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Please help me understand this (prop mount)

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So in studying 2 stroke engine design I found out that most paramotors are not direct-drive but rely on a reduction pulley and centrifugal clutch. 

But in studying pictures, I discovered the stem that the entire propeller/secondary assembly rides on... Is just a mere tab molded into the crankcase. I couldn;t believe my eyes when I saw that... Hundreds of pounds of thrust, prop strikes, axial load, radial load, it's literally moving the entire setup... And it's just a small metal tab. 

Am I missing something? 

I circled the tab in black in the picture. SO this tab supports the weight and thrust of the prop entirely? If it were me there would be a through-shaft supported on the other side as a minimum, and even that would be frighteningly under engineered to me... But one tab?! I mean, obviously props aren't falling out of the sky, but... Just the one tab? I really need to understand this...

Thank you!


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Yep, you are correct. Engineering is a compromise, and the compromise here is strength against weight.

Light as possible but strong enough to take normal loads. Yes if you whack a prop on the ground it may break, but that's not what its designed for...

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1 hour ago, Tundrawolf said:

even that would be frighteningly under engineered to me

Its sometimes useful to visualise a physical attempt to make it fail.
Imagine attempting to snap that "tab" off by hand... you could easily apply more force with your bare hands than the ideal static load that the "tab" is required to take (<60kg thrust looking at that motor)
I could easily apply more than 60kg and I am 99% sure I could not snap it off by hand as hard as I might try.

As others have said, these things may fail under "unusual" circumstances like a prop strike or a large harmonic vibration (damaged prop) both of which could potentially exceed 3 X the expected maximum load by a huge amount.

Now imagine hanging 180kg (3X max load) from that "tab" and place a £100 bet.... will it fail or not :) 
My "guess" would be "no" on the "assumption" that the person who designed the thing, designed it with the bear minimum of 3 X the ideal static load AND a typical engineer is more likely to add a touch of margin to ease his doubts than scrimp to save weight.

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