Pushrod hardware question...

[wwwarbird]

 I use the smaller diameter carbon fiber pushrods on almost all of my builds anymore. I've had it for some time but I think the batch of tubing I currently have came from Central Hobbies, the tubing is 3/16" O.D. I also use the Central Hobbies threaded inserts and I've been very happy with this overall setup. Here's the question, on a friends model I once saw a threaded adjuster unit with a jam nut that could be installed midway in a built up pushrod such as this. Does anyone have information on where to find such a piece of hardware? Any photos?

[Randy Cuberly]

I'm pretty sure that Bill Byles sold them at one time.  I'm not sure if he still does or not.  I have one in the Whitely Shoestring that I'm currently flying.  They do work well but are a bit of a PITA to adjust because the adjustment always changes a little bit as the lock nuts are tightened.  It doesn't have anything to do with the design or execution of the device it's simply an unintended consequence of adjusting the linkage in the middle.  I've seen very expensive linkage adjustments in Missiles that require the same fiddeling and cussing to get them right!

Anyway, Bill is on this forum and you can contact him to see if he still has some of these devices!

Randy Cuberly

[wwwarbird]

 Thanks Randy, I just sent Bill a PM.

[John Christensen]

Wayne you should have the unit by now. I got it in the mail last Friday.

[billbyles]

the adjustment always changes a little bit as the lock nuts are tightened. 
Randy Cuberly

Hi Randy,

I just saw this thread so I'm a little late in my reply.  "...the adjustment always changes a little bit as the lock nuts are tightened."  The way I make my adjustments is to loosen both jam nuts, then turn the center hex to lengthen or shorten the pushrod, then tighten both jam nuts while holding the center hex with a 1/4" open-end wrench.  This avoids having the adjustment that you just made change while tightening the jam nuts.

[Randy Cuberly]

Hi Randy,

I just saw this thread so I'm a little late in my reply.  "...the adjustment always changes a little bit as the lock nuts are tightened."  The way I make my adjustments is to loosen both jam nuts, then turn the center hex to lengthen or shorten the pushrod, then tighten both jam nuts while holding the center hex with a 1/4" open-end wrench.  This avoids having the adjustment that you just made change while tightening the jam nuts.

Yeah, thanks Bill.  I learned after a while to do it that way.  I wasn't trying to be critical of the parts, I have them in acouple of airplanes and they work very well.  I usually get Whitely to hold the wrench while I tighten the nuts...
Using them was his idea originally!!!

Are you still supplying them!

Randy Cuberly

[wwwarbird]

Wayne you should have the unit by now. I got it in the mail last Friday.

 Yep, I got it today John, thank you.

 

 It's one of Bill's aforementioned adjusters that I received today from John. It's a real nice piece but it's designed for the large arrow shaft type pushrods. I was really hoping for the same type of item, but one that would be compatible with the smaller diameter pushrod material. Does anyone know of such an offering?

[billbyles]

Yeah, thanks Bill.  I learned after a while to do it that way.  I wasn't trying to be critical of the parts, I have them in acouple of airplanes and they work very well.  I usually get Whitely to hold the wrench while I tighten the nuts...
Using them was his idea originally!!!

Are you still supplying them!

Randy Cuberly

Hi Randy,

I didn't take your comment as being critical but thought I'd pass on what I have learned just in case you were still having a struggle.  I am still supplying them, just not advertising them these days.

Hope to see you in January for the SW Regionals.  My new Impact is flying pretty well now with about 30 flights on it.  The trim seems to be pretty good and it flies just like the old Impact.

Bill Byles

[Mike Griffin]

Wayne I am not sure if this Is what you are looking for but I use a 3/16 hex standoff that has 4-40 threads on my take apart pushrods .  You can take the push rod, cut it, insert the titanium threaded ends in the CF pushrods ends and join them wth the threaded connector.  This gives you some adjustment back and forth in your pushrods length.  PI buy them from McMaster Carr.  Also you can cut the head off of a 1-1/2 4-40 bolt and JB Weld it inside the CF tube and save some money.  Those inserts are expensive.

Mike

[wwwarbird]

 Great idea Mike, definitely something to consider, thanks!

[Mike Anderson]

Why not just buy 4-40 allthread - ~$1.50 / foot?

[wwwarbird]

Why not just buy 4-40 allthread - ~$1.50 / foot?

 Thanks for the suggestion Mike, but in this case I don't think that will help either.

 Without having it in front of you, this one is tough to explain. I'll try to give a condensed version here. My current stumbling block is to do with the assembly of a current model. In the end here, I don't actually need an adjustable pushrod. What I do need is a two piece elevator pushrod to be able to assemble this model, at least it would make it a lot easier. For assembly access reasons I need to have the elevator pushrod connected to the flap horn before I can glue the wing in. I also need to have the pushrod attached to the elevator horn before the stab can be installed. There is no access to either horn once the wing and stab are in the fuse, and I'm not going to create any. I do have fuselage access to the pushrod midway between the wing and stab however. My thought is that if I had an "adjuster" in the pushrod I could make the connection after the wing and stab are installed.

 Actually, I just had an idea... 

[Randy Cuberly]

Thanks for the suggestion Mike, but in this case I don't think that will help either.

 Without having it in front of you, this one is tough to explain. I'll try to give a condensed version here. My current stumbling block is to do with the assembly of a current model. In the end here, I don't actually need an adjustable pushrod. What I do need is a two piece elevator pushrod to be able to assemble this model, at least it would make it a lot easier. For assembly access reasons I need to have the elevator pushrod connected to the flap horn before I can glue the wing in. I also need to have the pushrod attached to the elevator horn before the stab can be installed. There is no access to either horn once the wing and stab are in the fuse, and I'm not going to create any. I do have fuselage access to the pushrod midway between the wing and stab however. My thought is that if I had an "adjuster" in the pushrod I could make the connection after the wing and stab are installed.

 Actually, I just had an idea...  

Wayne,
This sounds like the perfect application for Bill's adjuster.  It's actually a turnbuckle adjuster with left hand threads on one end and right hand threads on the other.  Loosen the two jam nuts and turn the turnbuckle one way to lengthen and the other to shorten.  It can be assembled anywhere in the length of the pushrod.  Mine are just about midway in the carbon pushrod.
In your situation the entire thing could be assembled put in place in the flap horn then in the elevator horn and the necessary adjustment made through your access in the fuselage (wherever the turnbuckle is located).

Look carefully at the photo and you will see the hatch to access the turnbuckle for pushrod adjustment on the Shoestring.

Randy Cuberly

[wwwarbird]

 Randy,

 You're exactly right, except Bill's adjuster is designed for the large arrow shaft type pushrods which isn't what I'm using. Originally I was hoping for the same type of item, but one that would be compatible with the smaller diameter pushrod material.

 Anyway, I finally had an idea tonight and have already started working on it...

 Mike Anderson's suggestion earlier made me realize, since I don't actually need the adjustment function, I can just do this on my own. First I cut and drilled a 2" long piece of aluminum tubing that will slide over the outside of the 3/16" carbon pushrod. I drilled it with just enough extra clearance to allow for some JB Weld later on. I can get the wing and stab glued in, with the pushrod sections pre-installed, and then slide the aluminum tube over one of the pushrod halves and out of the way. Then, I'll join the split in the middle of pushrod with a 2" piece of threaded 4-40 rod JB Welded inside. Once that joint is fully cured I'll then slide and center the aluminum tube over the joint and secure it with JB Weld also. I think it's gonna work.

 Thanks for the help guys!

[James_Mynes]

I wouldn't wait for the 4-40 rod connection to cure before gluing the sleeve in place. Do it all at once. Any slight misalignment will prevent the sleeve from crossing over the joint. Do it while it's still pliable.

[John Rist]

In the RC car world they use a lot of turnbuckles.  Not sure how you would get a nut for the LH threaded end to screw into.  In the rc car world they use self taping ball ends.  Probably not much to this but it was just a thought.

http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXATGN&P=7#tech

[Steve Helmick]

I'm just wondering how Wayne has access to the middle of the pushrod, but none at the elevator horn. I'm thinking about a removeable panel inside the pipe tunnel, but Wayne's not a pipe user.  Steve

[wwwarbird]

I'm just wondering how Wayne has access to the middle of the pushrod, but none at the elevator horn. I'm thinking about a removeable panel inside the pipe tunnel, but Wayne's not a pipe user.   Steve

 Like this Steve, the rear half of the fuse is an ARF Nobler with the covering removed. I'll cover it with Polyspan once the pushrod installation is complete.

[wwwarbird]

I wouldn't wait for the 4-40 rod connection to cure before gluing the sleeve in place. Do it all at once. Any slight misalignment will prevent the sleeve from crossing over the joint. Do it while it's still pliable.

 Thanks for the concern Jim but it won't be a problem.

[wwwarbird]

, but Wayne's not a pipe user.  Steve

 Heh-heh, correct. 


 This latest plan is going to work out perfectly, got the wing glued in tonight! 

[wwwarbird]

 Well, the JB Welded joint connection is curing as I type this.

 For the elevator pushrod joint, I first put a piece of threaded 4-40 in the front half of the pushrod and let it cure. Then, that half was connected to the flap horn and the wing was permanently installed in the fuse. I had also put in a normal titanium threaded insert in what would end up being the rear half of the pushrod, for the clevis at the horn. Once all of that cured I test fit and cut the rear pushrod half to the necessary length. (Check and re-check many times before cutting) I had also made an aluminum outer support sleeve that would finalize the joint. Once all of this was figured out the stab was then permanently installed along with the elevator horn. From here on out everything else had to be done by reaching through the openings in the rear sides of the fuselage. For the final pushrod installation the next step was to slide the support sleeve over the front pushrod half, ahead and out of the way of the joint. Then it was to fish the rear pushrod half into the fuselage and thread it into the elevator clevis with some red Loctite, and in the same operation JB Welding and clamping the center joint together. I had to "feel" for the elevator clevis to get the pushrod started into it because that area is completely enclosed. Once everything is fully cured I'll slide the tube support back and center it over the joint and secure that with more JB Weld.

 Man, that was easy.  

[Mark Scarborough]

Hmmm interesting rudder shape,, I be watching now ,,

[James_Mynes]

I like your pushrod alignment tool, aka custom made clothes pin clamp. Simple and effective!

[Randy Powell]

Anyone have a current source for the small diameter carbon tube? The 3/16" OD stuff Wayne mentioned is what I've been using.

[Randy Cuberly]

Anyone have a current source for the small diameter carbon tube? The 3/16" OD stuff Wayne mentioned is what I've been using.

http://www.centralhobbies.com/control_linkage/pushrod3.htm

3/16 OD 5 32/ID  24" long.

[wwwarbird]

Hmmm interesting rudder shape,, I be watching now ,,

 No rudder shown here Mark, you must have peeked at the post over in the Building section?

[Randy Powell]

Thanks, Randy

[Randy Cuberly]

Thanks, Randy

You're welcome Randy...It's what I typically use also!

Randy C.