Tuesday, January 8, 2008

How much for the Maglev?

I love the idea of Maglev technology. A couple weeks ago I decided to find out how it really worked and how much it cost - how much power does it take to keep a train full of people elevated? You can't just assume a "new technology" is better for everything. Yes Maglev reduces friction, but how much power does it cost? I wanted to understand how it compared to traditional wheeled trains. And then I had a thought about sticking some huge wheels on a train..

Let's make an assumption that a maglev train suffers frictional loss only from air resistance, and that a similar train using traditional wheels will experience the same air resistance. Let's assume that a wheeled train suffers an extra frictional loss due to wheel bearing friction, and that this loss is roughly proportional to its speed.

So, all things being equal, there should be an approximate top speed at which the more expensive maglev train pays for itself by outperforming the wheeled train. Lets guess that this speed is 100mph.

But I had to ask this question: What if you made the wheels 5 times as large? This reduces the bearing friction by 5 times. Does that mean that a wheeled train would outperform a maglev train up to 500mph?

Of course there are heaps of ignored factors here, but it's a valid thought experiment. Here's a really bad sketch for you. I have no idea what is ha.xinhua.

1 comment:

Anonymous said...

Maglev car bodies can be made *much* lighter than their rail-based counterparts. The bottom half of a rail-based car presents all sorts of aerodynamic drag (wheels, axles, brakes, pipes, etc) that are not present on a maglev. Early locomotive designs often featured larger wheels, but you have problems of decreased wheel strength and stability, increased weight and the size affects how sharp a curve the train can negotiate.

Maglev "track" is way more expensive to build, and dealing with disabled trains is more complicated than with standard rail.