DIYbanter - View Single Post - I need a swivel or bearing for a lazy susan style turntable.

lid wrote:

On Mon, 11 Apr 2005 07:00:18 -0400, "J. Clarke"
wrote:

I want to be able to spin 100 pounds items on a 24" wide turntable that
will spin freely as long as possible.

Are these items symmetric or asymmetric? Balanced or unbalanced?

Yes.

So one should assume that the 100 pounds will be a point mass at 12 inches
from the center?

How many
RPM do you want?

As many as humanly possible.

Since you don't say anything about a retention I'm assuming that you are
simply going to lay this point mass on the rim of your platform and allow
friction to hold it. If that is not a valid assumption then please
describe the retention.

To a first approximation and in the absence of any information about the
mating material, the coefficient of friction of of any wood, according to
the Wood Handbook, may be assumed to be .3 as a lower bound. That means
that a 30 pound force will move your 100 pound mass off the table. Using a
safety factor of 1.5, which is a very low safety factor typical of aircraft
design, and if I've run my numbers properly that translates to about 24
RPM. Is that fast enough? If not then there is no point going on with
this until you provide either a number or more definition.

Is most of the mass distributed in the center, around the
rim, uniformly, or what?

Both.

Then again one must assume a point mass at the rim and the above analysis
applies.

Will there be any lateral force applied to the
object, if so how much lateral force?

As much as you could apply with a stiff paint brush or rubber spatula.

If the rubber spatula that I just broke is a fair sample that's about 5
pounds.

How long do you need to spin the
object?

Until I'm finished. The fewer times I have to spin it up the better.

And how long will that be?

Is there an objection to powering it this device?

Cost. I need this to spin 10-20 minutes once a day 4 days a week.

Why didn't you just say that you needed it to spin 10-20 minutes in the
first place? Is that so difficult?

Is there any
possibility that the object being spun will shift during operation?

No.

As I have stated, a wheel hub assembly off a motor vehicle or utility
trailer would probably be perfect.
Getting a suitable one has proven to be a problem.
Not being a welder it's also expensive.
I didn't expect or ask anyone to design anything.

Well, actually you did whether you realize it or not.

I was hoping there might be a bearing assembly 'off the shelf' that might
do this.

There probably is. Have you looked in the McMaster and Grainger catalogs?
But with the information you've given it's difficult to tell which
particular components would do the job for you.

Like bearing assemblies for making your own grinders and sanding
machines only one that supports a horizontal disk.
If the product doesn't exist I'm back to finding a suitable wheel and hub
off a motor vehicle.

--
--John
to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)