With a 50/34 and 11-28 cassette most gears are 5-7 gear inches and around 9% apart. I consider gears within 1-2 gear inches (eg. 62.6/63.8 and 68.7/69.2) to be overlapping. Of course even if you did want to use all these you would need to be constantly jumping back and forth between chainrings and have a great memory. If electronic front derailleur shifting gets good enough perhaps with careful cassette sizing we could get sequential shifting that uses nearly all the gear combinations.

http://www.sheldonbrown.com/gear-calc.html

Why does a car have 100-300++ horsepower, and humans only have 1/4 - 1/2 horsepower?

A car typically lugs when below 1000 rpm, and likewise with a human grinding at say 70 or 80 rpm.

Conversely, cars redline at 5-7000 rpm, sometimes more -
most humans spin out at like 120 rpm or so.

We're underpowered, have a shitty torque band range, and limited RPM range.
So we need all the damn gears we can get.

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float , hammer , and jog

If you add fuel with no change in external load on the engine, then yes, rpm will go up because you have increased the torque. If you do not let up on the accelerator (reduce torque) or increase the load on the engine, the rpm will continue to accelerate indefinitely until inertial loads blow up your engine by throwing a piston through the head or some other catastrophic failure. If you are driving along on a flat road at a constant speed and you depress your accelerator, first torque will increase. This added torque will overcome the inertia of your car (i.e. external load will increase) and the car will accelerate (and the rpm will then increase) until drag forces equal propulsive forces or until the engine blows up as above.

Freeway driving is typically a very low-load situation and not conducive to meeting the max efficiency point of the engine. Can you cruise at 65 mph on a flat highway in your car with the pedal to the metal? Unless you're driving a go-cart on the freeway, probably not. Generally you only hit the point of best efficiency during acceleration or perhaps climbing very steep hills.

Here's what is called a brake specific fuel consumption map for a 1.9L Saturn engine.




The red curve at the top of the colored section is the max torque curve. The curved blue lines are lines of constant power (use right y-axis). The lines delineating the regions of different colors are lines of constant brake specific fuel consumption - i.e. how many grams of fuel are required per kW*hr of energy production. You can also think of them as lines of constant thermal efficiency. The engine can operate at any point underneath the torque curve, given the right conditions to make it happen. The point of best efficiency is going to be somewhere near the center of the darkest red region.

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Ed O'Malley
www.VeloVetta.com
Founder of VeloVetta Cycling Shoes
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Yup...my Acura MDX is a 9 speed automatic. Seems as though the auto industry is heading in this direction...so the original question may be in the process of being addressed...more gears is "better"!

Wait....and here are I thought that Murphy's Law was he 2 horsepower human. Did you get old and downgraded to 1/2 hp?

Oh come on Ed like you know anything about engines or something.

The old Macks I used to drive only had 5 speeds. Great engine with a wonderful torque range. Didn't have to shift all the time. One of my neighbors has a newer Western Star with only 8 gears in it. Doesn't sound like he was impressed with it though because the torque range is too narrow on the engine.

Cars are overmotorized, bacause they are an emotional product. To get from a to b, 15 or 20 hp would be sufficient. But then more gears would be very helpful indeed.

Look at trucks. They are not overmotorized, but rather economic, and have much less hp per kg compared to cars. Because of that they have more gears.

Modern autos are up to 8 speed now...