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Old Feb 19, 2009, 11:30 PM
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Another needle valve extension question

I have a completely cowled saito 100. I'm trying to figure out how to make a needle valve extension - or more accurately how to install it. If I drill a hole on the side of the cowl and insert a wire, my hex wrench won't reach to the hsn to tighten the set screw.

Or, I might possibly be able to install a wire with the cowl off that will just stick out past the cowl - and do a little finessing with the cowl when I reinstall it to get it out of the hole I drill. But, if I do this, I cant bend the wire, as that will prevent me from removing the cowl. Maybe I can find an old needle valve and cut the end off to make a knob for the wire. I dont know.

What I would really like is some tool that I could insert through a hole that I would drill in the side of the cowl to engage the hsn - something I could insert and remove, perhaps about the diameter of a pencil that would grab the hsn.

Any advice?

Thanks,
Rodney
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Old Feb 20, 2009, 06:11 AM
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Jacksonville Fla.
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I bent tne wire over and insert it through the hole in the cowl as I am installing the cowl...you could file down a small screw insert the shank in the neddle valve and reach through with a screw driver
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Old Feb 20, 2009, 10:10 AM
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Quote:
Originally Posted by jetmech05
I bent tne wire over and insert it through the hole in the cowl as I am installing the cowl...you could file down a small screw insert the shank in the neddle valve and reach through with a screw driver
Thanks, with the cowl unscrewed, I can get , the cowl over the wire, I believe. Unfortunately, I can't finish until after work - so, I won't know how well it will work until then. But looks like it will be fine. I found a quick connector that I can use as a knob. So I won't have to bend the wire. Here's a pic that shows how far I got before work.


Rodney
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Old Feb 20, 2009, 11:16 AM
I meant to do that
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I like to make the hole in the cowl big enough for the needle valve to fit through. That way I can take the whole needle out, put the cowl on the slide the needle with the extension on through the cowl and into the engine. Much easier than trying to slide the cowl over the extension.
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Old Feb 20, 2009, 11:50 AM
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Quote:
Originally Posted by littlewing78
I like to make the hole in the cowl big enough for the needle valve to fit through. That way I can take the whole needle out, put the cowl on the slide the needle with the extension on through the cowl and into the engine. Much easier than trying to slide the cowl over the extension.
You have gone and made me feel dumb - I never thought of that - Great idea! If there is any difficulty getting the cowl on, I'll drill the hole bigger and do exactly what you suggest.

Thanks
Rodney
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Old Feb 20, 2009, 09:44 PM
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Quote:
Originally Posted by rodneygt
What I would really like is some tool that I could insert through a hole that I would drill in the side of the cowl to engage the hsn - something I could insert and remove, perhaps about the diameter of a pencil that would grab the hsn.

Any advice?
Before engine manufacturers began drilling holes in needle valves to receive music wire extensions, this was always a bugaboo situation. I myself soldered a cut-off hex head (allen) bolt to one of my engine's needle valve. I could adjust the needle valve through the engine cowl with a long-shafted allen screwdriver

I guess what I've devised here and wish to share (for what it's worth) is an adaptation of my soldered allen head bolt.

What I have done is take a 1/2 long allen set screw and silver soldered it to a short length of 1/16 music wire. The length of the music wire is adjusted so the head of the allen set screw is just inside the engine cowl. Cut the music wire long at first, of course. You will not be able to cut it longer later if it is too short...

In my case, the engine is an OS FS-52 and has a 1/16 hole in the needle valve and set screw. I obtained a few allen set screws from my local Ace Hardware of a size larger than the diameter of the 1/16 music wire.

I used a drill press at the lowest speed I could adjust to, used cutting oil, and took my time. A 1/16 drill bit does not take a lot of punishment or pressure. I drilled three set screws in case one fell onto my bottomless-pit workshop floor, or something else went wrong during the soldering process, and I intended to take one of the extensions and try to pull the music wire out of the set screw. The depth of the hole stopped above the floor of the socket hole. I did not want to punch through to the socket hole because I did not want solder to flow into the socket hole. Next, I cleaned the set crews in thinner to wash away the cutting oil and remove the drill residue.

I lightly ran the end of the music wire that was going to be soldered into the set screw on a fine grit grinding wheel to scuff it up for a better adhering surface. I used black brazing flux, silver solder (40% Ag) and a lightweight fuel/oxygen torch system.

After soldering and cooling, I placed one of the set screw/music wire fixtures in my bench vise. I attached pair of vise-grip pliers to one end of the music wire and attempted to pull the wire out of the set screw. No dice.

Hope this is of help to others.

EJWash
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Old Feb 21, 2009, 12:00 AM
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USA, OK, Broken Arrow
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Why not just take a dremel tool with a cutting disc, and cut a slot in the end of the needle. You can then use a long small common screwdriver to make adjustments. Long extensions are fine, but it looks to me like vibrations would break them sooner or later.
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Old Feb 21, 2009, 12:04 AM
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Quote:
Originally Posted by GaryParnell
Why not just take a dremel tool with a cutting disc, and cut a slot in the end of the needle. You can then use a long small common screwdriver to make adjustments. Long extensions are fine, but it looks to me like vibrations would break them sooner or later.
Ever try placing a slotted screwdriver in a running engine's needle valve?

The pic of the "long" extension is 6" long. As I explained in the post, the music wire is trimmed down so the head is just inside the cowl.

EJWash
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Old Feb 21, 2009, 01:30 AM
I meant to do that
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Very clever and very nice work EJ. Quite a bit more work but it probably looks nicer.
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Old Feb 21, 2009, 07:17 AM
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I was able to slide my cowl on with the needle without any problems and it looks pretty good - just the little knob in the pic above showing - a fair amount of the wire in the pic was eventually cut off.

EJ, your extension is very nicely done. It also keeps anything from sticking out of the cowl, which I really like. I may attempt making one of these in the future to replace what I'm using.

Gary, I considered slotting the hsn at first but quickly dismissed the idea. As pointed out above I didn't think it would be very easy to keep a regular screwdriver on the engine at 9 or 10K rpm. It's thinking out of the box, though.

Rodney.
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Old Feb 21, 2009, 09:12 AM
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I dont't really have a problem with hitting the slot, but for those that do you can slip a piece of small tubing over the needle valve to guide a small screwdriver into the slot. The main idea is to keep the vibrating mass as small as possible to ease the amount of strain to the needle. I know that large 4 strokes vibrate quite a bit.
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Old Feb 21, 2009, 10:34 AM
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I am fortunate that I have a pretty complete shop so I had the means to perform the task without investing in tools. Once I had the items on hand that I needed (set screws, 1/16" music wire) it took about 20-30 minutes to make the three extensions. That includes taking out the necessary tools and putting them away after use. It actually took longer to take the pics and make the post.

As I mentioned, engine manufacturers began supplying needle valves with the means to use a length of music wire to extend the needle valve to make it possible to adjust it further away from the engine.

Gary posted concern with vibration, and this issue is certainly valid. A long (how long - who knows?) length of music wire extended off of the needle valve MAY whip with engine vibration. The same can be true if the modeler used a smaller diameter wire for this application because that's what they had "on hand."

I was curious as to the manufacturer's suggestions on the subject of needle valve extension, and read over the manuals for several OS and Saito four-stroke (I don't have any glow fuel 2-stroke) engines. Both OS and Saito high-speed (HS) needle valves are machined to accept extensions (hole, set screw). The OS manuals include the following verbiage:

"NEEDLE-VALVE EXTENSION
The needle-valve supplied with this engine is designed to accept an extension so that, when the engine is enclosed in a cowling, the needle-valve may be adjusted from the outside. An L-shaped rod, of appropriate length, may be inserted in the needle-valve knob center hole and secured by tightening the set-screw with a 1.5mm Allen key."

The Saito manuals do not include any reference to HS needle valve extension, which is odd, because I have a Saito FA-45 (in the box) that includes a 3" length of music wire and a small knurled knob with allen head set screw (looks like a wheel collar).

1/16" wire is pretty stout. I guess the proof would be in putting an extension on an engine and running it on a test stand to see the amount of whip, if any, at different lengths.

While I haven't seen evidence of damage or failure caused by vibration due to an extended HS needle valve extension, I haven't seen it all. If vibration is of issue or concern, don't extend the needle valve. What I have witnessed over the years are plenty of bloody propeller-smacked hands and fingers of guys making (more like attempting) needle valve adjustments. Even with a piece of tubing over the end of a slotted needle valve, you still have to poke around the cowling to find and seat the screwdriver. But, if it works for some, more power to them! Can't argue with what works.

EJWash
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Old Feb 21, 2009, 01:43 PM
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I agree to the safety concerns and I guess that if you had a real long way to reach you could have problems with a screw driver and slotted head. one thing that could be done to reduced vibration loads from a long extension would be to get a rubber grommet ( possibly one without a hole in it), mount it in the cowl, and run the extension through it (you would have to punch a tiny hole in it to push the extension through it). That would dampen the vibration ( and look real trick! really nice with a small knurled knob.) In the past I noticed that the hole that I ran my extensions through seemed to "wallow" out and get bigger as time want along. (really bad on fiberglass cowls) I guess that it really wouldn't matter, but on a really good looking plane it 's a shame to watch the cowl slowly erode away.
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Old Feb 21, 2009, 02:36 PM
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Gary,

I haven't seen the small knurled knobs out there before. I wonder why not.

I like the idea of the rubber grommet, but aren't you just transferring the vibration (IF any) somewhere else, like the cowl attachment screws for example?

As far as the exit hole in the cowl for the needle valve extension, the hole should be somewhat larger than the extension wire diameter anyway.

I'll see what the deal is when I run an engine on the test stand.

EJWash
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Old Feb 21, 2009, 03:39 PM
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Yes indeed! the vibration would be transfered to the grommet and then to the cowl. the only thing different would be that the rubber grommet would dampen them somewhat, and possibly take some of the stress off of the extension. This is probably not the best of ideas, but I think it sure would look good. As for the knurled knobs, I think I could probably tool up for a run of them. I don't know if it would be worth it or not. I'm thinking something about 1/4 in. in diameter or so, and about 1/4 in. thick. I have a pretty much unlimited supply of grommets of all different sizes.
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