>Hello Dale,
  >What protects the inner tube from the Sheet metal screws?
Mr. Tuffy's will work, also old clincher road tires with the bead cut off
make a good barrier.  Another thing you can do is to use carbide tipped
studs (the small ones for car tires) instead of sheet metal screws.  The
car studs last longer (much longer) and actually seem to become sharper as
you use them.  I've got a pair I made five years ago that are still working
great and no where near being spent.  Here in Vermont they get plenty of
use too.
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