Tuesday, October 27, 2015

Pumpkin carving tool

Here's a tool I made for carving pumpkins this year...

It's an old scroll saw blade set in a wooden handle with one of the ends ground to a piercing point.

Thursday, October 15, 2015

General Electric model 352 clock

My parents had a clock that sat on their mantle and chimed every quarter hour with the Westminster quarters.  I remember it clearly as a child, and always liked the clock.  It's been in the family since my great grandmother bought it for her apartment in New York City.  My father also remembered it as a child.

The clock ran for many years until finally running into problems.  My father traced the issue to the motor, and tried to open it to see what was wrong.

The teeth of the wheels inside the motor had rusted and stripped, which clearly wasn't going to be easy to fix.  Apparently, my great uncle Gus had planned for this eventuality and had another motor ready.  However, the motor was the wrong type (model H3 instead of B2) -- both a different speed (3.6 Hz instead of 1 Hz) and different size -- but with auxiliary gears the speed was remedied.  My father installed a pair of wooden blocks to fit the new motor, and the clock ran for a few more years.   But this eventually failed, and the clock remained silent.

Recently, given my developing interest in clocks, my parents brought the clock to me to see if I was interested in fixing it.  Upon examination, I realized a number of things:
  1. The clock was a General Electric model 352, and there was a bit more information on this page.
  2. Based on the serial number 283845, this page claims the clock was built between 1935 and 1939.
  3. The motor was a Telechron B-2 motor.  Surprisingly (at least to me), refurbished motors are both available and reasonably priced!
So I purchased a replacement motor, which arrived a few days later.

It also was immediately apparent that the clock had not been cleaned in a long while -- the oil had long since gone bad, and the pivots were thick with black oxidation.  (Or, as my father notes, possibly oil mixed with cigarette smoke...  Unpleasant in either case.)

I carefully disassembled the entire mechanism, and grouped the parts based on where in the disassembly sequence they appeared.  And then spent an entire day cleaning.

Since nearly everything was brass and heavily oxidized, I cleaned each part with Brasso before an ammonia soak, a hot soapy ultrasound bath, and a rinse.  In  some cases, multiple repetitions were needed before the parts came clean.  Where the oil and oxidization had turned into a thick paste, I scrubbed what I could with an old toothbrush in between repetitions in the ultrasonic cleaner.  I also cleaned all the pivot holes with wooden pegs (nothing special -- just sticks from the backyard whittled to fit the holes).

The next day, I reassembled and oiled the mechanism.  The movement portion was relatively easy to reassemble, though a few things are worthy of mention.  First, the motor needs to be installed with the TOP marked on the top.

Second, the place where there was absolutely the most thick black gunk was where I have marked with an arrow below.

This is where a circular, copper spring presses against the back of a brass wheel. The oxidation was particularly bad there, and the wheel was worn about halfway through!  I made sure to be particularly careful with the oiling of that portion...

Getting the chimes to work was surprisingly delicate.  The mechanism is visible in the picture below, which shows the front (dial side), where the control of the chiming happens.

All of the interesting stuff is along the right side.  The clock strikes every quarter hour, with a different ring for each.  The minute wheel (which is keyed to the minute hand) carries four pins that engage the mechanism below.

The horizontal lever on top is pushed to the right as the quarter hour approaches; the lever drops into a warning position as the picture shows.  It engages a small pin protruding from the back, which pulls the chiming mechanism's drive train into engagement with the motor.  Just at the quarter hour, the pin on the minute wheel slips past, and the lever pulls back (to the left), carrying the pin with it, and engaging the chiming drive train.  It also starts another wheel (bottom right) with four pins and four gaps cut in its perimeter.  This wheel times when to disengage the chimes; when this wheel rotates, the pins lift another lever (shown above right below the horizontal lever) that disengages the chimes drive train.

Long story short; the clock would start chiming but would not stop!  Upon very close inspection, I found that the pins were slightly bent, and couldn't cause the train to disengage. Straightening them fixed the problem.

I also had to align the lower right pin wheel and the chimes mechanism -- so the correct chimes rang at the right time -- fortunately there are some indexing grooves for this purpose.  But they were not obvious...

Finally, I did try to clean the chimes hammers.  Sadly, although the brass polishes nicely, the soft heads on two of the four hammers disintegrated.  Upon inspection under the microscope, they look like something fibrous that's been bound in shellac.  The most likely material is leather, though I'm not too sure.  Fortunately, a little bit of the material remains on all hammers, so I don't need to replace them quite yet.

The clock is now working quite nicely, and is on our mantle!