Introduction & Cross wind solutions to motorcycle Streamliners?

[Cycle]

Originally Posted by sendler

I think you are making way too much of the bulging shapes of the under belly to try to project that up into the entire streamline of a motorcycle fairing. The top of the airplane fuselage where the majority of the area is located doesn't look anything like that.

Of course it doesn't look anything like that, because it's just a tube. There's not much more aerodynamically speaking that can be done to lower drag on a tube.

But for a bike, with wheels sticking out, we have to take into account rerouting the air around the wheels. Taking a cue from the airline industry as to how they route air around the base of the wings isn't "making too much" of anything... go with what the experts know.

[EDIT]
Ooh, just had a thought... the wheels are the wings, for a bike. The 'belly fairing' shape should be around the wheels to smooth airflow there.

[freebeard]

I was pretty sure there was some interaction with the wing root. But it widens the track; the Anatov AN-124 is similar, but a high-wing monoplane.

[Cycle]

Originally Posted by Teri_TX

Hi P-Hack,

Are you suggesting active counter measures like "fly by wire". I had thought of this in a moment of madness. If we had military or NASA budgets, that might be a possible solution. Think of the F-117. Besides, do we really want a bunch of code monkeys designing active control systems for our streamliners? Fighter jocks volunteer and get paid to risk their lives on monkey code. Unfortunately, if you fly on a modern airliner, you're a potential victim of bad code. I haven't flown since before 11 Sept 2001 and don't plan to. Apologies in advance to the real code monkeys among the readers.

Once, when I was looking at Vetter's long tail, a trim tab came to mind but he routinely rides through areas of rapidly shifting side wind directions, a worst case situation. A trim tab may be an option for some conditions but be aware of situation changes!

I have tried to think of how an active spoiler system could be implemented but nothing remotely simple comes to mind. Stall strips are the simplest solution I presently know of. Remember, K.I.S.S. (Keep It Simple, Stupid)

Passive automatic means are best for reliability in the real world.

-- Teri

K.I.S.S., definitely.

I'm exploring wing stalling for my design, somewhat akin to what F1 does for their rear spoiler by injecting air across the underside of the "wing". It's reversed in their case, since they're trying to create downforce, but the same principle applies... stall the wing. In our case, we'd inject air on the upper side of the "wing" to stall it, since it's reversed from the F1 downforce-producing wing.

I plan on doing it by having two scoops at the front of the bike, their openings angled backward at about a 15 degree angle. They'll scoop the air into ducts that cross over to the other side of the bike and exhaust further rearward and higher. Two small radiators will sit in those ducts, heating the air and thus lowering the density, which will help to "fill the void" and stall the "wing".

Going straight, both scoops provide relatively equal amounts of air to both sides of the bike, so the forces balance out. If you're getting hit with wind from the left, the right-hand scoop would be shielded by the bodywork, and thus the left-hand scoop would be forcing more air to the right-hand side of the bike, stalling the "wing". Vice versa for wind from the right.

Because the air exhausts a bit more rearward and further up than where it's scooped in, it moves the CoP rearward and lower because that exhausted air acts as a "longer lever" to counteract the side-wind loading.

Tony Foale Designs, article on motorcycle aerodynamics.
"To reduce the degree of lean necessary, we need to generate a small side force combined with a low C of P., to give the minimum disturbing effect..."

Further, the scooped air acts to "rob" the upwind side of the "wing" of some airflow, lessening the force on the upwind side of the bike.

A side benefit is that the air being injected back into the airstream during straight-line riding should help to keep the air attached to the body, thus giving better aerodynamics.

I plan on exhausting the hot engine exhaust (and the air that's pushed through the engine compartment to cool components, which will be scooped at the front of the bike via a small venturi intake to remove the "stalled" air directly in front of the bike) at the rear center of the bike to "fill the wake" and further reduce rearward drag.

[jkv357]

Interesting concept.

What speed will be necessary to get a noticeable effect?

[Cycle]

Originally Posted by jkv357

Interesting concept.

What speed will be necessary to get a noticeable effect?

Unsure. There will be an effect at pretty much any speed that overcomes duct friction (which would be pretty low), but a noticeable effect, unknown.

The good thing is, the faster you go, the more sidewinds affect you (mainly because due to speed, you have less time to react before you're blown into another lane)... and the faster you go, the more the cross-ducting counteracts the effect of the sidewind.

[sendler]

I think you will find that the required size of the duct entrance area is much larger than you might think. Circa 2 square feet minimum. Which we already have in the current Vetter streamliners. It's called the area where you get on and off the bike.

[PeterS]

Gentlemen, while you're there could you comment on the idea of a flat sided fairing ? It seems to me that avoiding the foil side to the fairing completely is the best way of avoiding "side lift".

My idea is a gently rounded forward section moving to flat sides tapering in a straight line to the rear.The profile from the side to be very much like a Vetter fairing.

http://ecomodder.com/forum/showthrea...ing-32339.html

[freebeard]

Originally Posted by Cycle

Unsure. There will be an effect at pretty much any speed that overcomes duct friction (which would be pretty low), but a noticeable effect, unknown.

You could start by calculating the number of cubic feet per minute of airflow. Then given the heat rejected you can get the increase in volume. Without an air pump (inline fan) I don't see that adding much flow.

As for the inlets and outlets of the duct[s], I would think the outlet would want to be a narrow gill slit to maximize the body height that is affected.

PeterS -- I looked at the other thread. Keep in mind that a flat plate can generate lift through 'angle of attack'. For a tapering body in a crosswind, when the crosswind angle exceeds the taper of the sides, lift will occur. Vortexes shedding off the sharp edges will increase drag. Sharp edges only work with a large fineness ratio like big-rig trucks and trains.

[PeterS]

Originally Posted by freebeard

PeterS -- I looked at the other thread. Keep in mind that a flat plate can generate lift through 'angle of attack'. For a tapering body in a crosswind, when the crosswind angle exceeds the taper of the sides, lift will occur. Vortexes shedding off the sharp edges will increase drag. Sharp edges only work with a large fineness ratio like big-rig trucks and trains.

Thanks , a good point but am I safe to assume that that lift would be LESS than with a "teardrop" shape .... the one we all automatically think in terms of.

Here are few photos of a rough model I made today. The sides are flat and the maximum cross section is around mid way but there is no foil. The rear could be narrowed more or even tapered a little without generating lift.

It is quite similar to the Vetter fairing and would have the same frontal area . Could i have some comments on this idea ?

[sendler]

Originally Posted by PeterS

It is quite similar to the Vetter fairing and would have the same frontal area . Could i have some comments on this idea ?

The wake drag would be many times higher than an airfoil but you would have some nice storage and probably still make a slight improvement in fuel consumption.