Lucas CFR2 developments

[JonE]

The Morris website seems to be best review for CFR2 and PLC2 operation, but several other websites refer to the dual resistance offered by F1 and F2 on other cars. http://www.ppowers.com/lucas_plc.htm

I've been sitting looking at John Cornforth's wiring diagram and the former, and I'm not actually sure what is the level of adjustabilty that Austin   got to by the end of 1938. Was/is the CFR2 used with 3 options on charge level (off, half, full) or did it ever offer 4 as seems to be possible with the terminals on offer?

I'm presuming the linkage of F1 to F2 on the PLC2 confers that it is only 3. But I'm not quite sure!

[Colin Morgan]

Hi

I am not aware of any changes to the electrical set up towards the end of production - and looking at John Cornforth's excellent diagram covering 1934-39, it seems to conform this view - the connections within the switch are shown for each for the four positions.

Colin

[JonE]

ok, perhaps it's me. I don't follow the diagram in respect of F1 and F2 on the CFR2 bit, as F1 isnt used.
Is it using both resistances separately at different times and if so, can someone just point out how it does it in layperson's terminology..

[Bob Culver]

Some makes did use both resistors to give three stages of charge; lights on, winter, summer but not utilsied on the Seven. An additonal lead was extended to the rotary switch. On the rotary on Sevens I think the two F terminalsif provided are often connected internally, and I am not sure if all junction boxes have two F termnals provided.

By also switching the f lead from the dynamo some can periodiaclly switch the dynamo off on 300 mile trips !(all in daylight!)

John's diag is very ueful and saves having to work out and draw oneself. Curiously Austins did not see fit to publish one.

[Colin Morgan]

Okay - it is not you - when I come to look at the set-up for ARQ and ARR Rubies, it doesn't appear to use the full capability of the Lucas PLC and CFR2 combination.

There is information on the use of the CFR2 and PLC switch in the Vintage Alvis Manual.  This shows a CFR2 cut-out fully wired up with an extra wire that is not on the Seven diagram that goes from F1 on the switch to F1 on the CFR2 cut-out - and there is no direct connection shown between F1 and F2 as on the Austin 7 diagrams, both official Austin and John Cornforth's.

'ALVIS' SET-UP

The workings of a FULLY WIRED up CFR2 are explained in the Alvis manual for the four positions as follows:

Summer or Half Charge Position

The resistances R1 and R2 are in series with the dynamo field to limit the charging rate.  (D connects through the resistances to F2, nothing else is connected inside the switch.)

Winter Charge Position

R2 is shorted out by the contacts bridging between terminals D and F1 in the switch.  (This reduces the resistance in the field circuit so increases dynamo output from the previous setting.)

Side and Tail

Moving the switch again does not affect the charging circuit, but connects the side and tail lights the battery via terminal A.  (Terminal A is connected directly back to the battery, and back through to the dynamo via the electromagnetic switch in the cut-out.)

Head

In this position both R1 and R2 are shorted out by the switch bridging between terminals D and F2.  This gives maximum field current and output.  In this position the field fuse is no longer in circuit.  

So that is the full set-up for a CFR2 switch and PLC switch.  It offers three levels of charging using R1+R2, R1 only, and no extra resistances in the field coil circuit respectively.  (The charging rate is the same for Winter charge and Winter charge with side and tail lights on.)

AUSTIN RUBY SET-UP

However, the Austin set-up is simpler.  There is only a low charging rate on Summer/Half/Low and a single higher charging rate for the other three switch positions - namely, 'Winter/High', 'Side/Tail' and 'Head'.  This seems to be set up as follows:

As mentioned above, on the ARQ/ARR Ruby there is no wire between F1 on the switch and F1 on the cut-out.  Both F1 and F2 on the switch (where they are connected together) go to F2 on the cut-out. The cut-out has no wires from F1, therefore, the terminal that splits the two resistances in the cut-out is not being used so they cannot be being used separately. 

In the Summer/Low/Half setting, the switch does not include the D terminal so there is no connection on the switch between D and the combined F1 and F2.  The field circuit coming from the dynamo via D resistance includes two resistances R1 and R2 on the way to F2 so the charging rate is as low as it can be.

Once the switch is moved to the Winter/High position, switch terminal D is connected to switch terminal F1 and F2 which connects D directly to cut-out F2 which short-circuits both resistances R1 and R2.  The resistance in the field circuit is a low as it can be so the charging rate is as high as it can be - so there is no intermediate charge rate.

Moving the switch to the Side/Tail position does not change the charging circuitry - switch D and F1/F2 remain connected to cut-out F2. 

Moving the switch to the Head position connects switch D to switch F2, which does not change the charge rate as both resistances remain bypassed. 

Therefore, the Seven appears to have two charging rates - Summer/Low/Half and Winter/High - this higher rate is retained when the switch is in both of the lighting positions.  (As the field fuse is in series with the two resistances, it is eliminated from the circuit for all settings except Summer/Low/Half.)

[John Cornforth]

Thank you Colin for that detailed reply, I was going to reply myself but you have saved me the trouble !

It does seem that the Lucas CFR2 cutout was adopted by several car manufacturers, some adopted the 3 rate charging option but Austin (as far as I'm aware) stuck to 2 rate for the Seven.

I suspect that the mighty Lucas would have offered a complete electrical solution to car manufacturers, and would have "held the hands" of their own designers during development. Naturally, their solution would preferably involve all Lucas components, unless the manufacturer insisted on mixing and matching with other component suppliers if they could strike a better deal.

[Colin Morgan]

Presumably with the Seven dynamo putting out a maximum of about 10 amps, there wasn't much point in having three levels of charge? It might as well as work as hard as it could unless needed on the 'Summer' setting that protects the battery from damage?

[JonE]

Thanks both! - so do I surmise that its merely the addition of an F1 terminal on the unit that stops it doing that, as even with present units, the resistance is "ready" as per John's diagram so to speak? And getting rid of the "formally-bodged" F1-F2 connection on the switch?

I only started looking again when looking at the complete mismatch between electronic regulators and the C35 dynamos, which are - as several old forum threads show - ALL incredibly low in field winding resistance (1.5/6) presumably for a very position reason - the third brush. The demands of the new-fangled units are higher resitance there - 2.5/3.5 ohms - and are encouraging expensive, perhaps unneccessary rewinds.

[JonE]

Just working through the Alvis material, does the manual actually refer to Winter as 'FULL Charge position', Colin?
It seems that, as that is the interim position utilising one resistance, it is actually the medium/middle setting.
With a CFR2 here now to study, I'll try and work out how easy it is try it all out and see if it offers anything useful.

If anyone has a broken CFR2 with defective cutout and lost resistances, I'd be interested to acquire one please. Don't need a lid.

[Bob Culver]

Ford 8s got by with a single charge rate about as the Ausin on Winter.