h a l f b a k e r yA riddle wrapped in a mystery inside a rich, flaky crust
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You're wondering why those automobilists don't respect you? That's because your vehicle is missing a lot to make it impressive. A brake light might help.
There are of course brake handles with switches which may be used to power a brake light. But with Murphy's law the battery is always down when
you really need it.
With today's LED technology, we need only very small electric power to produce quite a light show. Modify one brake shoe of the rear brake (in right-lane driving countries, the left one) so that there is a miniature dynamo and an LED attached to it. When the brake is activated, the dynamo gets in contact with the rim and powers the LED.
Maybe someone can marry this idea to the contactless Magnic bike light?
Rim Magnet Lights
http://www.bikerumo...iy-tire-studs-more/
[bs0u0155, Dec 09 2014]
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Annotation:
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I like this, but would use the energy to power my
horn. How dare someone make me brake? |
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Why not a shower of sparks, from a flint and a striker? |
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Why not just have a tiny hub or rim dynamo and a small
photovoltaic panel, that recharge a battery? Harvest small
amounts of energy in daylight or while riding, then use that to
power front and rear lights after dark. |
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I like the idea that the harder you brake, the brighter the light. So, why not dispense with the brake pads entirely (or keep them as a backup, if you're a wimp) and use the back-EMF to do the stopping. |
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Just a hub dynamo and a resistive load to dump it in (the brake lights). The brake lever would be replaced with a variac. |
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Brake shoe? What is this, the 50s? |
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//Brake shoe? What is this, the 50s?// |
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Hey! my drum brake is from the mid 60's thank you very
much. |
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Why does your drum need a brake ? You can just stop hitting it with
the sticks, shirley ? |
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Praps it's an electric drumkit. |
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Yes, that would make sense. |
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// //Brake shoe? What is this, the 50s?// Hey! my
drum brake is from the mid 60's thank you very
much. // |
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You know, they still make cars with rear drum
brakes. Ford Focus and Toyota Corolla are two
that I know of. |
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They're cheaper and last longer, and are
completely adequate on the light rear end of a
compact car. I've got an old 1998 Corolla with 150K
miles. The original rear brake shoes are still good.
I suppose I should check them again sometime
since it's been a while, but they performed well
during a panic stop on the freeway last month. |
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//completely adequate// words that make me die a
little on the inside. |
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My 1978 daily driver has 4 wheel discs. |
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//They're cheaper and last longer, and are completely
adequate on the light rear end of a compact car. // |
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Ah, but wait, the cast iron drum brakes are heavier. Now,
that means the overall mass of the car is greater. Now, if
we're going to have the same braking performance, then
we need bigger brakes. That's OK, we put bigger disks up
front, and bigger drums at the rear. We might need a
bigger pair of master/slave cylinders and the wishbone
arrangement might need to be beefed up a little, the
lines might need to be larger. OK, so a little more mass,
that's fine, some slightly bigger disks and drums, maybe
bigger wheels to fit them in.... |
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I've come to the logical conclusion that fitting drum
brakes at the rear leads to an out of control mass cycle.
Although they work great on bikes, as long as you don't
mind them weighing 2lb. |
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// they still make cars with rear drum brakes // |
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I hope you realize that this idea is about bicycles. And brake shoes are standard equipment with the rim brakes which most bicycles come with. |
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You wouldn't even need a dynamo; a permanent
magnet alternator would work fine. |
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Or glue some very small magnets to the inside of the
rim, and mount a solenoid beneath the brake shoe
(there are rear lights that work on this principle; the
magnet(s) are mounted on the spokes). Set up
properly, it would give you a rear light - brake light
combo; that is, the light would get brighter when
you applied the brakes. |
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// permanent magnet alternator // |
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The old-fashioned bottle-shaped rim "dynamos" are in fact just
that; a permanent magnet rotating within the pole pieces of a
coil. Since the lamps were incandescent filaments, no rectification
is needed. |
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However, lacking any sort of regulation, lamp brightness is a
function of wheel speed. |
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//Or glue some very small magnets to the inside of the rim,
and mount a solenoid beneath the brake shoe // |
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