OS RC Carburetor One-Sided NVA

[Mark Uth]

Does anyone know the thread size (diameter and pitch) for the OS RC engine carburetor one-sided NVA shown in the attached picture?  If so, any leads on where to buy this tap?  Thanks,  Mark

Thread seems to be M4 diameter, but is much finer pitch than standard 0.75 thread.  I don't have an owners manual for this FP model OS Max engine, but that might be a good source if anyone does.  Thanks.

Thanks all!  M4 x 0.5mm it is.  Plenty of purchase options on Amazon.

[Steve Berry]

I would need to check the actual user manual, but at a guess I'd say M4 threads, maybe as small as M3.

Steve

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[Brett Buck]

I would need to check the actual user manual, but at a guess I'd say M4 threads, maybe as small as M3.

   I would just measure it, it will be within a few thousandths of an inch of 3.0, 3.5, 4.0. etc.

     Brett

[Steve Berry]

Just checked. Start with M4x0.5 as a standard thread. I would bring it to Home Depot or Lowes, go to the specialty fastener section, find the metric nuts, and simply go with whichever fits and threads on. That's the size tap to get.

Steve

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[Dan McEntee]

  I know i have made spigot type venturis by using these NVAs for that purpose, and don't recall having trouble finding a tap. I think it's a standard 4mm but can't remember thread pitch, but it was something I had laying loose in my box of taps.
  Type at you later,
   Dan McEntee

[qaz049]

Does anyone know the thread size (diameter and pitch) for the OS RC engine carburetor one-sided NVA shown in the attached picture?  If so, any leads on where to buy this tap?  Thanks,  Mark

Thread seems to be M4 diameter, but is much finer pitch than standard 0.75 thread.  I don't have an owners manual for this FP model OS Max engine, but that might be a good source if anyone does.  Thanks.

A whole bunch of the European and Asian NVA assemblies have M4 x .50
I bought a tap locally, they have a CNC machine that cuts them on the spot.
It's a pretty standard Metric Fine size.

[Steve Helmick]

Just went down in the shop and dug out my metric thread pitch gauge...but couldn't find that sort of NV Assy. BUT, if you have a decent magnifier and metric machinist's scale...or even a machinist's inch scale, you can use them to determine the thread pitch. With metric threads, the pitch number is simply measured from one peak to the next, so if it's .5mm pitch, it's real close to .020" (inches). If you have dial calipers, you could set them at .020" and see if that's it, but you'll still need a magnifier of some sort, and some decent light! 1mm = .03937"...awful close to .040".  Steve

[Brett Buck]

A whole bunch of the European and Asian NVA assemblies have M4 x .50
I bought a tap locally, they have a CNC machine that cuts them on the spot.
It's a pretty standard Metric Fine size.

     There should be no problem funding that here, a really good hardware store would have that (Ace, maybe - our revived local chain "OSH" formerly "Orchard Supply Hardware" until Lowes bought them out and put them out of business, now revived almost unchanged as "Outdoor Supply Hardware" would certainly have that. I once got M3.5 helicoil kit there). Certainly it could be ordered and be there in a few days

    Brett

[James Lee]

It's a 4mm x 0.5
Jim

[Istvan Travnik]

Yes there is a branch of Metric 4 x 0.5 mm threads, all over the world.
One essential exception I have found: the NVA for HP-40 has 4 x 0.35 mm thread. (It is available by MECOA, I bought several times, several pieces from them, on affordable price, in excellent quality. )
Tap for this thread was not a task to buy on eBay...
Istvan

[Brett Buck]

I note that this RC carb part, along with a mounting bracket, used to be sold as the "OS Remote Needle Kit" and is identical to the needle and metering block supplied with the OS-20FP RN. I also used it as a remote needle for a Fox 35.

     Brett

[Dan McEntee]

I note that this RC carb part, along with a mounting bracket, used to be sold as the "OS Remote Needle Kit" and is identical to the needle and metering block supplied with the OS-20FP RN. I also used it as a remote needle for a Fox 35.

     Brett

     The last of the FP- engines all had that rear needle valve set up.  I'm not really sure about the .15 but the .20 through the .40 all did. I may still have a N.I.B .40 like that. That's how I discovered it. My son was still young enough to be prop shy so I set up his models with that engine and worked it out. I figured at the time, the combat and speed guys used remotes NVAs so why not a stunt model. I think I had one on my profile Shark/Twister model while I experimented before I switched it to the first of the Brodak .40s that came  out. That's how long ago that was!! Like I have said before, the biggest issue was learning how much to choke it, and then getting the tank positioned just right so it cut off as clean as possible/. Metal or plastic tank didn't seem to matter. I don't remember if a cut off loop worked or not. years later, I was going through the OS parts listing at Tower Hobbies and found the NVAs, brackets, and the "kits" you mentioned all listed separately and they were cheap enough that I picked up several of each. I went through all of my FP engine cores that had R/C carbs on them to find a few more. The only inconvenience I remember was keeping fuel line on that straight nipple. I found that exactly one wrap of copper wire soldered on the very end, and then sanded flat just a bit helped a lot, and you could still thread the mounting nut over that. . I think the speed limit combat guys still covet these also. I still think it WAY better than the O-ring style that they went back to.

   Type at you later,
    Dan McEntee

   

[Motorman]

Mark, Are you going to thread this directly into a venturi? If so, the nozzel projection and choke area will be critical to draw fuel from a suction/uniflow tank.

I have a friend that did it and he tried to get the engine started for an hour before I looked at it and told him the hole's too big.

Combat and speed planes are different as they have pressurized fuel tanks.

MM

[Mike Greb]

www.aeroracingengines.com has single sided needle valve assemblies for the nelson Q40 and Q500 engines that might be usable for a single sided nva for stunt engines.

[Paul Van Dort]

The Enya NVA version also fits