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Author Topic: ST NVA Wear Points  (Read 373 times)

Offline Peter in Fairfax, VA

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ST NVA Wear Points
« on: June 05, 2022, 09:21:21 PM »
One of the contributors here suggests that Super Tigre needles wear from vibration. Wouldn't the spray bar, which is softer, wear more?

Offline Dan McEntee

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Re: ST NVA Wear Points
« Reply #1 on: June 05, 2022, 11:18:47 PM »
   In my experience using the ST-G.51 and stock needle valves, when I start having problems getting consistent needle settings, the first thing I check in the condition of the needle. Where the point passes through the seat, it will wear the needle into a sort of fish mouth condition, and the smooth shallow taper is gone. replacing the needle has always brought things back into control again. I have never had to change the whole assembly. I would imagine that some sort of tool could be made to lap and polish the seat also, but I have never had to do that.
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Offline Brian McGrigor

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Re: ST 60 Best glow pug for CL stunt
« Reply #2 on: June 05, 2022, 11:37:30 PM »
Hi from New Zealand
I am setting up a restored stunt ship with a 1989 Supertiger ST 60
Can you please suggest a suitable glo plug brand and type to use for Sportsman flying
The motor is well run in and started and ran fine recently
Brian

Online Lauri Malila

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Re: ST NVA Wear Points
« Reply #3 on: June 06, 2022, 04:35:14 AM »
Rule number one: avoid closing the needle completely. L

Offline GERALD WIMMER

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Re: ST 60 Best glow pug for CL stunt
« Reply #4 on: June 06, 2022, 05:21:38 AM »
Hi from New Zealand
I am setting up a restored stunt ship with a 1989 Supertiger ST 60
Can you please suggest a suitable glo plug brand and type to use for Sportsman flying
The motor is well run in and started and ran fine recently
Brian

Hello Brian

Only the SIG RC idle bar plug and you will need to order from them:
https://sigmfg.com/collections/accessories/products/sig-glow-plugs?variant=417988706313

Nothing local available in NZ to suit old stunt engines , plugs are becoming a real problem and with the Ukraine situation we have lost a lot of CL supplies.
Regards Gerald

Offline Peter in Fairfax, VA

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Re: ST NVA Wear Points
« Reply #5 on: June 06, 2022, 07:41:10 AM »
> Rule number one: avoid closing the needle completely. L

Yes, leaving heavy tension on the NVA compression nut, then closing the needle could leave an impression on the needle.  Thanks for that suggestion!

Offline Peter in Fairfax, VA

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Re: ST NVA Wear Points
« Reply #6 on: June 06, 2022, 07:45:03 AM »
> replacing the needle has always brought things back into control

Dan,

I am having trouble getting consistent runs.  One day it is 3.5 oz for the pattern, another day 4 oz.  Some laps are 5.6, some 4.9.  Had an over-run at a contest recently, as well, my first time since 1975 in not getting pattern points.  Got it dialed in between rounds.  So I will try a NIP needle today.

thanks,

Peter

Offline Dan McEntee

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Re: ST NVA Wear Points
« Reply #7 on: June 06, 2022, 08:32:26 AM »
> replacing the needle has always brought things back into control

Dan,

I am having trouble getting consistent runs.  One day it is 3.5 oz for the pattern, another day 4 oz.  Some laps are 5.6, some 4.9.  Had an over-run at a contest recently, as well, my first time since 1975 in not getting pattern points.  Got it dialed in between rounds.  So I will try a NIP needle today.

thanks,

Peter

   One thing that I have wanted to try but haven't yet is chucking the needle up in a drill and spinning it at fast speed to dress the point back down again. Look at  you needle closely and I think you'll see the spot where it sits most of the time. It will be just a shallow dip that goes all the way around the needle. When looking for replacement needles, be sure to compare new needle to the old one. There are several different lengths of OEM ST needle valve assemblies .
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     Dan McEntee
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Offline Peter in Fairfax, VA

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Re: ST NVA Wear Points
« Reply #8 on: June 06, 2022, 08:41:39 AM »
Dan,

I'm aware of the three spray bar lengths.  However, I thought the needle were fully interchangeable with same threads/taper, only varying by their lengths.  I prefer very short length for profile/combat, but use longer when needed for full fuse stunters, often finding that the longer ones bend during normal starting/handling, usually with no bad effect.  When heated cherry red, the long ones bend easily.

Peter

Offline Dan McEntee

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Re: ST NVA Wear Points
« Reply #9 on: June 06, 2022, 11:37:21 AM »
Dan,

I'm aware of the three spray bar lengths.  However, I thought the needle were fully interchangeable with same threads/taper, only varying by their lengths.  I prefer very short length for profile/combat, but use longer when needed for full fuse stunters, often finding that the longer ones bend during normal starting/handling, usually with no bad effect.  When heated cherry red, the long ones bend easily.

Peter

  I have accumulated quite a collection of ST. needles over the years and found myself putting in a needle that was too short and wouldn't get the engine lean enough to fly! OS and Enya needles are easy to get mixed up and they won't interchange either, but I don't think there is any other similar type needle that uses the same thread pitch and such as the ST units. In going through my flight boxes and consolidation stuff a while back I got all my ST needles and NVAs in one spot so I could compare and in what I had there were several different lengths of threaded section, pointed section and such. There are several different ST copies of NVAs made these days and I'm not sure if they are all the same. It just pays to check your against other known good stuff.
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    Dan McEntee
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Offline Motorman

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Re: ST NVA Wear Points
« Reply #10 on: June 06, 2022, 12:16:36 PM »
In all my decades of using ST NVA for combat, racing and everything else I've never had any of the problems described here. You guys must have some horrible vibration problems or something.

Motorman 8)

Offline Brett Buck

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Re: ST NVA Wear Points
« Reply #11 on: June 06, 2022, 12:55:07 PM »
One of the contributors here suggests that Super Tigre needles wear from vibration. Wouldn't the spray bar, which is softer, wear more?

  Only problem I have ever had with wear on the ST needle/spraybar,  is that after a while, the very tip end of the compression fitting under the collet wears to the point that the slots close up, so you need to take a Zona saw and cut the slot open again to give it clearance.

        Note also that you need to run the collet as tight as you can get it and still turn the needle, because the needle more-or-less hangs from the slotted end of the compression fitting and can act like a tuning fork at a particular RPM. You can tell whether this is happening on the ground if the setting changes just by touching the end without turning it. In the air, there are many possible causes.  Big Jim discovered that one. This effect is why the OS needles are better - since they are a tight fit on the bore of the spraybar. The same problem might happen with the Jett and PA, except that the threads are much better fit than the ST, and, the compression fitting is teflon or nylon so it act like a damper in addition to a seal.

         Brett

Offline Howard Rush

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Re: ST NVA Wear Points
« Reply #12 on: June 06, 2022, 04:41:02 PM »
Peter and I used many Supertigre needle valves in combat engines with bladders.  One problem I remember was that the .15 size assembly would abruptly shut off the engine.  I figured that the needle was wiggly and when it wiggled next to the hole, the fuel pressure held it there.  Perhaps the unit in question is wiggly. 
The Jive Combat Team
Making combat and stunt great again

Offline Air Ministry .

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Re: ST NVA Wear Points
« Reply #13 on: June 10, 2022, 07:48:25 PM »
Quote
Hi from New Zealand
I am setting up a restored stunt ship with a 1989 Supertiger ST 60
Can you please suggest a suitable glo plug brand and type to use for Sportsman flying
The motor is well run in and started and ran fine recently

Basically , any HOT long reach plug . Tho Kim W wrote a ENYA 4 may be better than a 3 . But NOT the pirate cheap ones !

Were K&B 1s used , L R . . OS 8 or 3 . The Thunderbolt std or idle bar . ESSENTIALLY - if you get a REV DROP when you pull the plug leads ,
itaint otenouh . Tho in COLD weather it might need the leads on for say ten seconds . Definately if its run thirty & youve a switch , flicking
on & off should do nuffin then .

The Olde hold the nose up 45 degrees & shake the snot outoff it to check it , as we combat heroes did , applies .

As does the ' switch ' 2 to 4 stoke & VcV , pul the nose up stedilly . at about 20 to 30 degrees - above it should be 2 stroke . thereabouts. To suit tastes .
AND flipping the ship over , THE SAME angle for the same responce , generally tells you if the tanks shimmed right for even speeds insides & outside manouvers , inveted etc .
Kellets Hobbies in Liverpool had a good range , ENYA plus , anyway . Last time I was there . Most aussie stores do Mail Order . The Qld outfit with the $ 8 Enyas were the Pirate DUD ones !!!!!!!!!!!
Model Sports at Dapto are entutusiast run but erratic , but helpfull . and ENYA ( look on the internet 0 Supply DIRECT - so are a good bet .

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Kneedles !

The Lock Nut , if its not rather tight , you can get the needle tip wooble . or air leaks . So firming it up when the settings in close isagoodidea .

Big Jim put ENYA Needles in His S T's as he recond the tip vibrated , not helping anything . But Big Art put S T needles in everything !

So ENYA if youre atem , the 60 one is for the 60 & the 35 9 small ) onefits the 21/46 etc . same 4 mm / 5/32 in.

a not firm locknut on the ST needle definately cancause uneven runs .


Offline Air Ministry .

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Re: ST NVA Wear Points
« Reply #14 on: June 16, 2022, 12:26:50 AM »
ACTUALLY !

inanold Stunt News , One goes onabout DRILLING the Spray Bar & Fuel Orriface - 1.5 m.m. ( gives a Drill Number - 43 ? at a guess . which IS 1.5 m.m. )
run er through a few times after , by hand , to de ridge & de swarf  . A Good light , held up to , you can see in / through it ! )

says it 'toons easier ' . Ive tried it & it seems to be bouncier & more responsive .

If youve ever tried a FSR 15 / 10 NVA in a G !5 FI , youll know what I mean . No matter how far out the needle is , its never getting enough juice , ion C'Case Pressure , at least .


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