Very little side force. The table itself will be the heavy part because I want
to use the weight to keep it spinning.
I tried to go this route.
Auto wreckers won't do it and they want a minimum of $250 for the hub off
I can buy an entire utility trailer kit for less.
But I was hoping to find a nice floor flange (like on single pedestal table) and
a center bearing that might work.
Now I remember. Get a weld on stub axle and hub from Northern Hydraulics.
Have the axle welded in the center of a 1/4" plate of whatever size you
want. Cut off the axle to pit the hub as low as possible, before welding .
Or drill the plate to let the axle go through and then weld at the
appropriate height. Drill another plate, or maybe your wood, to bolt up
where the wheel would ordinarily go. I think you can find a hub with no
studs in it or maybe press the studs out of one that comes with studs. Then
you can use long bolts to hold the wheel on the hub.
The weak point of all this is that the normal hub diameter is relatively
small conpared to the table width, so the table must be pretty rigid. Come
to think of it, you could use a regular rim as the base of your table, if
that doesn't put you too far above the bench. Four little J bolts could
hold a plywood table to the top of the rim. You could fill the rim with
shot to raise its inertia.
When you find one, let me know. I need a friction-free bearing for my
perpetual motion machine :-).
But seriously folks, it's hard to find a lower friction coeffecient than
a lubricated ball bearing.
I just bought a lazy susan that's a large circle with said bearings and
it's rated for 1000 pounds. Readily available at Ace hardwares, or
cheaper online if you have other stuff to share the shipping cost.
Think air. Use a regular bearing for centre-ing and an air cushion to
Perfboard with some routed out channels and a regulator. Over a large
enough area, you'll be able to move tonnage with absolutely no effort
and the regular ball bearing will keep things in place.
10's of thousands of pounds, I tell ya. Four 12" diameter pucks moved a
buddy's printing press like it was floating on air...waitasec..it darn
well WAS floating on air.
You know how they stopped it from moving?
Yup... turned off the air.
btw...the compressor they were using was a 3 HP, 20-30 gallon tank. it
wasn't working that hard.
You only need a little air to get lift...more air does nothing.
Did I help ya? Huh? Huh?
You can use a router with circle cutter jig and a round nose bit to cut a
rounded bottom circular channel in the top and bottom MDF. Fill channel
with marbles. I had made one of these using 3/4" plywood approx. 30"
diameter with channel at 24". Can't see why MDF wouldn't work for you.
Don't remember MDF being available when I made that top 20 years ago This
was a TV rotator. (I use for about 8 years never a problem and very little
force needed to turn about 100 lbs. (you could even get the marbles at a $1
store.) This whole project should do the trick and its pretty cheap too.
I may be missing a few appends to your posting, but I still do not have a
picture of what you are trying to do.
You want to spin by hand, not turn, a 24" diameter, 4" thick MDF turntable
located on your workbench. And you want it to spin this turntable with
something unknown on it, at some unknown rpm for some unknown period
Although I've seen a number of solutions offered, I submit to you that if
describe in some detail what you are trying to accomplish with your
you will give the talented folks in this group a clearer picture of your
and they will come up with workable ideas and maybe even the answer to
I want to spin a heavy turntable 24" across. I want it to spin easily and for as
long as possible while supporting about 100 pounds.
Replace the wheel and tire on a utility trailer, or a car or truck with a heavy
table the same size as the tire turn it on edge so it is horizontal and give it
the ability to sit in or on a work bench and it would work great.
I can get the hub, and the bearing.
But getting the part the bearing sits in and fastening that to a work bench is
beyond my ability and rather costly.
I was hoping there was a product out there that would do this.
I can find all kinds of shafts and bearings to spin a vertical disk like
grinding stones but nothing that will support a horizontal disk.
On a lazy susan I made, there were two pieces -- the revolving "plate", and
the stand on which the plate sat. I mounted a large dowel to the back of
the revolving plate, and then recessed the bearings from the front wheel of
a bicycle into the stand., with a similar bearing set at the bottom of the
column into which the dowel sat, This gave a very smooth and sturdy support
to the plate, which turned easily with the touch of the hand.
I thought of a bicycle wheel but I don't think it's strong enough.
I thought a front tire off a motorcycle might be great using the disk brake as a
flange to fasten the table.
But I've never even seen a motorcycle wheel up close.
I then to shy away from the greasy end of things, like cars and stuff.
Do you want to do this because spinning a heavy turntable 24" across
supporting 100 pounds gives you a woody, or is there some higher purpose to
it? In other words is spinning the turntable your ultimate goal or is the
turntable a means to an end? If it's a means to an end perhaps if you
described that end you might get more useful advice.
No, knowing what you plan to use it for helps me figure out what would be a
suitable design. And designing things _does_ give me a woody.
If you went to an engineer and asked for an estimate on the cost to design
such a thing, whatever he came up with would be at least doubled due to
"lack of definition".
Are these items symmetric or asymmetric? Balanced or unbalanced? How many
RPM do you want? Is most of the mass distributed in the center, around the
rim, uniformly, or what? Will there be any lateral force applied to the
object, if so how much lateral force? How long do you need to spin the
object? Is there an objection to powering it this device? Is there any
possibility that the object being spun will shift during operation? Have
you given any thought to retention? Are you going to be performing cutting
operations of any kind on the device being spun? Painting? Anything else?
What's your budget for this? What do you have already that might be
Is there a college near you? If so visit the library and find a book on
machine design and read it through. Then perhaps you'll understand why
you're being asked for more definition.
Very well put.
I grew to hate high tech and engineering because of sloppy problem
Nice/bad to see it wasn't only high tech that suffered from these problems.
Usually after I was awarded a job I would talk to the customer and say
something along the lines of "OK now -- lets nail down all the
specifics..." Then I would be told -- "you're the expert -- figure out
what we want -- we don't have any more time to put into this". Then
..."Let us know when you have it working -- then we'll test it and tell
you if we like it". Then "If it isn't up to standard you can fix it at
your own cost cause you should'a been able to figure it out...".
Not all at once mind you -- just in dribs and drabs as it was revealed
to you the pickle you'd got yourself into.
Then there are the companies that have learned the hard way about lack of
definition and overreact. I remember one fairly small job we did for
Boeing (you could hold the part in one hand and it was all fabric) where we
had to hire a guy to keep track of the spec revisions and clear out an
office to hold it all--this was in the days before electronic
distribution--the spec arrived on a pallet.
Pretty funny actually. I have seen that too. Since I won't do gov't
contracts anymore I don't see it very much. I did enjoy your story
Been in High Tech since 68 -- have never worked for a company that
wasn't all electronic format (of some kind) on the specs and product
definitions -- except clients. So I can't really relate personally --
but it's still funny.
As much as you could apply with a stiff paint brush or rubber spatula.
Until I'm finished. The fewer times I have to spin it up the better.
Cost. I need this to spin 10-20 minutes once a day 4 days a week.
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.
I was hoping there might be a bearing assembly 'off the shelf' that might do
this. 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
So one should assume that the 100 pounds will be a point mass at 12 inches
from the center?
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.
Then again one must assume a point mass at the rim and the above analysis
If the rubber spatula that I just broke is a fair sample that's about 5
And how long will that be?
Why didn't you just say that you needed it to spin 10-20 minutes in the
first place? Is that so difficult?
Well, actually you did whether you realize it or not.
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.
The hundred pounds could be any size or shape, but I would only be spinning
cylindrical items of course. I don't make anything over 100 pounds in one piece.
I suspect my hub rated at 3600 pounds should be up to the job.:)
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