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  1. #26
    akouzmit's Avatar
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    RE: O.S. GF40 4st gas


    ORIGINAL: ozzieflyer


    ORIGINAL: MKnutson

    Iv'e got the DLE 35RA rear exhaust also, and it is no slouch in the power dept.
    Power to weight, the 4 strokes will never be as good as similar size 2 strokes for all out power.
    I wasn't going for sheer power it the choice of this engine, my dle 35 will spin the same prop a bit higher than the OS. I got this engine for the inherent quality of OS and for the 4 stroke sound.
    OH, and the ''sound'', my wallet is a touch thinner from this thing too! I like it enough to possibly get another one.
    I could really see this engine residing on the front of a H-9 1/4 PA-18 cuper cub! That would be another perfect combo.

    Mark.
    So, thinking of getting one of these for my 88 inch Tiger Moth.
    What do you think?
    Tiger Moth needs a 4 stroke, just for the sound.
    For 88" TigerM 30cc 4-stroke will be more than enough otherwise it will be a rocket with 40cc and doesn't fly scale :-).
    SAITO FG-30 will more suitable although I believe in 6 months OS will come with ~26cc -30cc size 4-stroke gas and after that with ~60cc twin based on the previous 26-30cc single one. This way SAITO went in the past.
    If you need now then go with Saito FG-30 (very good engine). If you want OS brand then wait for several months untill they will come with 26-30cc 4-stroke gas. This is the trend.
    For the reference Saito fg21 produce 5.5 kg thrust with well suited prop and right RPM.
    Saito-FG-30 shoul do even more. If you plane is in 6.5-7.5kg range then 5.5kg thrust is sufficient for scale flying.
    30cc 4-stoke gas will be more than enough for your TigerM.
    OS GF40 is a bit overkill.

  2. #27
    TonyBuilder's Avatar
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    RE: O.S. GF40 4st gas

    Has anyone used a 3-blade prop on the OS 40cc 4S? I want to put two of them in my 101" Ziroli B-25 the only prop I have seen is the bela 16x10- 3-blade.
    TB
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  3. #28

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    RE: O.S. GF40 4st gas

    I think the 40cc OS would fly the Tiger Moth just fine! Just put a big dia. flat pitch prop on it to fly slow.
    I don't think that the OS would be overkill, but it would be at the higher end for power. Locally a guy flew one, (Tiger Moth), with a Rotomotor 35cc 4 stroke and it was powered ok, but could have used more.
    I'm not into marginally powering my planes, that's what they make throttles for.

    Mark

  4. #29

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    RE: O.S. GF40 4st gas


    ORIGINAL: MKnutson

    I think the 40cc OS would fly the Tiger Moth just fine! Just put a big dia. flat pitch prop on it to fly slow.
    I don't think that the OS would be overkill, but it would be at the higher end for power. Locally a guy flew one, (Tiger Moth), with a Rotomotor 35cc 4 stroke and it was powered ok, but could have used more.
    I'm not into marginally powering my planes, that's what they make throttles for.

    Mark
    Thanks for imput guys.
    Pus the Tiger seems to need a bit of nose weight, so the slightly bigger engine will help.
    I have 92 inch Ryan STA, witht he OS GT33. Weigh overpowered, but big dia small pitch prop makes it a delight to stooge around at 1/2 throttle.

    Interesting the thought that OS will bring out a smaller 4s petrol. I bought the OS 33 , and now have the OS 22. Both Great engines, VERY smooth.
    Regards from 'Down Under.

  5. #30

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    RE: O.S. GF40 4st gas


    ORIGINAL: MKnutson

    I got it all mounted up to the test stand and ran it this evening.
    The idle mixture screw was way too rich, so I leaned it up a bit then it finally started up then we went in a little more to get the idle to smooth out.
    With just 5 mins running on 20:1 mix it turned some pretty good numbers, once loosened up and a leaner oil ratio gets run through it it will get even better!
    Once I get it on the plane I can really tweak the needles like it needs. Transition is ultra quick from idle to full back to idle again.
    We tried a hand full of props to get some figures, all props are Xoar laminated but one Mejlik carbon.

    Mejlik 18-10 8200rpm/1600idle
    Xoar 18-8 7900 1700y
    19-8 7400 1700
    19-10 6700 1700
    20-6 7500 1700
    Keep in mind these will get better with more time and less oil in the fuel, but for now these look pretty good to me.
    This engine runs very smooth and tight, very OS like. Also, the muffler actually works, it sounds like a goood running OS 120 surpass!

    It's a KEEPER!


    Mark.

    Hi Mark

    Are you sure about the Mejzlik? So is it really an 18x10 and not an 18x8? I'm asking as you got 7900 with Xoar 18x8 so a couple of hundreds rpm more with a same size CF prop is what you expect to see..

  6. #31
    MTK's Avatar
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    RE: O.S. GF40 4st gas


    ORIGINAL: AeroFinn

    Hi Mark

    Are you sure about the Mejzlik? So is it really an 18x10 and not an 18x8? I'm asking as you got 7900 with Xoar 18x8 so a couple of hundreds rpm more with a same size CF prop is what you expect to see..
    That's not a surprise really. XOARs are often higher loading than other props of same dia and pitch....BUT they don't produce any more thrust in my experience, just more noise from the tips

    These numbers are300-400 rpm lower than you would get with the GT33 2 stroke..... Plus the GT33 will turn even more prop at surprisingly high rpm. My 33s turn 20x10.5 and 20.5x10 (apc props) at 7400on Avgas, 50:1 mix. Premium auto gas produces a bit more output but it's not necessary for most applications

    It will be interesting to see what the 4 stroke engine can do after full break in. And you gotta love that 4 stroke sound.....
    Regards,
    MattK
    (Rcmaster199@aol.com)

  7. #32
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    RE: O.S. GF40 4st gas



    [/quote]
    That's not a surprise really. XOARs are often higher loading than other props of same dia and pitch....BUT they don't produce any more thrust in my experience, just more noise from the tips

    These numbers areΒ*300-400 rpm lower than you would get with the GT33 2 stroke..... Plus the GT33 will turn even more prop at surprisingly high rpm. My 33s turn 20x10.5 and 20.5x10 (apc props) at 7400Β*on Avgas, 50:1 mix. [/quote]

    Is this with the standard muffler or a pipe?

  8. #33

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    RE: O.S. GF40 4st gas

    with a pipe
    AMA # 126183
    Fly light, fly fast and fly low.

  9. #34
    MTK's Avatar
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    RE: O.S. GF40 4st gas

    The muffled GT33 will turn the same props as the 4 stroker 300-400 rpm more, conservatively.

    The piped GT33 will turn much more prop to the numbers I quoted above. Actually, Avgas produces 300-400 rpm less power than premium auto gas will all else equal. In other words, the same 20.5x10 prop will turn around 7800 on the piped GT33. The 33 is a stump puller and has absolutely great mid range response; the best of any 30-40cc class engine I've played with (but I haven't played with them all, so YMMV....SAP180, ZDZ40RE, Mintor 38, PTE36R and DLE35RA)
    Regards,
    MattK
    (Rcmaster199@aol.com)

  10. #35

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    RE: O.S. GF40 4st gas

    MTK,

    Are you getting the 4 Stroke Itch?
    Is being a Circle Flyer a bad thing?
    Rex Birkinbine

  11. #36
    MTK's Avatar
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    RE: O.S. GF40 4st gas

    Rex, no I am not. About the only thing I like is the sound a 4 stroker makes. Powerwise it is not in the same league as the 33, 2 stroke.....Weight is a fat 1300 grams compared to 950 for the 33. I'd have to design an airframe specifically to cover the extra nose weight and I am not going to do that.... If OS continues development and puts out a 40cc 4 stroker with less weight and more powr, then yes I'd consider it


    ORIGINAL: rexbirk

    MTK,

    Are you getting the 4 Stroke Itch?
    Regards,
    MattK
    (Rcmaster199@aol.com)

  12. #37

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    RE: O.S. GF40 4st gas

    With the extra weight this would be a great engine for some warbirds.
    Michael.M Waco brother #187

    P-47 Brotherhood #22

    And Certified Warbird Nut

  13. #38
    MTK's Avatar
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    RE: O.S. GF40 4st gas

    As an aside, I just ordered the VVRC 40 twin. Vibes and sound should be minimal....I intend to run this one with pipes also andI think it should turn 21x10 apc at about 7K....I'm also in process of making a 19x11 3 blader from modified e-props which should work great on this engine, also should turn around 7K.... Near perfect for whatI do....

    At some point I need to stop all this experimenting. My flying is suffering. I got my ears waxed at last week's contest, by lesser fliers. Aggravates me to no end....LOL



    ORIGINAL: MTK

    Rex, no I am not. About the only thing I like is the sound a 4 stroker makes. Powerwise it is not in the same league as the 33, 2 stroke.....Weight is a fat 1300 grams compared to 950 for the 33. I'd have to design an airframe specifically to cover the extra nose weight and I am not going to do that.... If OS continues development and puts out a 40cc 4 stroker with less weight and more powr, then yes I'd consider it


    ORIGINAL: rexbirk

    MTK,

    Are you getting the 4 Stroke Itch?
    Regards,
    MattK
    (Rcmaster199@aol.com)

  14. #39
    TonyBuilder's Avatar
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    RE: O.S. GF40 4st gas

    I am getting ready to run one of my OS40cc 4s in my Cub this weekend. I will be breaking them in for my Ziroli B-25 build later this year. So fare the engine looks well made short of the throttle and choke arms, they look like toys so I replaced them with aluminum arms. I am making my own muffler pipe and putting the stock muffler in the fuse like the canister installation. The stock setup is not user friendly, ugly as hell.

    TB
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    Fly, fly, fly!!!!

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  15. #40
    TonyBuilder's Avatar
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    RE: O.S. GF40 4st gas

    I got in one flight yesterday. The muffler is working great and the OS40cc four stroke engine is perfect power for a scale cub. The OS has a low idle so not a problem slowing her down. I am running a Xoar 18x8 prop and if I remember correctly I was getting around 7500 rpm. Today I will try to use a Rcxel and get some more accurate readings. So far I like this engine, starts easy, runs smooth and sounds great. The muffler I made is working great so far. I did make a new one from this prototype. I had an aluminum pipe welded to the stock muffler and then a copper 90 brazed to the 16mm threaded nipple. It is solid and strong.

    TB
    Fly, fly, fly!!!!

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  16. #41
    MTK's Avatar
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    RE: O.S. GF40 4st gas


    ORIGINAL: TonyBuilder

    Has anyone used a 3-blade prop on the OS 40cc 4S? I want to put two of them in my 101" Ziroli B-25 the only prop I have seen is the bela 16x10- 3-blade.
    TB
    TB,

    Mezjlik makes a carbon 3 blader that should work well on the 40cc 4 stroker. It's an 18x10. It's pricy tho (80$ plus S+H)....Nevertheless, if 3 bladers are the only thing stoppingthe project, at least they are available

    Regards,
    MattK
    (Rcmaster199@aol.com)

  17. #42
    TonyBuilder's Avatar
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    RE: O.S. GF40 4st gas

    Well the second flight was a bust. Dead stick on the second flight. Flew for 3 min then at mid range on throttle started running rough, then back fire, engine died and spun the prop. Third flight did the same. We tried to get it running so we could adjust the needles but could not get it to fire. Checked the plug and was getting no spark so I will swap the ignition tomorrow and try again. Disappointing to say the least.
    If this was a DLE 30R I would be on the 6th or 8th flight, rethinking if I want to put theses in my B-25!
    Fly, fly, fly!!!!

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  18. #43
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    RE: O.S. GF40 4st gas

    Bummer... [:@]

    What ignition bats are you using, and how is the ignition box installed in the airfram ?
    Sonnich Johannesen

  19. #44
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    RE: O.S. GF40 4st gas

    Currently I am using a 6v nimh1100and the ignition is mounted to a piece of ply secured to the side of the engine stand offs. I mount all my DLE ignitions this way with no problems.
    Fly, fly, fly!!!!

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  20. #45
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    RE: O.S. GF40 4st gas

    Day three on the OS. The factory settings are way off. This engine is not like a DLE where you just mount it, flip it, and fly it. It is very touchy and has been running very rich and keeps fouling the plug, or dead sticks. I got one 10min flight in and some more adjustment, got it around 7800rpm and it was running smooth on the ground, did not get another flight in. Tomorrow I will get some fights in. There is some hope still for this engine.
    TB
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  21. #46

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    RE: O.S. GF40 4st gas

    So far, my OS40 is still running really well. It seems to like the xoar 19-8 on the super sportster.
    The mixture screws are really touchy and don't need to be turned much to make a big difference.
    Currently I'm running stihl hp ultra at 30-1 and it runs clean and doesn't foul plugs.
    Don't give up on the OS yet! It WILL get better with a little more time on it.
    Peak out the top end screw then lean out the bottom just so it doesn't bog while reving up from idle when hot.
    When cold, it should bog slightly when reving up from idle, let it warm up a little. All running them rich does is carbon up the piston and head and valves sooner than you want.

    Mark.

  22. #47
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    RE: O.S. GF40 4st gas

    Today I got the engine running pretty good, 7700rpm on a Xoar 18x8. Too windy with a direct cross so I did not fly. I'm feeling better with this engine.
    TB
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  23. #48

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    RE: O.S. GF40 4st gas

    ORIGINAL: TonyBuilder

    Β*Today I got the engine running pretty good, 7700rpm on a Xoar 18x8. Too windy with a direct cross so I did not fly. I'm feeling better with this engine.Β*
    Β*
    TB

    I still do not get it how some people get 8200 rpm with an 18X10 CF prop while others get 7700-7900 rpm on a wooden prop? Even though carbon props are much more efficient there's still a 2 inch difference on the pitch (which should load up the engine quite a bit) when you go from 18x8 to 18x10..?

    Anyways Tony, happy to hear it's getting better. By the way, as you probably know gas engines are subject to overheating more easily than the glow engines so did you fly the cowl on or off? Baffling? Just in case the engine is still in the middle of runnin in phase..

  24. #49
    TonyBuilder's Avatar
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    RE: O.S. GF40 4st gas

    I'm flying with the cowl off and not breaking in on the ground. It currently doesn't like the cowl on so once the engine has a few gallons threw it I will put the cowl on and see what it does, may need the carb tube mod with a hose to the fuselage to equalize the pressure.
    TB
    Fly, fly, fly!!!!

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  25. #50
    TonyBuilder's Avatar
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    RE: O.S. GF40 4st gas

    Day five on the OS49, I'm done! This engine has been nothing but a big pain and disappointment. There is no way I'm putting two of these in my B-25.
    It was running good yesterday, then today I could not get it started. Had to put another new plug in it. Then it started. Was running ok but still needed some low end adjustment, hardly turned the needle, ran it some more, stopped it to do more adjustments, then started it again. It ran then back fired spun the prop and I could not get it started again, I'm done with this engine. I have hade 6 DLE's and they all are " mount, flip, and fly" with miner adjustments to the hi end as she broke in. So I would not recommend this engine to anyone that does not have a lot of time and patients to mess with it. I'm no gas Expert so maybe I'm not qualified to run this type of engine.
    I will let this engine sit for a bit, going to send the unused one back and get two DLE35R for my B-25. I may try again on the OS40 in my cub, or sell it. Anyone want a great deal on one of these, only got about 18oz threw it! PM me.
    TB
    Fly, fly, fly!!!!

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