- #1

- 3

- 0

Thank you

- Automotive
- Thread starter Rishabh Sharma
- Start date

- #1

- 3

- 0

Thank you

- #2

Bystander

Science Advisor

Homework Helper

Gold Member

- 5,203

- 1,225

- #3

rcgldr

Homework Helper

- 8,728

- 545

If you mean ram air intake as used on some sport bikes, it adds about 5% power at around 300 kph (186 mph).

Last edited:

- #4

- 3

- 0

- #5

- 2,053

- 2,720

I would personally guess a 0.8-1.0 hp/ft² at 60 mph. The lower value being representative of a full fairing bike with a driver lying low and the higher value being representative of a bike with no fairing and a driver sitting straight. Although, I wouldn't be surprise that 1.5 hp/ft² can be achieved in an extreme case.

But these values are proportional to the

Assuming similar, typical, frontal area (but the Harley would probably be larger), the aerodynamic impact would be:

[tex]

\begin{array}

\textbf{Speed (mph):} & 60 & 90 & 120 \\

\textbf{Harley drag (hp):} & 5 & 17 & 40 \\

\textbf{YZF drag (hp):} & 6.2 & 21 & 50 \\

\textbf{difference (hp):} & 1.2 & 3 & 10

\end{array}

[/tex]

\begin{array}

\textbf{Speed (mph):} & 60 & 90 & 120 \\

\textbf{Harley drag (hp):} & 5 & 17 & 40 \\

\textbf{YZF drag (hp):} & 6.2 & 21 & 50 \\

\textbf{difference (hp):} & 1.2 & 3 & 10

\end{array}

[/tex]

So, to refer to the OP's question, there is no particular speed at which the aerodynamic effects «begin»: The Harley requires about 25% more power at any speed than the YZF.

- #6

Bystander

Science Advisor

Homework Helper

Gold Member

- 5,203

- 1,225

If I didn't know better, it would be embarassing to have dragged that square all the way through --- knowing better and typing it --- too many bugs in my teeth.of the speed, not the square.cube

- #7

- 311

- 23

from experience, about 80 mph

- #8

Doug Huffman

Gold Member

- 804

- 111

- #9

- 366

- 16

http://news.motorbiker.org/Videos.nsf/Motorcycle-Superman.jpg [Broken]

Last edited by a moderator:

- #10

cjl

Science Advisor

- 1,864

- 439

Sure, drag force is proportional to speed squared, but drag power is proportional to speed cubed (since power is force times velocity).

- #11

rcgldr

Homework Helper

- 8,728

- 545

So the YZF with a fairing has more drag than the Harley? I was thinking that the rider leaned over on a YZF would end up a bit more streamlined than a vertically oriented rider on a Harley.[tex]

\begin{array}

\textbf{Speed (mph):} & 60 & 90 & 120 \\

\textbf{Harley drag (hp):} & 5 & 17 & 40 \\

\textbf{YZF drag (hp):} & 6.2 & 21 & 50 \\

\textbf{difference (hp):} & 1.2 & 3 & 10

\end{array}

[/tex]

- #12

- 2,053

- 2,720

Sorry, by reading the text, it is obviously a mistake on my part. It should of read as:So the YZF with a fairing has more drag than the Harley? I was thinking that the rider leaned over on a YZF would end up a bit more streamlined than a vertically oriented rider on a Harley.

\begin{array}

\textbf{Speed (mph):} & 60 & 90 & 120 \\

\textbf{YZF drag (hp):} & 5 & 17 & 40 \\

\textbf{Harley drag (hp):} & 6.2 & 21 & 50 \\

\textbf{difference (hp):} & 1.2 & 3 & 10

\end{array}

- #13

RaulTheUCSCSlug

Gold Member

- 179

- 25

- #14

- 18

- 8

I seriously beg to differ.. I've built every type of HD Sportster racer there is, from unfaired dragsters, to half faired Sporty road racers @ Daytona, to 883 series road racers w/ nothing but a flat # plate for aerodynamic's on the front, and the flat tracker's share the same flat # plate, in front. If you talking about the little semi "boat tail" on HD flat trackers (XR 750), that was designed more fore aesthetics, than drag reduction.Some Harley Sportser flat trackers are made to be pretty aerodynamic.

- #15

- 255

- 30

Aerodynamics play a role almost right away. Bicyclists will attest to this. There's a lot more drag at 15 MPH than at 10 MPH on a bicycle.

- Last Post

- Replies
- 2

- Views
- 851

- Last Post

- Replies
- 1

- Views
- 5K

- Last Post

- Replies
- 5

- Views
- 1K

- Last Post

- Replies
- 7

- Views
- 13K

- Last Post

- Replies
- 6

- Views
- 6K

- Last Post

- Replies
- 0

- Views
- 3K

- Last Post

- Replies
- 1

- Views
- 2K

- Last Post

- Replies
- 5

- Views
- 4K

- Last Post

- Replies
- 9

- Views
- 708

- Last Post

- Replies
- 1

- Views
- 3K