I see different values when people talk about pushrods.

2-56

4-40

What do these numbers mean. I was on track of using 2-56s for a size 40 kit. Is that OK?

Are 4-40s used in possible high stress areas?

Thanks

These are thread/size designations. A 2-56 thread is #2 size rod with 56 threads per inch. A 4-40 has 40 threads per inch on a #4 rod. I used to use the 2-56 Quik-Links, but as performance has increased on these things, I only use 4-40s on anything .40 size or larger. There is a tiny weight penalty, but I gladly pay it for strength and safety. I either run solid steel pushrods through Ny-Rod outer sheathes or use Central Hobbies carbon fiber pushrods with titanium ends and Sullivan heavy-duty clevises with jam nuts on the pushrod threads to prevent creep and to lock the treads against vibration.

2x56 or 4x40 are the thread sizes on the end of metal pushrods. The 4x40 is a larger diameter and may be needed if you have larger surfaces and a speedier airplane. If you use either for the full length of the push rod make sure your antenna does not parallel them. If you use Golden Rods or similar plastic push rods and housings the wire rods will require threading into the plastic inside rod.

What would be better in a 40 size trainer. Golden Rods or use the steal ones? Years ago I would opt for the golden rods but back then they did not include the steel rods like they do now. Then it was long wooden dows with wire wrapped around the ends.

I only use 4-40 on Giant Scale. On anything smaller (With the possible exception of competition flying) 4-40 is overkill.

Need proof? Look at my skybolt video. This is a plane that weighs in the neighborhood of 10 pounds powered by a YS 91AC 4-Stroke (Aproximately as powerful as a 120). This plane is over 10 years old and has always flown with 2-56 pushrods.

And as you can see from the video, I don't "Baby" it.

http://204.96.183.34/Skybolt/Videos/

Really? I've always done this and never had a problem. But, I usually run the antennae through a plastic sleeve of its own. Could you clarify this a bit?

If there is a bend in a 2-56 rod... and its more than 1 ft long... its probably inadeqate for more than a .46 powered model. The bend invtes rod flexing.

For a real short pushrod... 2 mm (smaller than #2) is OK on a .60 size model's ailerons if the rod is straight. If you have a bend in it... you need 4-40.

See the Goldberg Tiger 60 ARF... It ships with 2 MM pushrods. If you CAREFULLY align stuff to need no bends... and support the long rods at fuselage exit, mid length and near the servo tray... they'll work. Put a bend in the elevator pushrod... and you need to upgrade to CF tube with 4-40 ends. Put a bend in the aileron pushrods (appx 7 inch straight rod) to use a long servo arm a bit of mechanical differential and the outermost hole on the control horn and you need 4-40.

How you set things up makes a difference in how stiff and strong a material you need for the pushrods.

Excellent video Mike! Those flat spins are fun to do and your Skybolt does them very well.

Thanks ed. Yes, they ARE fun to do, and the Skybolt does them exceptionally well!


I've never had a problem running my antenna parallel to the steel pushrods either.

I've noticed on sailboats that handheld VHF reception (especially from distant weather stations) is much better when standing near the mast and shrouds (aluminum mast/stainless cables).

I suppose if you routed an antenna internally for scale or asthetics and it was EXACTLY parallel to a control rod, that rod could shield the antenna if it was directly between you and the antenna. Our transmitters are line-of-sight and relatively weak. So, put the antenna low in the fuselage where the control rods are above it for most flying if you are concerned. One of my first R/C airplanes (a Sig Kadet) had almininum colored Micafilm. It sure flew badly - must have been due to poor reception.

where does .047 wire fit in? I am building a seagull pc-9 and this wire flexes terribly near the servo when turning the nosewheel. It puts stress on the servo arm and binds the rudder response. I had to adjust the exit hole in the firewall as it was too high for a straight connection to the nosewheel. The guide tube ends about 6" from the servo allowing more flexing . I am fairly new at this and wondered if I might need bigger wire