Control System Q. Section 39, Page 3: F-1089 rod-end engagement

[RV6-KPTW]

Hi,

I am working on Section 39, Control Systems, and have accurately followed directions to create the forward elevator pushrod F-1089. I am concerned that the rod end bearing engagement on either end is only 5/16” not including the jam nut. I am trying to understand what the minimum safe engagement is.

Thanks

 

[Bill.Peyton]

As I recall, AC4313 says 1xD for steel to steel, and 1.5D for steel to aluminum The rod end is 5/16, so that would result in 15/32 engagement. Having said that, it is easy to confuse the rod ends, so make sure you have the correct end. Also,once you install the part in the aircraft, you will be adjusting the entire system for the proper travel

 

[Desert Rat]

Type of material does play into it as bill said, but as a general rule you also want the engagement to be deep enough that it can't unscrew itself enough for either end to come apart. That would mean 1/2 the length of the threads plus a bit.

 

[rocketman1988]

If I were building another -10, I would replace those rod end bearings with ones that have a longer thread; I ran into the same thing. It works but peace of mind is worth something...

Longer threads also assist in adjusting the elevator by eliminating the minimum engaged thread.

 

[Richard Connell]

This is the only rod-end across all RV pushrods where the standard practice of greater than half engagement is not observed. It’s a specific case due to the interference of the WD-1010 tie rod with the F-1089 pushrod at full aft stick.

It’s important that this end of the pushrod is built as close to plans as possible or you will have aileron binding at aft stick. Don’t be tempted to thread it in further. Safety it per plans and all should be fine. Any adjustments should be made at the rear - or better still in the F1090 or F1091 pushrods.

I also looked round for a longer rod end but couldn’t find one.

 

[RV6-KPTW]

[QUOTE="Richard Connell, post: 1935751, member:
It’s important that this end of the pushrod is built as close to plans as possible or you will have aileron binding at aft stick. Don’t be tempted to thread it in further. Safety it per plans and all should be fine. Any adjustments should be made at the rear - or better still in the F1090 or F1091 pushrods.
[/QUOTE]

Thanks all. I will wait till final rigging to evaluate final engagement.

 

[ewumnrr]

If you check the RV-10 Wiki, the engagement is spelled out there:

• Step 5: The long rod end bearing is nominally 2.312" from bolt end to hole and the short one is 1.375. The rod ends are sticking out 0.75", therefore the threads should engage 0.390" into the rod end fitting on both ends to yield a hole to hole length of 37 13/32. Taping the jam nuts into the 0.39 position will make it easy to do the initial thread insertion. 52% of the short and 26% of the long rod end bearing thread is engaged with the rod end fitting.
  Math: (33 + 1.5 + 2.312 + 1.375 - 37.40625)/2=0.39
  

 

[RV6-KPTW]

Martin,

This is close to the question I am asking. Does anyone have a VA-111 not yet installed? Can you measure the length of the threaded area?

Vans support said “… make sure that all the threads in the aluminum fitting are occupied with rod end threads if possible.”

I already put F-1089 together and do not have a good way to measure the threaded area.

Thanks

 

[ewumnrr]

The spec for VA-111 says the thread length is 0.625", so the 0.39" engagement if you build to plans is 63%. Vans only demands over 50%, see page 39-10, step 2.
I built the elevator hinges and the rods exactly to plan and I did not have to change anything. When I did the neutral gauge test according to page 39-10 step 2, it fit exactly.

 

[RV6-KPTW]

Interesting. I interacted with Vans support who could have stated the 50% value but… did not. I see the note now. I had already put the part together and did not know how to evaluate. Where did you find the VA-111 spec? That would be handy to know.

Thanks.

 

[ewumnrr]

Interesting. I interacted with Vans support who could have stated the 50% value but… did not. I see the note now. I had already put the part together and did not know how to evaluate. Where did you find the VA-111 spec? That would be handy to know.

Thanks.

I found the VA-111 spec at Vans when you look up that part and go to the specs tab.

 

[RV6-KPTW]

Thanks Martin. I never noticed the specs before. Very helpful.

 

[lr172]

This is the only rod-end across all RV pushrods where the standard practice of greater than half engagement is not observed. It’s a specific case due to the interference of the WD-1010 tie rod with the F-1089 pushrod at full aft stick.

It’s important that this end of the pushrod is built as close to plans as possible or you will have aileron binding at aft stick. Don’t be tempted to thread it in further. Safety it per plans and all should be fine. Any adjustments should be made at the rear - or better still in the F1090 or F1091 pushrods.

I also looked round for a longer rod end but couldn’t find one.

iirc backing out is not an issue here, as they have you safety wire the bearing to the tube to prevent that. Only worried about ripping threads out and 5/16" of thread engagement is fine for the light loads here.