Grasshopper Clock

[John T]

OK, OK, I won't win any awards for beauty but then that wasn't my goal.  I wanted to use a one second pendulum on the grasshopp er to see if there would be enough "power" to run it.  The grasshopp er requires a little recoil in order to free whichever pallet is engaged and that consumes some energy.

Anyway I have been able to do it (you can see I reduced the counterwe ight on the entry pallet quite a bit and I could do more but it works)  The pendulum rod is quite stiff and thick to ensure the required recoil and so the overall length of the pendulum in 51 inches and that gives me a one second pendulum.  Its still a work in progress but the difficult part of getting the escapemen t to beat once per second is done.

[Mooselake]

Very nice, John!

Is that lower gear 3/8" and the rest quarter inch?  That looks like quite a ratio from the drive weights to the grasshopp er, too.

Kirk

[John T]

Hi Kirk
The gear set is from Ward L. Goodrich's book called "The Modern Clock" (1906).  It is far and away the best book I have read on clock design.  In the book he reference s his ideal "regulator".  It is designed to be build of brass and so wood is definitel y a stretch - especiall y for pinions.  Anyway his design was as follows:

The escape is 30 teeth with a one second pendulum giving one rotation per minute.
All pinions are of 12 leaves
The number 3 has 90 teeth
the number 2 has 96 teeth
The hour wheel 144
and the great wheel 144 as well.
Depending on the barrel used on the great wheel you'll get from one to three months on a winding.  When building of wood I'm trying for a week perhaps before I exceed the strength of the wooden pinion.  The escape and number three wheel are of 1/4 inch while the number two is 3/8" and the the hour wheel is 1/2" (driving a 1" pinion"

I know I'm pushing the boundarie s but then why not?

John

[BobL]

John;

 Awesome clock,  this one will turn heads once your all done with it. Nicely done and thanks for sharing.

Cheers
Bob

[Mooselake]

If the boundarie s weren't worth pushing then we'd buy all our clocks at WalMart, and they'd keep virtually perfect time and run for years on a cheap battery.

I'll take a look at at the book.  While dead tree reprints of the actual book are available they're pretty pricey - doesn't seem to be a mass market paperback .  Since it's out of copyright I found a legal download source (which even has kindle versions), a scanned copy from Boston College Library at:

http://www.archive.org/details/modernclockstudy00good

I hadn't realized that epicycycl oidic teeth would allow a bigger endmill - i'm limited to a 6" diameter with my mini-router.  If the display screen is correct I can cut a 25DP 144T gear that's just a hair under 6 inches.  I've got some baltic birch plywood already ordered, perhaps the ZB would cut a gear that won't strip the first time it was loaded.

Thanks a lot John!  Liked the workshop in the backgroun d, too.

Kirk

[John T]

Hi Kirk,
Thanks for the reference to the downloada ble pdf of Goodrich's book.  I had scanned my hard copy just to be able to have it in electroni c form but my scanning isn't all that great. Now I've downloade d the pdf and its great.  Thanks again.

John

[John T]

It isn't officiall y a "clock" until it has a face and hands.

[BobL]

It isn't officiall y a "clock" until it has a face and hands.

LOL 

 This project is take shape...l ooking good...

[Steve Truscott]

Hi
I made a mock up of a clock very similar to this to see if it would work. Used 3mm hoop pine which wasnt a good idea, not rigid enough. Anyway the escapemen t worked properly when the parts didnt twist out of alignment .
Question though, with the solid stop when the pallet is fully engaged the pendulum goes clunk and stopped with some impact. Pervious grasshopp er designs I made have had a spring stopper.
Has your clock stood up to these impacts.