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Author Topic: thread for Cox .020 crankshaft.  (Read 893 times)

Offline sleepy gomez

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thread for Cox .020 crankshaft.
« on: April 10, 2013, 08:35:39 PM »
Is a 5-40 or 5-48 the right crank shaft thread for the prop?
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Offline Tim Wescott

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Re: thread for Cox .020 crankshaft.
« Reply #1 on: April 10, 2013, 08:52:18 PM »
Cox 049 is 5-40.

#5 fine thread is 5-44; 5-48 doesn't exist in nature.

The thread on my PeeWee reed-valve 020 is 3-48 (well, at least it's .098" diameter, coarser than 2-56 and finer than 4-40 -- I'll take that to be 3-48).

What was LeRoy Cox thinking when he used those odd threads?
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Offline pat king

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Re: thread for Cox .020 crankshaft.
« Reply #2 on: April 11, 2013, 10:59:09 AM »
3-48 and 5-40 were very common at the time those engines were designed. I believe that a rationalization of screw sizes has virtually eliminated those sizes. 3-48 screws are perfect for mounting cox 1/2 A engines. 5-40 screws are great for .29- .35 size engine mounting.

Pat
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Offline dennis lipsett

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Re: thread for Cox .020 crankshaft.
« Reply #3 on: April 11, 2013, 01:32:06 PM »
3-48 are also the screw size for the Fox 049/07/10/15 engines also Gilbert and Wen Mac and most of the other early small engines. Perfect  products sold 3-48 mounting sets for years as I remember.

Dennis
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Offline Mike Lauerman

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Re: thread for Cox .020 crankshaft.
« Reply #4 on: April 11, 2013, 03:51:12 PM »
I still see them (5-40 and 3-48) as standards, in better hardware and fasteners' outlets.

What was supposed to have replaced them, please?  Metrics? 

No sarcasm intended here, I'm just alarmed. (stack this info on top of sequester, guns & roses, er, Magazines!  et al.)
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Offline Tim Wescott

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Re: thread for Cox .020 crankshaft.
« Reply #5 on: April 11, 2013, 04:15:10 PM »
Quote from: Mike Lauerman on April 11, 2013, 03:51:12 PM
I still see them (5-40 and 3-48) as standards, in better hardware and fasteners' outlets.

What was supposed to have replaced them, please?  Metrics? 

No sarcasm intended here, I'm just alarmed. (stack this info on top of sequester, guns & roses, er, Magazines!  et al.)

AFAIK they're just less popular than the even-numbered screws.
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The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

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