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  • January 15, 2021, 04:48:02 PM

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Author Topic: Needle valve assy.  (Read 648 times)

Offline Greg Steffen

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Needle valve assy.
« on: January 10, 2021, 06:59:40 PM »
 OK, so I machined a venturi for my OS LA 40, with a bore of .253. What NVA assy do I need, And who has them? I tried emailing Randy Smith, and didn't get a response. I also need a DECENT NVA for my Fox 35 stunt ( Don't want junk Fox nva) Again, what do I need, and where do I buy it from? My Fox 35 stunts do not have the lugs on the cylinder to mount a muffler, so I will machine my own tounge muffler, unless some one is already doing them, once again... Who?  Thanks, Greg


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Offline Dan McEntee

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Re: Needle valve assy.
« Reply #1 on: January 10, 2021, 07:19:35 PM »
   Find some OS c/l needle valves. I forget the exact diameters, but the original early ones with the black chip board header on the bag was one size, and the last that they produced were a bit smaller in diameter, Some variant of Super Tigre needle valves will work well, but you need to open up the holes in the side of the case, as they are bigger that the OS. RSM sells a ST type NVA, and Randy Smith has his PA brand, and has a size specific for the Fox.35. Just try for something that has the hole in the spray bar end up about in the center of the venturi. if it's off a hair and you can't shim it,. no real worries. Just make sure of a good seal on both sides, and a good seal at the O-ring . look Jim Lee up in the vendors section and give him a call and see what he has on hand for you. Search the engine section also for some ideas and specific information
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Online Brett Buck

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Re: Needle valve assy.
« Reply #2 on: January 10, 2021, 08:31:25 PM »
OK, so I machined a venturi for my OS LA 40, with a bore of .253. What NVA assy do I need, And who has them? I tried emailing Randy Smith, and didn't get a response. I also need a DECENT NVA for my Fox 35 stunt ( Don't want junk Fox nva) Again, what do I need, and where do I buy it from? My Fox 35 stunts do not have the lugs on the cylinder to mount a muffler, so I will machine my own tounge muffler, unless some one is already doing them, once again... Who?  Thanks, Greg

  For the OS, try this one:

https://www.ebay.com/itm/OS-FP-LA-20-46-NEEDLE-VALVE-ASSY-DIRECT-REPLACEMENT-NIP/293139719059?hash=item44407d2393:g:M8sAAOSw5eBcolX7

  The same one will work on the Fox with some spacers, and only slightly reduce the choke area.

    Can't help you on the muffler, without the last version case lugs, that is always an issue.

    Brett

Online Craig Beswick

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Re: Needle valve assy.
« Reply #3 on: January 10, 2021, 08:31:33 PM »
Jim Lee in the vendors corner. Lee Machine Shop.

Can help with supplying and suggest the best NVA if you can't contact Randy.

Craig
Ps. A guy at my club always says Enya NVA with an OS engine, but I don't know I'm still learning.
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Offline Greg Steffen

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Re: Needle valve assy.
« Reply #4 on: January 10, 2021, 08:40:46 PM »
  Thanks for the help

Offline RandySmith

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Re: Needle valve assy.
« Reply #5 on: January 10, 2021, 08:44:18 PM »
OK, so I machined a venturi for my OS LA 40, with a bore of .253. What NVA assy do I need, And who has them? I tried emailing Randy Smith, and didn't get a response. I also need a DECENT NVA for my Fox 35 stunt ( Don't want junk Fox nva) Again, what do I need, and where do I buy it from? My Fox 35 stunts do not have the lugs on the cylinder to mount a muffler, so I will machine my own tounge muffler, unless some one is already doing them, once again... Who?  Thanks, Greg

and the reply  to you email  was  that  I only have  Fox  NVA  for the  Fox 35  and  I do have  PA  needle assemblies  that  many people use in the La and  FP  they are  19.99  and  you will need  to  drill the case  open  to  .157 diameter

Randy

Offline RandySmith

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Re: Needle valve assy.
« Reply #6 on: January 10, 2021, 08:45:44 PM »
Tongue mufflers  are in stock  and are  19.95

Randy

Offline Dan McEntee

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Re: Needle valve assy.
« Reply #7 on: January 10, 2021, 09:22:05 PM »
  For the OS, try this one:

https://www.ebay.com/itm/OS-FP-LA-20-46-NEEDLE-VALVE-ASSY-DIRECT-REPLACEMENT-NIP/293139719059?hash=item44407d2393:g:M8sAAOSw5eBcolX7

  The same one will work on the Fox with some spacers, and only slightly reduce the choke area.

    Can't help you on the muffler, without the last version case lugs, that is always an issue.

    Brett

       I got some of those OS clone NVAs from Bob earlier this year to try them. I had seem some real inconsistencies ith the stock OS NVAs that I had with the blue header card that were the last ones that OS made, and no longer produced. These that the link takes you to, were made by Enya. Bob has a good relationship with the Enya people and he had them make him a batch. They are the same diameter as the last OS unit, which is smaller that the original FP era NVAs, same length and such. Bob cautioned me to watch the torque on the nut when installing them, as there was a fit up issue with them and he was working with Enya on it. When I got mine, I checked the nut against what I had in genuine OS spray bars and nuts, and I reported to him that the nut is too big on the ID. The spray bars were fine, and OS nuts fit them properly.  I don't know if the situation was resolved with Enya on this or not. If you get some of these, just check the fit of the nut on the spray bar threads and see if it is excessively loos or rocks back and forth. I haven't heard of anyone having serious problems with them. I have been wanting to start a thread on this and some things that Mark Hughes and I discovered while we were able to fly together a lot during the Covid shut down this past spring and early summer. I'l do that in the next couple of days or so.
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Online Motorman

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Re: Needle valve assy.
« Reply #8 on: January 11, 2021, 06:16:56 AM »
You made the venturi now make the NVA.


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Offline Peter in Fairfax, VA

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Re: Needle valve assy.
« Reply #9 on: January 11, 2021, 09:13:20 AM »
As in stunt, downhill ski has skill levels.  Beginner / novice / intermediate / advanced / expert.

To me, turning a venturi would be in the beginner / novice range.

However, making an NVA would be advanced / expert.

As far as NVA for an OS LA, and Fox 35 for that matter, my own personal preference is the Super Tigre style, with the tension nut.  The O/S, Enya and Fox click/detent style does not work especially well for me, as I like a very short needle on the profile planes I fly.  As short as practical to clear the tension nut.  This is a carry-over from combat.  An inverted landing should not touch the needle.

As far as vendors for ST style, here is my understanding:

PA, similar design to ST.  Work fine and are available.  Requires a smaller tension nut wrench than the original ST.

RSM clone, very close to ST.  Work fine and are available.

Original ST.  Three lengths, shortest for Fox 35, medium for LA 40/46.  Available used and NOS.  Possibly available new.

best,

Peter

Offline Peter in Fairfax, VA

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Re: Needle valve assy.
« Reply #10 on: January 11, 2021, 09:26:53 AM »
Since the topic of turning NVAs came up, how exactly do you machine the seat?  Drill bit with a certain ground angle?  What is a practical shape for a seat?  I'm just curious; not planning to make one today.

Online Brett Buck

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Re: Needle valve assy.
« Reply #11 on: January 11, 2021, 10:02:19 AM »
Since the topic of turning NVAs came up, how exactly do you machine the seat?  Drill bit with a certain ground angle?  What is a practical shape for a seat?  I'm just curious; not planning to make one today.

   I have cut a few of them apart to see, and they were just drilled with a standard drill, and the angle of the "seat" was irrelevant to the function. The taper on the needle  gave it the proportionality, the "seat" could have been a right angle or anything else.

    Brett

Online Brett Buck

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Re: Needle valve assy.
« Reply #12 on: January 11, 2021, 10:06:05 AM »
Bob cautioned me to watch the torque on the nut when installing them, as there was a fit up issue with them and he was working with Enya on it. When I got mine, I checked the nut against what I had in genuine OS spray bars and nuts, and I reported to him that the nut is too big on the ID. The spray bars were fine, and OS nuts fit them properly.

     I just opened one of the ones I have and checked it for fit. The nut seems OK to me, it's looser than I would have made it, but its' also much deeper than those on the OS, so it has maybe 50% more threads engaged. I don't see a problem - these super-fine threads in brass are always a risk to strip out.

    Limitations aside, these spraybars allow you to run your engine the way it was intended and to *not drill a hole in an unobtainable crankcase* that can't practically be restored without a machine shop.

    In fact, some enterprising "engine person" might offer a set of machined collars that are the OD of an ST or other popular spraybars, and ID to pass the original part, and just long enough to fill up the hole in the case - that could then be JB-Weld'ed into the drilled-out holes to restore them. Operations are face off, bore to ID, machine OD, part off.  ID ~3.52mm, OD .159 (for ST needle, presuming it was drilled using a #21 drill, which will leave sufficient clearance), and length about 2mm.

     For extra credit, same thing, except part off long enough to go through the case and to the nominal-size venturi wall, then to be glued to the spraybar at each end, making a "dogbone" spraybar that takes up the extra space and will retain a damaged drilled-out stock venturi. I have hacked together such things using K&S tubing and shim stock, but a machined part would be a lot better. The only reason the hacked system works is that the fit isn't very critical in that area,

    Brett

p.s. I got out one of my Enya "identical" assemblies, and installed it. The threads are the same between the original OS and Enya copy. The seat seems to be deeper on the Enya assembly , but you can probably use the Enya needle in the OS spraybar, and probably vice-versa. The Enya spring is single-sided but seem to engage the ratchet better than the OS did on it's needle. Everything seems fine about the replacement, seems like it should work as well as the original, although I haven't run it or flown with it.

     I guess I hadn't noticed before today, but the nut doesn't fit any nut driver or socket I have on either one, it's 5.5xx mm which is pretty close to 7/32, but that doesn't fit either. I don't recall having a special wrench in the box, so its some sort of "all 16ths" adjustable wrench, or, that horror of horrors, pliers.

   
« Last Edit: January 11, 2021, 09:42:18 PM by Brett Buck »

Offline Greg Steffen

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Re: Needle valve assy.
« Reply #13 on: January 12, 2021, 06:31:18 PM »
Wow! If I knew I was going to be judged for my machining skills/ ability, I never would have made the statement about making my own venturi. Being a machinist by trade, and having the machine tools in my home shop, I thought it would better to turn it my self. I could make my own needle valve also, but my time is worth far more than the cost of a new needle valve.

Online Brett Buck

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Re: Needle valve assy.
« Reply #14 on: January 12, 2021, 08:25:39 PM »
Wow! If I knew I was going to be judged for my machining skills/ ability, I never would have made the statement about making my own venturi. Being a machinist by trade, and having the machine tools in my home shop, I thought it would better to turn it my self. I could make my own needle valve also, but my time is worth far more than the cost of a new needle valve.

    Oh, yes, making one at home is certainly possible if you have a sufficiently precise lathe. But by the time you get done, it would definitely be working cheap. That's the essence of the hobby business.

     Brett

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Re: Needle valve assy.
« Reply #15 on: January 12, 2021, 08:34:54 PM »
Amazing how many operations it takes to make a NVA. Drilling the length of it is the fun part. I cheat a little and buy the needle stems.


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Offline Dan McEntee

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Re: Needle valve assy.
« Reply #16 on: January 12, 2021, 08:39:40 PM »
Wow! If I knew I was going to be judged for my machining skills/ ability, I never would have made the statement about making my own venturi. Being a machinist by trade, and having the machine tools in my home shop, I thought it would better to turn it my self. I could make my own needle valve also, but my time is worth far more than the cost of a new needle valve.

     I don't have my lathe set up yet but hope to this summer.  I'm a welder by trade and a meat ball machinist by accident and necessity. I have a younger brother who passed away in 2012, and was one of the best machinist you would ever see and had his own small specialty shop. he thought like me, in that yea I could buy it cheaper, but making it just to see if I could is more fun! He had the right equipment to do it, but time is the big enemy.  I would be interested to know what you think f the Enya produced OS needle valve assemblies if you decide to get a few. And if you do, I'll send you an original OS unit that they copied, just to see what you think, since you are in the trade. Other than my suspicions about the fit of the nut , I think the Enya produced part is better.
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Offline Greg Steffen

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Re: Needle valve assy.
« Reply #17 on: January 13, 2021, 03:59:45 PM »
 Thanks Dan, Funny you should mention the Enya NVA, because I did use one in one of my 35 Fox's years ago, and it worked beautiful. Problem is, I don't remember which Enya motor it came from, I would just rather buy some thing that is already proven to work. I could make a needle valve assy., no sweat. Problem is , I don't want to screw around all summer trying to figure spay bar hole diameters spray bar ID's, and all the other engineering headache. I already have a 120" Nostalgia Front engine dragster that I'm building, and I'll tell you what, that thing has me scratching my head every time I work on it! The control-line stuff is supposed to be  my relaxation therapy!  I have been away from the hobby for 30 years, so I don't have many contacts anymore, and the local hobby shops aren't any help.

Offline Air Ministry .

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Re: Needle valve assy.
« Reply #18 on: January 13, 2021, 07:58:19 PM »
 I already have a 120" Nostalgia Front engine dragster that I'm building, and I'll tell you what, that thing has me scratching my head every time I work on it!

Id put a good high tensile scatershield in it .

Whadabout some pictures .

Offline Peter in Fairfax, VA

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Re: Needle valve assy.
« Reply #19 on: Yesterday at 05:10:27 PM »
My apologies if the comment about a venturi insert being an easier project than a full NVA was taken as a judgement of any specific person's skills.  That was by no means my intent.  Tone can be hard to indicate over the Internet.  It was only a general comment based on my impression of the difficulty level.


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