Tigre 46 needle assembly

Is there a source for the origional needle assembly? Elsewhere there is an old thread that says to us a .173 venturi opening. What effect will it have to use a .190 insted? If I should not use the .190 who sells the .173 or what ever is correct? I picked up one with a .251 delrin opening that someone had drilled through the sides of the base to mount it. When I removed it for cleaning the plugs they had made fell out showing they were not correct. What I want to do is put it back close to origional as I can.

Contact our kind host, bet he has some.

LAST EDITED ON Oct-10-04 AT 10:20 PM (CDT)
 
Leonard, our form host, can supply you with a stock super Tiger NVA and may be able to come up with a venturie for you as well.

On the other hand, if I read your post correctly, your case has been drilled to accept a nonstock NVA/venturie set up. That being the case, you may not the able to go back to the stock system as, most of the time, people will block off the original NV port with a steel plug.

If that is your situation, you might want to send the engine to Frank Bowman. He can set you up with either a box-stock system or if thats not possible, make you a venturie that will duplicate the correct/stock combination using your current NVA.

I am sitting here looking at a custon-built Tigre-46 that has a 285 venturie. Much larger than what you have, but it also has an OS Max FSR NVA installed through the case. That's Big Jim Greenaways set-up. I have, heard tell, that he knows a few things about Tigre-46s and 60s.

It's the combination thats important! There are Lots of ways to skin a cat!

BIGS

PS:
you might want to measure the needle valve/venturie combo that you have now, since It may be what you're looking for!

Read these words of wisdom. This is Brett Buck's advice. I have followed it and it works. There may be other things that work also, but I have followed this and it works.

You want something like a 11.5-6 or 12-6. I flew with as much as a 13-6 at times with very strong rings. The best all-around prop I ever used on the 46 was a 12-6 Rev-Up Special Pro3, greatly cleaned up, with 5.8 basic pitch heading towards 6.3 at the tips. I could get away with 13-5's cut down to 12 and cleaned up in cool conditions at sea level, but it was not enough pitch in the summer or away from sea level.

Modern engines are great and allow good performance with small diameters and low pitch at high revs. The ST46 is not one of these engines, and the old standards still apply - 5 or 6" of pitch, and as much diameter as can reasonably be accomodated.

By the way, the ST really responds well to nitro.

Here's my baseline setup for the ST46 (unchanged since I stopped flying them in 87):
STOCK engine with STOCK COMPRESSION and STOCK HEAD
STOCK sprinkler venturi ( see other post ) with .173 diameter
Tongue muffler with 12 1/8 holes.
Rev-Up Special Pro 2 12-6 with 5.8 and washing in to 6.3 at the tips
SIG 15% nitro fuel (Omega or even Cool Power with a bit of castor will also work)
Uniflow with vent open to air
K&B Long R/C or Glo Devil #300 plug
Brett

I don't see any evidence of the opening for the venturi being opened up. The origional needle openings were plugged but the semi clear plug almost dropped out when I removed the venturi ( It appeared to be epoxy). The needle that was installed was similar to an OS with the spring on the needle but not exactly like my fp engines. I would say that the only modification to it is the hole drilled all the way through from side to side to allow a different needle assembly to hold in the black delrin venturi. I plan to push the delrin venturi into place blocking the new holes that have been drilled and fill them with JB Weld. Then I should only need a standard venturi and the proper needle assembly for that venturi.

LAST EDITED ON Oct-10-04 AT 11:46 PM (CDT)
 
>I plan to push
>the delrin venturi into place blocking the new holes that
>have been drilled and fill them with JB Weld. Then I should
>only need a standard venturi and the proper needle assembly
>for that venturi.

Bill,
I had the same problem and fixed the same as you suggested. It has been working just fine for the last 2 years. DO IT!! The .173 venturi is for the stock needle position.

>Is there a source for the origional needle assembly?
>Elsewhere there is an old thread that says to us a .173
>venturi opening. What effect will it have to use a .190
>insted? If I should not use the .190 who sells the .173 or
>what ever is correct? I picked up one with a .251 delrin
>opening that someone had drilled through the sides of the
>base to mount it. When I removed it for cleaning the plugs
>they had made fell out showing they were not correct. What I
>want to do is put it back close to origional as I can.

That's going to be very difficult. The through holes in the case must be plugged airtight for the original system to work properly, because air leaks into the annular "manifold" will mess it up in the extreme. If you know someone to do very fine TIG welds to weld in plugs, (and then machine it back to the original dimensions) that is a possibility, or maybe aluminum plugs swaged in place. Very tricky, in my opinion.

I would instead suggest sticking with the through hole at this point. It was an unnecessary modification, but it will work OK that way. Lots of people did that back in the day.

A .173 venturi with an ST spraybar, is, of course, grossly too small, since the spraybar is .157 or so. I would start with a .280. This will result in less choke area than the .173 unobstructed hole, but it won't draw fuel as well as the standard venturi for a given choke area.

Of course, close up the other hole somehow - but it's not nearly as critical to get it perfectly leak-free. The "drawbar" that held the R/C carb in place would work fine, and it was far from leak-free.

Bill I have used the ST-46 for many years and still use them.I drilled all my motors for the through the center nv.I used a .292 opening and at times went up to .312. I have seen some of Big Jim's 46's and 60's that were drilled very low so the nv was 1/2 inch off the mounts. I never did that,I drilled all mine near the top on the flat spot 3/4 inch off motor mounts.I have converted some back using the method as mentioned above and it worked fine. I used delrin for the venturi as I could get a very tight fit with no air leaks.I found no difference in performance with ether system. Note the drilled case will use more fuel.All the above is for a stock motor. In the early 80's I did a lot of changes to these motors as we were flying big planes back then and needed more power. I dropped the sleeve, hemi heads and balanced cranks. These motors worked much better with the case drilled.They were very powerful and used a lot of fuel. One mod that will help a stock 46 is have some remove the head fins down to 1/8 inch as the 46 runs to cool with the stock head.
Ed

>Bill I have used the ST-46 for many years and still use
>them.I drilled all my motors for the through the center nv.I
>used a .292 opening and at times went up to .312.

Maybe if you lower the compression, too. .312 seems way too large for stock compression - equivalent to a .195 straight venturi in terms of choke area, which is WAY bigger than the biggest I ever got to work on stock engines. It's much bigger than was used on the average ST60, for instance. If you try a ,312, bring some 25% nitro and an 8 oz tank, that's for sure. I suggest starting at about .280 (a pretty standard size of the time) and working up.

In the early 80's I did a lot of
>changes to these motors as we were flying big planes back
>then and needed more power. I dropped the sleeve, hemi heads
>and balanced cranks. These motors worked much better with
>the case drilled.They were very powerful and used a lot of
>fuel. One mod that will help a stock 46 is have some remove
>the head fins down to 1/8 inch as the 46 runs to cool with
>the stock head.

That's when you could get parts, and complete engines for under $100. And my ST never "ran cool". And with all due respect, the best ST46's were stock engines that happened to have good rings. And I had several mod jobs - as did many of my buddies.

If someone thinks they need more "power" than a stock ST46, a much more effective solution would be to buy a better engine that you can still get. Or better yet, sell the ST on eBay and get 3 LA46s, or a PA or RO-Jett 51. More performance, more durable, more reliable, and parts easily obtained if necessary. And you don't end up performing irreversible experiments on a motor that ran perfectly well stock, and is effectively a collector's item at this point.