Long pushrods

[Brian Dorricott 1]

I have an old Funfly kit I recently put together and being 20 years old some of the hardware is a little brittle looking especially the nylon clevis on the pushrods . I measured the pushrod as being just under 2mm and got out the M2 clevis but the thread is wrong . I cannot find any partial threaded M2 pushrod anywhere longer than 300mm and I want about 500mm long. Anyone know of any supplier , I could go to M3 if necessary . I can't use the modern plastic inner/outer job because it's all boxed in without a major rebuild job so stuck with M2 or M3 .

[Keith Berriman]

How about a long 2mm carbon rod with adaptors super glued on ends for clevises. Or a long 2 mm rod and solder the adaptors on

[kc]

SLEC sell a nylon clevis that is a tight fit on M2 rods and has a steel split pin.

[Geoff S]

I use 3mm carbon tube, which has a 2mm hole, and glue in 2mm push rods at each end. Even unsupported, they are very stiff but a little support part way along is evn better.

This was suggested to me by a supplier at the Nats a couple of years ago and it works.

Geoff

[Andrew McKelvey 1]

I tend to use old bicycle spokes which are about 2mm, or just less so I’m not limited to 300mm, run a threaded die up it and you can have a thread both ends, nylon clevises don’t seem to care whether it metric or ba, you just need to source some old wheels. The bent end is good in servo horns you don’t need keepers! You can join the ends using 5 or 10amp electrical connectors (chocolate blocks) if you don’t want to go to the hassle of rethreading, annealing the end helps with cutting new threads

Edited By Andrew McKelvey 1 on 18/08/2020 10:58:10

[Callsign Tarnish]

Other options are M2.5 which is a good compromise, or 3mm carbon rod with adapters either end.

[Martin Harris - Moderator]

Are they supported? I certainly wouldn't want to use 500 mm 2 mm pushrods unless they were.

Have you tried 2-56 clevices e.g.Sullivan?

P.S. The thread diameter will be larger than the rod diameter as the threads should be rolled rather than cut.

Edited By Martin Harris on 18/08/2020 12:53:34

[Nigel R]

"I can't use the modern plastic inner/outer job because it's all boxed in without a major rebuild job so stuck with M2 or M3 ."

do you mean there is a 3mm I.D. housing in there?

[Martin Harris - Moderator]

I may be visualising this wrong set-up but if you're running the rods through holes in balsa intermediate formers, a way of using snakes would be to file some saw teeth on the end of a snake outer and using the existing rod as a guide, feed it over it and cut perfectly fitting holes for the snake. The plastic used is quite tough and more than capable of cutting soft balsa.

[Geoff S]

Posted by Martin Harris on 18/08/2020 12:51:44:

Are they supported? I certainly wouldn't want to use 500 mm 2 mm pushrods unless they were.

Have you tried 2-56 clevices e.g.Sullivan?

P.S. The thread diameter will be larger than the rod diameter as the threads should be rolled rather than cut.

The 3mm carbon tubes I use are quite stiff even at 500mm and certainly better than snakes. I have then on the Liddle Stik I scratch built a month or two back and they work well.

Beware of using bike spokes. Plain 14g spokes are indeed 2mm diameter but the threads are rolled and not cut so 2mm clevises won't screw on. Also I think most ready made wheels are now built with stainless spokes (all the ones I build are) and are often butted 15/17 gauge so thinner in the middle than the ends. If you do use 14g spokes make sure they're rustless rather than stainless or you'll never cut a thread. The spoke thread rollers I have won't work with stainless (they are probably 50/100 years old!) so I always buy spokes to the exact length I need. Though I haven't built any for some time.

Geoff

[Brian Dorricott 1]

I found a length of M3 threaded rod that is long enough and fits into the plastic pushrod tube , I cut this to length and fitted M3 clevis on both ends , this seems a perfect fit and operates perfectly . All I need now is a 3 more threaded rods as the rudder is push/pull and the elevator is in two halves and that may be way forward . The ARTF is a Magic Funfly 90 with recommended 60-90 two stroke so my Saito FA82b should be a good fit .

[Brian Dorricott 1]

I found a length of M3 threaded rod that is long enough and fits into the plastic pushrod tube , I cut this to length and fitted M3 clevis on both ends , this seems a perfect fit and operates perfectly . All I need now is a 3 more threaded rods as the rudder is push/pull and the elevator is in two halves and that may be way forward . The ARTF is a Magic Funfly 90 with recommended 60-90 two stroke so my Saito FA82b should be a good fit .

[cymaz]

Have you considered a closed loop? There would be no slop in the run and you get very positive control

[Brian Dorricott 1]

The rudder is already a push pull using pushrods but the elevator halves are two pushrods into a connector and one metal geared servo . It worked ok on the original pushrods but I don't trust nearly 20 year-old nylon clevis and couldn't find any metal ones to fit the thread . I'll see how M3 threaded rod works when I get it all back together.