Posted by Rob (208.17.229.201) on November 18, 2002 at 11:33:33:
In Reply to: Re: Das Triumphirende Perpetuum Mobile Orffyreanum posted by JOHN on November 17, 2002 at 17:46:00:
As far as grindstones go, I'll have to do some research, but some small old footpowered stones that I've seen are deliberately created eccentric - with the pivot hole off-center, which would produce a variation in rotational speed. I've often wondered why?
: Hi there, as I understand it ... a horizontal axle with an inner(or 'lower')wheel, ie: a heavy smaller diameter grindstone mounted through its middle on the horiz axle, giving the part of the wheel providing the drive(axle)smooth torque and lots of mass(flywheel effect). the outer wheel is the opposite ie: as light as poss(and well balanced) as it only has to do the 'tipping' or 'lifting' control. It is curious to note a report that the wheel was noted by one very sharp eyed observer(an artist)to not spin its full rotation at the same smooth speed, but allmost imperceptibly slowed or 'backed' momentarily a regular interval around the turn, I wonder if the suggests a timing machanism(poss related to the pendulum thing?)alternating resistance controlling the synch between the inner grindstone and the outer 'visible' wheel? etc..... questions questions....
: : Am I correct that the "lower cylinder" in the translated line: "Around the firmly placed horizontal axis is a rotating disc (or lower cylinder) which resembles a grindstone" is referring to the cloth covered wheel? If so, the wording "lower cylinder" would seem to indicate, or imply that there was also an "upper cylinder". If not, why put the word 'lower' in the description? Does anyone have any thoughts on this?
: : The third line of the same paragraph: "Accordingly, this wheel consists of an external wheel (or drum) for raising weights which is covered with stretched linen" refers to an external wheel. This seems to imply that there was an internal wheel. Again, if not, why put the word external in the description?