Control rods, carbon rod and cyano?

[martin collins 1]

I have some control rods to make up on a large model that i am putting an NGH 38 4 stroke petrol engine in and would like to use carbon rods from the servos to the control surfaces. The metel clevices would the be secured with thin cyano, the elevator and rudder servos are under the tailplane so all rods would be quite short. Is this a secure way of making the control rods, would you be happy to use this method and sure that the joints are strong enough? I know a number of you may say metal rods and silver solder but i am not confident in my soldering capabilities to ensure a strong joint. 

[Peter Jenkins]

An alternative to carbon rods is to use metal turnbuckle type rods.  That way you can make minor adjustments to eliminate any electronic trimming by adjusting the rod length mechanically very easily.  3 mm rods should be suitable.

[GrumpyGnome]

Personally, I'd always use something where the clevis and rod are attached mechanically, rather than glued...... but that's just me!  

 

You can always use a die to cut a thread into a metal rod to make pushrods of the correct length - no soldering required. 

[extra slim]

Umm. I find petrols vibrate, I find cyno is brittle and won’t like vibration. I pin my Clevis through the rod and use a less brittle glue. 

[Christopher Wolfe]

I have used a right angled bend on the end of the wire pushrod with a corresponding hole in the side of a carbon fibre tube.

 

Insert the wire and juggle the end into the hole.

 

Then insert a dowel plug of suitable diameter to fit inside the tube with a groove cut to suit the pushrod wire diameter and epoxy into place.

 

It won't pull out.

 

* Chris *

[Ron Gray]

I’ve used carbon rods with thread extenders expoxied on and they haven’t been an issue on any models. Including gassers.

[steve too]

@martin collins 1 I would use studding epoxied or medium cyanoed into carbon tube (2mm studding and 2/4mm tube or 3mm studding and 3/5mm tube) with clevises or ball links.

[Bruce Collinson]

Bind the outside of the CF tube, put a tap through it, epoxy in and put heatshrink over to protect the binding.   Beware the dust.

If you source sensible reverse thread studding which isn’t Chinese putty, please do share with us.

BTC

[Martin McIntosh]

CA by itself does not stick to carbon and easily scrapes off. I do use it on rods at times but firstly spray all parts with Polyolefin Primer (from CPC). This allows you to glue almost anything to anything else, even polythene fuel tanks. So called 2mm rods can have a shallow thread put on which aids adhesion. JB Weld works quite well.

That is a large motor and will cause much vibration; similarly the model will be large and will require rather more robust rods than you would put on a trainer. The suggestion above to use 5x3 tube with a 3mm threaded rod inside is bullet proof and simple so in your case I would recommend that.

[Ron Gray]

Carbon pushrod sets

[MattyB]

11 hours ago, Peter Jenkins said:

An alternative to carbon rods is to use metal turnbuckle type rods.  That way you can make minor adjustments to eliminate any electronic trimming by adjusting the rod length mechanically very easily.  3 mm rods should be suitable.

On a petrol model like this with a fair bit of vibration going on, I agree adjustable metal clavicles and rods are a good choice - it is not like the weight penalty is likely to matter in a model powered by a 38cc engine. 

[Mike T]

I'd use 3mm studding epoxied into 4mm carbon tube with 3mm clevises. 

 

I would not use those turned alloy sockets unless the threaded part was made separately from steel and the socket tapped to take it.  If the socket and thread is machined 'all in one' then the threaded end will bend and/or snap. (T-shirt, etc.)