Need help understanding flap bell crank

I have finished building my wood aileron and wood flap; now it's time to figure out the linkage for the flaps. Here is where my confusion comes in.

First, I went to Christian's site (Thanks again) to look at the wing drawings; #14394 Panel Assembly Wing to get a look at parts and set up. Looking at Figure 22 of that drawing blown up, the drawing shows this detail:



Ok so far. In the above drawing, it gives part #40092 for the Flap Bell Crank. Bringing up that drawing I get this:



Well, correct part number but it is labeled " Aileron Bell Crank" and is a different shape. So, off to Univair I go to see what they have. With the same part number, I get this:



and it confirms the info in Figure 22 but is different from the 40092 drawing.

Now for the question; What parts are correct? I am thinking that the "boomerang" shaped bell crank is correct but what is the "T" shaped bellcrank labeled "Aileron Bell Crank" and why the same part/drawing number but a very different part? Looking back at the full wing panel drawing I can't even find an aileron bell crank, what am I missing here?

Although my 2+2 wing is wood, all the dimensions match the metal PA18 wing so the flap linkage will be the same ...... I just need to figure out what to go by. Next will be the cables for the ailerons so I guess I need to know if I am missing something regarding the "aileron bell crank" and is that something I need?

I know you guys can get me on track here. I need to get this right so I can draw it all up for Tim to use on his 2+2 ........ and I guess I can use the info also. :help

Thanks,
Marty57

That tee-shaped bellcrank in the lower drawing looks exactly like the aileron bellcrank on my PA-12. The upper drawing looks like the PA-18 flap bellcrank (also used in my PA-12 by STC). Be wary of drawings for locating the flap bellcrank. The drawings I have for installation of PA-18 flaps on a PA-12 (the STC) result in interferences. Hope this helps a little - -

Marty, notice there is a dotted line that shows the outline of the flap bellcrank vs. the aileron bellcrank used on -12's etc. If you go to PA-18 parts catalog, it will show the correct "-" number.

You Need 40092-10 Left hand and 40092-09 Right hand flap bellcrank not the 40092 print shows a aileron bellcrank and look at your print close it says ( 40092-10 L/H shown dotted)
(40092-09 R/H shown dotted with bolt hole countersunk on opposite side of push arm)
If you look close you see the dotted line were the ear is cut.

So you have the right print you just have to build without the one ear or as you say boomerang style!
Good luck !!!!!!
Steve C.

Bugs66 said:

Marty, notice there is a dotted line that shows the outline of the flap bellcrank vs. the aileron bellcrank used on -12's etc. If you go to PA-18 parts catalog, it will show the correct "-" number.

Click to expand...

wow!

and another example of piper reusing (part of) whats already been designed instead of re designing what they need.... there's a farmer working there somewhere ;-)

Bugs,
I looked it over again and I don't see the dotted line. I see the cross section line at "B" but nothing dotted. Gordon, on the 12 you have both bell cranks? I don't have any -12 drawings of the aileron cable set up. I have drawings of both STC's for 12 flaps but don't remember if it shows both bell cranks. I'll have to get them out. I want to fabricate everything before drilling any holes first but not clear yet. The 18 doesn't use the aileron bell crank does it ?
Marty

Snip attached

Marty57 said:

Bugs,
I looked it over again and I don't see the dotted line....Marty

Click to expand...

Ok, got it now on the dotted line. Thanks. So now just need to figure out difference between -12 and -18 aileron set up with flaps and decide on what way to go. Also need to figure out if I want to pay that much for bell crank or make my own some how with 4130. Any advantage to 12 vs 18? I do want everything inside the wing. 2+2 has aileron cable just behind front spar then into cockpit.
Thanks Bugs
Marty

Yes, the -12 uses the tee-shaped bellcrank for the ailerons, actuated by cables that run between the rear spar and the false spar. The two sorta-straight legs on the bellcrank connect to those cables, and the sorta-perpendicular leg goes to the aileron. The flap bellcranks are the same on -18 and -12. The problem on the -12 is that the aileron cables have to pass by the flap linkage and hinge bracket, and its kinda a close fit, especially since the flap pushrod moves vertically as the flaps deploy.

I'm planning for a trip to Southern Cal this summer, assuming I finish my project. I GOTTA stop at Lancaster and see your craftsmanship!!

darn.... we all fire up the cad programs... (that you introduced me to ;-) )

Marty, I think I have pics - I'll look.

Gordon,
Thanks for looking for me. I'll look at drawings tomorrow from STC's. Mike, Here is my latest from my MAC; 24 x 36 drawing of wood flaps for anybody is interested. just finished the other day. I need to figure out how to attach pdf for full size printing. I will do the same drawing type when I figure out this question here.

Marty

Here are a couple pics. I can't seem to figure out how to attach more than three images, so it will take a couple of posts. Also, I've misplaced my post-restoration wing pics - so most of these are from when I started taking it apart.

Well, darnit! I can't seem to make it work at all right now, and tomorrow's a workday so gotta give up. If you'll send me your email I'll email you what pics I have. Sorry - -

To attach pictures in post click on the little window frame. It brings up Add an image. click on from computer then select. you should be able to find in in your photos and select. If not, email them to me and I can post for others following thread.
Thanks,
Marty

That's what I thought, but it is demanding a URL, like the old days. "From computer" does not show up. GRRRRR! Same in "advanced". I'll try the email link in your profile - - -

Pacers and Tri-Pacers use the same flap bellcrank as well.

Marty, if you use the -12 bellcrank, do not put excess pressure on the bolt that holds the cable to the bellcrank. Over tightening this nut and bolt will cause the ear of the bellcrank to crack.

Kevin,
Thanks for the heads up. Not sure yet on aileron config and no parts yet.
Marty

Use an MS24694S63 screw like Piper did on the 135 and 150 hp Super Cubs. It has a shoulder so you don't over tighten and crack the casting. Cathy found a cracked bellcrank this happened to.

Marty, I am confident that everything will work out just fine for you.

Steve, I don't remember which screw I used. I took the old screw out and took it to my local aircraft bolt distributor and told them I needed 2 just like that. If I remember correctly, it has a countersunk head that fits flush with the top of the bellcrank. There were washers that went inside that bellcrank assembly too but I can't remember if I used the part number from Univair and purchased from them or took the old ones out and went to my aircraft bolt distributor. It's been too long. Where I got them from is besides the point. I just want to make sure to mention about the washers needed. They take up the play between the bellcrank and the housing it sits in.

I was aware and actually anal about the possibility of cracking the bellcranks. I will look again when I pull the wings out of the cradle before covering.

kevin said:

.... They take up the play between the bellcrank and the housing it sits in....

Click to expand...

I think you mean between bellcrank and rod end......

Yes. That is what I meant. Thanks Mike.