Will this orientation of cylinder/slides have excessive wear?

[MechvsManu]

This is a lifter I have designed to lift 1000lbs. This is one side and is mirrored on the other side. The cylinder is capable of 700lbs.
Will the cylinder being off and not centered between the linear shafts/bearings have an issue with lifting?

Also would it help if I did 2 cylinders in the location of the red arrows over one larger cylinder in the center? Or would that cause a binding issue?
I'm clamping against an upper frame so I don't need the cylinders to lift exactly simultaneously.

I don't have space to mount the cylinder under and centered due to clearance issues.

 

[MechvsManu]

The whole thing gets lifted up and rotated upside down before returning to this position and lowering. That's all done externally by a car lift that's been modified.
We absolutely need a failsafe. I was playing with a spring activated air release cylinder to slide a pin into a opening when fully clamped. Thanks for the input.

 

[MechvsManu]

I wouldn't say I'm trying to reinvent the forklift. I only have 6" of stroke, 12" of clearance under the box and a $5k budget. Hardware looks to be $3k and the steel and plates shouldn't add up to $2k. We have lots of air in the area so I'd prefer to avoid hydraulics.
If there's an off the shelf solution I'd be open to it.

 

[dvd]

I have worked on somewhat similar rollover devices on a larger scale. Pinning the clamp mechanism is a reasonable approach. You might just make manually insertable clamping pins and interlock them with controls so that the machine will not operate without pins in proper locations.

$5K total!? good luck with that. You have a lot of things to accomplish, including pneumatics and controls. What sort of bearing arrangement does this pivot on? What provides the pivoting motion?

 

[MechvsManu]

Manually pinning with an interlock is a good idea. I might use that.
$5k for this clamp mechanism shown and the pneumatic cylinders & valve. The car lift will take care of the lifting and the rotation is already there with a 1050:1 gearbox tied to a VFD. Manual buttons for cw/ccw rotation.
I just need to provide the clamping mechanism and attach it to the spline shaft that already exists (and an idler on the opposite side).

 

[MintJulep]

What prevents the box from sliding out at 90 degrees?

Anti-gravity? Friction?

 

[MechvsManu]

Eh... the clamping force of the pneumatic cylinders. Or am I missing something?
1000lbs load with approx 1800lbs of clamping force.

 

[Stick.]

1800lbs of clamping force for a 1000lb load is probably too light. For reference, ASME BTH-1, Design of Below-the-Hook Lifting Devices* requires that the friction force developed by a clamp type lifter to be at least twice the load being lifted. That would require you to reliably develop a coefficient of friction of roughly 1.1, which probably isn't gonna happen. You also need to consider failure modes of the pneumatics and how that will affect clamping ability. You don't want a broken air hose to cause the load to drop. Crushing of the load also could become a factor, both for safety and product quality reasons.

*Note: I'm not sure if this is technically the correct standard to use, but it's at least a good place to start for getting a sense of what's required for safely lifting loads.

 

[MechvsManu]

Thanks for the info. I'll look into this before finalizing the design.