Special Repelling Magnet Shoes

[physicsfrenzy]

Hello,

I am new to the forums, my name is Brandon. I have just recently graduated high school. I graduated from my physics class with a 97% for the year! yay!

But off to my question...

I have been thinking of a cool project that involved 4 neodymium magnets and using the repulsion force between them to act like a "spring" effect to make you able to jump and run at increased increments.

Here is how it works:

You have two magnets for each shoe. You contain the two magnets inside a non-magnetic material so the axis are lined perfectly underneath the shoe. I am not sure of the complete contraption yet but I was thinking if you used magnetic repulsion it should act like spring shoes, well... my theory anyways. Could this possibly work?

Thanks for the help. And hello again.

Brandon

 

[Waterfox]

I was thinking if you used magnetic repulsion it should act like spring shoes

Then why not just use springs? The only advantage I see is that springs may fail earlier due to wear.

 

[physicsfrenzy]

I just do not see springs being stronger than some magnetic repulsion.

 

[Bobbywhy]

physicsfrenzy, Welcome here to Physics Forums!

If you put some powerful magnets in your shoes, wouldn't you need magnets on the ground to repel them?

 

[CWatters]

http://suspensioncoil.com/coil-spring-shoes/?

 

[HallsofIvy]

You got 97% in physics and did not learn anything about "conservation of momentum"? Very sad.

Your set up has all magnets as a system contained on your body and so cannot change the momentum of your body. They cannot add any speed at all to your body.

 

[NascentOxygen]

I have been thinking of a cool project that involved 4 neodymium magnets and using the repulsion force between them to act like a "spring" effect to make you able to jump and run at increased increments.

Hi physicsfrenzy. Yes, it will work, though the efficiency gain may not be as spectacular as you hope. One thing you may not have considered is the gradual loss of magnetism of the ground-contacting magnets due to the shock of hitting the ground hard with each step; a rubber sole should go a long way to easing that. I can see that a well-designed containment box will be essential.

You may find that best efficiency is associated with a kangaroo-bound gait, keeping feet together throughout. Some adaptation of ski poles might reassure the beginner. The extra weight compared with spring shoes will help develop good calf muscles!

Good luck with your physics career.

 

[ZapperZ]

I still say that Bobbywhy brought up the most sensible question that makes this scenario rather dubious. What is it going to repel against? The "ground" is usually non-magnetic! Try it!

Zz.

 

[Jimmy]

This is akin to pulling yourself up by your bootstraps.

 

[HallsofIvy]

PhysicsFrenzy said clearly in his first post that he would have magnets with opposing poles in each shoe. He seems to be under the impression that that would cause a net upward push. As I said before, he simply does not comrehend "conservation of momentum".

 

[CWatters]

You got 97% in physics and did not learn anything about "conservation of momentum"? Very sad.

Your set up has all magnets as a system contained on your body and so cannot change the momentum of your body. They cannot add any speed at all to your body.

When running the tendons in your legs act as springs to store and release energy at different parts of your stride. Amputee runners use carbon fiber prosthetic legs with considerable spring built into them. Some time ago it was questioned if this (and their reduced weight etc) gave them a potential advantage over able bodied runners. Would their artificial springs be more efficient than those of real legs? The answer is apparently no...

http://www.colorado.edu/news/releases/2009/11/04/new-study-further-disputes-notion-amputee-runners-gain-advantage-prostheses

http://jap.physiology.org/content/108/4/1012.full

allowing...

http://www.popsci.com/technology/ar...-be-first-amputee-compete-world-championships

 

[DaveC426913]

To get this to work - even in principle - here's what you'd need to do:
1] Arrange the magnets on your feet so that they are all pointing the same direction - say, south poles downward (or even more simply, one large sole-shaped magnet).
2] Arrange magnets in the floor so they are all pointing with south poles upward.

Now your shoes will be repelled from the floor.

In theory, this would provide a springlike effect. If you jumped off a chair onto the floor, the magnets would repel and bounce you back up like a pogo stick.

Unfortunately, in practice, there are several problems:
1] You could only do it in a controlled environment where you could line the floor with magnets. and you cannot simply space them out. The field must be uniform. You'd have to line every inch of the floor with magnets.
2] It would be impossible to stand upright, let alone jump, let alone run. It is equivalent to trying to stand upright in a swimming pool by strapping a beachball or floaty noodle to each foot. I've tried it. It's impossible. But it's a lot of fun to try.
3] The magnets would try very hard to flip over. You would almost certainly sprain both ankles.

While it would not be of practical use, it could be a fun amusement setup. But you would absolutely have to wear full padding and a helmet.

 

[physicsfrenzy]

Thanks for the tons of feedback already wow!

HallsofIvy,

I do know what conservation of momentum is. You can not change momentum between two objects that collide.

But i do not see where they are colliding. Its acting like a spring effect like springs. One magnet on the bottom and one on the top with repelling forces between them. If springs work wouldn't this? I guess I got my question answered.

Thanks everyone!

 

[Integral]

You all need to read his post a bit closer. He is putting a pair of opposing magnets within the shoe. So you would be walking on a cushion of magnetic levitation. Sounds like fun.

Two magnets might not be enough to make this work, also you would need to tune the shoes to the weight of the person wearing them. The magnets would always be pushing the soles of the shoes away from the uppers so would need to be very well build or they will self destruct.

Not sure if you could contain all of the magnetic field within the shoe so you would tend to pick up stray bits of iron as you walked. Don't try to walk across a iron plate, you just might lose your shoes!

 

[CWatters]

But i do not see where they are colliding.

They don't have to touch in order to "collide". Imagine a steel ball coated with rubber. The steel part of the ball doesn't have to come in contact with the ground for the ball to collide with it, it's just that there is a springy rubber layer in between. That rubber layer could be replaced by any number of alternatives (such as two layers of N to N magnets forming a spring).

If the springs/magnetic springs aren't fully compressed (eg they don't "bottom out" or run out of travel) then you could think of each step as an "elastic collision" rather than an "inelastic collision"

http://en.wikipedia.org/wiki/Elastic_collision
Conservation of Energy

http://en.wikipedia.org/wiki/Inelastic_collision
Conservation of Momentum

It wouldn't be a perfect elastic collision as some energy would be lost heating the springs but perhaps close enough.

 

[OmCheeto]

You all need to read his post a bit closer. He is putting a pair of opposing magnets within the shoe. So you would be walking on a cushion of magnetic levitation. Sounds like fun.

Two magnets might not be enough to make this work, also you would need to tune the shoes to the weight of the person wearing them. The magnets would always be pushing the soles of the shoes away from the uppers so would need to be very well build or they will self destruct.

Not sure if you could contain all of the magnetic field within the shoe so you would tend to pick up stray bits of iron as you walked. Don't try to walk across a iron plate, you just might lose your shoes!

It does sound like fun. And we discussed the hazards of using magnets a few days back.

Someone suggested earlier that it would be just like springs. I think it would be a bit different, as springs are linear, and magnets are not, in their force vs distance equations:

springs: F = -kx

opposing magnets:

What the hell does that mean?

hmmm... If one merges all the variable constants, it looks like the equation becomes: F=-k/x²

Springy, but different.

Unfortunately, I don't have the willpower today to solve whether or not a magnetic-springy shoe would be economically feasible to produce as a world commodity, but... I wonder if this technology can be used somewhere else...

-------------------------------
The physics of mud, will kick your butt, every time...

 

[HallsofIvy]

Thanks for the tons of feedback already wow!

HallsofIvy,

I do know what conservation of momentum is. You can not change momentum between two objects that collide.

That is one consequence of "conservation of momentum". It is NOT "conservation of momentum" itself. "Conservation of momentum" says that the momentum of a system cannot be changed except by an external force. What external force is acting on you here?

But i do not see where they are colliding. Its acting like a spring effect like springs. One magnet on the bottom and one on the top with repelling forces between them. If springs work wouldn't this? I guess I got my question answered.

Thanks everyone!

You said "You have two magnets for each shoe. You contain the two magnets inside a non-magnetic material so the axis are lined perfectly underneath the shoe."
Now it sounds to me like you are having two magnets oppositely aligned in each shoe and trying to use the magnetic repulsion of the two magnets in the shoe to act on the body as a whole. Everyone else is talking about a situation in which there are magnets in the shoes acting against magnets in the floor. If that is what you intended please say so.

 

[DaveC426913]

That is one consequence of "conservation of momentum". It is NOT "conservation of momentum" itself. "Conservation of momentum" says that the momentum of a system cannot be changed except by an external force. What external force is acting on you here?

Ohhhhh! I see now!

You contain the two magnets inside a non-magnetic material so the axis are lined perfectly underneath the shoe.

All he's doing is making magnetic springs. The shoes will have a form of piston, two pistons per shoes. Each piston contains two magnets, opposing each other.

If he jumps up and down, the springs will conserve his momentum - exactly as if he were wearing coil springs on his feet.

 

[physicsfrenzy]

You all need to read his post a bit closer. He is putting a pair of opposing magnets within the shoe. So you would be walking on a cushion of magnetic levitation. Sounds like fun.

Two magnets might not be enough to make this work, also you would need to tune the shoes to the weight of the person wearing them. The magnets would always be pushing the soles of the shoes away from the uppers so would need to be very well build or they will self destruct.

Not sure if you could contain all of the magnetic field within the shoe so you would tend to pick up stray bits of iron as you walked. Don't try to walk across a iron plate, you just might lose your shoes!

Thank you! You explained my scenario very well. The "container" would have to be a sturdy non magnetic material to contain the magnets in a straight axis to get the most out of levitation. Basically it needs a very strong base and sides to contain those magnets or I got a feeling it would be dangerous.
And Dave,

That is exactly what I mean! I would like to do that. Would it be possible?

 

[Bobbywhy]

Thank you! You explained my scenario very well. The "container" would have to be a sturdy non magnetic material to contain the magnets in a straight axis to get the most out of levitation. Basically it needs a very strong base and sides to contain those magnets or I got a feeling it would be dangerous.



And Dave,

That is exactly what I mean! I would like to do that. Would it be possible?

physicsfrenzy! So sorry I misread your original post and misunderstood your plan. Finally I get your idea. Congratulations on your novel idea...hope you continue onwards. Some of mankind's best ideas come in our earlier years! Hope you are keeping a notebook!
Cheers,
Bobbywhy

 

[Integral]

It does sound like fun. And we discussed the hazards of using magnets a few days back.

Someone suggested earlier that it would be just like springs. I think it would be a bit different, as springs are linear, and magnets are not, in their force vs distance equations:

springs: F = -kx

opposing magnets:

What the hell does that mean?

hmmm... If one merges all the variable constants, it looks like the equation becomes: F=-k/x²

Springy, but different.

Unfortunately, I don't have the willpower today to solve whether or not a magnetic-springy shoe would be economically feasible to produce as a world commodity, but... I wonder if this technology can be used somewhere else...

-------------------------------
The physics of mud, will kick your butt, every time...

That sure looks like a Kinetic sculpture! Da Vinci Days is near, will you be there?

 

[DaveC426913]

Basically it needs a very strong base and sides to contain those magnets or I got a feeling it would be dangerous.

It would be no more dangerous than a pogostick of the same height.

A pair of magnoboots that could add two feet to your jumping height would be exactly equivalent to a pogostick (or a pair of springs) that could add two feet to your jumping height.

 

[OmCheeto]

That sure looks like a Kinetic sculpture! Da Vinci Days is near, will you be there?

I hope so. That is a "real" mental workout, trying to figure out why a bunch of smart people, got stuck in the mud.

"That one has too many fat people on it"
"That one has too skinny wheels"
"That one is too shiny"
"This is Oregon. These college kids should have figured mud out by now..."

 

[NascentOxygen]

https://www.physicsforums.com/showpost.php?p=3982441&postcount=7
It might be better to use horseshoe magnets (in more of a squashed U-shape really). You'll get double the repulsion, and with much less stray field there's no likelihood of physicsfrenzy becoming glued to steel sewer covers, as Integral foresaw. Might still pick up some nails and bottle tops, though.

 

[nemesiswes]

I was actually just thinking of something like this today, lol. Except I was imagining it would be for jumping off something high like a building, I was watching batman, lmao. I was thinking one of the magnets (could be top or bottom) would be a electromagnet and it would adjust for how fast your downward speed was. So the higher the building, the greater the repulsion. I imagined the shoes would look like they were for giants, lol. I pretty much stopped thinking about it until now, lol.

 

[physicsfrenzy]

Its been over a year since I had thought of this idea and I had to revive this old topic to generate new discussion on my shoes. (no pun intended)

The reason why I revived this topic is now I have money to invest in a prototype pair to see if they do in fact work, and how the best effective way of doing so.

 

[HallsofIvy]

Thanks for the tons of feedback already wow!

HallsofIvy,

I do know what conservation of momentum is. You can not change momentum between two objects that collide.

But i do not see where they are colliding. Its acting like a spring effect like springs. One magnet on the bottom and one on the top with repelling forces between them. If springs work wouldn't this? I guess I got my question answered.

Thanks everyone!

Then you do not understand "conservation of momentum". The total momentum of any system is conserved. It is NOT necessary that anything "collide".

 

[ModusPwnd]

How does conservation of momentum undermine his idea?

Isnt he just trying to make an amateur version of the "blade runner's" legs? (http://news.bbc.co.uk/sport2/hi/olympics/athletics/7141302.stm)

Hes not trying to violate conservation of momentum. He is trying to save and store the energy of the downward motion and reuse it for the upward motion. Like a pogo stick. Or no?

 

[CWatters]

Exactly. See my post a year ago. When running human legs act a bit like springs and absorb and release energy when your feet hit the floor. The question is can adding or replacing them with real springs, magnets or whatever make running more efficient. I see no reason why it's not possible to improve on the performance of human springs but clearly they can't be >100% efficient. Perhaps that's what HallsofIvy is trying to say.

 

[sophiecentaur]

1. Only a magnet can repel a permanent magnet, so you would need magnets on the track.
2. Stability would be a problem and the system would almost certainly flip you over on your back, painfully.
3. This effect would have to give a reasonable 'cushioning effect', over a distance of several cm. This could require seriously powerful magnets which would, even with the sexy new magnets available, involve a lot of weight. A spring to achieve the same thing would be much lighter and cheaper and would also be safer.

[Edit: that will teach me to read all the posts and you can disregard my point 1. The rest is ok though ]

 

[OmCheeto]

1. Only a magnet can repel a permanent magnet, so you would need magnets on the track.
2. Stability would be a problem and the system would almost certainly flip you over on your back, painfully.
3. This effect would have to give a reasonable 'cushioning effect', over a distance of several cm. This could require seriously powerful magnets which would, even with the sexy new magnets available, involve a lot of weight. A spring to achieve the same thing would be much lighter and cheaper and would also be safer.

[Edit: that will teach me to read all the posts and you can disregard my point 1. The rest is ok though ]

Well, let's replace your point 1, with my point 4:

4. The equations don't work at shoe scale distances

You're welcome. And when it comes down to it, if I don't have the supplies lying around my house, and it's going to cost more than $20 to build, I always do the math first.

Also, the equation is obviously not valid for magnets that are extremely close to each other. As when the distance approaches zero, the repulsion tends towards infinity. And I know that is not correct, as I can with just a bit of effort, push two of my neodymium magnets together.
(1/8" length, 5/16" diameter)

At one micron separation, my magnets, according to the equation, should have a repulsion of about 190,000,000 Newtons*, which is a bit more than my thumb and index finger are capable of I'm sure.

*What is 190,000,000 Newtons equivalent to? The first stage of the Saturn V rocket had a thrust of only 34,000,000 Newtons. So a 190 megaNewtons is a lot!

So what do you do when the maths don't work?

I would do the experiment, and try and determine a curve fitting function for force vs small distances, but my magnets are too small to control, in a kitchen lab.

I did though do an experiment just now, with some 200 gram, 1970's era speaker magnets. I discovered that they were so weak, that when I placed one above the other, gravity won.

I did another experiment where my neodymiums floated in a plastic tube about 4 cm above the speaker magnets. I used a bamboo skewer to push the neo's down towards the speaker magnet. At around 5 millimeters, the repulsion was lost, and the neo's slammed into the speaker magnet.

hmmm... This is starting to look ugly on the human mass jumping shoe scale. And that's just the thoughts in my head. Just imagine what happens when you do the math.

hmmm... I wonder if Phil Knight had to put up with this negativity when he developed his air sole technology.

Its been over a year since I had thought of this idea and I had to revive this old topic to generate new discussion on my shoes. (no pun intended)

The reason why I revived this topic is now I have money to invest in a prototype pair to see if they do in fact work, and how the best effective way of doing so.

Just do it.

 

[B4ssHunter]

to those talking about the law of conservation of momentum , its true that the momentum is conserved , but he is using magnets in the shoes to transfer his downward momentum into an upward momentum
instead of pushing on Earth and pushing it down , the magnets will push him up with that same momentum . just like a spring .

 

[A.T.]

Someone suggested earlier that it would be just like springs. I think it would be a bit different, as springs are linear, and magnets are not, in their force vs distance equations:

Many shoes have air cushions which are also non linear. The only difference from using magnets is that the shoes will be very heavy, and jumping will be no fun at all.

 

[Human268]

Great idea

I accidentally saw this post and I have been planning the same project. I wonder if you have had any success? Although you are not creating new energy using these magnets, I think the springlike effect of opposing magnets could lead to greater energy efficiency in running. There are a lot of details that would need to be fine tuned - ie.. Magnetic strength, proper positioning and encasement for stability..etc. let me know if you are interested in collaboration

 

[CWatters]

Carbon fibre springs have already been used for a similar application :-). I suspect they are somewhat lighter.