Author Topic: alternator  (Read 359 times)

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Offline timsdad

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Re: alternator
« Reply #15 on: January 31, 2019, 07:15:38 am »
The polarity is the same either way, Ginge. There are two AC inputs from the alternator and the positive and negative output spades, all being insulated from the instrument, can be taken to where ever they need to go depending on what polarity the bike is.


Ray
Just a motorcyclist.

Offline Donald

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Re: alternator
« Reply #16 on: January 31, 2019, 10:58:55 am »
Hi there, I have only wired my bikes as neg earth. But if you read the description  ,it states ok for positive earth

Offline Ginge

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Re: alternator
« Reply #17 on: January 31, 2019, 03:56:20 pm »
Are they the square matchbox sized bridge rectifiers? Four spade terminals with one set sideways?  Or is there something else being used that regulates as well?
Ginge.

Online Vreagh

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Re: alternator
« Reply #18 on: January 31, 2019, 04:05:23 pm »
The square units with spade terminals sticking out of the top are good recifiers but will not regulate. The rec/reg units have fins sticking out of the top, two bolt holes either side and four wires out of the side and make converting to 12v very easy.

Online Tman

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Re: alternator
« Reply #19 on: January 31, 2019, 04:05:41 pm »
You'd need something else as well, a regulator. ;)


Offline timsdad

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Re: alternator
« Reply #21 on: February 01, 2019, 06:57:16 am »
They are the ones, Ginge, but much smaller than a matchbox and cost about £5 in our, sadly, funny currency. As has been said several times, these are rectifiers to rectify the current from alternator AC to battery DC and are just a simple replacement for the original plate-type rectifiers that were fitted by the factory.

You just need to fit these replacement rectifiers if you are still running a six volt bike with its original up and down wiring to the complicated light and ignition switch. If you are converting to twelve volts, or doing away with the old switch wiring and keeping to six volts, then you will also need a regulator. This can be done on by fitting an expensive electronic regulator/rectifier instrument, that also does the rectifying, or, on 12 volts, by just also fitting a Zenor diode like BSA did when they went to 12 volts in the '60s. This works by monitoring the battery voltage and, in simple terms, 'short circuiting' the excess to earth as the battery voltage creeps up over 12 volts. It sounds harsh but it works very well in practice, was good enough for all the Brit manufacturers back in the day and still works for me.


Ray
Just a motorcyclist.

Offline George B Walke

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Re: alternator
« Reply #22 on: February 01, 2019, 12:16:35 pm »
When I converted my present C12 I did away with that troublesome switch, using a late type barrel switch for ignition and a 3 way flip switch for the lights in the headlamp. As you can see I am not a stickler for originality.
That set up can be varied several ways to suit yourself if needed.

By the By, on an earlier C12 I got so fed up with the auto advance giving trouble I fitted the older C11 distributor type set up (I realise its not correctly a distributor) which was very easy to waterproof with the aid of DumDum and inner tube.

I did more miles on  that C12 than any other I've owned, once even a trip from London to Cornwall and back in a day, never ever let me down. Just another 'wish I hadn't sold it' bike.

Offline timsdad

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Re: alternator
« Reply #23 on: February 01, 2019, 12:47:00 pm »
You must have changed the engine then, George, because there are so many differences in the crank cases.

Ray
Just a motorcyclist.

Offline sidevalve

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Re: alternator
« Reply #24 on: February 01, 2019, 12:52:58 pm »
must admit we still seem to be having a little confusion here as to what I'm doing - 1 - a regulator regulates the current and 2 - a rectifier rectifies it AC=DC. However a modern reg/rec unit does both jobs in one with no need for the crude zener diode regulation or a separate rectifier.  The three wires from the alternator can be linked to give max output [cutting out the switching in/out of coils 'regulation' method used by BSA] and thus giving a simple two wire AC output. Yes the cheap units are neg earth but TBH I cant see any difference there - other than swapping the battery leads [and possibly the ammeter] over there is no difference - unless anyone knows otherwise ? Plus it was a common mod on dynamo units even back in the day. The unit on E Bay is the sort I was looking at and states it is a reg/rec unit so should do the job [if not I get my money back so no loss there]. I think some are perhaps getting confused between regulator and rectifier but if as I suspect [which was my original query] the alternator puts out anything significantly over 12v [all coils charging] when un-regulated then it should work to charge a 12v battery when regulated down to 12v.
If we are doubling the voltage of the bulbs we are halving the amperage so I'm hoping the overall drain will be less. I will need a coil but 12v coils are still quite easy to get at jumbles etc so I don't see a problem there
I have a small Honda with a very similar charging system [also 6v rectifier but no regulator just switch in/out coils] and I'll be trying the theory out on that first. Anyway assuming no-one else has tried this using one of these units I'll report back [have to wait for the weather to improve - shed is like a fridge]

Offline camman3

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Re: alternator
« Reply #25 on: February 01, 2019, 01:06:51 pm »
Thanks for that post sidevalve, saved my typing finger :)
Only thing I would add is, recommending changing to negative earth, as it makes any future changing to led lamps straight forward.
Advantages of going 12 volts explained in attached file .....probably worthwhile if you intend to ride the bike a lot, especially in the dark.
Graham
1957 C12
In sunny (sometimes) Christchurch, Dorset, UK

Offline sidevalve

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Re: alternator
« Reply #26 on: February 01, 2019, 01:47:34 pm »
yes one of the reasons I am considering changing is to use LED lamps [even less drain - so win win  ;D] plus I can see 6v batteries getting harder to find in the size we want [maybe so maybe not but there seems to be less about] and it does mean the wires are carrying less current so bulbs should be a little brighter. Not much of a problem in summer but it's easy to get 'caught out' in spring/autumn and end up riding home in the dusk. Finally it does allow a massive simplification of the wiring around the switch
Besides it's a bit of simple 'tinkering' and which one of us can so no to that

Offline Clive

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Re: alternator
« Reply #27 on: February 01, 2019, 01:51:31 pm »
I have led headlight bulbs on a couple of my 6v +ve earthed bikes, the technology keeps moving on!
Southampton

Offline George B Walke

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Re: alternator
« Reply #28 on: February 01, 2019, 01:55:29 pm »
You must have changed the engine then, George, because there are so many differences in the crank cases.

Ray

That long ago I can't be sure if I did or not,I had a garage full of C series bikes and parts, but I know it was alternator 12v and am more or less certain  I only changed camshaft and timing covers to add the distributor thingy.
I have a note of the reg no somewhere,be nice if it was still around.

Offline camman3

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Re: alternator
« Reply #29 on: February 01, 2019, 02:12:30 pm »
I have led headlight bulbs on a couple of my 6v +ve earthed bikes, the technology keeps moving on!

Yes Clive I agree you can now get led's in all voltages and opposite polarity, but the default and most widely available, hence cheaper, tend to be 12/24 volt negative earth.

Technology in some fields like cctv and security systems is moving so fast it is a job to keep up.....some of it is obsolete within a year or less :o

 
1957 C12
In sunny (sometimes) Christchurch, Dorset, UK