Hydraulic Press design

[RocketRacing]

Since I know this is the place to find experts on everything, here goes. Smokey will probably know this

Why do hydraulic presses always seem to have the cylinder on the top, pressing down. Why would you not make a press with the cylinder on the bottom that presses upwards ? I am sure there is some fluid dynamics here or something obvious, so please edumacate me !

The discussion came up elsewhere and I figured I could find the answer here since Mr Google failed me.

[klhansen]

You could do it either way as far as the hydraulics are concerned. Force is Force.

Probably the reason most presses are built that way is because it gives a stable platform (not moving) on the bottom to set the workpiece on. Then you lower the ram onto the top where you can see it. You could design something with a movable lower frame, but it probably wouldn't be as stable, which when pressing with lots of force is very important. You sure as heck don't want the workpiece kicking out and hitting you in the gut.

[SteveRacer]

I think it's just easier to make and use. For smaller things you'd be constantly bending down to work around the floor level. Also, the "work" platform on mine just sits on large rods that fit into an array of holes on the sides. Gravity keeps it in place. It would be harder to "hang" this arrangement if you wanted to "press up". The hydraulic bits would have to be on the floor if you wanted a reasonable working height range.

And lastly, it's probably better to shoot things toward the floor when you're pressing out old bearings or races or shafts out of gears. Sometimes when they finally let go, they really pop hard -- and it's probably better to shoot it down at the floor than have a projectile rocketing toward the ceiling.

Perhaps it's just the way it is and nobody has challenged the paradigm. Why do motorcycles all pretty much have the same layout, with the gas tank between your knees and on top of the engine? (Although the Harley V-rod "tank" is actually air filters and intake, but it's still made to LOOK like a fuel tank.)

I suppose people expect things to look and act a certain way, and if they don't -- they better be much superior than the status quo or they won't sell no matter what. It's a novel idea, but I can't see an advantage of an upward-pressing hydraulic press.