May 172010
Gears on a piece of farm equipment, gear ratio...

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Every now and again, astute Gizmag readers come to the fore to keep us on our toes – and never has this been better demonstrated than with last Friday’s D-Drive Infinitely Variable Transmission article. More than 40 comments and e-mails have flooded in over the weekend questioning the D-Drive’s capabilities as a true IVT, and its potential efficiencies.

Furthermore, an engineering report was made available on the D-Drive website that flat-out negates some of the key claims that were made in our interview video. So let’s take another look at this device in the harsh light of engineering scrutiny.

Steve Durnin’s D-Drive gearbox has spurred a lot of interest since it first came to public attention on the Australian ABC’s New Inventors show earlier this year. But despite its winning the weekly invention challenge, the device was explained in only the vaguest of terms, giving technically minded folk little from which to draw any proper conclusions.

I contacted Steve Durnin and arranged a meeting, during which we filmed the device from all angles and discussed its potential at length. I then put together a video story, touting the D-Drive’s potential as an Infinitely Variable Transmission, talking about its potential efficiency advantages, and explaining how it works from my own (non-engineer’s) point of view.

Steve, meanwhile, was working to put together a website for the device – which he made available to me just before the Gizmag article went live – and which contained a link to an engineering report that presented the D-Drive in much more sober terms.

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.

Read more . . .

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