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General control line discussion => Open Forum => Topic started by: Perry Rose on July 05, 2014, 05:30:52 AM
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I have a S/T .60, the one with a V on the left side, and it has a venturi (not sprinkler) in it that is .274 i.d. with a .156 spray bar going through it. What size should the venturi be? I believe it should be a lot bigger. 12 x 6 BY&O 10% nitro, 61 ounce plane built around the Patternmaster wing.
Thanks in advance.
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It's a trial & error process. I would just fly the thing and see if the power, smoothness, and fuel consumption is OK. Whoever who set the engine up must have thought the existing size was good. If you enlarge it you will probably be disappointed in the power gain.
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Hi Perry,
You should be able to get the info here from lots of people, but you could also check with Dick Carville as he ran his Tigre 60's with the spraybar through the venturi too.
Also you can take a look on this website: http://clacro.de
On the menu click on "design" and then next page click on "venturi"
The diameter of your spray bar is close to 4mm, and the venturi diameter is almost 7mm.
Also on that page it mentions a range for 60 size engines of 12-16mm effective venturi area.
Your current setup is 10.5mm effective area.
I bet you can go up to .283 venturi diameter (7.2mm approx) to get close to 12mm effective area.
-Chris
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Thanks for the info guys. I have what I need to begin the trial and error portion.
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I have run a lot of the ST/60 like yours and I ran a .292 to a .312. Some people run larger if the plane is very heavy. You need fuel in the motor to cool it and help give it the 2-4 run you are looking for. You will need at least a 6 oz tank. I run .292 in my ST/46 motors. Also I run a very shot .5" stack the part the extends above the crankcase. This is the same setup Big Jim used many years ago.
Ed
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I put it in the ball park with a .300 venturi. I ran it a few minutes ago and it's ready for a flight as soon as the winds go away. I can sleeve the venturi if it's too big. The engine kept a good 4 cycle at 8200, before it was mostly 2 cycling at that rpm. My lap times were 5.6 sec. with the engine breaking 2-4 constantly. I measured the venturi on the Evo .60 and the area is the same now.
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Hi, Perry, just passing along some ST 60 info from the late Big Jim Greenaway. Jim's engines were set up with generally .312 restrictors, so the engine would use about 6 ounces of fuel. Jim believed that quantity was critical to allow proper cooling/cycling for the distinctive 4/2/4 "growl" of the old ST 60's. Dave Cook, on the other hand, had success with smaller restrictors, about .280-.285, using only about 5 ounces of fuel to do the pattern. Lots of opinions...Might want to check with Len Harding, as he has built/rebuilt lots of 60's and 46's over the years, to get his thoughts.
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I have a S/T .60, the one with a V on the left side, and it has a venturi (not sprinkler) in it that is .274 i.d. with a .156 spray bar going through it. What size should the venturi be? I believe it should be a lot bigger. 12 x 6 BY&O 10% nitro, 61 ounce plane built around the Patternmaster wing.
Thanks in advance.
Meanwhile progressed to electric, but on my ST 60 I always used sprinklers (with a separate collector ring + needle and NOT the ST needle) and had a set with various diameters to adapt to altitude over sea level.
(http://www.modelbouwforum.nl/forums/members/bruno-van-hoek-albums-diversen-picture104295-st-60-04.jpg)
(http://www.modelbouwforum.nl/forums/members/bruno-van-hoek-albums-diversen-picture104294-st-60-03.jpg)
But a 12x6 is good for a ST .51, IMHO too small for a .60 and a 60 oz. plane!
I always used 13x6 Rev Up wide blade, the last years a Beringer custom prop, narrower blades than the R.U., but about 13.5 dia.
Pitch ranged from ~ 7 at the root down to ~3 at the tips. Giving me a much more constant speed through the manoeuvres.
(http://www.modelbouwforum.nl/forums/members/bruno-van-hoek-albums-diversen-picture53945-neus-ruwbouw-1.jpg)
And 5% nitro, I only flew 7.5% at the 2004 WCh by accident. Foreign fuel, ya know.... ;)
(http://www.modelbouwforum.nl/forums/members/bruno-van-hoek-albums-diversen-picture75122-wk-2004-muncie-indiana-usa.jpg)
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I needed to figure out a different problem with the S/T as it would go a bit rich right after the sq. 8's every time. 5.3 per lap and 5.6 after the 8's. I was thinking fuel tank. I removed the S/T from the plane and installed an Evo .60 and put the S/T on the profile the Evo was on. No other changes. I flew both today and both ran beautifully in their new planes. The S/T on 5 3/4 ounces of 10% GMA from Powermaster ran dry in the pull out to level flight after the clover. So 6.0 ounces should get it done. 5.5 sec. laps launched at 81/8200 rpm. I'll give the 13 x 6 BY&O a try next time out.
Great info guys, Thanks a million.