Streamlining. More important, the front or the back?

[NeilBlanchard]

A bicycle is mostly open, so it will benefit a lot from the front fairing, but I think a typical motorcycle will be more similar to a car i.e. a tail piece will be important. But the front wheel and forks are open, so you should look at Vetter and Allert Jacobs: http://ecomodder.com/forum/showthrea...diy-11970.html

[Grant-53]

My tests with tail sections on bicycles have not shown any improvement so far. I believe this is due to the fact the waste baskets are not as wide as the rider. A full fairing based on a vintage sailplane design is the next step. I posted the drawing URL in the #28 post of the Motorcycle Aerobody Research thread. It is similar to the Vetter nose with a rising tail. The nice part is that it is drawn with simple curves as in ellipses. If the tail is truncated at the sixth bulkhead the overall length is under 10 feet.

[freebeard]

My question stems from discussions of whether streamlining the front or the back of a motorcycle will make the most improvement if you were only to do one or the other.

There, see? Instead of a nebulous target we have a clear one—maybe the worst possible case. Length challenged, with the biggest problems in the middle, not the front or rear. Fully enclosed, semi-enclosed, sit-on or sit-in? Whoa. Beware weather-vane effects from the enclosed front wheel.

And the question is a set-up. What you do at the front influences the rear more than vice versa, but why would you do only one or the other?

Still, thanks for asking. Do you know what college Emil Faber was past President of?

[ChazInMT]

Ya see, motor sikles and bikes have this decidedly un-aerodynamic meat sack inevitably positioned between the front & back of them. I once read somewhere that a fairing that started the taper yielded good results.

Like dis.

[freebeard]

Your labeling reminds me of my Faber College days.

Can't remember if 'badder' was better or worse than 'gooder'.

[sendler]

Originally Posted by freebeard

but why would you do only one or the other?

Adding bodywork to the rear is a necessity in order to create luggage volume. Truncating the tail creates a flat panel to mount the license plate on and saves 3-4 feet of length in the garage. How much drag is increased by the Kamm?
.
I'm acually surprised that I can't find an online simulator that would let you play with different airfoils widths and lengths and allow you to add truncation to the tail.

[Sven7]

Originally Posted by ChazInMT

Ya see, motor sikles and bikes have this decidedly un-aerodynamic meat sack inevitably positioned between the front & back of them. I once read somewhere that a fairing that started the taper yielded good results.

Like dis.

[IMG]GOOD GOODER GOODEST

There was a thread about this on side mirrors, although I suspect you're talking about something else. I remember they had also discussed a stepped partial boat tail looking like conical window louvers.

Interesting thread, and it's good to hear the reasoning behind it now. I would imagine a motorcycle is so complex a shape that it would be more effective to simply carve some rough bodywork out of foam and test it yourself than to play with primitive CFD forms.

[ChazInMT]

Originally Posted by Sven7

There was a thread about this on side mirrors, although I suspect you're talking about something else.

Yes, someone designed a full fairing on the front of a motorcycle that had the shape returning in before it ended, this showed a fairly (?) dramatic drag reduction to the motorcycle....I just keep waiting to see it utilized by someone, but have yet to find where someone has made use of the idea.

It was a full sized motorcycle, with a Goodest fairing design, I do recall the rearview mirror.

[ChazInMT]

Originally Posted by sendler

I'm acually surprised that I can't find an online simulator that would let you play with different airfoils widths and lengths and allow you to add truncation to the tail.

I know, Right...2 things I've picked up over the last couple of years here:

1st, Flow simulation is about 50 times more complex than what you think it is, the math & such required to predict what a bunch of air molecules are going to do, and what effect this will have as an object moves through them, is astounding. The computing power required to run a proper test is enormous, see this video for what it takes to image swirls. They had 4,096 CPUs working together to make this.

The Secret Life of Vortices: Evolution and Destruction of Vortical Flows

What's this mean to you? Finding someone online willing to let you play with their 4,096 CPU's to simulate your various designs is not likely. Not even mentioning inputting the data to the simulation, in order to properly test what you are wanting to do, would require knowledge of the system way beyond what the layperson could understand without years of education on it.

2nd, Because it is so complicated, the slightest error in math will yield results that are not accurate in the real world. This is why any major automaker spends many 10's of millions of dollars on wind tunnels to test models for aerodynamic properties.

While flow simulation may get you close, there is no substitute for real air moving over a real object and measuring the forces to see how changes in design affect the overall drag, lift, downforce etc. on a vehicle.

[Frank Lee]

Originally Posted by ChazInMT

Yes, someone designed a full fairing on the front of a motorcycle that had the shape returning in before it ended, this showed a fairly (?) dramatic drag reduction to the motorcycle....I just keep waiting to see it utilized by someone, but have yet to find where someone has made use of the idea.

I used it on snowmobile hoods and pans starting in '93.