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)