[AT] OT pocket knives

charlie hill charliehill at embarqmail.com
Tue Jul 14 06:46:10 PDT 2015


Thanks.

Charlie

-----Original Message----- 
From: rlgoss at twc.com
Sent: Tuesday, July 14, 2015 9:28 AM
To: Antique tractor email discussion group
Subject: Re: [AT] OT pocket knives

I'll work on posting diagrams and pictures for you all.

Larry
---- Stephen Offiler <soffiler at gmail.com> wrote:
> I'm with Charlie.  I've been trying to visualize this, and I get hung up.
I looked around YouTube a bit, but all I found (in a quick search) were
real, modern, digital planimeters.

A picture is worth a thousand words, and sometimes a video is worth a
thousand pictures.

SO


On Mon, Jul 13, 2015 at 11:31 PM, <rlgoss at twc.com> wrote:

> I just now pulled my pen knife out and tried it, and found I couldn't do
> it -- the knife blade is too dull and it just wants to skip around over 
> the
> paper rather than slice in.   I'll dig a stone out tomorrow to whet things
> a bit and try it again.
>
>
>
> Larry
> ---- charlie hill <charliehill at embarqmail.com> wrote:
> > I guess it's one of those things you have to see to grasp.  I just can't
> visualize it working out.
> Seems to me like if you traced a circuit around a lake or field or 
> whatever
> that both blades would
> end up back at the starting point.   I'm not questioning what you are
> saying.  I just can't
> visualize it.
>
> Charlie
>
> -----Original Message-----
> From: rlgoss at twc.com
> Sent: Monday, July 13, 2015 8:04 PM
> To: Antique tractor email discussion group
> Subject: Re: [AT] OT pocket knives
>
> You let the knife edge ride on the paper surface of the map.  As you trace
> the outline of the lake, field, plat, etc., the knife blade glides along
> and
> slowly gets offset from the base line.  When you have completed the
> circuit,
> the offset distance gets multiplied by the effective length of the knife
> (straight-line distance from the "tracing pin" to the point of contact of
> the open blade with the surface of the map.)  It is tempting to grip the
> "tracing pin" too tightly and make the knife edge skip across the paper
> rather than to "slice" as you navigate the periphery.
> For large areas, you simply break them down into smaller enclosures and 
> add
> them together, just like you do with the professional instrument.  Try it
> with simple geometric shapes or on a piece of quadrille (graph) paper so
> you
> can get the hang of it.
>
> Sorry you won't be in Portersville, Dave.  It's around 90 miles from where
> we now live, and my grandkids enjoy that show.  Maybe we'll touch base at
> SIAM next year in Evansville?
>
>
>
> Larry
> ---- Dave Rotigel <rotigel at me.com> wrote:
> > I'm with you on this Charlie. I was lost right after Larry said "All
> > kidding aside…." I can't get to Portersville this year, but looking
> > forward to the "live demonstration" when it happens.
> > Dave
> >
> > On Jul 13, 2015, at 10:09 AM, charlie hill wrote:
> >
> > > Larry,  I understand how you are tracing the irregular area with the
> > > secondary knife blade but
> > > how do you allow the main knife blade to behave as you trace?  Do you
> > > keep
> > > it perpendicular to
> > > the straight line?  I don't understand at all.   There are multiple
> ways
> > > it
> > > could wander including
> > > at random if not controlled some way.  What am I missing?
> > >
> > > Charlie
> > >
> > >
> > >
> > > -----Original Message-----
> > > From: rlgoss at twc.com
> > > Sent: Monday, July 13, 2015 9:40 AM
> > > To: Antique tractor email discussion group
> > > Subject: Re: [AT] OT pocket knives
> > >
> > > !!!Dave, All kidding aside, a tape measure is exactly how you get the
> > > answer
> > > out of measuring an area with a make-shift planimeter. You start
> tracing
> > > an
> > > area with the main knife blade resting on a straight line that is 
> > > drawn
> > > outside the area you want to measure.  When you come back to the place
> > > on
> > > the irregular outline where you started, you measure the perpendicular
> > > distance to the straight line. That distance multiplied by the 
> > > distance
> > > between the contact point on one blade and the tip that you use as a
> > > tracing
> > > pin is a direct read-out of the area. The next time I run into you at 
> > > a
> > > show, I'll give you a live demonstration.  I'm headed to Portersville
> in
> > > a
> > > little over two weeks.  Are you going to be there?
> > >
> > >
> > > Larry
> > > ---- Dave Rotigel <rotigel at me.com> wrote:
> > >> Darn, That's NEAT! I use a tape measure in a similar way!
> > >> Dave
> > >> PS, Kidding aside, THAT'S NEAT!
> > >>
> > >> On Jul 12, 2015, at 11:02 AM, rlgoss at twc.com wrote:
> > >>
> > >>> I sold both of the polar planimeters I had in our garage sale
> > >>> yesterday.
> > >>> They were perfectly  good instruments, but technology has left them
> > >>> behind. That fact plus this thread brought to mind that I have
> carried
> > >>> a
> > >>> two-bladed pen knife for many years specifically because you can use
> > >>> it
> > >>> as a planimeter in an emergency by opening the large blade 
> > >>> completely
> > >>> and opening the smaller blade to approximately 90 degrees before
> > >>> starting a tracing. It gives a measure of irregularly-shaped areas
> > >>> that
> > >>> is better than estimations and requires minimal instruments.  You do
> > >>> have to keep the blades sharp so they don't slide sideways over the
> > >>> map,
> > >>> and they need to hinge at opposite ends of the knife.
> > >>>
> > >>>
> > >>> Larry
> > >>> ---- jtchall at nc.rr.com wrote:
> > >>>> Just an update: I bought my son a single blade Case with a
> > >>>> plastic/composite
> > >>>> handle. The knife has a lockback design. After reading your posts 
> > >>>> it
> > >>>> seems
> > >>>> quite a few folks are using single blade knives instead of the 2 
> > >>>> and
> > >>>> 3
> > >>>> blade
> > >>>> knives I carry. I carried him to 3 stores and we tried several. 
> > >>>> This
> > >>>> one is
> > >>>> fairly easy to open and close, yet the blade is never in a "free"
> > >>>> rotating
> > >>>> state. Some of the easy opening ones seemed to me they could open 
> > >>>> in
> > >>>> your
> > >>>> pocket. The blade is about 3-3.5 inches long and the knife is big
> > >>>> enough to
> > >>>> get a really good grip on. The handle is also textured. The Kershaw
> > >>>> and
> > >>>> Gerber knives some of you suggested were out of stock actually.
> > >>>> Anyway
> > >>>> he
> > >>>> seems pleased and has used it the last couple Saturdays around the
> > >>>> farm.
> > >>>>
> > >>>> John Hall
> > >>>>
> > >>>>
> > >>>>
> > >>>>
> > >>>> _______________________________________________
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