How to prevent rod/shaft from sliding

Question

I'm new to mechanical engineering and have a question regarding something that I design using fusion 360.

Here I have 2 wooden rollers that are mounted on 2 side plates thru holes. I'm planning to use sprockets and chain connected to these rods/shafts outside the side plates and a crank handle to power them. My questions are

1. And how do I make sure that these rods wouldn't slide horizontally when the crank handle is rotated that would misalign the sprockets and chain.

2. Since the thickness of the plate is only 5mm, I don't know if I should use a bearing to hold these rods or the hole is enough or any other thing(I'm not familiar with names of these parts to be used).

Answer 1

Since the thickness of the plate is only 5mm, I don't know if I should use a bearing to hold these rods or the hole is enough or any other thing(I'm not familiar with names of these parts to be used).

Yes, absolutely use a bearings or bushings. You want those bearings or bushings. Thickness of the material it is riding in is irrelevant as long as it sits square.

You do not want the outer race of the bearing to rotate relative to whatever it is mounted in, nor do you want the shaft to rotate against the inner race of the ball bearing. That defeats the purpose of the bearing. The goal is to have relative motion only occur between the balls and races of the bearing.

There are at least a few ways to do this:

1. Press fit (works for both inner race and outer race)
2. Slip fit with set screws (only works for the shaft and inner race)
3. Slip fit with adhesive such as green threadlocker (works for both inner race and outer race)

You can also get bearings and bushings with flanges or shoulders which can help if you are using a slip fit mounting for the outer race.

It is obviously okay for the shaft to rotate against the inner surface of a bushing since that is how a bushing works. Therefore you obviously do not want press fits or adhesives or set screws to prevent the shaft from rotating in the bushing. However, the outside of the bushing should not rotate relative to its mount just like the outer race of a bearing.

And how do I make sure that these rods wouldn't slide horizontally when the crank handle is rotated that would misalign the sprockets and chain.

There at at least a few common ways to stop the shaft from sliding lengthwise in the inner race of the bearing, in order of increasing security and elegance, but increasing complexity, cost, and convenience of assembly:

1. shaft collars
2. grooves with retaining rings in them, but there are also retaining rings designed to dig into the shaft so do not need grooves
3. put shoulders on the shaft

I suppose in some cases you might be able to get away with using adhesive between the shaft and inner race of the bearing, but this is not a proper method to prevent lengthwise sliding.

Answer 2

Use bearings on both ends of each shaft and locate the bearings in place with grooves in the shafts with circlips or similar.

Or, turn down the outer ends of the shafts to give a register for the bearings to locate against and thread the shaft for locking nuts.

Other possibilities are also possible.