The equal-and-opposite momentum is applied to the cutters themselves, not to
the other half of the lead.

Bob Ammerman
RAm Systems
(contract development of high performance, high function, low-level
software)

----- Original Message -----
From: "Olin Lathrop" <olin_piclist@EMBEDINC.COM>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Friday, August 17, 2001 8:45 AM
Subject: Re: [PIC]: Oscillator leads


> > Not when you use shockless cutters (see my previous post on this thread)
> The
> > cutters produce a flat cut on one side and that means there is no wedge
> > formed to push the lead back in that direction. All the energy goes into
> > pushing the portion of the lead with the wedge on it. I will try some
> ASCII
> > art.
> >
> >
> >                 | /
> > --------------| |/  /--------
> >   component   |    /  excess
> >     lead      |    \  lead
> > --------------| |\  \--------
> >                 | \
> >  <- no force   cutter  force applied ->
> >                blades
>
> Your physics doesn't add up.  If "all the energy" goes into the excess
lead,
> it will presumably be converted to kinetic energy of that lead causing it
to
> fly off.  Since the excess lead goes from still to a moving state, its
> momentum was increased, which means some impulse (force over a time
period)
> was applied to it.  According to Newton and conservation of momentum,
> EXACTLY THE SAME impulse is applied in the other direction to whatever
> pushes the excess lead away.  In other words, whenever a lead flys off, a
> "shock" has been delivered to the board, regardless of the cutting
> mechanism.
>
> The shockless cutters I've seen are shockless because they cut the leads
in
> such a way that they don't fly off.  They work more like scissors than
wire
> cutters.  The lead is sheared sideways instead of pinched.
>
> This all being said, I agree that it is unlikely that trimming the crystal
> lead on the other side of the board after soldering caused the problem.
>
>
> ********************************************************************
> Olin Lathrop, embedded systems consultant in Littleton Massachusetts
> (978) 742-9014, olin@embedinc.com, http://www.embedinc.com
>
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>

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