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Gary,
thank you for your reply to my earlier question and those most interesting 
experiments.
I am courious to learn about your results:
Does the tightening torque affect the alignment, is a 90� turn sufficient..?

I myself will shortly start some experiments on tube-making to custom 
diameters which -given the results were positve- might solve that cumbersome 
problem. My idea is to use a bending apparatus to bend pieces of various 
materials to form my own tubes. This should be possible with sheet metal the 
seam then soldered/brazed/welded, plasic (in heated state) with the 
advantages of low weight, no corrrosion, cheap price, easy to glue and 
possibly even with cardboard.
I have a printer that is ready to print on cardboard up to 1 mm thickness.

Maybe it is even possible to first print/engrave scales onto flat (plastic) 
material and then bend it...
Should that work it seems promising to use this
http://www.gravograph.com/english/engraving-products/gravoply_ultra.php
Since it can be laser-engraved any design could be realised easily.

THe experiments will take some time, just too busy right now.
I will report as soon as results are ready.

Wolfgang








Am Mittwoch, 30. September 2009 03:55 schrieb glapook@pacbell.net:
> In the past we have discussed the superiority of the MHR-1 to the Bygrave
> due to its mechanism for locking the two tubes together to prevent unwanted
> movement while resetting the cursor. See prior posts:
>
> http://www.fer3.com/arc/m2.aspx?i=109049&y=200907
>
>
> http://www.fer3.com/arc/m2.aspx?i=109054&y=200907
>
>
>
> I have made several copies of the Bygrave using as its base a 1.500 O.D.
> standard sink "tail pipe" or drain pipe twelve inches long on which to
> mount the cotan scale.  See my prior post on this:
>
> http://www.fer3.com/arc/m2.aspx?i=108949&y=200907
>
>
> I have also suggested in the past that a three and a half buck off the
> shelf "test plug" might be the basis for a locking mechanism, see:
>
>
> http://www.fer3.com/arc/m2.aspx?i=109056&y=200907
>
> The problem with making a copy of the Bygrave or the MHR-1 is finding tubes
> that are close enough in size to provide the proper sliding fit. My cotan
> scale is printed on paper and wrapped around the 1.500 inch O.D tube and
> then covered with a clear plastic sheet expanding the diameter to 1.520
> inches. I measured the I.D of standard one and a half inch PVC pipe and
> found it is 1.566 which is a good fit and within the range of adjustment of
> the "test plug." So today I decided to give it a try. I purchased a piece
> of such pipe, a piece of 5/16th inch threaded rod, a 5/16 inch nut, a
> 5/16th inch self locking nut, and another test plug, about ten bucks. The
> original bolts in the test plugs are 5/16ths.
>
>
> The attached pictures shows the process. Disassemble the two test plugs and
> use the two smaller plastic pieces, one of the large pieces, one of the
> rubber rings one of the washers, and one of the wing nuts. The other pieces
> are not used. The small plastic pieces are designed to use carriage bolts
> so have square sockets for the heads of the carriage bolts. Modify one of
> the small plastic pieces by opening up the square socket to allow the use
> of a normal hex nut (or modify a nut to fit in the existing square socket.)
>  Tilt the unmodified small plastic piece and you can insert it into the end
> of the cotan tube. Straighten it out and position it so it protrudes from
> the end of the cotan tube. Cut a piece of one inch PVC pipe a little bit
> shorter than the cotan tube and put it inside the cotan tube. This is to
> prevent the plastic piece from being drawn into the tube under tension. Cut
> the threaded rod so that it will go through the tube and protrude out the
> end. Put the wing nut on the rod and place the self locking nut on the rod
> and twist them together to lock them solidly to the rod, "double nutted."
> Place the rod though the washer and then through the large plastic piece
> and slide this whole assembly through the tubes so that the rod protrudes
> from the other end. Place the rubber ring on the rod followed by the
> modified small plastic piece and a regular nut. Turn the rod using the wing
> nut to tighten up the whole thing. Now slide the one and a half inch PVC
> pipe over the assembly, tighten the rod and it locks the two tubes
> together.
>
> I  have not yet made the cosine scale to go on the one and a half PVC pipe
> but that should not be a problem. I plan on making the same type of cursor
> using clear plastic sheet. The only thing I don't like about this is the
> PVC pipe has a thick cross section and I will continue to look for a
> thinner piece of tubing with the same I.D. to eliminate the parallax
> problem with the cursor so far away from the cotan scale.
>
>
> gl
>
>
> 
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-- 
Wolfgang Hasper
Beckstra�e 87
64287 Darmstadt
06151-4289333

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