See work up..

Dimensions

Weight = 150kg

Density (steel) = 8000kg/m3

Volume = 0.018m3

h=1m

r= 0.075m

A= 0.018m2

movement = 10m

Volume air = 0.18m3

Forces

F=ma

Downwards force = 1470 N

Maximum upwards force

If pressure above is 0

Pressure below weight = 100kPa

Force acting on weight = 100000*0.018 = 1800 N

Maximum Pressure required for return = 18kPa

Acceleration and times

Downstroke

a= 9.8m/s2

t= 1.43s

Upstroke

amax = 2.2m/s2

tmin=3s

Vacuum Calcs

cycle time of 5s (using vacuum pot to ensure vacuum is instantaneous)

so 0.18m3 of air in 5 secs

minimum increase in pressure.. say 1kPa, If vacuum pot is at 1 torr. (133pa) then 0.18m3 of atmospheric pressure air would occupy 555.5M3 to give a rise of 1kPa... This require a vacuum pump that can do 111.1M3/sec on outline calc (555.5/5)

Using S=V/t x ln(Po/Pi) = 238 M3/s (V= 555.5, t= 5secs , Po= 1133Pa, Pi=133Pa)

Using Power = S x dP/mech eff (typically 0.85)

= 130kW or 280kW

Friction force with PTFE will still be 60N with the differential force on this example being 330N, this is fairly significant.. that does not take into account the friction of the air movements etc.

Work up may be wrong only had 15mins to write it (10 mins was drawing a picture that was too large to be posted

)

Point out changes please.. As the power is large.

Something forgotten is the increase volume of air at lower pressures.. I have tried to take this into account