Recent content by Randy Beikmann

That's why I said "...it is multi-stage." There is just no reason to list them separately in a chart. ;-)

Either 8.28 or 9.73 would be a reasonable gear reduction from motor to axle speed, but as you suspect, multiplying both is not. The top speed for electric motors is in the 12,000 rpm range, more or less, not 177,000! I suspect that those ratios might be overall ratios for different versions of...

Load transfer is not dependent on vehicle speed, only its deceleration rate. Having said that, since brake material (probably) grabs better at low speeds because there is negligible heating, the load transfer could be even more pronounced than at high speeds.

While people do call it "weight transfer", it is actually "load transfer." When you are braking, the traction forces act on the car at ground level straight rearward(lower than the car's center of gravity). That will rotate the car in pitch (nose down, tail up) until the vertical tire forces...

Jack, the example you showed here gave valuable insight to the user of your website, especially since it was applied to a specific situation. You used the concept of "power flow" through the driveline to simplify the problem of choosing gear ratios, using a systematic way to do it instead of...

If the question is whether power or torque is "a better indicator of acceleration", then I'm afraid there is no general answer. It depends on the full question/problem definition - there are always "if's" that will determine the answer. It's like when someone asks you, "What's the best car to...

That energy is conserved is indisputable, but where it goes depends on the situation. At low vehicle speeds (say 5 mph), your engine will not be able to run at maximum power Pmax, because if you put your right foot to the floor, the driving tires will spin until your engine goes to redline. At...

Here is a plot of what I was describing. The max power could produce the dashed orange line, and the available traction could produce the dashed blue line. In actuality, acceleration is limited to the lesser of the two (the gray solid line).

This is something I've thought through quite a bit over the years. What I realized is that you have to look at it from the standpoint of what limits the acceleration, and it depends on conditions. There are three common limitations: 1) Traction, 2) Power, and 3) Wheelstand. Here's the key: The...

To simplify this discussion, I would assert that Newton's laws and the laws of thermodynamics/energy are equally important. There's no reason to argue about which is more so here. To accelerate a car, there must be a force F at the tire patch to cause it, so that F=ma (neglecting drag). But...

One likely inaccuracy is your value for drag coefficient. I have a reference that gives the Cd for a 1960's Mustang notchback as 0.475, much to my chagrin (I had a 1969 Cougar that would have been about the same). For as nice as they looked, 1960's cars were, by and large, bricks being rammed...

You are exactly right. That is in fact the most fundamental definition of power.

Experts I've worked with have long considered John Heywood's book "Internal Combustion Engine Fundamentals" the bible for IC engines. I just happened to see that a 2nd edition came out this year.

For an Otto cycle, there is no work input. There is heat input (Q_h) from the fuel. Work and heat are thermodynamically different forms of energy. Taking the work of compression as W_c and the work of expansion as W_e the thermal efficiency is (W_e - W_c)/Q_h. In words, it is the net output...

If that's your goal then that sounds like a good plan. As I said, there are existing vacuum pumps meant to move air. And since you don't really care about the vacuum pressure, so much as flow, you might even be able to use an EGR pump, with a low-restriction breather leading into the other side...