JB Welding Pushrod & Ball Links Choice Questions

[Kafin Noe’man]

So my Brodak P40 ARF comes with two-part pushrod that needs to be soldered together upon finishing. Question is, will JB Weld work instead of soldering it?

The other option I was thinking is to make my own one-piece pushrod from a carbon fiber tube that has ball links at its ends. Is it safe if I use the ball links that screw onto a 4-40 thread and have a 2-56 screw through the ball and into the nylon control horn? Thus I don’t have to enlarge the holes on the control horn.

I’m afraid I will damage the control horn holes if I’m trying to enlarging it to fit the 4-40 screw.

[Dan McEntee]

So my Brodak P40 ARF comes with two-part pushrod that needs to be soldered together upon finishing. Question is, will JB Weld work instead of soldering it?

The other option I was thinking is to make my own one-piece pushrod from a carbon fiber tube that has ball links at its ends. Is it safe if I use the ball links that screw onto a 4-40 thread and have a 2-56 screw through the ball and into the nylon control horn? Thus I don’t have to enlarge the holes on the control horn.

I’m afraid I will damage the control horn holes if I’m trying to enlarging it to fit the 4-40 screw.

   I think you are misunderstanding what size the hole is for the swivel/pivot. The 4-40 threaded rod is what threads into the ball link and the other end is epoxied into the push rod or is attached some other way if not using a CF tube. The pivot is 2-56 and should close to the size of the hole in your control horns.

  Type at you later,
  Dan McEntee

[Mike Griffin]

will JB Weld work instead of soldering it?

Kafin, I can only speak for myself here.  I have never been a big fan of soldering as I have had them fail a few times.  I have never had JB Weld fail anywhere I have applied it.  The strength of the stuff is amazing.  Now I am talking about the regular JB Weld, not JB QUICK.  I cannot speak to that because I have not used it in areas I consider critical for strength. It may be fine but I do not know.

Mike

[Colin McRae]

Kafin, if you want to use the wire pushrod system w/ coupler, you can use JB weld instead of soldering. I have done this on a couple of models where it involved a repair.

But it is recommended to roughen the wire ends a bit so the JB epoxy has something positive to grab inside the coupling. I used my Dremel tool cutting wheel to lightly roughen the wire surface. My opinion is that simple sanding of the wire is not good enough to roughen the wire as music wire is a very hard material.

Not the prettiest joint, but it will not come apart!

But also, the CF tube / ball link system is a great way to go. That is what I will be doing on any of my future model builds.

There is also a good video in the building section that discusses how to make up CF pushrods w/ ball links. Actually quite easy to do.

[Dave Harmon]

The push rod couplers sold by Du-Bro/Brodak are actually a roll pin.
These are intended to pin 2 metal parts together like a shaft going through a collar that needs to turn with the shaft.
The pin gets pressed into a hole pinning both pieces together....it is secure....like an early K&B 40 prop drive....ugghh...hated that engine.
BUT.....that coupler/pin material is not solderable no matter how hot you get it.
The best thing to do is get rid of the whole thing and do it the right way with a one piece pushrod with ball links on both ends.
I realize the picture of my P-40 pushrod in another thread is soldered....and I have always been concerned about it.
As I said in that other thread....I should have opened the planking and done it right.
However....JB Weld will work but rough up the the parts then clean the parts with lacquer thinner to get all the oil off....gotta be really clean.
You CAN'T solder that shitty wire and those roll pins and get a good joint!
If that stuff was solderable it would have been ok....not the best but ok.

[Ken Culbertson]

will JB Weld work instead of soldering it?

It may be fine but I do not know.

It is definitely NOT.  Quick is about 1/2 the strength of regular and doesn't get nearly as hard.  Still very good for bulk and making metal fillets etc. but absolutely not to hold a pushrod together.

Ken

[Dan McEntee]

The push rod couplers sold by Du-Bro/Brodak are actually a roll pin.
These are intended to pin 2 metal parts together like a shaft going through a collar that needs to turn with the shaft.
The pin gets pressed into a hole pinning both pieces together....it is secure....like an early K&B 40 prop drive....ugghh...hated that engine.
BUT.....that coupler/pin material is not solderable no matter how hot you get it.
The best thing to do is get rid of the whole thing and do it the right way with a one piece pushrod with ball links on both ends.
I realize the picture of my P-40 pushrod in another thread is soldered....and I have always been concerned about it.
As I said in that other thread....I should have opened the planking and done it right.
However....JB Weld will work but rough up the the parts then clean the parts with lacquer thinner to get all the oil off....gotta be really clean.
You CAN'T solder that shitty wire and those roll pins and get a good joint!
If that stuff was solderable it would have been ok....not the best but ok.

    The cleaning process that you went through to apply JB-Weld will also allow you to do a successful solder job. You need to clean any metal to metal solder joint this way. Clean the wire until it's nice and shiny with some scratches. Clean the INSIDE and OUTSIDE of the coupler the same way. Apply some flux, a good hot broad tip soldering iron and watch for the solder to flow. On that joint it should flow by capillary action and should not be lumpy or have any excess build up. Clean off any left over flux.
    I would also not recommend using JB-Weld for that type of joint either. When you apply the epoxy and then slide it all together, some will get pushed out. Not much glue for the area involved and will be susceptible to vibration causing the joint to crack. Fuel will eventually get to it also,
     Type at you later,
    Dan McEntee

[jerry v]

Kafin,
Yes, here on SH is my P-40 ARF building tread. Kit was my birthday gift from my son. a) I must build it. b) I have to build it with the glow power ( I may convert it to electric, because I fly mostly electric). c) I have to build it as quickly as possible to go fly in competition.
I built it in four days - mostly because I waited 24 hours between steps for epoxy to cure. My experience from flying my P-40 : maybe it’s my flying style over controlling ( in my combat models I have the positive stops on the belcrank to prevent stalling of the model) but I made my handle spacing less than 4 inches. It’s still  too sensitive  for me. If I will decide to convert my P-40 into electric I will redo control system too. I will install custom control horns at least 1 3/8 in on the flap and elevator and add the ball links and carbon tube push rod between the flaps and elevator.
Now going back to kit. I bent the wire from bellcrank to flaps with the pliers. Mark the position, hold the short end with the pliers, hold the long end with the hand or another pair of pliers  and bend toward the inner wing tip - geometry of this model requires both push rods to be on the same side between the fuselage and the flap control horn. Cut the extra end to the length at least 1/2 in long because there was history of spiral keeper falling off the short bent end of the pushrod. I like the kit spiral keepers because they can be installed on the already bent wire - just like the screws. I practiced to bend wire on some similar scrap wire. The kit wire between belcrank and flap is pretty easy to bend, but it’s only one time try)). Kafin, if bending will go wrong - then there is second option to solder the 4-40 treaded end with the steel split pin keeper as was described on this tread. Don’t use J-B weld. You can use the 2-56 ballinks as on the original tread question. In my P-40 I bent 2 mm music wire as one piece between the flap and elevator horns. It was the fastest way to finish the control. The custom pushrod can be made in different lengths to easy replace even at the field. The model was tail heavy. Maybe carbon pushrod will be lighter. Historically Brodak P-40 has not enough glue at the belcrank mount. Make sure you reinforce the area by inserting extra wood and glue into mounting area trough the wing push rod opening and also pin the plywood belcrank mount trough the fuselage bottom with the bamboo 3 mm stick. But not to interfere with the belcrank movement. Having the stock muffler and big wheels helps to make better vertical CG. Some pilots build the P-40 wing with 1 inch dihedral.
The last picture is my Brodak Ringmaster two piece push rod soldered with the coupler.

Jerry

[jerry v]

One more thing I learn. The top US stunt flyer uses the bent pushrod wire with soldered retention wire on his take apart model. No balllink. Two piece fuselage, quick disconnect pushrod from flap to elevator. Back to the future))

Jerry.

[Motorman]

I would never glue the push rod together on any plane I care about. If you sand the wire and inside of coupler back to bare metal you should have no problem soldering it with regular 60/40 rosin core solder. If you don't like the coupler provided, you can bridge the gap with a piece of wire wrapped with copper serving wire, very easy to solder and still adjustable.

MM

 

[Kafin Noe’man]

The kit wire between belcrank and flap is pretty easy to bend, but it’s only one time try)).

Jerry, thank you so much for your thorough response.

That one time try only that scares me out. Is there any more pro tips to ensure the 90 degree bend is spot on the neutral position. I mean, I know how to mark the midway point, but when you start bending the wire you’ll have to deal with the ‘bending radius’ that might affect the final alignment of your pushrod 90 degree bend.

I’m looking forward to hearing your take on this.


Best,
Kafin

[jerry v]

Kafin,
Bending wire at the mark is always challenging)) If you will make a piece of scrap wire and measure certain distance from the end of wire to the imaginary “centre control horn hole “ let’s say 100 mm. Marker has some thickness, and mark on the wire will be 1 mm wide. If you put edge of pliers on the shorter edge of the mark (99.5 mm) and  bend 90 degrees you will make certain size from the end of wire to the inner side of the 90 degrees bend leg. Add the radius of the wire and you will know the actual distance . The target is 100 mm. Now on the second scrap piece shift the edge of pliers to make the correct size. If you wrap the wire with masking tape and put the mark 30 mm from the bend center- you will have a reference point simulating the model. On the P-40 all you will have will be a mark on the rod for horn hole center with neutral flaps. You can put reference mark  30 mm distance or so from the actual bend center, wrap the pushrod with the masking tape and put reference mark on the tape. After bending the wire you will know the deviation from the target dimension. 100 mm earlier test now  is 30 mm. Masking tape protects the mark from accidental erasing with sweaty fingers during the process))  Belcrank  and , hopefully, equal length of already made ARF leadouts ends are what we have. In my opinion - leadouts differences can be adjusted at the handle. Bellcrank position is questionable- can’t see it trough the exit opening)). Conclusion- bending pushrod is not that critical. Most important is flap and elevator equal neutral position.

Jerry

[Steve Helmick]

I would go with a CF tube pushrod, because I remember several OPP's I crashed due to control failure...lapped wire pushrods joined with solder and very little binding wire. Not everybody is good at soldering, as it turns out.  Steve

[Ken Culbertson]

Don't sweat it too much.  Make the bend.  Try and make sure that is 90 degrees from the one in the bellcrank.  You get a lot of ware and eventually slop if they are off.  If you screw it up, just chop it off and make a joiner.  Oh, and remember the bend goes where it makes the bellcrank parallel to the pushrod, not the centerline.

Ken

[Kafin Noe’man]

So after doing some more research, I think I’m gonna go with the option of putting threaded coupler into the pushrod that goes to the bellcrank. I plan to screw in either clevis or ball-link.

Since using JB Weld is not recommended to join the two-part pushrods together, what about using it for this purpose? I’ve used 90-min epoxy to glue threaded coupler to the pushrod on my XEBEC and it seems so far so good.


Best,
Kafin

[Motorman]

Use a small file or a cut off wheel and put several small notches in the wire near the end of the push rod to give the glue something to key into. Also twist up a tiny roll of sandpaper and rough up the inside of the coupler.

[jerry v]

I guess, the fear of melting the nylon belcrank is still exist))
But if look into CF tubing and 4-40 treaded ends in most model applications- RC helicopters, RC 3D and CL stunters - all inserts are glued with JB weld or epoxy. Simple heat if with the heat gun will make them to come apart. If clean the pushrod wire with the sandpaper, make it in the shape of the zigzag , make mating 4-40 treaded rod in the same zig-zag shape, and overlap their 1 inch zigzag, wrapped with tread, or copper wire, smeared with epoxy or JB weld- ‘this contraption will work. If slide the CF tube or aluminum tube or brass tube over the joint, then nobody will know what is inside)) Zigzag highest points should not exceed the tube inner diameter. JB weld is basically epoxy mixed with the cast iron dust /chips. This blob of glue will have a good weight)) CF tubing has good tensile strength, but it will splinter. Most applications require wrapping the end of CF tube with the tread and more epoxy. Or slide brass tube over the CF tube with epoxy. Simple aluminum tube filled with JB weld over the zigzag area will be the lightest combination.

Jerry

[doug coursey]

ON THE RC HELICOPTERS WE JB WELD THE ALUMINUM ENDS IN THE CARBON TORQUE TUBE THAT DRIVES THE TAIL ROTOR.WE NEVER HAVE A PROBLEM WITH IT AND THERES A LOT MORE STRAIN ON THAT THAN ANY PUSHROD ON A CONTROL LINE PLANE...

[Ken Culbertson]

I guess, the fear of melting the nylon belcrank is still exist))
Simple heat if with the heat gun will make them to come apart.

You have me concerned.  I am using JB Weld for a CF battery compartment.  Per the JB Weld specs Regular is rated to tolerate 500 degrees steady, 550 max.  Batteries get hot but not that hot.  Am I missing something here?  A Monokote gun goes to about 400  max.

Ken

[jerry v]

You have me concerned.  I am using JB Weld for a CF battery compartment.  Per the JB Weld specs Regular is rated to tolerate 500 degrees steady, 550 max.  Batteries get hot but not that hot.  Am I missing something here?  A Monokote gun goes to about 400  max.

Ken

VOILA !

Jerry

[jerry v]

Back to the topic. In my P-40 the pushrod between belcrank and flaps is .070 inches diameter. I bent it into L shape as per instructions, and model flies well. Profile model with exposed controls is easy to modify for ballinks, CF pushrod and different control horns. The model has nylon belcrank and Z- bend connection to the flaps. It’s ARF, pushrod is not removable. I prefer to solder 4-40 treaded end with the roll pin coupler to the end of the existing pushrod ( belcrank to flaps) It will be much stronger, reliable and lighter connection than the JB weld. Nylon belcrank may give some concern but heat during soldering can be dissipated with the vise grips. In my previous post I showed the pictures of disconnecting with heat gun the 4-40 insert JB welded to the CF tube pushrod. During the crash CF tube survived, JB weld area survived. The weakest link was 4-40 treaded area. Because the whole tail was ripped off, something have to break. Heat gun is useful on repairs of the pushrods. Sometime CF tube breaks but 4-40 ends survive, sometimes CF tube survives. This is more applicable in RC helicopters. The bigger insert diameter, the bigger CF tube diameter- the more mating surface to be held with JB wed makes connection stronger. On the previous post pictures the CF tube inner diameter is 1/8 inches and insert outside diameter is 3 mm . Insert length is 3/4 inches. If pushrod wire .070 inches diameter JB welded with 4-40 treaded rod, with coupler or wrapped with wire - the mating surface area is smooth and small. This glued connection may fail. If wire and treaded rod bent like zigzag and wrapped with wire it will be like wrapping together two serrated knives blades.

Jerry

[Ken Culbertson]

VOILA ! - Jerry

VOILA indeed.  So much for manufacturers claims.  Why then would we use JB Weld instead of slow cure Epoxy for any application where shape is not important?  Personally, I would wrap and solder a pushrod joint.

Ken

[jerry v]

In my opinion the 4-40 insert and CF tube should be secured with the pin going through the assembly and the glue. Then even CA glue can be used. Good example is Dave Brown pushrod system with the L shaped end of the pushrod wire connected with the CF tube trough the hole on the side of tube and “wedged”  in with the plastic end over the wire. It requires CF tube 5/16 or 8 mm diameter which may interfere in the tight tail installations. Wherever I can I use the 4-40 screws with grounded  head, wrapped with tread and epoxy/ JB weld inside of the small CF tubes 3/16 inches or 5 mm OD. In this case the weakest link is the ball link, not the soft treaded rod.

Jerry