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    Re: Bygrave and MHR-1 locking mechanism construction
    From: Wolfgang Hasper
    Date: 2009 Oct 1, 20:19 +0200

    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---.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 --~--~---------~--~----~------------~-------~--~----~ NavList message boards: www.fer3.com/arc Or post by email to: NavList@fer3.com To unsubscribe, email NavList-unsubscribe@fer3.com -~----------~----~----~----~------~----~------~--~---

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