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Alternative Clock-Mechanical Answered

I need to build a device for a competition that can measure time acurate to the tenth of a second, but from its starting position it must be no more than 30cm in dimension, but can exceed that once it begins.  Even if you know of something that can do seconds that would be fantastic.  If you have any ideas or places to find plans please do tell.  IT CANNOT USE ELECTRICITY



9 years ago

There is some good information on the specifics of clocks on wikipedia.  

A good choice for an accurate pendulum clock is a grasshopper escapement and gridiron pendulum.  This is the cheapest method for building an accurate clock.

As for a tenth of a second, it is possible but will probably be a little costly as you might have to use invar.  Try it with a gridiron layout to reduce the length change even more.  The same wiki article above says that a quality home clock loses 10 seconds per month.  That is 1/3 sec per day.  Not quite 1/10th of a second so you will likely be unable to use bought parts.  Also, if you dimple the pendulum this will reduce wind resistance(not sure if it would be enough to make a difference)

Keep in mind, the most important parts of an accurate clock are the occilator and escapement so start there.  You need to prevent the occilator from expanding due to temperature as this effects its period(gridiron does a good job and there is also a method for wheels).  Also, interference from the escapement will greatly effect the period of the occilator. 

This article is a good start when it comes time to choose an escapement.

Be sure to post an 'able if this gets built.  Would love to see the final design.  Hopefully I will be able to post my own 'able soon so I won't feel like such a hypocrite everytime I say that.  lol.

A little history:
Most of the best parts were invented by one John Harrison, a carpenter back in the 18th century.  He literal dedicated his entire life to perfecting the mechanical clock.  All the best parts were invented by him and very little has been done to impove on this technology except for materials.  They are harder to make though so they are not easy to find.  His H4 is essencially the design that meets you competition requirements.

As for a place to buy parts:
Clockworks has parts to buy but not sure about quality.  For accuracy contests you can only rely on custom orders from machinists or DIY ; )
Fry Steel Co., in Santa Fe Springs, CA (310) 802-2721.
Invar FM. Round stock. For 1/2 inch diameter, a 12-foot stick weighs 8 pounds, and it costs $12 per pound. If you want less, it is $12.95 per pound, plus an $8 cutting charge; also $25 packaging charge, plus shipping.
Note UPS won't take a 12-foot package, so you *must* pay the cutting charge unless you live nearby.

I am probably too late for you to meet the deadline of your competition but thought this was good information.

PS: Sorry if this is wordy but there is a lot of information to convey and I wanted to be complete and clear.


9 years ago

I've seen this homework question before (but I can't find it right now)


Doctor What

9 years ago

 Howabout a very small wind up clock?

Rock SoldierDoctor What

Reply 9 years ago

(I'm not good with conversions...)
But still, a foot still isn't that large. Larger then an inch, but still not that large.