threading 4-40 rods for ball links
 

To get the correct length 4-40 push rod with threads at both ends , I was thinking of splicing 2 pieces of 4-40 rods using brass tubing and soldering them . Will this joint be strong and secure enough ? These are for the elevator push rods of a Sukhoi SU 31.

RE: threading 4-40 rods for ball links
 

Why not just use a piece of wood dowel for the mid section? or a section of carbon fiber tubing and glue the rod to the inside of tube ends.

RE: threading 4-40 rods for ball links
 

If you could get both rods hot enough it would be strong enough...go to a welder and ask him to braze the rods togrther...like solder only works at a higher temp....
nothing wrong with using the method mike said in his post

RE: threading 4-40 rods for ball links
 

I started using these a few years ago and now I usually replace the kit supplied rods on all my planes.


http://www.centralhobbies.com/contro...e/pushrod.html

RE: threading 4-40 rods for ball links
 

sportflyer-RCU,

Just go to Lowes or Home Depot and buy a 4-40 Die. Then buy the 4-40 threaded rod and cut the rod to the length you need and cut your own threads on the other end. It don't get any easier than that.

RE: threading 4-40 rods for ball links
 

> Then buy the 4-40 threaded rod and cut the rod to the length you need and cut your own threads on the other end. <

You can't use a die on the threaded rods sold in hobby shops. The threads on these rods are not die-cut but rolled. The rod diameter itself is too small for a die. In order to make a threaded rod you need to by a Rod-Chuck and use it on a welding rod.

RE: threading 4-40 rods for ball links
 

Dubro and GP make solder on 4-40 threaded ends. They work good if you do your solder joint right. Been using them for years.
Edwin

RE: threading 4-40 rods for ball links
 

I agree , one cannot cut the threads with a 4-40 die on a standard threaded 4-40 rod. the wire dia is only .09 which is too small . If I cut the threads myself I normally use steel welding rod of dia .12 . I make 2 passes , first with 5-40 die followed by 4-40 die. This makes the cutting process much easier. However this is a much longer process than soldering/brazing the pre-threaded 4-40 rods together using a brass coupling tube . I was just wondering about the strength of the joint . Actually I can use low temp silver solder since this is used for soldering on the solder type clevis .

RE: threading 4-40 rods for ball links
 

You also never mentioned the size or type of plane?? The rods Don mentioned from central are outstanding. The solder on threaded ends work very well if you solder them correctly, sounds like you know how.

RE: threading 4-40 rods for ball links
 

I'ts a Great Planes Sukhoi SU31 with about 78 inch wingspan. To be powered with DL 5o gasser :)

RE: threading 4-40 rods for ball links
 

I could have sworn I use a 4-40 die to cut threads before. I just went out into the garage and didn't even find a 4-40 die. I did see a 4-40 tap. Sorry guys. It's hell when you get old and the gears start to slip :).

RE: threading 4-40 rods for ball links
 

There used to be some old style rods that can be cut. But they're hard to find now. Dont know of anybody that sells them anymore. The current 4-40 is too hard to thread and like was already stated, too small to thread.
Edwin

RE: threading 4-40 rods for ball links
 

Sportflyer-RCU, the solder will be strong enough. I use solder links on 35% and turbines with servos pushing 400oz/in of torque. I've never had one fail. Use proper soldering technique and all will be good. I've also used the carbon rods with the titanium ends as listed by Don M. they too work fine.

RE: threading 4-40 rods for ball links
 

Yesterday I experimented with brazing silver solder and it works like a charm. Easy to use with the right flux ( black paste ) and when the temp is correct (used a propane torch) the solder flows easily. The joint is very very strong. I would not use high temp silver solder for the solder clevis for fear of making the clevis brittle due to the high temp . I have used solder clevises for smaller planes and the work well. I was concerned over the gas engine vibration and the larger plane .

RE: threading 4-40 rods for ball links
 

Pick up some Carbon Fiber Pushrods at www.darrolcady.com

He sells a CF rod that the hole is the same size as 4/40 rod. You simply glue a section of rod (with threads on the end) into the CF rod with Epoxy/JB weld and let it dry. These work great, are light, inexpensive, and strong.

RE: threading 4-40 rods for ball links
 

How long do you need these rods to be? If they are too long and unsupported it will bend and you won't get the elevator movement that you need at higher speeds. I use old carbon fiber arrow shafts.

RE: threading 4-40 rods for ball links
 

I'm assuming the elevators are in the tail, correct? I wouldnt do long control rods for the elevator.
Edwin

RE: threading 4-40 rods for ball links
 

Elevator servos are also in the rear just ahead of the horiz stab , so the rods are relatively short , just slightly longer than the root of the horiz stab. Length is not a prtoblem .