Debugging (Part 1)

With the completion of the pendulum, the clock at least runs for a while.  But it always seems to stop.  There are a number of possible points of failure:

1. Gear profiles not cut perfectly
2. Not enough or too much drive weight
3. Not enough or too much pendulum bob weight
4. Design flaw -- especially in the escapement.
5. Too much friction, somewhere in the mechanism

So with all of these possibilities, it is reasonable to try to break things down a bit.  I started by observing many, many runs.  It seems like there are three modes of failure:

1. The escapement stops getting driven.  In particular, one of the escape wheel teeth falls off the anchor and (usually) gently comes to a stop.
2. The anchor hangs up on an escape wheel tooth (which is clearly still pushing)
3. The anchor slips on its arbor, and therefore is out of alignment (less common)

The first of these seemed most serious.  Poking at things carefully, it looked like the third wheel arbor was binding on its pinion.  So, I removed the pinion and started filing teeth, to give it some more space (hint: this isn't a good idea)

After getting all six teeth, the profile changed like the one at the left in the picture below to the one on the right (arrow).

This didn't seem to fix anything, and indeed, made it worse.  So I just cut a new pinion from scratch.  That seemed to help solve the escape wheel losing power issue -- but not completely.  I'll come back to that later, I imagine.

So I decided to switch to the other major problem -- the point where the anchor gets hung up on the escape wheel.  This seemed to be a drive power issue, and possibly an anchor design flaw.  To test this, I removed the center, third, and ratchet wheels from the frame.  I attached a cord to the fourth wheel pinion with a plumb bob.

Still, the mechanism stops, so I suspected the problem was isolated to just this.  I've been concerned that the anchor requires too much lift, so I filed back the anchor teeth a bit.  Of course, I now realized that if I didn't like the result -- like the third wheel pinion -- I'd be making a new anchor.

But now, the mechanism seemed a bit closer to running.  And indeed, with quite a lot of weight it runs.  Specifically:

• With 7.5 oz on the fourth wheel pinion, the mechanism slows to a stop
• With 11.5 oz on the fourth wheel pinion, the mechanism runs
• With 1 lb 3 oz on the fourth wheel pinion, the mechanism runs, and can even tolerate the pendulum getting bumped a bit.

That's far more weight than I wanted to need at that point in the train.  Indeed, that would require some 35+ pounds on the actual drive pulley.  Really, I'd like only about 1-2 oz to be needed on the fourth wheel pinion to drive the mechanism.

Since there's not a whole lot of friction in the pivots, I suspect the right course of action is to try to reduce the lift on the anchor a bit more...