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Cox .074

Old 03-09-2012, 09:43 AM
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klord125
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Default Cox .074

I have a new in box Cox .074 w/throttle. Is this a decent engine. I don't see to many around or being used. Looking to build a small plane to put it in like a sportster type? Thanks Ken
Old 03-09-2012, 10:15 AM
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combatpigg
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Default RE: Cox .074

In the Klingon language, "Cox .074" translates directly to OINK.
Pretty hard to believe, but it's just one of those facts you read about nowadays.

I would run your QueenBee before committing a model to it. See how well it handles a 6x3 prop.
You might have a good one that was hand fitted to be run by an engine reviewer, you never know.
Old 03-09-2012, 10:45 AM
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klord125
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Default RE: Cox .074

Thanks for the info combat. I might fire it up on the stand?? What was some of the issues? I have a OS .10 I can use. I'm looking for a set of plans for a sportster for a .10 size . Any ideas Thanks
Old 03-09-2012, 11:45 AM
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Default RE: Cox .074

Use the .10. The .074 is an overweight underpowered turd. I had one and it had less power than my TD 051 for it's weight.
Old 03-09-2012, 11:52 AM
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Default RE: Cox .074

Yeah I mean .074 is no way gonna fly a .10 sized plane, just use the .10.

Old 03-09-2012, 11:57 AM
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Default RE: Cox .074

a few years back there was a guy on the forums with plans for a .10 sized "little ugly stick" type plane. I always thought one of those would be cool, but never got around to building it.

Old 03-09-2012, 01:05 PM
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Default RE: Cox .074

I've had two .074's that ran quite well with no work at all. Ran one as a pusher and the other as tractor. One nice thing about a reed valve engine. Think of it as a portly .049 that throttles well. I found a 5.7x3 up to a 6x4 worked quite nicely, with good power.
Old 03-10-2012, 05:09 AM
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klord125
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Default RE: Cox .074

Thanks for the help. I was looking for plans for something in the .074 size or .10 size.
Old 03-10-2012, 08:52 AM
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Default RE: Cox .074

I got an .074 at a swap meet with a Jr. Skylark or Skyhawk or something like that. I could not even get it going and was kind of mad with the motor.  I took it out to replace it with a Norvel .06 after a few years, and tried the motor on the test stand and it runs fairly good without the muffler at least. Maybe I'll put it back.  It is a reed valve motor though so it is no ball of fire.  I got 15,400 rpm on a 6-3 1/2" prop without the muffler.  I would rate it about like a worn Tee Dee .049 with a better throttle. I wouldn't reccomend buying one, but you have it already like me, and they are ok for sporty stuff.  An AP .09 ASP .12 or almost anything would be better, but run what you brung.  I think any .049 sized plane would be fine with that motor, but a .10 to .15 size plane would be anemic.  There are lots of plans and kits for .049 stuff likely here on rc groups.  Even some ARF electric planes should be good to convert. 
Old 03-10-2012, 10:53 AM
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hkbii
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Default RE: Cox .074

Howdy gents.
kloard 125, heres a pic of a plane I designed for the os.10. I have had a .o49 to .15 . it can bee built with the speed wing of the longer wing. I have the plans completed but not the con,manuel I called it Zipp. there is a build thread here or look at my profile under my pics. hkbii
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Old 03-10-2012, 11:32 AM
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Default RE: Cox .074

That looks like an AP .09 on that one.  Mine puts out about 1,000 rpm less than my LA .10.  Pretty good for the smaller size and $.  The plane looks good.
Old 03-10-2012, 11:49 AM
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Default RE: Cox .074


ORIGINAL: WINANS

I've had two .074's that ran quite well with no work at all. Ran one as a pusher and the other as tractor. One nice thing about a reed valve engine. Think of it as a portly .049 that throttles well. I found a 5.7x3 up to a 6x4 worked quite nicely, with good power.

I'd say that's a pretty accurate description, a nice running and quiet engine for the sport flyer. For some at the time, the .074 was the right engine despite it being looked down on by most (me included) nowadays.

The biggest flaw the .074 had IMO was that it was extremely sensitive to prime. More than a half drop would flood it. I flew mine in an Aerocraft Snapper and found it to be underpowered-not to the point it wouldn't fly it or do basic aerobatics, but the pitch speed was so low on a 6-3 prop that it might not have any forward airspeed on windy days.
Old 03-11-2012, 08:04 PM
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klord125
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Default RE: Cox .074

I have 1/2a sterling fledgling. Will the .074 be Ok for that??
Old 03-12-2012, 06:56 AM
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Default RE: Cox .074

I haven't seen one live, but from a search I just did it looks about perfect.  I would say anything around a 42" wingspan would be about right.  The Mini Fledgling is 40" so ya looks good. The .074 puts out about the same power as an .049 with a better throttle,so anything around that size is good. And it has built in noseweight with the heavy muffler. (removeable)
Old 03-12-2012, 08:32 AM
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klord125
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Default RE: Cox .074

Great.. Thanks for the info. Yeah the muffler is pretty decent size. You can remove it?
Old 03-12-2012, 09:38 AM
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Default RE: Cox .074

Yep, just unscrew the cyl. You pretty much need the wrench. More power if there are no rules at your field.  The muffler isn't too bad though, probably.
Old 03-12-2012, 12:17 PM
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Default RE: Cox .074

The regular glow plug is a power robber, with a regular 09 head it will do close to 18000rpm on a 6x3 and about 16000rpm on 6x4. That's better than any .049 engine I've had on the same props.

I have put a little bench run here; [link=http://rcuvideos.com/video/Cox-Queen-Bee] QB on a 6x3 prop[/link]
Old 03-12-2012, 04:09 PM
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Default RE: Cox .074

Mine does 15,400 no muffler on a 6-3.5" Windsor Airscrew prop. with the replaceable plug. That is likely why it is slower than yours. Just to compare, my Thunder Tiger .07 was 14,900 but at one point it got 16,200 (I think because the crankcase happened to seal better on that run) and my Big Mig .074 was 18,900 rpm. All on the same prop and no muffler and 10% with a bit of extra castor. The Big Mig is still pretty tight, it is on the second run and I didn't want it too lean for long. I didn't check any .049 motors yet (lots of .15s though) but I think they might turn a 6-3" almost there with the Queen Bee on the 6-3.5". I was quite happy about the Queen Bee when I got it running because the plane I bought it with wouldn't get a run at all for some reason and I wanted to replace it with the Thunder Tiger. I put the Queeny on a test stand and it ran better than the other one.
Old 03-12-2012, 06:59 PM
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Default RE: Cox .074

Another bit of Queen Bee trivia. My son had one with all the usual noted characteristics and in addition was also a real bear to hand start. It came new with an atrocious amount of ball joint slop. I tightened it up for him and it really did improve the starting, but as I recall didn’t do beans for the running.
I’ve had other engines years ago that I couldn’t hand start until the ball joint was tightened. I’ve theorized that the slop reduces crankcase compression during cranking? Once started, it didn’t seem to affect the running in any case.
Al Lenz
Old 03-12-2012, 10:45 PM
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Default RE: Cox .074

Al, your idea makes sense. Slop would reduce pumping action.......The Queen, she was a sloppy Bitc......

A good sales pitch / slogan for the QB would have been....."The perfect engine for those who are afraid of having too much fun".



Old 03-15-2012, 04:41 PM
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Richard-RC
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Default RE: Cox .074

I have just acquired a QB .074. By the tenure of the posts it is a real dog. I haven't run it as yet but hope to soon. I would like to get a muffler for this engine. Also soul be interested in the Mini fledgling. Any thoughts where I could acquire one or both? Thanks
Old 03-15-2012, 06:59 PM
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Default RE: Cox .074

I can't really help you out on the muffler as I need mine but I wouldn't really call it a dog, maybe a sick puppy.  Any reed valve motor is going to be less powerful than a proper one and it shouldn't be compared to a rotary valve motor.  I don't really like to run the reed valve .049 motors any more either, but they have their place and perform ok for what they are and can be made to go better with modifications at the expense of longevity. I would still run them in Mouse races if they still ran them here.   I got 15,400 rpm on the QB with a 6-3.5" prop and no muffler which was comparable to the Thunder Tiger .07 which has it's own problems like everything else. If you want to fly around and have fun, I can't see the QB stopping that.  The Norvel might be a little more fun with about 3,000 more rpm and the Foras and other Russian motors might even scare you a bit.
Old 03-16-2012, 12:45 PM
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Default RE: Cox .074

I still have a couple three of the .074 Queen Bee engines and the ones I ran all worked OK. They aren't super power engines like some guys were hoping for but they work OK. I think some people expected more from the engines but at the time that was not what Cox was marketing or making the engines for. They are a decent good sport engine in the .074 engine displacement range.
The muffler does restrict the engine a lot, but nowadays we have to use them, so one just gets used to it and the less power you have accordingly.

At the time that 1/2a engines were really popular. The .09 and .10 engines were all denegrated and looked down upon as being under powered and too heavy. I remember guys bad mouthing the .10 engines all the time stating a good .049 engine weighed less and had more power than the .09's or .10 engines had.
The trick is to choose a airplane to better match the engine's power potential for the best flights.



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