# Automotive How much magnetic power is needed to stop a slow car.

1. May 25, 2012

### Lancer2death

Hello everyone, I need to figure out how much magnetic force is required to stop a car going 15 mph, weighing 5071 lbs, at an angular velocity of 1rad/s, with a force of 30,848 newton’s, and accelerating at13.41 m/s^2. In addition, what would the size(dimensions) of this magnet have to be? Meaning, what magnet or contraption would have enough magnetic force to stop this car with characteristics I mentioned above.

2. May 25, 2012

### Danger

Welcome to PF, Lancer.
Your question lacks an awful lot of specifications, starting with what sort of organization you have in mind. For my bucks, I'd go with magnetic calipers acting upon a standard rotor. As for power requirements, I have no idea.

3. May 25, 2012

### Lancer2death

I don't know what to suggest...can you give me examples of specifications for power requirements?

4. May 26, 2012

### Danger

I just saw your post in the main forum, and see what you had in mind. (By the way, you shouldn't duplicate these.) I can't foresee any way in which this could work, but I'm not an expert.

5. May 26, 2012

### Lancer2death

:-( sigh okay thanks. U r more of an export than me.

6. May 26, 2012

### Danger

Sorry... I hate to discourage anyone, but magnetism acts over a very short distance. You would need an electromagnet, rather than a permanent one, in your design (to enable deactivation for stuff like parking and towing). I don't know that any system could meet the power requirement. Your magnet would have to lie somewhere between an MRI scanner and a cyclotron. It would probably be heavier than the car itself, and your car's engine wouldn't be able to drive a generator large enough to power it.

7. May 27, 2012

### Lancer2death

Allright I understand more now. Thank you! U all r very helpful. Im less bummed out now that I know why it wont work.

8. May 27, 2012

### Danger

That's the good side of learning stuff. Don't let this instance discourage you from continuing to have neat ideas. There's no such thing as a bad idea, as long as it isn't pursued beyond the point of reason. Yours, for instance, is a very good one in principle; it just won't work magnetically. Lots of auto makers these days are incorporating anti-collision systems into their products. They're active rather than passive, though. Ultrasonic or radar sensors cause the onboard computer to electromechanically apply the brakes. It's taken them decades and millions of dollars to develop those, so don't feel badly that yours didn't make it off the launching pad the first time.

9. May 27, 2012

### Lancer2death

Oh wow that's so cool! I didn't know that. Well thank u. I will definitely continue to come up with great ideas now that I have found an awsome website

10. May 27, 2012

### Danger

I look forward to seeing them.

11. Jun 8, 2012

### kazx9r

I think you mean eddy brake retarder, I might buy one for my own project, a 2200Nm with 4-550kw costs around $2500, shipping and customs another$800, weight around 400lb, enough to stop a bus.

12. Jun 8, 2012

### Danger

I didn't, actually, but it's a great system. Unfortunately, I don't know anything about the technical side of that. My thought was to use very powerful electromagnets rather than hydraulic cylinders to force standard brake caliper pucks against the rotor.