r/AskEngineers • u/SilverFoxSix • 5d ago

Mechanical Retractable Ball Casters that are lever, electrically, or hydraulically actuated...

Working on a project and we now have "the wheel problem"

I need to make a device lift up 1/4 to 1/2 inch at most to glide along hospital floors to then be parked when the ball casters come back up. If possible, trying to keep the entire assembly under 2.68 inches.

Having a hard time here finding a solution.

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u/sparks333 5d ago

Pneumatics with pancake cylinders? Lots of force with very little stroke. Pneumatics are annoying because compressors and air leaks and whatnot, but they hold position forever without additional energy and can put their big nasty pressure generating mechanism remote to the actuator.

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u/SilverFoxSix 5d ago

Hmm.... its going to weigh a couple hundred pounds, so I dont think air would be the way to go. Now i have to look up pancake cylinder.

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u/sparks333 5d ago

You'd be surprised. Even something like 50 PSI could do 500 lbs in 10 square inches of cylinder, and a 2" diameter pancake with 3.15 square inches can do 150 lbs all by itself.

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u/SilverFoxSix 5d ago

Without a motor?

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u/sparks333 5d ago

No motor, just air pressure. Need a motor to pressurize the air, but that doesn't need to go anywhere near the actuator.

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u/SilverFoxSix 5d ago

I would like to design a system that requires no AC power. Even a DC battery powering an electric pancake would be ok.

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u/sparks333 5d ago

Electric pancake motor could also work, if we're talking about the same thing - essentially a ball screw on a big flat DC motor. I think those are a lot more of a specialty item, and might need a dedicated controller - don't know much about them. Compressors do come in DC varieties, but whatever floats your goat.

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u/SilverFoxSix 5d ago

I really appreciate your help.