# Weight of an pendulum bob.

Discussion in 'Clock Construction' started by dandydude, Jun 9, 2015.

1. ### dandydude Registered User

Nov 30, 2014
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#1
Hello,

What is the weight of the pendulum bob of a vienna regulator? Does a heavier bob makes the pendulum swing in a wider arc?
I need a slightly wider arc as the scape wheel tooth lands a little too close to the impulse face of the palet.

Thanks
Dilip

2. ### Randy Beckett Registered User NAWCC Member

May 23, 2012
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#2
A lighter bob will swing in a larger arc than a heavy one, but this is just because the lighter one is pushed farther by the same amount of impulse strength of the movement. However, this added swing is all overswing from excess power. The escape wheel tooth will land at the same place on the pallet, whether the bob is heavy or light. The geometry of the anchor must be changed to make the escape wheel tooth land at a different place.

The deadbeat is most efficient when the escape wheel tooth lands as close to the edge of the impulse face as possible, without landing on it. And the heaviest bob that the clock will swing is the most stable, and therefore most accurate.

I don't have a Vienna bob out of the case to weigh right now, but going from memory, I would say the bob weighs a pound, or less. The viennas small swing comes from a combination of the impulse faces being ground flatter than most, usually around 1.5 degrees, and very little excess power, which matches the pendulums weight well, resulting in a small, but stable pendulum action.

3. ### dandydude Registered User

Nov 30, 2014
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#3
Hello Randy,

The impulse angle and the geometry i have chosen seems quite close to what you have mentioned. I have 1.5 deg impulse angle. The palets spans 10.5 Teeth. The swing iam getting is around 4 degrees. However iam not sure if the scape wheel is touching the impulse face or not. It doesnt seem like it because there is no visible recoil. I wanted to play a little safe and increase the swing.

I will try a 0.5Kg bob as you have mentioned.

Thanks
Dilip

4. ### Tinker Dwight Registered User

Oct 11, 2010
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#4
A dead beat should have no recoil.
Tinker Dwight