Lets try this. Anyone wanna take a look at my DXF Files for me???

[KKC]

Here are 2 attempts at drafting wheels in AutoCAD.  If anyone is able take a look and let me know your thoughts.

[steve323]

Hi KKC,

I would love to see the wheels, but I don't have a dxf viewer on this PC.  Are you designing your own clock?  That is my goal as well and my first (and only) clock is my own design.

Steve

[millerdlca]

Hi KKC,

I'm curious about how you created these.  Looking at the 60 tooth wheel, the teeth don't look like cycloidal forms.  The tooth sides inside the pitch circle are normally a radial line for the the pinion tooth top to roll on, but these seem to be a continuous curve.  The pinion looks more like a normal pinion tooth form.

If you want, you could compare to the forms generated by these tools which generate dxf or svg outputs:
http://www.hessmer.org/gears/CycloidalGearBuilder.html
http://www.hessmer.org/blog/2012/01/28/cycloidal-gear-builder/

Here is info on the theory:
http://www.csparks.com/watchmaking/CycloidalGears/

I don't know much about escape wheel design so I won't comment on it.

Dennis

[KKC]

Thanks Dennis I'll do some looking at your links.  I'm trying to learn how to design clocks.  I have AutoCAD and I just drew a gear.  Didn't realize they had to be Cycloidal.  I look into that. 

[KKC]

Hi KKC,

I would love to see the wheels, but I don't have a dxf viewer on this PC.  Are you designing your own clock?  That is my goal as well and my first (and only) clock is my own design.

Steve

I am trying to design my own clock Steve.  All kits and plans are copy righted and I can't sell them.  If I can design them myself I can sell them.  Of course it appears the market is more about selling plans and kits rather than finished clocks.

[millerdlca]

Hi KKC,

The teeth don't have to be cycloidal but that is the traditional tooth form for clocks.  Involute gears could be used but they have a serious disadvantage for low tooth count pinions and they just look wrong in a clock.  The csparks website has a good discussion on gear design.

There is an interesting thread on the ShapeOko CNC forum on clock design.  The thread doesn't yet come to a conclusion on the build but the early material especially could be useful to you on doing design and gear counts:
http://www.shapeoko.com/forum/viewtopic.php?f=30&t=6186

Dennis

[KKC]

Thanks Dennis that's a great link.  But it's going to take some time to read the whole thread. 

[KKC]

How bout this one? Take a look and tell me what you think guys.

[steve323]

Hi KKC,

I loaded a dxf viewer on this PC.  Here are my comments.

I like the graceful curves of the 60t center wheel.  The large radius curves on the cutouts look best (to me) for wooden clocks.  They are also easier to cut out and sand.  The diameter of the center hub should be sized to match the size of the pinion that is attached to it.

I prefer the 5 spoke design of the hour wheel instead of the 4 spoke design on the 60t center wheel.  I saw someone else post that odd numbers are more pleasing to them.  I agree.  The only change would be to increase the radius where the arms meet the outer rim.  My thinking is that the size of your router bit should determine the size of the gear teeth.  A 1/8" router bit would be able to cut a 60 tooth wheel with a diameter of around 4-5".  The curves in the spokes should have a radius that can be cut by the same 1/8" router bit.

I am still struggling with escapement designs in my head.  The "shoe" style escapement seems common on wooden clock designs, but looks too delicate (to me) in a wooden clock.  My personal preference is for the "slanted triangle" shape of escapement.  Sorry if I don't know the proper names.


Regarding your other question regarding gear tooth profiles.  I have read that there are many tooth profiles that have only rolling friction when the teeth mesh.  Two styles have become popular.  The cycloidal shape is traditional and has an advantage that it is very tolerant of meshing as the clock wears and the gears move apart slightly.  I was replaced by the involute shape when machines started cutting the gears.  Involute gears are easier to make by machines.  I don't think it matters which one you use.

I like that you are designing your own clock.  To me, this is the most challenging part.

Steve

[KKC]

I would agree.  This learning why and how and what goes into a clock (to me) is hard.  There are days I'm discouraged and just kind of let it sit.  Then there's days when I have an "Uh Ha" moment and it's thrilling.  So... Maybe someday I'll get this all figured out and get something that actually keeps time build and working.  I plan to make the Woodline clock this spring and summer once it warms up.  I have a feeling that will shed a lot of light on the entire process and help me better understand the big picture. 

Now the DXF files I've been posting is experiments I am doing with AutoCAD.  I can create a tooth I like and then use a command called "array".  I tell it how many time to repeat the shape around what radius and it draws it.  So if I can find a winning tooth shape and the proper tooth count I'll be able to create them fairly quickly. 

[steve323]

That is the same way I created gears in TurboCad.  There are a few gear profile generators out there.  I used the version from woodgears to generate the basic profile, then imported the image to TurboCad and re-generated half of a tooth to array into a full gear.  This created a cleaner profile.  The original output from woodgears was made with thousands of tiny line segments.  I simplified each tooth into a few basic arcs.  Each tooth is going to be sanded, so the profile only needs to be reasonably close to a perfect involute or cycloid shape.

I just found a program at geargenerator.com that looks like it could be used to model the entire gear train of a clock.  You can add ad many gears as you like.  All the parameters for each gear can be specified including which gears are on the same axle and which other gear it connects to.  It also animates the rotation at any speed you like.  The only thing missing is the escapement.

Steve

[steve323]

I just found a program at geargenerator.com that looks like it could be used to model the entire gear train of a clock.  You can add ad many gears as you like.  All the parameters for each gear can be specified including which gears are on the same axle and which other gear it connects to.  It also animates the rotation at any speed you like.  The only thing missing is the escapement.

Steve

Here is a model of my clock design gear train using geargenerator.com.  Hopefully, the link will come through.  It includes all the parameters for 10 gears.

http://geargenerator.com/#60,60,60,10,1,9,40356.23543000015,10,1,10,1,10,20,0,0,0,50,5,10,20,-45,1,1,10,1,10,20,-90,2,0,50,5,10,20,0,3,1,12,1.2,10,20,0,4,0,48,4.8,10,20,-120,5,1,12,1.2,10,20,0,6,0,48,4.8,10,20,-90,7,1,15,1.5,10,20,0,8,0,45,4.5,10,20,-90,0,0,2,-2292

Gear 0 is attached to the 18 tooth escapement.  It rotates once every 36 seconds with a 1 meter pendulum.
Gears 0 to 1 have a 5:1 ratio, so gear 1 and 2 rotate once every 3 minutes.
Gears 2 to 3 have a 5:1 ratio, so gear 3 and 4 rotate once every 15 minutes.
Gears 4 to 5 have a 4:1 ratio, so gear 5 and 6 rotate once per hour.  This drives the minute hand.
Gears 6 to 7 have a 4:1 ratio, so gear 7 and 8 rotate once per 4 hours.
Gears 8 to 9 have a 3:1 ratio, so gear 9 rotates once per 12 hours.  This drives the hour hand and would be placed over the axle for gear 5.  The diagram shows it below to keep the diagram uncluttered.

Steve

[KKC]

Dude that is sweet!!! Is that website free???

[KKC]

That gear generator is really cool... You could model you entire idea to see if it would even work in theory.  Which is basically what you did. Great find Steve.  I'm going to have to really play with this.

[steve323]

Yes, the program appears to be free.  It is way cool.

Here is a model of a traditional clock with 60:8 and 64:8 gear trains.

http://geargenerator.com/#80,80,80,10,1,5,59135.835429999934,8,1,8,0.8,10,20,0,0,0,60,6,10,20,-45,1,1,8,0.8,10,20,-90,2,0,64,6.4,10,20,0,3,1,8,0.8,10,20,0,4,0,32,3.2,10,20,-140,5,1,10,1,10,20,0,6,0,30,3,10,20,-90,0,0,2,211

The escapement has 30 teeth and rotates gear 0 at one rev per minute.  This can provide a seconds hand.
Gears 0 to 1 have a 7.5:1 ratio.
Gears 2 to 3 have an 8:1 ratio.  The 7.5:1 and 8:1 gears provide a 60:1 ratio between the seconds hand and the minute hand.
The remaining gears provide a 4:1 and a 3:1 ratio between the minute hand and the hour hand.

Steve