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Engine basics => Engine set up tips => Topic started by: RknRusty on August 10, 2015, 10:08:24 PM
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I'd like to replace the spring needles on my 25, 35, and 40fp engines with a solid stem type. Sometimes the spring makes it hard to tell if you're turning the needle or just the spring hidden inside of a cowl. And sometimes the knob turns inside the spring.
So, anybody ever heard of a solid stemmed replacement that fits the stock spraybar?
Rusty
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I'd like to replace the spring needles on my 25, 35, and 40fp engines with a solid stem type. Sometimes the spring makes it hard to tell if you're turning the needle or just the spring hidden inside of a cowl. And sometimes the knob turns inside the spring.
So, anybody ever heard of a solid stemmed replacement that fits the stock spraybar?
Rusty
Not that I am aware of, but you can either remove the spring and replace it with tubing, or just solder the spring until it is solid.
Brett
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This isn't a direct answer to your question, but I have remedied that same OS needle problem by applying JB Weld to both ends of the spring to tie it to the knurled knob and the body of the needle with the inside-threaded drum. It may not be elegant but it works.
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yes they did, OS made a thin diameter NVA with a hard needle that you could run in a FP LA with one spacer washer on one side. It was used in the OS 40 and 46 SF control line engines.
you could use a ST , Enya , PA NVA , but they are larger diameter and you would need to adjust the venturie size
Regards
Randy
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Thanks for the replies and suggestions.
I think I'll chop the spring under the knob and stack some tube to fit a 3/32 wire stem, and JB or solder it all in place.
Rusty
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The spring certainly threads onto the needle body and I think it does the same on the knurled knob. Solder a piece of tube onto the needle body and you should be able to either solder a piece of wire into the tube or solder the knurled knob into the tube.
The one warning that I've been given is that the needle is soldered into the body so, you cannot allow the body to get too hot.
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Personally, I don't like the OS NV assemblies and would heave them out in a heartbeat. Randy Aero's are the best! H^^ Steve
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Personally, I don't like the OS NV assemblies and would heave them out in a heartbeat. Randy Aero's are the best! H^^ Steve
Steve, I know and agree, as my flying buddy uses Randy's needles. But my two contest planes are trimmed and the engines are right on-song, so I am reluctant to open them up and unbolt them and start hoping venturi changes will exactly compensate for the spraybar area. After October, I'll have the shop and trim time to upgrade.
Rusty
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Reach in adjust needle at click nob. Cowled motor probably won't let you do that however. Adjust clip so that you can feel adjustment through spring. Hit it right and needle will click adjust without overturning.
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The needles area press fit in the holder. You can press the needle out and replace it withe a piece of drill rod with the similar taper ground in the end. The angle is about 7 degrees included. solder it into the body.
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Reach in adjust needle at click nob. Cowled motor probably won't let you do that however. Adjust clip so that you can feel adjustment through spring. Hit it right and needle will click adjust without overturning.
Hi Dennis, this is on a Nobler ARF. It's stiff to turn because I have a collar of silicon fuel line sealing the base of the needle and spraybar. Maybe that's not necessary. I talked with Ken about it too, and his concern is about the tuning fork effect of a solid stem wearing on the threads. Seems it's happened a few times. Just recently I had that happen to a pair of long Cox needles too. After considering all of the above, I think I'll just solder the base to the spring and JB Weld the aluminum knob on top of the spring. Doesn't look cool, but it'll work dependably.
Thanks for the tips and ideas.
Rusty.