Chassis as part of the circuit


Brian Cracknell
 

We have previously discussed this on an earlier thread. Most synchronomes seem to use the chassis for completing the circuit from the armature to the coils via a terminal below and slightly to the right of the coils but others do not and instead the wire from the armature goes directly to the bottom coil and there is no evidence of a hole for the terminal in the chassis which suggests they are as they left the factory. Mine is serial no 1483 and fits this pattern and another one in the 1200s is on ebay at present with the same arrangement with this particular wire looking very original. However other clocks, both earlier and later, use the chassis terminal and indeed the later ones seem to have standardised on using the chassis.
So the question is, what led to the different designs and why are they intermingled chronologically? My theory is that the earlier chassis castings were unpredictable in terms of conductivity and some maybe had cracks in them which prevented reliable conducting. Those examples would have the direct wire connection to bypass the chassis. But then the other obvious question is - why even use the chassis in the first place and what is the benefit? These are all standard clocks without any additional functions on them by the way.


John Hubert
 

One point too bear in mind is that the chassis is the junction between the ’switch’ and the solenoids.  If it is required to access the switch independently, then a connection is needed here.  Some clocks have a third terminal to facilitate this.  It was used when the master was used with a ’Synchronome’ distribution board.

John

On 17 Apr 2021, at 16:23, Brian Cracknell <brcracknell@...> wrote:

We have previously discussed this on an earlier thread. Most synchronomes seem to use the chassis for completing the circuit from the armature to the coils via a terminal below and slightly to the right of the coils but others do not and instead the wire from the armature goes directly to the bottom coil and there is no evidence of a hole for the terminal in the chassis which suggests they are as they left the factory. Mine is serial no 1483 and fits this pattern and another one in the 1200s is on ebay at present with the same arrangement with this particular wire looking very original. However other clocks, both earlier and later, use the chassis terminal and indeed the later ones seem to have standardised on using the chassis.
So the question is, what led to the different designs and why are they intermingled chronologically? My theory is that the earlier chassis castings were unpredictable in terms of conductivity and some maybe had cracks in them which prevented reliable conducting. Those examples would have the direct wire connection to bypass the chassis. But then the other obvious question is - why even use the chassis in the first place and what is the benefit? These are all standard clocks without any additional functions on them by the way.