How do you design a ball bearing rotator? - Mechanical - Engineer Boards
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# How do you design a ball bearing rotator?

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Hello geniuses,

I would say "fellow" geniuses, but clearly, I am not a genius.

I'll be honest, I have no idea if I'm in the right place. I was describing this to a friend of mine asking him for help (he's kind of a genius, but apparently not a big enough one). After describing what I wanted to do, he goes "What do I look like, a god damn mechanical engineer?". Thus, here I am...

What I want to do can be described rather simply in this picture:

Use example: You put a laser pointer on the end of this rod. You hold the right on your right hand. You use your thumb (from the same hand), and slide the knob forwards or backwards (while keeping the rest of your hand in the same position, so all you're moving is your thumb). When you slid the knob as far forward as you can, the laser pointer points to your 4 o'clock. When you slide it back as far as you can, it points to 9 o'clock.

Any ideas? Anything out there pre-made that I don't know about? Belt drive seems logical but would be too "jerky" with movement -- seems like ball-bearing would be a better idea.

Thank you!

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Let me make sure I understand you.  You are trying to grip the gray link, move the golden nub linearly with your thumb, which when moved a full stroke, will cause the black link to rotate 180 degrees?  What is the belt drive for that you think a bearing would accomplish?

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Which axis are you trying to to rotate the black thing about?  Does it rotate about it's own longitudinal axis (so it spins) or are you trying to rotate the black stick about the attachment point to the grey slide stick (like a "T" where the top bar spins but the stem does not)?

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@knight1fox3 This is unrelated to test prep. Can you please move it? THX.

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9 hours ago, EngrPaper said:

Let me make sure I understand you.  You are trying to grip the gray link, move the golden nub linearly with your thumb, which when moved a full stroke, will cause the black link to rotate 180 degrees?  What is the belt drive for that you think a bearing would accomplish?

Thank you for the responses!

Yes, that's correct for the most part.

I would assume bearings would be smooth, like how a caster can rotate.

8 hours ago, MA_PE said:

Which axis are you trying to to rotate the black thing about?  Does it rotate about it's own longitudinal axis (so it spins) or are you trying to rotate the black stick about the attachment point to the grey slide stick (like a "T" where the top bar spins but the stem does not)?

I believe the X axis, like a turntable.

If would be like a cake sitting on a turntable, and then your thumb rotates the table, making the cake sitting on top of it rotate with it...

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Do you want this as a personal project or something you would try to sell? If the former, I would start with a cheap drill motor (battery, motor, gear box, clutch, bearing, chuck) and build up from there. You can intercept the trigger switch and run that to an arduino controller.

For the latter, you would need to think about this a little more and either educate yourself or pay someone to help create a more detailed specification. Start with a phrase of what action you want your thing to do rather than how you think you might accomplish that action.

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16 hours ago, JHW 3d said:

Do you want this as a personal project or something you would try to sell? If the former, I would start with a cheap drill motor (battery, motor, gear box, clutch, bearing, chuck) and build up from there. You can intercept the trigger switch and run that to an arduino controller.

For the latter, you would need to think about this a little more and either educate yourself or pay someone to help create a more detailed specification. Start with a phrase of what action you want your thing to do rather than how you think you might accomplish that action.

Relatedly, is the thumb movement to control the rotation mechanically or electrically?

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On 5/19/2019 at 12:55 PM, JHW 3d said:

Do you want this as a personal project or something you would try to sell? If the former, I would start with a cheap drill motor (battery, motor, gear box, clutch, bearing, chuck) and build up from there. You can intercept the trigger switch and run that to an arduino controller.

For the latter, you would need to think about this a little more and either educate yourself or pay someone to help create a more detailed specification. Start with a phrase of what action you want your thing to do rather than how you think you might accomplish that action.

On 5/20/2019 at 5:47 AM, EngrPaper said:

Relatedly, is the thumb movement to control the rotation mechanically or electrically?

Thank you for the responses!

This is for personal use, and is mechnical (non-electrical).

I figured out that a fishing reel essentially accomplishes "some" of what I'm trying to do, in the sense that the handle of the reel is capable of rotating the top completely with very little movement. The only problem is that it's designed to be held horizontally instead of vertically, the bottom part of the reel is too bulky, and the handle can't exactly be moved with your thumb in the setup I proposed above.

Because of the bulk issue with the reel, I'm back to using part of a ball bearing castor (removed the wheel, etc). I have a handle attached to that, but I'm pulling my hair out trying to figure out how to attach something to it so I can rotate it with a forward/backward movement... I'm guessing I'll need some sort of gears like the fishing reel uses...

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So there are a couple options you could consider.  A rack and pinion would work, if you could find some small enough.  Similarly, you could run a small belt between two pulleys, one of which is attached to your rotating link, and then your thumb device is attached to one side of the belt to slide it back and forth.

As far as making the connection between the two links.  You want a small shaft that will free spin relative to your gray link (that means your bearings need to be mounted in the gray link) and you want that shaft fixed relative to the black link (so you can find some method to attach the shaft to the black link, such as a key, a spline, weld, glue, whatever your application needs).  On that shaft, you will also want whatever device you are using to rotate the black link (the pinion gear for a rack and pinion, or the pulley for belt drive system).  The remainder of the drive components can be housed within the gray link, perhaps will a screw on end so that you can change it out over time.

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The picture isn't loading for me. But it sounds like you're trying to change a translation (pushed or pulled by thumb) into a rotation. That sounds like a piston; a translation getting turned into a rotation. Would something like this work?
http://507movements.com/mm_092.html

So you thumb pushes the piston and causes the laser to rotate? You'd just have to limit the stroke of the piston to only operate over your 180 degrees?

Again, sorry if this is way off base. I can't see your picture.

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