How To Make A Clock In The Home Machine Shop - Part 18 - Making The Pendulum

Making The Pendulum, by Clickspring.

In this video I complete the pendulum assembly, and then have a quick look its behaviour with the help of a Microset timing machine.

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A very special thank you to Patrons Dan Keen, and Samuel Irons.
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Cameras used in this video:
Panasonic GH5 - https://amzn.to/2rEzhh2
Panasonic X920 - https://amzn.to/2wzxxdT

Tools & Shop Products:
"Solidworks 2013 Bible": http://amzn.to/2FObS1D
Dykem 80300 Steel Blue Layout Fluid, Brush-in-Cap (4oz): http://amzn.to/2HGPaJJ
Interapid Dial Test Indicator: http://amzn.to/2FPInwH
Loctite 231097 603 Retaining Compound, 10 mL: http://amzn.to/2pid6vR
Digital Calipers: https://amzn.to/2IkFh4O
Sherline Lathe: http://amzn.to/2pnXM19

More pendulum Information:

Galileo discovers the interesting properties of the pendulum: https://www.youtube.com/watch?v=MpzaCCbX-z4

Huygens uses a pendulum to revolutionise clock construction: http://www.historyofinformation.com/expanded.php?id=3506

Pendulums are not quite Isochronous - Circular error: https://en.wikipedia.org/wiki/Pendulum#Period_of_oscillation
http://www.rmg.co.uk/discover/behind-the-scenes/blog/second-one-hundred-days-results

Gravity is not a constant: https://en.wikipedia.org/wiki/Kater%27s_pendulum

Pendulum length is not constant either - Temperature Compensation: https://en.wikipedia.org/wiki/Pendulum#Temperature_compensation

Pendulums are bouyant and experience drag - Baromatric compensation: https://en.wikipedia.org/wiki/Pendulum#Atmospheric_pressure

Pendulum stability and Q (not the guy from Star Trek Next Gen): https://en.wikipedia.org/wiki/Pendulum#Q_factor
http://www.meccanotec.com/pendulum.htm

Harrison was correct - Larger amplitude, High Q, reduced circular error = astounding results. The Burgess Clock B trials - https://www.youtube.com/watch?v=sQAY-zFkVyQ

Abbreviated Transcript:

0:00:11 If there's one common attribute across all mechanical timepieces, its that each must have a component that provides a fixed and consistent interval of time.
0:00:45 The plans call for a simple brass disc for the bob, but I think it'll be a bit more interesting with a contoured profile like this.
0:01:15 Now although the profile of the bob is quite simple, its shape makes it quite a challenging part to hold on to, while making the required cuts.
0:03:37 The taper cut removes the bulk of the material, and so reduces the workload for the form tool that follows. Now that surface finish needs to be improved, so I wrapped abrasive paper around this file to maintain the contour, while I sanded and then polished the surface.
0:06:41 The tool is gently brought into contact with the work, until the bearing starts to continuously rotate. At this point the lathe is stopped, and the jaws further tightened. Visually I can see that the part is running quite true, but an indicator shows just how effective this simple tool can be.
0:09:44 A light sand and polish brings up the surface finish, and its ready to have the features for the hook formed. First up I'm drilling a cross hole to define the top of the hook slot. The cross hole diameter is 1mm, and I've used the drill bit to help me align the workpiece in the vise.
0:11:52 A few drops of loctite bond these last two parts in place, and I'm taking care to align the hook and block perpendicular to the face of the pendulum bob. And thats the pendulum assembly complete, so lets have a look at it in action.
0:12:48 And secondly that time interval is approximately proportional to the square root of the pendulum length divided by gravity. This gives us two things. We can tolerate some small variations in how wide our pendulum swings, and still have an accurate clock.
0:13:42 I've set up a timing machine to measure the time interval of a complete swing, and at the moment it's a little less than 1 a second. But as I lengthen the pendulum suspension thread, I increase the effective length of the pendulum, and so that time interval also increases, this case, to just over 1 second per swing.
0:13:59 The pendulum needs to receive a regular push to replace the small amount of energy that it loses to friction, and it receives that push from another crucial part of the clock mechanism that I'll complete in a future video. The escapement.

References:

John Wilding "Large Wheel Skeleton Clock" construction book can be purchased online from Ian T Cobb:
http://www.clockmaking-brass.co.uk/clock_construction_books.html

Making The Pendulum, by Clickspring.

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