M2 threads on piano wire

[Richard Walton]

Guys,

I'm hoping someone can give me some advice. I'm in the process of completing Peter Miller's Ballerina - I know it's about time - and need some advice about linking up the ailerons to servo's in the wing. I've gone away from the central single servo and installed mini's in each wing. I have already made the links by using a Z bend at the servo end and a clevis at the aileron end. There's what I believe to be a bit too much "slop" in the link caused by the Z bend. I want to install a clevis at the servo also but need to have thread at both ends. Here's the rub - at last you say - Before I go buying an M2x0.4 die and stock, how easy is it to put the M2 thread on the other end of the piano wire links. I don't want to use those solder on extenders as I think they'll add unnecessary weight.

Thanks in advance.

 

Edited By Richard Walton on 06/06/2017 09:30:45

[Don Fry]

If you have piano wire, it is just too hard to put a thread on. Why not use softer wire. Or buy some threaded rod. But another way is to just make the hole the Z bend goes through smaller. The should be a squeeze to get the corners in.

[Denis Watkins]

Threading is ideal Richard

If the steel appears too hard to thread, difficult to get your die to bite

Then heat the selected wire ends to a good cherry red and let it air cool

Don't quench this as it will harden more

Then thread your bar

[Cuban8]

I've never had much success putting small threads on piano wire when just using hand tools (M2 push rods that come pre threaded at one end only).  Not saying it can't be done, but I'd try to think of another method to make your links.

How about a 90 degree bend in the wire secured with a swing keeper - use this method myself, never gives trouble. I've seen a Sullivan snake inner stiffened with with a short length of piano wire inserted inside, and then the small lengths of studding screwed in for clevises at each end. Many more ways to 'skin a cat' of course.

 

 

Edited By Cuban8 on 06/06/2017 10:00:23

[Barryorbik]

Hi Richard, I fly mainly (older) helicopters and the servo to swash, head links and tail servo to tail horn are all threaded rods and in many cases becoming hard to find so, on the smaller helicopters and only when parts are no longer available, I have made replacements from either un-threaded 2.0 mm piano or silver steel rod using the annealing method described by Denis but with a small filed chamfer on the end of the rod to aid starting the die. A close look at the threads on the original parts indicate they are often rolled threads and not cut with a die, so I am always wary of over stressing my replacements but have not had any failures with the die cut versions to date.

Barry

[Andy Green]

If the slop is in the Z bend, you can run some CA into the joint, once dry it will easily free up and you have what is a a CA bearing with no slop.

I solder a clevis to one end and only have 1 screw end for adjustment. No need to have to screw ends.

Andy

[TIM Shaw]

I agree with Andy - used that technique on F3f gliders with no problems.

I've also tried threading the other end of threaded rods too, and found it difficult and rarely 100% succesful.

As regards soldering an extension on, I'd rather do that these days than try to cut a thread with a die.

But I try to never have threads on both ends of a control rod anyway. Unlikely as it seems, I once witnessed a nice, 60 powered model go in with elevator failure, and the post mortem revealed the threaded rod had screwed itself right into one clevis, and right out of the other one.

[Cuban8]

Nothing wrong with soldering providing the joint is well made and you can 100% guarantee correct flow throughout the fitting. I've come across threaded solder adapters that on close inspection, were rusty inside (ARTF accessories )  - impossible to clean effectively and a failure in the making. Although I've spent most of my career in electronics/engineering and can solder to high standards, I'd never trust soft soldering one of those adapters to a push rod but preferring a 'mechanical' joint i.e thread or clip fixing. Just my preference, of course.

Tim's warning above about having threads on both ends and the possibility of the system unscrewing itself is valid and goes to show that nothing's infallible. However, suitable locking nuts and preflight checks should really prevent such occurrences. Even on a single threaded clevis its good practice to lock it with a nut after adjustment, as it stops the threads wearing because of vibration.

Edited By Cuban8 on 06/06/2017 10:51:41

[Ken Lighten]

Solder a clevis onto the plain end, you should only need adjustment at one end, just make sure the wire is properly cleaned before hang, I normally file a slight taper onto the rod and just push the clevis onto it, proper tight joint that way

Ken

[Bob Cotsford]

I just run a 2mm drill into the solder adaptors to clean and scuff the bore before soldering them. Use a separate flux, don't rely on flux-cored solder. I've never had a solder adaptor come off. Whatever you do, remember to use locknuts with metal clevises both to avoid the rod self-adjusting but also to lock up the thread and stop it fretting with vibration. As Tim said, if using a clevis either end the rod can spin clear out so I run a drop of CA into the thread at one end once the model is trimmed out.

For something the size of a Ballerina pushrod I'd either use two adaptors epoxied onto 2mm carbon rod or for something less flashy, just a length of 2mm threaded rod ('studding' or 'all-thread' )  with a clevis either end.

 

Edited By Bob Cotsford on 06/06/2017 11:04:07

[Nigel R]

My answer to short runs like ailerons is screw clevis & a Z bend.

Mind you, with a pair of Z bend pliers on hand, its funny how many control run problems get solved with a Z bend at somewhere in the link.

Soldering is also fine, and usually my answer for one end of a bowden cable throttle link.

[Former Member]

[This posting has been removed]

[Richard Walton]

Thanks for all the very good advice guys. It's given me some food for thought. Right now it looks like I'll go for the soldered on clevis.

[kc]

The threaded rod will probably be too small in diameter to allow the thread to be cut with a die- reason is the existing thread will have been rolled which increases the dia a little. A thread which is on too small dia will possibly pull out!

Try using the SLEC Swingkeepers which need only a simple 90 degree bend. They clip on.

Otherwise invest in  Z bend pliers from Hobbyking etc which make a better z .

Edited By kc on 06/06/2017 12:22:04

[Nigel R]

I'd forgotten about swing keepers, they work well too.

"Otherwise invest in Z bend pliers from Hobbyking etc which make a better z"

Its worth saying, I find the inside of the Z bends needs a light cleanup with some sandpaper after you make the bend.

[Keith Berriman]

Richard. If you are good at soldering. I take a threaded rod section file a flat on the piano wire. Use some thin wire rap it round both sections and solder as required

[Peter Miller]

Why not just buy 2 mm threaded rods

When using 9 gram metal geared servos I make 20 SWG Z bends and bind and solder them to the ends of teh threaed rods. These Z bends then fit the 9 gram servos while you can use standard metal quick links (Clevises)

Z bend pliers will make good Z bends every time.

AS for threading piano wire, justs forget it. Even with heat treating it just isn't worth the effort and hassle

Edited By Peter Miller on 06/06/2017 15:03:52

[Geoff S]

Not a good idea to thread both ends of push rod. Both ends can gradually become loose and unscrew without having any effect on the trim until one of them falls off the end and that has a huge and catastrophic effect. Much better to have either a Z bend, a simple bend with a swing keeper, or a soldered clevis. Personally I've found the first 2 methods perfectly OK.

If you need to have a threaded end to a length of 2mm (14 swg) piano wire then you can solder a threaded end onto it. I've never succeeded in cutting a 2mm thread manually but then, I'm no fitter. Ready threaded 2mm push rods (at least those from SLEC) aren't actually 2mm (they're slightly less) and the thread is swaged like a bike spoke at one end.

Geoff

[onetenor]

14 gauge is actually too small for an M2 thread. Refer to a thread cutting table giving the correct sizes for tapping and die cutting threads.Either buy the correct diameter mild steel rod or use studding.That is if you insist on double threaded ends. I not sure what the thread size is on cycle threads but I know they are rolled. A specialist cycle repairer might be able to roll the other end. Wheel building specialists for cars do it I know.

[onetenor]

14 gauge is actually too small for an M2 thread. Refer to a thread cutting table giving the correct sizes for tapping and die cutting threads.Either buy the correct diameter mild steel rod or use studding.That is if you insist on double threaded ends. I not sure what the thread size is on cycle threads but I know they are rolled. A specialist cycle repairer might be able to roll the other end. Wheel building specialists for cars do it I know.

[Peter Christy]

Interesting thread, as it highlights a problem I ran into recently.....

My favoured material for short pushrods (aileron links, throttle links, etc) is bicycle spokes - readily available and easy to form and tap. However, I was recently building an old classic sport model and needed some wire pushrods a couple of feet long. Luckily, I had one old pushrod salvaged from an ARTF. Almost exactly the right length, nice fit inside the tube, and already threaded at one end. That was used for elevator. But what to use for rudder? The exit points on the fuselage precluded the use of soldered joints - not enough room between horn and tube exit. Piano wire is too hard to tap easily, and perhaps too heavy anyway.

Nowhere could I find a suitable length of mild steel! Does anyone know a source? I did find an old helicopter tail-rotor pushrod that might have done, but it was pretty bent, and didn't straighten well. In the end, I simply butchered the fuselage to move the exit point so that I could use a soldered link.

So my question is: Where does on find suitable threadable mild steel in meter or 2/3 meter lengths?

--

Pete

[Bob Cotsford]

Just found this site

[onetenor]

Getting It straight could be a problem though

[onetenor]

Getting It straight could be a problem though

[Geoff S]

Posted by onetenor on 06/06/2017 17:50:00:

14 gauge is actually too small for an M2 thread. Refer to a thread cutting table giving the correct sizes for tapping and die cutting threads.Either buy the correct diameter mild steel rod or use studding.That is if you insist on double threaded ends. I not sure what the thread size is on cycle threads but I know they are rolled. A specialist cycle repairer might be able to roll the other end. Wheel building specialists for cars do it I know.

I have a couple of thread swaging tools for 14 gauge spokes but the threads they make aren't 2mm. I don't know what they are except they fit 14 gauge spoke nipples as you'd expect. I used to build all my own wheels but after the first couple I always used high quality stainless spokes which are too hard for my pre-war tools.

Anyone choosing to use 14g spokes, make sure you get rustless (cadmium plated mild steel). They aren't really rustless but that's what they're called.

Geoff