Positive v negative earth?

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Owlsman
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Positive v negative earth?

Postby Owlsman » Thu Sep 12, 2019 5:03 pm

Hello chaps - bit of 'electrical' advice please.

My '62 saloon is currently positive earth and with a dynamo. I'm seriously thinking of having an alternator fitted and I'm leaning towards a Dynamator jobbie i.e. the one that has all the alternator gubbins but within a dynamo casing to maintain the original appearance. They're a bit pricey compared to a standard alternator but …….you can't take it with you! :D

1. Has anyone fitted a Dynamator? If so, are they any good?
2. Is it worth i.e. what are the benefits of changing over to negative earth? I don't currently have a radio and/or cassette and don't particularly plan to fit one. Can I realistically rule out a car radio if I stick to positive earth?
3.The car is fitted with both a voltmeter and an ammeter......I know, I know!! The ammeter is in the -30 to +30 range so, as I've read that the output of the Dynamator is 45 amps, do I need to 'upgrade' the ammeter to -60 to +60? What's the worst case scenario if I didn't?
4. I can buy a positive earth Dynamator (are positive earth 'normal' alternators available?) so, if I have it fitted, to maintain originality -- appearance and positive earth -- can I later switch to negative earth? Perhaps I'd be better asking the Dynamator people that really.

Sorry, quite a few questions there...….but they just kept coming, the more I thought about it.

ampwhu
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Re: Positive v negative earth?

Postby ampwhu » Thu Sep 12, 2019 7:03 pm

according to "folk", the positive-earth cars rust faster than the negative-earth cars.

all 3 of my BMC cars have alternators. why wouldn't you want to fit one? Dynamo technology isn't really up to modern standards. When people go on about originality, I do laugh. If people are that worried about being original, they aren't using the same battery, tyres, oil, air and possibly brake parts.

fit the alternator.

SteveClem
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Re: Positive v negative earth?

Postby SteveClem » Thu Sep 12, 2019 7:10 pm

Agreed, makes things so much more simple if you need to fit any accessories...radio, heated screen etc.
The rusting thing sounds like an old wife’s tale though... just ducking my head now :lol:

philthehill
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Re: Positive v negative earth?

Postby philthehill » Thu Sep 12, 2019 8:45 pm



geoberni
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Re: Positive v negative earth?

Postby geoberni » Thu Sep 12, 2019 8:48 pm

Unless you have a manic compulsion to stay with the Positive 'Ground' then switch it over.

Back in the beginning of the automotive industry, cars could be either and it didn't matter. It's not actually 'Ground' because the car is sat on rubber tyres, it's just a convenient way of routing all those electrical circuits back to the battery/generator; they do the same thing on aircraft and they're nowhere near the 'ground'. It's finishing the wires at the last thing you're operating and using the bodywork to complete the circuit, saving on time, materials cost and effort to build/maintain.

The whole 'Positive Ground rusts more/sooner' theory comes from the early days of the telegraph industry when they were messing with Positive/Negative grounding alternatives and found galvanic corrosion worse in in some conditions, all due to differences between 'true' Ground and 'system' Ground. I forget the exact details, but it's very easy to get circulating currents if your 'Earths' are not all at exactly the same potential.

In answer to your Questions....
1 - no idea, but they're great if you want a pretend dynamo look
2 - impossible to find a Pos Earth entertainment device unless you're looking to fit a genuine 1950/60s radio as many had a change over switch
3 - in High charge/discharge situations, your ammeter could bang the needle on the stops
4 - I doubt it, they've made it Neg Earth especially, it can't be switched at a whim. Might be able to change the regulation side of it for a different module I suppose. Ask the makers.
Basil the 1955 series II

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JOWETTJAVELIN
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Re: Positive v negative earth?

Postby JOWETTJAVELIN » Fri Sep 13, 2019 12:26 pm

Dynamo technology isn't really up to modern standards.
The entire car design isn't up to modern standards.

There doesn't seem to be any support for keeping things as they are. The dynamo/alternator debate goes on ad nauseum. The dynamo setup is adequate provided the voltage regulator is set correctly and the system has been correctly serviced... I had a faulty voltage regulator which allowed a current of over 15 amps and 19 volts from the dynamo... and still people rubbish them.

I suspect one reason for the alternator obsession is neglect of the charging system and the very short journeys most old cars are subject to, which are very bad for a car.

Whatever you do, if you have the Lucas 'helmet' battery terminals, don't cut these off to fit the SMMT clamps, because they are getting rare now. Remove the entire leads instead and fit new ones, and put the Lucas type somewhere safe.

Oh, and don't forget to disclose any modifications to your insurance company!
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myoldjalopy
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Re: Positive v negative earth?

Postby myoldjalopy » Fri Sep 13, 2019 12:46 pm

" The entire car design isn't up to modern standards." Ha ha! Beauty! 8)

geoberni
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Re: Positive v negative earth?

Postby geoberni » Fri Sep 13, 2019 1:08 pm

JOWETTJAVELIN wrote:
Fri Sep 13, 2019 12:26 pm
Dynamo technology isn't really up to modern standards.
The entire car design isn't up to modern standards.

There doesn't seem to be any support for keeping things as they are. The dynamo/alternator debate goes on ad nauseum. The dynamo setup is adequate provided the voltage regulator is set correctly and the system has been correctly serviced... I had a faulty voltage regulator which allowed a current of over 15 amps and 19 volts from the dynamo... and still people rubbish them.

I suspect one reason for the alternator obsession is neglect of the charging system and the very short journeys most old cars are subject to, which are very bad for a car.
Having a dynamo that could deliver 15 amps at 19 Volts is nothing to brag about; what's the extra volts going to do apart from perhaps weaken a few lamp filaments!
The dynamo set up is not 'adequate' if you have more load than originally designed. If you've changed to halogen headlamps, added fog/spot lights, heated read window etc, it's not going to cope well.
My dynamo is very happy most of the time, but if I put the headlamps on the Ammeter shows a slight discharge; the previous owner decided to fit halogen lamps... :roll:
Before someone says it, I know the wattage of a standard halogen lamp is only 10 or so watts more than an old filament lamp, but it all adds up in the total load.
I remember reading a personal account of being a UK Motorway Police driver in the 1960s with Ford Zephyr/Zodiacs. They complained that if they stopped at an accident with their lights on and the cars idling, the battery was flat in about 15 mins.
An alternator will deliver sufficient power at idle.
Basil the 1955 series II

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ampwhu
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Re: Positive v negative earth?

Postby ampwhu » Fri Sep 13, 2019 6:05 pm

i agree that these cars aren't up to modern standards. This is why I have modified all 3 cars and will continue to do this for years to come. I personally find standard cars unsafe on modern roads with the fools that drive 500bhp german autobahn stormers.

fit an alternator and disc brakes. It makes sense. Then get out and enjoy your motoring again.

ampwhu
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Re: Positive v negative earth?

Postby ampwhu » Fri Sep 13, 2019 6:08 pm

as for keeping things as they are...….

who buys a paper now to read current affairs
who posts letters
who has old wooden window frames in their home
who hand washes their clothes
who goes to Clacton for a 2 week holiday in a caravan

the list is endless. Improving cars is sensible and evolution.

oliver90owner
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Re: Positive v negative earth?

Postby oliver90owner » Fri Sep 13, 2019 7:04 pm

Steady on. It all comes down to practicality or originality. Two different camps. I’m in the latter.

Anyone fitted airbags in their minor? Anyone put an extra collapsible link in the steering column? Anyone fitted extra crumple zones fore and aft?

Do remember that when these cars were made, batteries could be topped up regularly with distilled water, plates were far more robust and they regularly lasted up towards ten years, given adequate sizing and with regular maintenance carried out on the system.

geoberni
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Re: Positive v negative earth?

Postby geoberni » Fri Sep 13, 2019 7:31 pm

ampwhu wrote:
Fri Sep 13, 2019 6:08 pm
Improving cars is sensible and evolution.
But most people feel that's what new models are for. If you want evolution, then stick to modern cars with their airbags, antilock brakes, and driver assistance etc, etc, etc..

The vast majority of Classic/Vintage owners do it for the nostalgia aspect in some form or another, whether preserving the heritage, reliving their youth, or just a love of tinkering on a car (something that is near impossible on modern vehicles); no different from people volunteering on Heritage Railways. Most of them can't afford their own steam engine, so they work as a team to keep them going.
People own and work on vintage aircraft because of the love of the aircraft. The CAA will make them fit an Anti-collision light, and install a modern radio with up to date frequencies, but they generally don't swap out the engines etc.
(there are some notable exceptions, but they are exceptions rather than the rule)

Your basic argument doesn't really hold up because where do you 'draw your line in the sand' over what should be upgraded.
What I think you're saying is you want to make selective improvements as though you're still back in the 1970s/80s, an era when you could still do 'home improvements' on your car, but you don't want to come too far up to date.

But changing to an alternator is something to do out of necessity, because you need the extra power, not because a
Dynamo technology isn't really up to modern standards.
It provides a 12 volt charging system for the battery and to run ancillaries like lights... that's the job and it does it well, unless the load is increased beyond it's designed capabilities. :)
Basil the 1955 series II

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myoldjalopy
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Re: Positive v negative earth?

Postby myoldjalopy » Fri Sep 13, 2019 8:32 pm

And I, for one, have retained my wooden sash windows in my Victorian house because putting plastic in looks like s***e.
Just because something is 'modern' and flash does not, necessarily, make it better. The modern world has lost a lot of charm. I could elaborate but, really, its not necessary 8)

IslipMinor
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Re: Positive v negative earth?

Postby IslipMinor » Sat Sep 14, 2019 9:11 am

Some late Minors were fitted with a +ve, yes, POSITIVE earth 11AC Lucas Alternator (45A) - I have one somewhere in the garage that was fitted to various cars of mine in the 60's and early 70's. The wiring is a bit complicated in comparison to the simple plug-in of the later ACR alternators, as it used an external control unit (11), a 6RA relay (56) and a 3AW warning light control unit (57). This is the extract from the BMC Workshop Manual dated 1970:
Later Minor with Alternator v2.jpg
Later Minor with Alternator v2.jpg (76.56 KiB) Viewed 329 times
I chose not to go down this 'originality' route with our Minor, and fitted a small self-contained Lucas ACR alternator in the 70's. The sight of a typical Lucas alternator could even be considered as 'original', but not negative earth! That came with the ACR alternator range. Since then the alternator has been replaced/upgraded, and is currently a -ve earth 'Lucas' type with 75A output. Heated front screen, 4 x halogen front bulbs etc. means that on a cold winter's night I have a bit of spare charging capacity!

The ammeter is a 60-0-60 and on initial startup will swing across to ~60A for a few seconds, but then settles to a few amps charge to replace the capacity used to start the car. There is a problem though! With a typically small v-belt pulley, the idle charge capability is quite high, which is good in one way, but turning on headlights, heater etc. drops the idle speed quite a bit - need a 'modern' idle speed control unit! I have to run a high(ish) idle speed with the 1380 anyway, so a little more (1100 rpm) is not too bad.
Richard



ampwhu
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Re: Positive v negative earth?

Postby ampwhu » Sat Sep 14, 2019 1:48 pm

myoldjalopy wrote:
Fri Sep 13, 2019 8:32 pm
And I, for one, have retained my wooden sash windows in my Victorian house because putting plastic in looks like s***e.
Just because something is 'modern' and flash does not, necessarily, make it better. The modern world has lost a lot of charm. I could elaborate but, really, its not necessary 8)

i have plastic sash windows. you'd never notice the difference and they won't ever rot away.

myoldjalopy
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Re: Positive v negative earth?

Postby myoldjalopy » Sat Sep 14, 2019 5:42 pm

I expect I would notice the difference, I do notice these things. Frequently. Mine have been in for 115 years. The expected life of a plastic window is only 20 years - they may not rot but they dry out and crack, plus the opening mechanisms frequently break, or the double glazing is compromised and they steam up inside.......

KeithL
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Re: Positive v negative earth?

Postby KeithL » Sat Sep 14, 2019 5:50 pm

myoldjalopy wrote:
Sat Sep 14, 2019 5:42 pm
I expect I would notice the difference, I do notice these things. Frequently. Mine have been in for 115 years. The expected life of a plastic window is only 20 years - they may not rot but they dry out and crack, plus the opening mechanisms frequently break, or the double glazing is compromised and they steam up inside.......
...and the silicone sealer drops out, and they discolour. I agree with myoldjalopy - just because it is new doesn't necessarily mean it is better.


PoolGuy
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Re: Positive v negative earth?

Postby PoolGuy » Sat Sep 14, 2019 5:56 pm

KeithL wrote:
Sat Sep 14, 2019 5:50 pm
I agree with myoldjalopy - just because it is new doesn't necessarily mean it is better.
Alternators are though, and it’s not like you see them
most of the time. Halogen headlights are better, modern oils are better, but you’re right about upvc windows, they’re rubbish compared to decent wooden ones.

ampwhu
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Re: Positive v negative earth?

Postby ampwhu » Sat Sep 14, 2019 7:50 pm

Disc brakes are also better. The 1st and best mod on a classic car.

jagnut66
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Re: Positive v negative earth?

Postby jagnut66 » Sat Sep 14, 2019 8:18 pm

I personally find standard cars unsafe on modern roads with the fools that drive 500bhp german autobahn stormers.
Agreed!
I would also include the current obsession with 4 x 4's and People Carriers, for most it seems it is little more than an extension of their ego! They drive them like they are driving a tank, they 'own the road' and are somehow superior to lesser mortals! :evil: :evil:
Personally I think the size of cars should be limited, so they don't block the vision of the car behind with the fat ar*e of these things.
And 4 x 4's should limited to those who can justify their usage (farmers etc.).
Another good reason for getting rid of them is that most are also pig ugly! (Nissan Junk **sorry** Juke for example)
Mind you this is just my opinion..................
And I, for one, have retained my wooden sash windows in my Victorian house because putting plastic in looks like s***e.
Just because something is 'modern' and flash does not, necessarily, make it better. The modern world has lost a lot of charm. I could elaborate but, really, its not necessary 8)
Also agreed, modern doesn't mean better, just more convenient, in some circumstances.
I must confess though that, as I want to use my car regularly, I will be fitting an alternator, disc brakes and period style (grey webbing and chrome buckles) seat belts.
I also prefer old wooden sash windows, though I no longer live in a Victorian house, my current home dates to 1950.
To me old houses are full of style, charm and character, which modern houses somehow lack.
I'm also a fan of antique furniture.
Modern houses also come with nothing more than a postage stamp (remember those :wink: ) for a garden, so another negative for me I'm afraid.

I would imagine most on here have got my type / character pinned down, boxed and labelled by now........ :lol:

So I might as well go for broke and admit that I would also bring back hanging for murderers, rapists and peadophiles!!

Best wishes,
Mike.
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