Hydraulic Press: Track Efficiency and Losses

Distinguish energy loss from the ideal force ratio.

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Useful-work efficiency = useful output work / input work. In a completed cycle with no net stored-energy change, input work equals useful output plus energy transferred elsewhere. Losses do not make energy vanish. Use diagrams and calculations only; never build or operate a press for this activity.

Worked example

A fictional cycle takes 60 J and delivers 45 J of useful work. Efficiency is 45/60 = 75%, and 15 J goes to other energy transfers.

An energy bar shows 60 joules of input split into 45 joules of useful output and 15 joules of other energy transfers. Useful output is 75 percent of input; net storage change is zero.

Would you believe it?

Many powered hydraulic machines use a motor-driven pump to supply energy. A large output force is not free energy; force and travel must both be counted.

OpenStax: hydraulic work and energy

Question 1 What is the efficiency of the example? 75% 125% 15%

Question 2 How much energy is not useful output in this completed cycle? 105 J 45 J 15 J

Question 3 At unchanged 75% efficiency, what input gives 90 J useful output? 165 J 120 J 67.5 J

Question 4 With input power 80 W and 75% efficiency, useful power is what? 60 W 20 W 106.7 W

Question 5 Can force ratio alone establish overall efficiency? Yes, always Yes, if the machine is painted blue No, travel or work is also needed

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