OS 120 AX Special
07-26-2012, 06:31 AM
#26
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RE: OS 120 AX Special
the ax 120 special has extended crank timing, which was intended to push rpm range upwards, the tech notes also recommend the higher flow muffler as well
NOTES FROM OUR TECH DEPARTMENT
This is the 120AX Special Ringed Aircraft Engine from O.S. Engines.
FEATURES: High performance two stroke engine designed for sport and scale models Compact size enables it to fit into most cowls Crankshaft port timing was modified to increase power at high RPM Velocity stack on carburetor adds acceleration at high RPM 0.1mm head gasket increases compression ratio for more power 1mm deeper machining to enlarge intake port for greater RPM Two year limited warranty through Hobby Services beginning at date of purchase
NOTES FROM OUR TECH DEPARTMENT
This is the 120AX Special Ringed Aircraft Engine from O.S. Engines.
FEATURES: High performance two stroke engine designed for sport and scale models Compact size enables it to fit into most cowls Crankshaft port timing was modified to increase power at high RPM Velocity stack on carburetor adds acceleration at high RPM 0.1mm head gasket increases compression ratio for more power 1mm deeper machining to enlarge intake port for greater RPM Two year limited warranty through Hobby Services beginning at date of purchase
INCLUDES: 120AX Special Ringed Aircraft Engine, #8 Glow Plug, 70D Carburetor with Velocity Stack, Instruction Manual, Prop Washer & Nut and Needle Valve Extension Set
REQUIRES: Fuel: Two-Stroke with 18% lubricant and 5-20% nitromethane Muffler: E-5020 "Power Box" Propeller: 15x10-12 or 16x8-10
NOTES FROM OUR TECH DEPARTMENT
This is the 120AX Special Ringed Aircraft Engine from O.S. Engines.
FEATURES: High performance two stroke engine designed for sport and scale models Compact size enables it to fit into most cowls Crankshaft port timing was modified to increase power at high RPM Velocity stack on carburetor adds acceleration at high RPM 0.1mm head gasket increases compression ratio for more power 1mm deeper machining to enlarge intake port for greater RPM Two year limited warranty through Hobby Services beginning at date of purchase
NOTES FROM OUR TECH DEPARTMENT
This is the 120AX Special Ringed Aircraft Engine from O.S. Engines.
FEATURES: High performance two stroke engine designed for sport and scale models Compact size enables it to fit into most cowls Crankshaft port timing was modified to increase power at high RPM Velocity stack on carburetor adds acceleration at high RPM 0.1mm head gasket increases compression ratio for more power 1mm deeper machining to enlarge intake port for greater RPM Two year limited warranty through Hobby Services beginning at date of purchase
INCLUDES: 120AX Special Ringed Aircraft Engine, #8 Glow Plug, 70D Carburetor with Velocity Stack, Instruction Manual, Prop Washer & Nut and Needle Valve Extension Set
REQUIRES: Fuel: Two-Stroke with 18% lubricant and 5-20% nitromethane Muffler: E-5020 "Power Box" Propeller: 15x10-12 or 16x8-10
07-26-2012, 07:41 AM
#27
My Feedback: (66)
RE: OS 120 AX Special
ORIGINAL: lfinney
the ax 120 special has extended crank timing, which was intended to push rpm range upwards, the tech notes also recommend the higher flow muffler as well
NOTES FROM OUR TECH DEPARTMENT
This is the 120AX Special Ringed Aircraft Engine from O.S. Engines.
FEATURES: High performance two stroke engine designed for sport and scale models Compact size enables it to fit into most cowls Crankshaft port timing was modified to increase power at high RPM Velocity stack on carburetor adds acceleration at high RPM 0.1mm head gasket increases compression ratio for more power 1mm deeper machining to enlarge intake port for greater RPM Two year limited warranty through Hobby Services beginning at date of purchase
NOTES FROM OUR TECH DEPARTMENT
This is the 120AX Special Ringed Aircraft Engine from O.S. Engines.
FEATURES: High performance two stroke engine designed for sport and scale models Compact size enables it to fit into most cowls Crankshaft port timing was modified to increase power at high RPM Velocity stack on carburetor adds acceleration at high RPM 0.1mm head gasket increases compression ratio for more power 1mm deeper machining to enlarge intake port for greater RPM Two year limited warranty through Hobby Services beginning at date of purchase
INCLUDES: 120AX Special Ringed Aircraft Engine, #8 Glow Plug, 70D Carburetor with Velocity Stack, Instruction Manual, Prop Washer & Nut and Needle Valve Extension Set
REQUIRES: Fuel: Two-Stroke with 18% lubricant and 5-20% nitromethane Muffler: E-5020 ''Power Box'' Propeller: 15x10-12 or 16x8-10
the ax 120 special has extended crank timing, which was intended to push rpm range upwards, the tech notes also recommend the higher flow muffler as well
NOTES FROM OUR TECH DEPARTMENT
This is the 120AX Special Ringed Aircraft Engine from O.S. Engines.
FEATURES: High performance two stroke engine designed for sport and scale models Compact size enables it to fit into most cowls Crankshaft port timing was modified to increase power at high RPM Velocity stack on carburetor adds acceleration at high RPM 0.1mm head gasket increases compression ratio for more power 1mm deeper machining to enlarge intake port for greater RPM Two year limited warranty through Hobby Services beginning at date of purchase
NOTES FROM OUR TECH DEPARTMENT
This is the 120AX Special Ringed Aircraft Engine from O.S. Engines.
FEATURES: High performance two stroke engine designed for sport and scale models Compact size enables it to fit into most cowls Crankshaft port timing was modified to increase power at high RPM Velocity stack on carburetor adds acceleration at high RPM 0.1mm head gasket increases compression ratio for more power 1mm deeper machining to enlarge intake port for greater RPM Two year limited warranty through Hobby Services beginning at date of purchase
INCLUDES: 120AX Special Ringed Aircraft Engine, #8 Glow Plug, 70D Carburetor with Velocity Stack, Instruction Manual, Prop Washer & Nut and Needle Valve Extension Set
REQUIRES: Fuel: Two-Stroke with 18% lubricant and 5-20% nitromethane Muffler: E-5020 ''Power Box'' Propeller: 15x10-12 or 16x8-10
What are you trying to say here everyone know this. Also this special is only 300 more over the stock 120AX.
Ifinney have you owned a OS 120AX or 120AX S???????
07-27-2012, 06:27 PM
#28
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RE: OS 120 AX Special
My 120 AX Special is behaving better, but this is certainly a different engine. Today, I went to the field with a 16x10 prop and no cowl. Engine started immediately, checked the needle setting, seemed rich enough, rpm was 8250. Engine stopped after 7 min of flight. This has been a recurring issue. After cooling and refueling, started the engine and richened needle to 8040 rpm. Flew 2 flights at this setting and was rewarded with 2 landings under power. That's the good news. The bad news is that at that power setting, the engine is not much better than a well worn stock 120. This is a rich power setting. The unburned fuel trail was very prominent. I assume the thinner head gasket is a major contributor to the overheating problems of this engine. Also seems to me, OS should treat this as a different engine and publish an addendum to their manual. The engine has 28 flights and a lot of ground run time... about 2 gal fuel, maybe more. Unless it gets significantly better with more running, I don't suppose I'll get more performance until fall or maybe winter. I might be underestimating the mount of break in required and the effect of operating in 100 degree temps, but so far it is falling way short on my expectations.
John
John
07-27-2012, 07:13 PM
#29
RE: OS 120 AX Special
I think I would expect to run the same prop as the regular 120AX, with a bit better throttle response and top end. I'd personally stick with a 16x8 or 15x10. I ran the regular 120AX on a 16x8 in the Venus and really liked it, then I propped down to a 16x6 and ran it in my Yak. The increased RPM with the 16x6 gave it more of a "4-stroke feel" with the quick throttle response, and top end was still pretty good with the increased revs. My expectation of the 120AX special would be a similar gain but without propping down.
The 16x8 was nice - it had good pull, seemed to be a good blend of power and low noise, but the throttle response felt a touch mushy; it needed some time to make RPM prior to a pull. I liked the YS due to the immediate throttle response. The OS felt more like that with the 16x6.
15x10 was a little too slow to rev up. I liked the performance some of the time, but too often it didn't have the pull I wanted. I think the special might handle it nicely.
The 16x8 was nice - it had good pull, seemed to be a good blend of power and low noise, but the throttle response felt a touch mushy; it needed some time to make RPM prior to a pull. I liked the YS due to the immediate throttle response. The OS felt more like that with the 16x6.
15x10 was a little too slow to rev up. I liked the performance some of the time, but too often it didn't have the pull I wanted. I think the special might handle it nicely.
