Superbike aerodynamic improvement

[agressor]

Dear Members,
this is my first post, glad to be part of this board. Know some of You have huge knowledge, this why I let myself to start topic in here. Been building my bike for almost 7 years, now its time to work on better aero, I was inspired by moto gp bikes.





I had to options do it just for look, are do all necessary calculations, I choose second way.
What I want to achive is better flow all over the bike, separat flow and reduce drag. I count also on better stability in to the corners (with "stock" look of the bike).

Waiting for feeback.

Lets start.

Im using aircraft science knowledge to make them work in my case, am I correct I don't know but if values will resonable I guess I will be. When we look at the bike from above it has approximately shape to tear drop, so I looks like wing in cross-section. So I think when we want to make vortex generators we can use same calculation as aviation.



air density - motorcycle (yes)
chord length - motorcycle length
dynamic Viscosity of air - set value

At the end we have stall speed, copy paste (Sumontro Sinha)
Stall speed is the speed where a wing loses lift and adds a lot of drag.
Should be lentgh from end of side fairing to the end of the bike.




I only think now about upper stream of air (fastest air) as its most important for us,
second side of bike is equal (I know exhaust).

The exact formula is
V = √( 2 W g / ρ S Clmax )

V = Stall Speed
W = Weight of the aircraft
g = 9.81 (Acc. Due to Gravity)
ρ = Density of Air
S = Wing Area
Clmax = Coefficient of Lift at Stall

Wing area is our whole bike (of course not in 100%) but I will count it as a length and from highest point to the ground.

Another value which I need to solve is Coefficient of Lift at Stall which is angle of attack,
I will take value from center line of the bike (from above) to maximum angle of bike turning point.

All these will let me to get Reynolds Number which I need to determine the height of my main wing and then.

Drawings and some pictures of my test.



Here is a test with strings, speed was about 70km/h.
What I think I see is no chaotic flow. No good result. Tail section is completely wasted.
Do not understand why flow is going down (this could increase wheele symptom).



What I want to achive.




During the weekend I did some calculations ang get some numbers. I cut cardboard form of main wing (to be honest there should be 3 of them across whole hight of the bike).
All numbers are for rectangular vortex generator beacuse I have good explenation how to do this. Anyhow rectangular profile is good as it self because of a big operating surface.
After I get size of the wing I calculate winglet for it basing on diameters of the wing.
Was thinking about profile, what I get its about 8mm maximum thickness, which should be 1/3 length from front of the wing. Need to read about it more. Shape should depand on Re number size.

After all I calculate best postions and hight for wing to be placed.

Back in a days I did also handle fairings, but know I think they should be a bit bigger (I change clip on's position to wider.

Pic. material:













What do You think about it?

[LVDH]

Just a few comments, as I do not know that much about motorcycle aerodynamics:

Your math does not apply to ground vehicles they way you think.

It seems like you are planning to reduce aerodynamic drag by looking at your bike from top and try to treat it as an air foil. You think by reducing the separation of the air flow you will reduce aerodynamic drag. The funny thing is you should not be so sure about that. Check out what some people call the Kamm-effect.

The thing you will mainly have to be very scared about are the side forces your bike will create if it was an air foil with attached air flow. They will be very big. As soon as you have some side wind you will have an angle of attack that will possibly turn you into an organ donor. In my opinion attached air flow will be the worst thing you can do your stability.

If you want to reduce drag you should add gurney flaps or just a kick-up the the trailing edges of the front fairing. A nice separation spoiler on your helmet will be very beneficial as well, probably also for driver comfort at higher speeds.

Don't get me wrong I love experimenting with aerodynamics and like the tests you are doing with the wool pieces, I just think that you should be very careful.

[agressor]

Thank You for comment LVDH, thats very interesting, will read about Kamm effect.

Of course I will be careful, survived 10 years in saddle, do not want to be killed.

Yes I've been looking at bike from a top, need some point of attachment with calculations.

[Jolle]

Fun project!

As far as I know there are/were three big developments on bike aero (apart from having a smooth fairing in the first place) with three different goals:
The BMW K1: reduce drag and turbulence, especially between layers, the front mud guard, flip up screen and small "cases" behind the legs
The Honda CBR900RR and the NSR's from that time: holes in the fairing to prevent the formation of a upward ground effect between bike and ground under extreme lean angles
The current MotoGP bikes: winglets to help to keep the front wheel on the ground during acceleration.

Are you racing the bike on track or more a case of having the slickest bike on the road?

[agressor]

Thanks Jolle, I do it for myself, I do not race it, too much cash involve, however one day it could be fun to test it on a track.
Guess my goal is slickest bike on the road.
My last quite big project, rear brake disc based on F16 carbon-carbon disc (titanium race pads).

[agressor]

Thanks Jolle, I do it for myself, never been on race track, however I think it could be fun to test it on RT.
So I guess my goal i slickest bike on the road

[agressor]

During the weekend I did cardboard VG and make a small test.
Thought result will be better or just more noticeable, however I think I should go fasters.
Very interesting thing is that VG fit perfect in diameters to original wing, space between all of them is 74mm.

In middle picture what I can see is that strings are not going down like before,
after hot air outlet we are loosing control so I guess ther should be something.
Main wing of side fairing wasn't installed.

[Gatecrasher]

For the ZX10 read up on Salt Flat bikes, a lot of good info on suspension and bodywork improvements out there. Also please ATGATT

[agressor]

Thank You Mate, yes I know about gear...

[agressor]

Been busy last weeks, but now Im getin back to business

Sorry for bad quality pics. I did first part of aero, small vgs to mount them on front of side fairings.

Its double 120g cf and polyester resin. Weight and stiffnes its pretty decent.

Now I will make bigger sheet for big wings.

[J.A.W.]

The OP might be interested to know that in a recent post championship test meeting,
the current Superbike champion was lapping as quickly as the 2nd string Moto G.P. machines.

I'd suggest that a close look at the last 250cc G.P. bikes may offer some aero clues, since these
bikes were recording race top-end speeds of close to the 300 Km/h mark, on not very much total hp...

[Tim.Wright]

One thing to keep an eye on is that vehicle design rules in most countries requires a minimum radius on all external surfaces - so the VGs will need to be blunted if you want to avoid the wrath of the local constabulary. At that point they probably won't work any more though.

[agressor]

Thanks Tim and Jaw, local police its not really my concern but thanks for a clue.
Jaw I guess 250cc are much more litgher than SBK bikes.
Best Regards
Tom

[turbof1]

Just bumped into this thread. I'll make a couple of remarks on the comments, regardless of the original posting date:

Do not understand why flow is going down (this could increase wheele symptom).

This is guessing, but I think it's because the underbody generates a zone of negative pressure, drawing in flow from atop (ground effect). This is not such a bad thing: flow coming out of the cooling openings gets drawn in by it and increases in velocity, increasing laminar flow and probably decreasing drag. Motogp bikes even encourage this by angling the openings:


It will increase wheelies, but you can fix that by fitting winglets - at the cost of additional drag- on the windshield area.

I am by no means an expert, but if you want to reduce drag through aerodynamics, the rotating wheels should be your primary target. These things create huge amounts of drag. Diverting flow away is not an option is that'll remove cooling for the radiators. So it might be better to clean up flow behind it . I think low VGs will be quite beneficial. This is also one of things you cannot solve by aevial aerodynamics as a plane has little moving parts exposed to outside flow.

I will comment on the rest later, but like LVDH, I do want to warn about cornering forces. Aerodynamic load dropping out while cornering will make the bike highly and unpredictably unstable. The increased forces can also wear you out.

Finally, evading separating flow is not necessarily beneficial towards drag and seperation might infact be beneficial on areas where the flow has to work really hard (creates lots of aerodynamic load), depending on the induced drag.

[agressor]

Thanks for input Turbo! I now that wheels are an issue,
was even thinking about rear disc...
During whole build want to change them, however huge cost of better and lighter rims makes them still not avaliable for me.


Cheers Tom