[Rhodes22-list] Compasses

[Steve Alm]

Step one checks out.  I took a full sheet of newspaper and creased it in
half both ways and diagonally and drew lines with a straight edge.  Since my
compass is still mounted on the splash board, it's an easy and sure way to
line the board up on the lines on the paper.  I laid the newspaper out on my
wooden dining room table and went to work on the adjustments. After about 35
minutes of fiddling, I got it to be consistent on all lines (8 positions) to
within a half of a degree.  Then I repeated the test in other rooms of the
house and basement and out on the front walk.  Results were consistent, so
my compass is working.  However, I always thought my house and the street in
front ran exactly north and south but the compass is saying it's a few
degrees off.  And maybe the street isn't exactly north and south but I don't
have a second compass to cross reference.  I have a couple small hand-helds
on the boat but not here at home.

Slim

On 4/8/05 11:32 AM, "Bill Effros" <bill at effros.com> wrote:

> Slim,
> 
> From comments sent previously, you can infer the problems manifest in
> all compasses: they will all kick out numbers, but there is no fixed
> relationship between any two numbers until you discover what that
> relationship is.
> 
> Let's start with your compass.  First rotate it 360°, slowly.  Is it
> capable of stopping at any number?  If the magnet has been badly
> damaged, it will jump over some numbers, no matter which way you point
> it.  If that's the case, you will not be able to use this compass
> because you will never be able to find another compass that makes the
> same mistakes in exactly the same way.  Consistency is the critical
> function of any compass.
> 
> Assuming that your compass is capable of pointing in 72 different
> directions (5° intervals) you must next determine if it is consistent.
> Point the compass so it reads 0°.  Make a line in the sand.  Turn the
> compass 180°, and write down what number the compass points to.  Turn it
> back to 0° using your line in the sand.  Does it say 0°?
> 
> Please note, if the compass is working properly, the compass card should
> not move at all -- only the housing and the board you may have mounted
> it on should move.  It may not be pointing in a predetermined direction,
> but it should be pointing in the same direction all the time.  That's
> the way properly functioning compasses work.
> 
> Using a protractor, draw a line in the sand at a 90° angle intersecting
> your first line.  Put your compass on this new line, first one way, then
> the other.  It should read 90° and 270°.  If it doesn't, you've got a
> problem.  Make more lines at 45° angles.  The compass card should not
> move.  Your computed angles should equal what you see on your compass.
> 
> If they do not, someone may have "corrected" your compass.  The
> adjusting magnets, built into the housing of your compass, must be
> pulling your compass card in different directions as you rotate the
> housing around your compass magnet. Try to twiddle with them, so that
> they don't change the orientation of your compass card when you rotate
> them around.  If you can't make this happen, it's time for a new compass.
> 
> If your compass is consistent, it's time to mount it on your boat, and
> figure out what direction it's actually pointing.
> 
> Timid Virgins Make Dull Companions.  Lesson II.
> 
> Bill Effros
> 
> 
> 
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