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Revisiting the Do-Nothing Machine one more time – The most critical part.

The Working Painted Do-Nothing

During the final final fit of the Do-Nothing Machine I ran into a few more problems. Like always, I eventually worked through the problems and also like always I learned something.

To “honor” the political season getting kicked off this week I decided to paint the Do-Nothing Red White and Blue. The two shuttles are painted red and blue because these colors  have become the way our media refers to the two political parties.  (i.e. the red states and the blue states).   Painting turned out to not be a good idea.  I am not sure if it was just the thickness of the paint, or the fact that it was water based, but the shuttles no-longer fit into the groove.  After some whittling & sanding, I finally got the shuttles to slide easily in the grooves, but when I put the handle on it all seized up again.   I thought maybe the problem was the paint on the handle catching on the threads of the machine screws.  I reamed the holes where the shuttle screws fit into the handle and it seemed to seize even more.

The binding of the shuttle

Finally, I looked at the end of the groove at the shuttle and determined the problem.  The shuttle was rotating in the groove and was wedging itself between the two walls of the groove.  My first thought was to work on the shuttle some more, but then I realised that if the shuttle was rotating the screw as also moving in the hole in the handle, because the screw is tight fitting in the shuttle. It was now obvious why making the hole in the handle made the problem worse.   At that point I decided to use a thicker piece of wood and made a new handle.  The original handle was a 7/16″ square dowel rod and I made the new one out of 1/2″ square dowel.  I carefully drilled the holes straight and made a tight fit on the screws.  The machine works well now.

A plan view of the machine.

I became curious as to why this binding always seemed to occur as a shuttle was at the end of the stroke.  The plan view of the machine explains this. At the point shown on the diagram the handle will be twisted either straight upward or downward.  All of the force on the middle shuttle in that case is in the Y direction yet the shuttle can only move in the X direction.  This is really a case where the math and the models fail us.  There is no force vectors anywhere in the horizontal direction, yet we are expecting things to move sideways.  Things have to move sideways!

The only way we can understand this mathematically is make the handle just an very small amount off the zero degree line. Anything other than that puts us in either a multiply by zero or divide by zero situation and those “blow up” in mathematics.

Physically, the only way this machine can operate is if the shuttles are not binding at all and that can only happen if the handle is holding the shuttles in alignment.

Conclusion: — The hole alignment in the handle is the most critical dimension on the whole machine.

Sooner or later, I am going to have to completely model this machine and really think about the what it is telling me.   The Do-nothing has caused me to have to do a lot.



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