the clevis. When this flows into the joint, pull the iron away and let it cool. Do not move it until it is completely cooled.

I've used this method for many, many years on all types of models, with absolutely no problems at all.

Dr.1 Driver "There's a Hun in the sun!"

Ken --

I prefer a heavy iron and acid core solder -- I wouldn't trust my airplane to a solder joint made with a gun and resin. Start out by sanding and cleaning everything to be soldered with solvent then use your torch to sweat the solder joint; heat the wire so that the solder will melt on contact with it and not by trying to melt the solder with the flame. When done, clean the joint with a slurry of baking soda and water; wash clean and oil lightly to prevent rust.

I do exactly as above, accept I usually apply a little solder flux to the joint before soldering. As mentioned, when the clevis/rod is properly heated, the solder will wick into the joint, much like sweating a copper pipe. Add enough solder until you just start to see the solder begin to ball up on the other end

- then immediately remove the heat. Once cooled, clean the joint thoroughly with alcohol. You should have a bright, shiny "professional looking" solder joint. Try practicing on a few clevises.

BTW, I use a standard Weller dual heat gun.

Alan Harriman

Ken, I'm no expert, but the main thing in soldering clevises, landing gear parts, etc. is to make sure your parts are clean! Soldering guns will work nicely. I like the Sta-Brite silver solder sold by Great Planes. It's solid, and you apply the flux to the parts just before you solder. You will have to wash off your soldered parts to keep the left over flux from corroding the metal.

Morris

On 5/10/2004 6:53 AM Ted shuffled out of his cave and grunted these great (and sometimes not so great) words of knowledge:

What "tinning" means, is to heat the piece and put a THIN coat of solder on that piece. Let it cool, then assemble and solder. Tinning assures that there is SOME solder all the way in the joint.

Assemble the joint

I'd love to have one again. My 15 year old one died about a month ago. They've disappeared from stores around here. Where do you find them? Dr.1 Driver "There's a Hun in the sun!"

Ken, there's a lot of good tips in this thread...

It all boils down to cleanliness, using a flux, and having enought heat to cause the solder to wick into the joint..

One thing that I think deserves mentioning is the type of soldering iron you use... The "pistol-grip" guns such as the old Weller dual-heat guns are fine if you're using them on the bench, away from the model's electronics.

But if you're soldering close to receivers and servos, use a "pencil" type iron... The "pistol grip" irons generate a pretty strong magnetic field when used and have been known to demagnetize the magnets in servo motors, and I've been told they can also zap an IC chip...

I have a little 20/40W dual heat "pencil" iron (Radio Shack #64-2184).. It was only about $22 and really does a nice job on 2-56 clevises, and has microtips that are perfect for servo wires....

Anything larger gets the torch.....

Cheers,

Bill

STA-BRITE Silver Solder is the only way to go! It is much stronger than regular tin based solder. The liquid acid flux works great. Very little head is needed to get a good solder joint! You don't need to use very much of it. It's the BEST. Regular tin based solder joints I have done have been known to break loose under vibration, etc. The silver solder (STA-BRITE) will never do that!

I agree. 20-40W pencil type is preferable for me too. The guns sometimes generate too much heat....just cooking the solder out of the joint before you get a good bond.

Do a search on Ebay for: 'Weller Soldering.'

There be all kinds of irons and guns....

Ken, You don't need a lot of heat. I use a 40 watt pencil by Weller. The trick is use "Sta-Brite silver solder.' It is very strong, requires little heat and comes with it's own flux. Clean the parts before you solder and it is very important to get all the flux off afterwards, or the parts will rust. But make sure that you use the flux. The flux is the key.

The only thing not mentioned in other responses is that some push-rod stock seems to have a coating of some sort - it looks a bit like zinc (galvanized) to me (but I doubt that's what it really is).

If you're working with that sort of rod, sand the thing until you see base metal.

Trying to get solder to flow onto that 'mystery coating' is an exercise in getting pissed.

Otherwise, a spritz of denatured alcohol is about all the cleaning you normally need. Sanding doesn't hurt, but it's not routinely necessary.

I've been making up mechanical solder joints for model airplanes for over two decades with rosin core solder because that's what I had on hand.

I've been making up silver soldered refrigeration joints for a lot longer than I'm going to fess up to, and I rarely ever need flux at work. Ditto for hobby soldering. In many cases flux just gets in the way and has been known to mask a flawed solder joint.

The only reason I've got lead solder in the building shop now is that I finally ran out of rosin solder, and I won't use the lead-free crap unless I'm working on a potable water system.

Sho 'nuff lead solder can still be had, but not at The BORG - you have to sniff out a welding supply house if you want the good stuff, which IMHO is _way_ better than rosin solder for mechanical joints.

I wouldn't waste the time trying to silver solder 2-56 rods - takes too much heat. 4-40 is about the smallest thing I ever use silver on.

Forget silver solder until you're ready to tangle with home-brewed landing gear.

BTW - if the clevis is a sloppy fit on the rod, crimp it first, then solder. Cheers, Fred McClellan The House Of Balsa Dust home.mindspring.com/~the-plumber

PMFJI, folks.

If you're going to use Sta-Brite (I use it all the time and recommend it highly) and its flux, do yourself a big favor when the joint has cooled: make up a thin mixture of baking soda and water, put the _cool_ soldered joint in the mixture, and let it sit until the bubbling stops. The baking soda will neutralize the acidic nature of the flux. If a mainly liquid mixture isn't practical or if you can't put the joint into it, make the mixture more like a thin paste and brush some on the joint. Let it sit until you can't see any bubbling, wipe off, then do again. The idea is to let the acid react with the base of the baking soda until bubbling stops...and having a "liquid" mixture helps you to see the bubbles.

If the acid flux isn't neutralized, corrosion can and probably will occur, leading to eventual problems.

John P.

I can put together a joint with a 40W iron and resin core solder that you will tear the clevis apart and not get the base loose from the wire no matter how hard you try ! ! ! ! !

David

That's because you did not do the joint correctly. If it vibrated apart, it was a 'cold joint'.

David

Soldering guns usually cannot transfer enough heat rapidly to make good joints.

David

I'll sell ya mine - I haven't used it in about 15 years.

I think the best 'all-round' soldering iron is the Weller WTCPN controlled heat station. You can put a small tip in it and do PCB work, then put in a big tip and solder pushrods or small battery cells. It heats in about 60 seconds.

If I cannot do the joint with the WTCPN, I have an 80W Weller on an SCR controller to adjust the heat that will handle any other modeling job.

David

If you sand down to bare steel, ya ain't gonna get solder to stick, no matter what. Steel must be welded or brazed. That's why that black finished crap pushrod material is a pain in the butt.

David