A Mini Tower Clock

[cnr6400]

 

[bent]

Wow, go on vacation for a week, and zap!  A whole new project, 6 pages in already!  Had to scrounge, but found some more popcorn...

[Kim]

Those upright frame pieces look great, Chris!  That cove around the edge is a nice touch.  And the adjustment will be great when adjusting the gears.  You've thought this out nicely.

Kim

[crueby]

Thanks guys!

[Roger B]

As Bent says you look away for a couple of days and there's a whole new project well underway       

I do like all the elegant details on the structure   

[crueby]

As Bent says you look away for a couple of days and there's a whole new project well underway 

I do like all the elegant details on the structure 

Thanks Roger!  Its the Penn & Teller Clock - Poof! Its there!   

[crueby]

Each of the gear holder plates has a main shaft at the same height, for the large gears that will all mesh together. So, next I laid out and drilled/reamed the holes for the pivot bearings (pivot being what clockmakers call the shafts that the gears are on).

Here are all of them after drilling. The tall one on the left has a smaller hole, that is the point where the pivot shafts step down from 1/4" to 3/16" diameter.

Then turned up a set of bearing bronze bearings to fit all the holes.

With the holders in place on the frame, I noticed that the short one looks a bit like a Minnion with a beard...   

So, at this point its time to switch over to making the twirling herd of gears! All will be Module 1.0, and range from 15 to 90 teeth. Those who read along on my Worthington Pump thread will know that recently I had picked up a Carbide3D CNC machine to do decorative plate work for myself and the logging museum. I decided to experiment a bit with it, and over the last couple weeks wound up making blanks for all the larger gears on it - great way to turn out the tapered/beaded spokes.

The main reason I started in on the blanks with the CNC was for the gears that attach to the off-the-shelf spring drums that I had purchased years ago. They have an outer gear on them, but its the wrong tooth count for this clock, and also has cycloidal teeth of a size I dont have cutters for. Originally I was thinking that I'd make up some sort of clamping ring  to attach the new gear, or drill/tap into the existing gears. With the CNC, I was able to lay out and cut a recess in the new gear blanks with little posts to engage in the cyclodal teeth:

Now I just need to put in a couple of small screws to hold them together, the little posts will take the load of the spring and gear:

Once I had that set cut (did initial testing with plexiglass sheet to avoid wasting brass, glad I did since it took a couple tries!) I decided to go ahead and make blanks for the rest of the spoked gears. All of them are cut from some C353 Engravers Brass that I bought years ago when first designing this clock. I could just as easily have cut them as I usually do, on the rotary table on the manual mill, but this was an interesting experiment. Since this CNC machine is meant for wood/plastic and light metal cutting, with 1/8" shank mills, it takes a lot longer to cut thicker brass than my normal mill - many more passes needed. That meant that using the CNC probably took more time overall than it would have taken to do them manually, though the accuracy and detail was better this way.

Another experiment was to see how well it could cut bevel gears for the sets needed to take the minute shaft up to the tower dial. It took a LOT of experimenting with the software to get it to do a good set in a reasonable time, was a great learning project to get more familiar with the CNC software. Here is what I wound up with:

They mesh quite well, and are a proper tapered bevel gear tooth form rather than the straight-line approximation possible on a manual mill and rotary table. I did have to increase to Module 2.0 to get the teeth/valleys large enough for a 1/16" ball end mill. A smaller module could have worked with a 1/32" ball end cutter, but the flute lengths on those are quite short, and they are a lot more delicate for deep cuts in brass.

So, next time I'll start in on making gears! Going to start with the 15 and 20 tooth pinion gears out of round brass bar stock, then move on to the larger gears from these blanks.
 

[Dave Otto]

Nice work on the gears Chris!
Did you model the bevel gears?

Dave

[crueby]

Nice work on the gears Chris!
Did you model the bevel gears?

Dave

Well, sorta!  Fusion 360 has several plugins that let you create all sorts of gears - spur, bevel, rack, helical, worm, etc. I used one of those to create the 3D model of the bevel gears, exported that as an STL file, and brought that into the CNC machines app to turn into the gcode.

[Dave Otto]

Ok now I have to ask why STL? That format is great for 3d printing but not really much so for machining.

Dave

[Kim]

Wow! That's a lot of gear blanks you've made there!  That Carbide CNC has really sped up your production here!  You've only been working on you're clock build for a week or so, and you've already lapped me!  And I started almost a year ago!  You're incredible, Chris!

I love the recess you designed to accept the built-in gears on the spring drums. That is pretty clever!

Kim

[crueby]

Ok now I have to ask why STL? That format is great for 3d printing but not really much so for machining.

Dave

Only because that particular app won't import a Step file!  I normally use step files even for printing, but had no choice here. I told Fusion to create the stl file with the highest resolution/detail settings.

[Dave Otto]

Ok now I have to ask why STL? That format is great for 3d printing but not really much so for machining.

Dave

Only because that particular app won't import a Step file!  I normally use step files even for printing, but had no choice here. I told Fusion to create the stl file with the highest resolution/detail settings.

 

[crueby]

Wow! That's a lot of gear blanks you've made there!  That Carbide CNC has really sped up your production here!  You've only been working on you're clock build for a week or so, and you've already lapped me!  And I started almost a year ago!  You're incredible, Chris!

I love the recess you designed to accept the built-in gears on the spring drums. That is pretty clever!

Kim

Thanks Kim!
It helps a lot that this tower clock is no way NEAR as ornate as your clock, and has a much simpler mechanism. I also am using off the shelf spring drums, which saved a lot of time. The CNC'ing of the spokes has saved a lot of hours in the shop too - could start each one up and go do something else while it was nibbling away. Very productive, but no where near as fun as the manual machining is. My shop elves want nothing to do with it. Until they find plans for a miniature Ferrari, anyway!   

[cnr6400]