Simple Bearing Question 2

[dsjon10]

I am designing a swing test fixture with little prior bearing experience. My plan is to use some off the shelf 4 bolt flange mounted bearings. The swing stand is a box shape and the swing itself is a u shape. Each side of the swing will have a 3/4" shaft that will go to bearing. Due to payload constraints, I am not able to have 1 shaft run across the structure to engage both bearings. The payload will be centered about the swing and will be approximately 75 lbs. The swing spans about 26" in length b/w bearings. The bearings selected have 1 rolling element in the assembly. I have an idea to align the system using a straight rod to span the system as an alignment tool and some alignment blocks to hold the swing in place.

Question: Will this design work with 1 bearing (2 total) attached to the outside of the stand or do I need 2 bearings per side (4 total) to distribute the load of the swing? (See attached pic for description)

 

[BrianE22]

There's nothing inherently wrong with how you are doing it. If the flange bearings are spherical they will compensate for misalignment. The down side to sphericals is that your swing may droop a bit.

 

[caoimhin1]

One bearing per side will be fine, the load sounds very low in relation to what a 3/4" flange unit like an SF3/4 will take. Four bearings will complicate matters, alignement over four bearings will be difficult.

 

[MikeHalloran]

Using one bearing per side requires that the swing to stub shaft joint carry some moment, as will the swing itself. It looks like the swing will react to the moment by deforming. Whether it deforms enough to be a problem for the application or the bearing is not computable from information we have.

I personally would probably use two bearings per side, one on the outside face of the stand, and one on the inside face of the stand, secured by the same bolts. The paired bearings can be aligned nicely with the stub shaft inserted before the mounting bolts are tightened.

Another alternative is the stub axle assemblies sold for small trailers, in which case the stand would be drilled with a wheel bolt pattern, and the swing would be analogous to the trailer frame or axle tube.



Mike Halloran
Pembroke Pines, FL, USA

 

[Tmoose]

If the 3/4 inch stubs are not co-linear the ball bearings will bind, forcing the spherical OD outer races to "be the bearings." Some are mighty tight fit in the flange housings.

 

[diskullman]

You could probably use a bearing designed for HVAC use. The spherical OD of the bearing is looser in the housing.

Russell Giuliano

 

[dsjon10]

I appreciate the responses. I'm going to take this under consideration and decided how to go.