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."
Re:Brilliant. Go Steve! (Score:4, Insightful)
Re:Brilliant. Go Steve! (Score:5, Insightful)
BTW, couldn't you do this sort of thing with a differential?
Re:Brilliant. Go Steve! (Score:4, Insightful)
Devil is in the Practical Details (Score:5, Insightful)
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.
Re:Automatic transmissions fail before engines, no (Score:4, Insightful)
'course, that's why any sane vehicle owner drives stick...
Re:Brilliant. Go Steve! (Score:3, Insightful)
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)
The control over speed and direction is independent of the power input.
How did you think that was manipulated? Mind Control?
Re:Brilliant. Go Steve! (Score:3, Insightful)
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)
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.
Re:What concerns me (Score:3, Insightful)
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 [slashdot.org] suggests that I am totally wrong
Re:Brilliant. Go Steve! (Score:2, Insightful)
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?).
Re:Brilliant. Go Steve! (Score:5, Insightful)
Re:you already can, just use a manual gear. (Score:3, Insightful)
Where in the world are you pulling 20-30% from?
http://www.consumerreports.org/cro/cars/new-cars/news/2008/10/save-gas-and-money-with-a-stick-shift-10-08/overview/manual-vs-auto-ov.htm [consumerreports.org]
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)
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)
Re:Fuel economy (Score:2, Insightful)
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)
Re:Fuel economy (Score:5, Insightful)
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.
Re:Devil is in the Practical Details (Score:1, Insightful)
"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)
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.
Re:Brilliant. Go Steve! (Score:3, Insightful)
Re:Fuel economy (Score:3, Insightful)
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.
Re:Brilliant. Go Steve! (Score:3, Insightful)
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:Brilliant. Go Steve! (Score:5, Insightful)
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.
We don't HAVE to get rid of the clutch. (Score:3, Insightful)
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.
Sean
Re:Brilliant. Go Steve! (Score:4, Insightful)
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).
Re:That's too bad then (Score:3, Insightful)
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.
Re:Less than it appears to be (Score:2, Insightful)
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.
Re:Brilliant. Go Steve! (Score:1, Insightful)
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.
Re:Less than it appears to be (Score:1, Insightful)
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.
Do you even understand the definition of torque? (Score:3, Insightful)