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WD-421 bellcrank

G

g zero

Well Known Member
The plans for the 8 and 7 show the WD-421-L Bellcrank to be installed in the Left Wing ( makes sense ) On the 9 the plans show the WD-421-L to be installed in the Right Wing . It places the push rod to the aileron below the stick to bellcrank push tube .

Why the difference ???
 
You are correct, the LEFT bellcrank is installed in the right wing and the Right bellcrank goes in the left wing on the RV-9.

Van's used the RV-4 bellcrank in the -9 wing and I suspect that the -9's push tube comes out in a different place than in the -4. By using the -4 bellcranks and flipping them over, Van's reduced the number of parts they need to make. It may provide more differential aileron movement for the -9 than in the other RV's.

It had me confused back when I was building and prompted a call to the Van's help line, where I was promptly straightened out and told that Left means Right, and Right means left. (It is kind of like driving with my wife.)

Anyway, it is nice to know there is a little RV-4 DNA in my -9!
 
I had the same problem in my build...just figured they were mislabeled. Fortunately, they will only work in the correct orientation, but there was a fair bit of head-scratching going on until I had the epiphany. :)
 
The RV-9 doesn't use an RV-4 bellcrank (this is one case where the 4 in the part # isn't related to model #), and they probably weren't mis-labeled.
Because the RV-9 has an airfoil shape that is quite different from the 23000 series, the exit point through the rear spar is much lower (relative to the mounting position of the bellcrank) than the other models.
Because of this, the bellcrank to aileron push/pull rod has to be mounted lower on the bellcrank. By installing the bellcrank upside down from what it is on the other models, it allows the push/pull rod to be installed at the bottom.
 
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WD-421

Thanks for the clarification about the orientation of the BellCrank .
Makes sense now .
 
Hey Scott--Just to make absolutely sure that I've got these installed correctly, here's a pic.

This is the right wing, and the top of the photo corresponds to the upper surface of the wing. The belllcrank is marked "L". I've installed the chromoly pushrod, and everything seems to line up correctly with the spar hole, control horn, etc.

 
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rvbuilder2002 said:
The RV-9 doesn't use an RV-4 bellcrank (this is one case where the 4 in the part # isn't related to model #), and they probably weren't mis-labeled....
Click to expand...

I'm crushed Scott! I so wanted to believe they were RV-4 parts.

No matter, they work well.
 
rightrudder said:
Hey Scott--Just to make absolutely sure that I've got these installed correctly, here's a pic.

This is the right wing, and the top of the photo corresponds to the upper surface of the wing. The belllcrank is marked "L". I've installed the chromoly pushrod, and everything seems to line up correctly with the spar hole, control horn, etc.

Click to expand...

Doug, a bit off topic, but check out EAA's video on applying torque seal. I've never seen a nut completely seize on a bolt because torque seal was applied to the threads, but apparently it's possible. Might save you some headache down the road.

http://www.eaavideo.org/video.aspx?v=29739769001
 
Thanks, Kurt. I'll check it out. I always put a dot of TorqueSeal on top of bolts I've just torqued too as a reminder.

Come inspection time, if the DAR takes issue with the mislabeled bellcranks, I can just show him this thread!
 
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