On the Fly tuning

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>" <A123X-at-aol-dot-com>

I was testing my coil with my new "plate" caps. The base of the primary only 
had two holes for tuning drilled in it because I didn't need to tune to any 
less than 13-14 turns. With the new 15nf tank cap tuning is appearently at 
several less turns. Anyway to try to achieve tuning I layed a peice of copper 
pipe across the primary. If I moved it in or out it would bypass different 
turns tapping it at different points. I was wondering if using something like 
this on a plastic roller attached to a small DC motor could be used for on 
the fly tuning? Would this cause a lot of metal sparks?   
Just a thought, I really don't have a big problem with unplugging it to tune 
each time.