Re: Timing data for Synchronome # 2177


Harvey Moseley
 

What are the dynamics when the gravity arm falls?  How should it really work?  1)  how far above the pallet is the roller when it drops?  2) does it drop onto a flat spot so the initial fall does not generate an  amplitude impulse?  3) the amplitude impulse occurs when it rolls into the curved section of the pallet?  Where should that be in the pendulum cycle?
I am thinking that we would want to avoid any impulsive interaction between the initial fall of the gravity arm and the pendulum amplitude, making the clearance between the gravity arm and the top of the pallet as small as possible?  Then all the push comes fairly adiabatically as the roller goes down the ramp.  Is this the right way to think of this?   Also, the shape of the pallet on which the roller works is a possible variable. I never understood the circular-looking profile.  Never seemed right to me.  We should decide what force profile we want and then machine that into the pallet.
As I have mentioned, I have a synchronome I built back in 1969-1970 when I was a 20 year old and played with it quite a lot then.  You  guys are spurring me into setting it up again.  I never had a clock dial with it - I did have a photocell to count cycles though.
Best,
Harvey


On Oct 22, 2019, at 6:35 AM, John Haine <john.haine@...> wrote:

Yes, my rod is actually CF tube.  I suspect that it is no more rigid than invar.  Actually I suspect that the vibration is not the rod bending, but rotating around the CG of the bob against the suspension spring - as Tom pointed out a while back it would be better to impulse through the centre of percussion of the pendulum to avoid this.  I do see a bit of this movement especially when starting up but I don't think it's a big problem, the vibration frequency is well above 0.5 Hz.

I agree that the 'Nome is a very robust and reliable design, a great bit of "intermediate tech".  That's not to say that it can't be improved with some modern techniques though.

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