Frontal Area and I don't mean hers!!

[wolbrink471]

An easy and accurate way to determine the actual frontal area of a motorcycle ( and/or a car if that is your thing ) is to use a digital camera, the longest zoom lens you have available, and a yard stick.

Square the bike and yardstick up and take a photo from as far away as possible to reduce 'paralex'. Download the image and start reducing the DPI. The goal is to scale off the yardstick so that one square inch in the image is represented by a single pixel on the computer screen.

Print out a copy of the photo and start counting blocks.

I didn't think of this, but sure wish that I had! It works great. I really appreciate all the help I get on this forum, so I really hope this is something new and/or helpful to someone!

Mark

[Seldom Seen Slim]

Oh, my gosh, he's at it again.

Parallax, not paralex.

You're welcome.

[wolbrink471]

Oh, my gosh, he's at it again.

i think/hope you meant ' he's still at it'

[JackD]

It is known as a "Graphic Scale".
That is one of the reasons you see it on plan drawings.

[Dean Los Angeles]

Hey! You bike guys! Don't forget the other 40% of the frontal area! Make sure you have someone else take the picture with you on it. 

[Stainless1]

Did y'all miss the post about streamlining, frontal area doesn't matter, all the other stuff does. 

[bak189]

Frontal area is important........but would you believe air going out the back is even MORE important.....our tunnel tests have shown this!!!!!!!!!...........test and learn....it's a wonderfull thing!!!!!!!!

[Stainless1]

Frontal area is important........but would you believe air going out the back is even MORE important.....our tunnel tests have shown this!!!!!!!!!...........test and learn....it's a wonderfull thing!!!!!!!!

We've always operated on the idea that if you don't add it to frontal area, it won't require any streamlining.   

[Harold Bettes]

A very easy way to establish a fairly accurate cross sectional (frontal area) of any vehicle is to place the vehicle up very close to a wall that is covered with butcher paper or packing paper and affix some graph lines on the stuff at every inch both vertical and horizontal lines. Then use a few incandescent lights in front of the vehicle.....The shadow knows the true cross sectional "view" of the vehicle. Tracing the shadow allows one to measure the vehicle's real cross section by simply counting the squares within the tracing of the shadow.

The information does not give a Cd, but it gives a very good reference to the frontal area of the vehicle and bikes can place the rider on if you can keep him or her still for long enough to get a sketch of the shadow done.

The frontal area of the bike/rider is not as much of a problem as the exit loss(es), so skillful use of "wheelie bar" type apparatus might be worthy of a look. Unless you wanna lay down on the thing.

Regards to All,
HB2

[Dean Los Angeles]

Yup, yup, yup, I got me one na those 1000mm lens in ma back pocket.

[Reverend Hedgash]

Then use a few incandescent lights in front of the vehicle.....The shadow knows the true cross sectional "view" of the vehicle. Tracing the shadow allows one to measure the vehicle's real cross section by simply counting the squares within the tracing of the shadow.

Sorry but this is not a very accurate way at all unless you move the light a long way away from the bike and the bike is very close to the wall and even then I still don't like it as a method!
The light is still a point source with its rays expanding out at a rate proportional to the width of the bike and the distance the light is from it.

And why would you use more than one light? Two shadows better than one? I don't think so...

The shadow is not a scaled up version of the sectional area as to get the whole bike's shadow on the wall the light would have to be low thereby distorting (keystoning) the whole image...

I think the long lens camera, at a long distance appropriate. You don't need the yardstick or tiles as you can measure exactly how high the bike is in reality and scsale from there.

Reverend Pedanticgash

[Harold Bettes]

Well, actually one can get very accurate results using light. After all, the photo method is also using light and the method of color changing pixels is called shadow tracing. The portions of a shadow are varied and the object is to trace the umbra (the most sincere shadow). Of course you are correct in that the vehicle must be fairly close to the wall (even though one would expect that). Sorta like gravity. It seems to work everywhere in some fashion or another.

However what Scott has stated is the most critical. It is what you do with the data that is most important.

So, one could say that you should "always look under the street light for the answers" and "the best secrets are always those that are in plain sight". Oh gee, those sound like Jack D truisms!

Regards to All,
HB2

[wolbrink471]

you always learn alot when you look at yourself as others see you.............or something like that.

seriously, I just thought it was an easy way to see how the bike & I fit, or more importantly where we don't.

Mark

[desotoman]

Did y'all miss the post about streamlining, frontal area doesn't matter, all the other stuff does. 

I am a Roadster guy so I don't know anything about this subject. So are you saying that if you had two cars that both had the same CD, but one had 10 square feet of frontal area, and the other had 6 square feet of frontal area, powered by the same HP and TQ figures they would go the same speed?

Sorry I cannot believe that, common sense is telling me the smaller frontal area would go faster when all else is the same.

Tom G.

[tortoise]

What part of  don't you understand?