h a l f b a k e r ySugar and spice and unfettered insensibility.
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Instead of making engine mounts out of rubber, use piezoelectric crystals, which create a voltage when squeezed or expanded. This wouldn't replace the alternator, of course, but would reduce the amount of work it needs to do.
As an added bonus, since the PZ engine mounts can monitor engine vibration
electronically, they can feed data on how much the engine is vibrating to the OBD system.
LTC 3588 Energy Harvesting Chip
http://cds.linear.c...atasheet/35881p.pdf
Commercial Chip [csea, Feb 01 2010]
[link]
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If I were feeling quibblish, I could point out that replacing
resilient rubber with energy-harvesting piezos must have a
consequence, and must sap some small permilletage of the
engine's performance. |
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But I am not, and therefore will not. |
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//resilient rubber with energy-harvesting piezos must have a consequence, and must sap some small permilletage of the engine's performance. //
What, you mean that fraction currently expended warming the engine mounts? |
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Not entirely. The engine mounts are elastic rather than
viscous, I think. |
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This means that they do not absorb a large part of the
energy, but merely store it between cycles. I suspect that
the energy in question is a very small but non-zero quantity. |
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[MB] Elastic materials absorb energy and convert it to heat,
only completely inelastic materials do not (they also don't
exist, but you can get close). In this instance, they are
specifically intended to absorb as much vibrational energy as
possible. If the mounts were rigid the engine would produce
a tiny fraction more power, but the passengers would feel
lots of vibration. This is the power that piezo mounts would
harvest. Not sure if it's enough to justify the cost of a
system to harvest it, but the idea is valid. |
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Cost? You mean I'm supposed to have been concerned about cost all this time? |
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Next thing you'll be asking for practicality. And safety. We may as well endorse customer satisfaction while we're at it. |
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I could just go to work and do all that. As a matter of fact, that's where I am right now. |
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Oh dear, [Hippo], I hate to correct you but alas you are
completely wrong. |
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Elastic materials store energy. This is why you can wind up
a clock, shoot an arrow, and indeed enjoy the delights of
pinging a rubber band across the room. |
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Rubber is not a perfect elastic material (so, it does
convert a small fraction of the energy to heat), but most
of the energy is stored. |
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Water is a fair example of an inelastic material, as is lead.
Squishing either of them will warm them up. (When you
referred to "completely inelastic materials", I think you
meant "completely rigid", which indeed do not exist.) |
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The "shock absorbing" rubber pads are not designed to
absorb vibrational energy, but to act as "mechanical
capacitors", effectively smoothing out the the vibrations
by storing and releasing energy. |
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(In contrast, true shock absorbers are indeed designed to
absorb vibrational energy. A common arrangement is to
have a piston moving through a viscous liquid; this
converts almost all of the input energy into heat. This is
very different from rubber blocks or any other form of
spring.) |
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Instead of piezo crystals, you could have the engine mountings made as very short tough mechanical linkages. As the vibration moves the engine-side-attachment in and out, it actuates a tiny, thick and very tough crank mounted on the chassis-side-mount. The crank powers a driveshaft that runs along the engine bay to the other mount, and is geared across to the other side. At some convenient point, a small alternator is geared off the shaft to generate electricity. The beauty of this scheme is that a gearbox could be selected to disengage from the alternator and engage a water pump, or any other small device that needed powering while you were on the move. Even a refrigeration pump to keep your ice-cream chilled. |
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Why not just properly balance the engine ? Rolls-Royce engines don't vibrate much .... |
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Yeah, tell that to the fish in the aquarium in the back of
mine. |
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I've been skeptical about the use of piezo materials to harvest vibrational energy, but I saw recently that Linear Technology, a respected silicon chip vendor, now has a nicely integrated harvester. [link] |
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You won't get much useable power from such a solution, but it would be practical for running some low-power electronics where regular sources are unavailable. |
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The link is interesting. I love the phrase "High Efficiency
Integrated Hysteretic Buck DC/DC" - sounds dirty. |
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[MB] Yes, I misspoke, and using the terms for collisions
rather than materials, and should have said rigid.
However, it is still correct to say that any flexing material
transforms some mechanical energy into heat. The
amount varies depending on the material, but some is
transformed. In addition, while you are right about the
nature of springs versus shocks, the anti-vibration mounts
serve a function somewhere in between the two,
absorbing some energy and stabilizing the system between
bounces. Regardless, to do this, they do flex steadily, and
this flexing of a piezoelectric material will produce energy
without robbing the engine of any more power than
normal mounts. |
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This idea is complete nonsense. |
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//This idea is complete nonsense// [+] |
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[MaxB] - are you confusing me with [MechE]? |
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Ooops - [hippo] - you are right. My apologies. |
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at idle the engine does tend to "rock" and could supply a few watts of power but at speed and under load a tuned and balanced engine does not vibrate but instead applies a steady load on the mounts. You would do better with regenerative damping on the suspension but that's already baked. |
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If the engine tends to rock at low speeds, it tends to rock a lot faster at high speeds, the system just eliminates it before it gets to you (Or the frequency is to high to be obvious). While a perfectly balanced engine with no vibrational tendencies is theoretically possible, it's not likely to occur in real life. The vibration can be minimized, but not eliminated. |
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You would end up harvesting more energy from the motion of the engine in response to road bumps than you would from the engine vibration. The idea is nonsense. You could also harvest a small amount of energy by damping the seats and the spare tire in the trunk. The engine mounts are there primarily to damp the torsion applied to the chassis when the load on the engine changes. This torsion is translated through the mounts to the suspension. Almost all of the energy that you are trying to capture by damping would simply be transferred to the suspension. If you would like I could do the math for you. Just give me some rough numbers on the compliance of the generators vs their output and I can give you an idea of exactly how inefficient this would be. |
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[WcW] has a point, I think you'd get more power from the flywheel/damper than the engine mounts, but it depends on the engine. Probably, the lower the number of cylinders, the more available power at the mounts, but this would also be true for the damper. |
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I used to have a motorcycle with a twin and there would have been LOTS of power as that thing used to vibrate me to death. |
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PS do engines still have dampers? |
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I wonder if it mightn't be possible to devise some sort of
"mini power-station" for use in a car. Basically, it would be
a bit like a conventional oil or coal-powered electricity
station, except that instead of using oil/coal to drive the
generator, you would somehow (??) couple the generator
(which would be smaller than that in a real power station,
obviously) to the engine, drawing off a small part of its
rotational energy and converting it into electricity. |
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Could such a thing work? Would it provide a useful amount
of energy? I guess it's unlikely we'll ever know. |
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It sounds like you're describing the device which this invention is designed to augment, but not replace. But I could be wrong. |
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Ian, thanks, great idea! Ok, so instead of having the engine mounts squeeze and pull PZ crystals, then each of the engine mounts will instead squeeze and pull an air bladder, creating a sound. Each air bladder will be acoustically connected with a thermoacoustic heat pump, which in turn will provide the passenger compartment with cooling or heating, as needed. |
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Rolls-Royce engines don't get very good fuel economy, either. 8/7. |
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know what other engines don't vibrate much? the inline 6. Mine is on polyurethan mounts, basically a tiny step from being solid. vibration is not bad. |
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a much more dramatic example of where you can get significantly more energy, the kind that can't just be designed out or balanced out, are the shock absorbers that are linear electric generators. |
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Still have that compliance/efficiency problem that we haven't resolved. |
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Baked - Honda and Toyota already use it, but in another way. The piezo-electric consumes power to vary elasticity. |
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[sstvp] So if I understand what you're saying, H&T have a system to adjust a load on a piezoelectric engine mount to vary its springiness (and thereby reduce vibration?) |
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Makes sense, do you have a reference / link? |
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// each of the engine mounts will instead squeeze and pull an air bladder // which is kept pressurized by a reserve tank. Two separate lines run through one way valves to replenish and withdraw air from the bladder. Lines from each bladder join together into a large pair just before the reserve tank, where a pair of turbines are coupled to small electrical generators. |
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