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I am designing a system wherein an assembly has to be moved up and down( 4 inches) at regular intervals ( every 5 mins) using a Linear Actuator. I wanted constrain the DOF and ensure that the entire assembly moves straight up and down( 1-2 degree misalignment is acceptable). The entire assembly is a cantilever and Hence, I wanted to have some bearings to restrict the moment and ensure straight vertical motion.The weight of the entire assembly is about 50lb and the distance from the support frame (for cantilever) is about 7 inches.

Hence, is it okie to have sleeve bearings(Red color in picture below) (Ultra-Low-Friction Dry-Running Flanged Sleeve Bearings from McMaster: http://www.mcmaster.com/#standard-sleeve-bearings/=11vp8eo ) which serves as a guide for the motion

enter image description here

In the above Image, the fixed frame is rigid and the moving assembly( in light pink) slides on the sleeve bearing carriages attached to the fixed frame( in dark pink color)using the guide block attached to the moving assembly( in green). However, since it is a cantilever I want to provide additional support at the other end .Cost & compactness is a factor for me in this design , so are normal sleeve bearings( in RED color- ultralow friction ) good for support the assembly at the other end .

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  • $\begingroup$ I can't get my head around the mechanism :/ do you have a picture of something similar? I'm using a lot of linear motion mechanisms atm so I'm very interested $\endgroup$ – CL22 May 7 '16 at 20:30
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I'm thinking of metal drawer tracks or slides, like those for kitchen drawers. Lightweight, easy to instal, you could create sort of cage so that your construction moves along the tracks, low friction, always horizontal, never stuck.

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I'm not sure that the sleeve bearings are adding very much to that design. In a cantilever the most important load is usually the bending moment at the supported end and they don't do really anything to support that.

50lb cantilevered to 7 inches isn't by any means unmanageable and If I were you I would just design the carriage to take all of the load. Here one possibility is to use similar sleeve bearings in a pair of vertical shafts (2 per shaft) which should effectively constrain it in all directions apart from vertical.

An alternative way to do this would be to have nylon wheel running in channel shaped rails

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