Get ready for a transmission revolution: Infinitely variable D-Drive

[Miramonti]

Gizmag link

youtube video

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 - it could be pretty much the holy grail of gearboxes... if only it wasn't so diabolically hard to explain. We flew to Australia's Gold Coast to take a close look at the D-Drive - and it looks to us like Durnin has pulled a rabbit out of his hat. Check out the video after the jump and see if you can work out if there's a catch.

Props to Loz Blain for his grasp on this story. It looks like Durbin created an engineering masterpiece. Not bad for a plumber!

 

[EightySix Four]

It's awesome until you look at it closely and see that the second (electric) motor has to produce as much torque as the gas motor it is connected to.

 

[StageLeft]

Skimming this. So it replaces the possible problems with a CVT by introducing a completely second electric motor? Is that right?

 

[ShawnD1]

I hope it all works out. The inventor seems like a reasonable guy, no crackpot claims, seems to have a solid understanding of how this could be used.

He mentioned that the secondary shaft would need an electric motor to drive it, and it looks like the motors work together rather than against each other, so it's almost like a parallel hybrid system. Mechanical things are beyond my comprehension, so I don't really know if I'm right about this.

I don't think we'll ever top the simplicity of a plain jane manual transmission. They're not always the most efficient, but they're indestructible and cheap. The regular CVT is a very basic transmission with very few parts, but Nissan still charges an extra $1300 CDN if you want one. This guy's D-Drive looks way more complicated than a normal CVT, so how much do you think it would cost?

 

[jpeyton]

I'll get ready for it in 5 years, once it is field tested and ready for market.

 

[Hyperlite]

It's awesome until you look at it closely and see that the second (electric) motor has to produce as much torque as the gas motor it is connected to.

This is addressed in the video. "the electric input only needs to produce a fraction of the power of the mainline engine, because it doesn't have to fight the resistance of that engine, only spin the shaft."


I'm not sure that makes sense to me, but that's what the man says.

 

[Fenixgoon]

This is addressed in the video. "the electric input only needs to produce a fraction of the power of the mainline engine, because it doesn't have to fight the resistance of that engine, only spin the shaft."


I'm not sure that makes sense to me, but that's what the man says.

power != torque

 

[EightySix Four]

Look at how the two shafts connect to the gear in the middle. If the gas motor produces more torque than the electric motor, the electric motor will simply be forced to spin backwards. They are connected to each other.

Or so it seems, it's tough based on a video.

 

[ShawnD1]

power != torque

If you only need to match the torque but not the power, then no problem. Electric motors are excellent for high torque, lower power operation.
torque = use electricity (this is why trains are series hybrid)
power = use gasoline

 

[Throckmorton]

This is just a planetary differential. Total BS

 

[Tristicus]

This is just a planetary differential. Total BS

Prove it.

 

[Meghan54]

It's almost a replica of a Prius transmission with its planetary gear system.

http://www.wind.sannet.ne.jp/m_matsu/prius/ThsSimu/index_i18n.html

Play around with D then R....you can watch the differential change the sun gears direction of travel....almost the same exact thing this "inventor" is demonstrating.



And Tristicus, when the "inventor" talks about sun gears, he's talking about a planetary differential, since sun gears are part of a planetary system......

 

[Zenmervolt]

What stands out is his claim that it will prove to be, "an order of magnitude more efficient" than current CVTs. Considering that a solid engagement isn't even an order of magnitude more efficient than a torque converter I am highly skeptical of this claim.

I'm also a little worried about the size; the prototype is already about the size of a small car's transmission and it seems to look as though it would need to be scaled up to be able to handle the loads that are carried by most automotive transmissions. This makes me wonder how large it would have to be in actual practice.

I'm also skeptical about the efficiency gains being sufficient to offset the additional energy required by the secondary motor necessary to control the ratios. Even if we assume a low-power motor like a starter motor, we're still talking about something that can draw 100+ amps and that's a lot of power that has to come from somewhere.

Finally, the lack of a proper fail-safe mode worries me. If the secondary motor fails, there is no actual neutral; you cannot disengage the engine from the transmission which strikes me as a situation that might become problematic.

ZV

 

[JulesMaximus]

I love rowing through the gears and no slushbox will ever take the place of a proper manual transmission!!!

NOW GET OFF MY LAWN!!!12

 

[ShawnD1]

I'm also skeptical about the efficiency gains being sufficient to offset the additional energy required by the secondary motor necessary to control the ratios. Even if we assume a low-power motor like a starter motor, we're still talking about something that can draw 100+ amps and that's a lot of power that has to come from somewhere.

12V battery * 100 amps = 1200 watts
1200 watts / 746 = 1.6HP motor

Not sure what the actual motor designation would be though. Motors are rated based on output power under the assumption that the thing is rotating, P = torque * rotation speed. Here you might be using the motor to simply the hold the shaft in place without rotating, so it's consuming 1.6HP of electrical engergy while outputing 0 mechanical energy; it's a 0% efficient system because it simply generates heat.


Meghan54, is your demonstration link how the actual transmission works or is that a differential completely separate from the transmission? Repeating what the inventor said about gears instead of chains, it should be possible to put quite a bit of torque through that kind of CVT without it breaking. That would certainly explain how something like a Nissan Murano can use a V6 engine with a CVT and it doesn't break. video of a guy trying to break his murano's transmission

 

[Greenman]

If you only need to match the torque but not the power, then no problem. Electric motors are excellent for high torque, lower power operation.
torque = use electricity (this is why trains are series hybrid)
power = use gasoline

You either don't understand the relationship between horsepower and torque, or I'm misunderstanding what your saying. In the world of car motors, horsepower is torque times rpm's divided by 5252.

A high torque low power engine is like a very bright dark, there ain't no such thing.

 

[futuristicmonkey]

You either don't understand the relationship between horsepower and torque, or I'm misunderstanding what your saying. In the world of car motors, horsepower is torque times rpm's divided by 5252.

A high torque low power engine is like a very bright dark, there ain't no such thing.

What you gain in torque, for a certain power level, you give up in speed. A high-torque, low power motor would have a (very) low rpm.

 

[EightySix Four]

You either don't understand the relationship between horsepower and torque, or I'm misunderstanding what your saying. In the world of car motors, horsepower is torque times rpm's divided by 5252.

A high torque low power engine is like a very bright dark, there ain't no such thing.

Yes there is. Let's say an electric motor was designed to operate at 1500 rpm and make 400 lb.ft of torque, at 5250rpm it would be way out of it's efficient area and would probably only make 50 lb.ft, and accordingly, 50hp.

This is why diesels are 750 lb.ft and 325hp.

 

[wirednuts]

you dont need an electric motor at all. like he says in the video, you could add a flywheel that could do the same thing... its just the fact that an electric motor would actually be simpler and more reliable is why he leans towards that.

i really like the idea. the ONLY problem i see is the orbital gear might produce wobbling or vibration at high speeds, but i imagine you could counterbalance that easily.

i think this transmission would also be good for wind towers- either to drive water pumps or run alternators at a constant speed no matter how fast or slow the wind is going.

 

[futuristicmonkey]

Yes there is. Let's say an electric motor was designed to operate at 1500 rpm and make 400 lb.ft of torque, at 5250rpm it would be way out of it's efficient area and would probably only make 50 lb.ft, and accordingly, 50hp.

This is why diesels are 750 lb.ft and 325hp.

Regarding your electric motor example, it is possible to get the full 400 ft-lbs of torque out of it at 5250 rpm. With the rated current flowing through the motor's armature, the rated torque will be developed. But in order to get that rated current to flow at the increased speed, you would need to increase the voltage applied at the terminals. The reason for this is the torque is determined by the current. The internal voltage (back-emf) of the machine would increase due to the increased speed. Remember faraday's law, Vemf = -d(lambda)/dt. d(lambda)/dt will increase as either the field flux, speed or both increase.

Due to the increased back-emf, the supply voltage would need to be increased, with the increase required depending on the excitation topology of the motor.

Of course, you'd burn the son of a bitch out in short order if operated this way for any amount of time.

 

[EightySix Four]

Regarding your electric motor example, it is possible to get the full 400 ft-lbs of torque out of it at 5250 rpm. With the rated current flowing through the motor's armature, the rated torque will be developed. But in order to get that rated current to flow at the increased speed, you would need to increase the voltage applied at the terminals. The reason for this is the torque is determined by the current. The internal voltage (back-emf) of the machine would increase due to the increased speed. Remember faraday's law, Vemf = -d(lambda)/dt. d(lambda)/dt will increase as either the field flux, speed or both increase.

Due to the increased back-emf, the supply voltage would need to be increased, with the increase required depending on the excitation topology of the motor.

Of course, you'd burn the son of a bitch out in short order if operated this way for any amount of time.

This has nothing to do with what we were talking about other than the fact that with my example you can make it happen... if you're willing to burn up the motor. I can make 1000whp out of my turbo I4 too if I'm willing to run it for only a few seconds.

 

[Zenmervolt]

you dont need an electric motor at all. like he says in the video, you could add a flywheel that could do the same thing... its just the fact that an electric motor would actually be simpler and more reliable is why he leans towards that.

A flywheel still needs to get its energy from somewhere; no energy is free. Either the energy in the flywheel has to come from siphoning energy that would otherwise go to the wheels or it would have to come from an auxiliary motor powering the flywheel. Also, since any reasonable flywheel would spin down well before the average stoplight has turned from red to green, there would still need to be an additional energy input to maintain "neutral" when the car was stopped at a light.

No matter what is used to power that secondary shaft, it's still going to take a couple horsepower to run and that energy has to come from the engine.

i really like the idea. the ONLY problem i see is the orbital gear might produce wobbling or vibration at high speeds, but i imagine you could counterbalance that easily.

If that's the only potential issue that you see, then it's obvious why you're not an engineer.

i think this transmission would also be good for wind towers- either to drive water pumps or run alternators at a constant speed no matter how fast or slow the wind is going.

We already have constant-speed drives for propellers; a system of purely mechanical weights and gearing alter the pitch of the blades to maintain a constant propeller RPM. The advantage of the current system is that it doesn't require an extra parasitic draw (the electric motor in the demo) to operate.

ZV

 

[herm0016]

We already have constant-speed drives for propellers; a system of purely mechanical weights and gearing alter the pitch of the blades to maintain a constant propeller RPM. The advantage of the current system is that it doesn't require an extra parasitic draw (the electric motor in the demo) to operate.

ZV

i think this could be a great transmission, but it has some obstacles to overcome.

wind turbines use nothing of the sort to control pitch and in turn speed. both models i have worked on use large electric motors and a computer to change the pitch for optimum efficiency in the current wind conditions. this requires that there be a large electrical connection between the spinning rotor and the generator section, using very large slip rings, and the motor controller was even mounted in the nose cone on one.
current model turbines do not have different gear ratios and will only generate electricity between about 25 and 40mph wind speeds. i am not sure but i believe that the speed is regulated with load on the generators, along with the huge 4 caliper disk breaks. emergency braking is very crude with a 6in dia pin on the end of a ram that rams it into the path of part of the connection between the nose cone and the gear train. also, they use hydraulic and/or electric systems to turn the nacelle into the wind or out of it depending on wind direction/speed.

 

[Throckmorton]

Prove it.

Look at the way it works. That's what it is.

 

[Throckmorton]

Guys, this is like taking your car's differential, putting an electric motor on one side, and then saying the variation in speed you an get on the other end is CVT action. Nope, you're just adding or subtracting speed through the differential. You aren't changing torque at all, AND the torque from the electric motor is the torque you get out the other end. You can't just use some little electric motor or flywheel, it has to balance.

Basically this guy is saying 2+1=9