Clockathon #2 Test Jig Video

[Christopher Boynton]

Here's a video of it ticking with an escapement rotation period of 29.8 sec. on $2 worth of pennies (about 500g).

http://www.youtube.com/watch?v=XPbUiVH44mA&feature=youtu.be

[ruste...@prototribe.net]

Very cool, in Technicolor!

> <http://www.youtube.com/watch?v=XPbUiVH44mA&feature=youtu.be>
>
>

[Alexander Schwartzberg]

This is really, really beautiful.

[Mathieu Glachant]

That warms the clockles of my heart! Beautiful work on the hands and on the pendulum. :-)

I think the gears may be in the wrong order, since the drum is supposed to be between the hour and minute gear, but if the clock runs, those two gears may be interchangeable? Need to check the gearing to make sure... And need to label the gears using some text script or other!

On Sunday, February 19, 2012, Alexander Schwartzberg wrote:

This is really, really beautiful.

[Christopher Boynton]

Hi, 

The minute hand does about a quarter turn in 15 min so it's running okay.  The ratchet & drum wont actually fit between minute and hour gears due to the minute gear's concentric shaft.  I think this is the correct configuration but let me know if you find otherwise.

--
-Christopher

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[Mathieu Glachant]

Hum... I'm relatively sure the drum was supposed to drop in between
the hour and minute gear, but it may be that it has the same gearing
as the one it got switched with, which would mean the clock keeps the
same time.

Just because we may have changed the gear between hour and minutes
gears, however, it might be a good idea to check that when the minute
gear does one revolution, that the hour hand advances by one twelfth
of a revolution. Just to be sure... :-)

This is what it was doing on this video at the end of Clockathon #2:

http://www.youtube.com/watch?v=AH4Tg2tIgfg

Moving the drum back towards the escapement just means it won't run as
long for a given length of weight drop. Not a huge issue for demos,
but not practical for a clock set to run for at least a day. It also
means that the weight must be heavier, and since it is also further
forward, it may be necessary to add a front case for support, again,
perhaps not the best for demos.

[Christopher Boynton]

For the drum/ratchet assembly to fit on the same axle between the minute and hour hand the minute hand shaft, upon which the hour gear rides, would have to pass through the drum/ratchet, which it is too wide to do, and be much longer to still have enough shaft for the hour gear to ride on, since it is now accommodating the ratchet wheel and drum.  This would also mean eliminating the bearings on the entire drum/ratchet which would probably be a bad idea.  To move the drum/ratchet to the lower axle, between the hour and minute hand would, again, require a much longer minute gear shaft.

In the video you referenced there doesn't appear to be a drum/ratchet assembly.  Just the original #2 intermediate gear with its built in narrow "drum".  Also, the front most gear on the top axle appears to be the ratchet wheel without its ratchet arms/drum. 

Since the current configuration does a 30 sec escapement rotation, a quarter turn of the minute hand in 15 min, and (I'll reconfirm this afternoon) the hour hand a 1/12 turn I'd say everything is in its right place.

[Mathieu Glachant]

Sorry, I wasn't clear. By between the hour gear and the minute gear, I
meant the gear, on the other shaft, that meshes with both the minute
gear and the hour gear. The intent was to replace the built-in,
non-ratcheting drum of gear #2 (counting the hour gear as #1 and the
minute gear as #3) from clockathon #2 with a ratcheting version.

I checked the gear ratios for the clock you printed out:

ratio1= -3; // 3
ratio2= -4; // 12
ratio3= -2.5; // 30 or 12x2.5
ratio4= -3; // 90 or 12x7.5
ratio5= -4; // 360 or 12x30
ratio6= -4; // 1440 or 12x120

Looks like gear #2 (which has a gear ratio of 3 ahead of it and 4
behind it) is completely interchangeable with gear #5 (which also has
3 ahead and 4 behind. So in this clock, the drum can go in either
place and the clock will work just fine.

I totally agree with you that if the clock is keeping time correctly
(it seems to up to the minute hand based on your earlier testing) than
there is no reason to mess with it. The only difference would be how
much weight is needed to drive the clock, and how long it will run
before the weight hits the floor, both by a factor of thirty.

Let me say again how much I love that video and thanks for putting one
together! :-)

On Mon, Feb 20, 2012 at 11:03 AM, Christopher Boynton

[Christopher Boynton]

Yep.  I just stared at it for a long time and came to the conclusion that I totally misunderstood.  In the video, it's running on less than 2lbs but I think it only goes for 30-40 minutes before the weight bottoms out.  I'll try it in the correct configuration this afternoon and report back.

[Mathieu Glachant]

Yeah, we're going to need work on documentation and parts labeling to
make a kit out of this. It's really not intuitive which gear is which!

30-40 minutes sounds about right, actually. I think the drum has a
circumference around 25cm, so for a one meter drop, you'd get four
revolutions. On the second gear, that would 4/3 revolutions of the
hour gear, or 16 hours or so. Gear #5 runs 30 times faster, so 32
minutes runtime.

Lastly, Gear #2 and Gear #5 are on different shafts, which means that
they don't rotate in the same direction. So the ratchets won't work as
originally designed with the drum in position #5, and would have to be
printed mirrored. Which, if I remember correctly, is something you had
to do!

Lovely when it all comes together.