Hi Guys, I have looked long and hard through the 3D threads on the pros and cons of running Saito 125,s and YS110,s and decided to go for an OS 120 AX in my new Seagull Harrier 90 3D model.
Is ther anyone else here running an OS120AX in their 3D model,any tips on prop sizes etc.

I am goint to start with 25%coolpower and an APC 16X6.The Target AUW of my Harrier will be 8.5lbs.
Any imput or advice would be most welcome.
Thanks ,Mark Palmer

Use 15% cool power and a light wood prop (Skorepa or similar) 16x6 or 17x6 for fast spool. If you are going to do extended hover practice and want optimal performance I recommend a pump or regulated fuel system (though have no experience with the AX120 with fuel system).
The motor should pull a solid 15 pounds of thrust close to sea level--if you come in @ 8.5 pounds and are not too high you should be good.

I have been on the fence about trying one of these, I have the OS108 and OS160 and they 3D great.

Mark,
I have been running an OS 120AX on an OMP Katana 70 V2. It has terrific power, of course. But what I like best is the smooth consistent transition. I just competed a scratch built of my own design for this engine. Its a profile with 1000 aq in of wing and weighs just over 6 lbs. It should be a rocket. I run a 17-6 APC and it turns it great. The light wood props mentioned above would be better. I found I instantly trusted this engine down on the deck, which is what is needed for 3D. As you break in the motor, take care to be sure the low end isn't too rich. Many problems with transition in 2 strokes come from this. I think you'll find this is a great running motor and a smart 3D investment.
Regards,
Dave

hi Guys, Thanks for the imput.
I am 850ft above sea level so I think i am in with a chance. I go for low level hovering ,harrier 8,s etc over blenders and other altitude moves. I am running a ucando 46 with a West t50 and pipe,and also a balsa craft extreme light,OS46FX and Cvec pipe.
I totally rely on an instantaneous spool up so I have skirted the pistons and gas flowed my 2 46 size motors to give me the confidence.
Hovever this is my first step into larger 3D models and also the 120AX is ringed so dont think it will take any severe mods without throwing the piston through the side of the liner ports.
I will probably break in on the apc 16X6 then track down the lighter loading wooden props you both have suggested.
Thanks,mark

Absolutely the same way I,m going. After owning several 4 strokes,went back to using a larger than called for 2 strokes,they 3-D just fine,cheaper fuels,engine and repair costs(I replace parts in my 2 strokes).And the newer, lighter OS 120(near same weight as the older 1.08)should be perfect.

I just test flew the scratch built I mentioned above with the 120AX. What a motor. The transition truly is great. and power is incredible! BTW, the airplane flew great, too! I was so comfortable with the motor (and plane) on the second flight I was doing rollers down low!

Hi dave,I am pleased that the OS is doing the business for you.The feedback on the 120AX seems to be good by all.
I am now on the hunt for a mini pipe. any suggestions?
I did track down a candidate from Morris Hobbies. They make an adaptor from an OS 91FX square to a Rossi round "O" ring manifold stump,then fit the Rossi 65 Mini pipe. I will have to cross ref the dimentions of the 91FX stub bolt and case outlet dimentions.
Regards,Mark

Hey Guys! I'm waiting for my Harrier 90. I am high Elevation: 6184' (1885m). I also want a 2 stroke engine for econimical reasons. I've been thinking about the 120AX. But i really don't know if it will work well hovers and everything. This is my first 3D. I'm jumping from a Super Stick, and a Mustang PTS Trainer. Both OS .46FX. Could you send me your thoughts about an OS 120AX in a Harrier 90 at 6,200 ft elevation? What Prop? Or maybe going all the way with an OS 160??? Also what prop? And last but not least...break in suggestions. Thanks in advance!

Hi, I have a Harrier 90 with an OS 120AX in it. all up weight 8.2lbs
It is turning an APC 16X6 @ 9100 rpm.This gives 16lbs of thrust at my altitude 850 Ft above sea level,air dencity Hg: 30.06.
I am running the motor on Magnum 20% Heli mix and a Medium rated plug. The motor is awesome hover on less than half throttle and plenty of punch out.
The O.S 160 does have more torque and power but the extra weight of the motor over does the wing loading of the Harrier,so 3D floaty manouveres are no go.

I hope this helps, Regards,Mark

I have a 120AX on my Seagull Edge 540. The engine is great. I was wondering if going to a 16x4W would be a problem. Right now I have a 16x8 and I have trouble slowing it down. I have a 4W and was wondering if you guys thought it would be a problem to run this prop on it. Thanks for the help.
Eric

I think the 16x4W would be a bit small. I'm currently using a 16x6 and the 120AX is turning 9,600, which I believe is about 600 rpm over peak power. You would get even more rpm out of a 16x4W, I think. If I could fit a 17x6 prop in the spinner I'm using, 2.5", I would go with that size prop.

Malcolm

Do you think the 120AX will power CA Epsilon 120 for pattern?

I already balanced the 16x4W, so I can't take it back. I will give it a try and see what it turns. OS' website says practical RPM is 9500.

What do you guys think about this engine on the new Funtana X100?

I think it would work well, it's what I'm thinking of doing.

I'm just not sure what prop, the 16x4 is too small, so I figure the 17x6...?

Has anybody run the 16x4W on the 120AX? People say it is too small, but I don't know of anybody who has tried it yet. I have it on mine right now, but I havn't had a chance to fly it yet.

OS advertises that it can use a 16x8-10, so a 16x4 would probably be too small, but I figure the next step up would be a 17x6...

guys,
I'm using the APC 17-6 on mine. The engine has no problem turning this prop. Sorry I don't know what its turning, but I know its happy.

So your 100X flys well with the 1.20AX and 17X6 prop Aero Dave?

Mine was turning just under 9,000 on an APC 17X6 buring Powermaster YS20/20 yielding about 13 lb thrust static. stock muffler and no pump. I've dropped down to 16X8 and added a VP30 pump but haven't checked the rpms. Performance seems good for pattern style flying on a 9.5lb UltraRC Quest 2G. I might try a lighter 17X6; Throttle transition seems a tad slow going up and down.

I don't have a 100X. Just stating the motor runs well with that prop.

Will this engine go well on my new ucando 60 or is better os91fx (less power)? If i buy 120ax i can in future use it also into a funana.

What can you suggest to me?

Thanks

I had the 91 fx int eh UCD 60. Truly, plenty of power. Hover pullout was very strong. I think the 120 ax ould be overkill in this [lane, but if you want one engine to use now and for the funtana later it would work. Just be really careful with throttle management. NEVER use full throttle in level flight.

i will do a throttle curve with TX to manage right the engine. Of course full throttle only in desperate case
I will order it.

Good! I have a plane similar to the UCD in weight with that motor on it. i find I fly at very low throttle settings, blipping when needed. Even in vertical lines I'll back off after it reaches speed and coast. Funny thing, I use so little of the engines power it takes less fuel than my .46! Hover pullout is truly devistating. Its REALLY fun! And having that big prop out front gives me total control in harriers. stationary flips, etc.