The Ergosphere
Thursday, September 30, 2004
 

Wasting energy... with useless textbooks

I promise that this is not going to become an education blog, but I had to point to this Richard Feynman story wherein he recounts his one time reviewing mathematics textbooks.  (Hat tip:  a commenter Jeff_H at joannejacobs.com.)

Textbooks which are confusing, obfuscatory or just plain wrong are more than just a waste of money; they are a crime against the taxpayers, schoolchildren and progress itself. 
Wednesday, September 29, 2004
 

Kill the hydramatic

Q:  How do you take a car that gets 26 MPG going up a hill and turn it into a car that gets 6 MPG?

A:  Make it send all its power through a nice, lossy torque converter.

Yes, I'm serious.  I've got a car with a bunch of nice features, including a highly efficient turbodiesel engine and a trip computer with a not-too-inaccurate MPG meter... and an automatic transmission.  (Wasn't available any other way this model year.)

What's wrong with that? For efficiency, plenty. A torque converter is a way to amplify torque at the expense of power; the slip between the two sides causes fluid to be slung around inside like an O-ring being rolled down a rod, and the stator turns some of that circulating motion into extra torque. This is good for getting away from a standstill, but a 3:1 torque multiplication at stall is still... 0% mechanical efficiency. At low speeds, it's easy for 75% or more of the input power to be lost as heat in the torque converter.

(For those who are lost here, consider the situation of a car standing still on a hill, being pulled by the engine just enough to stop it from sliding backwards.  You could accomplish the same goal by putting a brick behind a tire and shutting the engine off, but instead the engine is spinning faster than normal and being loaded more heavily than a normal idle just to keep the car in the same place.  All of this power and fuel is being wasted in the slippage of the hydraulic torque converter.)

75% losses means using 4x the fuel that is ideally required for the job.  Modern transmissions have "bypass" clutches which lock their torque converters at higher speeds and eliminate the slip losses, but in local and stop-and-go traffic this isn't possible.

Toyota has a better way, in the Prius at least.  The Prius has an automatic transmission, but no torque converter.  Instead, it has a gear arrangement such that the slip between the engine and final drive moves, not fluid, but a motor/generator.  The energy that would be lost in a conventional automatic is turned into electricity instead, and that electricity either feeds a second motor (to add torque much more efficiently than hydraulic fluid) or is stored in a battery.  A little bit of slip at the engine can maintain a lot of stall torque at the second motor, making the whole affair much more efficient in low speed, stop-and-go driving.  And the electric motors used in cars, unlike torque converters, can create torque at zero speed with a minimum of power being wasted.

Yes, two motor/generators are more expensive than some brazed sheet metal formed into a doughnut-shaped chamber filled with type F.  But ask yourself this:  how much are you willing to spend to cut the number of madrassas training the next generation of Mohammed Attas? 
Friday, September 17, 2004
 

A sad day

Upon my return to the world of blogs, I began to check my must-read list of other bloggers.  At the top is USS Clueless.  To my dismay, I found a declaration from Steven Den Beste that he has stopped writing.

Not that he and I agree all the time; far from it.  He is very tired of certain topics near and dear to my heart, and this shows in the rigor (or lack thereof) with which he treats them.  But when he's good, he's very, very good and it is a crying shame that he's no longer getting the emotional return on his investment of time.  The whole world is poorer. 

Talk largely about energy and work, but also politics and other random thoughts


Mail Engineer-Poet

(If you're mailing a question, is it already in the FAQ?)

Important links

The FAQ
Glossary
The Reference Library

Blogchild of

Armed and Dangerous

Blogparent of

R-Squared




The best prospect for our energy future:
Flibe Energy

ARCHIVES
January 1990 / February 2004 / March 2004 / June 2004 / July 2004 / August 2004 / September 2004 / October 2004 / November 2004 / December 2004 / January 2005 / February 2005 / March 2005 / April 2005 / May 2005 / June 2005 / July 2005 / August 2005 / September 2005 / October 2005 / November 2005 / December 2005 / January 2006 / February 2006 / March 2006 / April 2006 / May 2006 / June 2006 / July 2006 / August 2006 / September 2006 / October 2006 / November 2006 / December 2006 / January 2007 / February 2007 / March 2007 / April 2007 / December 2007 / January 2008 / May 2008 / June 2008 / August 2008 / October 2008 / November 2008 / December 2008 / February 2009 / March 2009 / April 2009 / May 2009 / June 2009 / July 2009 / August 2009 / September 2009 / October 2009 / November 2009 / December 2009 / January 2010 / April 2010 / May 2010 / June 2010 / July 2010 / August 2010 / September 2010 / October 2010 / November 2010 / December 2010 / January 2011 / February 2011 / March 2011 / April 2011 / May 2011 / July 2011 / August 2011 / September 2011 / October 2011 / April 2013 / November 2013 / December 2013 / January 2014 / February 2014 / March 2014 / April 2014 / July 2014 / August 2014 / September 2014 / October 2014 / November 2014 / February 2015 / April 2015 / October 2015 / March 2016 / April 2016 / May 2016 / June 2016 / July 2016 / November 2016 / December 2016 / February 2017 / May 2017 / June 2017 / September 2017 /


Powered by Blogger

RSS feed

Visits since 2006/05/11: