# Gravity Escapement Escape wheel RPM

Discussion in 'Clock Construction' started by dandydude, Mar 14, 2018.

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1. ### dandydude Registered User

Nov 30, 2014
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#1
Hello,

I was studying double 3 legged gravity escapements. With a seconds pendulum does it take 6 seconds or 12 for an entire rotation of the escape wheel? I am not able to figure that out...

Dandydude

2. ### Phil Burman Registered User

Mar 8, 2014
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#2
As the pendulum is 1 beat per second and the escape wheel moves every beat and moves 6 times for one revolution it must be 6 seconds per revolution.

Phil

3. ### dandydude Registered User

Nov 30, 2014
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Dear Phil,
Thanks for that...
In a graham dead beat style, each beat moves half a tooth forward right? (30 tooth Escape Wheel + 1 second pendulum = 1 RPM of Escape Wheel)
Why would it be different in gravity escapements? Why would it move 1 tooth per beat and not half tooth?
I have been finding some conflicting information online.

4. ### Phil Burman Registered User

Mar 8, 2014
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#4
With a dead beat escapement each pallet operates on every one of the 30 teeth the escapement moves only half a tooth spacing per beat., whereas each three legged escapement in the double gravity escapement operates only on its corresponding pallet. It's effectively two separate 3 tooth escapements.

Phil

5. ### tok-tokkie Registered User

Nov 25, 2010
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#5
Double 3-legged gravity escape wheel moves 60° each event so with a 1-sec pendulum you need a 10:1 gear reduction to drive a seconds hand.

6. ### Phil Burman Registered User

Mar 8, 2014
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#6
The confusion may be because a single six legged escapement will rotate once every 12 beats whereas a double three legged every 6 beats.

Phil

7. ### dandydude Registered User

Nov 30, 2014
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Thanks for that tok-tokkie...
1:10 wheel would be the fourth wheel... this would end up being larger than the 3rd wheel which is usually a 1:7.5... this is bit inconvenient, don't you think?

Thanks a ton
Dandydude

8. ### dandydude Registered User

Nov 30, 2014
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That makes it so much more clear. Thanks Phil...

regards
Dandydude

9. ### tok-tokkie Registered User

Nov 25, 2010
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#9
I suggest you read my 30-legged gravity escape thread. I give a detailed illustrated description of how a gravity escape works. There is a link to the Trinity College clock site which has an animation of a double 3-legged in action. It also has very thorough mathematical analysis of the dynamics of the escape. 30-Legged Gravity Escape Clock

10. ### dandydude Registered User

Nov 30, 2014
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#10
Dear tok-tokkie,

Thanks & regards
Dandy