Hydraulically rethinking vintage cars with positive grounded chassis

Most vehicles was made with positive grounded chassis before 1960's, though nowadays all negative grounded chassis.

The title picture is just an example: the beautiful 1955 Ford Thunderbird, and many antique collectors are still cherishing such kind of vintages.

I have read many articles that explain why such configuration was preferred in last century, however I have my own thought.

By comparative study with hydraulic circuit, I believe electrical positive earth system is more natural than negative one.

As illustrated in following figure, we can see a typical hydraulic motor in the left side, and it has small oil port to intake fluid power, plus large oil port to discharge the exhausted or say retarded oil.

The working pressure equals the inlet pressure minus the outlet one, aka back pressure, and the oil velocity at inlet is surely larger than outlet one, because mechanical output will retard oil speed so as to extract energy.

As flux = velocity * SectionArea, and flux is conservative in flow loop, thus the higher speed, the lower section area of hose, hence smaller diameter.

If the outlet port size is lesser than the inlet one, then it is anti-natural, and higher back pressure will be seen, consequently output work will be reduced.

The often-seen same size of inlet & outlet is just for the convenience to support both clockwise & anti-clockwise rotation, but will sacrifice somewhat efficiency.

In fact, electrical circuit can also be considered as special fluid circuit, just with different fluid media: the former electron & the latter oil, and electron invisibly flow from negative polar to positive polar.

By analogy, the electron velocity at positive terminal should be lower than at negative terminal, because after fording through load for work output, electron will be exhausted, thus a thicker positive post will quicken the return of electron.

Below figure shows: despite current in right side of battery & load does equal left current amperage, but left electron speed is slower than right side, thus left wire should be thicker than right side.

Now I have a rude awakening: the positive grounded chassis is just complying with above analysis, because engine block & vehicular metal frame can be deemed or imagined as the thickest conductor.

Anyway, some readers may not know that the electron velocity in conductor is very low, just like as snail speed. For instance:10 Ampere current in 2 mm diameter copper wire is equivalent to circa 0.25 mm/s speed of electron.

Therefore, for bipolar electrical DC small to medium power component, different thickness of connecting wires does not make much sense.

Some guys have done many experiments on regular gasoline cars for comparison between positive and negative grounded chassis system, but they never observed significant discrepancy in performance, though there may be some minor advantage in positive system.

Conclusion: if not for good practice of standardization, in fact, arbitrary choice is okay in selection of positive or negative grounded chassis for fossil fuel vehicles.

But pure Electrical Vehicle (EV) is another story, as large to super currents surge in circuit during all operation time, unlike light duty of electrical power in regular cars.

Current EV-makers are not aware of the benefit of positive grounded chassis, and they still follow the dominant polarity practice of conventional automobile industry.

In contrast, lithium battery industry has done a smart change for decades: they manufacture heavy-duty batteries with big surface metal shell in positive polarity!

Theoretically, EV with positive grounded chassis will slightly improve efficiency by increment about 1%. Too tiny incentive? but better than nothing!

So I hereby call EV industry for the positive grounded chassis system.

Reference:

What Is The Speed Of Electron In A Current Carrying Conductor?https://www.scienceabc.com/nature/what-is-the-speed-of-electricity.html

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