Magnetized Wheel (A Theory Thread)

[safe]

Magnetized Wheel (A Theory Thread)

This is a "Theory Thread" so if you are looking for an "answer" to some practical short term question you need to go to another thread.

The idea here is to create a bicycle rim that is lightweight... close to the weight of a standard rim... and yet is given a magnetized condition so that a coil placed near the rim could recapture the cyclical energy during regen. In fact... one might even consider using the magnetized wheel as a brake in place of the standard braking systems.

These days there are some rather exotic materials being created that might be able to produce the magnetic properties desired. If just the right material could be discovered that could provide the necessary material strength for a rim while also giving it magnetism then you have the basis for all of this.

The idea is to make a sort of "super pancake" hub motor where the hub is stretched all the way out to the rim. It's NOT going to be a standard motor... and the idea might not even work very well... but that's why we have a "Theory Thread" so that we might do the thought experiment to consider what could be...

 

[fechter]

Magnets are not particularly lightweight.

The main problem I see is the wheel would tend to pick up bits of magnetic trash from the road, like microscopic pieces of rust. This stuff covered the magnet ring on my Zappy after 100 miles or so.

If you didn't want to recover the energy, you could use a really strong fixed magnet against an aluminum rim to make eddy current braking. If the aluminum rim is in a strong magnetic field oriented 90 deg to the direction of movement, it will act like a generator with a short circuit. By retracting the magnets, you could control the braking force.

 

[Ypedal]

http://www.endless-sphere.com/forums/viewtopic.php?f=2&t=4263&start=0

 

[TylerDurden]

Dealing with drunks is like dealing with alzheimer's victims: every day there's a new and profound discovery that's not new and (obviously) not profound.

If you have the whole thing figured out already on a spreadsheet it's not that hard to do, but if you want I could probably do it for you and give you a spreadsheet that would show the resuts. Not tonight however because I'm going out to the local bar and tomorrow I'll be sayng "why did I drink like that?" for the hundredth time... :lol: (but it's always fun and I like to have a good time)

http://www.endless-sphere.com/forums/viewtopic.php?f=2&t=416&p=5668&#p5668

 

[ebinary]

Magnets are not particularly lightweight.

The main problem I see is the wheel would tend to pick up bits of magnetic trash from the road, like microscopic pieces of rust. This stuff covered the magnet ring on my Zappy after 100 miles or so.

If you didn't want to recover the energy, you could use a really strong fixed magnet against an aluminum rim to make eddy current braking. If the aluminum rim is in a strong magnetic field oriented 90 deg to the direction of movement, it will act like a generator with a short circuit. By retracting the magnets, you could control the braking force.

Does this really work on aluminum? I didn't know non-ferros metals responded to a magnetic field.

 

[safe]

The main problem I see is the wheel would tend to pick up bits of magnetic trash from the road, like microscopic pieces of rust.

That's a very good point.

Maybe the magnetic field needs to be induced? (temporary)

You could pass the current down the spokes and into small coils embedded into the rim. If you got all the timing right you could use the energy of regen to build up the coil energy making a sort of feedback loop. You would need to bootstrap the starting magnetism to start getting regen energy, but it should be possible to recycle it. This way you get braking and regen at the same time.

These guys are experimenting with regen as braking:

http://www.greencarcongress.com/2008/08/lithium-technol.html#more

A normal electric motor creates power all around the motor. In this idea you would have a single focused point where power is "exchanged". It would be like a single pole motor...

 

[vanilla ice]

F1'er racing is going regen next season. Should be the sharpest, most well funded race teams working on it there.
http://www.motorauthority.com/news/motorsport/brake-energy-regeneration-in-f1-by-2009/

How much electricity does an eddy current setup use? Some city busses use that.

 

[safe]

Except that in the article they talk about how they plan to use a flywheel rather than anything electrical to recapture the energy. I like the fact that F1 racing is mandating such things, but it does apply to the discussion of a magnetic wheel.

What is a magnet?

"Current (I) flowing through a wire produces a magnetic field (B) around the wire. The field is oriented according to the right-hand rule."

http://en.wikipedia.org/wiki/Electromagnet

Something like a Faraday disk?

http://en.wikipedia.org/wiki/Electrical_generator

"An electric generator or electric motor that uses field coils rather than permanent magnets will require a current flow to be present in the field coils for the device to be able to work. If the field coils are not powered, the rotor in a generator can spin without producing any usable electrical energy, while the rotor of a motor may not spin at all. Very large power station generators often utilize a separate smaller generator to excite the field coils of the larger."

So braking force would be triggered by power being sent from the brake lever to the coils in the wheel. When the coils have magnetism this causes a resistive force (braking) and produces regen. You could make the wheels out of a material that would also conduct the electricity well... hopefully not copper... something that could benefit the structural strength of the wheel as well as be a creator of magnetism. Steel is the obvious choice since it's cheap and it conducts electricity pretty well. (not as good as copper, but this idea is about getting something for next to nothing)

 

[Fumesucker]

Try dropping a neodymium magnet down a copper or aluminum tube that it just fits in, you'll get a very good example of eddy current braking.

Ever heard of a "Halbach array"?

http://en.wikipedia.org/wiki/Halbach_array

 

[safe]

Fechter already pointed out the "fatal" flaw to permanent magnets in that they pick up crap off the road too easily. In an electric motor you can keep things fairly clean, but on the road you would be picking up every nail you road past.

I think that we need to be thinking in terms of an induced magnetic field. The question becomes more about the design of the rim... how might it be built... more than anything else.

Exotic composite materials like carbon fiber might be an area to think about too, rather than steel which is heavy. (though there are a lot of steel rims in existence)

One might think:

"How can I get some regen without adding any significant weight to the rim?"

...that's the kind of thinking I'm focusing on. Anyone can strap on 15-20 lbs as a hub motor and get a regen generator, but you've effectively limited the usefulness of the bike when you do something like that because the unsprung weight is excessive.

 

[vanilla ice]

Except that in the article they talk about how they plan to use a flywheel rather than anything electrical to recapture the energy.

I didn't read it, was the first google result. Mechanical is one of two ways the teams can choose to go, the other is electrical. Given their big budgets, ultracaps is prolly what they'd want to try. But those flywheels could be good for big trucks and even cars if the tech trickles. 09 rules also allow for harnessing exhaust heat. That could be neat too.

We've got an eddy current brake at work. Way nicer than making dust, and it wont wear or heat up like the conventional brake setup does.

 

[safe]

Math, Math, Math...

It's getting late and I'm getting tired, but here's a brain teaser for anyone out there who has an energetic mind.

What are the equations for CREATING a magnetic field verses being able to CAPTURE current based on a moving coil?

Obviously the mechanical energy of the wheel is what pushes the electrified coil (and magnetic field) and that's what actually produces the regen energy, but what are the formulas?

The rough outline needs to be something like:

FinalOutputEnergy =

MechanicalEnergy * (CapturedElectricalEnergy - MagneticFieldCreationEnergy)

...anyone who has experience with generators would know this one.

 

[Link]

I'm not wasting my battery by dumping it into some coils to waste the kinetic energy stored in my moving self, and I don't see why I should add more weight to my bike (the rim, no less), by sticking a load of magnets on it.

It's not going to be as effective as a mechanical brake, especially at slower speeds. It adds weight. It adds cost. Motor braking saves brake pads, too, and can recapture a bit of that energy without costing much or anything extra. I enjoy hypothetical speculation on stuff that might come in handy, but why should I use a "magnetized wheel" at all?

 

[safe]

...I don't see why I should add more weight to my bike (the rim, no less), by sticking a load of magnets on it.

You haven't been reading very closely.

One: Magnets have been rejected for what is now two reasons: First that they would collect street junk (nails, etc) and second they weigh too much.

Two: The idea here is to make a rim that weighs the same weight as a standard rim, but has some embedded coils. (possibly in some sort of carbon fiber like material)

And as a "third point" let me remind you that this is a "Theory Thread". Youthful impatience does not mix well with theories because they require delayed satisfaction. We think and learn as we go... pushing for a quick answer is not the point.

 

[Link]

I read closely, but I guess I didn't word what I wrote clearly enough; you didn't answer my question. I don't care if it costs $10 and is lighter than a normal rim, why should I do it? What does it have other sorts of braking?

 

[safe]

We've got an eddy current brake at work. Way nicer than making dust, and it wont wear or heat up like the conventional brake setup does.

Very interesting...

http://en.wikipedia.org/wiki/Eddy_current_brake

Circular eddy current brake

"Electromagnetic brakes are similar to electrical motors; non-ferromagnetic metal discs (rotors) are connected to a rotating coil, and a magnetic field between the rotor and the coil creates a resistance used to generate electricity or heat. When electromagnets are used, control of the braking action is made possible by varying the strength of the magnetic field. A braking force is possible when electric current is passed through the electromagnets. The movement of the metal through the magnetic field of the electromagnets creates eddy currents in the discs. These eddy currents generate an opposing magnetic field, which then resists the rotation of the discs, providing braking force. The net result is to convert the motion of the rotors into heat in the rotors."

 

[safe]

http://en.wikipedia.org/wiki/Electromagnetic_induction

"Figure 8: Faraday's disc electric generator. The disc rotates with angular rate ω, sweeping the conducting radius circularly in the static magnetic field B. The magnetic Lorentz force v × B drives the current along the conducting radius to the conducting rim, and from there the circuit completes through the lower brush and the axle supporting the disc. Thus, current is generated from mechanical motion."

I keep searching the internet for some kind of online calculator where I could make an approximation without getting knee deep in the math. So far I haven't found anything... but the idea is simple enough... try to figure an approximation of how much braking force you can create with a bicycle wheel and how much regen you get as well all through the induction of magnetic fields rather than permanent magnets.

The math on this is going to be pretty heavy I suspect...

 

[safe]

This tool looks like it might have what it would take:

http://www.emfcalculator.com/emfcalculator/SimpleEmfCalculator.aspx

 

[Link]

It seems like you might have missed that last post (as you were in the middle of writing another and it's the last one on the first page), so here it is again:

I read closely, but I guess I didn't word what I wrote clearly enough; you didn't answer my question. I don't care if it costs $10 and is lighter than a normal rim, why should I do it? What does it have other sorts of braking?

 

[safe]

We here (collectively) have done a pretty good job modeling the electric motor because the math on it is relatively easy. What it would take to model a magnetized wheel is going to be similiar to an electric motor only you don't get to start with the "derived" and "simplified" equations and would essentially be rebuilding a motor from the ground up. You would have to model the magnetic field created by the coils and then figure (based on the gap between the coil on the wheel and a coil on the fork) the amount of induced current you would get. Ultimately you would arrive at a simulation where you could begin to be able to figure out questions like how much braking force you could realistically produce as well as how much regen you could capture... assuming you can even capture a "net positive" of energy. I know from reading about electric trains that below a certain speed the losses from the magnetic field creation EXCEEDS the gains received from the inductance.

The one thing we can say is that you WILL still need mechanical brakes in addition to the magnetic wheel brake... this is because below a certain speed the magnetic brake actually needs more current than it makes.

 

[Link]

*bangs head hard enough on desk to knock self out*

Zzzzzz...

 

[safe]

...why should I do it? What does it have over other sorts of braking?

The reasons are the same reasons that F1 racing is pursuing it. They have been able to recapture about 15% of the energy through regen in train implementations. This is holding true pretty much everywhere from what I've read. By doing about 75% of your braking with an induced magnetized wheel you can reduce your braking demands and recover some energy. Where this idea makes sense over something like a hub motor is that the hub motor is heavy and has a constant backEMF. An induced magnetic field does not have a backEMF so the only time it does anything (act like a brake) is when you pull on the brake lever which would turn on the current to the coils causing a magnetic field.

Is 15% worth it?

Sure if you can do it without adding weight...

http://en.wikipedia.org/wiki/Formula_One_car

"Due to increasing environmental pressures from lobby groups and the like, many have brought into speculation the relevance of Formula 1 as an innovating force towards future technological advances (particularly those concerned with 'greener' cars). The FIA has been asked to consider how it can persuade the sport to moving down a more environmentally friendly path. Therefore, in addition to the above changes outlined for the 2009 season, teams will also be asked to construct a KERS (Kinetic Energy Recovery System) device, encompassing certain types of regenerative braking systems to be fitted to the cars in time for the 2009 season. The system aims to reduce the amount of kinetic energy converted to waste heat in braking, converting it instead to a useful form (such as electrical energy or energy in a flywheel) to be later fed back through the engine to create a power boost. Such technology is highly likely to become a staple in the design and construction of road cars within the next 10 to 15 years, with increasing fuel costs and environmental concerns. It is through these technological breakthroughs that Formula 1 is striving to not only be the peak of what is technically possible, but also a platform from which environmentally friendly solutions for future use may be obtained, in a similar way to the development of technologies that have improved performance and efficiency in ordinary vehicles in the past."

 

[Link]

It's called regen braking. It doesn't add any weight, and is already fairly common on the tinkerers' bikes. I also asked what it had over that...

 

[Fumesucker]

*bangs head hard enough on desk to knock self out*

Zzzzzz...

I figured out a long time ago that it is better for me just to avoid threads which bring me to the point you just reached.

Different people have very different ways of looking at things and there isn't anything you can do about that. Some personalities are very focused in the here and now and others are almost completely disconnected from everyday reality.

I've found Jungian typology to be very revealing of the way different people approach life, find out what your personality type is like and realize that not everyone sees things the same way you do.

http://www.humanmetrics.com/cgi-win/JTypes2.asp

According to Jungian typology there are sixteen different basic personality types and some of them mix less well than water and oil. I get the impression that you and safe are two of those that do not mix well.

 

[ebinary]

*bangs head hard enough on desk to knock self out*

Zzzzzz...

I'm not interested in the regen, but I'd be very interested if I could get any reasonable braking by simply mounting some Neodynium magnets to a 2nd set brake calipers, and just pull them close (but not touching) when I need to control my speed. According to what I've seen in this thread, thats possible with just a normal aluminum wheel (no magnets in the wheel). Its a huge advantage not to be constantly scraping down your rim and brake shoes. I have to sand the debris off my wheels every week, or I lose substaintial braking power.

I am actually adding a friction drag brake (front drum) to keep my winter speed to something manageable on a long, steep, icy hill. Freewheel speed is 52mph, and I already know one guy who is permanently messed up by a crash on this hill.

As far as the regen idea goes, it makes much more sense to me to either have a direct drive with a clutch rather than a freewheel, or a planetary hub with a clutch rather than a freewheel, to reclaim your energy. The weight cost can't be more than a pound, and you you get the best of all worlds.

Maybe one other approach would be to have the permanent magnets in a non-geared hub be retractable when freewheeling, to eliminate back emf.

I'm getting the impression that some folks like to rag on safe, but this thread has possible born some fruit even if the idea is flawed - so I'll thank him for bringing it up.