Wooden Gear Clock!

[Michael Mathews]

I never would have attempted this without the encouragement from Joe Carr! I started simple with a 6 RPM Synchronous 120 VAC motor, readily available on Amazon very cheap. From 6 Rpm you just have to figure out the gear ration to work up to 1 RPM for the Seconds Gear. (Reference the Excel Spreadsheet image). Looking at the columns in YELLOW, the number outside the parenthesis is the number of teeth and the number inside the parenthesis is the Pitch Diameter (PD). I did all the design from scratch in Fusion 360. Knowing the PD of two adjoining gears makes the design easy. The PD becomes two tangent circles. So, figure out the ratios for each gear set. Oh, let me finish how to read the YELLOW columns. The 6RPM motor has a 10T (tooth) gear, meshing with a 10T gear, which then meshes with a 20T gear. The 20T gear has an 8T pinion gear on the same shaft that meshes with the 24T gear. The 24T gear is the SECOND hand gear that rotates at 1 RPM. Jumping over to the Minutes YELLOW columns, the first 8T gear is a pinion gear on the 24T SECOND hand gear, and so on. Hopefully this makes sense. Reach out to me if you want to try this and I can help you understand my spreadsheet better.

NOTE: After building the clock according to the spreadsheet below I discovered an error in my calculations! If you work through the gear ratios from the Minute gear to the Hour gear, it works out that the Hour gear will rotate once every 24 hours NOT 12 hours! I discovered this AFTER completing the clock the first time! So I took apart the gear train and reworked it for a 12 hour gear. So the ratios below are INCORRECT!!!

So this is my Fusion design using PITCH DIAMETERS from the above spreadsheet. I was just laying out the gears in a manner to try to keep everything as compact as possible yet not have a gear axle run through a rotating part of another gear. Here you can see that using the PD makes designing the layout much easier than trying to create a gear for each part then place them meshed.

After I was happy with the layout I created the first several gears in Vcarve Pro and cut them out on my ShopBot Desktop Max CNC along with the calculated axle center points to confirm I had enough slop so the gears would turn without too much friction.

Beginning assembly! You can see the motor shaft in the first 10T gear.

I wanted to add a bit of fun to my clock so this is what the Minutes, Seconds, and Hours gears look like!



More assembly pics:



The finished clock:

Comments and questions are expected and welcome!
This was VERY challenging but extremely rewarding! At times I was on the verge of quitting but Joe helped me over the hurdle many times! Thank you Joe!!!

 

[jlwest]

Great project!!!!

 

[Wilsoncb]

Thanks for sharing, it looks great and you have successfully intrigued me…so I have questions. Please don’t interrupt my questions as being critical, rather I have some pre-conceived ideas that are getting in the way of understanding what you did.

I understand pitch diameter, but I’m trying to understand how you end up with numbers that appear to be rounded. Correct me if I’m wrong but all gear teeth need to match with gears they mesh with. Therefore you have somewhat of a fixed tooth size and spacing? (Or can the spacing be adjusted?) Ultimately it’s about the ratio, so if your tooth size was half the size you chose, the pitch diameter reduced as well. So I’m guessing the exercise becomes defining the PD based on tooth quantity and spacing? This seems like it would result in PD that was a real odd ball number like 2.4367 vs. 2.5. However, what you described appears like you picked round numbers and made it work from there.

Next question, you said you used a 6 RPM Synchronous 120 VAC motor. Does that motor have any way of fine tuning the speed?

 

[drw]

Wow! Wonderful project! You engineers do some amazing work; what would frustrate many of us only seems to energize you! Thank you for posting.

 

[Michael Mathews]

Thanks for sharing, it looks great and you have successfully intrigued me…so I have questions. Please don’t interrupt my questions as being critical, rather I have some pre-conceived ideas that are getting in the way of understanding what you did.

I understand pitch diameter, but I’m trying to understand how you end up with numbers that appear to be rounded. Correct me if I’m wrong but all gear teeth need to match with gears they mesh with. Therefore you have somewhat of a fixed tooth size and spacing? (Or can the spacing be adjusted?) Ultimately it’s about the ratio, so if your tooth size was half the size you chose, the pitch diameter reduced as well. So I’m guessing the exercise becomes defining the PD based on tooth quantity and spacing? This seems like it would result in PD that was a real odd ball number like 2.4367 vs. 2.5. However, what you described appears like you picked round numbers and made it work from there.

Next question, you said you used a 6 RPM Synchronous 120 VAC motor. Does that motor have any way of fine tuning the speed?

This is the Spur Gear Generator that's built into Fusion. Notice that I cannot change the Pitch Diameter. I can however change the Diametral Pitch which effects the PD. Once I found a Diametral Pitch that worked for the size of gears I was working with, I kept the value the same for all gears and the PD always worked out to a good round number or to one decimal place.

The motor does NOT have any tuning. Since it's a synchronous motor, it syncs to the AC Waveform that the 120 VAC is carried on. So 60 cycles per second. It's very reliable and very accurate!

 

[Wilsoncb]

This is the Spur Gear Generator that's built into Fusion. Notice that I cannot change the Pitch Diameter. I can however change the Diametral Pitch which effects the PD. Once I found a Diametral Pitch that worked for the size of gears I was working with, I kept the value the same for all gears and the PD always worked out to a good round number or to one decimal place.

The motor does NOT have any tuning. Since it's a synchronous motor, it syncs to the AC Waveform that the 120 VAC is carried on. So 60 cycles per second. It's very reliable and very accurate!

Wow, that’s a nice little tool!

 

[Echd]

Very cool! How about a video of it in action?

 

[mattfrit]

Just about to request a video as well.

Also, at the risk of embarassing myself, how do you read the current rime?

 

[Michael Mathews]

Just about to request a video as well.

Also, at the risk of embarassing myself, how do you read the current rime?

read the numbers at the top, or closest to the top of each gear.

 

[Michael Mathews]

Here's the clock running! Sorry about my background noise. I'm not used to shooting video. Yes, the clock does make some grinding and whining noises. I find it quite pleasant! I hope you can enjoy it as much as I do!

 

[JNCarr]

Excellent piece, Michael! Congrats!

 

[Michael Mathews]

Excellent piece, Michael! Congrats!

Thank you Joe for all your help figuring out the details!

 

[Mike Davis]

I get the rabbit and the turtle, but what is the other animal?

 

[Michael Mathews]

Salamander or lizard. I tried to pick the three animals from the fastest to the slowest

 

[gesiak]

Michael, that's not only interesting, but excellently done.

 

[Henry W]

I would need to enclose that in a glass case, because our cats would be endlessly fascinated by the movement (and the grinding and whining noises). Mayhem might result.
Nice work Micheal - love the engineering and woodworking here.