Hi Colyn-
I hadn’t thought of that particular aspect. I did use e-glass rather than
carbon so it wouldn’t be as stiff and might allow some movement. Perhaps
Lancair has a suggestion? :<) The dimensions are meant as an aid to other
builders, not cast in stone. They’re just what the CAD program told me or I
measured after the fact.
I’ve never dealt with pressurization before and it adds a layer of
complexity that I don’t always account for. I’m an airframe mechanic but not
an engineer- my guess would be that the box itself would keep the bellcrank
and torque tube aligned. For the rest there’s the ball joints on the rod ends.
That’s why the twist, to keep the rod ends centered in each bracket for
maximum range of movement.
Now, if IV-P’s vary their wing geometry when they pressurize, all
bets are off.
One might think the aileron torque tube could be affected as it
spans a longer section of the fuselage and might be compressed to some extent.
It might not hurt to have some flex on one end. -Bill Wade
Sent: Saturday, June 18, 2011 9:15 AM
Subject: [LML] Re: IV Aileron Pressure Box Part
2
Bill,
so when your fuselage puffs out there, what will keep this all lined up
to close tolerance?
Colyn
On Jun 17, 2011, at 10:46 AM, Bill Wade wrote:
Two pictures show aligning the box to locate the forward
pivot/crosstube supports before bonding the boxes in place. It took a while
to puzzle out the instructions- page 17-22 shows the forward torque tube tab
upwards. It’s not that way on the ones I got. The thing I worried about was
to make sure there was clearance from the NG well housing and that the
crosstube would be high enough for leg room. The third picture shows how I
went about that.
I used Clark foam to fill the lower gap, then bonded the box
with Hysol followed by 2 E-glass BID on each side. I gather the bottom needs
to be free for movement during pressurization but I did use a couple of BID
to make a collar through the aileron pushrod hole. My intent is to make sure
the box couldn’t debond in that area and it’d remain sealed during
pressurization. The hole needs to be opened out to allow for the extra
material. Also attach the aileron pushrods to the lower bellcrank and check
for clearance through the range of motion to get the hole sized.
When all was done I discovered the wing pushrods aren’t perpendicular
to the aileron torque tube. The lower bellcrank and intermediate rod end had
to be rotated and the shaft holes redrilled until the bellcrank aligned with
the aileron rod end bearing. The forward hole ended up 0.20 inches closer to
the flange face than the aft one. The phenolic covers mistakes. The holes
ended up roughly 0.525 and 0.555 for the forward, 0.726 and 0.750 for the
aft ones; measured from the face of the box flange.
I realize this is more than you asked for and probably more than
anyone else wanted to read but I hope it helps. -Bill
Wade
<Aileron Box
001.JPG><6-12-09 012.JPG><Crosstube
003.JPG><015.JPG>--
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