NavList:

I measured the 2 and 3 inch plugs. The cam shaped plastic base for the two inch plug is 47.46 mm in diameter and the rubber friction ring adjusts to cover the range of 48.68 to 51.56 mm. For the three inch plug the measurements are 69.96, 70.13 and 81.12 mm respectively.

gl




Gary LaPook wrote:

In deciding the size of tubes to procure for making reproductions I would like to suggest you use tubes similar to the ones I have used. The cotangent tube is 1.500 inches O.D, (38.18 mm), 1.460 in. I.D (37.74 mm) I.D. The locking mechanism's rubber friction ring adjusts from 1.482 in. to 1.680 in. (37.6 to 42.7 mm) so a cosine tube with an I.D. in this range can be made into a reproduction of an HR-1 as well as a Bygrave. The I.D. of my cosine tube is 1.634 in. (41.5 mm) so works well but I would like to find a tube that was more close fitting to the cotangent tube and scale, 1.520 in. (38.46 mm). The off-the-shelf components I used for my locking mechanism also comes in larger sizes, 2, 3 and 4 inch ( 51, 76 and 102 mm) models so would fit tubes with I.D.s approximating those sizes so picking such tubes would also allow the option of making an HR-1 reproduction too.

gl



Hein Bodahl wrote:

My apologies for going off topic.
I renamed my answer from "[NavList] Re: Cylindrical Slide Rule tube poll"

I have read the posting earlier and the version you describe is of
course the inspiration for my idea. However it seems to me that the
described version still would suffer from the problem of locking the
scales while resetting the cursor. Mine would on the other hand, not be
collapsible.

Also, using shrink wrap tubes would eliminate the problem of "snagging"
along the seems.
The cursors printed on transparency sheets, laminated for stiffness.
Properly cut and shrink wrapped around the tube I believe that it could
make a better transparent outer tube than the adhesive pouch solution.
Accurate cutting could possibly ensure proper friction.

The simple beauty and extraordinary easy production and storage of your
flat Bygrave is unfortunately slightly inhibiting of actual prototyping :-)

Hein

On 21.01.2010 13:01, Gary LaPook wrote:
  

See:

http://www.fer3.com/arc/m2.aspx?i=108949&y=200907

gl
    

Hein Bodahl wrote:
    

I have been thinking about using a 50 or 75mm drain pipe and fixed
scales.
Around that I would shrink wrap a movable cursor for the cos scale. This
transparent wrap, lined to avoid undue friction, would also cover the
cotan scale.

Around the wrap covering the cotan scale I would wrap a second, movable
cursor for the cotan scale. This second cursor would then move in
conjunction with the cursor for the cos scale, once set, avoiding the
locking problem.