[Shop-talk] Mower blade orientaaion relative to piston

[Jim Franklin]

These are both two blade props? I would love to know why it makes a difference. Especially that the two props get mounted differently.

jim

> On May 18, 2021, at 6:49 PM, Karl Vacek <stearman809 at gmail.com> wrote:
> 
> They reason I thought of it is that aircraft propellers are supposed to be phased in a certain way.
> 
> My Stearman has a 7 cylinder radial engine and when it has the Macaulay hollow steel prop on it the prop goes in line with the master rod of the engine (vertical) when cylinder 1 (top) is at TDC, but a wood prop is installed 90 degrees from that, or horizontally when 1 is at TDC.
> 
> The wood prop and it's steel hub are maybe 30 pounds lighter than Macauley.  It's not lore, it's in the Type Certificate.  And people have put props on wrong and it's smoother once they remount then properly.
> 
> On May 18, 2021 4:56:44 PM Jim Franklin <jamesf at groupwbench.org> wrote:
> 
>> I can't think of a reason it would matter. Also, I think if it did, they'd have keyed it.
>> 
>> jim
>> 
>>> On May 18, 2021, at 5:52 PM, Karl Vacek <stearman809 at gmail.com <mailto:stearman809 at gmail.com>> wrote:
>>> 
>>> Last time I sharpened my 21” walk-behind mower blade I thought of something that’s never occurred to me, after using the same brand of mower for 25 years..
>>>  
>>> On a Snapper, the blade can actually go on any way onto the square adapter keyed to the crankshaft.  The mounting point is square, no pins, no longer side, nothing.
>>>  
>>> One way would be aligned with the cylinder at TDC/BDC, and the other way would be across.  It’s been off many times and there’s no way to tell how it was mounted originally.  The manual is silent on this.
>>>  
>>> Power stroke shouldn’t matter, but maybe some dynamic issue one way or the other?
>>>  
>>> Thanks!
>>> Karl
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