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Offset Blocks - How do they work?


Steve Loy
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Merry Christmas folks.

I've been scouring the interwebs and I cant seem to find a concise explanation of the physics behind how hang point offset blocks work.

I've just had my new Paramotor frame delivered (Evo Rebel 2) and it came pre-installed with offset blocks appropriate to my engine (Direct drive Minari, prop turns anticlockwise when viewed from behind)

Take the attached photo of my new frame for reference... from behind...  note the position of the silver offset blocks on the swing arms...

Can anyone explain the physics behind how these blocks help to prevent torque steer?

1334279470_image013214.thumb.jpeg.ea3e6ef52a921189624a2b5df42d7b5c.jpeg

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Hi Steve, well this is a laugh, I was wondering how these work as well when I bought a motor with them on.

As I didn't understand it at the time I didn't realise that the blocks were actually fitted on the wrong side. I flew it for quite a number of flights before understanding dawned, then I swapped them to the correct side.

It is actually quite simple how they work. Think of when you weight shift in the harness to instigate a turn, the centre of mass is moved to one side or the other and the wing is angled slightly in the horizontal plane, creating a turning moment.

Although the offset distance of the blocks doesn't seem like much, they offset the centre of mass enough to counteract the torque turning moment.

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That makes sense, however it raises a question...

On my new frame, the blocks are placed left... as in the picture... which places the wing slightly left overhead... wouldn't this put my centre of gravity to the right of the wing... thus resulting in a right turn, and NOT countering the right-torque steer of my engine?

They re-assured me that they had set them correctly for my engine... so are there other forces at play here? or have they made a mistake and set them wrong for my engine?

 

Edit - This video seems to suggest the same thing, in order to offset a right turn via torque... you shift the carabiners right... which puts the centre of gravity to the left of the wing.

 

https://youtu.be/OIfnIolZV_A?t=136

 

Edited by Steve Loy
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  • 1 month later...

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