Dynamo Advice Needed

[rogersirs]

Hi

I am fairly new to the scene and have a 1936 AAL Tourer. While the car is hibernating for the winter, I am trying to sort a couple of issues, one of which is the ability to charge the battery. The ammeter never shows a positive reading and I have to charge the battery every couple of runs.

So, having checked on the vehicle and getting no sign of Any Dynamo output I have removed the unit to check it over properly. On first look the internals were very oily, so Ah it needs a clean I think! However on stripping down the puzzle expands. I find one of the leads to the brush terminal disconnected (the one which goes to the D terminal), but the screw to which it attaches was tight so obviously it had not come undone. Also I find  a small square nut sitting inside and no screw holding the moveable third brush in place. 

So my initial thoughts are clean up all the oil, polish the commutator, new brushes, attach the cable and replace the screw! 

However, I was puzzled to find two roller bearing inside, one at each end and it turns out my Dynamo is 28-32 CAV DEL unit. A little investigation and I now understand that this unit has internal Winter/Summer Field windings, but I have it wired into a 36 CFR2 control unit with its own internal winter/summer resistor. 

Does anyone have any knowledge of using this early Dynamo on a later vehicle and could the disconnected wire and removed screw be a mod to make it work?

Help!

[Bob Culver]

If you have delved will already have read that essential reading is the Cornwall Club site "A Charging Refresher" and Dorset Club ARR/ARQ diagram by John Cornforth. It is common for the internal resistor to be open circuit, either burned open or intentional, possibly the stray wire. (I suspect the diagram is slightly wrong, the resistance connected to all the field coils in series, not after the first as drawn). Note that on the 4 pole dynamos the main brushes are somewhat unexpectedly at right angles. Care is necessary not to constrict and load the bearings end ways.

[rogersirs]

Bob

Cheers. Yes I read that article and with reference to the DEL it was the phrase:

 “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”  

Made me think the wire was disconnected for a reason, it’s just with that wire disconnected there is no connection between the brush and the output terminal and as you say we don’t know how accurate the drawing is. I will search out the other article you mention and see what it says.

[Bob Culver]

The situaaion with the D and F connected but not externally to the battery must be avoided (except for brief voltage  test of dynamo operation). Best not to join directly on the dynamo in case output lead ever detaches. With the original DEL this condition exists. Persons thinking they were disabling the dynamo possibly accounted for burned out resistors.
There is nothing inherently wrong with the DEL, although some suggest its safe output may be slightly reduced, 8 amps on meter) The armature internal connections are different and testing by comparing adjacent segments does not apply.