A Tower Clock project

What difference does that make?

Regards Ian.

.

Is that supposed to be a follow-up to my question … or something else in the thread

If the former : How should I know what difference it makes

I was just asking a civil question.

MichaelG.

Thanks John for the thought. It had crossed my mind. The pendulum hangs down behind the frame, so an arm at the top extending upwards past the suspension would be a possibility. But I am struggling to find a source of the math for such a pendulum. My applied math is so far out of date I don't think I could work it out from first principles.

Receipt of a copy of Ivan Law's book on gears (about which I knew very little), hard thinking and some spread sheeting over the last couple of days has produced a possible arrangement. Slightly longer pendulum with finer gears than scale on the great and second wheels and a few more pins in the escape wheel produce a set of figures that beat almost twice as fast, but still revolve the output shaft once per hour while the gear diameters remain fairly close to scale.

Now whether I could actually make a set of M. 0.4 ten pin lantern pinions, whether the required 0.6mm diameter (I think) piano wire/pivot wire would be strong enough for the pins and whether the resulting lantern would have room for an arbor are entirely other questions!!

Thanks again for the encouragement - although it does feel a little like I have stepped through Alice's looking glass and am being sucked further and further into another reality!!

This might help refresh the little grey cells, Peter: **LINK**

https://farside.ph.utexas.edu/teaching/301/lectures/node141.html

It’s a pretty concise introduction to the theory of the Compound Pendulum

MichaelG.

Here's a simple formula that works for light rods and compact weights. Taken from an article I wrote in 2008 for Horological Science News.

Hope this helps.

Thanks Both - I feel more brain ache coming on!

Michael G, casting was done in a cope and drag box the traditional way. PS. The risers (3/4 dia) have been used to make bushes for other projects and hav machined up well with no inclusions!!

.

Thanks again, Bernard … I was just interested because some of my ancestors were involved in Brass casting, and I am aware that such shapes do lend themselves to being cast single-sided, in ‘a mere scrape in the sand’.

MichaelG.

In case anyone is interested!. It has been a bit cold in the workshop for progress on the "other projects", so I have amused myself by developing the design for the church clock model. Rather than the original idea of having the chime triggered twice (rather than the four times of the original), I did some spread sheeting to develop an alternative time train that gives a once per hour minute shaft, and for which the wheels are fairly close to scale - I chose 6mm = 1" as I prefer to work in metric, but the clock is clearly imperial dimensions. So far only the time train is close to a finished design, the chime & strike trains will be closer to the original as the gear ratios can be retained.

The model so far is

Time Train
                         Church Clock Model
Great wheel Teeth 120             150
Rotates Every      3 Hours     3 Hours
Ratchet Teeth         20                 20
1st Pinion Pins       10                   8
2nd Wheel Teeth     90               116
Rotates Every min  15                   9.60
2nd Pinion Pins         8                  8
Escape Wheel Pins 35                35
Rotates Seconds     80                39.7
Pendulum Period secs 2.29         1.13
BPH                       3150             6343
Minute Wheel Teeth 40                 50
Rotates            Once per hour Once per hour
Bevel Gear Teeth    76                   60

Dimensions 1" = 6mm
                              inches          mm       Scale
Great Wheel           11.75           76        1.08
2nd Wheel                8.5             59         1.16
Escape Wheel          5.5             32         0.97
Minute Wheel           4.0              26         1.08
Bevel Gears             7.5              28          0.62
Drum                        6.0              36          1.00
Pendulum Length   51.20          320          1.04

Using MOD 0.5 for the gears, the second wheel is a fair bit (16%) bigger than scale which required the escape arbour to move to one side, at which point it clashed with the minute arbour drive wheel, so the bearing mounts needed lengthening to raise it up to maintain depthing. The output bevel gears also needed to be made a bit smaller to avoid a clash with the second wheel, but otherwise things are fairly close to scale.

The escape wheel teeth on the original are flattened and about 1/8" thick. To scale they look rather fragile at 0.75mm, so I have used 1mm pins and modified the pallet spacings to suit (I hope!). The plan is to make the arbours from silver steel and harden the pivots. All bearings are brass. Several parts (the frame, the escape arbour, bevel wheel bearing supports and the pendulum support are clearly cast iron. They will be fabricated from steel ( silver soldering is a skill I will need to acquire). The winding ratchet also looks to be cast and that together with the similar parts for chime and strike, plus the strike cam have some complex curves that I will need to work out how to make. I might see if I can find a local laser cutting organisation willing to make small one-off parts for a reasonable cost (unless anyone has a cheap desktop laser cutter capable of cutting 4mm steel plate going spare).

As always, comments and suggestions gratefully received.

Edited to correct tabulation of table ( I hope) 

Edited By Peter Cook 6 on 20/01/2022 17:50:07

Edited By Peter Cook 6 on 20/01/2022 17:52:38

That seems to have got very complex!

I have to agree with Roger, keep it simple its still fascinating to watch when finished.

The project has made its first swarf. Having decided on Mod 0.5 for the wheels of the time train, before ordering lots of material, I thought I should experiment and see if I could make a Mod 0.5 8 tooth lantern pinion. 6mm diameter, 4mm width (for a 3mm wheel) and using 0.51mm piano wire (nearest to Mod * 1.05 as per Wilding I could get). Included a cap to cover the end. Currently loose on a dummy arbour.

Worked well. Finish needs work, and the wire for the real ones will need polishing. But a win. Now I need to find out if it will run against a Mod 0.5 wheel.

You should (and perhaps have) realised that one of the advantages of a flat frame is the ability to have adjustable bearing bushes so that engagements can be set on the clock without depthing. The design should take allowance of this so that the clock can be set up from barrel to escapement as you go so that moving one bush doesn't throw three other clearences out.

regards Marin