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Remember to allow for the thickness of the paper carrying the cotangent
scale and the plastic covering it in figuring the clearance between the
tubes and so the proper sizes for the tubes. Measuring the scale on my
first reproduction of the Bygrave it is 1.516 ~1.520 inches in diameter
mounted on  a 1.500 inch tube so the scale takes up about .020 inches of
clearance between the tubes, about .5 mm.

gl


Wolfgang Hasper wrote:
> Since we come back to the tubes time after time
> I am interested to find out how many would like to make
> an actual reproduction on reproduced tubes?
>
> The HR1 uses Aluminium tubes
>
> (all dimensions [mm])
>
> inner tube    54x1        235 long
> interm. tube  58x1        225 long
> outer tube    62x1        222 long
>
> A kit of all three sizes 300 long each would be nice.
> Narrow tolerances are required for the outer diameters
> to fit the scales, the inner diameter is less
> important. If there is a felt lining as on the
> original you can easily compensate for 0.2 mm.
>
> Aluminium as the material seems preferable but not
> compulsory. I would not like to have stainless steel,
> it is heavy and a pain to machine.
>
> To investigate the local possibilities for custom tubes
> I have started with a firm that works with perspex.
> Maybe plastic is more realistic to have in custom
> dimension than aluminium? We'll see.
> I will try on aluminium tubes also.
>
> If Douglas is successful earlier it will be even
> better, maybe we can get two independent quotes.
>
> How many on the list would be interested in how many
> kits?
> If you want I could compile a list of all interested so
> we know how many metres we will have to order ;o)
>
> Wolfgang
>
>
>
>
>

   

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