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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

   

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