MotoGP aerodynamics

In the last test IRTA in Sepang, Yamaha showed the next step in MotoGP aerodynamics.

Fairing with ducted vanes

Technical regulation is forbidden aerodynamic appendices, therefore if you want to work with aerodynamic, only you have shape and ducts in the fairings.

Fairings are reason for aerodynamic existence, and the first goal is to down Cx in the motorbike.

Low Cx is less aerodynamic drag, and more top speed with same power, but this is dead end way when the top speed is all.

We take Honda RC213V values,

• width = 0.645m
• height = 1.110m
• Area = 0.562 m2 (Elipse área wuth height and width)
• Cx = unknow

However we have hayabusa Cx = 0.561, and could be estimate that the MotoGP more and less 0.5 and 0.6

	Cx	200 km/h	300 km/h	355 km/h
Hayabusa	0,561	45 HP	152 HP	252 HP
MotoGP	0,5	40 HP	136 HP	225 HP
	0,6	48 HP	163 HP	270 HP

We could see that the top speed is reachable by motoGP is the same that, but big part of circuit the power is superior than you need, the famous wheelie is this fact, engine to provide more power that bike could take to increase the speed.

Conclusion, top speed is only one point in track and more than 90% in the track, engine provides more power than motorbike can manage it.

Therefore, 90% in the track, we can power waste.

How? One way is aerodynamics effects, in the 2016 season we saw wings in all motorbikes, but in 2017 is forbidden wings, but wings are not all aerodynamics. we could explore two ways,

1. Slots and coanda effects
2. Lifting body

Yamaha show the first field, with ducted vanes to provide Coanda effect. is for air viscosity create boundary layer and air follow this profile meanwhile dont broke it, (stall effect).

Coanda effect follow the profile

But the coanda effect has other behaviour, and this could see in the Hunting H126 and it jet flaps.

jet stream drag the surrounding air in the same direction

Jet stream, deflect the air ans create lift

You could work with this effect, and create air paths in the surface, like diverterless, this effect could see in the F35 Lightning II engine intake.

This is DSI shape and it has other advantages in supersonic speeds

Lifting body create lift forces without wings, due to the body is a wing

With this effect and "dowforce" body, and ducted jet stream we could create down force, like the old wings.

Drag creates for in air intake is converted in downforce. Purple lines is air flow.

One point where could be create this effect is in the nose fairing

The nose is a big surface where Coanda effect works, and it begins the rest aerodynamic behaviour.

Sepang test,  M1 show this ducted

Yamaha M1 ducted vanes

If the make the first calculates with the effective vanes, and only the effect the flow deflection and Cx=1 (all air into the ducted is deflected).

• Intake width = 0.1m
• Intake height = 0.3m
• Intake area = 0.03 m2 

YZF-M1

200 km/h

300 km/h

350 km/h

2 Ducted vanes

11,6 kg

26,1 kg

36,5 kg

MotoGP wings analysis

Then of MotoGP season 2016 where the all motorbikes y all categories was mount wings.

Today is banned, but I'd like on resume of simple analysis of effects and how it works. 

I am sure  that in the future the aerodynamics into motorbike have more weight in the design, the aerodynamics is not high relevant value, but in one world, where each tenth could be mark win or lose one race, aerodynamics can provide this tenth.

Aerodynamics basic concepts

Angle of Attack

The main effect is the angle between air and profile depend lifts generate, until one point where profile lost lift and only provide more drag, (stall angle)

Angle of Attack

Lift and Drag Equations

D is the drag force, which is by definition the force component in the direction of the flow velocity

L is the lift force, which is by definition the force component in the perpendicular of the flow velocity

  is the air mass density  1.205kg/m3.

v is the flow velocity (motorbike speed).

A is the reference area, (wings surface).

Cd is the drag coefficient provide for NACA profile data. 

Cl  is the drag coefficient provide for NACA profile data.

For calcule I used information with NACA profiles (this information is public in NASA webs)

Aerodynamic analysis 

Wing analysis

Ducati GP16 courtesy from Ducati

I estimate several measures

• Wheelbase 1400mm
• Rear SAG with pilot 30mm
• Fork travel 110mm
• Pitch full brake (fork fully compressed, rear wheel without load, rearshock extended) 5.7º
• Wing area 250mm x 100mm

Ducati GP13 braking

In the front part I used a thin profile NACA 65-206. This enter in stall quickly and provide low lift (Cl < 1) (down force) and low drag, this wing was used for Yamaha YZF-M1

• Straight mode with motorbike with full gas we put the Angle of attack (AoA) 6º
• In full brake the motorbike pitch 5.7º, therefore the AoA is 11.7º

NACA 65-206 charts

With 11.7º, this profile is in stall, this point is in brake, therefore Drag increase and provide a braking extra. The table provide the several data (10 N ~ 1 kg ~ 2.3 lb)

NACA 65-206	6,0º					11,7º
	100 km/h	200 km/h	300 km/h	350 km/h		100 km/h	200 km/h	300 km/h	350 km/h
L	8,14 N	32,54 N	73,22 N	99,66 N		2,32 N	9,30 N	20,92 N	28,47 N
D	0,46 N	1,86 N	4,18 N	5,69 N		1,39 N	5,58 N	12,55 N	17,08 N

In the side part I used a thin profile NACA 6412. This provide high lift (Cl > 1) (down force) and high drag, this wing was used for Ducati GP16

• Straight mode with motorbike with full gas we put the Angle of attack (AoA) 7.5º
• In full brake the motorbike pitch 5.7º, therefore the AoA is 13.2º

NACA 6412 charts

With 13.2º, this profile provide more lift, this point is in brake, therefore provide more force to tyres (like a weight) and provide a braking extra. The table provide the several data (10 N ~ 1 kg ~ 2.3 lb)

NACA 6412	7,5º					13,2º
	100 km/h	200 km/h	300 km/h	350 km/h		100 km/h	200 km/h	300 km/h	350 km/h
L	17,43 N	69,73 N	156,89 N	213,55 N		5,81 N	23,24 N	52,30 N	71,18 N
D	0,23 N	0,93 N	2,09 N	2,85 N		1,39 N	5,58 N	12,55 N	17,08 N

However, these profiles try to create less drag possible, therefore  if you have enough power to waste in drag, you could be increase the Lift forces. 

For example we can increase AoA without stall and increse Lift with slots in the profile 

In the F1, the top in racing aerodynamics Cl is over 3

Source Racecar Engineering

If we calculate with Cl 3 

Ranurados	Cl 3
	100 km/h	200 km/h	300 km/h	350 km/h
L	34,87 N	139,46 N	313,79 N	427,10 N

Each wing, generate 43kg with 350km/h, with 4 wings (one front one lateral, in each side) reach  174kg , this is the same weight of one MotoGP without rider

Behavior effects 

Another effect is the rider change his position in the bike, this create changes in aerodynamics

Motorbike Magazine courtesy

In corner when the rider try to leave the bike vertical and launch his weight to turn side, it create a wall where stop the airstream, and the lateral wing lost efficiency, and the other side create a roll effect like the rider put weight in the opposite side, this effect aid to take the turn.

Other effects in in the brake the pitch increase the Drag and Lift, and this provide more capacity to brake.

The antiwheelie effect, but normally, the speed in the exit is less and this effect is not the more important, beacuse, the wheelie is stronger in short gear, and this translate to low speeds

General drag, the vortex could be create two effects

1º Low the general drag like a golf ball, locate vortex provide less general drag

Locate vortex decrease the general drag 

NASA studies

2º Create a concentre vortex behind the bike, where concentrate turbulence and the motorbike behind shake by this turbulende. The air intake to engine could be affected for this tubulence. In 2016 season  riders complained for this effect. 

Security

The problem is if wing hit a rider in one accident or overtake. We could see that Force that must withstand so that it does not brake the fairing, therefore it must and hard part and could be injure to riders. Cruchtlow  warn this effect, and he has reason.

This is the first reason to ban the wings, other reason is cost increase due to aerodynamics studies.

In the future I will develop other post with how develop aerodynamics forces in the motorbike without wings.

Why should Yamaha to make a YZF R675? (2) The crossplane

Follow with "Why should Yamaha to make a YZF R675?", in this post I show a kinetic energy analysis.

Concept Crossplane

Yamaha sells the R1 engine like crossplane, due to the kinetic energy of parts into engine is due to each piston and the crankshaft.

Kinetic Energy of Piston and Crankshaft

The engine in rpm constant state, the pistons have a alternative movement, therefore have 0 and X kinetic energy, but the crankshaft, turn all time to the same rpm and therefore keep the energy. But the energy doesn't created nor destroyed, only transformed.

If we follow Newton's laws of motion, and law of conservation of energy, the energy of pistons must go to other part, therefore is energy, is gave and took other part of engine, in this case it is between crankshaft and other piston.

Engine Kinetic Energy 

And relation between parts keep the energy constant. In the cross plane we see the piston when two piston is closed to maximum speed, the other 2 piston is closed to minium speed and then Exchange the energy between them, and together keep the energy constant

Video Yamaha crossplane explained

Analysis crossplane concept in R6 and R675

If we resolve the energy equation to provide crankshaft speed, we can calculate the speeds and pistons and crankshaft balance.

Equation to resolve the crankshaft speed

In the R1 with crossplane we can see this behaviour.

Yamaha R1 crossplane behaviour, with constant speed in crankshaft and with energy constant.

In last figure show with crankshaft energy without mass, and we can see that it is very balanced between pistons, and this configuration keep the energy  with few variations.

If we see the other configuration we can see that they are less balanced or completly unbalanced.

Yamaha R6 flatplane behaviour, with constant speed in crankshaft and with energy constant.

Yamaha R675 behaviour, with constant speed in crankshaft and with energy constant.

However in the other post  "Why should Yamaha to make a YZF R675?" we can see the balanced in the engine for vibrations, this mass created a inertia and this works like flywheel.

In the other post we calculate the inertia into the crankshaft

• YZF-R6  = I' (1 cyl) = 0,0050 kg·m2 ; I' (4 cyl) = 0,0200 kg·m2 ; 

• YZF-R675  = I' (1 cyl) = 0,0058 kg·m2 ; I' (3 cyl) = 0,0175 kg·m2 ;

Yamaha R6 flatplane reduced the energy changes crankshatf in 0.49%.

Yamaha R675 reduced the energy changes crankshatf in 0.20%.

Therefore the crossplane don't have enough impact in the behaviour in the rotational  motion in the crankshaft, due to 99% of kinetic energy is the crankshaft.

Other aprox is the minimum crankshaft inertia, in ideal case, is due too for balance mass in the crankshaft, calculates in "Why should Yamaha to make a YZF R675?",

Basic Inertia crankshaft equation

• YZF-R6  = ICrankshaft = 0,000388359 kg·m2 ; 

• YZF-R675  = ICrankshaft  = 0,000714714 kg·m2 ;

 

Yamaha R6 increased the energy changes crankshaft until 20%.

Yamaha R675 increased the energy changes crankshaft until 4%.

But this behaviour could be to the R675 have more inertia, but if we put the same inertia in the two engines ICrankshaft  = 0,000714714 kg·m2 

Yamaha R6 reduced the energy changes crankshaft until 12%.

It only reduced the variations until 12%, 3 times more than R675.

If we compare the inertia on the engine, in speed for example 100km/h (36 m/s) of one motorbike with 250kg (180kg bike + 70kg pilot), we have 162 kJ  and into engine to 11.000rpm the the energy is:

• YZF-R6   ICrankshaft = 0,0200 kg·m2 ; Energy engine 13.3kJ   8,23% overall energy
• YZF-R675  ICrankshaft = 0,0175 kg·m2 ; Energy engine 11.7kJ,  7,22% overall energy

but we considered, that it needs more rpm for the same power in 4 cylinders against 3 cylinders, near of +20%, the energy in the 4cylinders reach 12% of engine,  

If we analyze the construction of engine, we can see, that the Inertia an balance mass have inverse behaviour.

Balance mass to radio and the same inertia to radio

We can see that in we increase the mass balance, but we put near or turn axis for keep the balance, we have less inertia

Relationship of design parameters 

Therefore if, we decrease the ratio an increase the mass balance, for example in we realize on drill in the crankshaft to r 30mm to axis, we can replace with lead to r 20mm and this weight provide 33% less of inertia. 

with this we can see that a weight material in crankshaft, down the global inertia, but the ideal, is light material in the crankshaft with heavy mass to balance, something like that, aluminium crankshaft with lead mass balancer.

Conclusion, it is the crossplane, with current steel crankshaft, it don't provide a significative improvement, but Inertia in the engine is very important.