APC props OK for gas?

So how you going to get that prop on that cox .049? The OP, Ook, already said it won't work. The holes are too big. Maybe he should buy an engine to fit the prop? I believe........... you should go on the wagon. mk
Reply to
MJKolodziej
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"Facts" are very slippery things, and tend to be quite subjective. None of us have facts. We only have beliefs and opinions. A fact is only a fact so long as we believe it is.
I could make a bushing that would adapt it, but then I'd have a severe balance problem so I'd have to balance it. Way too much trouble :P
Reply to
Ook
I was wrong, it is a free flight prop as TNP says(he's till an asshole). Your right, that prop won't work on that eng. I just bought 5 NIP cox 049s and I have a few props laying around. As the thread mentions, APC ar good and sharp. mk (wondering what 049 has a 1/4" shaft?) Anyone own a Texaco?
Reply to
MJKolodziej
On Sun, 11 Mar 2007 20:55:29 GMT, "MJKolodziej" wrote in :
Googling shows that folks are using homemade brash bushings to fit the prop.
Bushings are also available for purchase to adapt the APC props to the Cox prop shaft.
Marty
Reply to
Martin X. Moleski, SJ
Hmm...ok, inventory time:
Zinger 6x3 (2) Thimble drone black flexible 6x3 (1) Thimble drone black flexible 5x4 (1) Thimble drone hard grey 6x3 (1) Thimble drone hard grey 5x3 (1) Thimble drone hard grey 5x4 (2) Thimble drone hard grey "performance" square ends 5x3 (1) Master Airscrew 10x6 (8) Master Airscrew 10x5 (2)
I'm not really sure where these came from, I used to have three times as much, but an unpleasnt divorce about 14 years ago caused most of my stuff to vanish :(
I've never used a 5x4 or a 5x3. Based on what others here have said, I'm not sure a standard .049 can benefit from a 5x3. I've used a 5.25x3 on a Black Widow, and it flat screamed. VERY noticeble improvement over a 6x3.
Reply to
Ook
A fact is that that prop is listed on APC's web site as an 049 sport prop.
Its not subject to belief, unless you believe I control their web site or can mysteriously influence your mind.
Don't get all religous weasel on me. Admit that you are plain wrong.
Why on earth would you have a balance problem if you bush the shaft properly?
Reply to
The Natural Philosopher
The fact is that virtually identical props of slightly different sizes are clearly marked as electric only, not to be used with gas engines. Makes one go "hmmmm...".
Wrong about what?
Because in the real world, proper doesn't happen and no matter how carefull you are the prop will still be somewhat out of balance. Because the manufacturer themselves tell you to balance the prop before using.
Reply to
Ook
Ook,
A couple of things:
(1) APC molds large holes in the hub of their props, and by their own admission does a piss-poor job post-drilling the through-hole. As a rule, you should center APC props with a bushing fit to the molded hole in the rear of the hub. The molded hole in the rear of the hub is accurately on center, but don't trust the drilled through-holes for anything but hanging your props on a pegboard.
They list a 5.7-3 on their website -
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call it a 1/2A prop and I own a few of them and use them as 1/2A glow props. Oddly they don't look exactly like the props in your picture, which really do look more like electric props. Normally, they supply bushings with their electric props. So something is amiss here - you are referring to 5.7-3 props which they only list as glow props, yet show a picture of what looks more like an e-prop, not a slow flier electric prop but a regular e-prop. So I'm confused, maybe they have a 5.7-3 e prop now, I dunno. I have some 5.7-3's somewhere but couldn't put my fingers on one just now, however I just ran downstairs and did find a 5.5-2 APC 1/2A prop. For reference, the through-drilled hole is 3/16" (0.188") in diameter. Coxes use a 5-40 prop screw, which typically measures 0.123-0.125" in major diameter. My VA's on the other hand use an M3 screw which measures 0.005-0.116" OD. In either case you need a bushing.
(2) Standard .049's can indeed benefit from 5-3 props but that depends so much on the application. 5-3 Cox props are a great prop for many applications, yes the engines "scream" on them, but honestly they are running at a very comfortable and efficient rpm on these props. They are small engines and make the best horsepower at higher rpms, and the 5-3 is by no means too small a load. Most reed valve Coxes turn a 5-3 in the ballpark of 17k, some up to 18k or so (I have a Black Widow that exceeds 18k on a 5-3), and that is child's play for them. TeeDees turn even higher. Many aircraft on Cox .049's fly better fitted with 5-3 versus 6-3 props. The reverse is also true - it depends entirely on the airframe. Smaller and clean - 5-3, larger and draggier, 6-3, as a very general rule.
Your 6-3 and 5-3 grey ("competition") props are the number one and two choices but not necessarily in that order depending on the aircraft. They are excellent quality props, they are one of the things Cox did right. If you use the APC 5.7-3's, try to do a good job centering them via a rigid and accurately made bushing.
MJD
Reply to
mjd
Those look like props for IC (glow) engines to me. What engine are they intended for, can I ask ?
Reply to
Boo
I forgot to say that there are other sized bushings available for APC props, but I don't know if the electric bushings will fit the IC props.
Reply to
Boo
If you can get access to a lathe (or have a friend who has one ?) then it would be the simplest thing to machine the outside diameter of a bit of ally bar then drill/ream the central hole at the same setting. This would guarantee a good result in terms of concentricity even on an old and tired lathe.
Hth,
Reply to
Boo

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