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  #2   Report Post  
Wilson Lamb
 
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If you can get a little metalwork done, a front car hub would be great.
Tell us how much weight you want to carry.
Wilson
wrote in message
...

I can't find anything to solve my problem because I obviously don't know
how to
explain my problem.
I want the be able to spin by hand a heavy 24" round turntable on top of
my
workbench using centrifugal force. Like the wheel on a car but horizontal.

I was going to make it out of 4 inches of MDF but I can't find a bearing
or
swivel or anything that will allow this top spin horizontally.
Lazy susans are strong and stable but don't allow a friction free spin.

I'm sure what I need is out there but I have no idea what it is, or what
it's
called.

There are all sorts of bearing to spin stuff vertically, isn't there one I
can
attach to this table that doesn't cost hundreds of dollars.



  #6   Report Post  
Duane Bozarth
 
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WillR wrote:
....
Force is acting downward when stopped and mostly horizontal when rotating.


The gravity load doesn't behave any different whether it's spinning or
not...

To OP, what you're application calls for is a "thrust bearing". Lazy
susans or rotating TV, etc., stands are commercially available for 100+
lbs. The large under-counter one Dad and I built for Mom some 30 years
ago now, used the thrust bearings from a small disc--3/4" shaft
available from a good farm implement supply. What their actual load
rating is I'm not sure, but it would easily hold 250-300 lb, I'm sure.
  #7   Report Post  
CW
 
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1000 pounds and ball bearings.

"WillR" wrote in message
...

I checked Lee Valley. Load capacity 100 lbs. on the largest Lazy Susan.
http://www.leevalley.com/wood/page.a...50,43298,43316

They use roller bearings. Since I was going to suggest this was a roller
bearing application anyway it seems like a good fit... If these are high
quality they should be low friction. Maybe they would work...

Force is acting downward when stopped and mostly horizontal when rotating.

--
Will
Occasional Techno-geek
http://woodwork.pmccl.com



  #13   Report Post  
Wilson Lamb
 
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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.
Wilson
wrote in message
...
On Sun, 10 Apr 2005 08:08:08 -0700, Larry Jaques

wrote:

On Sat, 09 Apr 2005 23:10:28 -0700, the inscrutable
spake:


I can't find anything to solve my problem because I obviously don't know
how to
explain my problem.
I want the be able to spin by hand a heavy 24" round turntable on top of
my
workbench using centrifugal force. Like the wheel on a car but
horizontal.


Give us more info. What are you making? Will any forces be at work,
such as a cutting tool or shaping forces from the side? What weight
will be on the table? How much external force will be applied?

Very little side force. The table itself will be the heavy part because I
want
to use the weight to keep it spinning.


I was going to make it out of 4 inches of MDF but I can't find a bearing
or
swivel or anything that will allow this top spin horizontally.
Lazy susans are strong and stable but don't allow a friction free spin.


Hmm, lazy susans don't don't much force to spin, even with 200# on
'em.

For a close-to-friction-free unit, mount a cut-off truck axle (with
bearing and wheel) to a metal frame and put an MDF (or real wood) top
on it.


I tried to go this route.
Auto wreckers won't do it and they want a minimum of $250 for the hub off
anything.
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.




  #15   Report Post  
Patriarch
 
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lid wrote in
:

On Sun, 10 Apr 2005 02:42:41 -0500, Patriarch
wrote:

wrote in
m:


I can't find anything to solve my problem because I obviously don't
know how to explain my problem.
I want the be able to spin by hand a heavy 24" round turntable on
top of my workbench using centrifugal force. Like the wheel on a car
but horizontal.

I was going to make it out of 4 inches of MDF but I can't find a
bearing or swivel or anything that will allow this top spin
horizontally. Lazy susans are strong and stable but don't allow a
friction free spin.

I'm sure what I need is out there but I have no idea what it is, or
what it's called.

There are all sorts of bearing to spin stuff vertically, isn't there
one I can attach to this table that doesn't cost hundreds of
dollars.



Larry Jaques suggested that this was very similar to a potter's kick
wheel.


Kicking a wheel on top of a 36" work bench could be tough. I'm just
not that limber any more.
I need something that can rest on the bench, not the floor.



Sorry, I wasn't clear. I was under the impression you were looking for
bearings that could handle both a heavy vertical load, as well as side
loading. I understood that the turntable would likely be motor-driven
in some manner. My thought was that the bearings used for a potter's
kick wheel would be suitable, not that you actually use that
configuration.

I wish you well with your quest.

Patriarch


  #16   Report Post  
Hax Planx
 
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J. Clarke says...

Assuming it's balanced and he doesn't apply any side force.


The lazy susan bearing will tolerate some side force. I just don't
think he will have a problem with it since the disk isn't that big or
heavy. He said he had a 12" LS bearing. That should be massive
overkill for his purposes.
  #17   Report Post  
Andy Dingley
 
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Default

On Sun, 10 Apr 2005 14:21:35 -0400, WillR
wrote:

Since the lazy Susan has a race of ball bearings it will handle side
forces


I've never seen a Lazy Susan that would handle side loads. They're a
simple thrust bearing with pressed steel races. There's no sideways
location of the two races, so any sideload tends to lift the upper
race off the balls and then shift the two races relative to each
other, jamming them.

It's not a good practice to put a sideload through any pure thrust
thrust bearing,. But if you must do it, use one with deep races, not
the cheapest of pressed races.

If you have space, the easiest solution is a car hub. They're
enormously over-engineered for this task, so you can simply ignore the
direction of the applied thrust.

  #18   Report Post  
John Flatley
 
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BlairR,

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
of time.

Although I've seen a number of solutions offered, I submit to you that if
you
describe in some detail what you are trying to accomplish with your
turntable,
you will give the talented folks in this group a clearer picture of your
problem
and they will come up with workable ideas and maybe even the answer to
your 'prayers.'

Jack

--
wrote in message
...

I can't find anything to solve my problem because I obviously don't know

how to
explain my problem.
I want the be able to spin by hand a heavy 24" round turntable on top of

my
workbench using centrifugal force. Like the wheel on a car but horizontal.

I was going to make it out of 4 inches of MDF but I can't find a bearing

or
swivel or anything that will allow this top spin horizontally.
Lazy susans are strong and stable but don't allow a friction free spin.

I'm sure what I need is out there but I have no idea what it is, or what

it's
called.

There are all sorts of bearing to spin stuff vertically, isn't there one I

can
attach to this table that doesn't cost hundreds of dollars.



  #19   Report Post  
World Traveler
 
Posts: n/a
Default

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.
wrote in message
...
On Sun, 10 Apr 2005 20:44:33 -0400, "John Flatley"
wrote:

BlairR,

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
of time.

Although I've seen a number of solutions offered, I submit to you that if
you
describe in some detail what you are trying to accomplish with your
turntable,


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.




  #20   Report Post  
J. Clarke
 
Posts: n/a
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lid wrote:

On Sun, 10 Apr 2005 20:44:33 -0400, "John Flatley"
wrote:

BlairR,

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
of time.

Although I've seen a number of solutions offered, I submit to you that if
you
describe in some detail what you are trying to accomplish with your
turntable,


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.


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.

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.


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


  #21   Report Post  
J. Clarke
 
Posts: n/a
Default

lid wrote:

On Sun, 10 Apr 2005 23:28:01 -0400, "J. Clarke"
wrote:

wrote:

On Sun, 10 Apr 2005 20:44:33 -0400, "John Flatley"
wrote:

BlairR,

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
of time.

Although I've seen a number of solutions offered, I submit to you that
if you
describe in some detail what you are trying to accomplish with your
turntable,

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.


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.

Does knowing what I plan to use it for give you a woody?


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".

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? 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
reused?

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.


--
--John
to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)
  #22   Report Post  
George
 
Posts: n/a
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wrote in message
...

I want to be able to spin 100 pounds items on a 24" wide turntable that

will
spin freely as long as possible.



Tapered roller bearings, as you and others keep mentioning, are ideal. Buy
trailer spindles and bearings from some place like Northern and use 'em.


  #23   Report Post  
WillR
 
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Default

J. Clarke wrote:
lid wrote:


On Sun, 10 Apr 2005 23:28:01 -0400, "J. Clarke"
wrote:


wrote:


On Sun, 10 Apr 2005 20:44:33 -0400, "John Flatley"
wrote:


BlairR,

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
of time.

Although I've seen a number of solutions offered, I submit to you that
if you
describe in some detail what you are trying to accomplish with your
turntable,

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.

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.


Does knowing what I plan to use it for give you a woody?



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".


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? 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
reused?

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
definitions.

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.

ROTFLMAO


--
Will
Occasional Techno-geek
  #24   Report Post  
Tom
 
Posts: n/a
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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.


You can buy hub units that have the lug bolts on one side and a four
bolt flange on the other allowing you to mount both sides - one to a
base and the other to the turning table. Would this work for you?
  #26   Report Post  
John Flatley
 
Posts: n/a
Default

BlairR,

I along with several other folks have asked you for more information is
various ways. Your apparent refusal to discuss your project in terms of
objectives and to provide any meaningful detail suggests that you may be
working on a project you want to patent. There may be another reason, but
it escapes me.

I wish you luck in your search for a solution to your 'problem!'

Jack

If you are working on a patentable activity, you might consider enrolling in
an Effective Communication 101 course at a local school to assist you with
future projects.


wrote in message
...
On Sun, 10 Apr 2005 20:44:33 -0400, "John Flatley"

wrote:

BlairR,

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
of time.

Although I've seen a number of solutions offered, I submit to you that if
you
describe in some detail what you are trying to accomplish with your
turntable,


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.




  #28   Report Post  
George
 
Posts: n/a
Default

http://www.northerntool.com/webapp/w...6135&R=1613 5
wrote in message
...
On Mon, 11 Apr 2005 07:16:51 -0400, "George" george@least wrote:


wrote in message
.. .

I want to be able to spin 100 pounds items on a 24" wide turntable that

will
spin freely as long as possible.



Tapered roller bearings, as you and others keep mentioning, are ideal.


Roller bears need something to roll against and that is usually firmly

attached
to the vehicle. If I could find this as a one piece assembly I would.

Buy
trailer spindles and bearings from some place like Northern and use 'em.



  #29   Report Post  
Unquestionably Confused
 
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Default

on 4/11/2005 11:51 AM lid said the following:

None of you gave me any help you moron.
I already had a solution.
A hub from a utility trailer bolted to my work bench.
I was looking for a 'ready to wear' more elegant solution in a bearing assembly.
Something already out there.
Lee Valley had already said a lazy susan bearing would not work but that didn't
stop some of you from insisting they were wrong.

BTW you putz I hold 3 patents that have paid me over $12,000 dollars in the past
ten years. Peanuts for sure but it isn't my job, it a result of always trying to
make my hobbies more efficient.
I'm a hobby woodworker and gardener, and full time computer tech, not a pretend
engineer like some of you morons.

So **** off. I politely gave all the information needed to explain my problem.
Then I was insulted because I wouldn't give you detailed plans of my end use.
You don't need to know my end use to answer the question.

I have a welding shop attaching a flange to the axle stub of a utility trailer
hub assembly right now.
It is perfect for my needs, no thanks to this group of ignoramuses.


It's really a shame that some folks have to get testy like this when
they toss out a plea for help to a group of "unknowns."

It's also a shame that when folks attempt to help them, take the time to
"really get into the problem" in an effort to help are thwarted or,
worse yet, ridiculed by the very person they sought to help simple
because they 1) chose to share their personal experiences, 2) asked more
questions so as to make an informed suggestion or 3) had the audacity to
suggest that perhaps a clerk at a woodworking supply emporium - even one
as well thought of as Lee Valley - MIGHT not be endowed with infallibility.

As for that, perhaps you gave Lee Valley more information than you gave
us. Maybe you didn't ask them at all? I realize that the above
information may have been "snipped" but I find it difficult to believe
they would tell you it wouldn't work since they have a numnber of "lazy
susan" devices that will handle up to 1,000 lbs and could be had in a
size that would rival the size of the turntable itself albeit at a loss
of capacity in that it would only hold 660 lbs.

I'm glad you found something perfect for your needs. Did it include a
gift certificate to a Dale Carnegie Course or a class in effective writing?

Plonk!
  #30   Report Post  
Unquestionably Confused
 
Posts: n/a
Default

on 4/11/2005 12:49 PM lid said the following:
tripping bozos with only enough knowledge to be dangerous, and NO experience.

HAND


JOB?






  #32   Report Post  
J. Clarke
 
Posts: n/a
Default

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)
  #33   Report Post  
J. Clarke
 
Posts: n/a
Default

WillR wrote:

J. Clarke wrote:
lid wrote:


On Sun, 10 Apr 2005 23:28:01 -0400, "J. Clarke"
wrote:


wrote:


On Sun, 10 Apr 2005 20:44:33 -0400, "John Flatley"
wrote:


BlairR,

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 of time.

Although I've seen a number of solutions offered, I submit to you that
if you
describe in some detail what you are trying to accomplish with your
turntable,

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.

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.


Does knowing what I plan to use it for give you a woody?



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".


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? 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
reused?

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
definitions.

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.

ROTFLMAO



--
--John
to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)
  #34   Report Post  
Robert Bonomi
 
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In article ,
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.

How many
RPM do you want?


As many as humanly possible.

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


Both.

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.

How long do you need to spin the
object?


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

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.

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.
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
motor vehicle.



Have you considered the swivel mechanism from a _chair_?? or a piano stool?

I just got a catalog from Van Dykes Restorers (www.vandykes.com)

They've got chair assemblies rated for several hundred pounds.



  #35   Report Post  
Teamcasa
 
Posts: n/a
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wrote in message
...

I can't find anything to solve my problem because I obviously don't know
how to
explain my problem.
I want the be able to spin by hand a heavy 24" round turntable on top of
my
workbench using centrifugal force. Like the wheel on a car but horizontal.

I was going to make it out of 4 inches of MDF but I can't find a bearing
or
swivel or anything that will allow this top spin horizontally.
Lazy susans are strong and stable but don't allow a friction free spin.

I'm sure what I need is out there but I have no idea what it is, or what
it's
called.

There are all sorts of bearing to spin stuff vertically, isn't there one I
can
attach to this table that doesn't cost hundreds of dollars.


Here is how I would do it.
I would drill 3" holes in all but the last (top) piece of MDF. Insert two
or three common single row sealed ball bearings. Mount the shaft on a 12"
square steel plate. Weld it or if no access to a welder, press and swedge
fit. Add a spacer over the shaft to stop the disc from hitting the base
and allow the shaft to reach all ball bearings without touching the top
piece of MDF.

Mount/secure vertically and balance. Re-mount on bench and spin away.

Note: Bearing holes and shaft size are dependant on the size bearing you
buy. Typ. Bearing this general size is $8. Graingers.

Dave



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  #36   Report Post  
WillR
 
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J. Clarke wrote:
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
tho... LOL

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.


--
Will
Occasional Techno-geek
  #38   Report Post  
WillR
 
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lid wrote:
On Mon, 11 Apr 2005 15:35:24 -0400, "J. Clarke"
wrote:


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?


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.


I would suggest that you re-read John's post again. You are likely
concentrating on the wrong point in his post. Since you aren't saying
that much about the stuff you are doing, one can only guess as he points
out, but the real issue may be whether it will stay on the table or not.
You may want to do a force calculation based on a symmetrical balanced
load (placed at the center), and then estimate forces based on an
unbalanced load -- i.e. on the rim. Somewhere I saw you mention 150 RPM,
and now it is 100 lbs. -- possibly unbalanced -- at the outer edge of a
24 inch rim. As John points out -- you must assume the total weight is
on the rim to do the worst case calculation... I will leave it to the
mechanical engineer in you to worry about the safety issues.

While I could do the calculations I can't be bothered as you seem to be
quite capable of doing them. (Someone might be able to tell us the
velocity of the rim of a 24" diameter circular platform, and the
resultant force of a 100 lb. object. The impulse on a floor if it flies
off a 34" high work bench might be an interesting calculation as well.
:-) Better test it outside. :-) )

The people here are not being dinks -- they are pointing out that you
may have missed some significant design factors.

My last post on this topic.

Thanks for listening.

--
Will
Occasional Techno-geek
  #40   Report Post  
Larry Jaques
 
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Default

On Mon, 11 Apr 2005 09:51:57 -0700, the inscrutable
lid spake:

On Mon, 11 Apr 2005 09:17:01 -0700, Larry Jaques
wrote:

On Sun, 10 Apr 2005 22:02:14 -0700, the inscrutable
spake:

On Sun, 10 Apr 2005 23:28:01 -0400, "J. Clarke"
wrote:

--snip--
Does knowing what I plan to use it for give you a woody?


With an attitude like that, you don't deserve any more help from any
of us. Whadda maroon.


None of you gave me any help you moron.


You gleaned no terminology from any of us, hmmm?


I already had a solution.


Then why did you post a request in the first place and then
ungratiously bat down over a dozen tips?


A hub from a utility trailer bolted to my work bench.
I was looking for a 'ready to wear' more elegant solution in a bearing assembly.
Something already out there.


Then you should have said so, y'think?


Lee Valley had already said a lazy susan bearing would not work but that didn't
stop some of you from insisting they were wrong.


With that much load, they'd take a lot more lateral force than they
would with a light load.


BTW you putz I hold 3 patents that have paid me over $12,000 dollars in the past
ten years. Peanuts for sure but it isn't my job, it a result of always trying to
make my hobbies more efficient.


And I hold no patents but have made that much from my glare guards
in the same amount of time. I'll bet your patents cost you the better
part of that $12k, too.


I'm a hobby woodworker and gardener, and full time computer tech, not a pretend
engineer like some of you morons.


That's "Technical GODs" to you, sir. g


So **** off. I politely gave all the information needed to explain my problem.
Then I was insulted because I wouldn't give you detailed plans of my end use.
You don't need to know my end use to answer the question.


You're trying to leech free info from us to use to make more money? I
see. Think anyone here will ever answer another of your requests?


I have a welding shop attaching a flange to the axle stub of a utility trailer
hub assembly right now.
It is perfect for my needs, no thanks to this group of ignoramuses.

HAND


Into the bit bucket you go, bubba. Ta!


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