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Taper pins and weldments

pappa

Member
Seeking some advice. Building a 9A and the landing gear is 2nd hand. The bolt is loose in the main weldments, not bad but loose . A 8 mm bolt takes up all slack. The standard bolt is good going in, but loose coming out the hole. This is for the gear leg. I assume I would have to step up to the oversized AN bolt for this which would require reaming the gear leg and weldment. Also I’d like to do the taper pin mod to the front leg. So, would the very expensive taper reamer do for both the front and the mains if I taper pined the mains also? Thank for your input.
 
There are a number of posts here about taper reaming so a search might be useful to you.

The main gear trunnions are larger than the nose gear. The reamer is long enough to do both diameters but you need to find a taper pin long enough to fit the main gear diameter. Unfortunately, I cannot help you on that particular detail.
 
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See what Bill said above.

Aircraft Spruce sells AN386 taper pins and has a chart for the length. Hope the charts from Aircraft Spruce below help you figure out what you need in length and if you can use the same first dash number pin for both applications. As I understand AN386 taper pins, if the first dash number is the same, you can use the same reamer.

an386.jpg

an386reference.jpg
 
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I have used taper pins especially on a thick wall weldment with a thin or thick inner tube. In the -10 stick assembly there is a joint ( I forgot which one and the plans aren’t available now) where the -3 bolt gave far too much movement. I drilled it undersized and reamed it and it still was unacceptable. I think the aircraft ended with four taper pins when it flew.

I keep a supply of taper pins that are the right size for both -3and -4 bolts but about 2” long and some taper pin washers. Just cut the pin down to the correct length.

Either with a bolt or a taper pin, you have to lock down both parts very tightly and use a good drill press and finish with a reamer. The normal AN bolts are specified to be slightly undersized which by itself can be an issue. You can get zero tolerance bolts from ACS, but sometimes a taper pin is the only good answer, and can save $, weldments are expensive parts.
 
I installed a close tolerance bolt in the nose gear leg on my -7A and it has been fine for about 2 years. The standard AN bolt allowed a small amount of wobble. Vans permits going up to the next size bolt.
 
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