Practical Magnetic Levitating Transmission Gear System Loses Its Teeth 103
Zothecula writes: A new transmission device that uses magnetic levitation to almost completely eliminate friction and wear has been developed as part of the MAGDRIVE research project, a collaboration of seven European nations. The creation of the unit entailed the development of a magnetic gear reducer and corresponding frictionless magnetic axles. Aimed primarily for use in spacecraft due to its extended mechanical life, the system is also adaptable for use in automobiles, railways, and aircraft.
PBS had a documentary... (Score:3, Interesting)
On 5-10 years back about classic cars from some museum in SoCal or something.
The 3 primary vehicles they discussed were:
A 1900s era Battery Powered car with a 25 mile range.
A Steam powered car capable of 'gas-like' performance, given ample 'warmup' time.
And a 1920s or 30s electrocoupled automatic transmission car that I believe used increasing rotational speed to more closely couple the engine to the output shaft (Can't remember if it also had gears or if the coupling mechanism doubled as the 'gears'.)
Point being: So they're finally getting back to R&D on 'non-mechanical' coupling mechisms in modern vehicles. Yay! Only took like 90 years.
Re:PBS had a documentary... (Score:5, Insightful)
If something has been abandoned for 90+ years with no significant advances in the area, it's probably for a reason.
The upper limit on what such gearing could do is quite low. You're comparing a steel-pushing-steel scenario with one of trying to turn one magnetic wheel by pushing another near it. It's a loser except in ultra-specialist applications with exotic materials (Space? Fine. Your car? Unlikely).
Battery powered cars have been around forever. UK milk floats were entirely battery powered for decades, delivering hundreds of pints of milk to every house in the local town - they just used lead acid batteries and charged overnight. If you ever got stuck behind one, you quickly (!) found out the limitations of the technology of the time. We've moved on from there now, but only very, very recently.
Some huge trucks still have things based on variable transmission technology, so the entire gearbox doesn't have gears but just slides into the most convenient gearing automatically. They've been around for decades. And they work by using a strong belt that can slide up and down a conical shaft. I kid you not. Every few years, they are re-invented under another brand / patent / material and actually do quite a good job. But they are still considered specialist parts because we can't overcome their weaknesses.
Wankel engines were still in mass production until very recently (I believe Mazda don't have newer models that still use them?). Again, they do everything you would want and were constantly reinventing themselves for decades.
The problem is not that it's been done before. It's that it's been done an awful lot and not much more can be done that way. As such, although we have stronger room-temperature magnets, they aren't THAT much stronger. Superconducting magnets might be considered "new" but we can't make them practical yet - except in the absolute zero and vacuum of outer space.
There's nothing wrong with going back to the old, but you have to add something new (e.g. the clockwork radio was hailed as genius because it took the old and made it do something "new").
And I'm not sure this does that at all.
Re:PBS had a documentary... (Score:5, Insightful)
Some huge trucks still have things based on variable transmission technology, so the entire gearbox doesn't have gears but just slides into the most convenient gearing automatically. They've been around for decades. And they work by using a strong belt that can slide up and down a conical shaft. I kid you not. Every few years, they are re-invented under another brand / patent / material and actually do quite a good job. But they are still considered specialist parts because we can't overcome their weaknesses.
For someone asserting they know all kinds of "unknoiwn" details, you sure are behind.
The description above is called a "Constant Velocity Transmission" and both Nissan (recently) and Subaru (since the 70's) have these. Subaru has had MOST of their new non-performance car fleet use CVTs for the last three years. Nisssan's CVT uses a "pusher" belt made of stacked plates connected by a chain. Subaru, a regular chain.
This is not "specialists" parts anymore. This is just a different type of automatic transmission.
True, "going back to the old" works sometimes, often that is because materials and engineering concepts have advanced far enough to actually make the stuff work now. That doesn't mean tinkering with, or taking another try at these old methods isn't worthwhile.
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The Corolla has CVT now too. It's getting pretty common out there in some mass-market cars.
Also, on his other comment about Wankel engines, I believe that Mazda are re-introducing one. Just rumours now, but it's not necessarily dead yet.
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If your car has a CVT, it's a "Continuously Variable Transmission". The gear ratio continously varies, hence the name.
It's unrelated to the CV ("Constant Velocity") joints on the transaxle. Those are joints that maintain a constant velocity on the input and output shafts even though there is a bend in the middle, as opposed to a universal joint that has some change in angular momentum that varies based on the angle of the bend.
dom
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And unfortunately, this is why the reliability of the Nissan Pathfinder has become utter shit. I wanted to buy a 2014 model, but the horrific reviews of failing transmissions at 30k miles scared me and many others off. For good reason I might add.
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Yes, they are finally nailing down the technology for smaller vehicles, but it's still problematic to scale it up to "truck".
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And unfortunately, this is why the reliability of the Nissan Pathfinder has become utter shit. I wanted to buy a 2014 model, but the horrific reviews of failing transmissions at 30k miles scared me and many others off. For good reason I might add.
I had the 2013 Murano which came out with CVT. 2013-2015 models had CVT problems. Nissan has pretty much solved this and have since added the CVT to even more models. I did lose my transfer case when it was 8 years old and that is still a weak point today for the Murano.
Its one of the reasons why I replaced it with a Jeep last year. The Jeep Grand Cherokee has an 8-speed transmission. The Cherokee now has a 9-speed transmission. At the time that I was researching the Jeep, ZF was saying that they were
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For someone asserting they know all kinds of "unknoiwn" details, you sure are behind.
This coming from a guy that thinks CVT means "Constant Velocity Transmission"...
CVT = Continuously Variable Transmission
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Mitsubishi too has CVT (I have one in my 2012 Lancer). It's made by the same company who makes Nissan's.
FYI: Milk Float (Score:3)
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UK milk floats were entirely battery powered for decades, delivering hundreds of pints of milk to every house in the local town - they just used lead acid batteries and charged overnight. If you ever got stuck behind one, you quickly (!) found out the limitations of the technology of the time.
Limited? Perhaps they were, but they did provide for some thrilling television.
https://www.youtube.com/watch?... [youtube.com]
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Some huge trucks still have things based on variable transmission technology, so the entire gearbox doesn't have gears but just slides into the most convenient gearing automatically. They've been around for decades. And they work by using a strong belt that can slide up and down a conical shaft. I kid you not. Every few years, they are re-invented under another brand / patent / material and actually do quite a good job. But they are still considered specialist parts because we can't overcome their weaknesses.
My 2012 Toyota iQ [wikipedia.org] most definitely isn't "some huge truck", and its Super CVT-i transmission [wikipedia.org] most assuredly doesn't have any "weaknesses" that needs to be overcome, nor is it considered "a special part" - it's just another option on the options list.
In fact, after having driven one for three years, I'm not sure I'd want to have a "regular" automatic gearbox, and I'm absolutely sure I don't want to go back to manual. Rush-hour traffic no longer feels like sitting in a pedal car...
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If something has been abandoned for 90+ years with no significant advances in the area, it's probably for a reason.
One of those reasons may be that 90 years ago they did not have the super strong rare earth magnets like we have now. They're commonly used in places like hard drives which massively pushed development of such permanent magnets, and pushed the cost down.
As your attitude towards such abandoned technology is shared by many people, it may be forgotten about, and receive less attention than it deserves. Until someone realises that there is now technology available that makes the idea viable - like the much stro
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You need to have your head examined. Check into any major hospital to have this done and you will see an Earthly application for large superconducting magnets.
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If kept at ultra-low temperatures in a room full of equipment to help do that.
MRI's are one of the largest users of liquid helium in the world, and it's considered to be one of the bigger supply-chain problems to come in the future (i.e. we won't have enough).
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Oh, people have noticed that little train-wreck ahead, have they. That'll be nice.
Nobody is doing anything about it, of course?
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Been done before (Score:1)
Research into the 'most exciting aspect' (room temperature gearbox) part of this has been done before:
http://www.magnomatics.com/technology/magnetic-gears.aspx
But the idea of using the low temperature and vacuum of space to run superconducting systems seems quite innovative.
One of the main limitations with magnetic gears is that material properties (the saturation flux density of iron/cobalt basically) limits the amount of force that can be transmitted across the airgap. If the motion is being generated by
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Re:Efficiency??? (Score:5, Insightful)
Way more efficient than gears for loads it's designed to handle - but it's not meant for heavy lifting; the "magnetic gears" will "slip" if the load is too high, and in this case "too high" is quite low (think force required to move two magnets oriented in "repulsing" way against each other).
It would be great for stuff like stabilizing flywheels - things that once set in motion stay in motion for years, and may take a long time to spin up or stop. It would work well for things that require very little force, like reorienting the solar panels or aiming the antenna.
OTOH, stuff like lander wheel bearings or drills for picking samples are better handled with normal bearings that can take much heavier loads.
It's not a cure-all solution, it's just a good new option for specific applications. You won't use it to build a better crane but gyroscope flywheels could immensely benefit from that!
Re:Efficiency??? (Score:4, Interesting)
Way more efficient than gears for loads it's designed to handle - but it's not meant for heavy lifting; the "magnetic gears" will "slip" if the load is too high, and in this case "too high" is quite low (think force required to move two magnets oriented in "repulsing" way against each other).
If you couldn't move high forces with a transmission like this, then you also couldn't generate them with an electric motor, because you couldn't hope for the magnetic fields to turn the stator against high loads.
OTOH, stuff like lander wheel bearings or drills for picking samples are better handled with normal bearings that can take much heavier loads.
What happens when you put too much torque through a drill? You shatter your bit. What happens when you put too much torque through an axle? All kinds of exciting things can happen, check out some four wheeling videos. There's lots of reasons why some slip designed into the system is not an undesirable thing.
Re:Efficiency??? (Score:5, Insightful)
The other point being that it could be designed only to replace the kinetic friction parts of a transmission, the parts that synchronize the system. The gearing itself can probably still be mechanical. Not having to replace clutch plates, for example, might be a nice and relatively easily doable thing.
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We already have extremely low friction fluid-drive connections, they're called torque converters.
Yes, but you have to be already making use of fluid pressure for that to be worth using, and they have lots of drawbacks. Some hybrids replace the TC with an electric motor already, starting with the Honda Insight and including Subaru's hybrids. This is already a form of magnetic coupling, and the only friction comes from the bearings themselves. It is capable of doing the TC's job, plus giving full-drivetrain power — and regenerative braking.
In an EV, obviously, we can eliminate the ICE and otherwise
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Not having to replace clutch plates, for example, might be a nice and relatively easily doable thing.
Probably not worth it. A properly functioning clutch should have minimal parasitic loss from friction when engaged, so the only thing you're saving is the cost of replacing the clutch. Since clutches are usually easy to replace and relatively cheap, especially compared to the cost of something like this, it's probably throwing money away.
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You're probably right. Although I've had a standard transmission car go through 100% of its clutch plate and they are not cheap to replace. But what is? And how many cars have standard transmissions any more? And of those, how many go through a whole clutch plate before they die from some other cause. Toyota's magnetic regenerative braking system suggests that one "can" mass produce the requisite magnetic coupling, but there probably isn't a compelling reason to do it in this case.
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If you couldn't move high forces with a transmission like this, then you also couldn't generate them with an electric motor, because you couldn't hope for the magnetic fields to turn the stator against high loads.
Electric motors can stall, and when they do so they draw a terrifyingly huge amount of power compared to when they're operating properly. Providing that static torque is very expensive and often dangerous unless the motor and controls were designed for it.
It's not that magnetic fields can't be strong enough, it's getting fields that are strong enough without additional energy input.
=Smidge=
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Electric motors can stall, and when they do so they draw a terrifyingly huge amount of power compared to when they're operating properly.
Part of the motor controller's job is to prevent that, but it's irrelevant here, because they're using permanent magnets. The maglev bearings have to be cooled, but the part of the transmission that provides the gearing doesn't require any power at all. You design the system for the torques you're expecting to see and you get limited slip out of it for free. This part of the system could be used even without the maglev bearings, to eliminate gear friction and to prevent damage in the case of a lockup. If I
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Your argument basically boils down to "since electric motors can produce high torque, then permanent magnet couplings can also provide high torque"
My contention is you make it sound way, way simpler than it is. Also, you'll find that the really big motors are not the permanent magnet type exactly because producing a high-torque motor with permanent magnets is more difficult and expensive. It's an issue of flux density.
I'm sure you COULD design a permanent magnet coupling for any particular purpose, but that
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Your argument basically boils down to "since electric motors can produce high torque, then permanent magnet couplings can also provide high torque"
Yeah, pretty much.
Also, you'll find that the really big motors are not the permanent magnet type exactly because producing a high-torque motor with permanent magnets is more difficult and expensive.
Mostly expensive.
I'm sure you COULD design a permanent magnet coupling for any particular purpose, but that doesn't mean it makes sense to do so.
Well, TFA says they did it already, and I suspect they're smarter than you are (or me, to be fair) so I suspect you're on about nothing.
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As the AC said, for a very limited torque; 15 Newton-Meters. For a sense of scale, the recommended torque on a lug nut for a car tire is typically around 8-10 times that.
It's also under cryogenic conditions, intended for space applications, which is a rather special case (ultra-reliable under extreme environments) where it makes makes more sense to use something exotic.
And having said that, the more I learn about it the less I'm impressed with it. Magnetic bearings are pretty old hat technologically speakin
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As the AC said, for a very limited torque; 15 Newton-Meters. For a sense of scale, the recommended torque on a lug nut for a car tire is typically around 8-10 times that.
Please forgive my ignorance Smidge but I find that number quite astounding although I have no reason to doubt your comment.
Isn't 150NM about what a small car is putting out in terms of torque? Admittedly one (rightly or wrongly) is supposed to stand on lug nuts to tighten them properly, is this what is meant here?
Just seems quite a lot to me with my limited understanding of the topic.
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150Nm is about what a typical small car engine might be capable of at peak, but torque at the wheels would typically be greater due to gear reductions. Not really relevant, though - the torque of the engine applied to the wheels is not applied to the lug nuts on the wheels as a torque, but applied to the lugs themselves as a shear.
Maybe imperial units will help?
15 Newton-meters is roughly 11 foot-pounds. Most people can comfortably apply that kind of torque with a normal wrench, and that's about twice what
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Great explanation, thank you very much. :)
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the torque of the engine applied to the wheels is not applied to the lug nuts on the wheels as a torque, but applied to the lugs themselves as a shear.
And that is why lug nut torque is entirely irrelevant. Guess what? Small car, flat surface, don't set the brake, you'll move the car while tightening the lug nuts. But it's still irrelevant.
Torque specifications for lug nuts are typically in the 80 to 120 foot-pound range, though practically nobody outside of a reputable auto shop will bother with that (and even most reputable shops will gloss over it...)
There is no such thing as a reputable shop which won't torque your lug nuts to specification, only idiots who can't identify a reputable shop. My tire shop always torques my lug nuts with a torque wrench, to spec, and so do I. Not doing so risks a wheel falling off.
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The point of transmission is not only "displacement" of rotary movement but also exchange of rotation speed for momentum. So, if (as the article says) the gear ratio is 1:20, it means the load on an axis two such transmissions away will be 400 times that of a motor.
And while, yes, the design makes the system safe against damage due to too high load, the load it can provide is still far away from load which could damage the mechanics; if the slippage was to occur at loads ten times as high, it would still be
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The question is, how much force can it handle?
The video says it has a max input speed of 3000 rpm and a max output torque of 3Nm (~4 ft/lbs) with a gear reduction of 1:20.
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It would work well for things that require very little force, like reorienting the solar panels or aiming the antenna
Maybe you should look into this natural phenomena called "wind". It's there in many parts of the world. It's something that can put massive forces on things like solar panels, and to a lesser extent antennas.
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Yeah, so could you give me an estimate on the massive force of solar wind pressure against solar panels of a space probe?
Oh, wait, the linked article has it. At 1AU, typically in the range of 1–6 nanonewtons per square meter.
Yeah, massive indeed. The bearings stand no chance.
Might be a fit for EVs (Score:3)
It looks too bulky to provide a lot of gears in an automotive application, but if it could provide just two that you couldn't strip out no matter how much torque you put through them, it could be a really nice match for EVs. They would benefit from a transmission, but it's difficult for any transmission of a reasonable size to handle the output torque.
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Actually it is a terrible idea for an EV. Magnetic material properties limit the amount of force you can transmit across an airgap, and physics doesn't care whether this is being generated by rotating permanent magnets or electromagnets. If it made sense to put one of these on the end of your electric motor, it would make even more sense to just replace the gearbox's input rotor with an electromagnetic stator and have a direct drive motor in the first place.
Also, one of the great things about an electric mo
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Actually it is a terrible idea for an EV. Magnetic material properties limit the amount of force you can transmit across an airgap,
That is a feature. You're thinking in terms of a perfect world. I guess now we know what kind of cowardice you display, coward. You're afraid to think things through completely. Guess what? Torque converters slip sometimes, too.
one of the great things about an electric motor is that you can accurately control the torque output. It is really the most pointless application for an overload safe transmission
Again, you're not living in the real world, where EVs don't have multiple gears because they destroy transmissions when we try to use them with one more complicated than a simple reduction gear. See, the problem with torque control on an electric motor isn't how rapidly you can back
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Actually it is a terrible idea for an EV. Magnetic material properties limit the amount of force you can transmit across an airgap,
That is a feature. You're thinking in terms of a perfect world. I guess now we know what kind of cowardice you display, coward. You're afraid to think things through completely. Guess what? Torque converters slip sometimes, too.
one of the great things about an electric motor is that you can accurately control the torque output. It is really the most pointless application for an overload safe transmission
Again, you're not living in the real world, where EVs don't have multiple gears because they destroy transmissions when we try to use them with one more complicated than a simple reduction gear. See, the problem with torque control on an electric motor isn't how rapidly you can back off the power. It's how rapidly it comes on, and how much of it there is. When the motor applies its full torque, and there is some sort of binding or resistance, the transmission gets all of that torque right away. But energy from ICEs comes in squishy packets.
It's a feature and not a problem that this transmission will slip slightly occasionally. It will only happen when you would otherwise have been at risk of breaking something.
You attack my post yet leave out the most important point - that due to physical limits on attainable airgap sheer stress, the design is redundant compared to direct drive. I don't know why you left that bit out but perhaps you don't understand how magnetic systems work.
Also your bit about torque control is plain wrong. Current is immediately and directly proportional to torque in an electric motor. If the system 'locks up' as you say, then just limit the current. Let the control software provide the 'slip'
Re:Might be a fit for EVs (Score:5, Informative)
It looks too bulky to provide a lot of gears in an automotive application, but if it could provide just two that you couldn't strip out no matter how much torque you put through them, it could be a really nice match for EVs. They would benefit from a transmission, but it's difficult for any transmission of a reasonable size to handle the output torque.
Electric cars don't need gears in the first place. The only reason we have gears in IC engines is because, 1. it would be expensive and hard to keep the engines in sync if you had a separate one for each wheel, 2. IC engines operate in most efficiently at very specific RPMs. Notice how the tachometer tends to hover around 2000 rpm as you shift gears? That's what the gears are for, to keep the engine at a constant RPM. Electric motors work just as efficiently at just about any RPM.
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The other reason is that an ICE can't generate force when at rest (unlike an electric motor), so getting going from stationary is impossible without a clutch. That's why, if you drive a manual, the engine has to be revved and the clutch gradually engaged, bleeding power into the axels while allowing the engine to run without stalling. Engage the clutch too fast and the engine will simply stall.
I believe External CEs like steam engines can generate force when at rest, so they don't need gearing.
It's one of t
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Wrong. Electric cars have plenty of gears. You need to change the relatively high RPM of an electric motor to the lower RPM of the wheels. Also if a motor is driving more than one wheel you need a differential which is full of gears.
What you might not need is a transmission where you can actively change the gear ratio but there are plenty of gears in an electric car.
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An electric car does not have to have reduction gearing at all. In fact there are electric cars that do not [cleantechnica.com]. Repeat, do not [cleantechnica.com]. Believe it [sae.org]. In fact you can also do away completely with mechanical brakes.
If Tesla and GM and Nissan and others were all too timid or conservative to do it right, that is their problem.
Now who is wrong?
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Now who is wrong?
The lames who think that hubmotors are appropriate for anything more than a golf cart. Around 25 mph, the effect on unsprung mass begins to seriously affect handling. This speed is not a law of physics, it just has to do with typical wheel sizes and masses. If you could substantially knock down the mass of the stuff around the hub motor, then you could get away with it, but if you made a tire thinner then you can't handle higher speeds anyway, if you make a rim thinner it deforms, and so on.
If all you want
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"But unsprung weight" is a tired old preconception. Maybe if you bothered exploring the references provided and elsewhere you would be relieved of some of your misconceptions.
Protean Electric tackles the unsprung-mass 'myth' of in-wheel motors [sae.org]
Heresy Unsprung, Lotus Engineering: Unsprung Weight Doesn’t Really Matter Much[The Truth] [proteanelectric.com]
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Confronted with the results of actual engineering studies by experts in the field, which you could actually learn something from,
You failed to either read or comprehend your own citation, which says precisely the opposite of what you want it to say. Then you belittled others for it. Congratulations!
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"But unsprung weight" is a tired old preconception. Maybe if you bothered exploring the references provided and elsewhere you would be relieved of some of your misconceptions.
My. Asshole. That is complete fucking bullshit, and if you had any relevant experience with the subject at hand, you'd know that. I've personally felt the difference in ground contact made by removing just fifteen pounds per wheel, and it is massive. These assholes (who are selling something, you rube) are telling us that adding sixty pounds won't negatively impact handling. But hey, from your own first citation:
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This is what an electric motor does, except some mechanism (such as brushes) enables and disables the magnets i
Still need transmission in cars (Score:2)
Just like IC motors, electric motors do not provide constant power/torque across their whole speed range. There's a reason why cordless drills often have two or three speed transmissions.
A typical universal motor generates max torque just before it stalls, and relatively little torque at high speed. This is great for fast acceleration from a standstill, not so much for trying to hit maximum speed with just a single-speed gearbox.
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There's no need to keep engines "in sync" when they each power their own wheel. the road does that.
The only thing to watch out for would be loss of traction on a particular wheel, but traction control would not significantly more complicated with two or four drivetrains instead of one. In fact, you could do away with the wheel speed sensors and rely on relative engine rpms to determine when one has lost traction.
The biggest reasons we don't have cars with multiple IC en
I'm confused: Loses its teeth? (Score:2)
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Smoothing out diesel Aircraft engines? (Score:3)
This should really be looked at by those producing Diesel engines for Airplanes.
The biggest problem tinker's face when trying to put a Diesel engine on an airplane is that the Diesel has very massive "power surges" each time a cylinder fires, and a nasty power "stall" when it's compressing a cylinder. This isn't a huge deal with the other applications of Diesel engines, they just add mass to the fly-wheel and transmission and that takes care of it. In Airplanes however, the mass costs too much (in terms of airplane weight) so they try to reduce it as much as possible, however if you reduce it too much the propeller is literally torn apart by the surges and stalls. Early tests had the propeller lasting only hours when running on a 4 or 6 cylinder diesel. If there is a reduction drive on it to bring the RPMs further down they too like to self destruct with a Diesel.
If they could use a low-weight magnetic coupler to absorb the surges and stalls and provide smooth power that would solve the biggest problem putting a diesel on an airplane and would really boost that market!
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Cost? (Score:1)
Costs are an important question as this story happens quite often (mag trains anyone?).
For space projects the cost may not matter, since it's paid for by taxpayers. But for applications for the rest of us making this affordable is as important, if not more.
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