A Mini Tower Clock

[crueby]

Continuing on with the pallet arm, I drilled the ends for the hardened pieces, and put a small flat where they will sit. The flat gives a better landing spot than the arched surface, plus the small step gives a place for them to index against so they cannot turn.

Then rough cut some pieces of hardenable tool steel, and turned a post on one end of each to fit the holes in the arm. Then laid the printed test piece on top, aligned with a piece of rod through the holes, and blued/scribed on the outlines:

The bulk of the material was milled off, leaving a little above each line:

At that point it was re-assembled, ready to take the faces down to the scribed lines. Carefully!

I took the assembly to the little belt sander, and took the faces back to the lines, with the arm on the table next to the belt. The curved impulse faces where shaped by turning the arm back and forth with the face against the belt, until I just got to the scribed line. I had the depthing tool and escape wheel with me, to test against frequently - did not want to take off too much.

Once it was clearing the wheel, and I could operate it by hand with pressure on the wheel and rocking the arm manually, it was time to take each end piece off and start polishing the faces on some super fine wet/dry paper glued to a piece of float glass.

That got things operating much more smoothly. So, the end pieces are ready to be hardened!   
One other thing done - with the depthing tool set to where the escapement operates smoothly, I marked the position of the shaft on the gear holder:

This last set of bushings will be a little different. Its common on clocks to have the bushing for the pallet be adjustable, to allow fine tuning of the action if needed at construction, and also years later to accomodate any wear. The usual way to do this is to drill the hole in the bushing slightly off center, so if the bushing is rotated it will raise or lower the shaft. A set screw with its head overlapping the rim of the bushing locks it in place.
So, next steps will be to drill the holes in the gear holders, make the bushings, and then get the bracket to hold the pendulum suspension spring made for the rear gear holder.
Also, for future reference and learning, I found a copy of that old Grazeley book on escapements from a seller online, should have it in a couple weeks. Looking forward to learning more on the topic, and finding out how many mistakes I made on this one!   

[cnr6400]

 

[mklotz]

This is fascinating stuff, Chris.  It had never occurred to me that the 'teeth' on the pallet arm would not be identical.  It greatly increases my respect for watchmakers who make tiny versions that fit in a wrist or pocket watch.

I have a vague mental image (at my age everything up there is vague) of pallet arms with precious (?) stones used as the teeth.  Was that every done or is it just the product of decaying neurons ?

Keep up the fantastic work; I check in every day.

[crueby]

This is fascinating stuff, Chris.  It had never occurred to me that the 'teeth' on the pallet arm would not be identical.  It greatly increases my respect for watchmakers who make tiny versions that fit in a wrist or pocket watch.

I have a vague mental image (at my age everything up there is vague) of pallet arms with precious (?) stones used as the teeth.  Was that every done or is it just the product of decaying neurons ?

Keep up the fantastic work; I check in every day.

The pallet arm ends bear on the same faces on the escape wheel for this kind of movement, so the faces are on opposite sides. Very clever stuff that goes WAY back in 'time'.

Yes - Ruby (no relation!    ) stones were and still are commonly used, especially in watches and chronometers. Harrison used precious stones like diamond and agate in some of his clocks, not a lot known about how he drilled the ones with holes.

Glad you are enjoying the build!      Are you going to be at Cabin Fever this year? If so looking forward to seeing you there.

[Kim]

Beautiful job on the pallet, Chris!  The removable pallet faces is very clever! 

Kim

[crueby]

Thanks Kim!  Not my idea on the removeable pallets, thats in most of the books. Works great!
This afternoon I did a test piece then hardened the pallet end blocks. Being so small, not much oil was needed to quench them. Rather than open up some motor oil and find a container, I did some checking online and verified that vegetable oils can be used as well. Better to preheat it to thin it slightly for large pieces, but for my parts room temperature worked fine. I have a bottle of peanut oil (great for making popcorn! Yummy flavor!) in the kitchen, so I just poured a bit into a cup and used that to quench in after heating the parts with the little MAPP torch. The test piece came out nice and hard, file skated off without cutting, so I did the same for the pallet ends. After rinsing them off, gave them a polish with an abrasive pad to get rid of the soot/oil residue, and installed them again, ready to get started on the bearings/etc. This kind of quenching/hardening is as close as I'll get to blademaking like on the TV show Forged In Fire!      Can hear Doug testing it and saying 'It will Tiiiick!'      For those who have not seen the show, just pretend to smile and move on...

[wagnmkr]

Thanks ... I have that voice in my head now!!!

 

Tom

[Charles Lamont]

I have watched about two minutes of Forged in Fire. I could not stand the falsely overexcited, hyperactive style of the presentation. Come to think of it, 'overwrought' might be a more apt adjective.

[crueby]

Got the bearings for the escape pallet made. Turned the OD with the stock centered, and drilled the hole with it offset in the 4 jaw. Pic is a bit blurry but you can see the setup

Here they are installed in the gear holders, along with the pendulum hanger block. The bearings will be held in place with the small screws on the rims. They will allow small adjustments to the mesh of the pallets. This, again, is standard practice on a lot of clocks.

Next will be to give these two gear holders a good sanding and then a coat of the clear spray before assembly. I can get a start on the pendulum crutch and the hanger spring in the meantime.

[cnr6400]

  I didn't know this clock was going to have Stephenson valvegear...

Just kidding, those eccentric adjuster bushes might come in real handy at some point. 

[crueby]

I didn't know this clock was going to have Stephenson valvegear...

Just kidding, those eccentric adjuster bushes might come in real handy at some point. 

Hmmm, it would make it more fun to set the clocks back an hour for daylight savings changes...   

[crueby]

The gear holders for the left set have been sanded and sprayed with the clear, that is drying. While waiting for that, I started in on the pendulum hanger pieces. I had a piece of suspension spring (wide flat spring stock) from a previous clock project just long enough, so I made up some flat stock pieces for the ends and got them all drilled through for the suspension pins. Also slotted the end of a length of round bar for the pendulum rod, for now left a bit long. I'll trim it and put a threaded section on the end after some experiments with the pendulum bob (yet to be made) to get the length closer to correct.

Without Bob hanging off the bottom end, the period on the pendulum is pretty short, putting a clamp on the lower end to lower the center of gravity on the assembly gets it out to about the proper period, so I know my calculations were good.

[cnr6400]

 

[crueby]

Okay, the gear holders were clear coated yesterday and are set up, so everything was reassembled on the frame. Also made the pendulum crutch, which connects the escape pallet shaft to the pendulum with a long forked piece that captures the pendulum shaft. I made a small pendulum bob to test with, I need to look things up to see what wieght it ought to be - I just grabbed a scrap piece to use to get things running.



And here is a video of it ticking over for the first time!  It still needs a lot of tuning, it runs for minutes at a time then stops. Currently there is no oil on the shaft pivots, and the mesh on the gears was just quickly set. I need to go back and check alignment of the gear holders with a square to ensure they are all vertical and in line front to back. But, this is a great step!
<a href="https://www.youtube.com/watch?v=-Hj2E3H85e0" target="_blank">http://www.youtube.com/watch?v=-Hj2E3H85e0</a>

[Kim]

That is just beautiful!  Very exciting, Chris!   

Kim