Airflow - The Kamm effect

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Airflow - The Kamm effect

Post #1 by sunnbobb » Thu Oct 11, 2012 2:17 am

I thought I would share this interesting concept. Who knows? Perhaps it will make you bike faster at Bonneville.. lol

A Kammback is a car body style that derives from the research of the German aerodynamicist Wunibald Kamm in the 1930s. The design calls for a body with smooth contours that continues to a tail that is abruptly cut off. This shape reduces the drag of the vehicle.

"Kammback" is an American term. In Europe the design is generally known as a Kamm tail or K-tail.

airflow.jpg


While the realities of fluid dynamics dictate that a teardrop shape is the ideal aerodynamic form, Kamm found that by cutting off / flattening the streamlined end of the tear at an intermediate point, and bringing that edge down towards the ground, he could gain most of the benefit of the teardrop shape without incurring such a large material, structural, and size problem. The airflow, once given the suggestion of the beginning of a turbulence-eliminating streamlined teardrop tail, tended to flow in an approximation of that manner regardless of the fact that the entire tail wasn't there. This is called the Kamm effect.[9]

There is controversy about the proportions of a true Kamm tail. According to the classic definition the tail should be cut off where it has tapered to approximately 50% of the car's maximum cross section, which Kamm found represented a good compromise - by that point the turbulence typical of flat-back vehicles had been mostly eliminated at typical speeds. Thus a minivan is not a Kammback, and neither are numerous cars that have truncated tails.

This concept would apply fairly well to stream lined Bonneville Salt Flat bikes I would think.

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Re: Airflow - The Kamm effect

Post #2 by fish » Thu Oct 11, 2012 2:56 am

OK thanks Sbob.... now I undrestand better.
I allways thought the styling department ran out of funds with the daytona coupe.
th.jpg

I assume having a long tapering tail is a PITA in a crosswind as well.
so the Kamback solves a lot of problems anim-cheers1
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Re: Airflow - The Kamm effect

Post #3 by Hal » Thu Oct 11, 2012 4:47 am

Alfa Tubulare is another classic Kamm tail design.

Image

The 1965 Iso Rivolta "Breadvan" is another.....ish

Image

and Ferrari's take on the Kamm tail....The Ferrari 'Breadvan'

Image

Razzaire similar, don't you think? Doubtless penned by the same Carozzaria.

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Re: Airflow - The Kamm effect

Post #4 by AODRN » Thu Oct 11, 2012 6:18 am

Now I just need to hit each rear quarter panel on my truck with a hammer untill gas mileage improves.
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Re: Airflow - The Kamm effect

Post #5 by ericheath » Thu Oct 11, 2012 7:40 am

So how do we use this in our carbs and valves? That should give a performance boost. I know it's too expensive, but that's an inefficient area of air movement in our engines.
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Re: Airflow - The Kamm effect

Post #6 by Track T 2411 » Thu Oct 11, 2012 9:43 am

ericheath wrote:So how do we use this in our carbs and valves? That should give a performance boost. I know it's too expensive, but that's an inefficient area of air movement in our engines.

Actually, some turbulence or swirl is wanted on the intake side of the cylinder to improve/maintain the air/fuel mixture. The exhaust side (in general) benefits more from smoother flow. Looking at the exhaust valve, which often is the most restrictive area on that side of the cylinder, one can see that the possibility of a "cone" shape on the back side of the valve (moving up the stem) might reduce turbulence, yet in practical applications, there is too little space in the runner to make it viable. It simply takes up too much space.

One could think about ways to improve airflow into the carbs, however, which may be of benefit to performance, if one is able to accurately tune the carbs.

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