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.o49 engines by cox

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.o49 engines by cox

Old 04-15-2008, 09:30 AM
  #26  
Bugzidor
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Default RE: .o49 engines by cox


ORIGINAL: Mr Cox

Nice job, but I think there is an inherent problem with a carburator on a reed engine?
The reed only closes due to a higher pressure in the crank and that''''s fine at full throttle but near idle the restriction of the carburator gives an underpressure. This would be ok if it stayed constant but as the reed is shut (do to a higher pressure in the crank) the throttle is still "leaking" and the pressure will continue to rise on the wrong side of the reed... [:''(]

I think the TeeDee would be much better suited for a carburator, please feel free to prove me wrong.
I agree with you about the carb. on Tee Dee, which has more suitable, but, it also possible to use with reed type engine, eventhrough, the response time, might be slightly delayed. Anyway, what would be the effect, you expect to see on the ''leaking'' problem?
Old 04-15-2008, 01:17 PM
  #27  
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Default RE: .o49 engines by cox

I simply don''t think that the reed is able to operate and shut the inlet like it should, since it is only relying on pressure differences to do so.
Old 04-15-2008, 02:33 PM
  #28  
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Default RE: .o49 engines by cox

With that thinking, the reed should work just fine. The pressures inside the engine shouldn''t vary much with RPM, just the frequency of the pulses. Seems I heard somewhere that the limiting factor in a reedie''s performance is the reed...tends to float at high RPM. I''m betting the reed performs better at lower RPM - more time to overcome inertia.
Old 04-15-2008, 02:48 PM
  #29  
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Default RE: .o49 engines by cox

The reed valve will be less effective when the throttle is closed down and the RPM and pressure differential are lowered,
which I think will cause a leaning out of fuel mixture. So you probably wont be able to acheive as low an idle speed
as with a rotary valve. You may have to richen overall mixture. But the concept does appear to work, especially with the choke tube throttle which inherently increases fuel mixture as you close down the choke valve.
Old 04-15-2008, 02:49 PM
  #30  
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Default RE: .o49 engines by cox

It is not the rpm itself that I'm after, it is the low pressure caused by the restrictive throttle that I think cases problems for the reed.

Maybe I'm looking for a solution to a problem that''s not there, but there is something about the reeds and a throttle that is not working well.
Old 04-15-2008, 03:03 PM
  #31  
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Default RE: .o49 engines by cox

There''s youtube videos of throttle-converted SS''s that idle beautifully. Of course, the QB didn''t idle so well, but I think that was just ''cuz of the lousy carb it had.

The proof will be in the numbers when he runs it...then we''ll all know.
Old 04-15-2008, 03:30 PM
  #32  
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Default RE: .o49 engines by cox

propjobbill , are you saying that you reset the piston on a brand new engine? How does give you more performance and why do you have to do it on a new engine? Thanks.
Old 04-15-2008, 04:41 PM
  #33  
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Default RE: .o49 engines by cox


ORIGINAL: rc2007

propjobbill , are you saying that you reset the piston on a brand new engine? How does give you more performance and why do you have to do it on a new engine? Thanks.

I imagine propjobbill does it for the same reason I do. I have found the fit on new Cox engines variable. Aside from any effect on performance a sloppy rod/piston fit will accelerate wear.

jess
Old 04-16-2008, 12:02 AM
  #34  
air-madness
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Default RE: .o49 engines by cox

That''s exactly, I mean exactly what I''ve done! I used an AP .061 carb though. I have been meaning to post some pics. My wife and I are in our newly constructed home now, I just need to get the things from my mother-in-laws house over to this one. I may even post some pics of our new home; I''m very proud of it.

I don''t have any problems at all with idle, transition or the likes, however, it does have a rather high idle. Who cares though, I now don''t have an .049 screaming constantly.
Old 04-16-2008, 06:53 AM
  #35  
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Default RE: .o49 engines by cox


ORIGINAL: jessiej


ORIGINAL: rc2007

propjobbill , are you saying that you reset the piston on a brand new engine? How does give you more performance and why do you have to do it on a new engine? Thanks.

I imagine propjobbill does it for the same reason I do. I have found the fit on new Cox engines variable. Aside from any effect on performance a sloppy rod/piston fit will accelerate wear.

jess
Same here.
Old 04-16-2008, 12:07 PM
  #36  
Clay Walters
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Default RE: .o49 engines by cox

I feel fortunate so many knowledgable .049 folks are around. After fussing for days with a formerly great running Black Widow that had been put away and permitted to gunk up; I ordered a couple of the Sure Starts even though a good many threads/posts had me wondering about how good they''d be.

Well, I''ve run-in two of them now and have to same I am impressed. Seems like they''d properly headspace just from running. At any rate, I just removed the stack off the back and bolted them to a Slickmount. They run for 11-12 minutes on a tank while they''re rich and breaking in. You can see the grey residue running off the block as they wear in and then clear up at the same time they smoothout. Who knows how long one will last but as smooth as they are going I have to wonder what the clues are that a piston reset needs to be performed?

Genuinely curious,

Clay
Old 04-18-2008, 08:03 AM
  #37  
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Default RE: .o49 engines by cox


ORIGINAL: Clay Walters
...Who knows how long one will last but as smooth as they are going I have to wonder what the clues are that a piston reset needs to be performed?

Genuinely curious,

Clay
Clay,

With the backplate off, turn the prop until the piston is partway up and hold it there until gas escapes past the piston and it will hold that position. Now VERY GENTLY rock the prop just enough to see movement in the crankshaft but not move the piston. There will be a little slop on the lower end at the crankpin. Any extra slop of the conrod moving without the piston moving is ball-socket slop. You can see it if you look up into the bottom of the piston.

Another way is to remove the piston and, holding it so you can see the bottom, push and pull on the conrod. Very slight looseness is tolerable. Ideal is little or no slop, without binding.

The faster you run the engine, the closer the fits need to be. In all honesty, I ran Cox engines for many years of sport flying without owning a reset tool. But then it was sport flying with no more than 25% nitro, ~22% oil, and usually a large (6x3) prop.

George
Old 04-18-2008, 11:32 AM
  #38  
Clay Walters
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Default RE: .o49 engines by cox

Thanks George. I recently purchase a 5.5-? prop since it was the only .049 prop the shop had -but haven't tried it yet. (That's how it was actually labeled!)

Still using a couple of 6-3 windsor props I have from 20+ years back and have started looking to see who carries the small stuff. Dissappointed to see it start drying up and suspect a revival of interest at some point. (Seems like that's how it always goes)

In the meantime, now that my interest has been revived I need to locate sources.

Unless you think the 5.5 (don't recall pitch) will introduce problems I guess the 12,000 rpm range gives me minimum exposure?

Regards,

Clay
Old 04-18-2008, 12:05 PM
  #39  
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Default RE: .o49 engines by cox

There is a member here ( Skaliwag ) who is a Cox Guru and has a website with Cox engines and parts and lots of nice kits and hardware etc for 1/2a and small planes. He has been a big help to me. His website is: www.selecthobbies.com
Old 04-21-2008, 01:23 PM
  #40  
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Default RE: .o49 engines by cox


ORIGINAL: air-madness

That's exactly, I mean exactly what I've done! I used an AP .061 carb though. I have been meaning to post some pics. My wife and I are in our newly constructed home now, I just need to get the things from my mother-in-laws house over to this one. I may even post some pics of our new home I'm very proud of it.

I don't have any problems at all with idle, transition or the likes, however, it does have a rather high idle. Who cares though, I now don't have an .049 screaming constantly.
I've just posted my testing Video at http://www.rcuvideos.com/item/XN434ZDLKFZCCB9J/received
it has slightly slow transition. I would like to see, how your AP carb. responses.
Old 04-22-2008, 07:18 AM
  #41  
Clay Walters
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Default RE: .o49 engines by cox


ORIGINAL: chevy43

There is a member here ( Skaliwag ) who is a Cox Guru and has a website with Cox engines and parts and lots of nice kits and hardware etc for 1/2a and small planes. He has been a big help to me. His website is: www.selecthobbies.com
Thanks! I've saved the link in my Favorites.

Clay
Old 04-22-2008, 07:34 PM
  #42  
bboykin
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Default RE: .o49 engines by cox

surprised how this post has energizes .049 engines hope it keeps up. do any of you know if any suppliers of glow head glowplug suppilers will be at SMALL this year. plan on attending for one day only live about 70 miles from there. hope to meet many of you enjoy reading your fun banters between many of you. hope some bring small planes to sell cheap.
Old 04-23-2008, 11:28 AM
  #43  
Yuu
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Default RE: .o49 engines by cox

Bugzidor... I put together a Surestart with an AP carb like your pictures in post #24. A $7 engine , with a $15 carb, and $23 worth of shipping!!!! All good things come to an end I put it somewhere until the weather cleared..... and it has "run away" !! I just can't find it anywhere, and today is sunny and 65*. Well, at least I know that it "runs"....... away, that is.
Old 04-23-2008, 07:47 PM
  #44  
cox .049
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Default RE: .o49 engines by cox

hey man just thought that i would let you know that ebay has a good but expensive selection of cox engines but www.coxmodels.com has em for 4.99 its the "sure start model"
Old 04-24-2008, 08:36 AM
  #45  
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Default RE: .o49 engines by cox


ORIGINAL: cox .049

<snip>......... www.coxmodels.com has em for 4.99 its the "sure start model"

I believe that's $6.99. Shipping for 1 or 10 is the same, so buy several.
Old 04-30-2008, 01:57 AM
  #46  
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Default RE: .o49 engines by cox

I have an old COX Dunebuggy, one of those free running ones with A Baby Bee Engine. The engine was trashed after installing a bigger Piston and Rod and Cylinder assembly. I think the piston snd cylinder were a .051. Well anyways in went really fast and super loud and would spin the tires like crazy until it would get traction and then the crankshaft broke and punched a hole in what was a reed valve and fuel tank. Does anyone know where I could get a crankshaft and a new tank with reed valve for the Baby Bee engine or even a new Baby Bee Engine?
Old 04-30-2008, 06:12 PM
  #47  
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Default RE: .o49 engines by cox

To check for rod slop, leave the engine in the plane, unscrew the liner and then take the piston in your hand and test for any slop. If there is more than a hairs' width of slop, then remove the engine and do your duty.
Old 06-23-2008, 08:55 PM
  #48  
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Default RE: .o49 engines by cox

This is my latest version carb. design for SS, which has more compact and relaible throttle responsive.
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Old 06-23-2008, 10:02 PM
  #49  
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Default RE: .o49 engines by cox

Very compact. Any video of the engine running?

I would like to know about that prop as well.

Robert
Old 06-25-2008, 12:23 AM
  #50  
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Default RE: .o49 engines by cox

The prop. is a vintage 'SCAMPER', I guess and I hope, I should have a video clip of this carb. available, soon.

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