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Needle Valve Extensions

How to extend a needle valve

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Tim Cheal23/06/2013 22:39:00
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134 forum posts
33 photos

I am after some help in extending a needle so that it can be turned from outside the engine cowl.

I started with a small Allen key screwed in with the grub nut in the needle an ethics lasted a few flights, but was missing after a flight. So I reverted to wire, bent for some traction, and flattened on one side for the grub screw, but this lasted only minutes. I tried again with epoxy resin, a little better but it has now given in. So, the same again with cyano, on both the wire an the grub nut, and thia appears the best so far, but I fear it will be lost soon enough.

Does anybody have a method of attaching the extension wire or allen key that has stood the test of time?

Tim

Martin Harris23/06/2013 22:55:09
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5827 forum posts
152 photos

I just tighten the grub screw...

If you're continuisly losing the extension, I can only think that you have excessive vibration. I would check the prop and spinner are balanced.

Tim Cheal23/06/2013 23:04:17
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134 forum posts
33 photos

That's a thought, woud an unbalanced spinner (I have balanced the prop) be worse at low revs or high. I ask because it does seem to "rattle" at low revs.

Tim

Martin Harris23/06/2013 23:21:56
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5827 forum posts
152 photos

Might be hitting a harmonic with the airframe at particular revs. What engine/model is it? I have found that some engines are prone to vibration in fairly lightly built airframes e.g. the Saito 82

I can't say that any of my extensions have ever come loose - the original bit of bent welding rod is still in my Chipmunk after more than 10 years of service.

crispin church24/06/2013 08:05:26
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442 forum posts
102 photos

after sorting your spinner out

solder the extension to the needle

Steve Hargreaves - Moderator24/06/2013 09:39:57
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6262 forum posts
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Like Martin I can't remember an extension coming loose!! Might an allen key be a little heavy......thin piano wire around 1mm diameter should be adequate. Grind a small flat for the grub screw to grip & you should be fine.......passing the extension through a small piece of tuel tube where it emerges through the cowl can deaden most vibration....thumbs up

Plummet24/06/2013 10:24:36
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1241 forum posts
39 photos

OR - an old trick from C/L days for extending or repairing broken needles.

Curtain spring. You know the sort of curtain spring that you use for your lace curtains. It is a long spring with a plactic sleeve over it. It is easily cut with plyers. You can cut a short length, then remove the plastic.

Cut the bend off the end on the needle, and solder the end of the spring to the end of the needle.

Solder a replacement bit of wire with a bend into the other end of the spring, and you have an extended and flexible needle.

Plummet

Martyn K25/06/2013 12:40:08
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3684 forum posts
2488 photos
Posted by Plummet on 24/06/2013 10:24:36:

OR - an old trick from C/L days for extending or repairing broken needles.

Curtain spring. You know the sort of curtain spring that you use for your lace curtains. It is a long spring with a plactic sleeve over it. It is easily cut with plyers. You can cut a short length, then remove the plastic.

Cut the bend off the end on the needle, and solder the end of the spring to the end of the needle.

Solder a replacement bit of wire with a bend into the other end of the spring, and you have an extended and flexible needle.

Plummet

Good tip.. yes

Thanks

Martyn

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