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Court rules SRAM patents not infringed by Princeton Carbon Works' aero wheels

The ruling brings the two-year dispute over the undulating rim design to an end

SRAM has lost its case against Princeton Carbon Works, with a jury in Florida ruling the performance wheel brand's aero design — namely the undulating rim shape that is said to reduce aerodynamic drag and side force — does not infringe patents.

The verdict came at the end of a two-week trial after SRAM had filed a complaint accusing some of Princeton's models of infringing on patents for the wavy rim shape that is used on SRAM's Zipp 454 Carbon NSW wheels.

SRAM patent drawing

Final arguments were heard on Thursday and just before 3pm on Friday the jury returned a verdict that Princeton had not infringed either of the two patents SRAM had accused the company established in 2018 by a group of engineering graduates from Princeton University of.

"We are pleased with the outcome and look forward to continuing offering exciting, high-performance wheels to discerning cyclists," Princeton CEO Harrison Macris told Bicycle Retailer and Industry News.

The wheels at the centre of the patent dispute – the Zipp 454 Carbon NSWs – rely on two patents from inventor Dimitris Katsanis, best known in the cycling world for designing track bikes used by Team GB.

SRAM's patented rim shape is partly inspired by a humpback whale, with the article 'Hydrodynamic Design of the Humpback Whale Flipper', published in the Journal of Morphology in 1995, cited in the patent. The sawtooth design came from the irregular shape of the leading edge of humpback whale pectoral fins.

On the other hand, Princeton argued the Wake 6560 design came as the result of four years of development by Princeton Carbon Works and contains 24 sinusoidal oscillations, giving a depth that varies from 60mm to 65mm.

As we noted in our original article on the patent dispute back in 2021, the depth of the Princeton rim and the Zipp rim each vary, but the Princeton undulations appear symmetrical while the shape of the Zipps is more like a sawtooth.

In its complaint from March 2021, SRAM alleged that Princeton was aware of the patent and continued to market its wheels. SRAM asked for tripled damages for wilful infringement and for Princeton to be ordered to deliver up for destruction of any remaining inventory, however, the jury ruled against the Chicago-based company.

At a pre-trial hearing last month, US District Judge Roy Altman granted a series of partial victories to the two companies, before ultimately deciding that the case should be settled by a jury.

"This case presents us with a proverbial battle of experts," Altman concluded. "As we've said in a slightly different context, 'we think it beyond cavil that the task of resolving [factual] disputes rests squarely with a jury of laymen, not a panel of unelected judges'."

Dan is the news editor and has spent the past four years writing stories and features, as well as (hopefully) keeping you entertained on the live blog. Having previously written about nearly every other sport under the sun for the Express, and the weird and wonderful world of non-league football for the Non-League Paper, Dan joined in 2020. Come the weekend you'll find him labouring up a hill, probably with a mouth full of jelly babies, or making a bonk-induced trip to a south of England petrol station... in search of more jelly babies.

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jaymack | 1 year ago

Meanwhile the lawyers on both sides will no doubt be delighted with the fees generated by litigating an issue of such great import.

Global Nomad | 1 year ago
1 like

grateful to learn a new word

The meaning of CAVIL is to raise trivial and frivolous objection.

Secret_squirrel | 1 year ago

I'm going to challenge them both on behalf of the whales.  They deserve royalties.

I for one actually think the Whale bit is a crock.  Hydrodynamics are not aerodynamics.  Otherwise the flying submarine would be a thing.

Global Nomad replied to Secret_squirrel | 1 year ago
1 like

its all fluid dynamics - both water and air do behave in much the same way...

TheFatAndTheFurious replied to Global Nomad | 1 year ago
1 like

Doesn't compressibility come into play though? High pressure in air results in a smaller volume. Not so in water.

Creakingcrank replied to TheFatAndTheFurious | 1 year ago

That's true, but fluid dynamics engineers tend to ignore the compressibility of air at speeds below about Mach 0.3, as the effect is small. That's 370kph according to Google. 

Here's a random link about it from the Internet:



ShutTheFrontDawes replied to Secret_squirrel | 1 year ago

I'm not so sure. The Reynolds's numbers might be in the same order of magnitude (for the whales, not the flying submarines).

Psi Squared replied to Secret_squirrel | 1 year ago

FYI, for some air projects with large Reynolds numbers (length Reynolds numbers) and low velocities, testing is done in water tunnels, not wind tunnels.  

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