Quote:
Originally Posted by Chris Fultz
A 2.5" cylinder from Bimba has a 0.625 pushrod. Assuming you will retract the rod to pull your robot up, we need to subtract that area to determine the capability.
2.5" diameter, less the .625 rod, gives an area of 4.6 square inches. 24 inch length = 110 cubic inches of volume. This cylinder has 275 pounds of force to lift your robot.
2" diameter, less the .625 rod, gives an area of 2.83 square inches. 24 inch length = 68 cubic inches of volume. This cylinder has 170 pounds of force to lift your robot.
The 2.5" cylinder has 160% of the volume of the 2" cylinder, so it will take about 160% of the time, assuming you have the available volume of stored air.
If your robot weights 120 pounds, +12 for battery and 15 for bumpers, you are close to 150 pounds that you need to lift. Remember that you will also have some friction to overcome if the robot is sliding up the front of the tower.
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I don't think a 2-1/2" cylinder would require 160% more time to fill since it it only requires 1/160% as much PSI to provide the same force.
I think this is interesting mathematically remembering the equation pv=nrt. Assuming that temperature remains constant, the two cylinders are operating in a vacuum, and they have the same stoke length, the same amount of air in one bore sized cylinder will provide the same amount of force that a cylinder with a different bore size. Let me explain,
F=force
A=area of piston end
V=volume of cylinder
P=pressure
N=amount of Air
S=stroke
PV=N
F=PA
V=SA
Therefore
A=F/P
V=SF/P
Multiply that by N=PV
NV=PVSF/P
N=SF
N/S=F
So under ideal conditions, the same amount of air in any bore sized cylinder (with the same stroke length) would equal the same force. The question then is what would fill to the required lifting pressure faster, the 2-1/2" bore or 2" bore? Wouldn't the the 2-1/2 fill faster because of the increased pressure difference? Since the air pressure inside the 2-1/2" would be lower under the load wouldn't it have a faster fill rate because the difference between the pressure in the cylinder and the 60psi storage would be greater? I will do some more calculations to try to figure that one out.