NavList:

It only effects the useful load of the plane.

My original re-creation weighs 5.98 oz (169.5 gm). My HR-1 recreation weighs 21.94 oz (622.0 gm). The cotangent tube, including the locking mechanism, weighs 15.16 oz (429.8 gm) and the cosine tube carrying the clear plastic cursor tube weighs 6.78 oz (192.2 gm.)

There are two ways to utilize the locking mechanism. You can line up the cotangent value with the cursor and then turn the locking knob one-quarter turn to lock the two tubes solidly together. Or you can just tighten up the knob just enough to provide sufficient friction to allow you to move the tube which also provides enough friction so that the tubes will stay in position without further tightening up the knob. This second method is the easier method.

gl


Wolfgang Hasper wrote:

Wow!!

Gary, you mention the weight is a lot higher compared 
to your earlier attempt-
does this fact affect the handling significantly? Or 
does it just reduce the payload of your plane...?

Wolfgang


Am Montag, 18. Januar 2010 12:59 schrieb Gary LaPook:
  

I wrote back in July about my plan to make a working
model of the HR-1 German model of the Bygrave slide
rule using off-the-shelf items to make the locking
device that sets the HR-1 apart from the Bygrave.
See my prior posts at:


http://www.fer3.com/arc/m2.aspx?i=109056&y=200907

http://www.fer3.com/arc/m2.aspx?i=109993&y=200909

I have now accomplished my goal. I have attached
twenty eight photographs showing how to do this, but
read my prior posts before going further.

Going in numerical order, the first two photos show
the 1.500 inch outside diameter tube that I have
used for my prior Bygrave re-creations cut off to
ten inches that will be used to mount the cotangent
scale.

The next photo shows the locking mechanism I had
described in my prior posts along with the cotangent
tube and a piece of PVC pipe cut to fit inside the
cotangent tube to take the compression load of the
locking mechanism.

Photo four shows the locking mechanism with the PVC
pipe in the assembled position.

Photos five, six and seven show the same now
installed inside the cotangent tube.

Photo eight shows a detail of the expanding ring
that is used to lock the two tubes together.

The difficulty in making this is finding tubes that
are a good tight fit. I found aluminum tubing used
for making antennas at:

http://www.dxengineering.com/Products.asp?ID=278&Sec
ID=136&DeptID=43

They have tubing with an outside diameter of 1.625
inches and a wall thickness of .058 inches making
the internal diameter 1.519 inches, a good fit on
1.500 inch O.D. tubing. If you could print the
cotangent scale directly on the 1.500 tube this
would be a good solution but my method requires me
to print the scale on paper and mount it on the tube
under a plastic sheet for protection making the
diameter of the cotangent scale 1.520 inches, too
large to fit inside a tube of this size.

The next largest size of tubing in 1.75 O.D., 1.634
I.D., too large for a good fit on the 1.520 diameter
cotangent scale.

http://www.dxengineering.com/Parts.asp?ID=2413&PLID=
278&SecID=136&DeptID=43&PartNo=DXE-AT1251

Photo nine shows this tubing in line with the
cotangent tube.

Photo ten shows my solution to this problem. I
decided to bush the inner tube out to fit closely to
the cosine, outer, tube. I used five sheets of
regular paper, 8.5 by 11 inches (standard paper size
in the U.S.), glued with rubber cement (which has
the advantage, that if you need to start over, the
glue will come off easily) totaling 55 inches
wrapped around the tube. The paper is .004 inches
thick and the five sheets brought the diameter close
enough (considering that the cotangent scale and the
plastic sheet would be placed around it) to make a
good fit to the cosine tube. Since I wanted to seal
the scale from the environment, prior to putting the
paper on the tube, I used several sheets of the
sticky plastic sheets cut into 1/4 inch wide strips
to wrap around the tube near the top to bring the
diameter out far enough that the plastic sheet
mounted on top of the scale would stick to these
layers of plastic thus sealing off the top of the
tube and the scale. After mounting the paper I did
the same thing at the other  end of the paper this
time using 3/4 inch wide strips.

Photo eleven shows the cotangent scale and photo
twelve, thirteen and fourteen shows th scale mounted
on top of the paper on the cotangent tube and
covered with the protective plastic sheet.

Photos fifteen and sixteen show the cosine scale
mounted on the larger tube and covered with a
plastic sheet. Photos seventeen and eighteen show
the cotangent tube being inserted inside the cosine
tube.


Making the cosine scale presented a bit of a
problem. Since the cosine tube has an O.D of 1.750
and the cotangent scale was only 1.520 inches in
diameter it was necessary to print the cosine scale
at a larger scale than the cotangent scale which was
not a problem using Acrobat. However when I tried
out the scales a problem presented itself. My
printer made the cosine scale wider but also taller
so that the pitch of the scales no longer matched.
Although it worked this way it caused ambiguity
since the cursor would sometimes end up between
spirals on the cotangent scale and either answer
(higher or lower than the end of the cursor) could
have been the correct one. I contacted Dave Walden
(the original source for the scales I have been
using) and he was able to modify the vertical and
horizontal ratios of the cosine scale so that, when
printed out wide enough to fit around the tube, the
vertical spiral pitch matched the cotangent scale.
(Thanks again Dave.)

Photos nineteen and twenty show the two cursors, the
cosine cursor pointing to zero and the cotangent
cursor on 76 degrees. I again made the cursor  out
of clear plastic by first printing the instructions
on a sheet of paper, drawing in the cursors and then
photocopying this onto a clear plastic sheet made
for use in an ink jet printer. I then wrapped it
tightly around the cosine scale and held in that
position with two pieces of scotch tape on the
inside of the cursor tube. I then wrapped a sticky
clear plastic sheet around it to protect the
printing on the cursor tube and to hold it in shape.
I then removed the scotch tape.

Photo twenty-one shows the condensed instructions
printed on the cursor tube. The cosine scale is
white underneath this section of the cursor tube to
enable easier reading of the instructions.

Photo twenty-two shows the "zig-zag" printed on the
cursor tube which lines up with the two cursors to
guide the user through the computation.

Photo twenty-three and twenty-four show close ups of
the cursors pointing to zero on the cosine scale and
76° on the cotangent scale.

Photo twenty-five shows the cursor pointing to 76°on
the cotangent scale.

Photo twenty-six shows the tubes extended so that
the cotangent cursor can point at 55'.

Photo twenty-seven shows a close up of the cursor
pointing to 55' at the bottom of the cotangent
scale.

Photo twenty-eight shows the tubes collapsed.

Turning the wing-nut (control knob) one quarter of a
turn locks the two tubes together and is an easy
manipulation to make. Since the cosine tubing is
only .058 inches thick the cosine scale and the
cotangent scale are very close together, and to the
cursor, minimizing any parallax problem when reading
the scales.

I have also attached the modified cosine scale and
note that the tick marks go down from the line under
the numbers. The cotangent scale is made with the
scales posted last March bt Dave Walden for the flat
Bygrave at
http://fer3.com/arc/img/107501.f2-lapook1.pdf

Also attached is the form for the cursor tube.

The only downside to this model, compared to the
prior model I made of the Bygrave, is that it is
three times heavier since the locking mechanism and
the cosine tube each weigh as much as my original
re-creation of the Bygrave.

I demonstrated this HR-1 to Frank, Mike and Greg
prior to our flight last Saturday.
gl