Author Topic: No escapement?  (Read 12295 times)

Gryphon

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No escapement?
« on: January 19, 2009, 01:52:27 PM »
One of my kids' toys sparked my imagination.  Would it be possible to build a clock that used multiple pendulums and a crankshaft to generate constant rotation?  They would have a pivot above the crankshaft and slots in the arms to generate the motion.  I was thinking 4 pendulums and the pins on the crankshaft rotated 90 deg from the next one. 

Gryphon

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Re: No escapement?
« Reply #1 on: January 24, 2009, 07:03:51 AM »
Finished my first cardboard prototype.  It failed.  The crankshaft wouldn't stay straight.  I'll have to think of a new way to do that for this prototype.  I think wood would be strong enough to hold together, but bolts and cardboard don't. 

Also, design thoughts:

1 - The circumference of your offset pin's path and the arc of the pendulum determine how far above your crankshaft the pivot should be.
2 - It would seem that any number of pendulums greater than 2 would work well.  Odd numbers may even work better as there would be one at a dead spot(vertical motion, where that pendulum can't affect the motion) at any given time.
3 - A tock could be added by a small ball on the end of a spring attached to the top of the pendulums.  A hollow wooden block placed at the top would tock as each pendulum reached the farthest point in it's swing in one direction.  Would likely tock a lot faster than most clocks.

Just some thoughts.
Gryphon

Offline chuckknight

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Re: No escapement?
« Reply #2 on: January 25, 2009, 09:58:26 PM »
I think prime numbers of pendulums would work best...1, 2, 3, 5, 7, 11, 13, 17, etc.

Another way to do this would be to use paramagnetism...an aluminum disc rotating through a magnetic field (permanent horseshoe magnet) will generate eddy currents, resulting in a braking effect.  It might have to be a *very* strong magnet...but it should be workable.

Chuck
« Last Edit: January 25, 2009, 10:12:31 PM by chuckknight »

Gryphon

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Re: No escapement?
« Reply #3 on: January 26, 2009, 06:21:01 AM »
Primes would probably work very well, except for 1.  It will stall at the ends of the arc as the pin on the crank would have to move vertically to continue the circle.  That was my origional thought and I caught the stall.  My solution was to use multiple pendulums.

Can you explain more about the paramagnetism?  I can't find a very good explaination of it online.

Gryphon

Offline chuckknight

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Re: No escapement?
« Reply #4 on: January 26, 2009, 07:36:59 AM »
http://www.youtube.com/watch?v=WHCwgc_xs3s

This is a decent explanation (and demonstration) of Lenz's Law, which basically says that certain paramagnetic substances like aluminum and copper, will resist a magnetic force.  There was a GREAT demonstration, years ago, on Mr. Wizard...but I can't find it on YouTube.

Here's a demonstration with a simple aluminum heat sink

http://www.youtube.com/watch?v=90fWGMidy9Q&NR=1

Same thing works with a conductive disk in a magnetic field...think horseshoe magnet.

Chuck

Gryphon

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Re: No escapement?
« Reply #5 on: January 26, 2009, 11:52:16 AM »
Ok, I understand the concept now.  I'm still not sure of the application in a clock.  How would you use that to create motion?

Gryphon

Offline chuckknight

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Re: No escapement?
« Reply #6 on: January 26, 2009, 04:15:13 PM »
You wouldn't use it to create motion.  You would use it, like an escapement, to retard motion.

The fundamental purpose of an escapement is to keep the weight from falling down...to release the power, instead, in measured increments.  By doing so, and tying a gear train to it, we get a clock that ticks in discrete units, usually seconds.

Your question was how to create a "no escapement" clockwork that unwinds continuously, generating constant (but controlled) rotation.  I would approach the problem using this principle.  It's basically nothing more than an electromagnetic brake, and should generate a constant resistive force.  Since acceleration due to gravity is also a constant, the resulting motion should be a completely smooth, but very slow descent of the weight.

Possible problems would include variations in timekeeping, due to other factors...sticky lubricants, for example.  And, loss of magnetism in the permanent magnets...but that shouldn't have a significant effect for hundreds of years.

Your goal, as I understood it, was to have a gear train that measures out time...doing so without "ticking," but instead by rotating at a constant speed.  By restricting the speed with which it can unwind (Lenz's Law...eddy currents) you should be able to accomplish this, with a very simple mechanism.

I may have to build one, just to prove the concept...it *should* work.  The rate could probably be controlled by adjusting the mass of the weight.

Chuck

Gryphon

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Re: No escapement?
« Reply #7 on: January 26, 2009, 07:36:19 PM »
Ok.  I understand where you are coming from now.  I like that idea as well.  Would definately be able to make a clock that could go a long time between windings.  Especially if you had a really long drum with lots of windings.  Could you use a series of pulleys(block and tackle) to keep the distance of the fall shorter and still have a long length of cord?

My idea didn't use a weight at all.  The driving force on the crank was provided entirely by the motion of the pendulums.  I imagine friction would play a part after a while, but the pendulums should give a slight push to others in different stages of swing by continuing the rotation of the crankshaft.  It would probably take much more mass on the pendulums to give them the required inertia as well.

I think it's interesting how a misunderstanding can spawn an entirely different idea that could be just as viable.  Any other thoughts are welcome as well.

Gryphon

Offline chuckknight

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Re: No escapement?
« Reply #8 on: January 26, 2009, 09:35:22 PM »
Wouldn't that, by definition, be a perpetual motion machine?  I have a whole book on them...fun reading.

Chuck

Gryphon

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Re: No escapement?
« Reply #9 on: January 27, 2009, 06:31:43 AM »
Yes, I guess it would make it a perpetual motion machine.  Hmmm.  I'll have to think on that some more to see if I can come up with a solution.

Gryphon