h a l f b a k e r yClearly this is a metaphor for something.
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Normal skateboards use ball bearings and their top speed all
depends on the quallity. Magnetic barings would allow you
to
reach speeds nearing terminal velocity. To make these
bearings a strong magnet would need to be used maby an
electromagnet, Two cilindrical magnets would need to be
used,
one attached to the truck wich would need to be modified
for structural reasons, the wheel would be moulded around
the second outside ring of magnet, the wheel would be
held
onto the end of the truck by a large washer and a nut
similar
to a conventional skateboard wheel. The two magnets
would
be have the same poles facing inwards causing the wheel to
float on the truck axel and creating very little friction. This
set up would allow lugers/downhill skaters to reach great
speeds.
Magnetic bearings
http://www.google.c...&btnG=Google+Search
Magnetic bearings on Google [hippo, Sep 02 2002, last modified Oct 05 2004]
Scrollerwheel
http://en.wikipedia.../wiki/Scrollerwheel
Cool type of rotary bearing [goldbb, Jan 22 2009]
[link]
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<Hands Gulherme a vowel>e</Hands Gulherme a vowel> |
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Thanks thumbwax I ran out of the letter e. Maby it could
be a combination bearing, I would think that a luge would
be large enough to house an electromagnet and the
spaceing and number of wheels means there is a wider
distribution of weight than in a skateboard. The idea of
spherical
wheels with the magnets housed inside isnt bad
but this means you have to change the whole truck to
change the wheels for different conditions. (I would think
that wheels selection would be important in luge.) |
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//Such a board would be heavy and buildable but I wouldnt stand on the thing, //
Bollux to that, I'd stand on it. You'd get used to it after a while. This idea rocks, IT ROCKS, you hear me?. I'm going to go an buy a croissant and eat it in honour of this idea. I have <expensive> bearings on my longboard, but which now need changing. This would allow you to never need to change your bearings, just plug your board in to recharger over night. YES! Good work [Gulherme] |
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One more thing I just thought of, wouldnt it be possible
to have some sort of tiny generator connected to the
skateboard wheel by another little wheel that spins while
the board is rolling and produces some electricity to
power the electromagnet? |
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Yeah, but thats gonna slow you down some surely; the opposite to the effect you want... |
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Imagine the air on the half pipe though, and hey, on the full pipe you'd never be able to get off. (note to science-pedants I know this is not actually the case) |
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These bearings would give you a bit of extra pop in your
ollies too I think. |
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I used to skate back in the 70s. i had a Mike Weed Rad. Terrain deck, Gullwing trucks and 70mm. red Kryptonic wheels with enclosed bearings.It was pretty quick. I now ride a 6'5" T&C thruster (surfboard)on the West coast of NZ.(mostly) and tho' the idea of terminal velocity on a skateboard sounds pretty appealing, you guys should have a go at a solid 6ft. swell coming up from the Tasman in mid-winter. It adds a new dimension to Term. Velocity. |
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I live the other side of the Tasman braindamage and get
to sample such swells on a regular basis, as we speak
there is a mega low pressure system of death bearing
down on our west coast, should bring swell in the 60ft
range to certain spots not that I'm game to take it on. |
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Wooo-hooooo, dust off the rhino chaser and the jetski... And that's BRIANdamage to you bruv. |
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You should get a decent sized NW swell later in the week |
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Stop talking about surfing you gits, I've been stuck in lovely landlocked Leicester all summer, missed my annual two weeks in Cornwall, at Perranporth trying to stand up in the shallows.... |
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Idea is good, but the magnetic force needed to stop the 2 sections of the bearings coliding during any kind of pressure (from somethin like landing at the bottom of stairs, or even a decent sized ollie,) is far too great. you would need to increase the axial size of the bearing massively and therefore the wheel width and board width. plus the power needed to drive an electromagnet strong enough would be phenomenal. You'd be lucky to get 5 mins before you needed to recharge the batterys, which themselves would be huge. The board would be as big as a Kenworth. |
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aside from that factor, you said you were going to use washers to stop the axial movement of the bearings, this would create more friction than a normal deep groove roller bearing creates in the first place. |
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If you want board that effectively floats on magnets than it'd be far easier to look at biulding a magnetically charged skatepark and then charge the board aswell, completely forget about trucks and bearings and wheels. |
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You are Thinking:
"Yeah, magnetic is cool cos' it doesnt touch any thing and is superfast!" |
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If you were smarter, you'd realize:
"Wait, it'll either need opposing magnets to retain the wheels so they don't fly off and kill a small child, or it'll need some kind of retainer that will contact the wheel, defeating the purpose of magnetic bearings, or that the bearings will be so large that they will require a massive effort to move the sled of a skateboard, and that the delicate magnetic balance necessary for speed will NEVER withstand the impacts and stresses of skateboarding, (thank you, "Zircon", although a magnetically charged skatepark is kinda dumb, considering that not only would it present a massive health hazard to anybody with a pacemaker and that a simple iron chunk would prove deadly to someone above it),so if you want to go downhill so fast, sod off and take an airplane. |
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I think this is a sweet idea, i want one, where can i buy it. Oh, that's right, it's just a dream...."a magnetically charged skatepark is kinda dumb, considering that not only would it present a massive health hazard to anybody with a pacemaker". I really think someone with a pace maker is not gonna ride a skateboard....prove me wrong though, but i just doubt it |
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So, does anyone know just how much
the turning-friction of regular bearings
slows down a board? I'll be you a
croissant that it's negligible and that
most of the losses come from vertical
movement in the board going over
bumps and stuff (with the energy being
lost because the rider's legs are not
perfect springs), and most of the rest
from air resistance. If a significant
fraction of the energy were lost through
friction in regular bearings, they'd melt
in a moment (yes, I know they get hot,
but not *that* hot...). Plus, you may
find you can only skate due north. Plus,
what's an ollie? (Yes, non-skating
person). |
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An "ollie" is the term used for - basically - jumping with a skateboard. I had an old skateboard book that gave it the silliest definition, along the lines of "defying gravity" and "graceful acrobatics."
It is done by jumping equally with both legs, and using your rear leg at the last fraction-of-a-second to kick the "tail" (back) of the board against the ground, causing it to pop up; while this is being done, your front foot slides up and forward, pushing the "nose" (front) of the board in the same direction, which causes the tail (which already has upward momentum from the pop) to straighten out with the rest of the board. If you're good, it almost looks like the board is glued to your feet.
And the bearings can get *extremely* hot if they're bad. My current deck (skateboard) has shitty bearings, and after a long session, I can't even touch my wheels or trucks. |
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Ah - thanks for the explanation,
AA.
As for the magnetic
bearings, it's pretty clear that the losses
through conventional bearing friction
are not significant (your bearings get
hot, but they would literally be white-
hot in a moment if they were absorbing
any significant fraction of your kinetic
energy). So, this may be a device for
reducing an already-small energy loss
and preventing bearings from getting
hot, but it's not going to make your ride
perceptibly smoother. |
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i would say its not that bad, but for the intented use i dont find it to be particulary perfect, the opposing magnets would reduce friction, but whats stopping the wheel and the trucks from separating, a washer and nut, that would have to be properly adjusted, but now we have one magnet pushing another magnet(and wheel) against a washer and but (which dont rotate) generate friction... |
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next what about the shear weight after a jump, these magnets maybe in an O shape around the trucks but thats the part most likely to bend. this is all relative to skateboarding. i ahvent thought much about street luge |
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Perhaps scrollerwheels [link] would be a good type of bearing for skateboards? |
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I agree that bearing losses with good ball bearings are likely to be a small fraction of total losses, so even if bearing friction could be eliminated your top speed would change less than you suggest. Rolling resistance where the wheels meet the ground is more important. Also, you are only being propelled by the force components parallel to your direction of movement, so you will never approach the terminal veocity experienced in freefall (if that is what you meant). |
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