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  1. #1
    H5487's Avatar
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    Please rate these little motors

    I've been cruising the 1/2A forum and I've read some good things, and some not-so-good things about the following motors that I have on hand...

    Thunder Tiger GP-07
    This is a new engine that I purchased about two years ago but have yet to run. Says Made In China on the box but looks to be nicely built.

    AP .061 Wasp
    This is also new and appears to be nicely built. Also made in China.

    Norvel .061
    This one is used but appears to be in good condition. It was given to me by a modeler who could never get it to run right. The box says Made in Russia.

    I have a couple of small (45" WS +/-) OT FF projects that I would like to power and I need to know which engine(s) to use vs which aren't worth the effort to mount. Please feel free to PM me if you prefer not to go public with your opinions.

    Thanks,

    Harvey
    Last edited by H5487; 11-03-2013 at 12:09 PM.
    Weather Geek

  2. #2
    Mr Cox's Avatar
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    The Norvels are very good, the TT 07GP is not too bad if it is the latest design, and the Wasp can be made to run, unless you got a real leamon..

  3. #3
    combatpigg's Avatar
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    The AP.061s served me well as $30 engines that needed almost zero break in. I used them almost exclusively for RC Combat to tow around 13 oz flying wings and 20 foot long streamers. I would always take .020" stainless safety wire to cinch down the mufflers better than the standard wire clips could.
    The down side to these engines is the crank shaft would get sloppy in the crankcase and present air leakage that compromised the fuel draw. The worst cases might not have lasted beyond 100 ozs of fuel before this sort of failure.

    It has been several years since I bought one of these engines so I have no idea what the situation is nowadays. A lot of flyers might rate them as being good engines but ask them how much 1/2 A flying they actually do on a yearly basis. For some of these folks, 12 flights out of 1 engine might be a whole year's worth of "work".
    WHO GUNNA FEED MAW KEEEIDS..???

  4. #4
    combatpigg's Avatar
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    The Norvel AME .049 works best with crankcase pressure and relatively small props like a 5 x 3 [or 4.2 x 4 on really small racer type planes]
    The main problem I've had with these engines is the cylinder getting gouged from poorly designed method of retaining the wrist pin.
    Gouges / scoring usually originate from where the piston has been "peened" [or disfigured] to keep the wrist pin from wandering out of position.
    I have run 25% oil in these engines [which always seems to help] but the long term results from running these engines for 20 years is a fishing tackle box full of salvaged parts and a lack of serviceable pistons and liners.
    A really good AME can turn a Cox 5 x 3 prop over 26,000 right out of the box and haul 12-13 ozs vertical like a rocket.

    The Norvel Big Mig .049 is probably a better choice for most flyers who want an engine that is designed to run at lower rpms with 6x3 props. They cost more up front than the AP .061 but will pay you back with more resistance to wear and tear. I don't know what their current market value is for NIB but I would gladly pay $60 for a new one.
    Last edited by combatpigg; 11-03-2013 at 01:52 PM.
    WHO GUNNA FEED MAW KEEEIDS..???

  5. #5

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    starting small engines: initially need to make engine rich then close the throttle valve,glow the glow plug and start engine, as soon as engine starts you must gradually and slowly open the throttle valve until you get smooth run, the fuel which you are using need to be at least 15% nitro, i can say for small engines to run smooth, nitro is a must.
    so i would say for the engines which you mentioned if you want to know their performance you need to check the manufacturer information , and make the best choice, but for starting engines especially the smaller ones you need to know some hints, as i said above.
    i will look forward for any further assistance if you need from me.
    Last edited by 05121344; 11-03-2013 at 02:07 PM.

  6. #6
    H5487's Avatar
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    Thanks for your comments, guys!

    What do you think of the new .049s coming from Cox International?

    Harvey
    Weather Geek

  7. #7
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    The Norvel .061 I bought new doesn't idle really at all. I Have heard they are like that until broken in which takes a while, and a newer style plug helps. I have another .061 from a swap meet in a plane that runs and idles very well. Very well. yes I said it twice. I have three TT .07's bought used. One is pretty much worn out as I got it, the other two run ok, not real fast, but idle very well and are mild mannered. They all have too much clearance on the crank to case. I tried correcting this on a couple with mixed results. The one is just worn out I guess. I made a Turbo plug insert for the TT, and they go as good as a Norvel .074 which is really great. I suppose I am hinting that a Norvel is a good choice. I have had good luck with AP and ASP motors, the .09, and both .15's, but not the .06. Some people haven't luck with the larger ones, but I think a newer one would be fine. Carb problems, and fussy people IMHO. Certainly any are better than the old reedies.

  8. #8

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    061 MP Jet glow or diesel just about perfection have 3 ==061diesels great quality Czech made martinClick image for larger version. 

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    Last edited by AMB; 11-03-2013 at 05:40 PM.

  9. #9

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    The Cox Sure Starts are excellent engines with decent power and a reasonable price. Great for planes that weigh less than 18 oz or so, less than 16 oz is very nice. They do take a little getting used to if you don't have experience with small engines. My friends and I like to build pylon racers powered by these engines and race. Our racers weigh 9 oz to 12 oz. Just a sport race nothing serious. The engines start easily and are reliable once you learn a little about them. Plenty of info about them here on RCU.
    Last edited by 049flyer; 11-03-2013 at 11:15 PM.
    I fly aircraft at the leading edge of trailing edge technology!

  10. #10

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    in these size engines no engine can be compared with Cox TD 051 R/C or non R/C , you should try to find a good second hand or perhaps a new one in ebay.

  11. #11
    skaliwag's Avatar
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    The 051 is not so plentiful as the 049.
    .002ci makes no significant increase in performance. I see the TD 049 go for under $40 on the big auction block.
    Real Airplanes have Round Engines and Two Wings.

  12. #12
    H5487's Avatar
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    Quote Originally Posted by skaliwag View Post
    I see the TD 049 go for under $40 on the big auction block.
    Wag,

    The new Cox .049s are only about $5 more. What do you think of their quality?

    Harvey
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  13. #13
    aspeed's Avatar
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    As per your original post for a Free Flight, I would go with the Norvel, but all three that you have are similar. I guess a throttle isn't an issue then. I wouldn't buy another motor to replace any of the three you have. A TD is a good motor, but so are the others. I checked a few .049's a while ago, on the same prop. 4.2 - 4" APC. A fairly small one. TD .049 22,900 rpm, Norvel .049 22,500rpm. The .06 would go a bit better than the .049. I tried a 6-3" MA prop and got 16,500, a TT .07 got 15,000 with a bigger 6 - 3.5". (The Norvel .074,which you don't have went 18,900 rpm on the same 6 -3.5 prop.) Not the greatest to compare, but the others were all without muffler, and quite similar really.

  14. #14
    H5487's Avatar
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    [QUOTE=aspeed;11654581]As per your original post for a Free Flight...I guess a throttle isn't an issue...

    Speed,

    Your reply made me reread my original post. I should've said that the airplanes will be radio-assisted vintage free-flight designs. So, yes, throttle-ability is desired (but not necessarily mandatory).

    Harvey
    Last edited by H5487; 11-04-2013 at 05:57 PM.
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  15. #15

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    I have seen the exhaust restrictor type of Cox throttle work very well and they are cheap. Cox International also sells a throttle that attaches to the choke tube for the Sure Start but I have not tried one yet. The throttled SureStart is probably close to the price of a throttled Norvel.

    The Sure Start performance is the same or a tiny bit more than a Cox Black Widow. With the high compression head from Cox International the power is noticeably more. However the exhaust throttle usually reduces performance a bit.

    One thing to consider when buying a used TD is the plastic venturi mount tends to crack and leak air causing eratic operation. I am in the process of rebuilding 10 or so of these engines and over half have a crack. No big deal if you know what to look for and have a spare on hand. No matter which engine you decide on, plan on buying a few parts to support it.

    I think the Norvel is hands down better than any of the Cox engines but it will cost you more.

    It all boils down to how much power do you need and how much do you want to spend.

    It would help if you told us the weight of your plane ready to fly, and your budget.
    Last edited by 049flyer; 11-05-2013 at 03:29 PM.
    I fly aircraft at the leading edge of trailing edge technology!

  16. #16

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    I have a Thunder Tiger .07 on a Jr. Falcon and it pulls it around nicely with a 6 x 3 prop and 25% Nitro. I would guess it's power to be similar to the Cox Sure Start but it is much heavier. It does have a throttle and muffler. It idles OK but not as reliable as the Norvel .061 and nowhere near as powerful.
    I fly aircraft at the leading edge of trailing edge technology!

  17. #17
    H5487's Avatar
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    Quote Originally Posted by 049flyer View Post
    It would help if you told us the weight of your plane ready to fly, and your budget.
    Flyer,

    The plans estimate a finished weight of 24oz. Note that I'm not setting this plane up for 3D; just a mild-mannered little lazy floater. The budget isn't unlimited but I'm not holding a sign on a street corner either. Yet.

    Harvey
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  18. #18
    H5487's Avatar
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    Quote Originally Posted by 049flyer View Post
    It would help if you told us ...your budget.
    Flyer,

    Please note at the beginning of the thread that I already own a TT 07, an AP 61, and a Norvel 61 and I'm trying to decide which one to use. (And which not to bother with.) However, since starting this thread, I've also discovered the new Cox International website. I know that Cox's glory years are behind it but that was my first engine 50 years ago so there's a nostalgia factor that favors buying a new Cox .049 RC.

    But I'm not 100% sold on the Cox just yet. The practical side of me reminds me that I've got three potential candidates already bought and paid for.

    Decisions, decisions...

    Harvey
    Last edited by H5487; 11-05-2013 at 08:31 PM.
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  19. #19

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    Quote Originally Posted by H5487 View Post
    Flyer,



    But I'm not 100% sold on the Cox just yet. The practical side of me reminds me that I've already got three potential candidates bought and paid for.

    Decisions, decisions...

    Harvey
    Which NORVEL do you have? Is the cylinder silver or slightly gold colored with notches for the cylinder screws or is it black with holes to access the cylinder screws.. Does your carb have retainer screws to hold it in the crankcase? There is a NORVEL faq sitckied at the top of this forum with pictures to help you identify your engine. NORVELs are not necessarily a beginners engine and can be difficult to start initially. They also take quite a bit of time to breakin. I do not support the later model recommendation to cold flip the engine until the top end pinch is relieved. I believe that this approach just causes premature wear. I generally use heat (monokote gun) to preheat the cylinder for initial starting. When your engine does start, get it up to running temp quickly --- these engines are not set up to run sloppy rich and cool, but rather run it at a rich two cycle during the breakin period.

    My ranking would be the NORVEL first --- it's light, a horse and well made. The TT07 is heavier, is ranked somewhere between a good .049 and a highend NORVEL .061, but most of the .07's are well behaved, have good throttling and are fairly consistant runners.

    The AP's are Chinese knockoffs of the early model NORVELs without the fit. Most have a reputation of being short lived. Some can be made to run; some are junk.
    the "other" andrew
    I'm not older than dirt, but I can remember when it was patent pending

  20. #20

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  21. #21
    H5487's Avatar
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    Thanks, Andrew, for the very informative post. Unfortunately, I'm away from my Norvel right now and won't be able to answer your questions for a couple of weeks. Despite whether my Norvel is one of the desired ones or not, it is still a second hand engine that the first owner couldn't get to run right. I have no idea how he treated it.

    It sounds like you're in favor of the little Thunder Tiger if the Norvel doesn't work out.

    I might relegate the AP to being a paperweight.

    Thanks for your thoughts!

    Harvey
    Weather Geek

  22. #22

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    Harvey:

    I'm sorry for being redundant, I forgot all about your initial post and got caught up in the moment talking about engines. I think that at 24 oz the Cox would be hard pressed to deliver stellar performance. The Thunder Tiger is not any more powerful than the Cox and weighs much more. My choice would be the Norvel.
    I fly aircraft at the leading edge of trailing edge technology!

  23. #23

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    One other thing about the NORVELs, they're ported to turn up and should not be over propped. My inclination would be to run a 5x3, 5.25x3 or 5.5x3. COX propellors are available from COX Int'l in Canada or from EX Model Engines here in the US. If you can't get your hands on one of these, you can cut down a MA 6x3 to a shorter length.
    the "other" andrew
    I'm not older than dirt, but I can remember when it was patent pending

  24. #24

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    For a floater type of plane maybe an APC 6 x 2 would work well on the Norvel.
    I fly aircraft at the leading edge of trailing edge technology!

  25. #25
    H5487's Avatar
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    If my second-hand Norvel turns out to be unusable, what do you think of the new Norvels (per the link that Danilo provided)? I have always heard that the old Big Migs were tops but the new company isn't producing the same quality. True? False? Somewhere in between?

    This thread has been a real help so far. Thanks for your posts!

    Harvey
    Weather Geek


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