>John Macartney wrote :
>
>> 2. The change from positive to negative earth appears to have been
>> brought about by no less an organisation than 'old Joe' being
>> pro-active rather tan re-active. Herewith an extract of a
engineering
>> paper dated March 1962 which I turned up in the Gaydo archive
today.
>> It runs to about six pages, is substantially technical and I've
taken
>> only a few key points from the summary:
><snip>
>> * Conventional dynamos are unable to meet anticipated discharge
rates.
>> Higher output dynamos can be designed and manufactured but this
brings
>> additional size, weight and cost penalties that vehicle
manufacturers
>> are likely to find unattractive.
>> * The alternator has already proved from research that it is
capable
>> of providing greatly enhanced electrical performance and at
rotational
>> speeds significantly lower than establised direct current dynamos.
Randall replied:>
>However, IMO, this is yet another example of the 'excuses' I made
reference
>to. There is absolutely no reason that an alternator can't be made
in a
>positive ground configuration, and in fact some of the early Lucas
models
>were externally switchable between positive and negative. Even later
units
>can be switched by installing the diodes backwards (that is,
installing the
>'positive' diodes on the ground side and vice versa).
Wouldn't disagree with any of that, Randall and all I would do is to
re-paste an additional extract, thus:
>While there is no intrinsic difficulty with a Positive earth
>system, there is ample evidence that in some world markets, a
negative
>earth system is an accepted standard. Joseph Lucas Limited feels that
>to continue with an earthing standard that does not recognise this
>convention could lead to normal maintenance and repair procedures
>being compromised by those who are technically unaware of specific
>system differences.
Having read the whole paper, I wouldn't necessarily agree with you
that this is an 'excuse' - isn't it more a statement of obvious
standardisation? The issues in the main paper were clear:
1. The customer base (end user) was insistent on having or using more
electrical services that were consumption heavy
2. Other component suppliers were clearly moving towards negative
earth systems in isolation
3. Manufacturers who failed to recognise this reqmnt and so equip
their cars would lose sales
3. There was no question of system 'choice' (switchable or
specifiable) as 'choice' can confound reliability and that affects
sales
4. The U.S. markets was cited as critical to all manufacturers and
Lucas was in no doubt the U.S. insisted on negative earth - period.
None of this was a phenomenon peculiar to Standard Triumph - read also
for every other UK manufacturer as they all changed to neg earth in a
relatively short period.
Cheers, Jonmac
All in all, I suppose it's the K.I.S.S. philosophy? If you give people
a choice on something as fundamental as electrical services, you
seriously risk falling flat on your face on both choices and the
customer blames the car or the washing machine "because it don't
work."
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