i'm planing to use os 120 engine on a new model and want to use a big fuel tank in order to get a long flight time (about 1000 cc). I read in the past that there is a limited size for the tank, and you cant use a big size tank. in the manual of the engine the recomended size is about 350cc. is it a problem to use bigger tank? and if yes is there a way to do it? dan
I have a Telemaster with an OS 1.08 and a 1000cc tank. No problems whatsoever. The Telemaster can carry a lot of payload and is not very sensitive to CG location, so the weight is not a problem either.
If I fly a lot at full power, such as when lifting gliders, I get about half an hour on a tankful.
On Tue, 21 Oct 2008 07:49:17 -0700 (PDT), dan wrote in :
In my view, the best thing to do is to just try the tank size you want and see what happens.
The issue is probably fuel draw.
You will also have a very large shift of CG as you drain the tank if you locate it off the CG of the plane. If the tank is forward, the plane will be nose-heavy at takeoff less so when the tank is empty.
You can get various pumps or fuel regulators to help with the draw. I've heard good things about Perry pumps and Kline regulators but haven't used either myself.
Another potential problem: inconsistency during the run. The big tank may produce extra pressure when full. I usually try to get the centerline of my tanks at or just below the position of the spraybar in the carb. With an oversize tank, you may have to run overly rich at first in order not to run too lean later in the flight.
My guess is that you can probably solve all these problems ...
Good luck with your project. Let us know how it turns out.
Marty
---------------
As Marty has indicated, the fuel pressure head will vary during your flight and change your mixture as the engine consumes the fuel. This is not good because as the fuel is burned off, the fuel to air ratio seen by your engine becomes leaner and leaner.
There are three solutions to this problem.
The first is to buy an engine with a pressurized fuel system installed by the factory, such as a YS or an OS FS-120 Surpass III/Pump.
The second solution is to buy a third party pump/regulator such as the Perry system. The Perry system is a pump that relies upon crankcase impulse pressure gained from the engine's lower crankcase area (two-stroke). This can also be made to work with a four-stroke if you look for the information here on RCU.
The third option is to go with a Cline Regulator. The Cline Regulator requires that the tank be pressurized over atmospheric level. This is easily accomplished by running a pressure line from the muffler to the fuel tank vent line. This choice is my favorite of the three. It is the simplest. It is effective. It is relatively inexpensive to accomplish ($60 USD, plus shipping) and it works with no known disadvantages when compared to the other two methods.
With all three of the choices listed above, it is feasible to mount the fuel tank near the balance point of the model (CG), so as not to suffer a severe trim change as the fuel burns off. Good luck.
Ed Cregger
"Ed Cregger" wrote in message news:1VmMk.50792$ snipped-for-privacy@bignews5.bellsouth.net... | | "Martin X. Moleski, SJ" wrote in message | news:Jdedna3LoNTzmGPVnZ2dnUVZ snipped-for-privacy@supernews.com... | > On Tue, 21 Oct 2008 07:49:17 -0700 (PDT), dan wrote | > in | > : | >
| >>i'm planing to use os 120 engine on a new model and want to use a big | >>fuel tank in order to get a long flight time (about 1000 cc). | >>I read in the past that there is a limited size for the tank, and you | >>cant use a big size tank. | >>in the manual of the engine the recomended size is about 350cc. | >>is it a problem to use bigger tank? | >>and if yes is there a way to do it? | >
| > In my view, the best thing to do is to just try | > the tank size you want and see what happens. | >
| > The issue is probably fuel draw. | >
| > You will also have a very large shift of CG | > as you drain the tank if you locate it off | > the CG of the plane. If the tank is forward, | > the plane will be nose-heavy at takeoff less | > so when the tank is empty. | >
| > You can get various pumps or fuel regulators | > to help with the draw. I've heard good things | > about Perry pumps and Kline regulators but | > haven't used either myself. | >
| > Another potential problem: inconsistency during | > the run. The big tank may produce extra pressure | > when full. I usually try to get the centerline | > of my tanks at or just below the position of the | > spraybar in the carb. With an oversize tank, | > you may have to run overly rich at first in order | > not to run too lean later in the flight. | >
| > My guess is that you can probably solve all these | > problems ... | >
| > Good luck with your project. Let us know how it | > turns out. | >
| > Marty | | --------------- | | As Marty has indicated, the fuel pressure head will vary during your flight | and change your mixture as the engine consumes the fuel. This is not good | because as the fuel is burned off, the fuel to air ratio seen by your engine | becomes leaner and leaner. | | There are three solutions to this problem. | | The first is to buy an engine with a pressurized fuel system installed by | the factory, such as a YS or an OS FS-120 Surpass III/Pump. | | The second solution is to buy a third party pump/regulator such as the Perry | system. The Perry system is a pump that relies upon crankcase impulse | pressure gained from the engine's lower crankcase area (two-stroke). This | can also be made to work with a four-stroke if you look for the information | here on RCU. | | The third option is to go with a Cline Regulator. The Cline Regulator | requires that the tank be pressurized over atmospheric level. This is easily | accomplished by running a pressure line from the muffler to the fuel tank | vent line. This choice is my favorite of the three. It is the simplest. It | is effective. It is relatively inexpensive to accomplish ($60 USD, plus | shipping) and it works with no known disadvantages when compared to the | other two methods. | | With all three of the choices listed above, it is feasible to mount the fuel | tank near the balance point of the model (CG), so as not to suffer a severe | trim change as the fuel burns off. Good luck. | | Ed Cregger
Excuse me for breaking in here but there are more options. Varsane (Perry) makes a vibration operated pump that they recommend for 4 strokes. Here is a Saito link that covers the options for their engines which would apply for other non pumped engines as well.
a3LoNTzmGPVnZ2dnUVZ snipped-for-privacy@supernews.com...
eTnx for the information about the cline regulator..... i'm going to use a 2 cycle engine, from the article i read in the internet in 2 cycle engines the pressure comes from the cranck case, that to my understanding means to drill a hole in the engins case. can i connect the pressure to the mufller's regular pressure conection? while using the cline reg with 2 cycle engine? Tnx
On Fri, 24 Oct 2008 16:31:49 -0700 (PDT), dan wrote in :
The Cline system requires no drilling.
All of the contemporary 2-cycle designs get pressure from the muffler-tap. I haven't heard of any tapless muffler in years and years.
The Cline system gets pressure from the muffler tap and keeps the pressure high in the tank by the use of a check valve (that may be the weak link in the Cline system). Then the regulator is placed in the fuel line near the needle valve (within 1" or so, if I remember correctly). When the regulator "feels" suction from the fuel line, it lets a dose of fuel through; when the suction stops, so does the flow of fuel.
Some of the pumps do get pressure from drilling holes in the crankcase. Those are different from the Cline system.
It sounds as though you haven't done any RC yet. You might want to go with a smaller, simpler rig until you get up to speed on how things work.
Marty
Tnx for the information after reading in the internet about the Cline Regulator iunderstood that using it with 2 cycle engines means to get pressure from the cranck case. is it correct? can i use the regukar pressure from the muffler??
On Fri, 24 Oct 2008 20:55:31 -0700 (PDT), dan wrote in :
According to the Cline website, they recommend crankcase pressure for 2-cycles and muffler pressure for 4-cycles:
:
installed
impulse
Regulator
engines
well.http://saito-engines.info/pumps.html>
Tnx for the information after reading in the internet about the Cline Regulator iunderstood that using it with 2 cycle engines means to get pressure from the cranck case. is it correct? can i use the regukar pressure from the muffler??
You pressure your tank with crankcase pressure when using it on a 2 cycle engine and you must use exhaust pressure when you use it on a 4 cycle engine. The Cline is a REGULATOR. It is not a pump. It uses a check valve to hold pressure in the tank and then it regulates a constant pressure to the engines needle valve.
Did you follow the link to Cline?
A minus for the Cline system is that the system is pressurized at least
2lb/sq in which requires very secure fuel line connections. Some of the guys I knew that were using the system wrapped their tanks with nylon stranded packing tape to control tank expansion.All of the above is why I decided to use the Perry pump system. It will draw fuel up to 9 inches away from the pump using crankcase pressure only. While I haven't tried it, others have used exhaust pressure in conjunction with the pump for greater pump to tank distances.
On Sat, 25 Oct 2008 08:34:54 -0500, "Anyolmouse" wrote in :
I think the pattern guys often do that when setting up YS systems, too.
The trouble with expansion is that a tank can split along the seams after it's gone through enough cycles.
Marty
Tnx for all the answers and to marty, I'm an expirienced rc builder and flyer, but still things that i don't know i prefer to ask, and ask again, instead of doing things wrang dani
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