zippo

Nothing spectacular - just a simple way of making pushrods out of carbon tube!

I have to say that I like pushrods made out of carbon tube - they provide the stiffness you need, are light and very easy to do. I started out experimenting .. here are some of the steps I took to get to the final solution ...

(1) Tried using a tap to cut a thread inside the tube. It don't work the tube always splits lengthways!

(2) Epoxying a threaded length of studding down inside the tube. This works .. but you need to use slow setting epoxy and getting the stud that is smaller than the inside diameter of the carbon tube to centre is difficult. It also take time because the epoxy has to set (I used slow setting .. hi strength stuff). I'm lazy and there had to be a better way.

(3) The final solution !!!

Get some snake inner - the ribbed variety seems best. Cut your carbon tube to length, cut a 1" piece of inner. If required, sand the inner so that it is a tight fit in the carbon tube. Then put a couple of drops of medium cyano down the tube and push the inner into the tube so that it is flush with the outer face. Do this in one quick motion and it will slide on easily without sticking half way in.

Then screw in the a suitable threaded coupler or piece of studding (Great Planes Threaded couplers are great for this job). Attach your prefferred quick-link/ball line etc. And there you go. Its simple and cheap - the pushrods are strong and very light. Don't forget to use a nut on the threaded rod to lock the quick-link in place. Also fuel tube on the link for added security, it takes seconds and can prevent a crash.

This system doesn't look as good as the purpose made carbon tube adaptors you can buy - but it does the job just as well and is significantly cheaper.

Thud_Driver

My Feedback: (1)

I don't exactly know what a "snake inner" is but I presume you're glueing a plastic Sullivan inner nyrod inside the CF rod. That's plastic to carbon. When I CA any of the nyrod stuff, the joints don't last as the CA seems to stick initially but breaks loose under load.

What I do is get a CF rod that has an inner diameter that fits close to the the size of either the threaded rod or a metal coupler. Then I use Flash Black which is the black CA with whatever the filler is (rubber??). The good part about the black CA is that you can position everything just right without it flashing off. When set right, hit it with the the accelerator but remember the black CA still takes awhile to fully harden inside. Then I put a heat shrink sleeve around the end, others use a brass or aluminum tube, since under high stress the CF tube can still split.

If you use 4-40 hardware or, in particular, 4-40 couplers, then you can use the larger CF tubes like I think you have without having to put sleeves in them. Just make sure you put a bunch of nicks in the coupler housing with a cutoff wheel so the CA has something to grab.

I'm sure everybody has their own way. CST is running a sale on CF tubes so you could get rods in various diameters to fit your needs. Aerospace Composites probably has them too. My $.02 worth.

visioneer_one

My Feedback: (506)

Darrol Cady has done quite a bit of research into CF pushrods and has published his findings on his website. Detailed 'HOWTO' info, pictures, stress tests, its all there.

http://www.darrolcady.com/Carbon_Fiber/carbon_fiber.htm

zippo

Thanks for the info ....

While I had done some pull tests on the pushrods I'd made and found no problem - I guess you could be right on the aging of cyano plastic/carbon joints. I will re-do the pull tests on some of my older pushrods again (some are now over 12mths old).

I think that screwing the threaded coupler into the nyrod, expands the the nyrod inside the carbon tube and helps the fit/glue joint. I could be wrong and only time will tell. Just means that I need to properly check all linkages during pre-flight checks. But so far I have seen no problems at all.

I think that using the black flexi-cyano is a good idea - especially with "anything" to metal joints. I will get some and give it a go.

Anyway .. thanks you your time reading and replying to this post. I find this forum most informative and so many people are willing to exchange views and update idea's from personal experience. When it comes to linkages ... I have always believed that they are flight critical and need to be (1) the best possible and (2) continually checked over.

If there are any possibility of failure, this needs to be addressed. If the consensus is that the nyrod system is likely to fail .. then I would be the first one to say that anyone reading this should take the cautious approach and NOT USE this method

Best regards.

Thud_Driver

My Feedback: (1)

The link visioneer_one provided is pretty much a description of what I do except they don't mention sleeving the rod at the ends. The Flash Black is great stuff.

You commented that you think the plastic is expanding when you screw in the metal fitting. That's usually correct and what bothers me is that the load imposed by that on the rod is exactly what splits them. You saw that when you tried to tap the carbon inner.

The guys selling rods and fittings to the TOC and giant scale 3D guys are also selling brass or aluminum sleeves to fit over the rod ends. Don't know if we average guys need it or not, but I tend to hedge my bet on a sleeve and the minute it takes to install.

If your rods are holding up, then great!

Volfy

My Feedback: (23)

I've always just CA'ed carbon fibre strips onto balsa sticks. They are lighter than CF tubes, just about as stiff, and cost next to nothing. Metal pushrods easily attach to the balsa stick the tradition way, too.

Most of the commercially available CF tubes (i.e. fishing rods, etc.) are WAYYYY overkill for pushrod duty IMHO.

AdrianM

I used 5/32" carbon tube for my push rods. The ID id the same as the unthreaded part of Sullivan 4-40 control rods. I cut up control rods so I have a 3/4" of smooth rod and 3/4" of threaded rod. I use a cut off wheel to nick up the smooth part of the rod and then glue it into the carbon with 30min epoxy. I insert it until the threads stop against the carbon. Thats it!

I tried to pull one apart once..it was impossible.

AlphaWhisky

I use homemade pushrods most of the time. My rods are all ex broken fly rods supplied FOC from my friendly local tackle shop and thus various weights and sizes. ( I strip off the rings and give them back!)

I install a metal rod in each end thus:- I generally use a standard 4-40 threaded rod cut to suitable length and then about an 1/8" long 90 degree bend applied to the shaft end. Drill a hole approx 3/32 dia. in carbon shaft approx 1" - 1 1/4" from the end. Slide the rod into the shaft and hook the short end into the hole. Lock it in place with a piece of small hardwood dowel whittled down to a neat fit with a groove along one side to accept the rod and epoxy it all into place.

I do the other end similar but use a plain rod (ex bike spoke) with a steel clevis silver-soldered to the end. A super cheap fix and never had one fail yet.

Alan W

fwconti

I have been using carbon fiber arrow shafts that I get from my bow hunting brother. They are verry strong and light.
I just cut to length and epoxy a threaded rod inside.