Possible senior design project ideas - Possible?

[xBa380]

We started our senior design for mechanical engineering and looking into some thoughts/ideas... I plan to talk with the professors soon about them (one is an advanced bearing analysis guy, so he would probably know for sure... But I thought I would self-moderate myself if the idea is too wacky!).

I have three automotive related ideas that will be thrown into our group "pool" and later pick the idea the professors and us like best. I just wondered if my ideas have any chance of working, if any of you have input.

First,

I was thinking of making a magnetic braking system to replace the rear disk/drums brakes... Replace the rotor with a copper alloy type rotor and the brake piston assembly would push rare earth magnets over the fin, causing braking force. Magnets cannot stop the car, so front brakes would still be required. This would reduce wear/tear and be maintenance free other than the fluid (theoretically). Would work much like magnetic braking systems on many amusement park rides which use permanent magnets on the ride car and the fins on the track. Completely power free. The main challenge would be designing the caliper system to fit inside the wheel.

Secondly,

Doing either magnetic or pneumatic bearings to replace the ball bearings in the wheels. Air bearings I have seen used in CT medical machines and it was fascinating how the rotors just float with basically no friction. You can spin the 1,000lb rotor on Friday and come back Monday and it still was moving. Was really cool. Wondering if we could do this somehow with car bearings to reduce friction and improve MPG and all that. Or if its really not even worth going for... Same thing with magnetic... Sort of like mag-lev trains and such. If that would even be possible.

Other ideas thrown around (non automotive related) include sanitation of escalator handrails using UV light or cleansers/heater system... Would be able to be retrofitted on existing equipment without replacing entire thing... Sort of a medical/health thing for malls and busy places when people want cleaner things to touch.

Comments/suggestions appreciated! Just going through some ideas for now.

Thanks!

 

[MolaKule]

You never did say if this was a paper study or an actual build/design situation.

First idea: You are still going to have to determine heat dissipation issues. Heat and eddy currents destroy PMs. Economics may kill this one.

Second idea. Consider that the forces on your example are primarily single axis. In an auto, you have complex, three dimension forces.

Suggestion: Develop an apparatus to determine oil temperatures into and out of a journal bearing under various loads. Propose methods to improve cooling in the bearing, including bearing geometries as factors.

Consider the total system requirements and then decompose down to the component level.

 

[Tegger]

Originally Posted By: MolaKule
Second idea. Consider that the forces on your example are primarily single axis. In an auto, you have complex, three dimension forces.

Plus extremely high transient-loadings that I think would easily overpower any air or mag forces.

 

[xBa380]

Thanks for the info!

And this project is design/prototype situation. We could stick to 3D modeling alone if need be due to cost, but generally a prototype of some sort. This semester the calculations and planning all need to be complete and next semester is the build/testing and everything.

I thought the bearing issue would be a problem with the forces and everything. The magnetic braking idea I still like, although like Molekule has said, heat will be an issue... But since the magnet will see the most heat at high speed situations, cooling veins in the "rotor" would help cool. An open wheel design may be required or the addition of a heatsink of some sort.

Basically, the rotor would be made of copper or copper alloy (or at least part of it that will see the magnet) and the caliper would move into position when braking is applied dynamically (computer would adjust the amount the magnet moves over the rotor based on speed and pedal pressure) to avoid over/under braking.

 

[MolaKule]

One could also consider a Non-Newtonian fluid based on a "magneto-rheological" ferrofluid, whereby a disk rotates in this fluid and the viscosity changes under the influence of a magnetic field.

Either way you examine it, you're still going to have dissipate large amounts of energy as heat.

For example, for a 4000kg SUV, the braking energy for one wheel is approx. 385,000 Joules.

 

[The_Jeff]

Would this magnet brake be passive or electronically controlled?

I can't imagine a magnet repelling a fin that it wouldn't shortly be attracting as the thing turns.

Or am I thinking about this oddly?

What will it give off as it slows down the car? Heat? Noise? Electricity? Wear?

 

[Shannow]

eljefino, a conductor moving in a magnetic field produces currents...in generators, these are carefully controlled to make electricity, but you can purposely "uncontrol" them to create eddy currents, which create a back pushing effect that resists relative motion.

e.g.

http://www.magnadrive.com/

 

[xBa380]

I think we are going ahead with the eddy current brake system, but our main challenge is heat. Trying to find information online about the heat created with eddy currents on such a system... Hard to come by, which I did not expect. I am probably searching the wrong thing, maybe.

We plan to create a heat sink (most likely the wheel itself) to disperse excess heat. But first, we have to make sure that the heat created will not literally melt or damage anything first.

 

[jrustles]

Originally Posted By: xBa380
I think we are going ahead with the eddy current brake system, but our main challenge is heat. Trying to find information online about the heat created with eddy currents on such a system... Hard to come by, which I did not expect. I am probably searching the wrong thing, maybe.

We plan to create a heat sink (most likely the wheel itself) to disperse excess heat. But first, we have to make sure that the heat created will not literally melt or damage anything first.




Eddy current braking - interesting but obscure.
Imagine having to input electrical energy only to waste it as heat, on top of wasting the inertia of the vehicle as more heat. They're really only used in places where friction braking is undesirable, not for efficiency.

But this is a project, and the process of building the apparatus and programming the logic is really cool stuff.

Maybe a solution to your heat quandary lies in generating electricity from the wheels inertia, and feeding it back into your frictionless brake resulting in somewhat of a hybrid generator/eddy current brake?

 

[xBa380]

Well we are not using the powered eddy current system, but a non-powered system. The only moving/powered component will be the caliper to position the magnetic "caliper" over the brake disk (aluminum/copper).

The same type of system used on most modern rollercoasters, freefall towers, etc... They generally just line up fins and attach rare earth magnets on the train. No power is required, completely fail-safe. As the magnet (on the train) passes over the copper alloy fins, the eddy current is produced and creates a braking force (and heat). No power is needed.

Much like this:

http://www.youtube.com/watch?v=LbN3NU4hIZg

Brakes start around the 50second mark after the drop.

Stops the train from 120mph down to a near crawl in a few hundred feet. We want to apply this same thing but to the rear braking system of a car.

 

[jrustles]

Ah, so a passive type, but using a rotor instead of the track on the roller coaster? So the heat issue becomes dissipating the heat on the relatively small rotor as opposed to the entire length of the 'stator' track.

What about the caliper of magnets, will they be opposed to each other?

 

[xBa380]

Yes, passive. And yes, the heat buildup on the rotor becomes the concern... So I am trying to find some equations or theory on the heat built up.

As far as the caliper of magnets, we basically were going to make a "U" channel lined with the neo-magnets. Not sure if they are "N/S" dependent, but that will come with the research. But if one direction has to be chosen, it would be for forward motion only.

 

[jrustles]

alright I see what you're saying. I'd go with a larger wheel rather than a smaller one, to fit more poles and create a larger dissipation surface. If you use some sort of CNC machined rotor, you can build in heatsink blades? Fill us in on your design!

 

[Shannow]

A friction brake disc or an eddy current brake disk have the same amount of heat to remove...

 

[xBa380]

Would they?

Our professor appeared concerned about our idea just because of the heat. If it would be the same as a friction brake (given the rotor is the same) that would be great. We plan to keep the rotor itself the same diameter, just replace it with aluminum/copper. If possible, we would design the rotor to have cooling veins inside of it, if time allows for us.

I found some equations for the heat, but it does not exactly apply towards our system. So I am still on the lookout to figure out exactly how hot the rotor will get, lets say from 70mph to a stop with a 3,000lb vehicle (only estimating 50% of braking for the rear although we know it is less than that), and divided between each wheel.

 

[jrustles]

Originally Posted By: Shannow
A friction brake disc or an eddy current brake disk have the same amount of heat to remove...



This public service announcement brought to you by The Conservation of Energy.

I now realize that xB's project is supposed to effectively demonstrate Lenz's law? Or are you actually applying this to an car?

Lenz's law and electromagnetics in general are absolutely fascinating. Never paid attention to Lenz's law until now, and I'm all hyped up about it lol

xB, if you keep the inertial mass low you shouldn't be dealing with a lot of energy resulting in minimal heat.

 

[xBa380]

Well our plan is to design a system to be used on a car. So we would machine a rotor, mount it to a test rig of some sort, spin it up to speed and apply the "caliper" to demonstrate how it works as a prototype. We would have to design the caliper system as well and how it would apply exactly. We are looking to electrically actuate it into position.

But we still have to do all the calculations and prove it can work in an automotive situation, even if we are not directly bolting it on a vehicle.

 

[Shannow]

Originally Posted By: xBa380
Our professor appeared concerned about our idea just because of the heat. If it would be the same as a friction brake (given the rotor is the same) that would be great. We plan to keep the rotor itself the same diameter, just replace it with aluminum/copper. If possible, we would design the rotor to have cooling veins inside of it, if time allows for us.


Be careful with that design if you want a good brake.

Do some research on transformers and electric motors, and see what they do to reduce "iron losses".

stacked thin plates are used to reduce the eddy current intensity (and thus the heat losses) in electromagnetic machinery...was thinking it through yesterday, and a "ventilated" disk would be like two seperated, stacked plates, i.e. less effective than a similar thickness of metal (I can't do the math, sorry)

 

[Shannow]

http://www.magnadrive.com/magna_asd.html