Re: [ATM] LWT setup questions

["john sherman" <atm@mail.johnspics.com>]

Hi Bernard,

>thinking about modifying my existing Foucault tester to allow
>it to perform the lateral wire test as well. 

I made a tester from scratch, instead of messing with an existing tester. You just need a dial indicator mounted sideways on a scrap piece of wood. Now mount a bolt which bears on the dial indicator's plunger and pushes it in and out. I filed the end of my bolt flat, and tapped a hole in the wooden tester stand. The non-lasing, un-lensed laser went into a drilled hole. A small wire/hair holder mounts onto the plunger of the dial indicator. Someone once did a much better job of describing it for the list, so that would be in the archives. 

The inventor of the LWT, John Francis, once had several pages of website, two of which got moved to http://hometown.aol.com/julesfran/ which answers some of your technical questions. Also, there are others on this list who are much better equipped to answer the hard questions than I am. 

>- I assume they can they can be made to move laterally together

Mine didn't, the light was mounted under the wire near the center of its movement. I think you can, but since the movement of the wire wasn't a quarter-inch, it probably doesn't matter much. 

>current one limited to 0.01mm (0.0004")?

On his website, Francis points out that since there is such a small movement of the wire, he recommends an indicator that can read 0.0001". But you should be able to use yours to play with. With my set-up, using a strong magnifying glass, I found I could start and stop the needle's movement ten times between each division marked on the scale. With similar care, you could probably use your current indicator to make a fine mirror.

My first wire-carrier was only made of cardboard, but actually worked! It is easy to carve a small C-shaped piece of wood to hold the wire. A hole in the bottom of it allows press-fit onto the plunger. If the lightsource was also on the plunger it would provide resistance to smooth movement, that's why I put it underneath. 

Good luck!

John









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