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  1. #1
    flyer1966's Avatar
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    OS AX 46 needs more power

    How can I increase the power in my OS AX 46? We have club races with GP Vipers. We all use the same engine and airframe. The last race I had a guy flying about 15 mph faster then me in the straight away. I think he did something to his motor because it seized up in the last heat. What can I do to increase the power in my 46?

  2. #2
    soarrich's Avatar
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    RE: OS AX 46 needs more power

    Work on the prop, that's where you'll get your speed.
    Rich Border AMA 77727
    Sig Kadet Brotherhood #2

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    RE: OS AX 46 needs more power

    Tear the engine down and sonic clean it. Put all the parts in a jar of solvent and tape it to an orbital sander and run it for as long as you think it should take.
    Reinstall just the crankshaft in the case, prop drive washer/collet and prop and check this assembly for friction free movement. You should be able to just flick the prop to make it spin for a few seconds. When the prop comes to a stop, it gradually loses momentum. If the bearings have too much of a crush fit in the case it will cause the crank to drag. To relax the fit you need to open up the rear bearing journal in the case with some careful sanding. A miniscule difference in bearing crush will make a huge difference in power lost due to friction. The distance between the bearings can't be too great either..there should be a tiny amount of end play in the crankshaft just to be sure.
    Run the engine with a 8x6 prop on the bench for a few tanks at wide open throttle. Don't mess with the throttle, just run it wide open. Check the exhaust spray for residue by letting it blow against a white rag.
    Once the engine is properly broke in the prop snaps through compression with a nice pop and then toggles back and forth freely before stopping when you check it by hand.
    Make sure the engine is bolted to absolutely flat and true mounts.
    Stock class racing should be just that...stock everything. "Detailing" the fit of the crankshaft bends the spirit of rules, but you are just bringing the engine up to it's optimum blueprint specs.
    Make sure you play with head shims and prop combos. Higher compression needs less load and visa versa.
    If your friend is running the exact same prop as you and the same plane, same fuel, etc....15 mph difference [which is huge] could be a combination of your set up needing some work and possibly he opened up the ports and timing of his engine. Maybe there should be a requirement to idle and taxi the planes for x amount of time before and after the heat is run..?
    WHO GUNNA FEED MAW KEEEIDS..???

  4. #4
    flyer1966's Avatar
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    RE: OS AX 46 needs more power

    What prop do you recommend ?

  5. #5
    combatpigg's Avatar
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    RE: OS AX 46 needs more power

    IIRC we ran either 9x6 or 9x7 APCs in a very similar class years ago with Vipers and Predators.

    There might be better props out there in APC's competition series.
    I have found an edge with carbon fiber props from suppliers like Eliminator [Steve Wilk]

    APCs are relatively heavy and thick, so they require more power to turn VS well made carbon props. I can take a carbon prop and reduce blade area and see improvement sometimes.
    WHO GUNNA FEED MAW KEEEIDS..???

  6. #6
    flyer1966's Avatar
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    RE: OS AX 46 needs more power

    I will try tearing down the motor and smooth it up. My friend seized up his motor with whatever he did thanks for the info.

  7. #7
    combatpigg's Avatar
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    RE: OS AX 46 needs more power

    If your engine already passes the "finger flick" test...then don't bother tearing it down.
    Chances are good you could try running a quart through it with a 8x6 prop and that might loosen it up. Take some store bought fuel and add an ounce of either castor or Klotz oil per quart of fuel and you might find that the engine will tolerate more aggressive needle settings without heat issues. Adding oil can increase the engine's usable power.

    Edit....check the elevator trim on your plane on the bench. It should be zero-zero.
    All control surfaces should be zero-zero, for that matter. ARFs are known for being crooked, wrong incidences, etc. A perfectly straight plane with the lowest drag possible will allow your engine to unload to it's full potential.
    WHO GUNNA FEED MAW KEEEIDS..???

  8. #8
    flyer1966's Avatar
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    RE: OS AX 46 needs more power

    I've been running YS 20/20. Is that a bad thing?

  9. #9
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    RE: OS AX 46 needs more power

    20% nitro 20% oil..?
    That sounds great.
    The prop advice I gave you earlier was for .40s.. [my mistake]....your .45 size engines should make that plane faster with 9x7 to 9x8 props. APC also has fractional sizes in this range for competition.
    With 20% oil, you can get away with occasional settings that are too lean...but always be ready to shut it down when you hear it sag. Make sure your low speed mixture isn't too lean also.
    WHO GUNNA FEED MAW KEEEIDS..???

  10. #10
    flyer1966's Avatar
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    RE: OS AX 46 needs more power

    Yep I was running one of the APC race props. It was in the 8.8x 8 range I think.

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    RE: OS AX 46 needs more power

    If your are able to get the engine turning free with carefull detail to the lower end, then like Rich said finding the right prop is the key.
    APC competition series props are really good.
    Being 15 mph slower is mystifying, but take it as a hill to climb one step at a time.
    WHO GUNNA FEED MAW KEEEIDS..???

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    RE: OS AX 46 needs more power

    use a cold plug as well, this is key to getting all the power out of it, and check and seal all movable services, you can replace your bearings with aftermarket bearings with a ABEC7 rating its a much looser fit
    and is used by racers and nelson engines etc etc , they have polyamide bearing retainers or other low friction plastic..they are lighter than metal retainers as well. all os heli engine use plastic retainer bearings
    with your prop drive installed and a prop torqued down to test crank endplay it should be free and spin easily, i prefer to have some endplay with prop installed. os engines often have tight wristpins out of the box, i lap pin bore until there is free rotation as well, jett engines use .003-.004 big end clearance, os engines stock are very tight, i use kratex rubber abrasive small wheels to polish rod end bores to achieve
    this clearance.

  13. #13
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    RE: OS AX 46 needs more power

    What prop, plug are you running on it now?

    Can you post a photo of the installation also ?

    Keep in mind.. . Q-500 speed is not ALWAYS the engine. If you are actually racing, flying has a LOT to do with it.

    If you are just messing around comparing straight line speed... then need to work on the prop setup. The engine is what it is trick is finding the prop that makes that particular engine/airframe combination happy.
    Bob Brassell
    Jett Engineering - Engine Mfg Support Forum Host
    rjbrassell@gmail.com or bob27s@hotmail.com
    RB-78

  14. #14
    flyer1966's Avatar
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    RE: OS AX 46 needs more power

    I would post a picture but the last race I hit the pole and tore a big hole in the left wing and tore off my gear. I finished the race and actually won due to my friend blowing up. I have a new fuse and wing being delivered today. I'm going to build it lighter than my old one by using lighter servos and battery.

  15. #15
    flyer1966's Avatar
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    RE: OS AX 46 needs more power

    I'm using a OS #8 glow plug. Not sure what you mean by a cold plug?

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    RE: OS AX 46 needs more power

    If you are running a 8.8x8 Pylon prop then that is your problem. that prop need tos spin over 19,000 to really start working. On a Stock engine you will be better off with a 9x8-9x9 set up or a 8x10 if on a long course. do you have to run stock muffler? There are a million things you can do to get more power but need to know your rules?

    Like Dub said show us a pic of your plane.

    Ifinney the ABEC rating is determined from how much "noise" a bearing makes. Usually the lower the ABEC rating the looser the fit ie more noise or not so perfect bearings. I would say a ABEC 3 or 5 is best for RC engines. If a bearing company tries to sell you a ABEC 7 or 9 bearing then are taking you for a sucker lol. how will you know its a 3,5, 7 or 9 lol.
    AMA # 126183
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  17. #17
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    RE: OS AX 46 needs more power

    The rules are going to be a determining factor here. Seems like the rulse are pretty loose otherwise you would not be running 20/20. That engine makes it's power in the 16,000 to 17,000 range. If you are stuck with the stock muffler then remove the baffle and prop for 17,000. I would strat with the APC 9X7 sport. Enya #3 plugs work well with 20% nitro. If your plugs are lasting a long time on 20% nitro, you can bump up the compression some. If you are able to replace the muffler, go with a Jett or Nelson. Those mufflers work within a certain RPM. You will know when you hit the right RPM and it jumps on the pipe. OS bearings are not the greatest. If rules allow call Boca and order some stainless C3 bearings with phenolic retainers. Phenolic works better but if your bending the rules get steel retainers.


    IMO I don't think your pal did anything to his engine except prop it better or had his airplane set up better. When 90% of the guys out ther start grinding on an engine they actually do more harm then good. My race planes are set up so that they will do a roll in about a second and a half and a pylon turn uses almost full backstick. I have to switch to high rates to land. Overcontrolling can cost you a good second + per lap. With a 130 mph airplane on the long course that is a full lap give or take. Just yesterday we had a warbird race. It was 103 degrees out so it took a few heats to get props, plugs and needle settings figured out. My first heat was 2:09 on a 700 foot course. With the right combo and my caller being right on the money, my final heat was 1:53. Big difference. My Rossi .45 is much simular to the OS 46 in timing numbers. I was running an APC 9.5X7 pylon prop cut down to 9", 20/20 fuel, Glowbee plug and Nelson muffler.

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    flyer1966's Avatar
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    RE: OS AX 46 needs more power

    Not really sure about the rules. The Viper class at our club is a 46 class so called unlimited. The reason I say that is I originally had a Jett 46 on the Viper and was told after we had a practice race that I was too fast. I thought our planes were equal I was just turning on the pylon and my friend was flying long past the pylon. So now I had to put the OS AX on the plane but now I'm so much slower in the straight away. The only way I can stay ahead of the guy is to turn right on the pylon while he flies about 100 to 200 feet long. He then passes me about 3/4 the down the straight away. I just need a little more speed to give me a little more room around the pylon so I don't hit it again. I just found my new airframe on my door step from the UPS guy.

  19. #19
    flyer1966's Avatar
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    RE: OS AX 46 needs more power

    My prop I was running was a APC 8.8 x 9.25.

  20. #20
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    RE: OS AX 46 needs more power


    ORIGINAL: flyer1966

    My prop I was running was a APC 8.8 x 9.25.

    Way too much prop for that engine. I doubt you were getting more then 13,500 RPM. I broke my piped Rossi 61 in on a 8.75X8.75


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    RE: OS AX 46 needs more power

    ORIGINAL: flyer1966
    The Viper class at our club is a 46 class so called unlimited. The reason I say that is I originally had a Jett 46 on the Viper and was told after we had a practice race that I was too fast.
    Devil in the details! Ya, the Jett may upset a few LOL. I'm kinda wondering if you wouldn't be better off with a the older OS 46 FX, Thunder Tiger 46 or Evolution 46 NT. The 46AX is a lower turning engine I believe, and as Raptor eluded to, the pylon prop works best at high rpm so I'd stay with the APC sport props to take advantage of the greater torque of the AX, if you stay with it.

    If you can take out the baffle, that may gain you a tad. Most OS sport engines start to struggle with 20% nitro, unless you start messing with cooler plugs and/or extra head gasket. I'd run 15% Wildcat or Power Master and a #8 plug and call it good
    Oooh eee oooh ah ah(the crowd) ting tang walla walla bing bang!(the plane crash)

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    flyer1966's Avatar
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    RE: OS AX 46 needs more power

    10-4 on the 15% and #8 plug. My buddy was running the Thunder Tiger 46 until it seized. It didn't want to idle before the race. All of you guys have helped me out greatly. My motor seems to be pretty smooth on the flip test. What happens when you add a extra head gasket to the motor. I almost have my new Viper together with the use of some of my old parts. I'm gonna save alot of weight just by using micro MG servos out of my combat planes. My old Viper had Futaba 3004 servos in it and a large battery pack. I'm gonna run a 6v 600mah pack vs my 6v 2500 pack.

  23. #23
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    RE: OS AX 46 needs more power

    ORIGINAL: flyer1966

    What happens when you add a extra head gasket to the motor.
    You reduce the compression of the combustion chamber so it can handle better the high nitro content.
    Living on a War Zone !!!!!
    Seriously

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    RE: OS AX 46 needs more power

    flyer you need to ask what are the rules and they need to enforce them all. if that guy is flying past the pylon even by 100 feet each end and still passing you before the next turn he doesnt have a stock engine. Is this the same guy that told you that you couldnt run the Jett engine?

    just because a prop says "pylon" on it doesnt mean it should go on your plane and engine. These" 40 size pylon" props are very narrow compaired to the sport props. they need to spin over 19,000 to work well. Put one on a engine that can spin them that fast or faster and run the engine rich to stay below 17,000 then while holding the plane slowly lean the engine out. once it reaches 19,000 all of a sudden the thrust will almost double or so it feels. 21,000 and they are pulling very very good.

    "Pylon props" need to go on a "Pylon engine"............


    Find out if you can run a Jett muffler? Also find out if you can run a Supertiger 45???????
    AMA # 126183
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  25. #25

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    RE: OS AX 46 needs more power

    heres some real tech about ABEC, for those who really want to know facts versus old wives tales

    the most crude, the least precise, the most durable and the cheapest.
    ABEC 3 is what most cheap complete skateboards come with, especially skateboards from China. ABEC 3 bearings will work for most skateboarding, but won't roll very smoothly or fast.
    ABEC 5 bearings are the norm in skateboarding. You get a reasonable amount of speed, and at a reasonable cost. However, there are lots of people who argue that the skateboarding industry is lying, and that most ABEC 5 skateboard bearings you see aren't actually built to ABEC 5 standards...
    ABEC 7 bearings would be very fast and smooth, but very expensive. Plus, you start to run the risk of needlessly damaging them if you skate hard or aggressively. Also, if you are buying cheap ABEC 7 bearings made in China, you are probably being lied to (read The Truth about Skateboard Bearings.
    ABEC 9 and higher bearings would be ridiculous to use in a skateboard, unless you are doing downhill luge style skating, or something else where your goal is to go insanely fast. If you aren't spending a fortune on these bearings, then don't trust that they are in fact ABEC 9!

    The ABEC rating of a bearing is determined by asking these four questions:

    How close is the bore to 8mm in microns (a micron is one millionth of a meter)?
    How close is the outer diameter to 22 in microns?
    How close is the width to 7mm in microns?
    What's the rotating accuracy in microns?

    knowledge is power abec rating have nothing to do with noise as posted earlier in this thread


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