Subject:
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Re: Technic Pendulum Clock progress
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Newsgroups:
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lugnet.technic
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Date:
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Sun, 26 Nov 2000 04:03:52 GMT
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Viewed:
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1298 times
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John,
I have seen these two other clocks, and a few electric Lego clock
designs. I went back to these pages, and I found out that they do have
enough information to calculate efficiency. I built an approximate copy of
the Zef Damen clock's weight, and weighed it. He says he used 2 meters of
string, but the weight couldn't drop that far unless it was hung very high,
so I am guessing it used more like 4.5 feet. The clock weight in the Eric
Harshbarger clock is reported as 7 lbs, and the long-case looks like it
could probably have at least 4.5 feet for the weight to drop as well.
I think the pulley configuration I have helps my clock. It reduces the load
on the spool by a factor of 2, as you note. This helps reduce the axle
distortion and friction. The length of string that gets pulled out from the
spool is doubled, so it does not lose any efficiency. The shaft for the
pully is much shorter than the shaft for the spool, so it does not distort
as much as the spool shaft would, even though it takes the full weight. Here
is a beautiful clock that uses a pulley on the weight:
http://www.erwinsattler.de/english/gb.htm
I added more weight to the pendulum, as you suggested, and it was able to
stand a little more without stopping the clock. Now it runs with a nice
1/second cycle. I tuned it up a little, and now it is running really nicely.
While I was weighing stuff, I weighed my lead bar, and I found that it is a
1.06 lb bar. Before I had guessed that it was 5lbs, but it is really a 1lb bar.
So, I can compute efficiency for the three clocks. This is not really fair,
since my clock doesn't have hands yet, but it does show that I am on the
right track. I think my escapement design is an improvement.
Silverstein clock: 4 hrs 1.06 lbs 1.44 ft drop = 2.62 hr/ftlb
Harshbarger clock: 13 hrs 7 lbs 4.5 ft drop = 0.41 hr/ftlb
Zef clock: .5 hrs .225 lbs 4.5 ft drop = 0.49 hr/ftlb
My tinkering doesn't compare at all to these two beautifully made clocks,
but I think my escapement design is sound.
Thanks for the feedback.
In lugnet.technic, John Morgan writes:
> two things that might increase your time is a little more weight on the
> pendulum and removing the pully on the lead weight. If I recall my pulley
> physics correctly, by having that pulley there you are reducing the weight
> transmitted to your clock motor by half. Ie, the weight is distributed by the
> anchor on one side and the cable winding mech on the other.
>
> I hope this helps : )
>
> John
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Message has 1 Reply:
 | | Re: Technic Pendulum Clock progress
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| I finally got my clock to run for a solid 24 hours (plus only a few more minutes until the weights hit the floor.). It ran the whole period non-stop, and I didn't touch it until it finished its run. It was 15 minutes slow by the end of this period, (...) (23 years ago, 29-Jan-01, to lugnet.technic)
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Message is in Reply To:
| | Re: Technic Pendulum Clock progress
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| (...) I know there are some clock design pictures here in LUGNET® somewhere.you might try searching for "clock". two things that might increase your time is a little more weight on the pendulum and removing the pully on the lead weight. If I recall (...) (24 years ago, 25-Nov-00, to lugnet.technic)
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