Need advice on best way to achieve this linear motion.

[Kosh]

I'm wanting motorize my adjustable "go-bar" deck. Basically, two adjustable horizontal surfaces with flexible rods between them which allow me to apply clamping pressure anywhere on a surface.

I'd love to have it as a cabinet with a top that "raises up" to form the clamping surfaces in the void under the top, then goes back down to be used as a regular workbench when not in use.

See pictures of "down" and "up" positions:

the four support columns can be round or square, doesn't really matter. The space just needs to be clear underneath. I just want a simple switch "up" and "down", and have it stay in the position when
the switch is in neutral.

My thoughts are:

1) some sort of ball screw setup where the ball screws are the actual column? Would need to mount the motors on the top then?
2) simple rack and pinion with a motor on each column?
3) is there a way to do with the just one motor and gears/chain driving all four shafts?
4) can it be done with just two motors or one if good sliders used on the others?

Thanks.





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[Jim Dawson]

There are many ways to approach this design. One way would be an Acme threaded rod at each corner with a chain drive and a single motor. Ball screws would not be the best, they are not self holding like an Acme thread is. From a cost standpoint, any type of screw lift might be the most expensive, and certainly more difficult to build. A rack & pinion would not be a good choice for this application.

The simplest and least cost way would be to lift it with a foot operated hydraulic jack, just have the jack lift a central plate that is attached to all four columns. This is a common method for lift tables. If there is a reason you need it to be powered, then an air operated hydraulic jack would be my choice, or it could be electrically operated with a small hydraulic pump.

[louieatienza]

Guitar-making?!

If it were me, the four legs would be internally connected with another platform, and I'd use a couple scissor jack assemblies to raise/lower the assembly. Would be a lot simpler and cheaper than making 4 rotating nut mechanisms synched together with chain or timing belt.

Gear racks on all 4 posts with two jack shafts running the pinions, connected together with timing belt and pulley, is another idea.

[Kosh]

Guitar-making?!

If it were me, the four legs would be internally connected with another platform, and I'd use a couple scissor jack assemblies to raise/lower the assembly. Would be a lot simpler and cheaper than making 4 rotating nut mechanisms synched together with chain or timing belt.

Gear racks on all 4 posts with two jack shafts running the pinions, connected together with timing belt and pulley, is another idea.

True. I considered that, but then I miss out on storage below!

[dharmic]

If precision isn't a huge deal I'd even look at four lengths of course allthread with each supported by a toothed pulley (with the matching thread in the middle so they spin, the allthread moves) supported by a pair of tapered bearings to allow load lifting and lowering/clamping. Run a belt around all four with the drive motor on a swivelling plate that can be locked in place to tension the belt and you're ready to rock and roll

[hanermo]

Whats the load / speed / accuracy required ?

I would suggest use of a centralized lift point like a flat steel plate, driven by one mechanism.
A car scissor jack for 30$ might be a good, fast, cheap, strong mechanism, that comes out for storage.

[louieatienza]

Instead of legs, use or make them out of pneumatic cylinders