> G Mann wrote:

> That would be 28 Peak HP.... so you need those 18 gears to
> keep the little engine exactly in BOTH it's best torque and
> best Horsepower sweet spot to gain max efficiency to achieve
> that "perfect" mileage.

And if the only duty of the engine was to run the generator that
powers the electric motors it _would_ be running at exactly it's
sweet spot.

And then, just to pick at nits, *smiles* there is hardly any big
trucks on the road with an 18 speed transmission.  The 18 speed's
primary duty is for off-road service.  9 and 10 speed are the
most common.  It's not rare to find a 13 speed, and a 15 speed,
though unusual, is not unheard of.

Since I'm on this rabbit trail already, I'll continue...

The RoadRanger type transmissions used in the big trucks today
are a 5 speed main gearbox with auxiliary gearing.  Using air
pressure from the air brake system, there are "switches" on the
shifter that operate "solenoids" to change the auxiliary gears.
It can be a large ratio change (range) or a small ratio change
(split).

9-speed = no splits, 5 in low range, 4 in high range
10-speed = no splits, 5 lo, 5 hi
13-speed = 5 lo, 4 hi with splits
15-speed = 5 lo with splits, 4 high
18-speed = 5 low with splits, 4 high with splits

--   Philip

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