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Hey Jeff,

How's it going buddy?

If it were me, I would look at making it a simple as possible; a 
hand-held lens, only adding some kind of restraint if it were absolutely 
necessary.

(Exhibit Aphorism 6 of spades "Sufficient ruggedisation of loose parts 
turns them into weapons" courtesy of Harry White's collection of Exhibit 
Aphorisms)

But since you say you 'need' a two axis slider, I might forgo the linear 
bearings and use drilled blocks of nylon or Delrin as your bearings. 
They would have sufficient slide with enough built in friction. Linear 
bearings can be fussy - and expensive. McMaster also has a ton of decent 
busings which work surprisingly well, and in a way are much more 
suitable for exhibit use (low speed and relatively high off axis and 
awkward loads.) Of course, only a little experimentation would answer 
all your questions.

Keep it simple, buddy - I'm sure Harry has an aphorism in his deck for 
that one, too

Joe R.
www.TheExhibitGuys.com


Jeff Courtman wrote:
> ISEN-ASTC-L is a service of the Association of Science-Technology Centers
> Incorporated, a worldwide network of science museums and related 
> institutions.
> ***************************************************************************** 
>
>
> I need to build a 2 axis slider to move a magnifying lens around a 
> large graphic (think of 'where's waldo').  I plan on using linear 
> bearings and wanted to know from those of you with experience what 
> might be the best way to control the friction in the movement (so an 
> over-exuberant 7 year old, like my son) can't wind up and sling it 
> from one side to the other.....
>
> Thanks in advance,
>
> Jeff
>
>     
>
>
>
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