19-07-2020, 02:10 PM
(15-07-2020, 11:46 AM)JonE Wrote: That's helpful, thanks. The 'Charging Refresher' series of wiring diagrams doesn't actually mention the short and long armature differences - how would one tell... and what did they relate to - is one later than the other?
Can I also be thick over the "Most of the internal resistances on CAV DEL dynamos are open circuit" bit? I realise that means the circuit is not activated if its open, but what does that mean in practice vis a vis checking if the original resistance still operates and how you deal with that? I presume that your 7.5 Ohm is brought in to play when the SM switch activates the F-D bridge?
The Charging refresher article says:
"Repairing these windings can be a real pain, which is why (according to Harry Hale, the expert,) many of the DEL types are simply used with the resistor open circuit, or replaced for later machines. Again, there has to be some appropriate modification of the circuit – they might fit mechanically but need some other changes electrically"
I waas uncertain whether Open Circuit meant "not functioning", or whether one needed to detach something.
Jon,
The term "long" and "short" refer to the physical length of the armature, the later dynamos being the long variety. The two can be differentiated by the fact that the short armature DEL has a fabricated distributor end cover, whereas the long armature machine has a one piece cast aluminium end cover. The changeover was December 1929 at around engine number 99900. The drive gear also changed from the extremely fragile bell gear to the solid gear familiar to the later cars.
The term "open circuit" means just that, not connected, no current can flow, disconnected.
On full charge, the dashboard switch places a short circuit (N.B. "short circuit" is the opposite of open circuit and implies that two parts of the wiring are connected together with 0 ohms resistance between them) between F and D. On 1/2 or "summer" charge, this short is removed and that's when the current can flow from D to F, through the internal resistance if it's still operational or through an external resistor if connected between F and D.