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  1. #1
    earlwb's Avatar
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    RCG 26cc gasoline RC engine



    This engine is sold via Hobby King for a pretty low price which makes it pretty attractive. The example I bought came through OK, but apparently on its long boat ride across the ocean to the US warehouse, some of the screws and stuff picked up a little corrosion. Nothing serious, just a bit unsightly though.

    The engine came with all of the basic stuff needed. Some hardware, motor mount extensions, screws, CDI ignition and some unknown brand of CM-6 type of sparkplug. The instruction sheet stated a 17x8 prop would be about right for it. But the LHS only had a Xoar 17x8 wood prop, so I got that.

    I ran three propellers on the engine so far. I plan on trying out some others though. I want to see what a 18x8 prop would do. As the engine seems to really like bigger props on it. But the 17x8 Xoar prop worked pretty good though. According to Pe Reivers' Prop/Power spreadsheet the engine is developing about 2.3 hp to 2.4 so far and it has only hadseveral tanks of fuel through it so far. Plus the fuel had too much oil in it as well as I didn't want to go easy on the oil at first.

    I am planning on using the engine on a huge 1.20 sizeSeagull Gee Bee Z plane that I bought a few years ago.

    Propeller RPM numbers so far gathered:

    Master Airscrew 16x8 composite prop 8,480
    Xoar 17x8 wood prop 7,780
    Master Airscrew 18x6 Classic composite prop 8,130

    I did some further tests and got these results using some 18x8 props
    Master Airscrew Classic 18x8 prop 7,095
    APC 18x8 prop 7,095
    Vess 18x8 Sport prop 7,225
    Xoar 18x8 prop 7,180

    Using Pe Reiver's prop power calculator spreadsheet, with the numbers from the 18x8 props, shows the engine was developing around 2.3 to 2.4 HP and static thrust was about 14 pounds static as well as a calculated airspeed of a little over 53 mph. The 18x8 props keep the peak RPMs under 8,000 rpms by a good margin too. As the instructions state 8,000 rpms is max for the engine.


    The engine was fairly easy to get running.When cold, I would use the choke to get it to pop, runand turn over a few times. Then flip the choke off and flip it again, and usually it would fire up and start running. But I would let it warm up before giving it much more than low throllte. After it was running a while, it would fire up and run on one flip of the prop most of the time. The vibration wasn't really all that bad and seemed to be pretty low actually. I had some other engines glow and ignition that could vibrate the stand apart and one of those made it almost impossible to hold the throttle lever at WOT too.

    The engine is a little on the heavy side but not all that bad though. On the Gee Bee that may be a plus as I won't have to cram and jam everything forward as far as possible.

    The prop washer is loose on the crankshaft end tip. I used some tape to put on the shaft to center the prop washer with. So with a snug fitting prop, you'll have to either put on shrink tubing and shrink it on and then put the prop washer on or make a spacer to fit for it. I think making a new prop washer is a better wayto do it though. I din't really like how they did the three prop mounting screws. As they have the screws pretty far out to the edge of the prop hub. That causes you to drill at least one hole out pretty close to the outer edge of some props. Plus the three holes just don't seem to align well with any props I want to use. But the props I tested didn't break on me, and I was careful to not be in front of the engine where if a prop failed it might hit me. You cannot depend on the center threaded part to hold the prop on either as the hub isn't knurled on the end to grip the prop, and although they knurled the prop washer, that is sort of useless for locking a prop in place. So you have to use the three mounting screws. What I did was fit the prop on, using the prop washer as a guide, center the prop washer and mark the screw hole locations and then drill those out using a drill press.







    you can see some corrosion on the screw heads here in this pic


    engine by itself weighs this much


    Engine with all of its accessories is obviously more heavy



    I am not particularly fond of the three bolt prop hub setup. The washer is knurled but the prop hub end isn't. So you pretty much have to drill holes in the props touse the three screws to hold the prop on with.



    The muffler is pretty nice looking and well made, but it is quite loud though. You'll need a quieter muffler for some flying areas.


    Test running the engine



    A tachometer reading using a Master Airscrew 16x8 composite propeller


    A tach reading using the Xoar 17x8 wood propeller


    A tach reading using the 18x6 Master Aiscrew Classic composite propeller



    The engine temperatures were not bad, the engine right at the base of the spark plug on the head was reading around 382 degrees Farenheit after a few minutes at full throttle.




    Club Saito #722, Sig Kadet Brotherhood #80, GlowHead Brotherhood #14,
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  2. #2
    acerc's Avatar
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    RE: RCG 26cc gasoline RC engine



    Earl I have two of the RCGF engine's. I believe they are spec'd for a max rpmof 8K. I think you wil find with the prop's your running once airborne there is not as much pull as there could/ should be. For me a 18x8 Xoar give's the best thrust - rpm. I would highly suggest propping for around 7500 on the ground.
    I agree totally on the stock pipes, way to load. I went with pitts type. Much better sound.
    You have a nice set-up there. Throw it on some rollers so you can do some thrust test as well.
    And I hope you don't take this as I'm poking at you it's strickly an observational opinion.

    Robert
    Cub Brotherhood #3\\ Ryan STA Brotherhood #4
    Corsair Brotherhood #56\\ Waco Brotherhood #184

  3. #3
    earlwb's Avatar
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    RE: RCG 26cc gasoline RC engine

    Thanks.

    Yeah I have thought about rollers and a weighing scale to determine static thrust too. I just haven't gotten around to doing it.

    I can agree with you in that it likely would run better with a 18x8 prop. I needed to get some more props to test with, I didn't have an 18x8 to try at the time as the 18x8 I had was reamed out to fit a big 1.80 glow engine earlier. I have to see if the hobby shop has one or whether I need to order it in or not. 

    I am thinking that the 17x8 is marginal for the size as the instruction sheet stated 8,000 rpms was tops for the engine. They stated a 17x8 prop would turn 7,200 RPMs and my engine beat that by about 500 or so RPMs. But I don't know what prop they used though. At 7,700 rpms or so, the engine would likely rev more in the air going over 8,000 RPMs, if that is really the limit for it.

    But the engine was, according to my spreadsheet, developing more than 13 pounds of thrust with the 17 inch and 18 inch props sop far. If the plane comes in weighing about 10 pounds or so, it wouldn't be all that bad then. It has a huge fuselage but a relatively small wing.
    Club Saito #722, Sig Kadet Brotherhood #80, GlowHead Brotherhood #14,
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  4. #4
    acerc's Avatar
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    RE: RCG 26cc gasoline RC engine

    Yea ! I'm the same way, can't never seem to get around to it. Mine are in a 1/5 scale Waco at 17lbs with a 18x8. And the other is in a 1/4 scale Cub at 16lbs with a 17x8. The Cub needed a bit smaller prop so I adjusted my throttle so I don't over rev. I don't know either if running above the max rpm would hurt anything. But I don't want to be the one to find out. I will tell ya, I just learned that a plug in type tach is much more accurate. Or so I was told by someone I trust to know his stuff. Needless to say I bought one for final tuning.
       Keep up the good work.
    Robert
    Cub Brotherhood #3\\ Ryan STA Brotherhood #4
    Corsair Brotherhood #56\\ Waco Brotherhood #184

  5. #5
    acerc's Avatar
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    RE: RCG 26cc gasoline RC engine

    Oh! Almost forgot. I have a total of five RCGF's and all of them needed the tape around the prop shaft.
    Robert
    Cub Brotherhood #3\\ Ryan STA Brotherhood #4
    Corsair Brotherhood #56\\ Waco Brotherhood #184

  6. #6
    earlwb's Avatar
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    RE: RCG 26cc gasoline RC engine

    That is interesting in that they seemed to have made the prop washer a bit oversized to fit the prop shaft.

    I found some more 18x8 props at the local hobby shop, I can try. I need to drill the out first though.

     A while back I bought a RCexl tachometer but it didn't work all that well for me with other engines using RCexl CDI units. It seemed to be too sensitive to RPM changes and it's update rate was too fast, thus making the numbers difficult to read with the digits changing fast. It might be bad though as it seemed to reset itself a lot too.


    Club Saito #722, Sig Kadet Brotherhood #80, GlowHead Brotherhood #14,
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  7. #7
    acerc's Avatar
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    RE: RCG 26cc gasoline RC engine

    Well that is not what I wanted to hear. Tomorrow I'll have to fire up an engine and see if this tach suck's like your's.
    Robert
    Cub Brotherhood #3\\ Ryan STA Brotherhood #4
    Corsair Brotherhood #56\\ Waco Brotherhood #184

  8. #8
    earlwb's Avatar
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    RE: RCG 26cc gasoline RC engine

    Well, I did see a number of videos where everyone else seemed to be having much better luck than I had with the plug in tach. So maybe it was just mine. There might be a RPM limit beyond which they don't work right. I was trying it on the little NGH 9cc engines that can rev over 12,000 rpms no problem and maybe the tachs don't really like that.

    Club Saito #722, Sig Kadet Brotherhood #80, GlowHead Brotherhood #14,
    AMA # 928076

  9. #9
    earlwb's Avatar
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    RE: RCG 26cc gasoline RC engine

    I did some further tests today and got these results using some different 18x8 propellers:

    Master Airscrew Classic 18x8 prop 7,095
    APC 18x8 prop 7,095
    Vess 18x8 Sport prop 7,225
    Xoar 18x8 prop 7,180

    Using Pe Reiver's prop power calculator spreadsheet shows the engine was developing around 2.3 HP and static thrust was about 14 pounds static as well as a calculated airspeed of a little over 53 mph.The 18x8 props keep the peak RPMs under 8,000 rpms by a good margin too. As the instructions state 8,000 rpms is max for the engine.

    I ran out of time, but it might have been interesting to see what a NGK spark plug would have done in comparison to the no name brand OEM plug that came with the engine when I was running it.


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    AMA # 928076

  10. #10
    acerc's Avatar
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    RE: RCG 26cc gasoline RC engine



    Just a couple of ideas for ya. If you have not yet, try some full synthetic oil @ 45-1. Also if you want to boost the engines performance put a Bowman ring in it. I've been running some test on normal oil versus synthetic. Synthetic runs a little cooler and give's a couple hundred more rpm. The Frank Bowman ring also boost the rpm by 2-4 hundred rpm's. And I feel a little more horse as well. With these mod increases you could increase the prop for more speed. Which is what you will need for the GeeBee.
    I like what your doing keep it up.

    Robert
    Cub Brotherhood #3\\ Ryan STA Brotherhood #4
    Corsair Brotherhood #56\\ Waco Brotherhood #184

  11. #11
    earlwb's Avatar
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    RE: RCG 26cc gasoline RC engine

    Yes I use Amsoil Saber Pro air cooled two stroke oil. Even though Amsoil says the oil is good down to a 100:1 ratio, I do not use that little amount.  I am still using up some fuel in the gallon jug with around a 25:1 ratio, then I'll mix up a batch at 32:1 and see what happens, along with using a NGH spark plug too.

    Now in comparing the engine to a NGH 25cc engine the RCG 26cc engine has a little more power. It develops around 0.2 more horsepower and can turn larger size props better. So even though it weighs more, it isn't doing all that bad in comparison to other engines like it.

    Yeah I did seriously think about a Bowman ring too. But I thought I would see what it did using the OEM stuff instead.

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  12. #12
    acerc's Avatar
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    RE: RCG 26cc gasoline RC engine

    If your still entertaining the ring, best to do it before breaking in the cylinder walls.
    As you I would never run 100-1 of any oil. 45-1 is a safe level but I would not go leaner. Lubrication does require some oil to be there. Some guys don't realize R/C engines are not their weedwackers. They are smaller, lighter built, and lower quality.
    Robert
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  13. #13
    earlwb's Avatar
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    RE: RCG 26cc gasoline RC engine

    Well weed wackers, leaf blowers, etc are not run WOT for long periods of time like RC model airplane engines are as well as being under a high load too. So what may work for a trimmer engine won't work for a RC model airplane engine. So the engines need the extra lubrication.

    Since the engines are so cheap, if this one hangs in there for a while, I might get a second engine and put the Bowman ring on it. Or a new cylinder and piston since they are pretty inexpensive.




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  14. #14
    acerc's Avatar
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    RE: RCG 26cc gasoline RC engine

    Earl it's been a while anything new figured out?
    Robert
    Cub Brotherhood #3\\ Ryan STA Brotherhood #4
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  15. #15
    earlwb's Avatar
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    RE: RCG 26cc gasoline RC engine

    Well nothing new popped up. My 26cc engine seems to be holding up OK. I did switch to Stihl HP Ultra synthetic oil instead of using Amsoil Saber Pro as it doesn't leave as much carbon deposits on the engines at higher oil ratios. The Amsoil oil worked good, but I was getting more carbon than I liked though. So I am trying out Stihl to see how it does. With my little 9cc gas engines the Amsoil oil left some carbon on the piston and combustion chamber but it wasn't too bad. I had run about a gallon or two of fuel through the engines at a 25:1 ratio. So I'll see what Stihl;s Ultra oil does in comparison.

    Club Saito #722, Sig Kadet Brotherhood #80, GlowHead Brotherhood #14,
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  16. #16
    acerc's Avatar
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    Good to hear all is going well. I use Stihl Ultra as well at 40-1 and it has served me well. And that tach we spoke of is working out real well also. Really helps fine tuning and because of it I bought an onboard recorder for the tack and temp. Blew me away when I first saw the readings.
    Robert
    Cub Brotherhood #3\\ Ryan STA Brotherhood #4
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