Soldering brass tube to piano wire - expert opinion sought

[Nigel R]

Question for any seasoned metalworkers out there.

 

I'm somewhat familiar with binding and soldering piano wire for UC and cabanes and suchlike, or soldering mild steel washers to piano wire, but, I've not soldered brass tube to piano wire.

 

Intended use is for a DIY torque rod which needs to be, a) longer than the usual prefab 12g offerings and, b) double ended (!). I have some KS tube & wire which fits together perfectly.

 

Is there anything special I need to know about prepping? My toolkit is a basic torch, leaded solder and flux.

[Allan Bennett]

If you can do wire and steel washers, then brass will be a doddle!  Brass takes solder easier than steel so your normal technique will do the job; i.e. clean, pre-tin, and then solder together.

[leccyflyer]

As Allan said, if you can solder piano wire successfully, you will be able to solder piano wire to brass quite well, as it's a bit easier to work with. Personally I give the piano wire a clean with emery paper, a fine file or a steel brush in a Dremel to ensure the cleanliness of the surface.

[Nigel R]

Thanks chaps. My usual with piano wire is some fresh fine grit paper, then leave the flux in place for a good few minutes, then tin. Seems like this will be just more of the same 🙂

[John Wagg]

If you want some real grip then really roughen the surfaces. 

You mention torque rods so perhaps grind notches in the wire or similar. 

[Martin Harris - Moderator]

Best to use an aggressive flux such as Baker’s Fluid as cleaning the inside of small diameter tubing effectively is rather difficult. Just ensure the workpiece is washed thoroughly afterwards otherwise it will corrode. 

[Nigel R]

Thanks Martin, yes that was the worry point, getting inside the tube to clean, it'll have to be flux.

 

Edited November 10, 2023 by Nigel R

[PatMc]

I'd use silver solder & possibly the ball of a bal link instead of brass tube. 

[Geoff S]

I regularly solder brass tube to piano wire to mount wheels.  I over hang the wire slightly so I can drill a hole for a split pin and washer for scale(ish) wheel retention.  It was the method suggested by Dudley Pattinson for the SE5a kit I built as my 3rd model back in 1996.  Never lost a wheel yet and all I cleaned/tinned was the wire because of the difficulty getting inside the tube.  Brass solders very easily.  I use Fluxite to make it easier.

[Don Fry]

Roll some abrasive paper over a bit of very thin wire, so you can insert it in the tube, and through the tube,  then you can clean it by pulling back and forth

[Nigel R]

58 minutes ago, PatMc said:

I'd use silver solder & possibly the ball of a bal link instead of brass tube. 

 

Not sure I follow - how I could use the ball of a ball link?

 

 

[PatMc]

Nigel, hopefully a picture is as good as 1000 words. Here's 2k worth. 

 

 

 

 

 

They are leftovers extras from years ago, I think the balls are actually "soft" soldered to the torque rods.

[Martin Harris - Moderator]

Nice idea but I think the OP wants to butt join two rods using brass tube?

[gangster]

When I required some double ended rods to link aelerons I discovered that there are two sizes of 2mm pushrods With threaded ends. Some are thinner than 2mm with the thread squeezed. Don’t know the correct term. But some are tapped on 2mm rod. Those you can tap.  How you identify which to order I have no idea. We used to actually have shops where you could actually see them.

Edited November 11, 2023 by gangster

[Paul De Tourtoulon]

8 hours ago, PatMc said:

Nigel, hopefully a picture is as good as 1000 words. Here's 2k worth. 

 

 

 

 

 

They are leftovers extras from years ago, I think the balls are actually "soft" soldered to the torque rods.

I bend the ends at 90° and then solder the balls.

[Nigel R]

8 hours ago, Martin Harris - Moderator said:

Nice idea but I think the OP wants to butt join two rods using brass tube?

No, the brass tubes are to flatten and drill, one at either end of the torque rod.

 

It's to link two inboard servos with outboard twin rudders. Surfaces are too thin for burying a servo. My other idea was to bury a bell crank but I preferred the torque rod idea so I'm trying that first...

[leccyflyer]

The flattened brass tube torque rod terminations work fine with small models - have used that system myself. The other thing that you might try would be to bend the torque rod from threaded rod and use the nylon screw on torque rod horns, like these.

 

[Nigel R]

I would need to thread both ends. Would work with mild steel but I'm skeptical about being able to thread piano wire. Maybe I should try that. 

 

Either way the commercially available rods are too short, sadly

[leccyflyer]

You could perhaps  take a pair of those commercial torque rods and connect them together with a brass tube sleeve?

[Paul De Tourtoulon]

Don't thread piano wire, it has ruined 3 of my dies,,

[Nigel R]

Would the brass joiner be solid enough to butt join two torque rods? I admit I'd prefer to use the screw fitting that these come with, as it gives some scope to fine tune / adjustment. 

[Mike T]

Cut out the middle man.  If you're going to flatten and drill the brass, why not just flatten and drill the wire?  Grip the wire above the bend with a heavy mole (or 'vise') grip to a) hold the work and b) act as a heatsink to avoid de-tempering the bends.  Then heat the ends to near white hot and belt them with a heavy hammer and a suitable anvil.  If you make the bent end overlong, you can fold the flattened end over on itself and solder it before drilling, to give a more substantial pad for the pivot hole.*

 

Alternatively, just heat the ends as described above and then run a die down them to use commercial plastic horns.

 

In both cases, after working, heat to dull red and quench to harden, then polish and heat to blue/purple to temper.

 

Yes, you lose the spring in the ends that you've worked, but you don't need it there.  The mole(vise) grip keeps the temper in the bend and in the length of the rod, which is where you do need it.

 

(* If you stick to plan A and use brass, cut it over length and fold/solder it before drilling, etc.)

 

[john stones 1 - Moderator]

Put solder adaptors on, then plastic horn thingys, then you've thread for adjusting.

https://www.slecuk.com/control-fittings/m2-metal-solder-extender-8-per-pkt

[Nigel R]

Oh good gosh why have I not thought of those doohickeys before.

[Geoff S]

19 hours ago, gangster said:

When I required some double ended rods to link aelerons I discovered that there are two sizes of 2mm pushrods With threaded ends. Some are thinner than 2mm with the thread squeezed. Don’t know the correct term. But some are tapped on 2mm rod. Those you can tap.  How you identify which to order I have no idea. We used to actually have shops where you could actually see them.

 

The thinner 2mm threaded pushrods have rolled threads like bicycle spokes so the rod itself isn't 2mm.  They're the ones that SLEC sell in packs of 10 IIRC.  To make a double ended rod you can solder a threaded end onto the pushrod - SLEC sell them too. 

 

A word of warning about pushrods with thread at both ends.  If there are no locknuts the pushrod can turn with vibration and gradually unscrew at one end.  The adjustment remains the same so there's no warning anything's amiss until it finally falls out and you're left with no connection.