CNC and clock building

[cjablonski]

Definitely not interrupting! That's what the forum is all about, different views, different approaches to problems ect. Which law design did you choose?

[BillK]

I went with the Clock 1, not so much that it is the first one I saw, but because I liked the design, even though I want to alter some things.

[cjablonski]

I personally have liked Brian Laws escapements, but I myself aren't particularly enamored with the esthetics of his overall designs, so I completely understand your wish to alter the look. Keep us posted!

[bill z]

BillK,

Please allow me to make a suggestion since this will be your first clock. Just do Law's Clock 1 as described by him and get it working. Then start adding your modifications. I went into making these clocks with some assumptions that proved to be in error. If it wasn't for encouragers like cjablonski, I may have dropped it as a lost cause. Just do the Clock 1 as is first.

When I first started, I started building Brian Law's Clock 1 from a PDF where I cut and pasted it to the plywood and started cutting using my jig saw. WOW! As I was cutting, I couldn't help but think that has to be a better way to do this. That is what started me dreaming of a CNC. OK, I am about the finished product and not the making. There I said it. One miss step with my saw and devastation.

Being new to the CNC, I went with a Simplicity DXF because I thought it would be easier. At the time I didn't know how to bring a PDF into Aspire. I did learn a bunch about Aspire and the Shark with this clock project. I think I can now take a PDF image and create a TAP file for a decent Clock 1.

I will be interested in watching your progress and the finished clock(s).

[cjablonski]

As always bill, thanks for the kind words

[BillK]

Hi guys,

Well I got started. First thing though, I spent $20 for the DXF file and downloaded it with all the PDF files. To let you know, I am a Mechanical Engineer for over 36 years now, so I spent some time reviewing the design and checking how the components interact, as well as analyzing the gear train. I found some errors on the assembly PDF and one error on a gear bore in the DXF file so far. As a pretty experienced person with my shark and with Aspire, the changes I made to the first gear I cut were for aesthetics and for ease of cutting. I have many bits of 1/16 diameter as well as smaller and larger sizes, but I thought it would be best to cut this using a 1/8" end mill. Checking one of the gears it might have left the root with too large a radius so the alteration I did there was to change from a flat bottom to a radiused one, only increasing the depth by 1/16". This is the first gear off the machine tonight and it cut very smoothly. Many more parts to go, and I will be altering in this manner where I see the need. I will also try to keep a running list of any errors I find and email them to Brian Law at the end.

[BobA]

Nice job

[cjablonski]

Really well done!

[bill z]

Scripting on the spokes!! Very nice in deed!!

BillK, with you being an engineer and I'm not, I would like to discuss with you (where I'll be learning) about the pendulum weight to the main weight.

Because the clock has to nudge the pendulum each swing, where are the limits, if any?

[BillK]

Hi Bill,

Well, I did a few calculations to help answer your questions based on the Law clock 1 design that I am working on. I'm going to guess and say that these calculations are probably good for a lot of clocks like this, or will be very close. Why re-invent the wheel or the gear train if it works? Lol.

Anyway, the pendulum is a theoretical perfect machine that runs on an initial force and then is powered by gravity. Pivoting on a small point makes the friction very low, and the only other thing that can subtract from its efficiency is air resistance. So just like pushing a child on a swing, once they get to the height they want, very little effort is required to maintain it.

And very little force is what you get from a clock gear train like this. Take a look at this chart:

These calculations are theoretical and don't consider friction which can be considerable.

Law says to start with a 6 pound weight and adjust from there. Some people claim to have used as little as 3 pounds which would cut these calculations in half. At any rate, 0.024 pound is only slightly more than 1/3 of an ounce of force on the escapement from the timing wheel. The timing mechanism of the pendulum is more dependent on the length of the pendulum, rather than the weight at the end. The nudge from the timing wheel is probably just enough to make up for the lost friction and keep it swinging.

In other news, I guess I'm making this clock project into a slightly hybrid version. I decided to model the rachet-spool-winding gear as a one piece assembly and with the pawl, 3D print them out of ABS plastic. Here the 3D model the parts are printing now.

And a new model for my next wooden gear.