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Pendulum enquiry

How to make a driven pendulum

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Plasma23/07/2019 18:44:42
326 forum posts
41 photos

I dont know why but I have a hankering to build a large pendulum mechanism to operate in my home.

What would be the requirements to make and drive a pendulum perhaps 2m long? No clock mechanism or indication equipment at all, just a pendulum, escarpment? And drive system, even using weights as a power source.

Is it something a non clock buff can create?

Regards plasma

Bob Stevenson23/07/2019 18:52:21
285 forum posts
6 photos

.....So it ill have a pendulum, an escapement and weights to drive it...so it will be a,...a,.....well actually it's a clock! sorry about that!

............And yes, a "non clock buff" can create a very nice clock with some thought and careful work,...try looking up John Wildings books of designs

old mart23/07/2019 19:45:01
323 forum posts
26 photos

Electromagnets switched by some sort of proximity indicator all set near to the pivot point.

Brian Oldford23/07/2019 20:27:30
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533 forum posts
4 photos
Posted by old mart on 23/07/2019 19:45:01:

Electromagnets switched by some sort of proximity indicator all set near to the pivot point.

These had a mechanism that detected when the pendulum's travel fell below a certain range.

**LINK**

John Haine23/07/2019 20:32:09
2577 forum posts
133 photos

See...

Minimag

**LINK**

**LINK**

**LINK**

Take your pick.

Plasma23/07/2019 21:47:02
326 forum posts
41 photos

The electromagnets look interesting but I'm looking to make a more mechanical set up, kind of like a beating heart of the house. I know it sounds daft but I think it would be an interesting project.

I'll have a look at the wielding designs and see what is within my limited engineering skills.

Many thanks for your replies thus far.

Plasma

John Olsen24/07/2019 00:42:57
977 forum posts
86 photos
1 articles

What about a Foucault pendulum? That is the one that changes its plane as the earth rotates. Well, strictly the plane remains the same while the earth rotates under it, so after 24 hours it is back to the plane where it started. The pivot at the top must somehow allow for that, and I am not sure how the driving arrangements work. Quite an interesting device while not actually a clock.

John

Don Cox24/07/2019 08:01:47
35 forum posts

I maintained a number of small/medium telephone exchanges until the digital revolution swept away all of the interesting stuff back in the '80s. Some had clocks 36, as mentioned in the link by Brian Oldford above, which provided timing to detect faults on the electro-mechanical equipment and a host of other functions. The stepper wheels at the top of the clock gave 1,6 and 30 second pulses (from memory) and the latter were used to drive slave clocks within the larger Post Office buildings and exchanges.

The basic principle used a Hipp contact to energise an electro magnet to restore the pendulum swing when it got below a pre-determined point, I seem to remember this happened every 6 swings. I inherited the task of changing the complete clock when I took over one of my rural exchanges, a bit like trying to nail a coffin to a wall, it took quite a while just to get the pendulum to hang directly over the pointer fitted at the bottom of the cabinet. After that I gave it a daily tweak to get the swing right, it took about 3 weeks to completely settle down. One of my ex colleagues has one working in his workshop.

Michael Gilligan24/07/2019 08:16:45
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13573 forum posts
586 photos
Posted by Plasma on 23/07/2019 18:44:42:

I dont know why but I have a hankering to build a large pendulum mechanism to operate in my home.

What would be the requirements to make and drive a pendulum perhaps 2m long? No clock mechanism or indication equipment at all, just a pendulum, escarpment? And drive system, even using weights as a power source.

Is it something a non clock buff can create?

Regards plasma

.

Returning to your original text [and noting your subsequent clarification]

YES ... I am sure that a 'non clock buff'' could create a decorative item such as that ^^^

The only significant detail that you have omitted is the required angle of swing:

My guess is that you will, for visual effect, want at least +/- 3°

... but only you will know what looks right in your situation.

The reason that this is significant is that it will inform your choice of a suitable mechanical escapement mechanism. I suggest that you experiment with a plunb-line, to get some idea of what angle you find appealing.

MichaelG.

roy entwistle24/07/2019 08:26:26
1005 forum posts

Have a look at Wildings version of Galileo's escapement. Whether it would cope with a two metre long pendulum I'm not sure

Roy

Martin Kyte24/07/2019 10:02:10
1463 forum posts
24 photos

You could consider the Hipp Toggle clock design and not bother building the clock part. Simply, the pendulum has a free swinging 'toggle' which when the amplitude is suffucient passes back and forward over a notch mounter on a spring suspension. When the ampitude falls the toggle fails to clear the notch and on it's reverse swing forces the notch down and closes a contact. The contact activates a solonoid which impulses the pendulum. No wheels, simple mechanics, and a small amount of wiring.

The schematic on the top of this page shows the arrangement.

**LINK**

regards Martin

Michael Gilligan24/07/2019 10:32:04
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13573 forum posts
586 photos
Posted by Plasma on 23/07/2019 21:47:02:

The electromagnets look interesting but I'm looking to make a more mechanical set up, kind of like a beating heart of the house. I know it sounds daft but I think it would be an interesting project.

.

Martin, for info. ... That ^^^ was the 'subsequent clarification' to which I referred

Although the Hipp toggle has an interesting mechanical device at lts heart, I doubt it would qualify as a 'more mechanical set up' [but, of course, I may be wrong]

MichaelG.

Michael Gilligan24/07/2019 10:43:26
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13573 forum posts
586 photos
Posted by roy entwistle on 24/07/2019 08:26:26:

Have a look at Wildings version of Galileo's escapement. Whether it would cope with a two metre long pendulum I'm not sure

.

Good call, Roy

Whether it would suit a two metre pendulum is really why I asked plasma to determine what he perceives as a visually appealing swing.

As you will see from the contemporary illustration **LINK** the swing angle was large.

Re. **LINK**

http://www.cs.rhul.ac.uk/~adrian/timekeeping/galileo/

MichaelG.

Plasma24/07/2019 12:37:40
326 forum posts
41 photos

Some really good suggestions and thoughts here. It's certainly a very interesting project.

I do intend to simply have a long swinging pendulum as a decorative feature. I dont want to go down the route of time indicating.

The pin wheel escapement looks like a very possible method of making a pendulum swing without the need to cut gears etc.

I need to find a set of plans or guidance on making a weight driven drive train and calculate the length of pendulum etc.

Regards plasma

Michael Gilligan24/07/2019 12:46:03
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13573 forum posts
586 photos
Posted by Plasma on 24/07/2019 12:37:40:

... I need to find a set of plans or guidance on making a weight driven drive train and calculate the length of pendulum etc.

.

Have a look at the Huygens 'endlless chain' [or rope, or maybe toothed belt for the modernists] arrangement ... it would save you a lot of heavy engineering for the sake of an occasional pull.

MichaelG.

Bazyle24/07/2019 12:52:11
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4656 forum posts
185 photos

I have a very good book that might be by Laurie Penman. Only 1/4 in thick and green cover. Can't see anything like it on google at the moment so will check this evening if nobody else knows what I'm talking about.

John Haine24/07/2019 13:43:17
2577 forum posts
133 photos

You could over-complicate this. You said you wanted a 2 metre long pendulum - that will make one complete swing every 2.82 s assuming that the bob is heavy compared to the rod. Rule of thumb: a 1 metre pendulum has a period of 2 seconds (clockmakers call it a seconds pendulum because it makes a swing, L-R or R-L, once per second). The period scales as the square root of the length, and is independent of the bob mass (or weight).

The pin wheel is just one part of the escapement, several types can use a pinwheel. As important are the pallets, and these will need to be compatible with the swing you want. Clocks usually have quite small swings, but you might want something quite large for decorative effect. As Michael suggests, several types of escapement don't work well with larger swings.

You might look at a design by John Wilding for a weight driven egg timer - this is aimed at beginners and has a rather simple escapement. There was a series describing its construction in either HJ or Model Engineer I think, maybe Michael you know?

Michael Gilligan24/07/2019 14:02:48
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13573 forum posts
586 photos
Posted by John Haine on 24/07/2019 13:43:17:

... You might look at a design by John Wilding for a weight driven egg timer - this is aimed at beginners and has a rather simple escapement. There was a series describing its construction in either HJ or Model Engineer I think, maybe Michael you know?

.

I've done a quick search on the BHI archive, for 'wilding egg timer' but found nothing, John ... so I suspect it may have been in Model Engineer.

There is some detail here: **LINK**

http://www.clockmaking-brass.co.uk/egg%20timer.html

But given that JW sells his series in book form, I wasn't surprised to see no reference to the magazine.

MichaelG.

.

See also: https://www.craftsmanshipmuseum.com/Wilding.htm

Edited By Michael Gilligan on 24/07/2019 14:05:04

roy entwistle24/07/2019 16:20:48
1005 forum posts

John I think that Wilding's egg timer has a folio escapement not a pendulum

Roy

Michael Gilligan24/07/2019 17:12:16
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13573 forum posts
586 photos
Posted by roy entwistle on 24/07/2019 16:20:48:

John I think that Wilding's egg timer has a folio escapement not a pendulum

.

Roy & John

I am not familiar with it, but [quoted directly, it appears] ...

The escapement is "MacDowell's Single Pin"

**LINK**

https://www.bonhams.com/auctions/18836/lot/263/

MichaelG.

.

Edit: Which is very odd, considering that the Single Pin escapement is illustrated here:

http://elgintime.blogspot.com/2016/04/single-pin-escapement.html

Edited By Michael Gilligan on 24/07/2019 17:22:21

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