Grasshopper Escapement Clock

[asever]

Mind if I ask what wood you used to make the gears? My guess is European beech. I understand ply is the best to minimize the expansion and contraction; but for some reason the thought of using plywood gears next to the hardwood just goes against my sense of style. From what I have read you can get away with using some of the more stable woods (I suppose it would also depend on the climate, and where the clock is displayed).

Thanks again for sharing.

Andy

[pcstru]

@Andy,

The gears are a 4mm 5ply mahogany "marine" plywood. For the main gears I cut two of each and bond them together to end up with 8mm 10ply - partly because I find the sheet isn't perfectly flat and the bonding tends to sort that out and partly because you need some depth to the material otherwise they will not end up perpendicular to the arbour. The problem with using wood is that the gear teeth are quite fine and from a single piece of wood you will get teeth with the grain running across the tooth (unless you cut the gear in multiple parts which is ... just a pain!). So they will break quite easily. Ply also has the advantage of being more dimensionally stable over long periods of time - but that's compromised in a way by cutting the frame pieces from a single piece of oak. If that starts to deform, the stability of the gears won't matter.

I get what you are saying about using plywood against the nice oak, on the other hand it is high quality stuff, wickedly more expensive per cubic foot than the oak and the mahogany seems to give about the right contrast. Even from the side the plywood looks reasonably nice - the individual laminates are so thin it is difficult to distinguish them.

[Norb]

I just bought clock #7 from Brian Law's Wooden Clocks site..... US$ 10 for the DXF and PDF files.

Essentially in imperial measures it is very easy to convert to metric for those who prefer the latter. Set up the job in inches, import the DXF and change the job to mm. Couldn't be easier.

While looking around for close-grained and well seasoned wood, I will probably do one first in Corian or similar with some wooden accent pieces.

[wbegg]

Thank you very much, now I have to spend the next 30 days studying clock movements and construction. Darn this A.D.D.!!

[woodmouse]

Simply brilliant....

[dgoodyear]

I have been working on a clock of my own design and I am looking for some pointers. I am using gearotic for drawing the gears and cut2d for generating the toolpaths. I am just wondering...do you generate your toolpaths so the gears will be a little smaller than you wish, that way they will not bind? or do you just sand until they work?

Thanks. any input would be appreciated.

[pcstru]

I have been working on a clock of my own design and I am looking for some pointers. I am using gearotic for drawing the gears and cut2d for generating the toolpaths. I am just wondering...do you generate your toolpaths so the gears will be a little smaller than you wish, that way they will not bind? or do you just sand until they work?

I've not used gearotic. The grasshopper clock was made from profiles generated by the "radial vector program" found here. It generates pairs of cycloidal profile gears with appropriate spacing, so provided you take the pairs and centre them appropriately, there should be little need for sanding (other than to clean them up (unless you have accuracy or cutting issues with your CNC machine)).

Good luck with the design and build! Glad to help if I can.

[cabnet636]

WOW is a good start!!!

[dgoodyear]

I am currently working on a clock with a grasshopper design. I am unsure about a maintaining mechanism for the clock. Does your clock use a maintaining power mechanism to keep the clock running while rewinding? How do you keep the gear train from turning as you rewind?

Thanks,

DJG

[pcstru]

Does your clock use a maintaining power mechanism to keep the clock running while rewinding? How do you keep the gear train from turning as you rewind.

There is no maintaining mechanism on the clock. The weight drives the great gear via a ratchet and the gear itself is not 'tight' on the arbour - so doesn't want to drive the mechanism backwards which would cause problems. It does lose time while winding - but it's not a regulator quality timepiece so a few more seconds a day inaccuracy is not a worry.

[jmkissell]

Great clock!
Do you have trouble with the thin wood of the gears warping?
How do you over come that problem?
Thanks.

[pcstru]

No trouble with gears warping (yet!). I use high quality marine plywood - even the 4mm is a 5 ply, very stable but quite expensive.