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MIT Team Creates Shock That Recharges Your Car
An anonymous reader writes "If you had a GenShock, you may not mind those potholes in the road any longer because this new prototype shock actually harvests energy from bumps in the road to save on fuel. A team of students at MIT have invented a shock absorber that harnesses energy from small bumps in the road, generating electricity while it smooths the ride more effectively than conventional shocks. Senior Shakeel Avadhany and his teammates say they can produce up to a 10 percent improvement in overall vehicle fuel efficiency by using the regenerative shock absorbers. They also already have a lot of interest in their design, specifically the company that builds Humvees for the army are already planning to install them in its next version of the Humvee."
I take it you don't live in a cold weather climate or in a large city. Snow/ice + salt + plows = pot holes. Large cities have notoriously bad roads, it's too hard to repair them with so much traffic.
And it's not just bumpy roads that shocks help with. Every time you turn a corner the shocks are used to keep the car stable.
Personally, I think it's a brilliant idea. The easiest way to become more efficient is to turn the wasted energy into something useful.
"Action without philosophy is a lethal weapon; philosophy without action is worthless."
Bose admitted to pre-tuning their magnetic suspension specifically for each demonstrated feat. Changing one without changing the other would destroy the so-called "advantage".
Also, the system is hideously expensive, impractical and performs poorly compared to conventional equipment. A bit like every single other crappy product Bose has ever made, really.
Eat the rich.
Generally speaking you have more handling and fuel performance issues with having too *little* air in the tires. 27% of cars, according to the US DOT, have at least one underinflated tire.
http://www.dot.gov/affairs/nhtsa4601.htm
So what's the problem? Well, as you say, you get a harsher ride from an overinflated tire, but you get far many more problems with underinflation, which is probably far more common. Some of those problems include poor braking, slow steering, poor handling/road grip, and worse fuel economy... worse than can be made up by funky new regenerative shocks.
http://www.straightdope.com/columns/read/225/could-we-conserve-gasoline-by-putting-more-air-in-our-tires
I know lots of people made fun of Barack Obama during the Presidential campaign for his plea to check the tire pressures, but the reality is that drivers the world over could save millions of gallons of oil annually by simply keeping tires inflated properly. In cold climates this also means double checking the pressures when the outside temperature drops by 10 degrees.
Better to pump up the tires than not.
This post brought to you by your friendly neighborhood MBA.
At first glance this sounds like a good idea, but let's do the math.
Assume you're driving over an evenly and heavily potholed road, such that all four wheels are rising and falling four inches four times a second. That's a very generous assumption. And assume a rather pudgy 400 pounds of unsprung weight. To move that stuff 1.33 feet per second takes 900 ft-lbs.sec of power, about 1.5 horsepower. But you don't want to absorb all that power or the whole point of a flexible suspension is lost. Let's guess we want a Q-factor of about 3, that is, we absorb 1/3 of the energy per cycle. We're down to 0.5 horsepower, and that is under optimally bumpy conditions. And small random jiggles are hard to capture as electricity. Overall it does not seem to be worth harvesting.
If one is going to be driving on such surfaces a lot, it makes a whole lot more sense to fit the vehicle with larger flotation-type tires. Those tend to flex and span potholes, so the car and passengers don't jiggle at all.
(My father in law drove an 18 wheeler at one point).
So much of the 18 wheeler relies on moving air around pneumatically. The two basic forces in an 18 wheeler are positive pressure and vacuum. If you do away with the engine (or otherwise turn it off), you lose the boost/vacuum economy which makes those accessories work. While you could probably come up with some weird stopgap - they already use compressed air tanks as a backup - the retrofit to make it work with existing trailers would far outweigh the savings from a hybrid cab. Add to this that the truckers rent or own their own cabs as part of the business and there's little incentive for anyone to innovate or upgrade in a direction that would hurt their prospects for hauling.
Some forms of active suspension mean your car can have suspension matched to the weight of the car and its loads, you can have suspension matched to an empty car when its empty and matched to a fully laden car when its loaded up instead of having a compromise setup thats matched to neither laden or unladen. How many times have you seen a car where the rear is low because of the load of the passengers or the trailer its towing?
Other forms of active suspension means you can have soft suspension when you're driving in a straight line and only have stiffer suspension when you are cornering, the result is that you can make your "cornering" rates higher performance without sacrificing your "straight line" comfort.
Other forms again allow the car to stiffen is anti roll bars and to corner flat.
Citroen has produced suspension systems that do all of the above on production cars, their first systems (on the DS and later cars) only self levelled, later their Hydractive system on the XM had "hard" and "soft" settings too eventually the Activa system on the Xantia added active anti roll bars too.
Formula One cars used active suspension, it could vary suspension rates, ride heights and anti-roll stiffness, it gave the cars that had it a competitive advantage over those that didn't but was eventually banned.
In fact it will have a net negative effect on your gas mileage. If you put an electric (re)generator on a shock absorber, and hook it up to an electrical load (to capture the energy) then the generator will fight back when the shock absorber tries to react to the pothole. In effect, it will directly reduce the "shock absorbing" capability of the shock absorber, giving you both a rougher ride and slowing your car down more.
Since there are always losses in energy transfer, the amount you "recover" will always be less than the amount put into the system by you having to use more gas as a result of the harder bump.
It's called Back EMF, basic high school physics.
Beware the Wikipedia article on Back EMF, it loosely covers the concept but the article links to a "serious" entry about a perpetual motion machine called Perepiteia, which also would violate the laws of thermodynamics.
The "inventor" "doesn't understand how it works" and yet worked "8-12 hour days on it" making a transformer 7000% efficient!
Sigh..
Bavarian Purity Law of Rice Krispie Squares: Rice Krispies, Marshmallows, Butter, Vanilla.