D-Drive Infinitley Variable Transmission

[Rockbrick]

as always with these things I always wonder how to do this with lego....

[Cumulonimbus]

Looks like an interesting idea, although I don't completely understand how it works yet (sound is not available to me at the moment).

Is it correct that the vertical shafts are the output (but why two?) and which side is the input then?

I also wonder about the efficiency and lifespan of this setup.

[DrJB]

I too am not clear about how it works... There seems to be four shafts, input, output, one to vary the ratio ... besides the input, what are the other three for? Could be that one is to vary the ratio, and the other is output ... but then what is the 4th shaft for? Also, if proven to work, this would need another level mechanics to optimize the speed based on the load (as in common car transmissions). Some sort of 'load-sense' mechanism would be needed. Not to be a skeptic, but it's hard to to believe this is a 'revolutionary' device ...

[Rockbrick]

theres seems to be one input on the left and output on the right

the two inputs on the side are what make the system either a running neutral: both running the same speed, reverse: one full speed the other stopped, and then everything in between - infintiely variable ratios

I suppose that is kept a bit hidden due to patent pending - but some sort of electrically controlled automatic gearbox with 'virtual' ratios comes to mind for the side inputs

you could have two lego motors which you control the speed of the shafts controlled by the variable speed controller Remote

this will give you some virtual forward and reverse gearing based on the increments of the controller

then an XL motor as input and whatever as output as the input is on all the time - this is clutchless and lets you apply power to the output gradually by altering the ratio of the two side inputs

Edited October 13, 2014 by Rockbrick

[TheItalianBrick]

it's more an "open differential", But looks like there is a big problem there: the motor that controls the shafts must have the same power of the input!! Correct if I'm wrong...

[Rikus]

it's more an "open differential", But looks like there is a big problem there: the motor that controls the shafts must have the same power of the input!! Correct if I'm wrong...

You're right.

The system is quite pointless (at least in a Lego version), for many reasons...

1)

To change output speed you need to regulate "drive shaft" speed.

So, you'll need a variable speed motor to regulate output speed...!

2)

To have the system bear the neutral gear, both motors will have to run at same speed and supply same power.

3)

By using this, you'll end up draining batteries faster than light, since one motor will always run at max and second motor will have to run at variable speed to regulate output speed.

I'll try to make a scheme out of it:

Drive Motor-----\

I--------- Output

Power Motor ---------------------/

Output, in speed terms, is simply Power speed - (minus) Drive speed

The system is based on eccentric gearing, but is the same you can obtain using a standard differential!

Should you put on motor on one side and a sec on one (variable speed controlled) on the other side, you'll be able to regulate output speed by varying "drive motor" speed.

When Drive Speed is 0, Output speed is same on Power speed

When Drive Speed equals Power speed, Output speed is 0

When Drive speed exceed Power speed, Output speed is reversed (Drive-Power)

Edited October 13, 2014 by Rikus

[efferman]

looks like an adder subtractor with planetary gears

[TheItalianBrick]

try this simple test: connect 2 lego motors to the outputs of a bevel differential. one of the motor is wired via inverter switch..now turn them on and simply playing with the switch you will obtain a similar effect.....as in the video! basically you will slow down or accelerate (infinite variations) the differential inoput (that in this case is an output) simply buy turning off/on one of the motor!

this happens not cos of the speed of the motors, but cos of the ration between them! :)

[notareal]

it's more an "open differential", But looks like there is a big problem there: the motor that controls the shafts must have the same power of the input!! Correct if I'm wrong...

I think that's the case, so so basically to run this, one needs strong enough variable speed motors with those control shafts.

Edited October 13, 2014 by notareal

[Lipko]

Maybe I'm mistaking this with another "revolutionary" invention, but it seems like a concept that's been used since something like 70 years, and I remember learning about it from a 30 year old book. The continuously variability comes from the continuous variability of one of the inputs....

As far as I know, it is used in the industry for continuously variable drives in factories, and the variability is usually solved with a belt variator between the primary constant speed input and the other input.

Edited October 13, 2014 by Lipko

[Zerobricks]

Thats quite interesting! Maybe I will try make it in lego.

[TheItalianBrick]

Maybe I'm mistaking this with another "revolutionary" invention, but it seems like a concept that's been used since something like 70 years, and I remember learning about it from a 30 year old book. The continuously variability comes from the continuous variability of one of the inputs....

As far as I know, it is used in the industry for continuously variable drives in factories, and the variability is usually solved with a belt variator between the primary constant speed input and the other input.

the concept it's the same of course..but the difference it's in the "non use" of any belt, clutch, or engaging gears. Normal CVT transmissions use the "belt" concept but it generates frictions.

Anyway....this "invention" doesn't look that rivolutionary.....

Edited October 13, 2014 by TheItalianBrick

[hrontos]

I probably miss the point.

What is the difference between this and the adder/subtractor based on a standard differential?

Is it more effective?

Both of them need two equally powerful motors and on both of them at least one motor has to have a variable speed.

[Lipko]

the concept it's the same of course..but the difference it's in the "non use" of any belt, clutch, or engaging gears. Normal CVT transmissions use the "belt" concept but it generates frictions.

Anyway....this "invention" doesn't look that rivolutionary.....

But the whole problem with this invention is that you need to have at least variable speed input. It is (at least in most "old" factories) solved with a friction based variator of some sort. "More modern" modern factories probably use a variable wpeed motor. There is a perfectly reasonable goal of this device, but I can't remember what it was or how this thing is called so I can't google it. Maybe it is only used for increasing the speed range, which is pretty limited with friction variators.

Edited October 13, 2014 by Lipko

[aol000xw]

So if you already need a variable speed input... what does it achieve? I don't see it as a CVT if you already need some kind of speed control....

[zux]

looks like an adder subtractor with planetary gears

Sounds pretty much the same to me.

[Rockbrick]

The torque transfer is what's different about this, no belt or clutch, but I'd think it would be difficult to maintain two side speed inputs at the same speed in Lego to keep it in neutral....

Edited October 13, 2014 by Rockbrick

[Doc_Brown]

I thought this looked a little too good to be true, and just following the link shows the mistakes in the video!!!

It is clear that the input motors will be affected when under load so makes it kinda pointless lol.

On a side note, as this is an Australian invention and took 1000's of hours to create, its worth pointing out that that converts to approximately half a million beers.

http://www.gizmag.com/d-drive-redux/15120/

What we got wrong

Firstly, the D-Drive as pictured in our video is not a complete infinitely variable transmission system. At best, according to the engineering report, it is a cheap, innovative and potentially very useful primary component of an IVT.

The key problem here is that the D-Drive's control shaft needs to be driven at variable speeds in order to effect the final ratio - so effectively, you need a variable drive motor attached to the D-Drive before it actually works. e3k's engineering report goes so far as to say the control shaft could foreseeably be driven through an external CVT, using a clutch - which of course introduces not one, but two friction components to the system.

One of the main advantages we spoke of in our original article was that the D-Drive got around the need for friction components and transmitted all power through gear teeth. Effectively, if mated with a CVT, the D-Drive outsources the friction components to the transmission of its control engine.

The next thing we failed to pick up on, but that several commenters have pointed out, is what happens when you run the D-Drive under load. With the control motor running to decide on the final gear ratio, the input motor's power would be transmitted to the wheels, where it would meet resistance under load. That load would then be passed back through the gears to the weakest point - which would be the engine driving the control shaft, if it wasn't up to the job.

So it's not possible to run the control shafts using a small electric motor as we said in the video - in fact, the engineering report is quite clear on the fact that the 'control' motor needs to be just as powerful as the 'input' motor: "Our designation of 'Input' and 'Control' shafts in this report is arbitrary in that both would conventionally be used to provide power. There is no inherent character of the mechanism that requires the input to be the dominant power-providing element. The torque provided by the control shaft will typically be of the same magnitude as the torque provided by the Input shaft... the Input and Control should be considered as parallel power paths rather than as 'power ' and 'control' elements respectively."

What you got right

You can certainly rely on Gizmag readers to think through an issue like this one - some of the technical discussion in the comments section of the original article - as well as the discussion threads on Slashdot, Reddit and elsewhere - was fascinating.

The D-Drive does indeed operate as an epicyclic gearset. It does indeed operate in a similar way to the Hybrid Synergy drive on the Toyota Prius - and this is a matter of some pride to Steve Durnin, who designed it with none of Toyota's considerable resources behind him.

It does require an external CVT or some other powerful drive component for the control shaft that will not yield to the torque of the primary input motor.

So where does this leave the D-Drive?

More or less where the engineering report concludes. The D-Drive is an innovative component that could be used in the design and manufacture of a true IVT for use in vehicles or anywhere else a variable drive would be required.

It's not a 'holy grail' and there's no rabbits coming out of hats - and what's more, it can't forseeably operate with no friction components between engine(s) and wheels, or at least something like an electric motor that can be smoothly varied in speed.

The D-Drive should, and will, be evaluated on its abilities inside this scope - and as such it may well still become a very valuable piece of intellectual property for its designer.

[TheItalianBrick]

i really respect the "inventor", but honestly....he spent 20 years of is life around this "non exactly working neither innovating" thing.....

He could have travelled the world for 20 with half of the money probably

[Rockbrick]

I think in lego it would be easier to have the input and control motors of similar torque or just use the same motos and a variable resistor for the control ones ...

8<...He could have travelled the world for 20 with half of the money probably

...like a friend of mine who restored his car piece by piece with shiny new polished parts... the car was better than showroom - it took him 15 - years to do

he drove it a couple of times and then died in his sleep. He wasnt that old either.

Later I found out he was an alcoholic and that restoring the car kept him away from the bars and his wife happy...

Edited October 14, 2014 by Rockbrick

[TheItalianBrick]

Later I found out he was an alcoholic and that restoring the car kept him away from the bars and his wife happy...

true, but don't forget that he was an alcoholic at first place....

At least your friend has done lots of successfull thing as you said, this D-Drive invention hasn't.