Author Topic: New Clock  (Read 14402 times)

Offline jrbeall

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New Clock
« on: January 14, 2006, 02:25:33 PM »
Have decided to start 2006 with a new clock design and have made some progress already.  Always looking for womething different, I have come up with a design which has the pendulum on top. (don't ask) Not a compound pendulum but regular looking job, held upright by magnets.  Experiments suggest that it can be made to beat about any interval by adjusting the weight and the magnet spacing.  It looks pretty different but thats my schtick.

Have cut the plates and the pinions and tomorrow I will do the wheels.  I may power it with bows eventually but that will mean adding a rememtoire so I think initially I will run it with a constant torque spring motor.  These little motors are great and inexpensive and very easy to use in a clock.  I never hear of anyone doing it though.  

The upper part of the train uses wheels and pinions that are .05 English module.  Pitch circle is .55 inch for a 10 tooth pinion.  These are pretty small and I can only use a 3/16 hole.  I expect this is about as small as is practical for wood.  They are about 1/4 thick and 5 plys of my shop made plywood.  I am using an 80 tooth .065M great wheel.  It is great having a CNC mill and being able to cut any size wheel and pinion I like with nothing more than a 1/16 end mill.

I will try to get up some pictures of this insanity  soon.

Offline rabbit

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your latest clock
« Reply #1 on: January 15, 2006, 09:11:40 PM »
JR, that sounds so cool. I just love the unusual!
Your post prompts me to ramble; forgive me...
I'm so jealous of the CNC machining! But for the "tool-impaired" like me there is hope: I built a clock recently where I wanted the train to be as small as possible. I used 0.050" pitch for most of the gears and 1/32" pitch for some. The great wheel is only 4" in diameter and the 8-tooth pinion in the dial train is 1/4" pitch diameter! All of the gears less than about 1" in diameter had to be made by hand (literally) because they were too small to be cut safely with the scrollsaw. Little tiny gears CAN be done with just a coping saw, a file, and sandpaper.
I also built a clock once upon a time powered by a "Negator" (constant torque) spring. The problem was that even with the largest spring I could find, the design run-time was only 18 hours. It works great, but you have to wind it twice a day.
And, speaking of spring-powered clocks, the remontoire is good - it's really fun; I built one. It's a great design challenge, and a total trip to watch it run. But have you considered a gravity escape? I've built a bunch of spring-powered clocks, but the only successful ones were the remontoire, the gravity, and (if you want to call it "successful") my Congreve.
And, still speaking of "powered", how about posting some kind of design info on your bow power? These clocks are simply beautiful, and I'm really intrigued by the bow power. Like I said, I love the unusual, and it's the "machinery" that I really love!
- rabbit

Offline jrbeall

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New Clock
« Reply #2 on: January 16, 2006, 04:53:40 AM »
Rabbit,
You are way ahead of me in the miniature department.  I can't imagine cutting those gears by hand.  I don't know if you ever sell any of your clocks but if you did, just one good sale would buy you a small CNC mill.  With that you could do all your plates, pinions and wheels in one day.

I have been thinking about a gravity escapement and I have done a couple of experimental balance wheel designs using a modified Earnshaw.  They are pretty simple to make compared to the grasshopper.  On this one I am going to try to pivot both the pallets at the same point.  A little difficult on a small movement with wood.

I would like to see how you managed the rementoire.  Was it gravity with an endless chain?  The bow clocks are great to look at but wildley innefficient time keepers.  Even if you get the fusee right, the bows take a set over time and loose power.  I hope you are having as much fun as I am.

JR

Offline rabbit

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New Clock
« Reply #3 on: January 16, 2006, 09:29:35 AM »
My "Dent" clock has a remontoire. This movement employs a gravity driven train remontoire. This is one of the few clocks I have pictures of - it's on my 'website', and you can sort of see the remontoire.
I figured out how it works from a good explaination (and 4 movies) at this website:
http://www.my-time-machines.net/wagner_detail.htm
I basically copied this design. To my surprise, it worked wonderfully on the first try; and it's so cool to watch.
The reason I suggest a gravity escape is because it's also perfect for a spring-powered clock. As long as there's enough power to resest the gravity arms, any variation in power won't change the timekeeping. This is also true with the remontoire, and you wouldn't need both, and either one eliminates the need for a fusee.
I love the grasshoppers, but the problem with them is that ANY variation in power will greatly affect the timekeeping.
- rabbit

Offline jrbeall

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Upside down and gravity
« Reply #4 on: March 17, 2006, 02:57:37 PM »
I have taken your advice, Rabbit.  The gravity clock is nearly finished.  See comments under "Other Escapements"

     The upside down pendulum clock is all done and running along fine.  It is not a great time keeper.  It uses a Negator motor but even that varies considerably from up to down.  The adjustment of the magnets and the pendulum are both criticical and very sensetive but the grasshopper works great and is the smallest one I have yet built.

Offline jrbeall

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Negator spring motors
« Reply #5 on: May 11, 2006, 05:06:24 AM »
I have finished the gravity clock which runs fine and keeps good time.  I like it about as much as the grasshoppers.  I am disenchanted with the "Negator" motors though.  They are expensive, $35 and they don't hold up well.  Two of the ones I ordered were DOA.  One that I had in a working clock got tangled and quit.  They are poorly engineered and haven't much power.  I have ordered several clock springs from La Rose, Less than $6 each, and am working out how to mount them.

I have designed a new clock with a remontoire and a sweep second hand.  The frames are cut but haven't started the wheels and pinions yet.  It probably won't work but I am having fun.

Dave

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New Clock
« Reply #6 on: June 02, 2006, 02:29:45 PM »
Hi Rabbit it is true that the grasshopper is at risk from variable power but only when using a compound pendulum. Some years ago, i half made an experimental skeleton clock, i lost interest and placed it on the shelf. A friend bought the clock and finished it to a high standard. It is full of ball races and has a pendulum that is clamped to the pallet arbor, (no suspension spring). He has said that he will never part with the clock and it never needs adjustment from one week to the next, regards dave

Offline rabbit

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New Clock
« Reply #7 on: June 03, 2006, 08:10:08 AM »
hi, Dave -
'glad to see you here. (it was very quiet on this forum for a long while...)

the grasshopper isn't sensitive only with a compound.  it's a matter of that pesky "Q-factor" (related to the forces that return the pendulum to "down" and the frictional losses...)
because a grasshopper is essentially in constant coupling with the pendulum, it can "force" a low-Q pendulum both ways at a rate that it wants to - because it contributes significantly to that "returning" force.  compound's typically have low Q.  so does a short, light simple pendulum.  a heavy, well-suspended pendulum (high-Q) can "control" the grasshopper instead of vice-versa, because it's returning force is proportionally much higher compared to the force from the escape.

i still love 'em, but it's a matter of application.
- rabbit

Dave

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New Clock
« Reply #8 on: June 03, 2006, 09:54:42 AM »
Hi Rabbit, i forgot about the pesky Q factor, i wouldn't care but i have a good example in my sitting room. My grasshopper wall regulator has a heavy one second pendulum and keeps reasonable time. It could do better but it is open for all to see and does not have a case, i am sure that shmbo has the occasional poke with a feather duster when i am not looking, Dave

Dave

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New Clock
« Reply #9 on: June 06, 2006, 03:44:14 PM »
Hi JRB and Rabbit, reading through your messages about spring power or lack of it, i thought i would explain how my regulator works. I got the idea from J Wilding who used the method for driving a turret clock, it is non invasive from a restoration/historical point of view. The wheel count is attributed to Ferguson and is, Main wheel 120Tx3mod, centre/2nd wheel 120Tx2mod and 2x escape wheels of 6 inch dia and 3 inch dia, each 90 T. On my clock a lever is free to rotate on the lower wheel arbor (14 inch dia) and a motor with internal gearbox is fixed on it outer edge. The motor shaft has a lantern pinion which is in permanent mesh with the left hand side of the wheel. The weight of the motor drives the clock and as the wheel rotates a mecury tilt switch kicks in and power is given to the motor which climbs up the teeth of the main wheel. On my clock this happens about every 70 minutes and it takes 25 seconds for the motor to climb back to its starting position, regards Dave