Material Selection and Dimensions

[devils4ever]

So, I'm getting closer to starting my clock project.

Pricing brass has given me sticker shock. I'm thinking of using Aluminum for the wheels, probably 7075. Issues with using this? Hardness of 353 brass is B66 and 7075 is B87. Thermal expansion difference? For the plates, I'm thinking of using 6061 Aluminum and use Bergeon bushings. Good idea?

Next, I'm trying to determine dimensions for some of the parts. The wheels are in the 3"-4" range, so I'm thinking of using 1/8" thick stock with 1/4" thick pinions. Shafts are 1/4"? Plate thickness?

 

[John MacArthur]

Before you decide on aluminum, check with McMurray Metals in Dallas about brass prices; they are MUCH better than the other "usual suspects". They'll cut just whatever you want. 1-800-658-5688

Johnny

 

[GregS]

I agree with John. Aluminum oxidizes much worse than brass and needs to be anodized to be properly protected. That extra cost alone needs to be considered, though I suppose you could lacquer them.
I may also add that you consider making a mock up out of cardboard circles to get a scale of how big and heavy your movement will be with 3 - 4 inch wheels. I've attached a picture of a wheel from a clock I am making that also has 3.5 inch wheels and I kick myself everyday for starting out with these huge wheels. I'm too far into to go back now. The wheel shown is ~3.5 inches in diameter with an 1/8 inch arbor (no pivots as it will ride on roller bearings). The teeth are module 0.95.

Greg

 

[devils4ever]

Thanks. I'll look into McMurray Metals. Maybe, I can use 260 brass or 360 instead of 353?

 

[Allan Wolff]

Yes, brass is very expensive, as are all other metals. I don't know the exact costs you are facing, but there are other factors to keep in mind besides saving a few dollars on the raw materials.

Aluminum is fine for structural components like back plates and brackets, but it is too soft for wheels and will wear away and deform quickly.

All of your brass round stock will be 360 and that is fine. It looks great and is a dream to machine. Sheet stock will be 260 or 353 brass. Don't use 260. While it may work for the plates, wheels and other parts, 260 is miserable to work with. It cuts more like steel than brass, requires lubricants to keep from sticking to your tooling, and the chips are stringy and sharp.

Going with thinner material may be OK if the clock will be out of sight or in a case. However, if you are making a skeleton clock or something that will be on display, appearance is almost more important than timekeeping. For a display clock, you want something that looks proportionally correct. Thin wheels might be OK but skeleton clock plates are typically 3/16" thick or more. Look at a bunch of photos and you will see what I mean.

When I built my clocks years ago, I remember being shocked at the price of raw materials, but I went ahead and spent the money on the right stuff. I'm glad I did. I no longer remember how much the material cost, I just know the clocks look great and will last forever because I used the right material. Also, consider the amount of time you will have invested in your project. I estimate I had over 1000 hours in each skeleton clock. With that much invested in labor, spending a few hundred dollars more on material is insignificant.
Allan

 

[John MacArthur]

260 will not work very well, it's gummy to machine and doesn't drill well. It is made to be formed or bent, not machined. 360 is what the rods will come in anyway, and try to stick with 353 for plates and wheels. I realize these are more expensive, but you will be happier. If you do go with 260 be sure to get "half hard". The same applies to the steel rod you'll need for arbors and pinions. Use 12L14, it's much easier to machine and being very common, isn't much more expensive than cold-rolled. If you plan on hardening the pinions, use 41L40. You don't say where you are located; are you in Britain or USA?

Johnny

 

[John MacArthur]

Looks like Allan beat me to it!
Johnny

 

[devils4ever]

I'm located in NJ, USA. I'm having trouble even finding 353 brass. 360 is much easier to find and less money.

7075 aluminum is hard and like steel in many aspects. It's not cheap either, but a LOT less than brass. I' don't want to get into anodizing though.

I have a CNC mill which has no problems cutting steel and do it all the time so 260 brass wouldn't pose a problem. My lathe is small, but I cut steel on it all the time, also. I cut 12L14 on it all the time. I thought I needed to harden the pivots so I would need a high carbon steel for that.

One of my usual suppliers is Onlinemetal.com. 353 brass 3/16" thick X 12" X 12" is over $650! McMaster-Carr has 1/4" thick by 12" X 12" 353 brass for $324. Better, but still crazy!

 

[Allan Wolff]

Devils4ever,
You seem to be very much like me. I am so used to finding everything online that I avoid calling vendors or shopping in person. McMurray does not post their pricing online. They told me it was because the prices change almost daily and they want to provide the best prices to their customers. Don't be like me; make the call. I think you will be pleasantly surprised with their prices. Even with shipping and cut charges (they will cut a 12 X 12 piece out of a much larger sheet), McMurray has been substantially cheaper than other sources.
Allan

 

[John MacArthur]

McMurray also doesn't show up on Google searches because they won't submit to the "pay to play" policy. They really have much better prices. For arbors that are not integral with the pinions, drill rod (O1) is fine, for machining hardenable steel for pinions I like 41L40 best.
Johnny

 

[wisty]

Prices look expensive compared to the UK! but have you considered starting with 4" wide 3/16" strip for the wheels rather than a 12" square.
McMaster Carr seem to have 360 brass in that size at about half the price/sq ft of 12" wide sheet.

 

[devils4ever]

Allan, I quickly reviewed your skeleton clock thread and I'm absolutely impressed with your work. Amazing.

I'll have to give McMurray a call when I get closer to finishing my design. I plan on building a prototype (or two) before going for the brass. I especially want to build the escapement since that seems to be the trickiest.

I was planning on going with a Graham deadbeat, but after seeing the pinwheel I might go for that. I like the idea of drilling and adding pins for the escape wheel rather than machining one. I've read that the downside is lubrication of the pinwheel escapement.

How do you size the length of the arms versus the diameter of the escape wheel? Also, most of the books I've seen on the pinwheel escapement show a much shallower angle on the faces.

I thought the shaft (arbors) where made from tool steel and the ends hardened.

I plan on using module 1 gear cutters since that's what I have hence the larger size of the wheels.

 

[Richard Cedar]

Devils4ever,

Let me share some alternative thoughts on the choice of material. I design and construct large skeleton clocks (www.cedarclocks.com); my largest clocks have wheel diameters of over 20". To minimize the power required to turn the escapement wheel, keeping the rotational inertial is crucial, so one wants to choose a low-density material. Because of this, I have been constructing the wheels from walnut wood and have worked through the issues of warping and breaking teeth.

I have recently made a couple of smaller clocks and had an email exchange with Dennis Keeling, who constructs clocks from acrylic plastic. Dennis persuaded me to try using acrylic to make my smaller clocks. I tried and found that it was an excellent material. With the appropriate feeds and speeds, it machines beautifully. You can glue components together to make complex shapes and polish the joints so that they are almost invisible. Acrylic is low-density, comes in a wide variety of colors (permitting interesting design options), and is relatively inexpensive, especially compared to brass.

I am sure that an acrylic wheel clock will wear faster than one made of brass, but by designing the clock to minimize the tooth forces will minimize the wear. I have seen no evidence of wear on my clock and am okay if it does not last for generations. Of course, the aesthetics of an acrylic wheel clock will not be the same as a traditional brass clock, but that is a matter of personal preference.

In some of your earlier posts, you ask about gear cutters and the limited options on the choice of tooth count from your dividing head. However, you also mention that you have a CNC mill. Is there a reason you do not want to cut the wheels on your CNC mill to mitigate the need for a gear cutter? I cut all my wheels on a CNC mill and Dennis Keeling moderates a Facebook community called "Clockmaking using CNC". There was also an article in a recent NAWCC Bulletin on using a CNC mill to make a traditional brass clock.

Richard Cedar.

 

[devils4ever]

Richard,

Your clock looks awesome. Great work!

I think cutting the gears on my CNC mill would require very, very small end mills even for gears in the 3-4" range. I might try that on the escape wheel, but that has larger openings between the teeth.

Do you use acrylic? I've used Acetal before and it machines beautifully and is fairly slippery, but probably too soft for gears.

I'll look for that bulletin.

Thanks!

 

[gvasale]

I'm located in NJ, USA. I'm having trouble even finding 353 brass. 360 is much easier to find and less money.

7075 aluminum is hard and like steel in many aspects. It's not cheap either, but a LOT less than brass. I' don't want to get into anodizing though.

I have a CNC mill which has no problems cutting steel and do it all the time so 260 brass wouldn't pose a problem. My lathe is small, but I cut steel on it all the time, also. I cut 12L14 on it all the time. I thought I needed to harden the pivots so I would need a high carbon steel for that.

One of my usual suppliers is Onlinemetal.com. 353 brass 3/16" thick X 12" X 12" is over $650! McMaster-Carr has 1/4" thick by 12" X 12" 353 brass for $324. Better, but still crazy!

A HUGE "NO" to 12L14. Leaded steels do machine easily, but RUST wicked fast.

 

[Robert Doris]

A HUGE "NO" to 12L14. Leaded steels do machine easily, but RUST wicked fast.

I use W1 water hardening tool steel (drill rod) for arbors and pinions in my clocks with no ill effects. Pinions hardended from cherry red and tempered to straw/brown are very hard, quite tough and can be highly polished. Never had one break, wear out or rust going back to the 1980's

I have used McMurray Metals in Dallas and Lewis Brass and Copper in NY in the past for cost effective brass plate.

As per Richard Cedar's wonderful clock, I will concur that cast acrylic machines beautifully and a pleasure to work with. I have made two clocks using clear cast acrylic plates. It is nice to see the movement components completely unobstructed.

 

[jhe.1973]

Hi Everyone,

Just to support the OP's idea to use aluminum for as many parts as possible here was my attempt (being a cheap pack-rat helps):

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This was all built using shop scraps. The aluminum for the plates was dead soft who knows what with Bregeon bushings and ball bearings. The plates were polished then lacquered in 1979 using clear that I tinted yellow and sprayed with a spray-gun. The movement has been apart countless times so the lacquer is chipping a tiny bit but it is hardly noticeable. The posts and stand-offs for mounting the dial are 'anodized' using Dykem layout dye. The bronze rims for the wheels were cut from a bushing my brother-in-law gave me and were fairly nasty to cut with the method I used. The tooth form is all wrong and I had to hand file each of the 120 teeth per wheel to even get it to run.

Even with all of these weird materials and methods I was amazed to find that it is easy to keep in within one second per day referencing a radio controlled clock that follows the US atomic clock signals (WWVB).

P.S. I almost forgot, the pendulum shaft is an old curtain rod found in the basement of the house we lived in at the time. So, unless I miss my guess, I don't believe it has temperature compensation!

 

[Allan Wolff]

Dykem anodizing... I never thought of that. I bet you can Dykem blue the hands too

 

[jhe.1973]

Yep any port in a storm ....... works for me!

Great to hear from you Alan!

 

[Phil Burman]

This is a bit late but I just read in the book "Woodward on Time" by Philip Woodward that he used aluminium alloy for the wheels, with involute teeth (he was an engineer) together with stainless steel pinions for his famous W5 free pendulum clock. Bottom paragraph on page 312. Doesn't sound right but there it is.

Phil

 

[devils4ever]

UPDATE: I made the pinions out of W1 drill rod, but have not hardened them yet. I decided to go with 353 brass for the wheels. I've cut the teeth on the 96T wheels using a custom 24 hole dividing plate. I still need to cross out (mill the spokes). I'm working on the 90T wheel next.

A few questions:

1. Do I need to use a crutch on the pendulum or can I connect the pendulum directly to the anchor pallet?
2. The wheels are 1/4" thick and the pinions are 3/8" thick. Is 1/8" thick brass appropriate for the front and back plates?
3. Should I use bushings in the plate or just drill directly into it?

Pinions.

96T Wheel mounted on dividing head with pins in place to measure if depth of cut is correct.

 

[John MacArthur]

Devils - 353 brass is a good choice for the wheels. The escape wheel should be thinner than 1/4" to keep its weight/inertia down. The wheel obviously doesn't have much force driving it, and it needs to accelerate pretty quickly. The plates can be as thin as 1/8" thick, but are almost always a little thicker in regulators. I typically use 5/32"; I used to use 3/16". If you go with 1/8" you should probably install bushings at least at the barrel arbor pivots. The escapement almost always transfers power to the pendulum via a crutch. This allows one to remove the movement from whatever case it is in, such as for servicing, without removing the pendulum. You also have to consider the suspension - how you are going to hang the pendulum; the normal type would interfere with attaching it directly to the escapement. There have been exceptions, but I would imagine they are pretty cumbersome to handle. It appears that you are using involute tooth shape; this has been argued endlessly over the years, but with modern materials and cutters should work out fine. the cutters are MUCH cheaper. Looking good so far. Keep posting, we all love to see this stuff.
Johnny

 

[Allan Wolff]

Do I need to use a crutch on the pendulum or can I connect the pendulum directly to the anchor pallet?

A crutch would make assembly and servicing much simpler as Johnny pointed out. I would encourage you to include a mechanism to adjust the beat in your design. While a fixed crutch or attached pendulum is simpler to make, it seems so crude to bend a part, insert shims or tilt the case to put a clock in beat.

 

[devils4ever]

Thanks for replying!

I made a prototype escapement with 1/4" aluminum for the escape wheel and 3/8" 4140 steel for the pallet. I plan on remaking the escape wheel in 353 brass. I guess I'll go with 3/16 for it"? Or, should I go down to 1/8"? Should the pallet be smaller to match? 1/4"?

Okay, I will go ahead with a crutch.

Sounds like 3/16" for the plates will be good. Should this be 353 brass as well?

I'm looking into purchasing a suspension spring. Suggestions on approximate size and vendor would be appreciated.

Yes, I went with involute gears since I had the cutters and the cycloidal ones are $$$. I've read so many pros and cons on this subject that my head hurts!

Anchor pallet

Escape wheel with hub.

 

[John MacArthur]

Devils - My escape wheels are 1/16 th., I would think 1/8 wouldn't be too heavy. The pallets sustain most of the wear in the escapement. That said, the pallets can be any thickness; they don't have the inertial problem. I use Starrett feeler gauge stock .006" or .007 for heavy pendulums. MSC or McMaster. Make it as short as possible. Mine are ~ 1/2" long, and a little less wide. I use 353 for everything I cut from plate. Bigger blocks are cut from stuff I picked up many years ago at Los Alamos Salvage yard, probably 360 from the way it machines. Cost was no object to them.... Nice looking pallets and escape wheel.

What CAD/CAM and machine program are you using?

Johnny

 

[devils4ever]

Wow! That thin? Okay, I'll have to remake it with thinner stock.

I use FreeCAD for CAD/CAM.

 

[devils4ever]

Here's a view of the 96T wheel in FreeCAD.

 

[devils4ever]

I'm looking finalizing my design and I'm looking at the click and clickspring. I can easily make the click, but I'm wondering if I should buy a commercial clickspring. I've been using "Making Clocks" by Stan Bray as my reference and he states in it to make the clickspring out of mild steel and hammering it to work harden it.

Thoughts?

 

[John MacArthur]

Why make it out of mild steel when you can use gauge stock and harden and temper it. They're both hacksaw and file work.
Johnny

 

[devils4ever]

Why make it out of mild steel when you can use gauge stock and harden and temper it. They're both hacksaw and file work.
Johnny

I'm not familiar with gauge stock. I did a quick search and found that it is used for feeler gauges. What thickness would be appropriate? Does it come annealed?

Could I make it out of 4140 or W1 steel and harden and temper it?

 

[John MacArthur]

AKA oil-hardening flat stock MSC #76110105 McMaster 9018K13
Stuff hardens and tempers nicely, and with your CNC it should shape almost perfectly
Johnny

 

[devils4ever]

I'm still trying to finalize my design and I have a few outstanding issues/questions:

1. I'm not sure if anyone follows clickspring on YT, but he used a silk cord instead of a spring suspension which allows adjustment at the top of the pendulum instead of the bottom. Thoughts?

2. I'm not sure how big the arbors/shafts should that hold the hour and minute hands. Thoughts?

3. I'm assuming a tight (but not too tight) fit is needed to allow the hands to be moved to set the clock. So this is needed between the minute hand and the center wheel?

Thanks!

 

[John MacArthur]

Devils - I have watched quite a bit of clickspring, and appreciate his craft. However, thread suspension is not as secure, precise, and accurate as a spring suspension. If you care about accuracy, use a spring.
keep us in the loop,
Johnny

 

[devils4ever]

Johnny,

Thanks for the feedback.

I'm thinking of ordering this assortment since I'm not sure about the size. I'm thinking the A2 size would be appropriate?

 

[John MacArthur]

It will depend on the weight of your pendulum bob. The big one might be appropriate for a heavy bob. I use .006 feeler gauge, about .4" wide, and make the chops. My pendulum bobs these days weigh 11 or 12 lbs.
Johnny