- #1

OJT

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Hi all,I would like to know how to calculate the force required to lift a flap (or drawbridge if you proffer) of known weight that is on a pivot and where the pull chain (let’s say it’s a chain) connects to the flap at a known distance from the pivot.I’d also like to be able to calculate the effective weight it would exert when resting at it’s top (denoted by a blue dot on the drawing)I’m no engineer or mathematicians but I do have CAD softwear so can measure angles (as shown on the attached drawing) so the simplest methods - i.e. without any trigonometry if possible - would be great! I have been unable to find similar explanations online with equations that the person un-versed in long equations can follow that easily(!) – although am happy to learn if there is no simple solution!

So the flap / drawbridge:

- Is 3.2m long

- Has a weight of 25kg.

- Pivots around the point marked ‘

- The ‘chain’ connects to the flap at a distance of 2m from the pivot / or 1.2m from the free end

- All (I hope) relevant angles are shown on the drawing.The problems to solve:

Any help or pointers will be fantastic so thanks in advance,

Oliver

So the flap / drawbridge:

- Is 3.2m long

- Has a weight of 25kg.

- Pivots around the point marked ‘

*p*’- The ‘chain’ connects to the flap at a distance of 2m from the pivot / or 1.2m from the free end

- All (I hope) relevant angles are shown on the drawing.The problems to solve:

- How can you calculate the force required to lift the flap from horizontal to 45 degrees (A) and from 45 degrees to 12 degrees (B)?
- How would you calculate the weight exerted on the resting point at the top of the flap (as denoted by the blue dot). 'C' denotes the direction I think this force would be acting in.

Any help or pointers will be fantastic so thanks in advance,

Oliver