# pendulum balance wheel vibrations

Discussion in 'Clock Construction' started by croyleje, Dec 21, 2016.

1. ### croyleje Registered User

Jan 13, 2016
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service technician
Lewes. DE
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Hello Everyone,

I have built several clocks from plans and am now working on my first design of my own. I have been doing a lot of reading about train design and have managed to confuse myself more then anything. Most of the books I have been using are old books found free on google books they use the term vibrations a lot. My question is, does a vibration equal one complete swing of the pendulum from one side to the other and back (so it would start on the right and end on the right) or is it from right to left? I have even seen descriptions of one complete pendulum swing being four vibrations (one from center to right, one from right back to center, one from center to left and finally left back to center). Any clarification would be very helpful.

Thank you,
Jason

2. ### tok-tokkie Registered User

Nov 25, 2010
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Cape Town, South Africa
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I am afraid it is used both ways. In Horology a vibration is usually just a single swing of the pendulum - it starts and ends at the same place. In Science they refer to a cycle where the pendulum is back where it started AND moving in the same direction so it passed through the starting point half way through the cycle.
The period of a swing (horology) is Pi*SQRT(length/gravity) or a cycle (science) 2*Pi*SQRT(length/gravity)
The last part of your question would be 2 horological vibrations but 1 science cycle.

3. ### dAz57 Registered User

Dec 7, 2011
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Last edited by a moderator: Dec 31, 2017
You have period, vibration or beat, Hz and ampiltude.

Take a one seconds pendulum, you measure it's time of the swing from it's max swing to max swing, not starting at the resting point,

So we'll call the stopped position when the pendulum is at rest zero (0), the maximum swing in one direction point A, and the maximum swing in the opposite direction point B

So a swing from point A to B is a vibration or beat

a swing from point A to B and back to A is a period

So a seconds pendulum has a period of 2 second, a vibration or beat of 1 second and a Hertz of 0.5Hz

Normally in the trade we write down the beats or vibrations per hour, so a one seconds pendulum has a train of 3600bph(vph)

Ampiltude is the distance of a swing in a single direction, measured from point zero to either point A or B

If you have a balance wheel escapement from a watch or platform that has an 18,000vph train then that is beating 5 times a second or 5 beats per sec or 2.5Hz and it should have a nice healthy ampiltude of 270° or 3/4 of a turn from point zero to A or B

4. ### croyleje Registered User

Jan 13, 2016
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Lewes. DE
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Thank you both gentlemen both your answers helped. Tok-Tokkie that explains why I see both being sited and thank you for the clarification dAz57 I truly appreciate it. It seems the more I think I have learned the less I understand.

Thank you,
Jason