Foliot Clock

I built this wooden clock around 1965. I made it mostly made from walnut. It's a copy of an original 13th century clock I saw in a museum in Quebec City, Canada. I took some photos and made sketches and notes which I used to design the parts of this clock. Clocks of this style are called Foliot Clocks. The folio is the horizontal bar which oscillates back and forth through an angle of about 60 degrees.

As you can see from the photos, it has only an hour hand. Minute hands didn't appear on clocks until a couple of hundred years later than the original era of this style of clock.

The clock is driven by the decending larger weight. The smaller weight just keeps the cord seated in the pulley groove and creates enough friction force to keep the cord from slipping. The weights are just traditional lead fishing weights "antiqued" by tapping on them with a ball peen hammer.

A verge escapement gets its timing from the rotational inertia of the oscillating foliot which gets accelerated and decelerated by the clock's driving force. The clock's rate is adjusted by moving the pair of lead filled wood weights in and out on the arms of the foliot.

My clock keeps pretty poor time, mostly due to the "verge" escapement and the folio bar which are strongly affected by friction and also by the driving force. The clock's rate changes almost directly with the driving force.

To make things worse, the driving force increases slightly as the clock runs down as more of the weight of the cord supporting the larger weight gets added to that weight (and subtracted from the smaller weight). This causes the clock to speed up. Yes, I thought of adding a loop of cord hanging below the weights to cancel out that effect, but the originals weren't built that way, and it would have looked sort of stupid anyway, so why change things?
 
 

In 2001 I was chagrined when my son showed me an advertisement from a 1972  LIFE magazine featuring a $6.98 plastic model kit, which looks as though it could have been copied from the same clock as the one I modeled mine from.

 

Jeff Wisnia