Low profile OS needle?

Stuka Stunt Main Forum · 8 of 8 known posts recovered

mpa · May 25, 2004 11:49 PM

One last question before I roll it up and head for Albany. Does anybody know if OS makes a stub (or low profile) needle that will fit the FP.20/25 spraybar (assembly no. 22311000)? The spring extension on the stock needle tends to get caught on things and it looks pretty ratty when bent- it gives the impression I land inverted a lot.
OS makes dozens of different needle valves but it's not practical to try them all. Yes, I tried the one from the .20/.25 R/C carb and it has a different thread pitch. I know Super Tigre, Jett and Nelson NVA's will fit, but the OS works perfectly with just the right sensitivity to adjustment. And I kinda like the ratchet.
Thanks!
Derek Moran

LNeumann · May 26, 2004 08:14 AM

#1 source

>Does anybody know if OS makes a stub (or low profile) needle
>that will fit the FP.20/25 spraybar (assembly no. 22311000)?
> The spring extension on the stock needle tends to get
>caught on things and it looks pretty ratty when bent- it
>gives the impression I land inverted a lot. (snip)
>I know Super Tigre, Jett and Nelson NVA's will fit, but the
>adjustment. And I kinda like the ratchet.
>Thanks!
>Derek Moran

Derek, OS only makes needles with the spring. That's the bad news. I also agree about the spring. Wish they would make one without.
I do like the ratchet as you mention, and the other needles you mention not only do not have this feature, but they are larger, meaning you have to drill the engine and it will reduce the size of the venturi choke.

OK, here's the good news. You should be able to twist the spring right off. You can then solder a short piece of brass tube to the stub and insert a piece of music wire of the appropriate size in the other end. Then give this a bend at the other end so it looks like an ST type needle, or attach a wheel collar for a knob. Now you have the best of both worlds. You still have the ratchet, you didn't modify the engine, and it looks neat without the spring. We have done this ourselves on several engines. It works fine.

mpa · May 26, 2004 12:34 PM

#2 source

Thank you Leonard.
I don't adjust the needle every flight like many folks do. It's not necessary on a restricted engine set to run below peak. I find a setting and leave it alone unless there is a darn good reason to change it- as indicated by in-flight performance. I log the needle position and RPM for reference, in case the setting is lost. If a change is indicated, it is likely to be one or two clicks, which I do before I start the engine. For this reason I don't need a long extension jiggling in the breeze and getting caught on things.
Your construction method should work very well. I could also just reduce the length of the spring extension by 50-60% to get it out of harm's way.
Thanks again,
Derek

dirtydan · May 26, 2004 03:52 PM

#3 source

Derek,

I have an idea of what you are doing, and I say just whack off whatever you don't need sticking up. Assuming I am correct as to the application, movement of one or two clicks is all that is required, and not very frequently at that. You can simply roll needle between your fingers, avoiding the spring rachets.

Dan

mpa · May 26, 2004 04:38 PM

#4 source

Exactly, but your solution could be accomplished in almost no time at zero cost. . . I think I'd prefer just a bit more to grab on to, but I'll give it another look when I get home. The bodies on the R/C carburator needles would be perfect if they only fit.
Thanks Dan
Derek

dirtydan · May 26, 2004 04:47 PM

#5 source

>Exactly, but your solution could be accomplished in almost
>no time at zero cost. . . I think I'd prefer just a bit
>more to grab on to, but I'll give it another look when I get
>home. The bodies on the R/C carburator needles would be
>perfect if they only fit.
>Thanks Dan
>Derek

Derek,

I should have mentioned that I have one O.S. NVA where the clicks are not easily felt through (bent) spring. So in the cases where a one-click adjustment needs to be made, I am always grabbing the body of needle anyway as that is the only method of being certain the adjustment is correct.

I do apologize for my solution being quick and low-cost, knowing how much you prefer agonizing over details which cost a lot of money to get right.

Dan

mpa · May 26, 2004 06:04 PM

#6 source

That's my professional training. . .
D

gtrbaby · May 26, 2004 07:42 PM

#7 source

I agree with Dan....it is the easiest way to go and works fine....just rip the spring off and use what is left....if you are adjusting the needle before you start the motor then it is easy.....mind you, it is easy to do when the motor is running too...