
World's Simplest Electric Train [video] - Turing_Machine
https://www.youtube.com/watch?v=J9b0J29OzAU
======
nly
I have some old Ladybird Classic books[0] that I inherited from my father, who
had them when he was a kid in the 60s. I remember one of them included
something like this. It may have been [1]. I can't imagine a modern childrens
book encouraging kids to take apart batteries or attempt their own
electroplating :-)

[0]
[https://en.wikipedia.org/wiki/Ladybird_Books#The_classic_Lad...](https://en.wikipedia.org/wiki/Ladybird_Books#The_classic_Ladybird_book)

[1] [http://www.ebay.ie/itm/VINTAGE-LADYBIRD-BOOK-Magnets-
Bulbs-a...](http://www.ebay.ie/itm/VINTAGE-LADYBIRD-BOOK-Magnets-Bulbs-and-
Batteries-Dust-
Jacket-621-2-6-/311198291511?pt=Antiquarian_Books_UK&hash=item4874dd1637)
(several pics of inside)

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quarterwave
Nice demo! Quick back of the envelope calculation for the current to overcome
dynamic friction:

I = mu_friction * Mass * grav_acc / (Turns_per_length * Area * Br_magnet)

Say Mass=0.1kg, coil at 600 turns per metre, hand-wave mu_friction=0.2, and a
rare-earth retention Br=1Tesla, gives a current of 3A. Maybe more to chug
along, would deplete a 2000mAh battery in about 30 minutes. Wire looks about
20 AWG, should get quite hot.

~~~
scoot
Which would theoretically use more energy, levetating the "train", or
overcoming the friction?

(I"m not suggesting this design can levitate, just curious about the trade-
off.)

~~~
CraigJPerry
Levitating.

Since overcoming the friction can be achieved through approaches like coating
the wire in ultra low friction material which will consume no power to
operate.

------
Someone
Same principle, different application (an electric engine):
[http://www.youtube.com/watch?v=zOdboRYf1hM](http://www.youtube.com/watch?v=zOdboRYf1hM),
[http://youtu.be/CoXboA8Ax7Q](http://youtu.be/CoXboA8Ax7Q) (or zillions of
other videos)

------
aleem
Almost as interesting, this video of a Stirling/Heat engine using just an
empty can, sticks and heat for power source:

[https://www.youtube.com/watch?v=FCjYZT6FJm4](https://www.youtube.com/watch?v=FCjYZT6FJm4)

And a very simple motor using just only a battery and wire:

[http://www.youtube.com/watch?v=vCSvNyHorgo](http://www.youtube.com/watch?v=vCSvNyHorgo)

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elsurudo
Could a design such as this work in the real-world, for a real train?

It seems to me that this could be feasible, since the power source is on the
"car" itself, and the coil (infrastructure) wouldn't be that expensive to
build (apart from the materials, of course). Or is it just too inefficient?

I don't know much about electronics/electromagnetism, admittedly.

~~~
MrBra
Also never forget the implications of the Square-Cube Law
[http://en.m.wikipedia.org/wiki/Square-
cube_law](http://en.m.wikipedia.org/wiki/Square-cube_law)

~~~
elsurudo
Can you explain what you mean by this? I can't find mention of its
implications to electricity.

~~~
cma
Probably that as you scale up the size linearly, the volume, and thus weight
goes up as the cube, but the surface area goes up as the square.

Since this design relies on closing the circuit by having the magnets rub the
wire, as you scale up you have an area in contact with the wire (surface area)
going up as X^2, but the downforce due to gravity going up as X^3.

You could add wheels and metallic contact brushes to scale it up. Keep in mind
copper is really expensive, and you'd be scaling that up nontrivially too, or
the current would fry the wire (I'd think the mass of the copper would go up
as the cube too, at least to accelerate at the same rate--acceleration depends
on the mass since F=MA, and the mass of the train went up as the cube).

------
MrBra
Why I do not know anything about how this works. I thought myself how to code
but each time I see this stuff I struggle with the feeling that I can't seem
to find a reasonably DIY knowledge builder for basic science branches like
this.

How do you start? Help please.

~~~
facepalm
We were taught this stuff in school, although I didn't think of that
application then :-) I mean that current running through a coil induces a
magnetic field.

Maybe just start with a physics school book?

Edit: in fact current running through a wire induces a magnetic field
(actually, just electrons moving, with or without a wire), I guess the coil
just gives it direction and kind of amplifies it (it's been a while).

------
thornjm
Anyone have a neat explanation for how it works?

~~~
kghose
When the train is placed completely within the copper coil, the circuit is
closed. A current flows from the +ve end of the battery, round the local part
of the coil, back into the -ve end of the battery (the magnets are
conducting).

This circulating current generates a magnetic field. Proper orientation of the
head and tail magnets leads to both magnets being pushed in the same direction
because of their interaction with the generated magnetic field.

This is the force that drives the train.

------
theophrastus
We may properly guess that the handedness of the helical copper coil
determines the direction the train takes? (left hand rule and whatnot) Connect
two loops of opposite handedness and perhaps the train will alternate
direction? nahh, probably just get stuck at the transition point.

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higherpurpose
Is this also the first real perpetual motion machine? That thing looks like it
could go on forever. Or is it limited by the current in the battery? If it is,
could the motion provide _back_ the energy to the battery somehow, and would
it be a net positive?

~~~
BoppreH
The motion depletes the battery, no different than a toy car motor. Yes, you
could theoretically provide energy back to the battery. No, it would not be a
net positive. It would deplete the battery faster, for a net loss because of
unavoidable conversion inefficiencies.

Edit: if you saw this video, realized there was a battery involved, and your
first thought was " _Perpetual Motion Device!_ ", you might be delusional or
severely misinformed. For your own sake, please research the topic a bit more
and avoid echo chambers.

~~~
dang
This comment would be better without the second paragraph, which is needlessly
personal and meta.

The first paragraph is splendid.

~~~
BoppreH
I agree the second paragraph is personal and meta, and I don't like it either.

But if I ever go down a rabbit hole and end up detached from reality, I would
_love_ to have someone to tip me off. It's like pointing out someone's fly is
open.

Maybe OP is perfectly sane and just got confused on the physics of this
system. Maybe they are very young. Or I misread their comment. In that case,
OP has my deepest apologies.

It's just that perpetual motion is a well known trap for intelligent people;
and expressions like "first real perpetual motion machine" and "provide _back_
the energy to the battery somehow" make me worry that a fellow human being is
going down the wrong path.

~~~
dang
Thanks for clarifying the helpful intention behind the comment. That does make
sense. Probably all it needed to do was make the intention a bit more
explicit, so it wouldn't be mistaken for one-upmanship.

By the way, your reply was so neutral and respectful that I didn't realize you
were the original commenter. That's remarkable, so thank you.

------
rootlocus
Anyone else notice the Berta Lovejoy comment? :D

~~~
twkl
I wonder who made the stupid decision to remove the downvote feature in the
YouTube comments. I heard that they couldn't implement it because Google+ only
has upvotes, but why they don't simply allocate another column in their
database is beyond me.

~~~
ohitsdom
If I had a dollar for every time a manager said "Just put another column in
the database"...

But seriously, I doubt it was a technical reason. Probably wanted to drive
more positive behavior.

