[TheForge] Little Giant / pulley / rpm / ???

[jerry Frost]

Yeah, I've had that very discussion Mike. Did said fellow know the
difference between kinetic energy and momentum? I was kind of disturbed by
the number of college grads I've talked to who didn't. Energy is conserved,
not type sure, Mr. Newton said that and as far as I know it's a good
description of the observed evidence, even does a pair job of prediction.

I was trying to get out of said conversation with a fellow once but he'd
scented blood and wasn't about to let me go. He wasn't amused when I asked
him, (to paraphrase.) "So tell me how much energy is conserved in a lb. of
bullshit?" He wasn't amused and deprived me of his presence thereafter. I
guess he couldn't conserve the momentum in his argument. 

No snow here to speak of this year. How'd that Ruffed grouse taste?

Jer

-----Original Message-----
From: TheForge [mailto:theforge-bounces at mailman.qth.net] On Behalf Of Mike
Spencer
Sent: Sunday, March 22, 2015 2:42 PM
To: theforge at mailman.qth.net
Subject: [TheForge] Re: Little Giant / pulley / rpm / ???


Bruce wrote:

> You sound disgruntled.

You meh say dat.

> ... "Snow is beautiful!"...

Yes, it is.  I spotted a ruffed grouse doing its courting display, ruff up,
tail feathers spread, only the second time in my life I've managed to see
one of these perfectly camouflaged birds do this. It was only because of the
snow that he was visible.  I feel bad for the poor, pathetic guy. "Yow!
Hey, ladies!  Time for hanky-panky, time to nest, start a family!  Here I
am!"  Only the snow is still 4' deep over everything a grouse holds dear
except the edible buds on my apple trees. (Growl)

> I guess I can't blame you for being mildly annoyed by 4 feet of snow.

Indeed.  A little spring snow storm is nothing out of the ordinary here.
But *not* 12" on top of 2 or 3 feet already laying on.

> There on pp 450ff (of the 12th Ed., 1943 -- years before I was
> born!) are formulas for al sorts of springs.

Oh, good. Although my copy is newer (1971), it has 45 pages of stuff on
springs plus more under "shafting" re torsional loads.  So far, I'm good
with f = kx although now I wonder if loads on a LG spring might qualify as
"shock" loads (vs. "static"), accounting for the rather hefty size of an LG
(or similar hammer) spring.

> And you're dating yourself with the MacHinery reference.  I doubt 
> anyone under 40 has even heard that one.

Yeah, yeah, well, I'm older than your M'sHbk, so there.  I'm older than Old
Bert Shaw was when he got me interested in smithing in the first place.  Up
until recently, I was fairly hip vs. the "kids": 6 working computers, Linux
etc. Now, with no cell phone, no tablet, no Farcebook or Twitter or gmail or
U-tube but still dial-up internet, I confess that I'm a relic.  And the
average age of a tool in my shop is... what?  Maybe 75 years, all those nice
new^h^h^h newish power tools notwithstanding?

> I will NOT recommend HF anvils for any serious blacksmith.  But these 
> are for demos in which a novice might be working -- and dinging up the 
> face.

My *very* *first* blow struck at the anvil: I was hanging around Bert Shaw's
shop in Leverett, Mass.  He points at the sledge hammer so I pick it up.  He
pulls something out of the fire, lays it on the anvil and says, "Hit it".
So I did, only I missed the workpiece completely and made a ding in the edge
of the anvil.  And froze up, like a deer in the headlights, thinking that I
might have to run for my life.  But Bert say, "Hit it, HIT IT!"  So I did,
didn't miss again.

Pretty soon, Bert puts the iron back in the fire, takes his nasty, twisty
little cigar out of his mouth, spits on the floor and says, "Don't worry if
you can't hit twice in the same place.  Some days, I can't hit *once* in the
same place."  I surmise that I've been a blacksmith ever since. :-)

Post-Script for Bruce:

> ...dead-blow anvil...

I had an argument with one of the instructors at MIT when I was doing demos
there.  Isaac Newton said momentum is conserved.  Who am I to argue with
Newton (genuflect)?  But if you drop, say, a steel ball into a tub of wet
clay, it stops.  There is no motion, thus no v, so no mv.

Makes perfect sense in terms of energy: the energy (whatever that is,
exactly :-) is converted to heat, maybe a little to gravitational potential
energy by pushing some of the clay up, and so on. So I'm good with
conservation of energy because you can have energy that doesn't depend on
velocity.  But my MIT guy just insisted that momentum is conserved.

How is that dealt with in practical engineering?  Surely you don't do some
gnarly thing with the mass of the earth and a 10 to the minus bignum change
in its velocity.  Or do we just tell Newton (and my MIT
guy) to stuff it?

Just a little distraction for you while you rest up from your workshop.


- Mike

-- 
Michael Spencer                  Nova Scotia, Canada       .~. 
                                                           /V\ 
mspencer at tallships.ca                                     /( )\
http://home.tallships.ca/mspencer/                        ^^-^^
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