The Spike or Wick type

LAST EDITED ON Jan-29-04 AT 07:50 PM (CDT)
 
I've got one of the Rustler-Merco Metamorph .40 size engines and the needle valve is of the "Spike" or "Wick" type. (Very English, Indeed)

The instructions that came with the engine read.....

PLUS - "We are using a "Spike" needle valve, (sometimes called "wick" or "needle"). This has been well documented in Stunt News as giving either more fuel draw for the same power, or more power for the same fuel draw.

I have also seen this same "wick" or "needle" on the Just Engines web site under the J'EN VENTURI that they sell.

http://www.justengines.unseen.org/jenven.htm

The Just Engines' J'EN Venturi.
Sized similarly to the chart used by P.A.M.P.A.

Hundreds of users Worldwide!!

Just Engines apparently uses the needle valve assy off of the O.S. R/C type Carburetor. Just Engines claims that the "O.S. Needle Valve assembly can be adjusted and wound in or out of the Venturi body - which changes the effective venturi area and therefore allows your setup to be 'tuned' without further drilling or filing!!

This makes sense. I don’t know if it works but I’ve got about ten O.S. Carbs lying around with un-used needle valve assy’s on them.

The reason being; I have a small lathe and make venturi for some of my engines but I have been using Super Tiger, O.S. or PA "Thru Type" needle valve assy's forever.

I must have missed that issue of Stunt News that explains the more fuel draw for the same power, or more power for the same fuel draw thing. What issue was that?

Anybody know where I can get that P.A.M.P.A. venturi size chart. I don't have one of those.

>I've got one of the Rustler-Merco Metamorph .40 size engines
>and the needle valve is of the "Spike" or "Wick" type. (Very
>English, Indeed)
>
>The instructions that came with the engine read.....
>
>PLUS - "We are using a "Spike" needle valve, (sometimes
>called "wick" or "needle"). This has been well documented in
>Stunt News as giving either more fuel draw for the same
>power, or more power for the same fuel draw.
>
>
>I have also seen this same "wick" or "needle" on the Just
>Engines web site under the J'EN VENTURI that they sell.
>
>http://www.justengines.unseen.org/jenven.htm
>
>The Just Engines' J'EN Venturi.
>Sized similarly to the chart used by P.A.M.P.A.
>
>Hundreds of users Worldwide!!
>
>Just Engines apparently uses the needle valve assy off of
>the O.S. R/C type Carburetor. Just Engines claims that the
>"O.S. Needle Valve assembly can be adjusted and wound in or
>out of the Venturi body - which changes the effective
>venturi area and therefore allows your setup to be 'tuned'
>without further drilling or filing!!
>
>This makes sense. I don’t know if it works but I’ve got
>about ten O.S. Carbs lying around with un-used needle valve
>assy’s on them.
>
>The reason being; I have a small lathe and make venturi for
>some of my engines but I have been using Super Tiger, O.S.
>or PA "Thru Type" needle valve assy's forever.
>
>I must have missed that issue of Stunt News that explains
>the more fuel draw for the same power, or more power for the
>same fuel draw thing. What issue was that?
>
>Anybody know where I can get that P.A.M.P.A. venturi size
>chart. I don't have one of those.
>
>Regards,
>John Jolley
>

Hi John,

Can't help you re the Stunt News in question. Don't remember reading it myself but that doesn't mean it wasn't there.

What I can tell you is that when I first got my Rustler I was concerned about the needle valve assembly and actually got some spare intakes and so forth in anticipation of replacing it with a "normal" set-up like the ST or OS.

To be fair to Ian I felt I should run it first as supplied. The new parts never saw the light of day. I was concerned about vibration and the large apparent overhang of the stock needle. This proved on two samples, mine and later Brett's,to not be an issue. The engine runs very smoothly and vibration has not been any consideration. The more open intake without a spraybar through it is technically a superior venturi and a neat plus is the fact that the threaded/with jam nut style of attachment allows the amount of spray bar extending into the venturi to be changed, thus allowing a variable choke area with a single venturi.

The last positive thing is that both the needle and the fuel entry can be on the side of the engine desired. Run it on the right side for a standard ccw flight path and the tubing length is minimized at the same time you keep the needle away from the muffler (if the side exhaust option is selected).

This is a very neat engine right out of the box. I encourage buyers to try it as it comes before assuming any mods are necessary. I love mine.

>Can't help you re the Stunt News in question. Don't
>remember reading it myself but that doesn't mean it wasn't
>there.

I think the instructions refer to the original article about the "Fuel Post Venturi" by Frank Williams. I recall the article and of course I use spigot venturi in my PA and RO-Jett, but I can't remember which issue it was in. I would start looking about 5 years ago.

In general, this works like a charm and *greatly* reduces the tendency to go lean or break into a 2-stroke on hard outside turns. The increased fuel suction for a given power, or more power for the same fuel suction, is a factor I really haven't fully explored.

<<regarding the RM-40>>>>:

>This is a very neat engine right out of the box. I
>encourage buyers to try it as it comes before assuming any
>mods are necessary. I love mine.

I think the "try before fix" is a pretty good idea in general.

The Rustler is a pretty neat motor, alright. Holds a 4-stroke to remarkably high revs, and seems to be a real pussycat as far as setup goes. Best prop so far is a Tornado 10-4 3-blade. Not quite as strong as the AeroTiger or Magnum, but much stronger than engines like the Stalker&Double Star 40.

I have No Desire to "Fix" my brand new engine. I'm going to try and use it in a ARF Nobler. (Maybe when I get the cast off)
I really liked Teds "Tribute to George Aldrich" Nobler. I'm sorry that it got run over. Believe me, I know what it feels like to get run over. (smiles)
I think I'll horse around with the "Spike" or "Wick" type of NVA's on some other engines. I just think its funny how you get used to doing something a certain way (thru type) and forget that there is more than one way to skin the cat.