Might need bearing lesson, tennis mach ver 2

[Mike Amick]

my new attempt and went super simplistic. But having a problem with bearing rattle.

When I turn the pulleys on the lathe and later spin and touch them up on the axle they spin true.

But when I put the axle thru the bearings, the pulleys and axle wobble just a hair and are noisy as hell.
the bearing is a 6002RS which appears to be a really cheap bearing. Not sure if that is my
problem but are better bearings quieter ?

LATER EDIT; I am having this thought in the back of my head saying that how the bearing fits on the axle has more
importance than I thought. I made the pulley AND the bearing have a slip fit. I can easity grab it and move it
up and down the shaft/axle. Maybe it should be a shrink tit.

Any ways talk bearings to me.

[LKeithR]

What is it?

[Mike Amick]

It's a tennis ball throwing machine. The first one used much bigger wheels and I had a similar problem with those cheap bearings and
an even worse problem with the big solid rubber tires being out of balance and shaking the machine apart. But it threw the ball really far.

These skateboard wheels spin pretty true but i have to really speed it up for it to throw not even as far.

I see other setups of wheel axle bearing and the thing just hummmmms away. I like to learn how to get there.
.

[small.planes]

Single bearing? With a single row of balls?
normally for an axle you would use 2 and add a light preload to take up any slack

Dave

[Bented]

I produce bearing fit bores and shaft journals everyday.

The customer drawings often look like this, a light press fit, -.0005" +.0000"

[A.K. Boomer]

Mike im at a loss as to how this thing is supposed to work in the first place --- I seen the pics of the original design and it's easy enough to figure out plus i knew how they worked to begin with but this is not making any sense to me - how does this launch a tennis ball?

BTW I like that channel lock stuff your using, expensive ?


OK scratch that - I see this is just the initial synchro pulleys and not the engagement ---- I thought you were having trouble with the main engagement hubs,,,
plus the original synchro pulleys looked like they were toothed for timing purposes which I would think critical for keeping proper accuracy of the ball when being launched ???

outside observation --- the original synchro pulleys most likely were toothed for a reason, the reason being is they did not want to just rely on the ball drive wheels momentum alone as one might decide to dominate over the other when the ball gets squeezed and launched - there is a drastic drop in RPM's and then the motors RPM's "get involved"
without a toothed pulley their will most likely be belt slip and deviation between the two ball drive wheels --- if there is then the ball will choose to shoot low or high - you can maybe just adjust for this and maybe it will be somewhat stable but not as stable as with the motors engaged?
plus another honorable mentions is if their is deviation and domination of one drive hub over the other it would accelerate both ball and drive hub wear....

have no idea if this is absolute - just mentioning it waking up with some coffee here...

[chipmaker4130]

Single bearing? With a single row of balls? normally for an axle you would use 2 and add a light preload to take up any slack . . . Dave

This is likely the problem. Even if there are two bearings in that mount, they're not far apart and probably have zero preload. A double-row bearing would minimize, but not eliminate the problem.

[A.K. Boomer]

Mike are you starting from total scratch or was your original posting just trying to re-work an existing store bought unit?

[Rich Carlstedt]

Mike, If the shafts turn , they must be a press fit on the inner race of the ball bearings. The outer race does not need a press, but you don't want it bouncing either

On ball bearings, what ever turns must be press fit. On a setup , where the Wheel turns and the axle is stationary, then they outrace must be a press fit.
If you have machined and finish surfaces, then Loctite bearing retainer is possibility so you don't have to make the parts again. and it is applied to replicate a press fit

Rich

[A.K. Boomer]

If you have machined and finish surfaces, then Loctite bearing retainer is possibility so you don't have to make the parts again. and it is applied to replicate a press fit

Rich

Good suggestion in fact they make a "stud and bearing mount" just for this type of purpose, I believe it's green and strong as all hell...

If you have any clearance at all you want to apply liberally on both parts and "spin them together" if you can then let set up with "no load" not even gravity if you can help it as you don't want the fluid to go "eccentric" before it hardens....

[Mike Amick]

Ok ... both were from scratch. The main difference is the original one had bearings on both sides of the drive wheel. This time
I used a thick block and have a bearing on both sides of the block. And the aluminum extrusion made things some what easier
and it's a little expensive but not too bad.

And AK, I think I will try and loctite the bearing to the axle and take your advice about spinning it and preventing it from settling into misalignment

If that doesn't work I will make new axles that press fit.

Also I will remember what Rich said about the outside bearing not needing to be pressed on.

But I can't but think there may be better bearings to use, the ones i am using are like $1.50 a piece. 15mm

Oh, real quick, how do I preload ?

[chipmaker4130]

. . .I think I will try and loctite the bearing to the axle and take your advice about spinning it and preventing it from settling into misalignment . . .

The best way to achieve this goal is to apply the retainer and set the assembly with the shaft vertical. It doesn't take long for it to set.

[Rich Carlstedt]

Ok ... .........................
But I can't but think there may be better bearings to use, the ones i am using are like $1.50 a pi
Oh, real quick, how do I preload ?

Mike, there are two kinds of "Preload" , there is Radial Preload , and Axial Preload

Radial is a function of the interference fit between the axle and the inner bearing race.
For example, if the shaft was .0005" bigger than the Bearing ID , That would become the preload Radially on the bearing.
You could consider the bearing inner race as being elastic and conforming to it's new diameter

Axial Preload requires shims or adjustable nuts to shift the two bearings apart or together . That means if the inner races are rigidly locked in place, that
the outer races be pushed inward or pulled outward from each other by using adjustable nuts or spacers. Sometimes spring washers are used as well.

Rich

[Bented]

Ok ... both were from scratch. The main difference is the original one had bearings on both sides of the drive wheel. This time
I used a thick block and have a bearing on both sides of the block. And the aluminum extrusion made things some what easier
and it's a little expensive but not too bad.

And AK, I think I will try and loctite the bearing to the axle and take your advice about spinning it and preventing it from settling into misalignment

If that doesn't work I will make new axles that press fit.

Also I will remember what Rich said about the outside bearing not needing to be pressed on.

But I can't but think there may be better bearings to use, the ones i am using are like $1.50 a piece. 15mm

Oh, real quick, how do I preload ?

ABEC (Annular Bearing Engineering Committee) ,you preload the bearings by using pairs of angular race bearings pressed together much like a milling machine or lathe spindle.

ABEC 7 bearings are wonderfully accurate and smooth running but cost well over $1.50.

If making a prototype product do not go cheap, if a home project do not go cheap as you have experienced.
https://www.grainger.com/search/powe...SAAEgLRFfD_BwE
Good Luck

[oxford]

Just be forewarned, if you use bearing retainer Loctite, you will most likely destroy the bearings when it’s time to come apart.