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Re: HR-1 working re-creation
From: Wolfgang Hasper
Date: 2010 Jan 18, 20:34 +0100
From: Wolfgang Hasper
Date: 2010 Jan 18, 20:34 +0100
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