There's a simple way to lift a platform a short distance:

  1. Identical discs are mounted on a frame at the four corners of a platform such that front pair of discs' axes of rotation are colinear, as are those of the back pair. The front and back axes are parallel.
  2. Each corner of the platform (at rest) is mounted to its disc at the same offset (and angle) from the disc's center.

When you lift one end of the platform, all of the discs have to turn identically, so the platform rises parallel to its at-rest position.

What is the formal name (e.g. crank-slider) of this mechanism?

I've been searching the Internet for parts and keep coming up with harrows and cultivators (farm equipment for plowing).

EDIT I'm building a rack to store eight snowmobiles in two rows - one above the other. I have maybe an inch to spare width-wise, so the solution has to be fairly thin, and the ceiling is already too low. Fortunately, the top row can sit below the tallest bits of the bottom row (the windshields and handlebar loops can project into the upper level without being run over). But the back halves of the upper decks need to lift 4-8" to allow sleds to move into the lower level. Discs are not only thin, but their rotation when the deck is fully lowered could be at an angle where raising the deck could combine pushing with lifting, rather than just pure lifting. When raised, their rotation would be just past 12o'clock so they are "locked" by gravity, and "unlocked" with a slight pull. (The decks would be unloaded when raised and lowered, else they would require power and vertical clearance that I don't have.)

I'd rather find a manufactured thin-disc-on-a-thin-bearing but I have no idea what it would be called.

Thanks for any help.

  • $\begingroup$ If you replace the rotating discs with hydraulic rams then that is how some oil field platforms are positioned. $\endgroup$ – Solar Mike Nov 18 '19 at 14:25

I suspect you may be looking for a "synchronized screw jack lift mechanism." Many sites exist when one searches using the above term. Some are not synchronized, allowing for tilt and translation and probably other movements, depending on the complexity.

A commercially oriented web page provided this image:

screw jack image

Laser cutters use this method of bed movement as do many 3D printers. There are variations in the mechanical actuators as well.

EDIT: With the previous information as a foundation, consider that 3D printers use lead screws (pronounced leed) with follower nuts that are usually disk shaped.

lead screw with follower

This is a common part in other engineering realms, specifically machine tools and you may be able to find a diameter appropriate to your application, capable of handling the loads involved.

Laser cutters have tables which use the same system:

laser cutter table lift mechanism

For lasers and 3D printers, GT class belts and gears are used to rotate the screws. GT belts are available in a wide variety of sizes from 3 mm to 10 mm and possibly wider. If necessary, you could use a drive belt from any power transmitting device (motorcycle?) as long as the gear matches and can be secured to the lift screws.

  • $\begingroup$ I came across this in my wanderings, but it would be inappropriate due to its size and complex operation. I've added an edit to my question to explain the constraints I have. Thanks. $\endgroup$ – pbyhistorian Nov 20 '19 at 1:41
  • $\begingroup$ I popped a few edits in that may expand your options. $\endgroup$ – fred_dot_u Nov 20 '19 at 21:20

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