# NavList:

## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

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Re: recommendation for slide rule ? Bygrave
From: Gary LaPook
Date: 2009 May 22, 00:35 -0700

```I used to make special use slide rules. The first two pictures show one
made to calculate miles per gallon. It was simple to make, just cut
pieces of logarithmic graph paper, label the lines, and then mark an
index pointer. The picture shows that using 8 gallons to go 200 miles
shows you getting 25 miles per gallon.

The second slide rule calculates kinetic energy of a bullet given the
weight in grains and the velocity in feet per second, the K.E is
calculated in foot-pounds. You set the index on the weight, 220 grains
in the picture, and you can read out the K.E. aligned with the velocity,
e.g. 220 grain bullet traveling at 2500 feet per second results in a
K.E. of 2900 foot-pounds. Since the K.E. varies with the square of the
velocity I used two kinds of logarithmic graph paper, one having one
cycle and the second having two cycles. The velocity in on the one cycle
paper and the scales for weight and K.E. are on the two cycle paper.
Doing it this way the slide rule automatically squares the velocity. I
taped an extension to the velocity slide to allow for velocities below
1000 feet per second.

gl

James N Wilson wrote:
> Make your own slide rule? Been there, done that. The attached was made
> in 1945, and it would be a few years before I could afford a Dietzgen
> Maniphase Multiplex, which I still have. I've been fascinated by the
> discussions, remembering well the days when that was /the/ way. I'm
> very interested in the application to sight reduction. I always
> thought that the accuracy wasn't good enough.
>
> Jim Wilson
>
> >
>
> ____________________________________________________________
> Get a life insurance quote online. Click to compare rates and save.

>
>
> ------------------------------------------------------------------------
>

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