Involute gear clock

dewbane

Michael McIntyre
H-M Lifetime Diamond Member
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I've become intrigued with the idea of building a clock using involute gears. I've found some references to experiments done on bomb timers that suggested there was no disadvantage to using involute gears in clockwork mechanisms, and I just want to give it a whirl. The worst thing that could happen is the clock doesn't run well, which would put it on a par with every other clock I've built so far.

The other problem I want to address is the size limitations of the material I can realistically work with. All the clocks I've built to date have been wooden kit clocks, and they have all had relatively huge wheels. If you want to make, say, an 8" wheel out of brass, then you need a piece of 8" diameter stock. I haven't priced it, but I can already tell you that it's just stupidly expensive. Even aluminum in bigger sizes like that is stupidly expensive. A quick search turned up a price of $150 an inch for aluminum and brass only went up to 4" on that site, which is $90 an inch. Ouuuch.

So I want to use involute gears, and I want to limit the maximum size to something affordable, like 2" diameter. I also want to build some real chimes into this crazy thing. Forget Westminster, I want it to play a melody I wrote for a dungeon game a long time ago. I've been following the Marble Machine X build on Youtube for the last two years, and I guess I'm inspired to make a mechanical thingie that plays some music I wrote.

So at this point, I'm really just daydreaming. I finally pulled the trigger on the dividing head I've been talking myself out of buying for years. The only reason I even want to learn how to make gears, is because I've always been fascinated by mechanical clocks. I wear a little one on my wrist every day, even though my phone tells much better time.

I'm not even married to a mechanical escapement. I might consider something crazy, like a fancy brass mechanical hoopty do that's driven by a quartz crystal. I guess I'm just trying to think way outside the box here, and come up with an all-consuming mad scientist type project to help me deal with fall depression for the next 50 or 60 or 180 years, until I finally get a working prototype finished. I mean, sitting here having never cut a gear in my life, and dreaming of impossible craziness.
 
I've become intrigued with the idea of building a clock using involute gears. I've found some references to experiments done on bomb timers that suggested there was no disadvantage to using involute gears in clockwork mechanisms, and I just want to give it a whirl. The worst thing that could happen is the clock doesn't run well, which would put it on a par with every other clock I've built so far.

The other problem I want to address is the size limitations of the material I can realistically work with. All the clocks I've built to date have been wooden kit clocks, and they have all had relatively huge wheels. If you want to make, say, an 8" wheel out of brass, then you need a piece of 8" diameter stock. I haven't priced it, but I can already tell you that it's just stupidly expensive. Even aluminum in bigger sizes like that is stupidly expensive. A quick search turned up a price of $150 an inch for aluminum and brass only went up to 4" on that site, which is $90 an inch. Ouuuch.

So I want to use involute gears, and I want to limit the maximum size to something affordable, like 2" diameter. I also want to build some real chimes into this crazy thing. Forget Westminster, I want it to play a melody I wrote for a dungeon game a long time ago. I've been following the Marble Machine X build on Youtube for the last two years, and I guess I'm inspired to make a mechanical thingie that plays some music I wrote.

So at this point, I'm really just daydreaming. I finally pulled the trigger on the dividing head I've been talking myself out of buying for years. The only reason I even want to learn how to make gears, is because I've always been fascinated by mechanical clocks. I wear a little one on my wrist every day, even though my phone tells much better time.

I'm not even married to a mechanical escapement. I might consider something crazy, like a fancy brass mechanical hoopty do that's driven by a quartz crystal. I guess I'm just trying to think way outside the box here, and come up with an all-consuming mad scientist type project to help me deal with fall depression for the next 50 or 60 or 180 years, until I finally get a working prototype finished. I mean, sitting here having never cut a gear in my life, and dreaming of impossible craziness.
Looking forward to following your build. Maybe prototype with something more reasonably priced?

Tell me about the price of brass. I haven't finished a tripod mount for a project that calls for a 5" round 4" long at $300. Considering other options.

Bruce
 
What material is more reasonably priced? Seriously, after doing a little checking, I'm starting to be of the opinion that the only reasonably priced material out there is good old Virginia clay mud. What kind of relief angle do you need to grind on your tool when cutting mud? :p

I don't know, man. The vapor potential of this build is pretty high, but watching a train wreck can be fun.
 
Don't know if it'll work for you, but Menards sells polyethylene sheets. A 24" x 36" x 0.220" thick is $27 (search their site for AmeriLux). Another option is plastic lumber. They sell it in 8' and 12' lengths, looks like it's probably recycled polyethylene. Standard dimensional lumber sizes from 2 x 4 up to 2 x 10 ($34 for a 2 x 10 x 8'). I've used the plastic lumber for trial parts for CNC cutting, machines well. I'll cut it to rough size on a table saw and have at it on the mill.

Bruce


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Keep an eye on the temperature coefficient of the material; some plastics are pretty bad in that respect. Depending upon the size and tolerances, you can end up with a clock that binds up when it's warm out.
 
If you want to make, say, an 8" wheel out of brass, then you need a piece of 8" diameter stock. I haven't priced it, but I can already tell you that it's just stupidly expensive. Even aluminum in bigger sizes like that is stupidly expensive. A quick search turned up a price of $150 an inch for aluminum and brass only went up to 4" on that site, which is $90 an inch. Ouuuch.


Couldn't you just get plate and cut the starting circle that you want for the gear?
....well that would work for aluminum, I have never seen thick brass plate.
-brino
 
If made from brass, how thick does the stock have to be? Just for a quick check, I went to online metals and priced their 1/8" thick brass sheet, $76.34 for a 12x12 piece. That's for 260 soft annealed. The most expensive is 353-H02, $139.20. These guys aren't necessarily the cheapest, I just picked them out of a list I have of online metal suppliers.

Aluminum sounds like a bad idea to me, problematic due to galling. A36 cold-rolled is $13.60 (but perhaps not good since it's easily magnetized?). Depending on the alloy, stainless can cost less than to more than brass. Again, based on one supplier's pricing, so probably not the cheapest.

Maybe the issue regarding using sheet stock is flatness? Generic sheet stock probably isn't all that flat.

Going back to wooden clocks vs. ones with plastic gears, plywood has a temperature coefficient of expansion, too. Choosing a plastic with a similar tempco would likely work (aside from strength considerations). Nylon gears show up in all kinds of commercial applications so that might be something to consider. McMaster will sell you a 12 x 12 inch piece of 1/8" thick 6/12 nylon sheet for $34.31.

Just to throw more variables into the mix, you could choose something cheaper for the big gears and go with more eye-appealing (and expensive) materials for the smaller ones. If that matters.
 
The plastic goods above were suggested merely for prototype cuts. I hate to make my first attempt at something new with a multi hundred dollar piece of material. Just my inexperience, but if it's pricey or a dicey operation, I typically do a practice piece first. One advantage of being a hobby machinist and not working in a production shop.

No question you'd want metal for the gears. I don't think you'd even see a Chinese clock with plastic gears.

Bruce
 
Aluminum actually slips nicely against steel. So a large aluminum gear and a smaller steel one would be a good match.
Here's a crazy idea: a huge gear with bolted on teeth. Each tooth made and attached separately. Whoa. Picture that.
-Mark
 
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