Torsion pin Ventus replacement

[be...@ebdt.be]

Hi,

Is there someone in this group with practical experience with replacing a wing torsion pin on a Ventus? (V1, V2, D1, D2 are identical)

The replacement pin arrived and the included instructions are very short:
1. heat the old pin at the tip, than you can screw it out
2. Place the new pin with resin and rig the glider for curing
3. check the tangential play and put some distance rings on it if play is to big.
...
We have experience with torsion pins from Glasfluegel and LS but not from SH.
So tips from someone who did this small job re certainly welcome.

Bert - Belgium

[John Sinclair]

Bert,
You must heat the pin in order to loosen the epoxy on the threads. I’d use a small propane torch on the tip of the pin while applying moderate pressure to unwind the pin, so you’ll know when the epoxy gives and remove the heat. Clean up the old threads then mix up a small amount of epoxy and spread it on both threads. Screw in the new pin all the way, then clean up the area to insure there is no epoxy on the outside. Then assemble the bird and allow the epoxy to cure.

Check the wings for fore-aft slop at the wing tips. Any slop can be removed by thin shim washers at the lift pins. It’s a good idea to check the tram by measuring the distance from a common point on the vertical fin to aileron cut-out on moth wings. This will show you where to place any necessary shim washers.
Hope this helps,
JJ

[Christoph Barniske]

Hi,

I replaced the lift pin of our V2cM a few months ago. It's quite straightforward as John described.

In my case it was a bit difficult to unwind the old pin. It needs a fair amount of heating to be unwinded while not overheating the carbon structure. So I shielded the wing root rib from the heat of the electric heating gun with a patch of engine-compartment insulation material made of asbestos/aluminium sandwich. I cut a hole in this patch and put it on the old lift pin. Then I installed a temperature sensor between the patch and the carbon structure with contact to the lift pin. 70°C and a good grip with the pincer were needed to loosen the old pin.

The fore/aft play of the wings were adjusted with a piece of steel tubing that was glued on the lift pin, around 3mm in width. I reused this spacer on the new pin, cutting it a bit shorter so that the main pin went in with a very tight fit. You could use shim washers, but it will take quite a few of them.

Christoph

[be...@ebdt.be]

Thanks for responding, it was comforting :-)

I did one try with a with a heat gun, but we failed to have a good enough grip to turn the pin.
The weekend after we welded a bolt to the end of the pin and probably the heat of the welding was enough to let the epoxy bond go with a small crack (hot to the touch at the threaded tip)

The new pin however was 1/10mm too big and had the thread not 100% centered, every 180° it binded to the cavity.

[John Sinclair]

You may have an as-centric pin that allows very slight wing incidence corrections? I know Schleicher offered them to correct a constant turning problem? The 1/10 mm oversized pin would be to correct slop in the wing attachment……… does the wing slide onto the new pin ?
JJ

[be...@ebdt.be]

It's only the inside part that is very slightly off center and 1/10mm + compared to the original one, but it fits after some work.
Inside the fuselage ball bearing it fits perfectly anyhow. (with some shims)

Bert