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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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  • 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.
  • 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?
  • 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.
  • 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.

  • by Abcd1234 ( 188840 ) on Saturday May 15, 2010 @11:58AM (#32220068) Homepage

    'course, that's why any sane vehicle owner drives stick...

  • by Raffaello ( 230287 ) on Saturday May 15, 2010 @12:03PM (#32220102)

    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 .

  • Re:Its a con (Score:3, Insightful)

    by microcars ( 708223 ) on Saturday May 15, 2010 @12:09PM (#32220142) Homepage
    the speed of those 2 shafts is what controls both the output speed of the device and direction of rotation.
    The control over speed and direction is independent of the power input.
    How did you think that was manipulated? Mind Control?
  • by mfnickster ( 182520 ) on Saturday May 15, 2010 @12:15PM (#32220182)

    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 the load will always be less than full-power in either direction.

  • Re:Uh... (Score:3, Insightful)

    by Raffaello ( 230287 ) on Saturday May 15, 2010 @12:16PM (#32220190)

    Not so. The control shaft only has to spin a set of planetary gears, while the output shaft has to drive the entire vehicle. Their torque requirements are orders of magnitude different.

  • by OzPeter ( 195038 ) on Saturday May 15, 2010 @12:18PM (#32220204)

    I think you're exactly right. The invention seems to take a fixed-speed motor and a variable-speed motor of identical power and combine them into a variable-speed motor of identical power.

    However this comment below [] suggests that I am totally wrong

  • by maxume ( 22995 ) on Saturday May 15, 2010 @12:20PM (#32220222)

    My connection is too slow for video, so I have not looked at the thing, but I have seen your criticism raised elsewhere.

    Other people have mentioned that the test does not show any load, I expect that, were it truly a breakthrough, they would go ahead and show it doing some ridiculous things (hey, why not?).

  • by Mindcontrolled ( 1388007 ) on Saturday May 15, 2010 @12:21PM (#32220224)
    It is indeed similar to the planetary gear coupling boxes in parallel hybrids. And yeah, you are basically right - a 6-gear box holds you sufficiently close to the optimum rpm anyway for practical use. CVTs really shine in heavy machinery, but are not that important for personal cars. Still nice technology, though. To hell with practical importance - all hail those engineering efforts done for the heck of it!
  • by NNKK ( 218503 ) on Saturday May 15, 2010 @12:24PM (#32220248) Homepage

    Where in the world are you pulling 20-30% from? []

    The worst I see in that test is 15%, some are under 10%. And the way I see people in California drive, I'd hate to think what the roads would look like if they were worrying about shifting, too.

  • 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.

  • Re:Electric motors (Score:4, Insightful)

    by hedwards ( 940851 ) on Saturday May 15, 2010 @12:26PM (#32220266)
    That's not entirely true. Dr. Porsche a really long time ago more or less solved that problem. By inventing a vehicle that was propelled by an electric engine but powered by a gas one. Meaning that at all times the gas engine was working at it's most efficient gear ratio, but since the electric engine was driving the actual wheels it could be very efficient and give just the power needed at any given time.
  • Re:Fuel economy (Score:2, Insightful)

    by indi0144 ( 1264518 ) on Saturday May 15, 2010 @12:29PM (#32220294) Journal
    So we are in the bizarro=world where /. actually post interesting NEWS, and link to a useful article that almost everyone read?

    Think of wind farm applications!

    For being an independent plumber this guy and his invention is the living example of an "EPIC WIN"
  • Re:Electric motors (Score:3, Insightful)

    by mstrcat ( 517519 ) on Saturday May 15, 2010 @12:41PM (#32220400)
    Another type of engine that really likes to run at a constant speed are gas engines (primarily methane or propane). This sort of equipment would be a huge benefit to the natural gas industry as it would allow variable speed compression while the driving engine runs at a constant speed. Currently you have to put a generator and a variable speed electrical drive in between the driver motor and the compressor.
  • Re:Fuel economy (Score:5, Insightful)

    by Glonoinha ( 587375 ) on Saturday May 15, 2010 @12:57PM (#32220520) Journal

    Assuming 1000 miles per month (which is what most leased cars are allocated) :
    The difference between a 150mpg car and a 250mpg car is 32 gallons of gas per year per car.
    The difference between a 30mpg car and a 40mpg car is 100 gallons of gas per year per car.
    The difference between a 20mpg car and a 30mpg car is 200 gallons of gas per year per car.
    The difference between a 15mpg car and a 25mpg car is 320 gallons of gas per year per car.
    The difference between a 12mpg car and a 22mpg car is 450 gallons of gas per year per car.
    The difference between a 10mpg car and a 20mpg car is 600 gallons of gas per year per car.

    Read from bottom up, you see the point of diminishing returns.

    If car companies would focus on the right range (forget about exotic expensive 150+ mpg carbon fiber hybrids that hold two people, focus on 30+mpg vehicles that hold a family and gear) they would have a LOT more impact. I don't necessarily agree with the way cash for clunkers was handled, but in the cases where people traded in a 12 mpg car and drove off in a 22mpg car - it makes a BIG difference.

  • by Anonymous Coward on Saturday May 15, 2010 @01:50PM (#32220892)

    "This is why we need to support the math, science and physics departments everywhere"

    I think it means we need to train more people to be plumbers.

  • Re:Fuel economy (Score:1, Insightful)

    by Anonymous Coward on Saturday May 15, 2010 @03:03PM (#32221342)

    To demonstrate this, you can also look at a graph of f(x)=1/x where x = fuel efficiency in mpg, f(x) = gallons of fuel per mile. The largest slopes (changes in gpm/mpg) are near zero (i.e. the car has terrible fuel economy so even small differences in efficiency effect a large decrease in the amount of fuel used per mile) happen near zero, whereas the smallest slopes are near infinity (i.e. the car has awesome fuel economy so a small difference in efficiency effects almost no change in fuel used per mile). al-Khwrizm probably recognized that it would be cool if he didn't need to write out big lists of calculations if he just wanted to demonstrate a fact like the one you've pointed out.

    It's also worth noting that the point of diminishing returns is different for different people, so no that's not obvious.

  • by Alef ( 605149 ) on Saturday May 15, 2010 @03:12PM (#32221400)
    I did watch video in TFA, and it doesn't make it clear how this device works. It does suggest, however, that they haven't actually made any real measurements yet, so whether it works as they think remains to be seen. Regardless, what I instantly dismissed was the GGP's claim that combining two inputs to an output is anything new.
  • Re:Fuel economy (Score:3, Insightful)

    by jeff4747 ( 256583 ) on Saturday May 15, 2010 @03:39PM (#32221552)

    At 3 per gallon, that only saved me $750 dollars. How much of my tax money did the government spend on it though? Oops.

    Fortunately for supporters of the program, the goal wasn't just to save you money on gas. That new car also resulted in a bunch of taxes for the government, in that auto workers were employed and getting taxed on their income. And still buying stuff, resulting in more taxes and employment, and then those people bought stuff (and so on, and so on)

    Too many economic arguments are overly-simplified for ideological purposes.

  • by Alef ( 605149 ) on Saturday May 15, 2010 @05:08PM (#32222072)

    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.

  • by egcagrac0 ( 1410377 ) on Saturday May 15, 2010 @06:07PM (#32222436)

    it may increase the life of the car/machine.

    Sadly, this may kill the project.

    It seems that manufacturers don't want to build things that last forever. Planned obsolescence is the current fashion.

  • 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.

  • by ray-auch ( 454705 ) on Saturday May 15, 2010 @06:31PM (#32222574)

    It also removes a redundant control method.

    Throttle stuck ? - stamp on the clutch (and the brake) no problem.

    This device has a "powered neutral" determined by getting two input shafts spinning at precisely the same speed - otherwise you are moving. You aren't going to manage that manually so you are likely looking at some form of electronic (+ software) implemented "neutral" switch. You'd better be worrying about how long before _that_ goes wrong - because it's going to be fun controlling the car when it does (without a clutch, remember).

  • by torkus ( 1133985 ) on Saturday May 15, 2010 @07:25PM (#32222930)

    So the large number of people in the US with a new car fetish who trade them in ever 2-4 years...or those leasing cars who get a new one every 3 years...will be forced to...what?

    Cars are already far more reliable than they were 15 years ago and manufacturers strive for increasing reliability because it's a key selling point...even though people often don't keep the car long enough for it to matter. If you made the a car nearly service free for 5 years then you can sell include "free service" for 5 years with every car like some manufacturers already do.

    Conspiracy theory doesn't hold water on this one. I'm much more interested in how it actually works and the mechanical stresses involved. Is it reasonably practical to scale up to 100HP? 200HP? 300+HP? If it's mechanically simple, cheap to make, has low losses it could quite handily replace an automatic transmission. Nissan has gone CVT on most/all of it's cars already.

    And for CVT in general, it may be better in industrial uses but it has definite applications in consumers applications. It can definitely give better performance for a given engine.

  • by Scytheford ( 958819 ) on Saturday May 15, 2010 @10:15PM (#32223934)

    I AM a ME and I share some of your concern. I'm failing to see how the sun gear on the output end wouldn't need to be able to match the torque difference between the output ring and the input from the planetary gear.

    However I'm thinking that if the control shaft (which drives the sun gear on the output side) were driven with a worm drive it would annul most of the back-torque caused by the output planetary using the sun gear as a fulcrum to drive the output ring.

    I'm cautiously optimistic, but also slightly disappointed that this didn't come about 40 years ago when it would've made a difference. We're too close to the dawn of the electric age for this to have much of an impact in the most common applications.

  • by Anonymous Coward on Sunday May 16, 2010 @04:38PM (#32229804)

    Wrong. Remember how Detroit was sunk? Yeah, better quality. Today's japanese cars are functioning to the manufacturer's specifications with 100,000 miles on the odometer and they work pretty well with 250,000 miles so no: the auto industry is an all-out war and the good brands really try to build better cars. There *is* competition.

  • by Anonymous Coward on Sunday May 16, 2010 @06:56PM (#32230948)

    I was thinking nearly the same thing:

    Suppose this "transmission" were powered by some powerful engine on the input side and on the output side there was something being held at a stop. Wouldn't most of the torque be directed out the control positions (the rod at a standstill would start turning, unless an equal force in the opposite direction was there)?

    Given that insight, it appears that the necessary torque on both the input and control position seem to need to be in the same ballpark so that they do not overpower each other when attempting to rotate the output.

    To be useful as a transmission you would need a design that would under minimal power convert X input rpms into Y output rpms. A manual transmission does this without any external power by swapping gears (outside of the power required to actually swap the gears, provided by the person operating the transmission; as IANAM, I cannot explain an automatic so easily, but I would assume that they work similarly, once set in a particular gear ratio there doesn't need any additional power to stay in that gear). A CVT requires constant power to maintain a particular gear ratio (otherwise it could slip into one of less resistance), but that power is orders of magnitude less than what can actually be transmitted through the device.

    It could probably be geared so that the control is done via a worm gear, to reduce the torque required to maintain a particular gear ratio, but you would still need a transmission to control the speed at which the worm gear is turned (and I am not sure if there is in fact less power required for this overall or not). If this was possible, then this system could be used to increase the available torque of an existing CVT, by using the CVT to adjust the speed of the control to the d-drive (splitting off a fraction of the original engine power to drive the cvt, then using the rest on the input for the device). Note that I am a mathematician with little experience in power calculations so value my thoughts with that in mind.

  • by George_Ou ( 849225 ) on Monday May 17, 2010 @03:46AM (#32234430)
    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 which results in the same torque.

How many NASA managers does it take to screw in a lightbulb? "That's a known problem... don't worry about it."