The Murphy Builders Site

I read here (http://www.melling.com/marine_rotation.htm) that a "Standard"
engine crank rotates counter-clockwise when viewed from the flywheel end

and

a "Reverse" engine is the opposite. Does anyone know if, generally,

helical

geared prop reduction units maintain the direction of rotation of the

engine

or does the reduction unit reverse the direction? I want to use a standard
three bladed prop, so I need to know if I should order a Standard direction
Chevy or a Reverse direction. I'm getting pretty close to completing the
basic airframe so I am getting that much closer to ordering an engine.

Mike
A Planetary gear reduction does NOT change the direction of the out put
shaft compared to input ( as is the case with a belt drive).
On the other hand a spur gear drive like the Marcotte DOES change the
rotation of input to output.

Another important factor is what the particular choice of drive does to the
position of the output shaft relative to input.
Planetary: no change; Belt: lots of change (7"??); Marcotte (internal spur)
a couple of inches above input.

I've been getting info from Marcotte on his drive and am working on a group
purchase which would get us 10% off. He has in stock now two models of his
450 (max hp) drive with chevy V8 adapter. One is 1.33: 1, the other is
1.96:1. List price is $3400 US and $3650
Are you interested?




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Umm.. It depends on how the planetary gear set is utilized. Lots of
planetary psru's out there do in fact reverse the rotation direction.
A single external gearset (helical or not) will also reverse it.
Ken

Peter Cowan/Lexi Cameron wrote:

I read here (http://www.melling.com/marine_rotation.htm) that a "Standard"
engine crank rotates counter-clockwise when viewed from the flywheel end

and

a "Reverse" engine is the opposite. Does anyone know if, generally,

helical

geared prop reduction units maintain the direction of rotation of the

engine

or does the reduction unit reverse the direction? I want to use a standard
three bladed prop, so I need to know if I should order a Standard direction
Chevy or a Reverse direction. I'm getting pretty close to completing the
basic airframe so I am getting that much closer to ordering an engine.

Mike
A Planetary gear reduction does NOT change the direction of the out put
shaft compared to input ( as is the case with a belt drive).
On the other hand a spur gear drive like the Marcotte DOES change the
rotation of input to output.

Another important factor is what the particular choice of drive does to the
position of the output shaft relative to input.
Planetary: no change; Belt: lots of change (7"??); Marcotte (internal spur)
a couple of inches above input.

I've been getting info from Marcotte on his drive and am working on a group
purchase which would get us 10% off. He has in stock now two models of his
450 (max hp) drive with chevy V8 adapter. One is 1.33: 1, the other is
1.96:1. List price is $3400 US and $3650
Are you interested?

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I suspect this is a typo but just to be clear, Marcotte uses an INTERNAL
gear set and it does NOT change the shaft rotation direction. I consider
this an important asset for a taildragger.
Ken

On the other hand a spur gear drive like the Marcotte DOES change the
rotation of input to output.

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I suspect this is a typo but just to be clear, Marcotte uses an INTERNAL
gear set and it does NOT change the shaft rotation direction. I consider
this an important asset for a taildragger.
Ken

On the other hand a spur gear drive like the Marcotte DOES change the
rotation of input to output.

Ken, thank you so much for pointing this out. I am really embarrassed that I
didn't think about this when it is so easy to sketch out what is happening
compared to planetary set-ups. What is particularly stupid in my case is
that I am currently running a double spur gear box wich also keeps the same
rotation and am planning to change it to Marcotte's because of Marcottes
same rotation (and better ratio). To me, the strong point is being able to
use "normal" props.
Peter.




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