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Lifting Machine (Via Suction)

by jnlbctln
Tags: lifting, machine, suction
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Apr7-12, 08:36 AM
P: 22
Good day!

Just wanna ask the principle and mechanism behind that Suction Lifter (did I mention the name correctly, don't know the correct term e).

I have watched that video regarding the Construction of S.M.A.R.T Tunnel in Malaysia. They used "hydraulic suction lifter" to install (lift) those curve concrete side by side and top and bottom of the tunnel.

I know the principle behind the SUCTION CUP. And I'm thinking right now if they have the same mechanism. You know, I'm just amazed how this huge amount of weight being lifted.

You might probably answer "YES, THEY HAVE SAME PRINCIPLE".

Here's what I think. Isn't it that the mechanism of the simple suction cup is the difference between the air pressure inside and outside the cup. The force of pressure outside the cup is greater compare to the inside pressure force. Hence, it pushes the cup towards the glass. (<----Would you please verify my previous statement, im not sure with that though :) )

What about the "lifter" ? If we make a free-body diagram of a "concrete" or "glass" for example being lifted by a suction cup or any suction device.

These are the forces (i think)
---Weight acts downward
---Suction force acts upward? (This must be the case to obtain equilibrium)

But as i have said above, "pressure force" acts towards the glass (or concrete), hence, downward. How can this be? I know there's a misconception in my part. Please help me. Thanks a lot!

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