Bring NASA in ( was Re: oz*in NOT oz/in

Dave,

Yes, and that's why it would be nice to see some real-world
experiments to corroborate/ confirm/ extend the data of your
program...

And we still need the numbers for the actual CUTTING forces needed/
encountered...

Hope this helps,

Ballendo

--- In CAD_CAM_EDM_DRO@y..., "dkowalcz2000" <dkowalcz@d...> wrote:
> Folks,
>
> Hmmm. I've been thinking about writing a performance modeling
> program to do this sort of calculation for a while now. E.g., how
> fast can you move/accelerate and what can you cut, given the
physical
> constraints of friction and mass vs. motors & drives? Since it
seems
> like people might be interested, I'll see about putting such a
thing
> together now that I got my copy of Visual Basic back. CAMAS isn't
> bad, but it only spits out Superior Electric part numbers IIRC!
Not
> helpful if one just wants a quick estimate of whether that 150 oz
> motor will pass muster or not before wasting a few days in the shop.
>
> In the meantime, it's not really as trivial a calculation as one
> might think. The lead angle of the screw, rather than the pitch,
> determines to a large degree how much force you can multiply. So a
> 1/4-20 will yield less force than a 1/2-20, for the same torque.
But
> the 1/2" one is a trade-off with more inertia. There's a bit of
> torque required just to get something to move at all. And of
course,
> an ACME does a better job of it than a 60 deg threaded rod, and
> ballscrews better still.
>
> Dave Kowalczyk
> Everett WA
>
> --- In CAD_CAM_EDM_DRO@y..., "dave_ace_me" <davemucha@j...> wrote:
> > Hi Guys,
> >
> > not to get too far afield here, but NASA
> > http://www.grc.nasa.gov/WWW/K-12/airplane/thrsteq.html
> > offers this little bit.
> >
> > " If we are dealing with a solid, keeping track of the mass is
> > relatively easy; the molecules of a solid are closely bound to
each
> > other and a solid will retain its shape. But if we are dealing
with
> a
> > fluid (liquid or gas) and particularly if we are dealing with a
> > moving fluid, keeping track of the mass gets tricky. For a moving
> > fluid, the important parameter is the mass flow rate. Mass flow
> rate
> > is the amount of mass moving through a given plane over some
amount
> > of time. Its dimensions are mass/time (kg/sec, slug/sec, ...) and
> it
> > is equal to the density (r) times the velocity (V) times the area
> > (A). Aerodynamicists often denote this parameter as "m dot" (m
with
> a
> > little dot over the top). Note that "m dot" is not simply the
mass
> of
> > the fluid, but is defined to be the mass flow rate, the mass per
> unit
> > time"
> >
> > So mass over time is refered to as kg/sec or slug/sec. So this
is
> > not the proper measurement for either tourque or force as we use
it
> > in referring to starting a table to move or moving the table.
> >
> >
> >
> >
> >
> > --- In CAD_CAM_EDM_DRO@y..., "stvdnb" <dsa3@u...> wrote:
> > > --- In CAD_CAM_EDM_DRO@y..., Doug Fortune <pentam@c...> wrote:
> > > ...
> > > > torque is measured in 'force*lever arm'
> > > > in other words, oz*in lb*feet N*m
> > > >
> > > > etc, NOT oz/in , lb/ft etc.
> > > >
> > > > (Yes I know oz & lb are not exactly units
> > > > of force, we should be using Slugs but I'm
> > > > afraid that will lead to even More Confusion!)
> > >
> > > If I remember correctly, the slug is a unit of mass, not force.
> > > Pounds and ounces _are_ units of force.
> > >
> > > - Steve