Member postings for Sam Stones

Tell yah wot ... split three times ... it's taken me twenty-five minutes to get this b******y graph into the thread.

Cobbled in Excel, it went into MS Word where I prefer to edit, and then into Photoshop, before becoming a .jpg file and palatable for this forum.

Now, if you haven't lost interest, you'll have to go back to the text on the previous page. EDIT Now on same page,( Jason)

Sam

Edited By Sam Stones on 20/02/2020 01:23:49

Edited By JasonB on 20/02/2020 08:01:49

... continued

My back-step is in regards to velocity ratio. I had become rather tired of attending to all the manual (CAD) iterations and abandoned the exercise when I got around to messing with lantern pinions.

In that case, I retained the number of teeth, the lantern pinion having 8 (eight) pins (leaves) meshing with the John Wilding’s 290 tooth large wheel. The teeth of the latter being of conventionally accepted cycloidal design.

Consequently, I can only show what was happening where Mr Wilding’s pinion was cycloidal not a round pin.

The graph shows that the velocity ratio (theoretically 290/8 = 36.25:1), gradually increases to almost 40:1 as a single (large wheel) tooth makes its transition. Then, as the ratio gradually decreases, surprise, surprise, the ration drops (from 38.77:1 to almost 36.25:1) as the next pair of teeth/pins meet.

I'm obliged to split this thread a second time ...

Continued ...

Before moving on to the now, quite clearly, ancient trunnion concept, it seems appropriate to reiterate a (perhaps) minor issue. This cropped up towards the middle or final exercise of meshing (read messing) with cycloidal clock teeth in a CAD simulation. With an appropriate warning, the extent of my verbosity can be unearthed here …

Would you mesh with this? Some thoughts on cycloidal clock teeth

**LINK**

Meshing with Lantern pinions - Part A Another slice of CAD, and how cycloidal clock teeth might mesh.

**LINK**

Meshing with lantern pinions - Part B Due to my zealous output, I have been 'advised' to split the original thread.

**LINK**

continued ...

Back shortly,

Sam

I agree Phil.

Some sort of torque/friction relationship?

I’m beginning to think in addition, that even the tiniest amount of lubricant needed for each end of the pins (even minimal), might eventually migrate onto the wheel teeth.

Are there dry (or non-migratory) lubricants suitable for clocks?

Sam

That’s typical of those old blokes, John.

Leaving us nothing to get our teeth into.

Ifoggy - Judging from your excellent work, I'd reckon making one would be a cinch for you.

Sam

There are four lantern pinions in my skeleton clock. The pins were a press fit of steel into brass, and unlikely to work loose.

Although it’s highly unlikely I’ll make any for reasons I’ve mentioned on previous occasions, I’ve pondered about the benefits of trunnion-style pins as shown in this illustration.

The pins could roll over wheel teeth instead of sliding with the obvious benefits and disadvantages …e.g. assembly of the pinion, lubricant spreading to the wheels, etc.

Any thoughts?

Sam

That's a nice piece of kit, Michael.

Tinkerers [whether practical or armchair] might find this helpful: **LINK**

http://www.atmosman.com/clockaid.htm#Calculate%20Pendulum%20Length.

Thank you.

Sam

Does this mean he could have used a non-integer ratio and then run them in the opposite way to get back nearer to the centre?

Guilty as charged NDIY.

I gave it even less thought, other than it might look better

Sam

Bazyle, I think you may have cracked it!

Here’s what happened in a similar vein when I was making the wheels of Mr Stevens’ clock.

My second hand ML7, bought in about ’65, came with a dividing head and three indexing plates.

The design for both the great and the maintaining had 96 teeth. I set up the 40:1 homemade dividing attachment selecting the appropriately drilled index plate. As with the other gears, I used a single-toothed fly cutter made from hardened silver steel. All seemed to be going well until I decided to check that the result was correct by dropping into the first groove I had cut.

To my dismay, that didn’t happen.

Instead, the first tooth began to disappear as the cutter traversed the edge of the wheel. It was too late to do anything but start all over, but not until I had discovered the source of my error. Either I had miss counted the number of holes during indexing, or I had made a mistake in the arithmetic. Then I discovered that I didn’t have the correct number of holes in the index plate either, so I ended up machining a new wheel with 94 teeth.

It was fortunate too, that `give or take a couple’, the number of teeth on the great wheel is not critical in the actual operation of the clock providing that the depth of engagement is taken into consideration. They simply transmit power to the gear train. The only real damage was to my ego.

It is now clear (if you know what you are doing), that the rest of the ‘going train’ wheels don’t have to conform exactly to the number of teeth specified.

Thanks Bazyle!

Thanks for the CPR tip Duncan.

When I was blowing clarinet (badly) in the RAF Auxiliary Band I recall the Cameron Highlanders had to march at about 180bpm. Oh to be so fit now!

Edited By Sam Stones on 31/01/2020 23:42:38

Thanks for the explanation Dave.

Despite having used or had access to word processors since the 70’s, I never knew that.

Several times during the course of my ten years of M.E. forum ‘threading’, without realising why, I’ve lost text or found myself logged out.

I know I’m not the only one who has experienced this frustration after spending considerable time composing.

Unless I have only a remark or two, I compose in MS Word. Then, for no reason that I can recall, I switch to 12pt Times New Roman. All this while avoiding being logged into the forum editor.

This will be a good test.

Sam

It appears to have worked!!!

Many more thanks Dave

This thread has invited a useful selection of entertaining comment. I trust others have been similarly amused. Thanks Michael for your watchful eye on detail, and your attention to the motion ratio aspect Bazyle.

On that score, it’s possible that he thought the design less cluttered when Mr Stevens was considering the motion’s 12:1 ratio. Instead, and with minimal stress to contend with (thanks for your input there John), he used a wheel with 72 teeth meshing with a 6-tooth pinion, the only solid pinion in the clock. However, this choice shoved the smallest of the pinions over to the side, thus requiring a 1:1 pair of wheels to bring the movement back to centre.

Dave’s chosen description of a clock and its variants while delving into the depths of atomic clocks and GPS was quite unexpected. Thanks for that Dave.

We’ll probably never know whether Mr Stevens started with a known (oscillator) source of timing, e.g. a variant of a platform escapement, or the alternative … a fixed stack of crossed out wheels and lantern pinions, each identified according to traditional terminology.

If the former, then I would imagine (as Neil suggests), he may have experimented with varying sizes of balance wheel or, as is quite feasible, calculated variants of the wheel’s 2^nd moment of area. In the original article, brass was the material specified for the balance wheel. Whereas, having read somewhere (Gazeley’s book, perhaps) I digressed making the rim bimetallic (brass on steel). As I recall, the suggestion was 2/3 brass fused onto 1/3 steel. By the time I was into about the fifth attempt, having produced one without clearly visible blowholes in the brass, it was nearer 45/55.

Alongside this, he may instead have chosen to calculate the section properties of the wire, in particular the MI (moment of inertia). Classified in Wikipedia as a chronometer helix … **LINK**, the spring was supposed to be of flat section wire, giving the spring substantially greater stiffness in the vertical direction. Ideally, it would appear to ‘breath’, whereas my switch to round wire stood little chance. Wobble would be a better description.

In hindsight, it appears to matter little if the beat is 0.89266667 secs or 1.00000000 sec so long as we have the time (to wonder).

Sam

PS Have you tried locating a cicada (or a cricket) guided only by the sound they make?

Edited By Sam Stones on 30/01/2020 23:32:10

Inexplicably overstepping the thread character limit, I was obliged to split my last offering.

In answer to your suggestion John H, that … the designer might have started with the balance and designed the train to suit?... this did pass through my mind on occasions. In Part 1 of the five-part Model Engineer article he abandons the idea of using platform escapements as looking like an afterthought rather than an integral part of the design.

Mr Stevens appears to have based his escapement design along lines similar to already established principles of escapement. On Page 268 in the third edition of Model Engineer (17 March 1972. Vol 138, issue 3437), he refers to methods in the late W.J.Gazeley’s book …“Watch and Clock Making and Repairing”.

Whether he developed his own set of balance wheel and balance spring details is unclear. I imagine he would have to. He certainly chose to use flat-section spring wire for the balance spring, whereas I switched to round-section wire, driving myself into a gloomy backwater and many failed attempts at producing a suitable (just passable) balance spring.

In contrast, the (bimetallic) balance wheel design provides timing screws around its periphery.

Despite the bimetallic facility however, I have never tried to adjust the beat for variations in temperature. There were other imperfections that I wasn’t willing to fix; for example, the fusee/main spring calibration, versus the sensitivity to power variations of the English Lever Escapement.

More to come,

Sam

Edited By Sam Stones on 29/01/2020 23:27:58

Continued ...

Re your second response NDIY

As long as the prime number falls within the scope of the available equipment, the idea of using prime numbers is valid. It seems there are few limits when stepper motors are involved.

I’m reminded in your third paragraph (and also your third posting) of what was (once) referred to as a hunting tooth, i.e. an extra tooth that lessened wear. Personally, I have no hard evidence as to whether this method is used.

How odd that I was reading about cicadas, and how two species have evolved. Spending many years of their life underground, they emerge from the ground after a specific period. One species, after thirteen years, and another after seventeen … both, as you can see are prime numbers. This, it would seem, reduces the propensity for their predators to match their emergence.

Sam

NDIY – I enjoyed your replies, so here are my thoughts.

Q. Pleasing to his ear? Perhaps it was. Maybe he didn’t have a preference for the pace of a military beat 120bpm (shades of square-bashing). Personally, I enjoy a good brass or military band.

The ratios the designer selected were 8.4:1, 8:1, and 4:1. The calculated beat (per ‘scape wheel tooth) is 0.892666(recurring) seconds. Whatever reason crossed my mind, I resisted the temptation to quote #1 followed by a string of zeros.

Unintentionally, the three ratios emerging from my choice of wheel teeth were …

8:1, 7.777778:1, and 3.857143:1. Not bad for little effort

Q. Do ALL other clock designs beat at 1.0s?

My guesses …, in not knowing much about clocks would be …

Antique clocks? … not many … apart from longcase (pendulums close to 1 metre).

Electric clocks? … Hummm? … locked into mains frequency at 50 or 60cps.

Quartz clocks? … most of them that I’ve heard ticking ... [sourced from a 2^{^15} crystal.]

I agree that none of it (i.e. the ratios) really matters other than that the clock keeps accurate time which, as I found out while building and setting up the clock, is another story altogether.

I chose to refrain from ‘messing’ with the pinion count. Other than a 6-leaf pinion onto a 72 tooth (motion work) wheel, the drive train for the Stevens clock uses lantern pinions.

It seems I've overrun the number of characters ... I'll be back.

What a wealth of responses and information. Where do I start?

I think it might be easier (for me at least), to address some of these in separate postings.

I'll be back!

Sam

As a one-clock ‘expert’, I have often wondered why the late Mr John Stevens, in designing his skeleton clock with English lever escapement, chose wheels and pinions that produced a beat of 0.893 seconds instead of a very handy 1.0 beat per second.

In a simple spreadsheet for determining the ratios of the existing wheels and pinions while leaving the number of pinion teeth alone, I tested the feasibility.

With little more than intuition I changed three of the wheels from 84, 72, and 56 teeth down to 80, 70, and 54. I was amazed that it took so little effort.

Apart from shifting the arbor centres, slightly increasing the mass of the balance wheel, and/or using a slightly ‘softer’ balance spring, I can see no other obstacle.

Unless I’m off the beam for some reason I could (just for fun) make new wheels and even grab parts from my CAD file.

Any thoughts?

Sam

Edited By Sam Stones on 28/01/2020 02:45:45

Having become what some describe as an armchair engineer, I found this ...

**LINK**

If you have plenty of spare time (which I appear to have), the three parts make a nice change.

Sam

PS - Which category does it fit?

Hello Tony,

In case you missed it, I sent you a PM.

Regards,

Sam

Bazyle, I resemble that remark

If only Buchanan were in Melbourne Bob, I'd be booking an appointment with them and taking an Uber ride up there pronto.

Chelmsford, NSW is just a road too far for this old bugger

Sam