OS 50 SX problem
08-01-2003 | 04:02 AM
#1
Thread Starter
My Feedback: (72)
OS 50 SX problem
Just bought a used one in excellent condition with very little time on it. (I know, thats what they all say)
I've got 3 flights on it in my World T-34, it idles great and transition is good but immediately after take off the engine surges for about 10 seconds (badly) but then clears out.
A magazine article mentioned the remote needle sucking air in a review but made no mention of the fix... What do I do about this?
Turning a APC 10/7 for now.
I've got 3 flights on it in my World T-34, it idles great and transition is good but immediately after take off the engine surges for about 10 seconds (badly) but then clears out.
A magazine article mentioned the remote needle sucking air in a review but made no mention of the fix... What do I do about this?
Turning a APC 10/7 for now.
08-01-2003 | 05:47 AM
#2
Senior Member
OS 50SX
Carlos,
I know the WM T-34 is used for racing in some circles. But having a thick, high lift symmetrical wing, it is built more for great maneuverability and for slower flight. It lands, under power, as slowly as most trainers.
My T-34 (with an OS.46FX) flies much better with a Bolly 11.5x6 and even with a Master Airscrew 11x6, it flew better than with a 10x7.
I suggest you change to an APC 11x6. It will load your engine more, but vertical performance will be improved visibly.
Your muffler equipped .50 (the engine is not rated by the manufacturer with the muffler...) is probably exceeding its RPM of maximal power, with the 10x7 prop you now have. Maybe this is the reason for the surge.
Is your fuel tank completely insulated from airframe vibrations, by a 1/4" layer of latex foam? Maybe vibration levels increase as the prop unloads in flight, causing the fuel to foam, or the clunk to take flight.
About your needle; if and only if you see bubbles in the fuel line between your needle and your carburettor, that are absent in the fuel line between the tank and the needle, is there a problem to be rectified. Check at all RPM levels.
The best fix, if this condition occurs, is to replace the O-ring that surrounds the needle.
Don't bother to find an OEM part. Any neoprene, or silicone O-ring, of the correct size will do.
If there is a leak in a fuel nipple, within the remote needle unit, exercise your warranty and replace the remote needle unit.
I know the WM T-34 is used for racing in some circles. But having a thick, high lift symmetrical wing, it is built more for great maneuverability and for slower flight. It lands, under power, as slowly as most trainers.
My T-34 (with an OS.46FX) flies much better with a Bolly 11.5x6 and even with a Master Airscrew 11x6, it flew better than with a 10x7.
I suggest you change to an APC 11x6. It will load your engine more, but vertical performance will be improved visibly.
Your muffler equipped .50 (the engine is not rated by the manufacturer with the muffler...) is probably exceeding its RPM of maximal power, with the 10x7 prop you now have. Maybe this is the reason for the surge.
Is your fuel tank completely insulated from airframe vibrations, by a 1/4" layer of latex foam? Maybe vibration levels increase as the prop unloads in flight, causing the fuel to foam, or the clunk to take flight.
About your needle; if and only if you see bubbles in the fuel line between your needle and your carburettor, that are absent in the fuel line between the tank and the needle, is there a problem to be rectified. Check at all RPM levels.
The best fix, if this condition occurs, is to replace the O-ring that surrounds the needle.
Don't bother to find an OEM part. Any neoprene, or silicone O-ring, of the correct size will do.
If there is a leak in a fuel nipple, within the remote needle unit, exercise your warranty and replace the remote needle unit.
08-01-2003 | 03:46 PM
#3
Thread Starter
My Feedback: (72)
OS 50
Hi Dar,
I'll try a APC 11/6 and at a richer setting.
I've removed the muffler baffle and drilled out the exhaust outlet pipe to the max, I use mostly Powermaster 15% fuel.
This is the fifth T-34 for me, sold two and crashed two and all with the OS 46 FX engines with the same mods (as per race rules).
Thanks,
Carlos
I'll try a APC 11/6 and at a richer setting.
I've removed the muffler baffle and drilled out the exhaust outlet pipe to the max, I use mostly Powermaster 15% fuel.
This is the fifth T-34 for me, sold two and crashed two and all with the OS 46 FX engines with the same mods (as per race rules).
Thanks,
Carlos
08-02-2003 | 08:24 AM
#4
Senior Member
Race...
Carlos,
So you do race the T-34.
If so, the correct load for the engine would be a 10x8, or a 10.5x8 (better), so you can get a speed advantage from the higher prop pitch. Even a 10.5x7 is preferable to the 10x7.
The 10.5 diameter will improve your thrust by over a pound, compared with the 10x7 you now use, despite the RPM reduction.
You will have to obtain a small stock of Bolly props, because APC doesn't have these sizes. See this web site for North America:
http://www.bollyprops.com/index.html
My T-34 is my first and has been flying with a minor mishap, or two, but no major crashes (thankfully), for nearly 3 years.
So you do race the T-34.
If so, the correct load for the engine would be a 10x8, or a 10.5x8 (better), so you can get a speed advantage from the higher prop pitch. Even a 10.5x7 is preferable to the 10x7.
The 10.5 diameter will improve your thrust by over a pound, compared with the 10x7 you now use, despite the RPM reduction.
You will have to obtain a small stock of Bolly props, because APC doesn't have these sizes. See this web site for North America:
http://www.bollyprops.com/index.html
My T-34 is my first and has been flying with a minor mishap, or two, but no major crashes (thankfully), for nearly 3 years.
