Fuel Fed Problem
 

Need some advice. On my Intruder, OSMax61FX, mounted upright. This engine has needle valve assembly at rear of engine. This puts it about 1.125" higher then the clunk line from tank. It draws fine, except when going to outside loop. Enter, cut throttle for downside, engine cuts out, wants to quit. Roll upright, apply power, comes back fine. Should I go to a pump ?
If that is the answer, which one?

Vince

RE: Fuel Fed Problem
 

I would contact the guy who started this thread, http://www.rcuniverse.com/forum/m_7618521/tm.htm , and make him a deal. You would be very happy with the YS 61. You could then buy the Mecoa 930-61 muffler and be in business. The YS doesn't care where your fuel tank is located.

RE: Fuel Fed Problem
 

AirBus - Thanks. YS engines are great, but I am moving on to Rossi 60's in Phoenix' under construction now. Looking for primary FNV engine's. I have run the first Rossi, great idle and transition. Without going to new mfg of engines, (YS), I will try a pump with this OS61FX set-up. What can be causing the fuel draw problem with the Intruder?

Vince

RE: Fuel Fed Problem
 

Some people have had luck with pumps. Others have not. My experience was dismal. You also need the space to install them which you probably don't have a lot of in that plane. I'd bet you a dollar to a doughnut, as my dad used to say, that if there was a YS 61 installed in that plane, you would never take it out after you saw how well and reliably it ran. The problem you may have with a pump(I assume you mean Kline) is that now your carb has to suck(venturi) the fuel. Where as before it sucked fuel that was under some pressure from the exhaust pressurized tank. Depending on your carb, this difference could cause significant tuning and stable running issues. Also, you are going to have to drill a hole in the crankcase(back plate or side of engine) and install a pressure tap. And after the pump maybe not being successful, you will alway have a threaded hole to keep sealed in your crankcase. There is an old engineering axiom that says "Why solve a problem you can eliminate." Oh, one other thing to keep in mind, the pressure regulator(Kline) will have to be mounted between your needle valve and the carb. As I recall, the regulator must be within about an inch of the carb, not the needle valve. So in that short stretch between the needle valve and carb you will have to mount the regulator. If I remember my Perry pump investigation, they were sometimes not as effective with the high speed two strokes as the pump is "powered" the shaking(vibration) of the engine. The smoother running two stroke engines sometimes didn't vibrate enough to operate the pump. They were better suited to four-strokes. But good luck in your solution.

RE: Fuel Fed Problem
 

Thanks AirBus, your reply sez it all. Good info. I will work on it.

Vince

RE: Fuel Fed Problem
 

Does the condition change if the tank is completely full compared to a lower fuel level?

RE: Fuel Fed Problem
 

Try changing the low end needle. I suspect it's too rich. Try a couple of clicks leaner and if that doesn't help go a couple of clicks richer.

RE: Fuel Fed Problem
 

I always found the key to even draw in all maneuvars was making sure the clunk tube out of the tank was centered on the spraybar of the carb. The location of the needle should not affect you that much. If you are running muffler or pipe pressure it should work well.

Jeff

RE: Fuel Fed Problem
 

Crankpin:
Make sure the centlerline of the tank is in line with the inlet on the engine or no more than 3/8" lower. What is happenning you are setting the engine for upright run, when inverted the tank centerline changes (becomes higher than inlet) and it goes rich. Move your tank up or down to get the tank center line in line or close to the fuel inlet on the engine. The location of the needle valve in this case does not matter much.
Stay away from pump, I have never had ean engine that needed a pump even when the draw was long way off ( in that case I use a hopper tank setup). You may want to think about that if you have the space for a 2 ounce tank up front, and put the main tank further back. If done correctly, you can get setup your airplane where the CG does not change throughout the flight, unless you run the hopper tank dry.
Call me if you need assistance.
Orlando

RE: Fuel Fed Problem
 

Thanks everyone. Tank placement in relation to the NVA, could not do it with this setup. If I mounted the engine sideway's as the plans call for, all would be fine. I would be in better shape with a slant sullivan or other. Problem there is drilling the firewall thru the nose gear and engine mounts. Not workable.....yet.

With this rear NVA and the banjo on the vertical NV, that is where my problem is. With this OS, I can mount the NV and banjo vertical or horizontal. Horizontal would lower it some, but not that much. See attached. I may try to put a slant tank in, this will bring the exit of lines up closer to the NVA. Lot of space in that area.
Thanks for all the help, thinking about the slant tank line exit, any comments appreciated.

Vince

RE: Fuel Fed Problem
 

I don't know if this will help; can you mount the tank upside down?

RE: Fuel Fed Problem
 

Upside down mount. Present tank is same, upright or down. Sullivan RST-10, center exit, I think it is called RST, just a regular tank.
I have tried to mount one of those tanks that look like a whisky flask with the exit on one corner, no go.

Vince

RE: Fuel Fed Problem
 

I had a simular problem back in the 90s with my Atlanta/Rossi set up. Tried about everything, change tank, lines, location, I didn't add a hopper tank though. I'm pretty sure that would have settled it up, and made for a nice constant c/g as crashlander stated, I just haven't heard of that set up yet. I ended up adding a perry regulating pump on it. Worked out great after that. No issues until a tree jumped into my flight path! [:@]


DM

RE: Fuel Fed Problem
 

Those Dang Jumpin' Trees... :D

RE: Fuel Fed Problem
 

The hopper tank is a simple and reliable system. It utilizes a second tank considerably smaller say 2-4 oz. The main tank is placed on the CG of the airplane. Muffler pressure or crankcase pressure is supplied top the main tank, fuel is then transfered to the small tank which feeds the engine. The small tank is never run dry.
Simple and very effective. The small tank is adjusted to be at the correct position to achieve constant flow no matter the attitude of the airplane.
The added values are consistant engine runs and a plane that has the same trim from start of flighht to end of flight.
Problem is, in the SPA/BPA airplanes, space may be at a premium.

RE: Fuel Fed Problem
 

I've actually used a 2oz 'hopper' tank on a ST2300 set-up just behind the firewall. The main 16oz tank was mounted over the airplane CG and the engine ran great without a pump! If you can squeeze even a 1oz tank in I think you may solve your problem as others have stated.
Good luck and keep us posted!
-Will

RE: Fuel Fed Problem
 

-


How about replacing the carb with a front needle valve type? If things persist as they are, that is.

Is it possible that your fuel pick up line in the tank is too stiff and isn't tracking along with your fuel? I can see your engine richening up when going inverted with the carb/spray bar above the centerline of the tank, but it should be going rich when inverted or in an outside loop - not dying lean. I say dying lean because if the engine was rich, it would not come back on without spitting and sputtering. Your description made me think it was losing its fuel and going lean.

You shouldn't need a pump unless something is wrong, like a backplate leak, etc. Even then you don't need a pump, just a gasket and retightening.

I never could get my Perry pumps to idle and transition well. but I was using 5% nitro fuel. Using 15% nitro or more, all of that becomes less critical. Plus, I found out later, I was melting the diaphragms over time by using 3-in-1 oil as after run oil. But even after replacing the pumps with undamaged ones and not using 3-in-1 oil any longer, they still did not give me the clean performance that I was looking for on a consistent basis.

I hate rear needle valves on front carbureted two-stroke engines. I wonder if the .55AX carb would fit? At least you would get better fuel draw. This is an unproven assumption.


Ed Cregger

RE: Fuel Fed Problem
 

Hallo Crankpin,

Look at Top Flite Taurus treath message of 14 12 07, My Taurus, with pressure regulator like Cline (Kline?).
I built these regulators myself but the are the same like Cline.

When these regulator works well, the engine thinks that the tank is on the place where the regulator is mounted. and this eliminates most of the problems.
You do need enough tank pressure to get the fuel in the motor in every position, so alo vertical up. Exhaust pressure of the 61FX will be enough.

Still another problem you solve with the system, when a 61FX does not get enough fuel, the motor gets warm. This also haats up the needle assy. and the fuel evaporates.
Most people think there is air in the fuel line between the needle and card, buts it's vapor. This blocks the fual and the motor really will be overheated. That why I did mount a Moki enlarged carb with needle in the carb.

With this system also idle vertical down works well.

I mount these regulators direct near the caburator on every two stroke.

Succes, Taurus Flyer

RE: Fuel Fed Problem
 

Taurus - Never thought of that, the vapor issue. With the needle valve assembly, (NVA), mounted in the back, will more heat be created there to identify what you said, vs the NVA out front more in the airstream?

This OS61FX, I can adjust it so a little on the rich side, and hold plane up, leans out well. Reason for this, normal NV running adjustment on the ground, this engine still screams when in the air. "Unloads", so they say. Come in, great. Only time I had problems is when using Cool Power fuel. Nasty stuff, nothing but varnish to show on the engine. Using Omega 15%, runs fine.

Thanks for info,
Vince

RE: Fuel Fed Problem
 

Crankpin,

The heat of the crankcase is conducted to the needle assy because the are mechanically connected. Methanol boils at 64,5 gr. C (147 gr. F)!!
A needle assy in front of the motor is cooled down by the evaporation of the methanol!!!



Taurus Flyer

RE: Fuel Fed Problem
 

Full Scale Aerobatic aircraft use a "Header Tank", that principal makes sense to me. I will probably try that one on some future projects. Thanks for the tip!!

I'm intrigued by the cline regulators. I did a little research on them and the the Perry pump system. I had just about talked myself out of the Perry system but thought I may like to try a cline or Ironbay regulator if the need ever arose. I remember reading you need a relatively large throat carburetor for the cline regulator system to work correctly as suction is required to draw the fuel from the regulator. If I'm remembering correctly the cline set-up pressurizes the tank which in turn forces fuel to the regulator. The regulator stops the fuel and holds the it there for the carburetor to draw on an "as needed" basis. It sounds pretty interesting.

I've actually ordered the Webra regulator for my Speed .61 which I have slated for my Curare. The Webra regulator seems allot like the cline or Ironbay regulators. It will be a while before I get to that project but I'm looking forward to checking it out.

I hope you find a resolution to your situation be it an adjustment, header tank or a regulator.

RE: Fuel Fed Problem
 

Atlanta 60,

Classic pattern planes does not have much room for a header tank, even the ventilation of the crankcase is poor, that is why I do not use back mounted needle assy directly on the motor. OS 61 FX, to avoid overheating and prevent ballbearing troubles.
A Cline regulator works with some underpressure, so suction has to draw the fuel, that is right
It's also right that the Cline need some pressure on the tank, at least as much to get the fuel near the regulator in any position of the plane.
I think the reason is that the Cline will drop no fuel when the motor is stopped, and that's a pro. In my regulators I adjust the needed underpressure as low as possible so I can enlarge the bore of the carb.



Taurus Flyer

RE: Fuel Fed Problem
 

You don't need a header tank on a classic pattern plane. We used to fly without them back then and never had any kind of a problem with fuel feed.

Modern patternships with wide fuselages and large diameter/low pitch props might have a problem, but the old classic pattern planes did not have the drag in the downlines that the new patternships have, so they moved along at a good clip, permitting the fuel to stay in the back of the tank.

Ed Cregger

RE: Fuel Fed Problem
 

Ed, that's right on the old ships. But, the issue here is the rear NVA. The old days, Super Tigres, OS, etc., all the NVA's up front, unless you had a RV or RR engine. Then with the carbs in the back, I never saw one run right. Jimmy Grier flew the RV Super Tigre's a lot, and I always remember him and Dave B. working on it. He also had the engines inverted. When they were running right, looked good.

Vince

RE: Fuel Fed Problem
 

Yes Vince,

It is just that Ed did not read my nickname, Taurus Flyer, so there are more, Merco 61 double plugged, Webra Speed, HB 61 and so on.
I did make my first fuel regulators when you where looking to the others asking yourselfes "Why do they wind-up there engines, that are fuel engines or not?" And a lot of pilots still do!
I could not wait for Cline, so my regulators are older and a little different.
The OS Max 61 FX.
A lot of metal on the cilinder and exhaust, more than the motors of our old ships (did you use an exhaust? I do not see this on the old Tauruses) heating up untill 200 gr C head temp, because vapor blocks the fuel and leans the motor, then it stops.
All the heat lets risen the temp of the crankcase and the big ball bearing displaces backwarts.
Away all your axial bearing play when the motor is cooling down, and now its the motor do the job.
Next you start he will destroy the ballbearings for you.
Yes Ed, they where running right and allways a little "rich"! (read expensive and with less power than max) our "ringed"!
Two pictures: one of the head temp warning light > 200 gr C, with memory, second the pressure regulator and you can see the Thermocouple connection at the head of the motor and also the checkvalve in the exthaust connection to the tank to get the right pressure on the tank.
Cees