Eccentric cam wing assembly tools

On Monday, October 31, 2016 at 11:48:34 AM UTC-7, Dave Nadler wrote:
On Monday, October 31, 2016 at 2:35:26 PM UTC-4, JS wrote:
Using excess force with a Schempp dump valve misalignment may end in tears.

Oh dear, how do we know this???

Someone gave rigging in "dump" position a try on one of the club's Discus 2s.
Seems like a wing panel makes a good hammer.
Jim

This is a fun thread to read. "How many engineers does it take to ..."?? I say that with many smiley-face emoticons.

FWIW, the simple taper pin that my friend made works 10 times out of 10 with my -29. It's just a delrin pin with a solid handle at 90 degrees to the major axis of the pin. If the wing bushing are misaligned by a few mm, the pin pulls the wings together. If they are misaligned by more than that, it's time to make sure a) the flap handle was in -2 or so and b) the stick was more or less neutral and c) the divebrake handle was at the forward 1/4 or so of travel.

P3

Steve's tool is a bit undersized on the 20 & 27. No problem on the
20 because there's a reasonable taper at the end of the pins –
not so on the 27 where there's only a rounded corner with a tight
radius; so you have to be really fussy lining up to get the first pin
in.

I would love a pin that's ground off at the end so there's only a
few degrees of arc. Then you could rotate to find if the next hole
is high or low. Fingers are not straight enough.

As for marks, I filed a flat spot where the cylinders line up, and a
notch at the maximum difference.

I find that feel works better than vision on a promising soaring
day because my eyes don't adapt quickly to under the turtledeck
when the sun's out.

Another approach that's worked great for me and doesn't require any extra gadgets is to modify the pins for Schleicher ships. The -20 has enough meat sticking out the back of the spar that simply making it more pointy on a lathe works.

I'll try that on the Duo too.

The 27 doesn't have enough extra length for the sharpening process, so I had an insert made that increased it enough to be tapered. A small amount of spar box removal is required to take the extra length.

KS

All of these are great suggestions, and could be incorporated on request. Naturally, some will involve more work and a slightly higher cost, but I am always open to ideas. After all, "R&D" in the aviation world often means "Ripoff and Duplicate."

KS is spot on with tapered pins. Schleicher pins have no taper whatsoever, just rounded ends. If the spars aren't in perfect alignment, the pins clunk hard into the rear spar. I tapered the pins on my Genesus-2 so that the last 3/4" gently tapered down 1/8". With a little dab of lube on the tapered area and a twisting motion, the taper will force spars into alignment. If your pins go completely through both spars and stick out the rear, then it is safe to taper them in the excess area. You can also make a tapered pin out of aluminum. With the aluminum pin in, raise or lower the fuselage (or tip) to bring the second pin into alignment. With the second pin in, then remove the aluminum pin and insert the steel pin.
JJ

On Sunday, October 30, 2016 at 12:24:13 PM UTC-4, wrote:
Steve Bralla used to make and sell tools used to help align the wing spar pin bushings during assembly. He contacted me recently and said he had lost access to the machine shop. He graciously offered me the opportunity to take over the product line, and I am now in production. I will add them to my website shortly (www.mmfabrication.com) If you need one, please contact me through the website.

And a big "Thank You" to Steve!

Would this work with a Ventus? Do you have any photos?

Dennis

Le mardi 1 novembre 2016 16:21:12 UTC+1, HGXC a écritÂ*:

Would this work with a Ventus? Do you have any photos?

Dennis

Yes, works on my Ventus cM.

On Tuesday, November 1, 2016 at 11:48:41 AM UTC-4, Tango Whisky wrote:
Le mardi 1 novembre 2016 16:21:12 UTC+1, HGXC a écritÂ*:

Would this work with a Ventus? Do you have any photos?

Dennis

Yes, works on my Ventus cM.

OK so I slide both wings into the glider but they are resistive to go the final inch. (Typical for me with my Ventus) Then I insert this tool into one of the pins holes .... how does this effect the pin hole of the wing behind the closer wing?

Dennis

Dennis- The tool has a has a large main body the same diameter of your spar bushing (less a few thousandths of an inch for clearance). Extending from that pin is a smaller diameter pin that is offset to the side like a cam. The smaller pin goes in the second spar through the part of the hole you can see. Using the lever handle, the pin is rotated 180 degrees, pulling the bushings into alignment. Assuming the wings are adequately supported, they will remain in alignment when the tool is removed. You can then install the actual steel spar pin.