OT: Small diameter magnetic roller between wheels to provide frictionless braking resistance?

[John Doe]

I'd like to use a roller between two wheels to provide some
(practically) frictionless braking resistance while going downhill.
Would an unconnected DC motor be the only possibility for that
purpose? Preferably the braking device would be all in one small
cylinder in between the wheels, but I can't imagine anything that
would provide a small amount of friction while not wearing out
components like an attached DC motor would. Being able to fine-tune
the resistance, like by moving the motor body away from the rotor,
would be ideal.

Is there some other device besides the magnetism of a DC motor shell
that might provide near frictionless roller braking?

Thank you.

Here's what it might look like, except with a much smaller motor and
not connected to a power source.
Newsgroups: alt.binaries.phish
Subject: attached DC motor to inline skates - File 5 of 5

Here's some background, for what it's worth.
One of the most difficult parts of in-line skating is going downhill.
Currently the best braking mechanism is a rear wheel brake. So
alternatively, some sort of roller between the wheels would not be
useful for emergency situations, but it could be useful for providing
a variable/preset amount of resistance while going downhill. It
wouldn't wear out the rubber brake and it wouldn't require lifting the
front wheels off of the ground. The same could might be usable for a
skateboard or scooter.

 

[Ned Simmons]

I'd like to use a roller between two wheels to provide some
(practically) frictionless braking resistance while going downhill.
Would an unconnected DC motor be the only possibility for that
purpose?

DC injection brakes apply DC to the windings of an AC induction motor

Hysteresis or eddy current brake
http://www.ogura-clutch.com/product...34&PHPSESSID=86039d94b27c7322163b0cab264880bf
http://www.ogura-clutch.com/product...35&PHPSESSID=86039d94b27c7322163b0cab264880bf

 

[PeterD]

I'd like to use a roller between two wheels to provide some
(practically) frictionless braking resistance while going downhill.
Would an unconnected DC motor be the only possibility for that
purpose? Preferably the braking device would be all in one small
cylinder in between the wheels, but I can't imagine anything that
would provide a small amount of friction while not wearing out
components like an attached DC motor would. Being able to fine-tune
the resistance, like by moving the motor body away from the rotor,
would be ideal.

Is there some other device besides the magnetism of a DC motor shell
that might provide near frictionless roller braking?

Thank you.

Here's what it might look like, except with a much smaller motor and
not connected to a power source.
Newsgroups: alt.binaries.phish
Subject: attached DC motor to inline skates - File 5 of 5

Here's some background, for what it's worth.
One of the most difficult parts of in-line skating is going downhill.
Currently the best braking mechanism is a rear wheel brake. So
alternatively, some sort of roller between the wheels would not be
useful for emergency situations, but it could be useful for providing
a variable/preset amount of resistance while going downhill. It
wouldn't wear out the rubber brake and it wouldn't require lifting the
front wheels off of the ground. The same could might be usable for a
skateboard or scooter.

Consider the concept of conservation of energy. You have to do
something with the energy that is gained by going down hill, right?

 

[RLM]

I'd like to use a roller between two wheels to provide some
(practically) frictionless braking resistance while going downhill.
Would an unconnected DC motor be the only possibility for that
purpose? Preferably the braking device would be all in one small
cylinder in between the wheels, but I can't imagine anything that
would provide a small amount of friction while not wearing out
components like an attached DC motor would. Being able to fine-tune
the resistance, like by moving the motor body away from the rotor,
would be ideal.

Is there some other device besides the magnetism of a DC motor shell
that might provide near frictionless roller braking?

Thank you.

Here's what it might look like, except with a much smaller motor and
not connected to a power source.
Newsgroups: alt.binaries.phish
Subject: attached DC motor to inline skates - File 5 of 5

Here's some background, for what it's worth.
One of the most difficult parts of in-line skating is going downhill.
Currently the best braking mechanism is a rear wheel brake. So
alternatively, some sort of roller between the wheels would not be
useful for emergency situations, but it could be useful for providing
a variable/preset amount of resistance while going downhill. It
wouldn't wear out the rubber brake and it wouldn't require lifting the
front wheels off of the ground. The same could might be usable for a
skateboard or scooter.

Dynamic or regenerative braking.

Electric forklifts use the generated current of the drive motor to stop a
coasting truck before reversing direction without use of the brakes. This
is known as "plugging" the truck. Motor becomes a DC generator when
coasting.

Some manufacturers of electric trucks use this force to enhance the
braking system to the point that brake shoes wear for extreem extended
times between replacement of the shoes. The brake pedal reacts as if it
has power brakes, when in reality this is an electrical adjustment to
increase or decrease the amount of (regenerative) braking as the pedal is
being pressed.

http://www.ab.com/drives/techpapers/RegenOverview01.pdf

 

[John Larkin]

I'd like to use a roller between two wheels to provide some
(practically) frictionless braking resistance while going downhill.
Would an unconnected DC motor be the only possibility for that
purpose? Preferably the braking device would be all in one small
cylinder in between the wheels, but I can't imagine anything that
would provide a small amount of friction while not wearing out
components like an attached DC motor would. Being able to fine-tune
the resistance, like by moving the motor body away from the rotor,
would be ideal.

Is there some other device besides the magnetism of a DC motor shell
that might provide near frictionless roller braking?

Thank you.

Here's what it might look like, except with a much smaller motor and
not connected to a power source.
Newsgroups: alt.binaries.phish
Subject: attached DC motor to inline skates - File 5 of 5

Here's some background, for what it's worth.
One of the most difficult parts of in-line skating is going downhill.
Currently the best braking mechanism is a rear wheel brake. So
alternatively, some sort of roller between the wheels would not be
useful for emergency situations, but it could be useful for providing
a variable/preset amount of resistance while going downhill. It
wouldn't wear out the rubber brake and it wouldn't require lifting the
front wheels off of the ground. The same could might be usable for a
skateboard or scooter.

Eddy-current braking would be interesting, but I don't know if the
speeds/forces would work out. It would involve an electromagnet or a
permanent magnet in proximity to a spinning aluminum or copper disc or
cup. But I suspect the braking force might be small, given the speeds
and geometry.

John

 

[default]

I'd like to use a roller between two wheels to provide some
(practically) frictionless braking resistance while going downhill.
Would an unconnected DC motor be the only possibility for that
purpose? Preferably the braking device would be all in one small
cylinder in between the wheels, but I can't imagine anything that
would provide a small amount of friction while not wearing out
components like an attached DC motor would. Being able to fine-tune
the resistance, like by moving the motor body away from the rotor,
would be ideal.

Is there some other device besides the magnetism of a DC motor shell
that might provide near frictionless roller braking?

Thank you.

Here's what it might look like, except with a much smaller motor and
not connected to a power source.
Newsgroups: alt.binaries.phish
Subject: attached DC motor to inline skates - File 5 of 5

Here's some background, for what it's worth.
One of the most difficult parts of in-line skating is going downhill.
Currently the best braking mechanism is a rear wheel brake. So
alternatively, some sort of roller between the wheels would not be
useful for emergency situations, but it could be useful for providing
a variable/preset amount of resistance while going downhill. It
wouldn't wear out the rubber brake and it wouldn't require lifting the
front wheels off of the ground. The same could might be usable for a
skateboard or scooter.

Check out stepper motors. Spun around and they are alternators. Very
cheap and easy when you just need an amp or two.

I played with a few to make cheap alternators for some engines (where
one needs 24 V DC and only has a rotating shaft)

The downside is they "cog" (slight "friction or detent" from one pole
to the next). A skate rider probably wouldn't notice it. Twist it by
hand and you would definitely notice it - very hard to turn with a
shorted winding.

Apply a short to the wheels connected to the windings (via something
like a mosfet) and you could make an electronic brake.

They already use this technology in "bait casting" fishing reels.
Apparently "bait casters" can't master, or can't bother to master the
subtle thumb pressure on the reel as the line spins out when open reel
casting. - so they apply a kind of magnetic brake - similar to a
speedometer mechanism.

Several magnets spin on the shaft and their close proximity to a
aluminum ring tends to take the ring along in the same direction as
the spinning shaft - the ring works against a spring and indicates the
speed.

Take a sheet of aluminum or copper (or non-ferrous metal) and drop a
magnet (strong magnet - nevoid) so it slides down the nearly 90
degree sheet - it will slowly drop until it reaches the end of the
sheet - then Newton takes over.

Point is . . some spinning very strong magnets on the wheels, would
make some decent brakes as the aluminum rings got closer to them.

And you didn't think of it first, so don't try to patent the idea.

 

[John Doe]

Eddy-current braking would be interesting,

But I suspect the braking force might be small, given the speeds
and geometry.

Controlling speed doesn't take much force, probably much less than the
36 V DC motor I connected it to. When the motor speed control trigger
was released and it did the electronic braking thing, it abruptly
kicked my leg backwards. Not talking about hysteresis or eddy current
braking, but in my estimation a small DC motor (think RC car) would be
enough magnetic power.

If it only requires the small part, doesn't require power, and is
adjustable (either resistance or top speed) like at the following link
provided by Ned Simmons, that would be great.

http://www.ogura-clutch.com/files/images/full/PHTS.jpg

Now I can find places to buy the things.

Thanks to the replies.

 

[[email protected]]

What about a pony brake...
Use a small water pump and restrict the flow...

 

[Carl McIver]

I'd like to use a roller between two wheels to provide some
(practically) frictionless braking resistance while going downhill.
Would an unconnected DC motor be the only possibility for that
purpose? Preferably the braking device would be all in one small
cylinder in between the wheels, but I can't imagine anything that
would provide a small amount of friction while not wearing out
components like an attached DC motor would. Being able to fine-tune
the resistance, like by moving the motor body away from the rotor,
would be ideal.

Is there some other device besides the magnetism of a DC motor shell
that might provide near frictionless roller braking?

Thank you.

Here's what it might look like, except with a much smaller motor and
not connected to a power source.
Newsgroups: alt.binaries.phish
Subject: attached DC motor to inline skates - File 5 of 5

Here's some background, for what it's worth.
One of the most difficult parts of in-line skating is going downhill.
Currently the best braking mechanism is a rear wheel brake. So
alternatively, some sort of roller between the wheels would not be
useful for emergency situations, but it could be useful for providing
a variable/preset amount of resistance while going downhill. It
wouldn't wear out the rubber brake and it wouldn't require lifting the
front wheels off of the ground. The same could might be usable for a
skateboard or scooter.

The first thing that came to my mind is an eddy current clutch or brake,
using permanent magnets. You have a few permanent magnets mounted to some
reasonably sturdy plate (has to be able to resist the opposing torque) and
you move it close to an aluminum or copper (or any conductive metal,
depending on braking power needed) disc that you want to slow down. Keep in
mind that the disc might get really hot, and could possibly come apart from
the eddy current losses melting it down, so mind that for extended braking
situations.
I asked a fellow who has worked with the North American Eagle on some
design issues about a related question awhile back (poke around
http://www.landspeed.com/researchbraking.html until you find a video of the
brake bringing a full sized lathe to a full stop by eddy current braking--I
couldn't find it when I went looking last couple times, though) with the
question about how much axial force one had to push the magnets, which he
didn't think was much, but couldn't quantify it.
The faster the parts move, the more of a difference it makes, especially
when there's a large speed differential between them. I'm not the
physicist, so I couldn't offer much more on the topic, other than it's
fairly easy to implement, but at low speeds the brake makes little
difference, so a light duty final brake is required.

 

[John Doe]

The first thing that came to my mind is an eddy current clutch
or brake,
using permanent magnets. You have a few permanent magnets mounted
to some reasonably sturdy plate (has to be able to resist the
opposing torque) and you move it close to an aluminum or copper (or
any conductive metal, depending on braking power needed) disc that
you want to slow down. Keep in mind that the disc might get really
hot, and could possibly come apart from the eddy current losses
melting it down, so mind that for extended braking situations.
I asked a fellow who has worked with the North American Eagle on
some
design issues about a related question awhile back (poke around
http://www.landspeed.com/researchbraking.html until you find a video
of the brake bringing a full sized lathe to a full stop by eddy
current braking--I couldn't find it when I went looking last couple
times, though) with the question about how much axial force one had
to push the magnets, which he didn't think was much, but couldn't
quantify it.
The faster the parts move, the more of a difference it makes,

That's good.

especially when there's a large speed differential between them.
I'm not the physicist, so I couldn't offer much more on the topic,
other than it's fairly easy to implement, but at low speeds the
brake makes little difference, so a light duty final brake is
required.

Yeah, I think a small non-powered device that increases resistance as
RPM increases (but is adjustable) would be great, even if it requires
heat sinking.

I'm still looking for places to buy.

 

[Robbo]

I'd like to use a roller between two wheels to provide some
(practically) frictionless braking resistance while going downhill.
Would an unconnected DC motor be the only possibility for that
purpose? Preferably the braking device would be all in one small
cylinder in between the wheels, but I can't imagine anything that
would provide a small amount of friction while not wearing out
components like an attached DC motor would. Being able to fine-tune
the resistance, like by moving the motor body away from the rotor,
would be ideal.

Is there some other device besides the magnetism of a DC motor shell
that might provide near frictionless roller braking?

Thank you.

Here's what it might look like, except with a much smaller motor and
not connected to a power source.
Newsgroups: alt.binaries.phish
Subject: attached DC motor to inline skates - File 5 of 5

Here's some background, for what it's worth.
One of the most difficult parts of in-line skating is going downhill.
Currently the best braking mechanism is a rear wheel brake. So
alternatively, some sort of roller between the wheels would not be
useful for emergency situations, but it could be useful for providing
a variable/preset amount of resistance while going downhill. It
wouldn't wear out the rubber brake and it wouldn't require lifting the
front wheels off of the ground. The same could might be usable for a
skateboard or scooter.

This is a little off what you asked for, but may be useful anyway. This guy
makes brakes for skateboards / longboards:
http://www.brakeboard.com/

 

[[email protected]]

Controlling speed doesn't take much force, probably much less than the
36 V DC motor I connected it to. When the motor speed control trigger
was released and it did the electronic braking thing, it abruptly
kicked my leg backwards. Not talking about hysteresis or eddy current
braking, but in my estimation a small DC motor (think RC car) would be
enough magnetic power.

If it only requires the small part, doesn't require power, and is
adjustable (either resistance or top speed) like at the following link
provided by Ned Simmons, that would be great.

http://www.ogura-clutch.com/files/images/full/PHTS.jpg

Now I can find places to buy the things.

Thanks to the replies.

Not sure what they call it but some smaller class B and K dieslel
trucks use a magnetic braking system on the drive shaft to help
control downhill accelleration.

CJ

 

[Robert Baer]

I'd like to use a roller between two wheels to provide some
(practically) frictionless braking resistance while going downhill.
Would an unconnected DC motor be the only possibility for that
purpose? Preferably the braking device would be all in one small
cylinder in between the wheels, but I can't imagine anything that
would provide a small amount of friction while not wearing out
components like an attached DC motor would. Being able to fine-tune
the resistance, like by moving the motor body away from the rotor,
would be ideal.

Is there some other device besides the magnetism of a DC motor shell
that might provide near frictionless roller braking?

Thank you.

Here's what it might look like, except with a much smaller motor and
not connected to a power source.
Newsgroups: alt.binaries.phish
Subject: attached DC motor to inline skates - File 5 of 5

Here's some background, for what it's worth.
One of the most difficult parts of in-line skating is going downhill.
Currently the best braking mechanism is a rear wheel brake. So
alternatively, some sort of roller between the wheels would not be
useful for emergency situations, but it could be useful for providing
a variable/preset amount of resistance while going downhill. It
wouldn't wear out the rubber brake and it wouldn't require lifting the
front wheels off of the ground. The same could might be usable for a
skateboard or scooter.

1) You need to absorb energy (equivalent to friction) to do any braking,
so reducing friction appears to be a poor choice.
2) Adding a motor wheel and using it as a generator is a start in the
right direction; use of a variable resistor across that generator to
dissipate energy is an improvement.

 

[John Doe]

Not sure what they call it but some smaller class B and K dieslel
trucks use a magnetic braking system on the drive shaft to help
control downhill accelleration.

Some trains do too, according to a History Channel (USA cable TV)
show, and they dissipate lots of heat.

I was thinking somehow I wouldn't need a heat sink since a DC motor
requires force to turn even with the leads disconnected. I'm not
disputing any of the expert opinions here, I know things aren't always
simple as they seem.

Thanks.

 

[JoanD'arcRoast]

Check out stepper motors. Spun around and they are alternators. Very
cheap and easy when you just need an amp or two.

I played with a few to make cheap alternators for some engines (where
one needs 24 V DC and only has a rotating shaft)

The downside is they "cog" (slight "friction or detent" from one pole
to the next). A skate rider probably wouldn't notice it. Twist it by
hand and you would definitely notice it - very hard to turn with a
shorted winding.

Apply a short to the wheels connected to the windings (via something
like a mosfet) and you could make an electronic brake.

They already use this technology in "bait casting" fishing reels.
Apparently "bait casters" can't master, or can't bother to master the
subtle thumb pressure on the reel as the line spins out when open reel
casting. - so they apply a kind of magnetic brake - similar to a
speedometer mechanism.

Several magnets spin on the shaft and their close proximity to a
aluminum ring tends to take the ring along in the same direction as
the spinning shaft - the ring works against a spring and indicates the
speed.

Take a sheet of aluminum or copper (or non-ferrous metal) and drop a
magnet (strong magnet - nevoid) so it slides down the nearly 90
degree sheet - it will slowly drop until it reaches the end of the
sheet - then Newton takes over.

Point is . . some spinning very strong magnets on the wheels, would
make some decent brakes as the aluminum rings got closer to them.

And you didn't think of it first, so don't try to patent the idea.

I like the eddy current idea best. Aluminum disk, strong little
magnets; wonder if there isn't a location for a pendulum actuator on
the boots that closes the gap *only* when coasting downhill... now that
would be sweet! [My damn inlines are gathering dust simply because I
can't control them downhill...got tired of launching myself into
someone's lawn or bushes just to avoid an impending intersection.
sigh.]

-j

 

[John Doe]

1) You need to absorb energy (equivalent to friction) to do any
braking,

Thanks, I can grasp that idea, the force that generates heat is the
force pushing back against the vehicle rolling down a hill.

so reducing friction appears to be a poor choice.

I'm sure you're correct, but I'm not sure what you're saying. I am
sure that a heat sink would last a lot longer than a rubber friction
brake, and the braking should produce little heat anyway.

2) Adding a motor wheel and using it as a generator is a start in
the right direction; use of a variable resistor across that
generator to dissipate energy is an improvement.

Not that this is what you mean, but for what it's worth.
For this application at this time, just using a ready built device
that can be rolled against the wheel is probably better then trying to
turn a wheel into the device itself. And using a smaller scale device
would probably produce smoother rolling (I suppose that has to do with
the magnet configuration), and smooth rolling matters a whole lot.
When standing on a skate/board, unnecessary jerking motions play
havoc with my reflexes.

Someone else with the same hobby might consider adding flashlight
bulbs as a side benefit. Personally, I'd really rather just buy an
eddy current brake, like the ones in the links, if I can find
them for sale. Hopefully they aren't just OEM parts.

 

[Gerald Miller]

Thanks, I can grasp that idea, the force that generates heat is the
force pushing back against the vehicle rolling down a hill.


I'm sure you're correct, but I'm not sure what you're saying. I am
sure that a heat sink would last a lot longer than a rubber friction
brake, and the braking should produce little heat anyway.


Not that this is what you mean, but for what it's worth.
For this application at this time, just using a ready built device
that can be rolled against the wheel is probably better then trying to
turn a wheel into the device itself. And using a smaller scale device
would probably produce smoother rolling (I suppose that has to do with
the magnet configuration), and smooth rolling matters a whole lot.
When standing on a skate/board, unnecessary jerking motions play
havoc with my reflexes.

Someone else with the same hobby might consider adding flashlight
bulbs as a side benefit. Personally, I'd really rather just buy an
eddy current brake, like the ones in the links, if I can find
them for sale. Hopefully they aren't just OEM parts.

If you look at the bottom of the page you will find a link to "sales
representatives"
Gerry }
London, Canada

 

[nick hull]

I'd [like to] buy an eddy current brake, like the ones in the links,
if I can find them for sale. Hopefully they aren't just OEM parts.

If you look at the bottom of the page you will find a link to "sales
representatives"
Gerry }
London, Canada

I'm not an OEM.

So they will probably send you a free sample if you ask

Free men own guns - www(dot)geocities(dot)com/CapitolHill/5357/

 

[John O'F]

Thanks, I can grasp that idea, the force that generates heat is the
force pushing back against the vehicle rolling down a hill.


I'm sure you're correct, but I'm not sure what you're saying. I am
sure that a heat sink would last a lot longer than a rubber friction
brake, and the braking should produce little heat anyway.

That depends what you mean by "little heat". Suppose you are skating
down a 10% grade of length 50 ft (15.2 m). If you are going 10 mph
(4.47 m/s), and you weigh 160 lb (73 kg), and your speed is held
constant, you are generating about 320 W for 3.4 seconds.
--
John

length of hill = 15.2 m, drop = 10% * 15.2 m = 1.52 m
energy = 9.8 m/s^2 * 73 kg * 1.52 m = 1087 J.
speed = 4.47 m/s, time = 15.2 m / 4.47 m/s = 3.4 s
power = 1087 J / 3.4 s = 320 W.

 

[Leon Fisk]

I'd [like to] buy an eddy current brake, like the ones in the links,
if I can find them for sale. Hopefully they aren't just OEM parts.

If you look at the bottom of the page you will find a link to "sales
representatives"
Gerry }
London, Canada

I'm not an OEM.

Have you looked at what they use on "Mag-trainers" for
bicycles. They use a magnet system and dial settings to
increase resistance. I have one and it will take quite a bit
of heat. They are made to spin pretty fast too. If you
aren't familiar with what I'm talking about see this page
for several different flavors:

http://www.nashbar.com/results.cfm?...nit=y&pagename=Category: Trainers and Rollers

Probably a bit big, but maybe a starting point. You might be
able to pick up a used unit cheap to dissect...