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Transportation Hardware

Inventor Demonstrates Infinitely Variable Transmission 609

ElectricSteve writes with this excerpt from Gizmag: "Ready for a bit of a mental mechanical challenge? Try your hand at understanding how the D-Drive works. Steve Durnin's ingenious new gearbox design is infinitely variable — that is, with your motor running at a constant speed, the D-Drive transmission can smoothly transition from top gear all the way through neutral and into reverse. It doesn't need a clutch, it doesn't use any friction drive components, and the power is always transmitted through strong, reliable gear teeth. In fact, it's a potential revolution in transmission technology."
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Inventor Demonstrates Infinitely Variable Transmission

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  • Brilliant. Go Steve! (Score:5, Interesting)

    by eldavojohn ( 898314 ) * <> on Saturday May 15, 2010 @11:30AM (#32219856) Journal
    The real icing on the cake is (as mentioned near the end) the secondary drive doesn't require a whole lot of power so it can be run by a flywheel. Infinite torque? Frictionless? This is almost too good to be true, there has to be some catch. Like the primary input drive requires more energy than they expected but I can't see it--although I'm not a mechanical engineer.

    This is the kind of thing you like to see -- I hope this man has all the capital he needs and gets that prototype up and running for demonstrations. Plus it's a small time plumber inventor ... these are the kind of news stories an engineer loves to read about.
    • by Mindcontrolled ( 1388007 ) on Saturday May 15, 2010 @11:45AM (#32219942)
      Well, obviously this is not "frictionless" - it just appears not to use friction as the main force of transmission, like friction-cone type CVTs do. There are other types of CVTs that do not use friction - for example chain-driven CVTs or hydraulic-type CVTs. Theoretical infinite torque is also not exactly new - look at hydristors, for example. I'd love to see more technical detail about what the guy actually invented there, TFA is not exactly helpful when it comes to the inner workings of his gearbox.
      • Re: (Score:3, Informative)

        by Raffaello ( 230287 )

        watch the video half way down TFA- it shows in pretty fair detail how the d-drive transmission works.

        • Re: (Score:3, Funny)

          Yeah, thanks - I missed that video. I am slightly too hungover to wrap my head around a video demonstration at the moment, though... Gotta have a look if his patent is already published later.
    • by FooAtWFU ( 699187 ) on Saturday May 15, 2010 @11:48AM (#32219964) Homepage
      By "frictionless" I assume they're talking about something to do with the clutch, where you have two plates that you can jam against each other to transmit power via friction (and if you take them a little distance apart you they have a little bit of slip to them, so that during a gear change can the engine's speed will be smoothly met by the friction until it matches the drive-shaft's speed without any terrible lurch which would damage everything). This thing still has normal mechanical friction, as any set of gears would, but doesn't have any component explicitly designed for friction.
      • by Mindcontrolled ( 1388007 ) on Saturday May 15, 2010 @11:54AM (#32220028)
        They are actually comparing it to other times of CVTs, which use friction belts driving a pair of cones. Nothing to do with the clutch. The device from TFA uses only gears, in particular a set of planetary gears, so they say that the advantage would be no danger of slippage compared to friction driven CVTs. From what I know, in the usual designs, the slippage problem is not really limiting anyway, though.
        • Re: (Score:3, Insightful)

          by Raffaello ( 230287 )

          Slippage limits torque. the whole advantage of this system is that it allows infinitely variable output - from full speed reverse through neutral, to full speed forward, all with full torque limited only by the size of the toothed gears used. All power transmission in this device happens through toothed gears. There are no belts, friction plates, clutches, etc - all toothed gears and only toothed gears, with zero slippage, full torque, and infinitely variable output .

          • by Mindcontrolled ( 1388007 ) on Saturday May 15, 2010 @12:10PM (#32220150)
            Yeah, but that's basically the working principle of any planetary gear system. If you don't hold any of the components locked in a planetary gear, you can configure the output to be proportional to the ration of the inputs. Combine a CVT with a planetary, and you get an infinitely variable transmission. That's used in hybrid vehicles all the time, and doable with gears only, not using friction components. From quickly skimming over the video, I definitely see a planetary gear setup there. As I said above, I'd love to see more technical detail on that one, TFA does not really make clear what is actually new about this.
            • by MachDelta ( 704883 ) on Saturday May 15, 2010 @12:29PM (#32220298)

              The new aspect is that this planetary gearset actually has TWO inputs, and the output is determined by the *difference* in speeds between the two. That's how it can go from reverse to forward seamlessly. V1 > V2 is Forward, V1 V2 is Reverse, V1 = V2 is Neutral. Assuming there are no practical limits on the velocity of either input, the possible difference between them is infinite.

              Personally I find this really exciting, because i've always been in love with the idea of a variable transmission. Ignoring electric motors for a minute, there are some absolutely INSANE things you can do to a small motor with cams, turbocharging, etc, to extract absolutely massive amounts of power from teeny engines. Like, 1000+hp from sub 2 litre motors. The problem is they end up being extremely peaky (power is only made at a narrow RPM band, or a terribly high one)... but with a variable transmission you can let the engine hunker down in it's sweet spot and let the tranny worry about all the fiddly bits. Hell, you can even do the same thing with a big engine... I wonder if its possible to make five figures of power from a 7 litre? With this we just might find out.

              • by Alef ( 605149 ) on Saturday May 15, 2010 @12:53PM (#32220500)

                The new aspect is that this planetary gearset actually has TWO inputs, and the output is determined by the *difference* in speeds between the two.

                You just stated the definition of a differential gear. It is not new in any way, and describes exactly how a planetary gear works and is normally used. For a real world example take a look at the Hybrid Synergy Drive [] used in Toyota Prius. It has precisely that: A planetary gear with two inputs summing up to one output, allowing the engine to operate at optimal rpm regardless of wheel speed.

                • Re: (Score:3, Interesting)

                  by Nazlfrag ( 1035012 )

                  Not at all. This device has three inputs, GP neglected to mention the main engine. It uses two smaller inputs to affect the main larger input. The prius balances two engines of rougly equal size. This controls a single engine with two much smaller ones. It seems to be a novel and unique transmission.

                  • Re: (Score:3, Insightful)

                    by Alef ( 605149 )

                    Whether you add two or three power flows makes little difference to the principle of operation. You do not escape the fact that the "control" engine(s) will be experiencing a proportional amount of torque as the main one.

                    It seems to be a novel and unique transmission.

                    Well, many things seem novel and unique when you lack the relevant expertise.

              • Re: (Score:3, Informative)

                I hope you're not saying what I think you're saying. Transmissions CAN'T increase horsepower. All they do is keep the engine from stalling by trading speed for torque. Horsepower is rotational speed X torque so the total horsepower doesn't change just the ratio of torque to rotational speed.

                I think the transmission design is very cool and I'm amazed that someone can still come up with new ways to combine gears that haven't been done before. In fact, there was a post claiming someone had come up with a s

              • by MostAwesomeDude ( 980382 ) on Saturday May 15, 2010 @03:34PM (#32221532) Homepage

                hunker down in its sweet spot and let the tranny worry about all the fiddly bits

                I've spent too long on the Internets, apparently.

              • aka differential (Score:4, Interesting)

                by bzipitidoo ( 647217 ) <> on Saturday May 15, 2010 @07:29PM (#32222956) Journal

                Not really new. Model T's had differentials. And why are differentials called that? Because they "difference", as in subtraction, rather like Babbage's difference engine. All this thing is doing is distributing the speeds of 3 shafts so any 2 add up to the speed of the other. The wonder is that apparently no one has applied this idea in a transmission. Maybe that's because there's some fundamental problem, like, oh, how to drive 2 shafts so that the 3rd one can be precisely controlled? I suspect the electric motor used to drive the 2nd shaft may need to be so powerful that this idea may prove impractical. The inventor tries to get around that problem by having that electric motor act more as a brake, always running at negative rpm, so to speak. Notice that "top gear" is the 2nd shaft being locked to a speed of 0 rpm. The 2nd shaft could be run forward for an even taller top, but that would take real power, so this invention doesn't do that. We can hope that it works.

                Perhaps most people on Slashdot have never played around with a differential? Jack up the rear wheels of a manual transmission, rear wheel drive car, and see what happens when you spin one wheel by hand. If the transmission is in gear (engine off, of course), the other rear wheel will spin the opposite direction, at the same speed. If the transmission is in neutral, the opposite wheel and the drive shaft will spin at some rate that together adds up to the speed you're spinning. Usually, the drive shaft will spin and the opposite wheel won't, because the wheel has the greater mass and inertia.

                Also perhaps most people here have never had the experience of getting one rear wheel of such a car on extremely slippery ice? I'm talking ice right at 0 C, with water on top. (Well, if that's what road conditions are like, just stay home that day.) You might think you're okay if at least one wheel can get traction. Nope! If your vehicle doesn't have differential lock, you're stuck. The one wheel on a dry surface won't move, while the one on ice spins twice as fast.

            • Re: (Score:3, Interesting)

              Can you elaborate? You say "combine a CVT with a planetary...not using friction components" but I was under the impression that a standard CVT (with 2 cones and a belt? That's the kind I know about) does use friction components, whereas this new design doesn't.

              What I don't get is how exactly this is distinct from a differential gear.
    • by camperdave ( 969942 ) on Saturday May 15, 2010 @11:52AM (#32220004) Journal
      Well, one potential flaw is the eccentrically mounted components. Unless properly counterweighted, at high speed this will cause a lot of vibration.

      BTW, couldn't you do this sort of thing with a differential?
    • Re: (Score:3, Interesting)

      by roman_mir ( 125474 )

      It is a very interesting approach, the problem that may happen (I don't know, just guessing here) is to locking the lower shaft while trying to go full force, isn't the entire premise of friction basically shifted (sorry for the pun) to the device that will stop or let go of the lower shaft, which needs to be stopped for the torque to be transmitted to the wheels for example? So there are these 2 small black gears if you look at the video, these gears are perpendicular to the lower shaft, sitting on it sid

      • Re: (Score:3, Insightful)

        by mfnickster ( 182520 )

        isn't the entire premise of friction basically shifted (sorry for the pun) to the device that will stop or let go of the lower shaft, which needs to be stopped for the torque to be transmitted to the wheels for example?

        I'm no engineer either, but AFAICS the two counter-rotating shafts share the load between them, and the forward/reverse motion is the difference of the two.

        So if one shaft is strong enough to transmit full torque from input to output, there's no problem if you split it between them because

    • by Stan Vassilev ( 939229 ) on Saturday May 15, 2010 @01:28PM (#32220738)

      The real icing on the cake is (as mentioned near the end) the secondary drive doesn't require a whole lot of power so it can be run by a flywheel

      This is something that bothers me as I look at this demo. The secondary drive doesn't require a whole lot of power, because there is literally nothing attached to the output to counteract the little motor's selected ratio.

      To simulate the forces of what it'd be to have a car attached on the output, you can just use your hand and try to hold the output from moving, while the ratio is not in neutral. If there is a weaker motor and a stronger motor, what do you think will happen? The stronger motor may feel a pinch, and the small motor will be completely unable to stop the output from distorting the ratios, making the entire setup unusable.

      Now, I hope I'm wrong, but there better be something hidden from view That Changes Everything.

  • Fuel economy (Score:4, Interesting)

    by Krneki ( 1192201 ) on Saturday May 15, 2010 @11:32AM (#32219868)
    If this gearbox works we could see a massive decrease in fuel consumption and much better power delivery in our cars.
    Because right now the gearboxes are rubbish, they haven't evolved much in the last decades.
  • Lucky for him ICE cars will probably still be around for the next 20 years. Electric motor cars don't normally need to change gears.
  • So... (Score:4, Interesting)

    by Max Romantschuk ( 132276 ) <> on Saturday May 15, 2010 @11:33AM (#32219880) Homepage

    ...when can I fit this on my bicycle?

    (I'm serious. Proceeding to read TFA...)

    • A few notes... (Score:4, Interesting)

      by Max Romantschuk ( 132276 ) <> on Saturday May 15, 2010 @11:48AM (#32219962) Homepage

      While quite elegant, this solution requires power input... So not so great on a bicycle...

      And as far as cars go, you have to spin a shaft in order to achieve neutral. Which means that you still need a clutch or something for a car to be safe. (If the engine's running and the electric motor spinning the shaft fails the car will go forward... Not nice.)

      (Am I the only one who thought that the TFA's statement that understanding these mechanics is dumbing it down? I think it's simple, honestly. I'm not claiming I would have invented it, but I do understand the principle...)

  • by Freshly Exhumed ( 105597 ) on Saturday May 15, 2010 @11:45AM (#32219944) Homepage

    The greatest limitation on today's CVTs is the lack of sufficiently strong materials for the belts. While research and development has already yielded marketable CVTs, they are limited to being paired with relatively low displacement, low horsepower, low torque engines for durability purposes. Your father's Oldsmobile's honkin' huge Rocket V-8 or your cousin Bubba's new pickup truck's V-10 would likely tear any of those CVT belts to shreds. Supposing that this new design is strong enough, those engine pairing limitations could be done away with once and for all.

  • Hydrostatics... (Score:3, Informative)

    by crankshot999 ( 975406 ) <> on Saturday May 15, 2010 @11:46AM (#32219950)
    Several tractors I have owned have hydrostatic transmissions. These are also infinitely variable, but they use a hydraulic pump and motor to achieve it. They provide very high torque and excellent power transmission. I always wondered why they were never used in cars.
    • Re:Hydrostatics... (Score:5, Informative)

      by Anonymous Coward on Saturday May 15, 2010 @12:22PM (#32220236)

      Fluid friction losses. Recirculating a fluid via a pump in a closed system actually makes a bit of heat, especially when there's a bit of load on it. Works great when something can be built big and doesn't need to go very fast (like the tractor application you mentioned, also used a lot in earth moving equipment and fork-lifts), but when having something that goes fast - not so much. Also if you go too fast, you're either going to have some kind of undesirable hammering or cavitation at a certain point depending on what kind of pump you use to provide hydraulic power.

      Some air motors use a tilt-block that does something similar as well in regards to infinite variable speeds, but they're not so much about efficiency as about being able to control speed in industrial environments where electric motors aren't always desired. (Like working around water or in a no-spark environment.)

    • Re:Hydrostatics... (Score:5, Interesting)

      by caseih ( 160668 ) on Saturday May 15, 2010 @01:27PM (#32220728)

      It's loud. Plus you have to have a heavy hydraulic system (pump, oil reservoir, valving, etc). In practice an electric motor gives you most of the same benefits of a hydrostatic system, but it's a lot lighter and doesn't require an oil system. Of course batteries are heavy, but aren't strictly needed (as in a locomotive).

      A few years ago I heard of a design that used small hydraulic motors connected to each car wheel via clutches that would efficiently overcome the propensity of a differential to send power where you don't need it. Basically when slippage was detected, the clutches would engage and the faster wheel would act as a pump, sending fluid to drive the other wheel. The beauty was that if you tied all four wheels into the same system, you could get on-demand four wheel drive as well.

      Another prototype I heard of used a hydrostatic system to charge up a nitrogen accumulator in a form of regenerative braking system.

      Hydrostatics also has limitations in the amount of power you can transmit. Every large combine harvester we've ever owned has had a hydrostatic transmission, but no tractor ever has had. Combines typically don't pull things; driving power is minimal compared to the power consumed by threshing. Whereas in a tractor, it's all about driving power (outside of PTO applications). You just can't really put 500 HP of pulling power through hydrostatics. Most hydraulic motors are gear motors, which means the oil spins little gears. Under high load, oil slips past the gears without turning them. Compare that to electric where on a daily basis Locomotives pass thousands of horsepower from big diesel engines to the wheels with electric motors.

    • Re: (Score:3, Informative)

      by Mashiki ( 184564 )

      They were used in cars, back in the '60's. The actual name of the transmission escapes me right now, but they came in both mechanical and hydraulic flavors. One gave you more torque, the other more power. Bah, and I'm sure they weren't called hydrostatic, but they could do exactly the same things. GM put them on their super-blocks.

  • by stevel ( 64802 ) * on Saturday May 15, 2010 @11:46AM (#32219954) Homepage

    I think the weakness in this design is the need to rotate the "bottom" shaft at a speed equal to the input shaft for neutral. While indeed it doesn't need a lot of power, it's a lot of rotation where, in competing designs, a clutch disengages or the drive motor is idling. I could see a lot of things going wrong if the synchronization was imperfect, or if something went wrong.

    How do you start this up from a dead stop? Somehow you have to exactly match the shaft rotation speeds to keep it in neutral before you start moving forward, otherwise there will be a lurch.

    I look forward to seeing how this is developed further. It has a lot of potential.

  • by BoRegardless ( 721219 ) on Saturday May 15, 2010 @11:54AM (#32220034)

    It works as a demo very well I , as an ME agree.

    The big issue in science and engineering is ALWAYS reduction to practice. The inventor acknowledges this and is working with an engineering firm to make a practical pseudo-production testing model. When you have no clutches, the lack of shock loading means the size of gears and the housing can be substantially reduced, since there won't be an engine load shock issue. There can be issues of loads when parked, though, when another car bumps yours. The other issue is how do you tow such a car when the engine fails or you want to tow it behind a motor home? There may still need to be a "cog" connection for towing.

    Issues involved in getting it into a small, produceable and cost effective prototype will tax the engineers. If they can do it, there will be applications in many different fields.

    Given that the gear ration can be set by controlling the small electric motor speed, it can be integrated with other electronic control systems easily.

    I have to hand it to the guy for coming up with a very clever implementation. This is why we need to support the math, science and physics departments everywhere, because in the end, the world is a physical place and the countries who prosper the most will be the ones with the most technologically up-to-date innovators.

  • Newton's Third Law? (Score:3, Interesting)

    by cunniff ( 264218 ) on Saturday May 15, 2010 @11:55AM (#32220044) Homepage

    For every action, there is an equal an opposite reaction. So, when your monster torque motor is spinning the input shaft, surely it is pushing against the counterspinning shafts with exactly that amount of power? In other words - won't the mechanism (electric motor, flywheel, etc.) that keeps the counterspinning shafts running at the desired speed ratios have to overcome this reaction? It's possible that the frictional and mass inertia of the system helps some, but how much?

    I'm not an ME, but the explanation of what the required control motor power is relative to input motor power is very thin here. Be very interesting to see what the detailed input / output / control torque & power measurements end up being.

  • by caseih ( 160668 ) on Saturday May 15, 2010 @12:05PM (#32220116)

    At first blush, I'd say that both Toyota and John Deere have already produced something similar. What he appears to have, however, is a system that can smoothly transition (with power) through neutral and reverse. That indeed could be the cool, patented part, as the rest of his transmission is pretty well understood and actually in production already in many of the applications they list for their invention. I don't see any patent application listed, so I can't tell for sure exactly where his breakthrough is.

    Here's the fundamental principle by which his transmission works, though: Basically the idea is you supply driving power to a planetary gear system and then use another variable system such as an electronic motor or, in John Deere's case, a hydraulic motor, to take speed (but not power) away from the output shaft by spinning part of the planetary system. If you understand how a planetary gearbox works, this makes sense. So in John Deere's case, the less-efficient hydraulic motor uses a tiny amount of power to control how the actual, geared, power is transmitted to the wheels. Using this system JD has a completely variable system with a particular gear range (this is a tractor after all) that has a powered neutral stop. In the pictures and video you'll note he has two electric motors that control the ratio.

    Toyota does something similar with their hybrids, although it's more of a way to efficiently (and brilliantly, I might add) blend the gasoline motor's power with the electric system in an infinitely variable way.

    Another way of implementing an IVT, though I don't think it is as efficient, is to use a differential. Power comes in the normal part of the differential (IE spinning the entire gear assembly), and then power comes out one side, and an electric or hydraulic motor attached to the other side (Where the wheels would normally go). You can then use the motor to change the apparent gear ratio, and even reverse it.

    • by caseih ( 160668 ) on Saturday May 15, 2010 @12:22PM (#32220234)

      Hate to reply to my own post, but here is a fairly detailed explanation of John Deere's IVT: [] . The relevant part is "The John Deere IVT uses a hydromechanical, power-splitting design where a portion of the power is transmitted mechanically and a portion hydrostatically. A hydromechanical transmission is more efficient than a purely hydrostatic transmission because gears carry power more efficiently than a hydraulic pump and motor. By careful selection of the gearing, the John Deere IVT carries a maximum of the power mechanically both at normal field working speeds and at transport speeds, taking maximum advantage of the higher mechanical efficiency while providing the control and versatility of a hydrostatic." And of course this power-splitting is done via a planetary gear system.

      I say this not to take away from the D-Drive's awesomeness (John Deere doesn't do reverse without shifting a gear), but to help offer explanations of how it actually works.

  • by Mawbid ( 3993 ) on Saturday May 15, 2010 @12:21PM (#32220228)

    The Thompson coupling [] was invented not long ago, and I remember being amazed that there was anything new to be done in the area of mechanical power transmission. And now this. Are we all done now, or is there more still?

    • Re: (Score:3, Informative)

      by Vireo ( 190514 )

      Well this D-Drive resembles the Thompson coupling in that they both seem new but they're really not. The Thomson coupling is a (admittedly nicely packaged) double cardan joint, while the D-Drive is a powered-planetary, already used in infinitely variable transmissions before. I'm not sure if that particular arrangement existed before, and it's nice to see that novelty is still possible in basic mechanics, but similar devices with powered neutral already exist (for example in tractors).

  • something to hide? (Score:5, Insightful)

    by v1 ( 525388 ) on Saturday May 15, 2010 @12:25PM (#32220260) Homepage Journal

    I watched with interest through 3/4 of the video as they continuously refused to show the back side of the model, just loosely discussing the "control shafts" and couldn't get it out of my mind
    "pay no attention to the man behind the curtain".

    Then finally at the end they showed the back and surprise, there's another motor there, but trying to explain it off that this motor requires far less energy than you're going to gain by using the rest of the system. Maybe this is true, but that's a poor way to present the design, by hiding a serious concern until the last second.

    As they wrapped up the video they did admit that this little kink is going to be the determining factor in whether or not it's a useful design. "Why can't they just tap some of the power off the input shaft to manage the control rods?" I thought. Then it occurred to me, the speed would need to be continuously variable, and that's the whole problem they're trying to solve. So, what we have here is a continuously variable mechanism, so long as we can already provide a continuously variable mechanism. (all his D-Drive needs to complete it is, another D-Drive, which would of course need another D-Drive....) Sounds terribly recursive to me. But he didn't go into any detail as to the requirements of this control system, but from what I can tell, it needs to be continuously variable also. He dismissed it as being easy to achieve with something such as an electric motor, which one could argue the same is true of his entire invention...

    We'll see. I'll remain skeptical until his design is complete, including the nagging little details of running the control shafts. But really it's an excellent idea even with this problem. It's solved the larger portion of the problem. One other thing that also came to mind is balance. The orbital gears could really get whipping around the sun gear, they'll have to be balanced. Using orbital gears itself at high torque will create new problems also. I'm no mechanical engineer but I also see a potential problem there with torque on the position of the planetary gears since the shaft isn't fixed. You don't usually see floating gears in transmissions.

    • by T Murphy ( 1054674 ) on Saturday May 15, 2010 @02:21PM (#32221102) Journal

      Then finally at the end they showed the back and surprise, there's another motor there

      They mention the electric motor 2 minutes in, and they constantly talk about driving the bottom shaft, implying you are providing some sort of power input. They didn't show the back of the device for a while because looking at an electric motor is less helpful than seeing the output when trying to understand how the thing works.

      As they wrapped up the video they did admit that this little kink is going to be the determining factor in whether or not it's a useful design

      They spent most of the video trying to explain how the device works, so understandably they get to the application stuff only at the end. He just showed the device working perfectly fine with an electric motor- you don't need to work out a continuously variable input from the main motor unless you really want to. As for the efficiency, the input power is exactly the main concern, but it sounds perfectly plausible for this input to require minimal power. As they mention, the electric motor isn't seeing any of the main motor's power, so the required power for it can be very small.

      I agree vibration issues and robustness have yet to be seen, but the device is simple enough it should be feasible. Engineering this from a demo to a working transmission for a full-size motor can be as much work as developing it in the first place, so it may be a while before we see where this goes.

  • Video of D-Drive (Score:3, Informative)

    by SJ2000 ( 1128057 ) on Saturday May 15, 2010 @12:47PM (#32220438) Homepage
  • by Whuffo ( 1043790 ) on Saturday May 15, 2010 @03:05PM (#32221362) Homepage Journal

    The largest value of this device is in its "wow, how does that thing work?" design. By baffling the onlooker and also describing the widget very carefully the illusion of a wonderfully useful device can be created.

    It has a problem in the real world, though. The reaction torque is equal to the working torque - and the reaction torque path runs through that "secondary control shaft." This will become obvious as soon as he tries to transmit some significant power through his device. What he's showing isn't a new invention at all, it's just a mechanical "summer" that adds the inputs from two input shafts. All that's new here is some fancy handwaving and creative description.

    It might be good enough to fool some people but Mother Nature and those who paid attention in school aren't fooled. Maybe if / when he actually tries to transmit some power through his "invention" and the control motor just spins backwards he'll "discover" a source of electrical energy?

    • by Bigjeff5 ( 1143585 ) on Sunday May 16, 2010 @03:50AM (#32225706)

      The reaction torque is equal to the working torque...

      No, it isn't.

      - and the reaction torque path runs through that "secondary control shaft."

      If either were the case, then as the secondary motor spun up either the drive motor would have to slow down or the total speed of the two drive shafts would change.

      The drive motor never changes speed, and neither does the total speed of the two drive shafts.

      In your scenario, the top shaft would not slow down as the bottom shaft sped up, it would simply keep spinning at the same speed. To get the system in neutral, the control shaft (and therefore the control motor that drives it) would have to spin at the same speed as the drive motor and shaft. In order to make the output shaft spin in reverse, the control motor would have to be twice the size of the drive motor!

      That is obviously not what is happening, so now you have to look at what is happening. The control motor is spinning the planetary gears around the drive motor's ring gear and the output shaft's ring gear, effectively neutering all the torque the drive motor is applying. This is exactly the same as applying a clutch, without needing two friction plates - just a spinning motor and some planetary gears. When the control motor spins faster, the effect is to reverse the direction that the planetary gears need to spin to compensate for the torque being applied by the drive motor.

      The only things the control motor is applying any power to are the planetary gears, and then only to affect their relationship to each other. It is completely isolated from the torque conversion loop, even though it looks like it is right in the middle of it. When the control motor is spinning at full speed (reverse), all of the power is still being supplied by the drive motor. You could swap out a bigger motor on the drive side and apply a load on the output side and the results would be identical. So long as the RPMs didn't change with the larger motor you wouldn't have to change any gearing on the control motor or any of the planetary gears.

      • So you think the reaction torque is different than the working torque? Do you even understand the definition of torque? Torque is the effective radius multiplied by the force. Your reaction shaft might be geared lower so that it doesn't require as much force to push, but its the lower gear has a smaller effective radius. These two things negate each other and you still end up with the same torque. The only difference is the speed of your output. A higher output RPM is balanced by the reduced force whi
  • by jafo ( 11982 ) * on Saturday May 15, 2010 @06:17PM (#32222498) Homepage
    A lot of the replies bring up problems of going completely with this solution (how do you get it started if you need things spinning first, how do you tow a car with one of these). Admittedly not an optimal solution, but a very effective one could be to still have a clutch in the mix for some of these situations. Considering that the clutch would only be used fairly rarely, and could be engaged while the rest of the system is in neutral (meaning it's fairly low engagement load), it could be much smaller and have a much longer life than the typical clutch arrangement.

    Clutches don't have to have a short life. The clutch in one of my cars that I've owned since 20 miles now has just under 200K miles on it. I've been expecting to have to replace it for a decade. But, the way I drive it seems to pamper the clutch.


"Let every man teach his son, teach his daughter, that labor is honorable." -- Robert G. Ingersoll