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Old 15th May 2010, 23:10   #1
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Default Inventor showcases infinitely variable transmission!

Infinitely variable transmission. Imagine going from lowest gear to top gear with motor running at same speed? D-Drive is the answer. While Honda has CVT, the D-Drive is totally a revolutionary technology
Video: Is Steve Durnin's D-Drive the holy grail of infinitely variable transmissions?
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Old 16th May 2010, 07:53   #2
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Interesting.

But i wonder how it will work with a traditional engine when you drive for performance and fuel economy. I'd want the engine to be at it's lowest possible speed when cruising at 100 and the highest possible speed when i'm flooring the throttle.

Running the engine at the same speed irrespective of driving conditions would be very impractical. I doubt if this system will have a huge advantage over something like a DSG system and might be more suited for electric cars.

Shan2nu

Last edited by Shan2nu : 16th May 2010 at 07:57.
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Old 16th May 2010, 16:27   #3
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Quote:
Originally Posted by tsk1979 View Post
Infinitely variable transmission.
Pretty cool! Came here to post just this. Posting video here for easy viewing :




What i am still unclear about is - how much power will the secondary shaft need in order to manipulate the transmissions through its ratios? Is power needed for forward ratios, or is it braking (on that 2nd shaft)?

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Originally Posted by Shan2nu View Post
But i wonder how it will work with a traditional engine when you drive for performance and fuel economy.
Simply by keeping the engine at the RPM where it is most efficient (max power output + min fuel usage + min emissions)

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Originally Posted by Shan2nu View Post
I'd want the engine to be at it's lowest possible speed when cruising at 100 and the highest possible speed when i'm flooring the throttle.
You can also modulate the speed of the engine -- its just that it wont be at its "most efficient" in those cases, but it might be at its most fun / powerful / quiet etc etc.

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Originally Posted by Shan2nu View Post
Running the engine at the same speed irrespective of driving conditions would be very impractical.
Not at all -- the transmission modulates the vehicle speed (still not solidly tested though). However, if it does work, i dont see anything impractical about it.

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Originally Posted by Shan2nu View Post
I doubt if this system will have a huge advantage over something like a DSG system
When it comes to ratios - the DSG is like steps, regular manual would be like a ladder (ie gaps/drops between every gear), this is like a smooth ramp.

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Originally Posted by Shan2nu View Post
might be more suited for electric cars.
Well, electric motors are at peak efficiency at much higher in the RPM range than ICE engines. (electric @ ~80% of peak RPM).

This may or may not work to their advantage (depending on the speed/power needed on that 2nd shaft?? I still haven't completely grasped the finer details of this)

cya
R

Last edited by Rehaan : 16th May 2010 at 16:31.
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Old 16th May 2010, 20:59   #4
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Going through the comments posted in gizmag makes for more interesting (and educative) reading than watching the video!

Sutripta
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Old 16th May 2010, 23:18   #5
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Quote:
Originally Posted by Rehaan
Well, electric motors are at peak efficiency at much higher in the RPM range than ICE engines. (electric @ ~80% of peak RPM).
Actually, DC Induction motors, for example, produce max torque from zero RPM, with peak efficiency around 60-75% of max revs, as per design; ICEs, particularly gasoline engines, produce max torque around the same range. Only diesel engines are more efficient with peak torque hovering around 50-60% of rev range...

Electric motors are more like petrol engines, so you have just about the same scope of modding, which is to say quite a bit...

This is a quite intriguing concept....need to check it out in detail...planetary gears have been omnipresent in differentials since ages now (especially torsens), but in trannies...nice...
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Old 17th May 2010, 08:18   #6
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Quote:
Simply by keeping the engine at the RPM where it is most efficient (max power output + min fuel usage + min emissions)
Quote:
You can also modulate the speed of the engine -- its just that it wont be at its "most efficient" in those cases, but it might be at its most fun / powerful / quiet etc etc.
Yeah, so the engine speed will also have to change depending on the driving conditions. An engine doing low revs at a given cruising speed will be more fuel economical than it being near the peak power rpm at the same speed.

Quote:
When it comes to ratios - the DSG is like steps, regular manual would be like a ladder (ie gaps/drops between every gear), this is like a smooth ramp.
When Honda launched the CVT transmission, i thought it would be an awesome experience having a trans which can constantly change its ratios to get the best out of the engine.

Theoretically, it made a lot of sense. But when i did a back to back test of the M/T and CVT versions. The M/T was still very impressive. When overdrive tested these 2 cars. The M/T did 0-100 in 13.8 secs while the CVT version took close to 16 secs.

So, we will know how good "D-drive" is, only when they build a full sized prototype and test it against Manual/DSG units.

Shan2nu

Last edited by Shan2nu : 17th May 2010 at 08:30.
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Old 17th May 2010, 10:25   #7
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This is not really CVT, uses two cones as the friction core. D-Drive uses planetary gears somehow. I tried and tried but got lost in the tech details. From what it appears is that this system addresses the shortcomings of CVT, and is more closer to Toyota Synergy drive than the CVT.
Imagine, you need not design an engine to have a wide powerband etc, etc.,
With this tranny, even if you an give an engine a peak torque band in a narrow range, such a system will always ensure that the engine is in sweet spot. You can actually arrange the torque band such that the max FE is also achieved in that narrow band.
Currently, engine design has to see lot of things. For example a turbo diesel which spools up only after 2000rpm is considered bad for city driving.
Bring it down to 1500rpm., and you get too much torque taper off at high rpm, leading to loss of top power and lack of FE at high highway speeds.
with such a system, it will give engine designers a lot of leeway!
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Old 17th May 2010, 18:20   #8
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Quote:
This is not really CVT, uses two cones as the friction core.
I didn't say it was. But the basic principle remains the same, which is to have a stepless transition of ratios which allows the engine to stay at it's most efficient rpm all the way to the car's aerodynamic top speed.

The main difference they have mentioned is that CVT units can only vary their ratios to a fixed max/min point. To get a CVT into neutral or reverse it needs a friction plate.

In this system, you have the center gear, the planetary gear and the outer ring gear. When the planetary gear is orbiting in one direction around the center gear, the car moves forward.

When it starts orbiting the other way around, its going backwards. And when the planetary gear stops orbiting the center gear and just rotates on it's axis. It's in neutral.

The design seems perfect, but what needs to be seen now is how this actually works on a car.

Shan2nu

Last edited by Shan2nu : 17th May 2010 at 18:25.
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Old 17th May 2010, 21:32   #9
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Quote:
Originally Posted by veyron1 View Post
Actually, DC Induction motors, for example, produce max torque from zero RPM, with peak efficiency around 60-75% of max revs, as per design; ICEs, particularly gasoline engines, produce max torque around the same range. Only diesel engines are more efficient with peak torque hovering around 50-60% of rev range...

Electric motors are more like petrol engines, so you have just about the same scope of modding, which is to say quite a bit...

This is a quite intriguing concept....need to check it out in detail...planetary gears have been omnipresent in differentials since ages now (especially torsens), but in trannies...nice...
Totally confused by this post, esp. the parts I've marked in bold. Could you explain it a bit more clearly please?

Regards
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Old 18th May 2010, 04:47   #10
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@ Sutripta: What I meant by that was that DC motors (currently used for hybrid applications in cars) produce peak torque like petrol engines, with max power being produced at 65-70% of peak revs, with motor efficiency trailing off thereafter...

Electric motors are currently not at full potential. Just like petrols, whose thermal efficiencies hover at 25-30% for production motors. Lot of scope there...wonder why nobody's thought of upscaling 2 stroke diesels of yore, the ones used for marine applications with 50-60% thermal efficencies...!

Coming back to the transmissions, planetary gears have been used in differentials since forever; open differentials using sun & star or pinion type gears, and torsens with planetary gears for current torque bias ratio requirements...there have been no planetary geared transmissions so far in automotive applications; only for electric motors...
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Old 18th May 2010, 06:43   #11
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Perfection is not achievable. Hence, this is not going to save the world or anything. Furthermore, this guy needs to provide empirical evidence of efficiencies and forces involved.
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Old 18th May 2010, 18:13   #12
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Default D-Drive redux: about that holy grail thing...

I saw the original article on Gizmag an thought hey this looks neat. But looks like we'll have to keep looking for the holy grail...

Follow up article from Gizmag bursts a few bubbles:

D-Drive redux: about that holy grail thing...
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Old 18th May 2010, 21:24   #13
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Everybody is going GA GA over this guys invention. But many inventions which already ready for sell use the same tehcnology but somewhat in a different way.Use of planetary gears in a hybrid drive is not new technology.
Only difference here is if i understood it correct is that the torque on the shaft whose speed has to be varied is going to be low-although i still doubt this. Varying the shaft speed can be done by:
1)Using a hydrostatic drive (which is costly and the whole purpose of this invention will go waste if we again use a hydrostatic drive)
2)Use a battery and a variable speed motor to drive the shaft.(God knows how much power the shaft will consume and thus how efficient the whole thing would be)
3)Use a cone type or toroidal type CVT to drive this shaft. (Again this will make things complex and increase the cost)
4)Using a separate small petrol engine (whose speed can be varied)to drive the shaft(Which again is costly,complex and doesnot make sense)
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Old 18th May 2010, 21:58   #14
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Quote:
Originally Posted by ksreddy View Post
I saw the original article on Gizmag an thought hey this looks neat. But looks like we'll have to keep looking for the holy grail...

Follow up article from Gizmag bursts a few bubbles:

D-Drive redux: about that holy grail thing...
Quote:
Originally Posted by amit_purohit20 View Post
Everybody is going GA GA over this guys invention. But many inventions which already ready for sell use the same tehcnology but somewhat in a different way.Use of planetary gears in a hybrid drive is not new technology.
Only difference here is if i understood it correct is that the torque on the shaft whose speed has to be varied is going to be low-although i still doubt this. Varying the shaft speed can be done by:
1)Using a hydrostatic drive (which is costly and the whole purpose of this invention will go waste if we again use a hydrostatic drive)
2)Use a battery and a variable speed motor to drive the shaft.(God knows how much power the shaft will consume and thus how efficient the whole thing would be)
3)Use a cone type or toroidal type CVT to drive this shaft. (Again this will make things complex and increase the cost)
4)Using a separate small petrol engine (whose speed can be varied)to drive the shaft(Which again is costly,complex and doesnot make sense)
Actually media generated hype. As I said
Quote:
Originally Posted by Sutripta View Post
Going through the comments posted in gizmag makes for more interesting (and educative) reading than watching the video!
Sutripta
It is informative to read the comments to the original article,
http://infinitelyvariabletransmissio...ion-Report.pdf
and any article on the Toyota Prius transmission system.

The misnormer, in my mind, is calling a power input shaft a control shaft. In our mental image, controls require very little power themselves. This one I think will require gobs of it.

Deviating from the D-Drive
Quote:
Originally Posted by veyron1 View Post
@ Sutripta: What I meant by that was that DC motors (currently used for hybrid applications in cars) produce peak torque like petrol engines, with max power being produced at 65-70% of peak revs, with motor efficiency trailing off thereafter...

Electric motors are currently not at full potential. Just like petrols, whose thermal efficiencies hover at 25-30% for production motors. Lot of scope there...wonder why nobody's thought of upscaling 2 stroke diesels of yore, the ones used for marine applications with 50-60% thermal efficencies...!

Coming back to the transmissions, planetary gears have been used in differentials since forever; open differentials using sun & star or pinion type gears, and torsens with planetary gears for current torque bias ratio requirements...there have been no planetary geared transmissions so far in automotive applications; only for electric motors...
a) What is a DC Induction motor?
b) What is the ballpark efficiency figure for the most common electric motor in the world:- the 3 phase squirrel cage. 25 - 30%?
c) Don't think one can upscale the Wartsila two stroke Diesel!
d) Slush boxes?
e) Don't think planetary gears are central to a Torsens operation. It is a worm, which Gleason calls an elemental, IIRC.

Regards
Sutripta
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Old 19th May 2010, 11:54   #15
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Quote:
Originally Posted by Sutripta
a) What is a DC Induction motor?
b) What is the ballpark efficiency figure for the most common electric motor in the world:- the 3 phase squirrel cage. 25 - 30%?
c) Don't think one can upscale the Wartsila two stroke Diesel!
d) Slush boxes?
e) Don't think planetary gears are central to a Torsens operation. It is a worm, which Gleason calls an elemental, IIRC.
A) Ok. My bad. I was thinking of this particular concept wherein an AC induction motor, or your asynchronous/squirrel cage motor was converted to a DC motor for automotive applications...but that's not quite relevant here, sorry...
B) I would think so...but then again, production gasoline engines are less than that with BSFC of 0.4-0.6 lbs/hp/hr..close to what, 20-25%...? I would think there's a lot more to alternative power...TESLA, (motors, not Nikolas) is quite promising, don't you think...?
C) Perhaps upscaling was the wrong word...with around 50% thermal efficiency, 2 strokes need to make a desperate comeback...more so with mass production diesels.
D) Ah. Sorry. Forgot about that...automatics have always been a pain in the neck to decipher. As if conventional gearboxes weren't complex enough..however, slushboxes are quite inefficient despite the advantage with torque converters...maybe there should be a stickshift with a torque converter..nono, not the computer controlled man-o-matics with paddle shifts, but an H-gater with pure manual control...
E) The type C torsens with planetary gears (being currently used by Audi/VW, I think, for the non-haldex units) need them for uneven bias...1.5 or 1.75:1 or whatever...depending on design..but then again, I'm still a bit unsure as to the significance of the gear design.

Coming back to the D-drive...only time and detailed testing will tell...

Last edited by veyron1 : 19th May 2010 at 11:56.
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