Sunday, November 29, 2015

Handle for a plane

Here's a short lathe project...  My dad likes restoring old woodworking tools.  Here's a plane that's missing a front handle.

Here's a handle I turned from a piece of oak.

which has a bored recess on the back to fit the socket on the plane:

Here is the handle installed!

Timer is finished!

I made a number of finishing touches to the gravity escapement timer.  It now runs reliably!
First, I turned a thicker barrel on the lathe

Using a square file, I cut a keyway to engage with the metal teeth on the existing barrel.

Here's the finished barrel, ready for installation...

...and here it is installed.

Many of the wheels weren't running smoothly.  To find where to file, I used a pencil to mark the pinion teeth...

... which transfered to the driving wheel.  This could be filed down as needed.

Quite accidentally, I made the pinion teeth an integer multiple of their driving wheel teeth.  This made debugging easier!  Because I found certain pairs of teeth consistently binding.  I marked them like so

which allowed me to track down the problems! 
 I made a 4 oz pendulum bob from two halves that friction fit to the pendulum. 

The excess screws are for weight!

It's worth noting setting that a gravity escapement in beat is quite a bit more delicate than I expected.  Here's a picture of the timer in action...

And a link to a video!

Friday, November 27, 2015

Timer improvements

Current specs:
  1. Pendulum bob is around 2 oz
  2. The barrel should be 1/2"-3/4" diameter and about 1" long
  3. The hand should be about 2.5" long
Working off the timer improvements list...
  1. I replaced the pendulum hanger with plastic.  Much more rigid, and keeps the pendulum where it should be.
  2. The gravity arm hangers were remade.

They're two-part pins that press together.  This took a bit of doing since I misjudged just about every diameter and had to remake them...  But in the end, they seem to be an improvement.

Saturday, November 21, 2015

Balance staff (preliminary)

I have several broken watches in which the problem appears to be (at least) that one of the balance staff pivots is broken. I'd like to build my experience to the point where I can fix this problem, which involves making a new balance staff. Fortunately, I have a balance wheel with this issue that doesn't go with any watch that I have. So, I attempted the repair on this part first, knowing that failure wouldn't be much of an issue.

I started with a 1/4" steel rod, which I turned to fit the 3/16" collet I have for my lathe. Unfortunately, my lathe seems to take 4C collets, which aren't very common. The smallest collet I have is 3/16", so that's what I have to use.
After two tries, I was able to turn a passable start at a balance staff. That is, the balance wheel fit the rivet nicely, and the pivot came out intact.

The picture above shows the view of the new (left) and original (right) parts. I wasn't careful with the lengths, and I haven't yet cut the second pivot. At this point, I needed to reverse and regrip the staff in the lathe. If I had a suitable small collet, this would be easy. But I don't, and therefore needed to hack something.

I came up with the idea of gripping a pin vise (which happened to have a handle 3/16" in diameter) in the collet, and the part in the jaws of the pin vice. The vice seems to run true, but it took a bit of doing to keep the end of the vice straight. In the end, there was a bit of runout, which I'm not pleased about.

Again through the microscope, the new part is on the bottom.

Staking the balance wheel.

Post staking... It's securely attached!

Roller table reattached. This is a taper fit; I probably made it too loose, and was able to push it on by hand (in the staking tool).

Finally, a picture of the finished assembly, to show size.

In the end, it went together pretty well. The major remaining issue is how to regrip the part in the lathe without runout. Of course, there is the possibility of running between centers, but I don't have centers made, so this would involve obtaining such as setup...

Sunday, November 1, 2015

Reaming a piston cylinder

In order to have a perfectly fitting piston and cylinder pair, it's necessary to have an accurately drilled cylinder.  When I tried drilling before, I was unable to get the accuracy needed for smooth motion.  The inside of the cylinder changed diameter and had internal ridges that the piston would get caught on.

The usual solution to the problem is to drill an undersized hole (bearing in mind that a typical drill bit will drill slightly larger than its stated size) and then ream it to the correct size.  This requires a reamer, which can be made as needed.  This is the first such reamer I made -- loosely inspired by this page -- it's passable, but not perfect.

To start, I turned the reamer body from a 1/4" steel rod to precisely the size I wanted to have the cylinder bore.  In this case, I turned it to a diameter of 0.19" -- just 2.5 thousandths larger than 3/16". 

One roughly turned, I polished it with several grades of carbide sandpaper, finishing with 1200 grit and parted it off.

Then, I ground about half of the diameter away on the griding wheel and beveled the leading edge. 

This came out much more messy than I intended, but after cleaning up on an oilstone, the edge was sharp.  I heat treated the reamer tip and left it dead hard. I never got the rest of the reamer hot enough to harden it.

Here's the cylinder after drilling with an 11/64" bit.

Here is the reamer in action, cutting about 1/16" at a time before needing the chips (rather a fine powder) to be cleared.

After reaming, I turned a piston to fit. 

I cleaned both the piston and cylinder in isopropyl alcohol to remove chips.  The piston slides smoothly and is a quite close fit. 

A little clock oil improves the action, and you can feel a small amount of compression as the piston moves in.  If the piston is pushed in quickly and then withdrawn, the end of the piston is slightly warm.  Not hot enough to be used as a fire piston (it should be longer, so more compression occurs), but still enough to indicate that the fit is close.

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!

Sunday, September 20, 2015

Two weekends of clock construction

I made considerable progress on my timer over the past two weekends.  I started with a pile of parts (after sanding)...
... and ended up with a nearly complete, partially functional timepiece!
Here is how it happened...

Since the design phase, I had left the spacing between the two plates as a yet-to-be determined variable.  The key distance was the winding barrel, which had to rotate freely around the main wheel's arbor and engage with the ratchet and click assembly.  I wasn't quite sure how much room I'd need, so I built the winding barrel first.

The winding barrel is hollow, and has two transverse pins to anchor the winding ribbon.  First, I turned the outside of the winding barrel from 1/4" brass rod.  Notice the thicker end (left) to receive the ratchet wheel.
I filed flats on the narrower portions...
And drilled holes to receive the pins in the flats.
I turned the pins from 1/8" brass rod, tapered to fit into the holes.
I pressed the pins into place with the vice.
This wasn't secure enough to keep the pins in place while center drilling, so I also soldered them.
I center drilled the assembled winding barrel in the lathe.  
After it was drilled, it was fit friction-tight into the ratchet wheel.

Now that I knew the length of the winding barrel, I could estimate the distance between plates.  Here are the two standoffs that hold the plates in place.
I also fabricated four pivots and two hollow bushings for the three arbors.
Here are the main wheel pivots drilled and fit into the frame.
Once that was all in place, I turned the main wheel arbor so that the winding barrel fit around it.  I turned this out of a single piece of 1/4" brass rod, which took a while.
Then, I pressed the assembly together -- the winding barrel is permanently captive on the arbor.
With the main wheel assembled, I could align the main wheel pivot and bushing by aligning the two plates.  This ensured that the arbor was installed perpendicular to the plates; if I had assembled the plates first, there was the risk that the pivot and bushing centers might be slightly out of alignment.
Next, I started to assemble the winding mechanism.  Here is the click in place; I used a short nail with a broad head to attach the click so that it can move freely.
For the spring, I used the drive spring from a broken toy car.  (There are lots of toy cars around my house since Theodore loves cars!  Whenever a car gets destroyed, I scavenge for useful parts, springs in particular.)  The spring was easy to cut with diagonal cutters, and easy to bend to shape with tweezers.
Here is the spring installed with two small finishing nails.  I put the nails in first...
... and then trimmed off their points flush with the back of the wheel.
In order to drill the other wheels, I realized that I was struggling to get perpendicular holes since I don't have a drill press.  So, I made a clamp assembly for my lathe's flat faceplate.   I started with a sheet of steel and drilled four mounting holes.  I think that the steel was probably hardened, and I was unable to anneal it with my small propane torch.  Anyway, I broke two drill bits.  One was a carbide-tipped bit for drilling glass, which cracked -- thankfully after finishing the holes!
Then, came the job of cutting the clamps out.  Again, much tool stress later (wore out the teeth on my hacksaw and two jeweler's saw blades), I had my clamps.  I filed them neatly, so they wouldn't mark anything.
Here they are, holding the second wheel securely in place.  I also made use of a wobble stick to get the center just right.
And with that, turned a simple arbor and fitted the wheel and pinion into the frame.
Now, on to the escape wheel.  Again, it was important to get the size of the escape wheel before making its arbor.  The escape wheel consists of two three-toothed wheels, held part by three brass pins.  Here are the pins, turned from 1/8" brass rod.
The pins are pressed into holes on each of the wheels, forming the escape wheel.
Now, with the escape wheel sized, I was able to figure the length of the arbor.  I learned my lesson with the main wheel: turning down a 1/4" brass rod to 1/8" over nearly its entire length so that you have a hub takes long time.  To economize on time a bit, I turned the arbor from 1/8" rod brass, and made a separate hub from 1/4" brass rod.
These two items were soldered together, thereby avoiding waste of time and materials.
The escape pinion was pressed on, using my now-standard technique of pressing on the lathe.
As usually happens to me, the depthing for this wheel wasn't perfect.  So I opened up the bushing and pivot holes a bit and shimmed them to fit.
Here, the escapement wheel is pressed into place on its arbor.  This means that the escape wheel and its pinion are permanently attached to the outer plate.
Trial assembly; most everything seems to fit.  The wheels turn (mostly) smoothly, with the escape pinion occasionally binding.  That'll be a problem for later, but it will need to be managed...  Anyhow, this was the end of the first weekend, probably about 10 hours in total.

The second weekend started with making lots of pins...  There are (top to bottom) 2x locking pins, 2x pendulum crutch pins, 2x gravity arm pivots, and a pendulum support.
Here are the locking and crutch pins installed on the gravity arms.
Here are the gravity arm pivots.  It turned out that I had made these too short, so I put washers in as a stop-gap measure.  Will need to fix later.
The pendulum support rod was set up in the style of what's shown in Gary Mahoney's clock:

I slit my pendulum support rod with a jeweler's saw, filed two flats, and then drilled to receive a screw.
This allows the pendulum to be attached with a flexible hinge of some sort.  For the moment, I'm using paper.  Maybe I'll use a flat spring.
The whole mechanism is assembled and mounted!
It runs, somewhat intermittently, with 4lb 4oz of weight!  It is noisy!

The key issues seem to be that
  1. The escape pinion binds occasionally, stopping the clock
  2. The escape wheel occasionally skips, in which it slips past its locking pin rather than being captured.  This is kind of catastrophic since the pendulum receives an out-of-phase impulse; sometimes it can recover, sometimes it can't.  I think the cause is the gravity arms slipping along their pivots.
Remaining tasks:
  1. Cap off the ends of the gravity arm pivots.  The arms tend to slip around and off the pivots
  2. Fix the gravity arm pivots by either remaking them (preferable) or making custom washers so that they keep the gravity arms the correct distance away from the outer plate.
  3. Fix the depthing of the escape pinion
  4. Fabricate a pendulum bob.  The current bob is attached with a rubber band
  5. Replace the pendulum pivot with something a bit stiffer than paper -- the pendulum wobbles axially too much.
  6. Fashion a drive weight and winding pull
  7. Fashion a hand for the main wheel arbor
  8. Further debugging until it runs reliably