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Methods of exerting forces and displacements introduction to the design of „basic machine”

Methods of exerting forces and displacements introduction to the design of „basic machine”. Drawings taken from:. Levers. „Give me point of support and I will lift the Earth” Galileo Is this true?. Power screws (screw gears) .

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Methods of exerting forces and displacements introduction to the design of „basic machine”

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  1. Methods of exerting forces and displacementsintroduction to the design of „basic machine”

  2. Drawings taken from: Levers „Give me point of support and I will lift the Earth”Galileo Is this true?

  3. Power screws (screw gears) Screw with a nut is a basic machine able to achieve a large force in the screw by multiplying the force applied to the nut Torque that has to be applied to the nut (or screw head) in order to obtain force P On the other side: Mn = Fhand x Lwrench

  4. Power screws Various configuration of mechanisms Compound and differential screws (Hunter’s)

  5. Mechanizmy śrubowe Evaluating torque and force

  6. Design of a power screw Selection of thread 1. Thread type – trapezoidal thread (Acme) or butress threadlub niesymetr. 2. Minor diameter - destruction of the bolt shank Screw under tension - break Screw under compression - exceeding allowable stress - flexural buckling (wyboczenie) Material selection + limited specific load: Cast iron 8-30 MPa brass 8-15 MPa bronze 10-30 MPa Aluminium bronze 10-40 MPa - Destruction of the thread seizure of the surfaces excessive wear 3. Thread pitch – standard values selected to obtain required mechanical advantage and self-locking properties. A possibility to use differential and summing mech.

  7. Rope mechanisms Pulley block (compound pulleys)

  8. Hydraulic devices

  9. Rack and pinion mechanism

  10. Crank mechanism Cam mechanisms Rack and pinion mechanism Transformation of rotational motion into linear motion crankshaft Push rodCam follower

  11. Belt transmision Transmissions Gear transmision

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