Parallel horizontal shims that slide frictionless on vertical rods 1

[phill86518]

Horizontal shims that slide on vertical rods:

I have 10 long aluminum horizontal shims (nearly 8'') that have two identical holes (diameter nearly 0.5") on one end. Two vertical rods pass through each of these holes such that the 10 shims are stacked. These shims are required to be perfectly parallel to each and to the ground but currently, because of the suspension from one end, the shims' far ends tend to collapse on each other creating a slant.

I need a solution that not only solves this but ensures that the shims can slide up and down the rods (almost) frictionless perfectly aligned and parallel to one another. I also cannot use any grease.

Would appreciate any help!

 

[Stick.]

Can you provide a sketch of this arrangement with some dimensions? Preferably one that shows the ideal situation, and another that exaggerates the "shim's far ends" collapsing on each other effect.

Also, you're going to need to define how much deviation from perfect is acceptable.

 

[dtimberlake]

Among the many other hitherto unidentified details things the holes in the shims are going to need some careful detailing lest their square edges become locking devices.

https://m.media-amazon.com/images/I/71anrnKKStL._AC_SX522_.jpg

https://www.harborfreight.com/media/catalog/product/cache/c7f358f04aec81e7c5e0be4c56edf041/i/m/image_14817.jpg?auto=webp&width=1200&height=1200&canvas=1200,1200&fit=bounds

https://img4.dhresource.com/webp/m/f3/albu/jc/s/12/2dea1ead-b8c3-4946-8a62-ba040a1361e4.jpg

 

[dgeesaman]

Among the many other hitherto unidentified details things the holes in the shims are going to need some careful detailing lest their square edges become locking devices.

https://m.media-amazon.com/images/I/71anrnKKStL._AC_SX522_.jpg

https://www.harborfreight.com/media/catalog/product/cache/c7f358f04aec81e7c5e0be4c56edf041/i/m/image_14817.jpg?auto=webp&width=1200&height=1200&canvas=1200,1200&fit=bounds

https://img4.dhresource.com/webp/m/f3/albu/jc/s/12/2dea1ead-b8c3-4946-8a62-ba040a1361e4.jpg

Yeah my first thought is that this system is practically designed to lock / grip the rods.

So how are you going to address the requirement of keeping the shim stack parallel to ground?

I would consider using a tighter clearance hole, maybe located in the middle of the stack, that has a dowel pin in the middle and increase the clearance on the 1/2" holes as much as possible. Don't let the shims touch the rods.

 

[phill86518]

There are two sets of shims - here is the image of the first one. They are tilting to the right in the image... they need to slide up and down the rods perfectly horizontally... right now there are bushings/spacers. The shims may have to be redesigned such that they are thicker on the left to counteract the weight on the right? Any ideas or anyone with SolidWorks experience would be a tremendous help. Thanks.

 

[dvd]

Unless everything is perfect, this will be difficult. Your rods need to be perfectly parallel and spaced at exactly the hole spacing, otherwise something, like your perfectly horizontal motion, will not work out. Can you guide along just one rod? A lot of precision fixtures use one round pin and one diamond shaped pin - look into that type of operating philosophy.

 

[phill86518]

The rods are dead centered and steady - so that is not the issue. Besides the design change, bearings could be used to keep the smooth glide.
Notwithstanding above, if we imagined the system at 90 degrees, there might be a few good ideas?

 

[phill86518]

Can you provide a sketch of this arrangement with some dimensions? Preferably one that shows the ideal situation, and another that exaggerates the "shim's far ends" collapsing on each other effect.

Also, you're going to need to define how much deviation from perfect is acceptable.

Please see the image I posted in the thread.