Author Topic: Changing earth  (Read 2797 times)

Offline Tone

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Changing earth
« on: 17.07. 2009 20:57 »
Hi All, What do you have to do to change from possitive to negitive earth?

Offline a10gf

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Re: Changing earth
« Reply #1 on: 17.07. 2009 21:39 »
... just being curious, why  ????

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Offline Rusty nuts

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Re: Changing earth
« Reply #2 on: 17.07. 2009 22:11 »
Dynamo polarity will have to be changed. Apart from that nothing to do except swap over battery leads, earth lead(s).
The former will cost, so no point unless you are having dynamo rebuilt &/or are fitting a new loom & anyway
there is no benefit in doing it.
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Online groily

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Re: Changing earth
« Reply #3 on: 17.07. 2009 23:01 »
No need to spend any money. You want the thing to run in the correct direction of rotation (no choice there, the engine dictates that) with the chosen side to earth. Easiest way is to swap the field coil winding ends round so the one that goes to the F terminal on the end-cap goes to the dynamo body and the one to the dynamo body goes to F.
Reason for doing it is up to you - most usual reason would be because you've got an electronic regulator for free and it runs on the opposite polarity? Or you've bought one which has the opposite polarity to what you intended? While the electronic regulator cares about the earth, the dynamo doesn't give a hoot. Easiest test is on the bench, with the dynamo seen to turn as a motor, in the direction you want it to turn as a generator, with the earth of preference. To test you've got it right - neg earth in this case - connect battery neg to dynamo body and positive to a wire that bridges F and D. It should turn the way you want. If you don't bridge F and D, nothing will happen. Nor will it if the dynamo is still connected to its drive system.
There be other ways, but this is my favourite.
Bill

Online trevinoz

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Re: Changing earth
« Reply #4 on: 17.07. 2009 23:15 »
Groily,
            that is incorrect. The way to change polarity is to flash the field with the desired polarity.
If the field connection is reversed, the rotation is reversed.
Trev.

Offline Tone

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Re: Changing earth
« Reply #5 on: 18.07. 2009 09:32 »
Sorry Guys, I didn't have much time when I asked the question, the reason for wanting to change is I'm thinking of changing to an altinator system the one i've been looking at I think its Alto? only comes in negative earth, I've already changed to 12volt and have a very bright light and with the dynamo it has to keep the revs up quite high to ensure charging.Has anyone else done this?

Offline Josh Cox

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Re: Changing earth
« Reply #6 on: 18.07. 2009 11:31 »
Tone,

Is your dyno chain driven or did you convert belt with the SRM kit ?.
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Offline fido

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Re: Changing earth
« Reply #7 on: 18.07. 2009 12:54 »
If you are not using the Lucas dynamo all you need to do is swap over the battery leads, perhaps using a bit of red and black tape to denote + and - terminals on the respective wires. Obviously you will not be using the normal mechanical voltage regulator, which can be removed or simply disconnected and left in situ. You may also need to reverse the ammeter wires.

Offline A10Boy

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Re: Changing earth
« Reply #8 on: 18.07. 2009 13:53 »
Trev is correct, two things to do.

1/ Swap over battery terminals.
2/ Then re polarise the dynamo by flashing a wire from the "hot" in this case Pos side of the battery to the field winding on the dynamo. It can be done in the dynamo or at the F terminal on the regulator.


Here's how.

http://www.youtube.com/watch?gl=GB&hl=en-GB&v=wH_yIeKsBSM

Regards

Andy

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Online groily

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Re: Changing earth
« Reply #9 on: 18.07. 2009 15:54 »
Sorry that was total BS guys. Mea culpa. Thing was rotating the right way in the first place. Brain out of gear.
Bill

Offline Tone

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Re: Changing earth
« Reply #10 on: 18.07. 2009 16:01 »
I've still got the chain drive, the guy I spoke to about this does either an alternator for the original chain drive or one for a belt drive kit which her supplies.

Online Triton Thrasher

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Re: Changing earth
« Reply #11 on: 18.07. 2009 17:20 »
Alton has got itself a pretty dodgy reputation in some quarters, such as the Velocette Yahoo group.

Having said that, I use one and it works well these days, after one regulator failure and one Alton alternator failure.

Offline a101960

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Re: Changing earth
« Reply #12 on: 18.07. 2009 17:26 »
If you are going to retain the dynamo and I would advise you to do that. then you really do need a belt drive conversion. If you switch to an alternator you will not gain much advantage over a belt driven dynamo. The reason for this is that although the alternator has a much higher output capacity. It's operating characteristics are similar to a dynamo. That is definitely the case with an Alton. What I mean by that is that the alternator will dish out a high charge at cruising speed, but you will find it less than adequate around town. The Alton does not behave in the same way as a car alternator whereby it will balance the battery in urban conditions with your lights being operated. I have a 12v -ve dynamo system fitted with an H4 40 watt lamp and it is more than adequate. I changed to -ve to enable me to fit LED lamps to the speedo and tacho because they are only available  in -ve configuration. I am not saying that the Alton is a bad device, but it will probally not deliver what you think it will. The regulator will also require isolating from the battery when the engine is not running otherwise it will gradually discharge your battery. You are doing the right thing by researching the subject before committing yourself to any action.

John

Offline Tone

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Re: Changing earth
« Reply #13 on: 18.07. 2009 18:40 »
Thanks Guys, John, I get what your saying, the trouble is i've heard some stories about belt drives, not sure if they are reliable.

Online Triton Thrasher

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Re: Changing earth
« Reply #14 on: 18.07. 2009 18:45 »
My first Alton was 3 phase and was really no better than a Lucas dynamo running at 12V.  It didn't charge at all at under about 2500rpm.  Is that what you have A101960?

When it failed in service the Alton guy changed it to single phase (without admitting his 3 phase version was bad) and it was much improved.  Starts charging at anything over idle. It's done many thousands of miles since.  I'm not recommending it, because the version sold for Triumphs doesn't actually fit: I have to set pinion backlash with a wooden wedge.  Also some Velo owners report having got through several Altons.