Shopsmith Forums

JPG40504 wrote:Why does this sound familiar?

http://fordr533.tripod.com/glclub/id4.html

paulrussell wrote:http://fordr533.tripod.com/glclub/id4.html

Actually I have a vague recollection of Farmer saying the same thing!:)

P.S. Thank You for that link Brother!

paulrussell wrote:A while back I bought a small CNC machine (see the BluumaxCNC thread) with dreams of making wooden clocks & puzzles.

Paul, how does your ~$400 CNC work for wooden clock gears? That's one of the reasons I was using to justify my purchase of the laser engraver (other than to supliment my sandcarving/engraving hobby). Only problem, I'd have to go with at least a 60Watt laser to vector lase wood thick enough for clock gears, and that's going to be in the $25-35K range.

tom_k/mo wrote:Paul, how does your ~$400 CNC work for wooden clock gears? That's one of the reasons I was using to justify my purchase of the laser engraver (other than to supliment my sandcarving/engraving hobby). Only problem, I'd have to go with at least a 60Watt laser to vector lase wood thick enough for clock gears, and that's going to be in the $25-35K range.

"Helical gears" might be a problem(2.5D).

JPG40504 wrote:Actually I have a vague recollection of Farmer saying the same thing!:)

I have gotten a lot of years of good out of "grand-dads hammer". I used it as a sig line for quite a while.
.
I really do have grand-dads hammer, actually several of them and almost all of them have both original parts.
We gave our grown son all of the wooden planes (including a good assortment of molding planes), wood and brass bit brace and some other tools that belonged to one of my great great grandfathers. He had used them among other things to build a house about 3 miles southeast of here including all of the walnut trim in the house.

JPG40504 wrote:"Helical gears" might be a problem(2.5D).

Paul, most of the laser engravers come with a rotary attachment so you can engrave/cut on cylindrical objects. I would think you could cut them with that by cutting down on the tooth. It would be a lot more difficult though in adjusting the wattage to get the exact depth of the tooth. Cutting from the side, it's a simple vector cut and cut all the way through.

tom_k/mo wrote:Paul, how does your ~$400 CNC work for wooden clock gears? That's one of the reasons I was using to justify my purchase of the laser engraver (other than to supliment my sandcarving/engraving hobby). Only problem, I'd have to go with at least a 60Watt laser to vector lase wood thick enough for clock gears, and that's going to be in the $25-35K range.

I'm on my cell phone at the moment, resting from too many miles afoot at the local art fair, so links will have to be later.
As far as using a laser for wooden clock gears, see Brian Law's wooden clock site for a discussion of low cost lasers & clock wheels.
The Bluumax is fully capable of making clock gears. The secret is a sharp, quality end mill and a slow feed rate. I'd say in the neighborhood of 7 inches per minute. A Dremel is sufficient. Faster is possible, but gantry flex (accuracy/repeatability) can occur if you push too far.
There are some repeatability hints I'll write up if/when anyone else gets a Bluumax.
If you go to http://www.bluumaxcnc.com and follow the link to the forums, Steve Hobley has posted pics of his clock build, and he has the completed clock and a discussion on his homepage (links to follow in a later post)
Helical gears require a 4th axis or cnc lathe. Some 2.5d CAM software supports a 4th axis and/or lathe (I believe Dolphin does). Adding a 4th axis is a very popular DIY project.

JPG40504 wrote:Actually I have a vague recollection of Farmer saying the same thing!:)

P.S. Thank You for that link Brother!

Brother, I was just looking for the Lincoln story & hadn't even read the rest of the page!!

Believe it or not, there were a few clocks made with helical gears, for the most part I think it was more trouble than it was worth. On wooden wheels it would worse than useless.

CNC would be handy if making a production run of wooden clock wheels. However for the average hobbyist you could get by with far simpler tooling. While most clock teeth are cycloid and not involute profiles, traditional wood wheels are simpler still. As I am working on a presentation on this very topic I have photos...

Hand cut teeth, these can be fairly fine as in this example:
[ATTACH]8994[/ATTACH]

Or quite crude.
[ATTACH]8995[/ATTACH]

Typically these are found on earlier clocks but do appear on later examples. There were quite a few makers who only made a handful of clocks, farmers and others trying to make a living during the winter months.

In mass produced clocks, a few used teeth milled with a single cutter, these have a rounded space between the teeth.
[ATTACH]8996[/ATTACH]

Most were made with circular saw blades and a cutter to round the tip of the tooth, the two blades and rounding cutter were run through a stack of wheel blanks, cutting one complete tooth on each pass. Thousands of clocks with these movements were made.
Note the peak left by the two circular saws between the teeth.
[ATTACH]8997[/ATTACH]

The point is (yes there is one) that conventional gearing and extreme precision can be detrimental in a wood works clock. This simple tooth profile gives maximum strength at the root where it is needed and has withstood the test of time. Even with quartersawn lumber the dimensional variations mean that designing to extreme tolerances will produce nothing but headaches. In the wood works community there is a saying, if it will rattle it will roll.

Troy

horologist wrote: The point is (yes there is one) that conventional gearing and extreme precision can be detrimental in a wood works clock. This simple tooth profile gives maximum strength at the root where it is needed and has withstood the test of time. Even with quartersawn lumber the dimensional variations mean that designing to extreme tolerances will produce nothing but headaches. In the wood works community there is a saying, if it will rattle it will roll.

I take very strong issue with this. Perhaps as a matter of terminology, but none-the-less I disagree.

If your argument is that redesigning a wooden clock to metal clock standards and dimensioning is detrimental, then I will agree.

However, tolerances and extreme precision are not detrimental to correctly designed wooden clock gears. How in the world could making something less in adherence to its design possibly be an asset?

A CNC cut wooden clock gear IS superior to most hand cut gears when the gears are properly designed.

The clock wheels you display in your post appear to be, or are very similar to, those from the medieval "Verge and Foliot escapement" design clock. I saw many of these on display during a recent trip to Germany, and they were the origins of my interest in wooden clocks. The accuracy of these clocks was so poor, that they had only a single hour hand. The medieval woodworker had a different system than the woodworker of today. Today, we cut many parts in advance, to high degrees of accuracy and precision, and then expect them to all fit together as designed. The medieval woodworker, not having our abilities of consistent repeatability, had to make part 1, and then build part 2 to fit part 1, and so on and so on.

The modern wooden clock with a long pendulum, is a very accurate timepiece. The roughly hewn teeth shown above would have no place in their construction.

Take a look at the state-of-the art wooden clocks here: http://lisaboyer.com/Claytonsite/Claytonsite1.htm and see how many roughly hewn gear teeth are in evidence.