12volt conversion

[Andrew Eales]

So after a hiatus (more kids) I have finally found some time to get back on with the work to the Bradford "special" in the workshop. Before I started work on this some 3 years ago I rigged up an ignition circuit and and attached a 12volt car battery I had lying around. This got the engine started, which was the main plan to check it did indeed run.
I ordered a 6 volt Lincoln battery with a plan to keep it all original.
Now I have returned to the project after 3 yrs this 6v battery can barely turn the engine over and appears to only be able to produce a very weak spark. It is fully charged.
So there is only one answer for it and that's a 12 volt conversion. What exactly will I need for this ?
Will the generator produce 12 volts ? In which case will I need a new regulator ? Do I need a new coil and condenser ?
Does anyone know the resistor required for the fuel sender ?
Could I have damaged any of the ignition system by running it for a couple of minutes on the 12volt battery ??
Thanks all !

[Keith Clements]

I hope someone who has done the conversion can advise.

Firstly, leaving any lead acid battery more than 6 months without a discharge/ charge cycle will probably cause the plates to sulphate and thus reduce its capacity. It may be possible to restore condition with additives or special charge cycles, but I doubt it.

It is likely that any 6v components that you attached 12v to will have been damaged. Essentially you would be either putting twice as much current through them than for which they were designed. A capacitor might survive as might a coil if not left attached for too long. The regulator and dynamo/generator will need changing anyway as part of conversion. The starter motor might have survived provided you only had it going for a few seconds.

[Andrew Eales]

Cheers Keith,
I was led to believe that the starter motor was quite happy with 12V, so i hope to not have to change that. I'm happy changing the coil condenser and regulator, but was hoping that would be it.
Maybe someone else can chip in..

[george garside]

A couple of thoughts -

all pre CC Jowett commercials exept the 10hp used 6volts to save weight (and taxation) and started fine even on a frosty morning provided the battery was ful10 l and everything in good nick.

Same went for many other makes and indeed the Ford *8 and 10 right up to ?1958 were 6 volt, however several owners converted them to 12 volt and there were articles in practical motorist etc on how so to do the advice being that the 6 volt starter would cope with 12 volt as its use would be intermittent as is the want of starters unless something else is badly amiss.

There is of course also the starting handle and it used to be very common to use this on a frosty morning to 'save the battery'

For ''classic'' use 6volt should be fine and particularly if always coupled to a pulse charger when not in use (Aldi and Lidle usually have them once a year for about £14 whih is much cheaper than elsewhere. I have two one for my motorbike and one for my caravan battery and they look after the batteries extremely well , greatly extending thir life ( my last caravan leisure battery lasted 7 years)

george

[Andrew Eales]

Mine is a CC but its a very early one so 6V. I could try a different 6v battery but the last one was over a £100 and its lasted no time. It was left fully charged. Ill look into it a bit more..
Someone must have converted one as I thought it was common practise a while ago.

[Andrew Eales]

Ok I've found a reasonably priced 6V battery on the web £69.. Its a 56 Ah capacity. Do you think that will be enough ? I intend using the starter handle on most days but i would like a reliable ish spark, which is very weak at the moment. What I'm trying to avoid is spending lots renewing the 6V system (coil etc due to a weak spark) only to have to convert it to 12V and have to replace it all again ! I am keen to keep this part original as other than the metal work there is not much original left !

[PAUL BEAUMONT]

No! 56Ah is probably an MGB battery. These use 2 6v batteries in series to create 12v and as there is a reasonable market for them, tend to be fairly cheap. You will struggle to start the Bradford with them, though the CC has a better starter motor than the earlier ones. A 12v starter for the CC should not be hard to come by. Are you still using semaphores? these are likely to be the most expensive part of a conversion, but 6V one are probably readily saleable. A weak spark did not ought to be the result of a low battery I suggest you check all the electrical connections and especially the earth connections. My 6V CB almost never starts with the starter, but it starts reliably with the handle even if the battery is really down

[richard turner]

Watts=volts times amps!!!
Starter. dynamo, No problem. Change coil. Bulbs throughout. 6v semaphore seem to work ok but will leap alarmingly to attention! Petrol sender needs to be changed and a from memory 2ohm resistor place in series to gauge. Change coil and windscreen wiper motor. Change regulator to 12v. Swap to negative earth! Rich

[george garside]

Apart from the availability of cheaper 12 volt batteries and brighter headlights I can't see much point in changing to 12v on a vehicle that will not be in regular daily use and may and which is probably unlikely to do much nocturnal exercising. As to starting I used to drive a 28hp Bedford O type. lorry that was 6 volt and it started on the starter in the thick of winter! The key is to keep the ignition system in really good order including the plug leads and of course the plugs themselves

george

[Andrew Eales]

Thanks everyone..

I have no indicators at all so thats not an issue, same with windscreen motors.
If I were to go down the negative earth, 12V route I might as well fit an alternator, and remove the need for a new 12V regulator at all.
I have a small alternator and a 12 volt battery to hand. I assume the starter is of the old type that will still turn the correct way when the poles are reversed - maybe I should check that ! Its such a basic simple system that other than the resistor for the fuel gauge sender I can't really see a reason not to !
If we know the resistance of the fuel gauge sender then an equal resistor in series with it should drop the voltage by half to 6V and hey presto !

Alternatively I could spend another £120 on a 6V battery and try and look after it a bit more - (pending no more children on the horizon !)

Its food for thought, and as its too cold to go in the workshop now I've plenty time to mull it over !

[David Kemp]

Convert to 12v, I did it years ago on my Bradford, better starting better lights. Also meant I could fit a radio. Regulator of a Javelin is the cheap way to go, change bulbs & you have converted. Sorry also wiper motor.
If you change polarity, you have no problem with starter, indeed your six volt starter will run for a very long time with 12v through it.

[Andrew Eales]

Cheers David,
That's the decision made then.
What did you do with the fuel sender ?

[george garside]

not sure about this but would it be possible to fit a resistor in the wiper motor circuit to drop 12 volts to 6. Otherwise a CC Bradford 12 volt motor would be fine as would many pre war motors ? autojumble or JCS. Another thought would two 6 volt motors in series work and give you the passenger a view out!

george

[David Kemp]

Never did anything with fuel sender it did not seem to matter. Never failed. It is basically just a variable resistor.

[Andrew Eales]

No wipers to worry about george. Not at the moment anyway !

David,

Thanks for the info ref the fuel sender. Its a done deal now !

Andrew