McCoy .35 RH NVA - ST vs OS remote

[Terry Caron]

I have an ST nva in my '57 .35 RH which, after turning the spraybar down to ~.125", allowed it to turn a 10-6 to a respectable rpm.
However, on my rotating test stand it was very slow to cycle from 4 to 2 and even slower to come back down to 4.
Needling was also erratic - 3/4 turn might do nothing, then a few degrees might add a couple hundred rpm.
The engine was fresh from a crock-potting and reassembly, so I chalked it up to a need for rebreak-in.

In an earlier thread, on hot plugs, Randy S. had cautioned that the spraybar might break from vibration in time, so I decided to try a remote, relieving it of the mass of the loooooong ST needle and collet nut.
I plugged one end and connected the other to a spare OS remote needle and it needled very linearly, and after about an hour's running 4-2-4'd quite well, with props from 9-6 to 11-6.

I reinstalled the ST needle, thinking now it might act like it has some manners.......but no.
When rotated 90 deg, it still takes a full second or more to go into 2 and at least 5 secs to come back to 4.
Same fuel, plug, props and tank on my test stand throughout.

Now, I have no prob running the remote, MOF I like not having my hand near a spinning prop, but since the ST nva is so often recommended for RH replacement, I'm wondering what the deal is with it.
Anyone have thoughts on why it's so crappy?

Terry

[Andrew Tinsley]

Hello,
At the risk of Brett flaming me. I would not advise using the Rear OS needle valve on an engine intended to do a 4-2-4 style run. I had quite a few rear OS NV assemblies after swopping them out for a front mounted NVA. I am of the age where inadvertent fingers in props are getting too common, so I figured a remote NVA was just what was required. There followed many hours of trials on such things as McCoy 35 and 40s. An odd fox 35 and some early Enya and OS engines. despite everything I tried (and it was a lot!). I found the rear mounted NVAs, were very inconsistent in setting and would change without doing a thing to them.
They work fine on and the usual high revs low pitch prop set up. I even have an odd OS46LA with rear NVA. If you want to run an old style stunt run, then they are a complete waste of time. I also tried a modified TT GP 42 rear set up, using TT bits and the results were the same. It probably doesn't take much guessing as to the cause. The clue is that a metal pipe from the rear NVA gave much better results.

Regards,

Andrew.

[Terry Caron]

Thanks for sharing your experience Andrew.
I've also run remotes on several old engines on the bench but have had no problems with them.
I'll also note that George Hostler has reported  good results with an Evo remote on his .35 RH/Ringmaster.
So far, I've run my .35 RH only on my old CG test stand, set up to rotate 90 deg, but've had no indication of erratic settings.
It's certainly subject to less vibration than on a 'plane, but in any case is much better than the ST needle under the same conditions.

regards,

Terry

[kenneth cook]

              First thing is that all ST spraybar assemblies aren't created equally. Is this a authentic ST needle or a generic copy claiming it's a ST? While they have good adjustment, they're not always leak proof. I've had some where I would replace the collet with a black harder fuel tubing I use for my bladders. This would provide a seal and also friction to the needle to keep it in place. ST needles have a bad habit of loosening the collet when the needle is turned and when a engine vibrates. I would be curious to hear the results if you lost the collet and installed some kind of tubing over the spraybar and onto the needle. Ken

[Brett Buck]

Hello,
At the risk of Brett flaming me. I would not advise using the Rear OS needle valve on an engine intended to do a 4-2-4 style run.

  I am not going to flame you, but that certainly wasn't my experience. Using the old OS remote needle kit on a Fox 35,  it worked just like a regular needle with a puddle of silicone grease to seal the threads (a temporary but useful fix). It might depend on how you assemble your spraybar - I filled in the needle side of a conventional Fox sprabar with a screw and soldered it in place, filled one of the two outlet holes, and then used that.

   In this case, I don't think the spraybar has anything to do with it. If it fails to return smartly to a 4-stroke. I would guess that it is either not fully broken in, or it needs more compression ratio.  The compression ratio is (stock) very low, but the best 4-2 break engines I have ever seen or heard were PTGs McCoy 40s. The front end bearing was *sloppy loose*.

    The stock McCoy spraybar assembly was one of the better ones from that era - I don't think it needs to be replaced until it breaks (which never happened to me, but does happen from time to time).

    Brett

[Terry Caron]

The engine was w/o an nva when I got it and the ST was a recommended replacement so I went with that.
The OS remote works much better than the ST needle and with it the engine cycles between the 2 modes well.
But I'm using the ST spraybar turned down, not simply thinned on each side - the reason for Randy's caution.

As for the authenticity of the ST nva, I can't say - I bought it from Eric Rule, assumed to be ST.
But I'll try it again with Kenneth's suggested mod to see if it makes a difference.
I have ~1.5 hrs rebreak-in time on the engine now and it'll hold at 10.7K rpm, 10-6 APC.

Terry

[George Hostler]

I used the stock McCoy NVA but plugged the needle end with a short 2-56 machine screw and flat washer. Remote Evo NVA provided the needling.

[Terry Caron]

             First thing is that all ST spraybar assemblies aren't created equally. Is this a authentic ST needle or a generic copy claiming it's a ST? While they have good adjustment, they're not always leak proof. I've had some where I would replace the collet with a black harder fuel tubing I use for my bladders. This would provide a seal and also friction to the needle to keep it in place. ST needles have a bad habit of loosening the collet when the needle is turned and when a engine vibrates. I would be curious to hear the results if you lost the collet and installed some kind of tubing over the spraybar and onto the needle. Ken

I reinstalled the ST (?) needle with tubing in place of the collet, wired and twisted over the collet area and over the needle itself as tightly as I dared.
The needle threads are such a sloppy fit it would shock a Fox!
My jury-rig wouldn't hold setting for flying (not enough friction) but on the bench it seems to be better than with the collet, tho' certainly no better than the OS remote.

At this point, I'm still liking the remote.

Terry