D-drive

It's one better than the F-drive!

Brent McKelvieJohn KrikorianRich Brown

What is it?

•  It is an infinitely variable transmission designed by Steve Durnin.

• There are no clutch plates or friction devices, therefore torque is only limited by gear teeth, not clutch slippage.

• Uses variable speed planetary gears to achieve this.

How does it work?

The D-drive works in a nutshell by comparing the speeds of two spinning (But not always) shafts. Before we get into the technicalities, let's sum it up by saying that when both shafts are spinning at identical (but opposite) speeds, the output is in a neutral state.  When the bottom shaft is slowed or stopped, the top shaft speeds up (hitting max speed when the lower shaft comes to a stop).  As the bottom shaft is sped up, the top shaft slows, and when it (the top shaft) is stationary, we have reached maximum reverse speed at the output.

 

To make this work, there is another input that is used to control the speed of the bottom shaft.  In fact, to envision this better, you can try to picture it like an automotive differential, but turned sideways. You would have your main input where one of the wheels are. The other wheel would be the output, and the driveline input would be where this second power application goes. In this scenario, while your input spun one tire, the other tire would spin in the opposite direction. The speed would then be controlled by turning the driveline input.

Why not just use the variable velocity motor?

 

Applications

As the D-Drive is cutting edge, brand new technology there are no physical applications yet  but there are many applications that could benefit from it...

Applications

Many Cnc machines require variable speed spindles.  The D drive could be used to control the output speed

Applications Infinitely variable transmissions in vehicles.   The benefit here is always having the best gear ratio for the speed, and removing the need for a clutch.  

Interesting facts about the D-Drive

With a variable speed electric motor input there is no need for the friction components (clutch) of a drive system. (normally considered to be the weak point.)

It was invented over the course of the last 10 years by Steve Durnin, a plumber in Queensland, Australia. The Toyota Prius apparently uses a very similar system to combine its ICE to its electric motor

Limitations and Disadvantages

• The D-drive needs a second motor to control the speed of the control shaft.

• This second motor needs to be able to be driven at variable speeds.

• If one motor fails the D-drive would be stuck in a ratio.

• Controlling the second motor with a clutch and CVT, which of course adds a friction component.

• Running the D-drive with load• The control motor needs to be just as powerful as

the input motor  

Controversy

• This CVT is being compared to an overengineered, overcomplicated open rear differential, in that you could accomplish the same feats without having all the extra gearing.