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U/C fixing

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Zflyer25/04/2019 12:06:55
22 forum posts

May not work for everyone but have lost the undercarriage plate ue to long grass or ahem, nearly perfect landings.

I have found using nylon screws/bolts is a good solution as this pull out leaving everything else intact. Just replace them with new ones.

Allan Bennett25/04/2019 20:50:55
1523 forum posts
38 photos

A friend of mine at the flying club used that solution, but the trouble is the nylon bolts keep breaking almost every landing. He wants to use larger diameter nylon bolts, but the captive nuts are inaccessible so he can't change them until the bottom plate comes off again.

Doc Marten25/04/2019 20:58:53
353 forum posts
4 photos

 Have you considered redesigning and replacing the UC with a torsion type? That will never pull out.

 

Edited By Doc Marten on 25/04/2019 21:00:12

Don Fry26/04/2019 06:16:27
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3725 forum posts
42 photos

Bear in mind, a nylon bolt is fragile where the thread joins the head. It to do with the design and how it was cooled when made. After all it was not made for this function.

Try using a length of threaded rod, with a nut glued on instead of a bolt. It's a lot stronger, and has a predictable shear resistance.

Mike T26/04/2019 10:14:20
404 forum posts
28 photos
Posted by Allan Bennett on 25/04/2019 20:50:55:

A friend of mine at the flying club used that solution, but the trouble is the nylon bolts keep breaking almost every landing. He wants to use larger diameter nylon bolts, but the captive nuts are inaccessible so he can't change them until the bottom plate comes off again.

An old friend had a Wot4 with the u/c bolted this way. A less than perfect landing was accompanied by a sharp 'click' followed by many expletives.

Proper nylon bolts will snap near the head as Don says and I'm convinced that coloured ones are worse due to being adulterated by the pigment, so I always use the 'natural' (off-white) type.

You could try using the bolts made by SLEC, which seem more flexible. I'm pretty sure these are polythene or polypropylene.

Zflyer26/04/2019 11:46:30
22 forum posts

I have used a metal washer under the screw head, on both occasions the bolts have come clean away.

However I do not use them again as the threads get damaged.

The off white ones are those I use.

Should they shear inside a hot pointed screwdriver tends to get them out.

David Davis26/04/2019 11:46:53
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3346 forum posts
577 photos
Posted by Mike T on 26/04/2019 10:14:20:
Posted by Allan Bennett on 25/04/2019 20:50:55:

A friend of mine at the flying club used that solution, but the trouble is the nylon bolts keep breaking almost every landing. He wants to use larger diameter nylon bolts, but the captive nuts are inaccessible so he can't change them until the bottom plate comes off again.

An old friend had a Wot4 with the u/c bolted this way. A less than perfect landing was accompanied by a sharp 'click' followed by many expletives.

Proper nylon bolts will snap near the head as Don says and I'm convinced that coloured ones are worse due to being adulterated by the pigment, so I always use the 'natural' (off-white) type.

You could try using the bolts made by SLEC, which seem more flexible. I'm pretty sure these are polythene or polypropylene.

That's been my experience too Mike T! I use black bolts for wing bolts and white bolts for the landing gear. smiley

fly boy326/04/2019 12:50:55
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3475 forum posts
18 photos

If the model is a trainer, and the pilot is a learner he/she may benifit from using banded on u/c until landing procedure improves. Cheers

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