MCADXmag

The Durrani wheels, as originally conceived, never shipped. They were, however, a fascinating showcase of ideas which spawned “airtight patent applications with over seventeen claims” of original engineering. Durrani’s intent was to utilize the highest principles of modern manufacturing, as he explained: “It’s called designing ‘custom tailored blanks’ in the auto industry, where you have the ductility where you need it, the strength where you need it, with no more cost than you need. That’s the Holy Grail of manufacturing design.”

His original idea was to create a very lightweight wheel core out of a relatively inexpensive alloy of magnesium. This core would be comprised of the hub housing, spokes, and a thin connecting rim. The actual wheel rim, hubs and cush drive would all be attached to this. The alloy selected for the core was chosen for its shock absorbency, ductility, and suitability for use in a manufacturing process resembling plastic injection molding called Thixomolding.

Raw Thixomolded Wheel Core

Thixomolding is a relatively recently developed method of injecting semisolid slurries of certain metals at very high speeds through an enclosed auger, resembling a cannon. The temperature of the metal is hundreds of degrees cooler than the molten magnesium used in sand or pressure casting. The cannon and the mold, requiring up to 1000 tons of clamping force, are temperature-controlled to very close tolerances. Argon is used as a shielding gas for the metal, allowing it to flow without skinning for the 1/20th of a second it takes to fill the mold.

This process has been used during the last decade to manufacture relatively small parts like electronic casings, cell phone shells, and laptop frames. There is even a thixomolded magnesium fairing stay on the current Buell Lightning motorcycle. The ability of thixomolding to produce a piece with a very complex shape allowed Buell to eliminate several pieces that were attached to the previous stay, reducing cost, weight, and assembly time. But until the Durrani wheelcore, no one had successfully made a thixomolded part as large or as structurally demanding.

Surface Detail, Raw Core

The “thixotropic”property that makes magnesium so appropriate for this process is the way it forms spherical semisolids in the slurried state. This is important to accommodate the speed at which the auger shoots the metal into the mold, as the grains align well and the metal flows quickly. This process produces a very dense piece with little of the porosity of casting. Thixomolded parts have smooth and detailed surface qualities. There is very little waste material other than flashing, and the resulting cooled piece, if engineered correctly, can be within just a few thousandths of an inch from the intended ‘net shape’, requiring a minimum of extra 'machine stock' for post-secondary machining.

Unlike casting, which can tie up a mold for hours while a piece cools, the thixomolding machine can turn out many pieces per hour. Even large parts will run with cycle times of two minutes, or thirty pieces per hour, including the time necessary for the temperature of the mold to stabilize prior to injection and for the finished part to solidify before release.
[BREAK=Other features of the design]

The patented, model-specific Durrani hubs were threaded like “The mother of all huge bolts”, in order to screw into the matching center housing of the Thixocore. Utilizing chemical thread lock and reverse threading on one side, they would effectively tighten every time the front brakes were applied. Durrani pointed out: “In twenty-five years of making aftermarket cast wheels for motorcycling, nobody thought to bolt up a hub where the hub is the bolt. They all use five or six steel bolts, because each hub has to be different to fit a Triumph, GSXR, R1, or whatever. Each bike has a different placement of brake carrier bolts and rotor position. You’ve got a half pound of steel bolts in the typical wheel – in this design, they’re gone.“

Another elegant aspect of the design was the lightweight cush drive, which saved weight and complexity compared with the alternative of designing wheels to accept the original factory ones.

Hub DesignMag Cush Drive

The outer rims, onto which the tires would be mounted, were to be rolled rings of very strong extruded magnesium, in the shape of a standard rim in 3 1/2”, 5 1/2” and 6” widths. These rings were designed to be laser welded across the seam where they joined together, and that weld would be carefully buffed out. Finally, the rims would be chemically bonded to the thixocore, which would form the structural basis for both front and rear wheels, regardless of rim size. This feature was to have saved tooling, complexity, inventory, and money.

Partially Rolled RingMag vs Aluminum

The entire assembly would be treated with a conversion coating of magnesium ceramic oxide, electrochemically etched onto the surface to form a corrosion-resistant base for the final paint or powder coating.

Coated core

[BREAK=The Inventor]

• Proudly unconventional in their thinking, reluctant to do things in a particular manner just because that's the way they have been done.
• Resistant to criticism not supported by data and logic.
• Inordinately confident of their ability to solve problems as they present themselves.
• Averse to spending too much time making a detailed plan in advance.
• Non-conformists in the workplace, often challenging supervisors who are invested only in protecting the status quo.
• Irresistibly challenged by the phrase “it can’t be done.”

This description seems to fit Durrani very well, according to some of his statements and the impressions of people who know him. While it took a person who had this sort of personality to risk everything on such an unconventional approach to wheel building, there also had to be a wellspring of expertise, passion, vision, and motivation to trigger the effort.

Durrani’s obsession for magnesium is evident to anyone who talks with him. In our first conversation, he was quick to point out that “In one cubic mile of seawater, there is 70,000 tons of pure magnesium. The guy who discovers how to extract that metal cost-effectively could change the world, but the guy who uses it to make parts that are needed for society in a number of ways, that’s the guy who is really going to make a contribution.”

As a young engineer in the automotive industry, Durrani viewed the mainstream use of magnesium as an important means to satisfy the future demands of the transportation industry. Strong, light, inexpensive, moldable, easily machined, fuel-saving, and ubiquitous; it was the obvious answer to questions the moribund, tradition-bound auto industry wasn’t asking.

As he sought to develop new applications for his beloved metal, he met with a stone wall of institutionalized resistance to innovation. Durrani persisted, authoring patents and enjoying successes such as an engine cradle assembly for the Corvette and a prototype magnesium convertible top for Infinity.

That project resulted in his publication of a Society of Automotive Engineers paper which drew the attention of a group of German manufacturers. They came to the company that Durrani worked for, seeking help in developing a lightweight convertible mechanism for the Porsche Boxster and other Teutonic rag-tops requiring mag-tops. Unfortunately, Durrani's employers insisted on an aluminum solution. The Germans then started their own company, which later became a troublesome competitor.

On another occasion, his team made a proposal for a popular American SUV. Using magnesium to replace certain steel body components, they calculated the behemoth would lose 1400 pounds, increase gas mileage by 3.2 MPG, and save over a thousand dollars per car in production costs. The proposal was met with derisive and dismissive laughter.

Those rejections had a part in setting Durrani in motion. In his words, “The last thing any executive in Detroit is concerned with is innovation. They’re just worried about turning the lights off on the way out without getting run over in the process. That is the fate they have brought upon themselves in this town, and too many of my friends and neighbors have lost their jobs because of it. I’m one pissed-off engineer - I care, and I’m not going to take it anymore!”

Photos: D. Solo and Durrani Racing Components

Attached Thumbnails

     

CBRVFR

Part 3, in which the magnesium hits the fan, to be published 3-23.

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