RE: My 2300 only likes one prop

RE: My 2300 only likes one prop
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RE: My 2300 only likes one prop - 3/6/2006 4:10:48 AM

Cyclic Hardover

Posts: 7221
Joined: 5/7/2002
From: New Mexico, USA
Status: offline

quote:

ORIGINAL: aerobob

I don't hang out in glow engines much anymore, as I've seen the light and started running gassers.... however, I see my name and website being promoted, so thought I'd throw in a comment or two...

First - there has been MAJOR grief with the ST 2300 since it was introduced. It is a very "finicky" motor to get setup reliably and consistently, but it can be done without buying a bunch of after market crap and adding to the wallet depletion.

Second - by design, the motor is supposed to be an "rpm" motor... it is not meant to be lugged with a huge prop load that reduces it's peak rpm range. WHen it gets loaded to that extent, two very important things happen --- one, motor internal temps go through the roof, and if running synthetics, you get scored pistons and destroyed rings and two - there is not enough fuel flow through the motor to properly cool it (fuel going through takes a lot of heat with it out the exhaust).

Third - any motor dies, and nearly any dead motor causes problems. My most recent deadstick destroyed a nearly new GP Ultimate. Ugly. But it happens.

The STOCK ST can be made to run VERY well by following the instructions that come with it. No matter what anybody says to the contrary, this motor is NOT a powerhouse like a OS 1.60 or Moki 1.80.... ain't gonna be, and never was meant to be, and it needs nitro and smaller props. End of story.

Pumps can help - but I have seen them add to a person's woes more than once. Perry carb is good (until you learn how totally screwed up their low end mixture design is) but it ain't gonna make the motor run. Back pressure is needed from a muffler to make the carb draw most efficiently. True story. Rotating spray bars, running idle bar plugs, 30% nitro (cannot believe ANYONE is actually saying to DO that) and all the other stuff MAY help someone....

My suggestion - FWIW - go back to the basics, follow the instructions, make sure the fuel is CLEAN, filtered IN the airplane, that the tank orientation is correct to the venturi, and that the rear end of the clunk isn't more than 12-14" from the VENTURI. And for God's sake - do NOT run all-synthetic....

Signing off now - I sure hope you guys get the motors running well. They are very capable of consistent, reliable performance.

Amen to this.

_____________________________

Retired Army Aviator - Excuse Me! You sold me a hair with a cake around it!

(in reply to Bob Pastorello)

Post #: 226

RE: My 2300 only likes one prop - 3/6/2006 12:53:46 PM

speedster 1919

Posts: 1467
Joined: 12/17/2004
From: Martinsville, IN, USA
Status: offline

Not24 Did your ST carb have the flat bar or round spraybar. Think about this. That ST carb you were trying to restrict is the same carb on Super Tigre's from 40-45-51-61-75-90-2000-2300-2500-3000 except most got the flat spraybar at 61 and up to increase air flow a little. There are far to many of these carbs out there to be considered really bad. The Moki at 30 pounds makes it an expensive choice like the OS7. There is one old time fix I've heard about but never tried. The fuel nipple which is med tubing size is fine for smaller tigres but restrictive for the larger ones. Rather than try to drill out nipple. Take it out and solder a longer brass tube in it's place. Since the tube has no barbs it needs to be longer to hold tubing on or a clamp. You now have a passage 3 times as large.

_____________________________

Hey Buddy -That was the most spectacular crash I've ever seen , That rolling cart wheel with parts slinging out was cool...

(in reply to Not24)

Post #: 227

RE: My 2300 only likes one prop - 3/6/2006 6:47:49 PM

buzzingb

Posts: 1512
Joined: 9/4/2002
From: Bruce, MS, USA
Status: offline

I found Aerobobs comments very intertaining but not in sync with what I have experienced. I started simple and tuned those needles till they were ready to fall out but no consistent midrange and random deadsticks. After spending all summer trying to get this thing going is when I started trying pumps etc. but with no luck. The pump for this engine is not the answer. I fully believe that if I had another carb that my engine would perk up like Not24s. Later this spring I plan on going that rout and purchase a carb. The first think that came to my mind while reading his comments were exactly what Not24 said about some motors being good runners and other not. I don't doubt that many people have 2300 that run well but mine would not so I have spent over a year trying differnt things. My last thing to try is the carb and if that doesn't do it then forget it.

_____________________________

Buzz

(in reply to speedster 1919)

Post #: 228

RE: My 2300 only likes one prop - 3/6/2006 7:11:44 PM

Bob Pastorello

Posts: 5292
Joined: 2/23/2002
From: El Reno, OK, USA
Status: offline

The ability of that motor to operate in midrange is absolutely, completely tied to the angle of the groove in the drum rotor. That, and the concentricity of the spray bar where it rotates as it opens the cat's eye at the end of the idle needle. If your spraybar is NOT absolutely concentric, or the needle o rings slightly worn, permitting the idle needle to wobble - you will NEVER EVER get a reliable and smooth transition. Very few folks get into that carb deep enough to understand the mechanical tolerances and interplay between that low speed needle, the venturi, and it's impact on the high speed. Then, of course - ALL of that interplay is controlled by two things -
1. Tension of the spring that is pushing the drum rotor toward the low needle and 2. The machining tolerance of the rotor GROOVE and the SET SCREW that controls the rate of angular change during rotation. That set screw can wear, it does wear, the spring can get weak, which then means it doesn't resist the drum rotating of the low needle (and THAT is what causes the throttle-up-rich-and-die-transition).

I could go on, but I doubt anyone is really truly interested in learning the vagaries of the internal workings of the STOCK carb.
It's all about tolerances.

Whether you agree, or don't, is irrelevant.
My facts are irrefutable from physical evidence.... learned painfully at the U. of H. K.

_____________________________

Bob Pastorello www.rcaerobats.net
Learn from others...you can't live long enough to make all the mistakes yourself....

(in reply to buzzingb)

Post #: 229

RE: My 2300 only likes one prop - 3/6/2006 10:02:04 PM

Not24

Posts: 999
Joined: 12/7/2002
From: Gloucester, VA, USA
Status: offline

quote:

ORIGINAL: speedster 1919

Not24 Did your ST carb have the flat bar or round spraybar. Think about this. That ST carb you were trying to restrict is the same carb on Super Tigre's from 40-45-51-61-75-90-2000-2300-2500-3000 except most got the flat spraybar at 61 and up to increase air flow a little. There are far to many of these carbs out there to be considered really bad. The Moki at 30 pounds makes it an expensive choice like the OS7. There is one old time fix I've heard about but never tried. The fuel nipple which is med tubing size is fine for smaller tigres but restrictive for the larger ones. Rather than try to drill out nipple. Take it out and solder a longer brass tube in it's place. Since the tube has no barbs it needs to be longer to hold tubing on or a clamp. You now have a passage 3 times as large.

It's got the round spraybar. The fuel nipple is not the point of restriction on the carb. The diameter of the hole thru the spraybar is. Even given that, fuel flow is not the issue with the ST carb. It flows plenty of fuel. Its problem is that it doesn't DRAW fuel. It doesn't atomize the fuel properly and spits raw fuel out the exhaust. It'll do this at any power setting. The venturi is just simply too large and takes in too much air, so to get a good running mixture you need to load it up with fuel. By reducing the air intake, you increase the intake velocity, which aids in fuel draw. Now that you have less total air entering the engine, you need less fuel to mix with it to get the mixture right. By injesting smaller gulps of fuel and air, the atomization is better, and fuel economy increases. Now just prop it right, and you don't even realize a loss of power. Is the size of the venturi the only issue with the ST carbs? I don't think so. I think there are many contributing factors, manufacturing tolerances being a big one.

_____________________________

Fly it till you break it!

(in reply to speedster 1919)

Post #: 230

RE: My 2300 only likes one prop - 3/6/2006 11:11:34 PM

Daryl Martel

Posts: 595
Joined: 2/10/2002
From: WinnipegManitoba, CANADA
Status: offline

aerobob - Bob, I've downloaded your tuning tips from your website (a long time ago!) and have 20+ years in the hobby. I consider myself reasonably decent at tuning engines (I'm an aircraft mechanic). I know what you mean about the criticality of the carb needle being centered in the spray bar, but my carb never metered correctly across the entire RPM range from new, i.e. right out of the box. Many have reported similar experiences, so it's not a "wear" issue - it's got to be design, manufacture/assembly, etc... I suspect that S.T.s machining (just of the carb I'm talking here) and/or quality control may also be at fault. Too many people that are otherwise experienced, successful modelers report woes with this engine. I'm not in any way putting down your extensive experience or your post, but there has to be a real (not perceived) problem with these carbs. People swap carbs and get instantly better transition - doesn't that say it all? O.S. must have made a killing already selling the O.S. 7D carbs for the big tiggers - look, a readily available adaptor sleeve!!? You don't exactly see this every day do you. These 2300s and the 3250s are performance bargains, but I'm not crazy about the stock carbs.

< Message edited by Daryl Martel -- 3/6/2006 11:14:27 PM >

_____________________________

Spending my daughters inheritance one plane at a time...

(in reply to Not24)

Post #: 231

RE: My 2300 only likes one prop - 3/6/2006 11:21:34 PM

Bob Pastorello

Posts: 5292
Joined: 2/23/2002
From: El Reno, OK, USA
Status: offline

Daryl, you are EXACTLY correct. I wasn't saying "the design is good"; I was sharing that the reason it is so hit and miss is the ol' proverbial "expansion of tolerances in all directions". I truly think that could be an issue with this motor, with the "average" being the ones that royally SUCK.... and the ends of the bell curve being "won't run no matter what" and "runs fine per instructions".

My findings and experience simply is shared to help anyone on the good end of the tolerance curve.

The solution for everyone else, IMHO, is a different motor.

The ST2300 is a PRIME example of throwing good money after bad, and a person who can't see the forest for the trees just keeps on investing.

It ain't NEVER gonna be a silk purse..............

_____________________________

Bob Pastorello www.rcaerobats.net
Learn from others...you can't live long enough to make all the mistakes yourself....

(in reply to Daryl Martel)

Post #: 232

RE: My 2300 only likes one prop - 3/6/2006 11:27:13 PM

Daryl Martel

Posts: 595
Joined: 2/10/2002
From: WinnipegManitoba, CANADA
Status: offline

Darned - I guess that's why all the pattern guys so quickly abandoned them. I had mine originally in a Midwest Giles. Killer combo, but the engine really only ran great flat out. No shortage of power. Too bad, I was really hoping S.T. would knock O.S. off their post a little and bring the price of pattern engines down from their exorbitant levels. I can seriously see the advantage of going gas, especially for pattern guys putting lots of training flights in. If nothing else, these engines are available cheap.

_____________________________

Spending my daughters inheritance one plane at a time...

(in reply to Bob Pastorello)

Post #: 233

RE: My 2300 only likes one prop - 3/7/2006 12:06:04 AM

buzzingb

Posts: 1512
Joined: 9/4/2002
From: Bruce, MS, USA
Status: offline

I with Not24 on this issue the carb venturi is too large and the metering isn't right, plane and simple. A simple carb swap should solve the issue. Question is which carb is the best OS, Magnum, Jett, Moki and how much will it cost? The 2300 at $125 and the cost of a good carb will still be cheaper than some other engines out there. I am going for it.

_____________________________

Buzz

(in reply to Daryl Martel)

Post #: 234

RE: My 2300 only likes one prop - 3/7/2006 1:54:35 AM

speedster 1919

Posts: 1467
Joined: 12/17/2004
From: Martinsville, IN, USA
Status: offline

Not 24 That same carb on a ST .40 should just flood that engine with fuel , but they don't. Cause a 1.40 spits out raw fuel at all levels. The round spraybar is fatter and takes up more volume in venturi limiting air flow. The flat spraybar takes up less volume to allow more air to come in and produces more suction to get more fuel to feed a 1.4 cu engine. I forgot if you have the dogleg slot barrel or the straight angle cut. If it were my carb I would make sure I had the flat spraybar and straight cut barrel grove. You can take a file and flatten the round spraybar on both sides. Now that you butched the cats eye it is probably shot. Drill out the nipple a little larger and use large fuel tubing from tank. Center the cats eye in venturi even..... (9:00) level nipple. turn low needle in till it blocks off the cats eye half way. Turn out the HS needle 3 turns. 17" prop. get close but rich high speed and lean the LS needle for pinch test with 100RPM increase. But thats me. Super Tigre admitted the round spraybar in some carbs was wrong and the dogleg slot was a misstake.

< Message edited by speedster 1919 -- 3/7/2006 1:59:21 AM >

_____________________________

Hey Buddy -That was the most spectacular crash I've ever seen , That rolling cart wheel with parts slinging out was cool...

(in reply to Not24)

Post #: 235

RE: My 2300 only likes one prop - 3/7/2006 4:07:51 AM

Not24

Posts: 999
Joined: 12/7/2002
From: Gloucester, VA, USA
Status: offline

quote:

ORIGINAL: speedster 1919

Not 24 That same carb on a ST .40 should just flood that engine with fuel , but they don't. Cause a 1.40 spits out raw fuel at all levels. The round spraybar is fatter and takes up more volume in venturi limiting air flow. The flat spraybar takes up less volume to allow more air to come in and produces more suction to get more fuel to feed a 1.4 cu engine. I forgot if you have the dogleg slot barrel or the straight angle cut. If it were my carb I would make sure I had the flat spraybar and straight cut barrel grove. You can take a file and flatten the round spraybar on both sides. Now that you butched the cats eye it is probably shot. Drill out the nipple a little larger and use large fuel tubing from tank. Center the cats eye in venturi even..... (9:00) level nipple. turn low needle in till it blocks off the cats eye half way. Turn out the HS needle 3 turns. 17" prop. get close but rich high speed and lean the LS needle for pinch test with 100RPM increase. But thats me. Super Tigre admitted the round spraybar in some carbs was wrong and the dogleg slot was a misstake.

I don't know where you read that I did anything to the cat's eye. I did not. I only did two things to the stock carb. Enlarge the fuel nipple and alter the metering slot in the barrel. I admit that I now have a better understanding of what the metering slot should look like, and I can still fix it, but there is more wrong with that carb than just that slot. I just took some measurements that you may find interesting. I measured the velocity stack at the inlet and the barrel, and I measured the hole thru the barrel on both carbs. On the Magnum the measurement includes the restrictor sleeve.

ST carb .560/.430/.460 (barrel)

Magnum carb .590/.455/.388 (barrel)

As you can see, these dimensions are very different. The most noticeable difference is that on the ST carb, the hole in the barrel is bigger than the base of the intake, and the magnum carb has that hole quite a bit smaller than the base of the intake. Bernoulli's theory says that as velocity increases, pressure decreases. The velocity in a venturi is the highest where the diameter is the smallest. This puts the vacuum upstream of the spraybar in the ST carb, and at the spraybar in the Magnum carb. The spraybars are not the same diameter, with the ST one being larger. The amount of choke that the spraybar adds is only that. It is more of an obstruction to the flow than an increaser of the velocity due to reduction of area. I'd say that to get the ST carb to function properly, one thing to try is to sleeve the barrel to a diameter that is smaller than the base of the intake. .400" looks like a number that would work. My engine runs fine with the Magnum carb, so I'm not going to play with the st carb any more. Maybe in the future my curiosity will get the better of me, but for now, I am done. My testing from this point on will be limited to fuel and propellers.

_____________________________

Fly it till you break it!

(in reply to speedster 1919)

Post #: 236

RE: My 2300 only likes one prop - 3/7/2006 3:17:37 PM

downunder

Posts: 3198
Joined: 10/10/2002
From: Adelaide, AUSTRALIA
Status: offline

quote:

ORIGINAL: Not24
ST carb .560/.430/.460 (barrel)

Magnum carb .590/.455/.388 (barrel)

The velocity in a venturi is the highest where the diameter is the smallest. This puts the vacuum upstream of the spraybar in the ST carb,

It's total area that counts and the spray bar is an integral part of the venturi and not just an obstruction. With your measurements, the total area under the barrel (.430 diam) is .145 sq inches. Now if the big ST's use the same diam spray bar they seem to use in just about everything it'll be .156" which gives a total area in the barrel of .094 sq inches after subtracting the spray bar area so the fastest airflow is still at the spray bar. The Magnum starts at .118 sq inches (in the barrel) so even with a smaller spray bar the area is going to be less than the ST.

(in reply to Not24)