W-818 aileron pushrod length

While doing some research on other stuff, I ran across a handful of instances where RV-7 guys built their -718 pushrods (the ones from the cockpit to the bellcranks) to spec, only to find down the road that they were too short. Has anyone run into a similar issue with an RV-8?

I finished up my short pushrods tonight, and I'd like to go ahead and build the long pushrods and have them "stored" attached to the bellcranks in the wings, but I'd rather not find out they're useless in a year or so.

Thoughts? Experiences?

Plans worked fine for me

I have built two RV-8's and followed plans for aileron pushrods lengths. Worked perfectly for me.

Dan Miller
Battle Ground, WA

Follow Plans

Worked fine for me too.

Me too

cdmiller said:

I have built two RV-8's and followed plans for aileron pushrods lengths. Worked perfectly for me.

Dan Miller
Battle Ground, WA

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No problem with the plans I have found. (Hello Dan)

I'm building a 7a and my pushrods were too short. I built two new ones about 5/16" to 3/8" longer.

I don't want there to be any chance a pushrod can loosen and untread itself!

Pushrods

EllisMcgaughy said:

I'm building a 7a and my pushrods were too short. I built two new ones about 5/16" to 3/8" longer.

I don't want there to be any chance a pushrod can loosen and untread itself!

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7a here too. Mine isn't flying but I took your advise and made mine 3/8" longer. I made the short tubes longer too. I just cut the tube in half. Once rigged, I rotated the rod all the way to the end and it couldn't fall out. Good test I learned on VAF.

Built to plans and it's fine (can't unscrew itself from the rod ends).

I don't understand why some people end up short and others don't...assuming everyone is building to the same plans, how can this be?

RV7A Flyer said:

Built to plans and it's fine (can't unscrew itself from the rod ends).

I don't understand why some people end up short and others don't...assuming everyone is building to the same plans, how can this be?

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That's what I wonder, too. I don't want to throw out a blanket accusation of foul-ups on the part of the builders, but it seems like the most likely cause to me.

Anyway, I went ahead and assembled the things tonight. These were a cakewalk after doing the short rods with the solid rivets! Plus, after I was done, I had to temporarily install the bellcrank and both rods, then sit at the wing root and make the aileron move.



Thanks for the feedback!

Mine were built according to the plans and are also too short UNLESS one is to accept that 5/16" insertion depth of the threaded portion (3/8" diameter) into the threaded cone is acceptable, or allow the control sticks to lean towards each other.

I seem to recall that insertion depth should be 1.5X diameter but cannot find that stated anywhere. Can anyone point me to a documented standard?

Bevan

tubes

look at the print there is two length given one for the tube and one for the total length of the finished tube center of bearing hole to center of the other bearing hole you will find the bearings thread into the cone at less then some people think is acceptable to get the total length if you cut the tube to the length given for the tube only

An update for those Google searching the aileron pushrods length issue in the RV-7. The plans drawing 15A shows the total length of the tube and between rod ends. The distance between the rod ends is pretty darn close to accurate for me. The tube however is not. That’s because the drawing shows the Heim M3614M rod end with a disclaimer of “or equivalent”. My RV7 purchase in 2021 came with Aurora 3M-670’s. These are 1/4” shorter from the bolt center to the threads. So, you need to add approximately 1/2” to the push rods to make them fit per spec giving you more thread engagement. If you already cut your tubes, there is a 3M-680 apparently that gives you more thread engagement.

Just passing this observation along from my experimentation.

Cheers

Could the sweep of the wings affect the pushrod length? If you don’t set the rear spar correctly and have some “swept” back or forward wings? I know there’s a process of measuring, triangling, chalk lines, ect.. but could that effect length?