(ot) magnetic brakes

[alex h]

Here's an off topic Q. for you all...

Why do we still rely on Hydraulics to actuate our brakes?

I was a trying to work out if it was possible to use electromagnetic forces to apply the brake pads to the disc. With the added bonus of reduced friction when the brakes are released and would repel back to their starting point off the disc much much faster than the standard arrangement.

Benefits would include; could use "calipers" which fully covered each side of the disc as you wouldn't need to have billions of pistons working....just a few magnets all fed by the same wire. Less maintainence, fewer moving parts and no fluid to change. Reduced Friction as sighted above. Increased ability to dissipate heat as larger pads used and the calipers would have a larger surface area. Could you mount it inboard to save unsprung weight? http://www.mkivsupra.co.uk/iB_html/non-cgi/emoticons/rock.gif

Negatives could be, loss of heat transfer capability due to the lack of fluid (but it also stops fluid boiling becoming an issue). Weight of units? Modulation and feel of brake pedal?

But whilst I sit here and write this post I can't help thinking I've heard of a system which goes one step further than this and does away with pads...by using electromagnetic forces to slow the vehicle without touching anything. And that the system is used to charge the battery as well (so you wouldn't need an altenator? http://www.mkivsupra.co.uk/iB_html/non-cgi/emoticons/rock.gif )

Anyone else know anything about this, have any thoughts, comment or facts http://www.mkivsupra.co.uk/iB_html/non-cgi/emoticons/rock.gif

(apologies for any spelling mistakes...brain isn't quite upto speed yet http://www.mkivsupra.co.uk/iB_html/non-cgi/emoticons/smile.gif )

[alex h]

ooops should this have been in Chassis Tech? Sorry! http://www.mkivsupra.co.uk/iB_html/non-cgi/emoticons/smile.gif http://www.mkivsupra.co.uk/iB_html/non-cgi/emoticons/tounge.gif

[Martin F]

Quote[/b] (alex h @ Jan. 21 2004,08:56)]Modulation and feel of brake pedal?
I think that would be one of the keys to getting this right. i.e. how do you make the electromagnet progressive ? It can be done but wonder how it would feel compared to a traditional hydraulic system.

Also a big issue would be voltage and current regulation so that when your battery was growing flat that you still had good brakes. Again not an impossible problem to overcome but would need to be added to system.

I'm sure electromagnetic brakes already exist on industrial machines somewhere, just can't place them at the mo.

[alex h]

The new Beemer 7-series is running a 48V system now isn't it? This is the biggest power system on a car that I know of, but that mean the technology is there to power the things...I think.

[Martin F]

All cars will be running 48v eventually, its been in the wings for a while.

Just sprung to mind electromagnetic clutch on the AC compressor. Not quite a brake but similar.

[alex h]

This is not quite what I wanted but a start....Telma (http://www.telmainc.com/telma_htm/default.htm). And here (http://www.landspeed.com/030215.html) is the new challenge from the Yanks for Thrust SSC and its frictionless brakes.

[Nathan]

I personally feel that electromagnetic braking ie no brake pads whatsoever is an excellent idea. You could use the braking as a way of generating energy (like an alternator) rather than throwing it away as heat in conventional brakes. I'm sure Honda or someone has done this already. It uses electricity to get the thing going then charges the batteries back up (OK, with a fair bit of loss) when it slows down from the kinetic energy stored in the mass of the car. I think the idea is brilliant. No idea how to make it work (and 'feel' right on the pedal too) in a high performance application though. The weight of the whole thing could be an issue too. Some trains use them. After all, thats where the retarders for our rolling road come from...

[wez]

If you change the braking system to electrical you are essentially changing this to brake by wire where as the current system is mechanical and has less to go wrong.

I can see this being a very good idea, as Nathan says you could then re-use the energy but this would require an obscene amount of testing as the brakes are very important and if an electrical failure occured it could be fatal.

Its ok if the relay goes on your windscreen wipers or indicators but brakes i am not so sure.

http://www.mkivsupra.co.uk/iB_html/non-cgi/emoticons/buttrock.gif

[Nathan]

Good point Wez but if ?25,000,000 fighters can get by on fully fly-by-wire systems I'd personally feel happy driving a car that had a similar amount of backups upon backups. Quite a bit of testing would be needed I agree, but I'd never feel 'unsure' about driving the end product. Hell, I might as well never step into another plane again!

[alex h]

Consider also, on the reliability front, that Lotus are developing a electromagnetic/hydraulic system for thier camless engine...by utilising magnets to control the valves. That system will go through hell...more so than the electromagnetic brakes and it should be in a production car by 2008...well that's the idea anyway http://www.mkivsupra.co.uk/iB_html/non-cgi/emoticons/smile.gif It's not just Lotus developing it...but they are the leaders in this field at the moment.

[wez]

Quote[/b] (Nathan @ Jan. 21 2004,13:11)]Good point Wez but if ?25,000,000 fighters can get by on fully fly-by-wire systems I'd personally feel happy driving a car that had a similar amount of backups upon backups. Quite a bit of testing would be needed I agree, but I'd never feel 'unsure' about driving the end product. Hell, I might as well never step into another plane again!
Hey Nathan I was not knocking the idea just saying that it would need serious testing before any production company put it to use and as you say it would also require alot of backup.

I think they spend alot more money of fighter aircraft development than cars, could be wrong though.

http://www.mkivsupra.co.uk/iB_html/non-cgi/emoticons/cool.gif

[Nathan]

No you're dead right chap. Cost and weight are the two reasons why this isn't readily available yet, not because it can't be done or problems with the system going down and leaving you with no brakes at 200mph.

Cheers

[timwildman]

Quote[/b] (Nathan @ Jan. 21 2004,13:11)]Good point Wez but if ?25,000,000 fighters can get by on fully fly-by-wire systems I'd personally feel happy driving a car that had a similar amount of backups upon backups. Quite a bit of testing would be needed I agree, but I'd never feel 'unsure' about driving the end product. Hell, I might as well never step into another plane again!
Most Airbus planes use fly-by-wire. They have 7 computers that can each controll the plane, the software was designed by 2 totally independant companies. They still have cable controll on some flying controlls just incase.

I think a lot of new cars are starting to use electric accelerator pedals, Clutch etc.. so it can't be long. It costs less to make electric parts (genrally)and saves weight.

At the end of the day if the brakes fail you've got 15 odd air bags to save you http://www.mkivsupra.co.uk/iB_html/non-cgi/emoticons/rock.gif

[Chris Wilson]

I think there may already be a production car with steer by wire steering (no direct wheel to rack mechanical connection, if not it's not far off. makers are deperate for this, as it would put to bed steering coulmn ingress into the passenger comaprtment in an accident once and for all, and at the same time allow them to stop having to thread a coulmn through hot bits of exhaust and vice versa. NVH could also improve with a steer by wire system, and all sorts of active steer are then also available.

[Martin F]

Quote[/b] (timwildman @ Mar. 18 2004,22:33)]At the end of the day if the brakes fail you've got 15 odd air bags to save you ? http://www.mkivsupra.co.uk/iB_html/non-cgi/emoticons/rock.gif
Only any good if their ECU's don't fail.

http://www.mkivsupra.co.uk/iB_html/non-cgi/emoticons/tounge.gif

[timwildman]

I was reading on another web site that, the Facelift supra which has the ECTS has an electronic throttle? but with a cable backup. so it's getting there.



The engines on fly-by wire aircraft are not controled by the pilot. (apart form when they turn them on and off) The flight management computer does all that.

[alex h]

ECTS is on pre facelift.... I was under the impression that was the Traction control!

[Nathan]

LOL, you're sort of on the money there Tim. The VVT-i does have a 'semi' fly by wire system, in that there is still a cable from the throttle pedal to the throttle body, but it is connected to a pot which the ECU intercepts and then decides how much to turn the actual throttle plate. It's a kind of half and half system. In reality, what it means is that if the fly-by-wire system goes down, you can actually get up to 20% throttle form the last 20% of the pedal movement. The first 80% will only work via the ECU.

[Martin F]

That seems like a lot of hassle for not much gain. Wonder why Toyota went with that system ? In fact what advantage does it have ?

[Chris Wilson]

Probably helps tie in anti knock, abs and traction control systems.