Motorcycle Aerobody Research
 

What’s it all about?

Motorcycles with extensive or “full” bodywork are rare beasts indeed. Informed opinion, let alone genuine academic research into their aerodynamic performance is hard to come by. I’ve started this thread in order to open the debate and deepen the pool of knowledge, as well as supporting my own project, which could benefit from better sources of information.

If you have knowledge of good sources please post links. Personally I have found very little real scientific knowledge to be available. I do however come across quite a lot of misinformation and misapplication of aero principles from other disciplines.

My “pet” hate is the oft cited “centre of pressure must be behind the centre of gravity” which applies to bodies in free flight and is not directly applicable to road vehicles. Yet this phrase is routinely applied by “experts” in motorcycle dynamics. Even if true, it must be seen through the complex relationship between front and rear tyre slip angles, which I have never seen mentioned.

There seems to be a lot of conflicting theories about sidewind stability and how a low drag motorcycle would be affected. Is it more, or less prone to disturbance than a normal rider seated on a naked bike, and if so – why? My personal opinion is that the critical factor is body height, since a lower body also has a smaller moment around the contact patches.

I have been looking at some youtube videos of small-scale wind tunnels, with a view to building a simple version solely to investigate these issues. Making provision for a balance instrument that measures overturning forces at various angles of lean and yaw. I have never seen a motorcycle in a wind tunnel at anything other than upright and “zero yaw”.

Since the accuracy of numbers is not critical, we only need to understand the relationships, would a small-scale tunnel purpose-made for this task bring any benefit? For those with windtunnel knowledge, what would you imagine a suitable design to be – just to get a feel for the principles.

I'd look for whatever is available about the Ecomobile; they've been the living proof for decades.

Hi Frank - yeah I've seen a lot of stuff on that, but it does conflict!

Peraves make bold claims about sidewind stability and use the tests of the ecomobile being blown from one side in video ( I think you posted about that onanother thread, do you have a link for the video, I've only seen the stills) and photo images - yet there is significant deflection from the path

On the yahoo usergroups feet first forum, which is used by some Ecomobile owners, there is a different attitude, which leads me to think that the Peraves statements may be "sales talk"

Even so, its not the deep technical stuff I'm really hoping will surface in this thread.
Pete

My 2 cents.

Can i just say that enclosing the wheels will have a dramatic effect on aerodynamics, and make your goal easily achievable. You should look into the Human Powered Vehicle speed records for bicycles. Those are supremely aerodynamic vehicles capable of 80mph using less than half a horsepower! The basic outer shell design could be easily adapted to the scale of your vehicle to allow the same roominess, while still maintaining nearly the same drag coefficient as an HPV. Which is i think below 0.1cd.

On the HPV land speed record vehicles, i've read that nearly half the aerodynamic drag comes from the tiny slits where the wheels are exposed, as it does from the rest of the vehicle body. And these slits are for really skinny bike tires capable of only turning the front wheel an inch to either side. This goes to show how much aero drag an open wheeled vehicle can have in proportion to the aerodynamic body it's attached to.

Your goal is easily achievable, it just depends how much you want to sacrifice to styling.
http://www.rose-hulman.edu/hpv/images/sam_varna.jpg

An airfoil or tear drop is the most efficient shape. Concessions must be made to make it practical.
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One simple design trait I see in modern race motorcycles is that the bodywork between the wheels is designed to be just shy of dragging the ground under full compression. This smooths the flow, which wouldn't be an issue with a full streamliner, but also makes the Center of Pressure from the side as low as possible. Having the side CoP lower than the CG of the role axis aids in getting the best self correction in side winds by pushing the bottom of the bike more than the top to lean it into the wind. Trail also takes the side load and through gyroscopic precession leans the bike into the wind as the trail also countersteers the front wheel away from the wind to increase the lean further. You see this in dramatic fashion in the 50mph side wind test of the Peraves. It was blown off line 3 feet but leaned into the wind and automatically recovered in one oscillation.
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A "symmetrical wing with an angle of attack" is created by a bike moving forward at a significantly higher speed than the side wind. Venting the resulting pressure differential also helps reduce the (side) lift that is acting on the bike as Craig found out when he added doors to his streamliner and then had to take the back off when he found it was worse in side winds.
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Nose overhang is bad
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The human powered vehicle has way too much nose overhang which makes them very difficult to ride in side winds of more than a few mph.
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A pro rider can do 450 watts for an hour and 2000 watts for 10 seconds.

In fact the the world record holder said just that,about the incredible loss through the wheel openings.Had aerodynamics not been banned,[moto gp racing] by now we would of through real world testing learned what works and what doesn't.There is not a lot of hard data on vehicle motorcycle aerodynamics[mainly because they are void of any aerodynamics],I like, most of the people on this forum pass on little bits I read here and there.I do remember seeing a race version of the Ecomobile,single seat,short wheel base with a tail rudder.Like a arrow with feathers,the longer wheelbase and body workm does help with directional stability.

you said it yourself!
You are absolutely correct about the drag reduction measures, but my thinking (in this thread) is about aerodynamic stability. My observation is that there are areas where minimization of drag is critical, and they are mostly competitive events. Here though I hope to focus on issues of stability, particularly from sidewinds and other road traffic. As Scott says, these HPVs look quite difficult to control.

If I were a budding degree student, I would write my thesis on motorcycle aerodynamics. Its such a neglected subject area that anyone with access to reasonable equipment could easily become a world leader.

Maybe now is the time to redress the balance and push back against those FIM restrictions. I have always felt that motorsport governing bodies are misguided, but now it seems they have woken-up to how their rules shape future technology. Formula 1 rulemakers seem to understand how a framework can stimulate innovation, I wish the same was true of the motorcycle world.

I certainly feel that the future of motorcycle design is brighter than it has been, as the world wakes up to the concepts of efficiency and practicality.

Regarding the arrow with feathers concept and having tail fins sticking up as a rudder:
This is copied from the other motorcycle aerodynamics thread.
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http://ecomodder.com/forum/showthrea...-16754-12.html
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Thinking through the issue of side winds and motorcycle aerodynamics some more:
I question the theory of adding a long tail behind the rear wheel in order to improve stability. I know it is very aerodynamic and reduces wind drag from the front but will it make the bike track better in side winds? Adding a long tail makes the bike want to go straight through the wind like an arrow. So far, so good.
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Bikes don't turn from steering, they turn from leaning.
When a side wind hits the tail, it steers the front of the bike into the side wind. So far, maybe not so good. Bikes need to lean to turn, not steer. Does yawing the bike into the wind with the fin (rather than leaning) load the trail of the front steering geometry to cause a counter steering event that actually leans the bike the wrong way. Probably.
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Is the wrong way lean more than the right way yaw? Don't know.
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Another draw back to the rear fin is the sheer increase in area for the side wind to push on. Does it increase the ability of the wind to skid the whole bike to the side all at once? Definitely. The wet roads that I ride on half the time would be revealing.
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Does any increased fin area that is sticking up higher than the cg of the roll axis, ie a rudder, blow the bike over to lean the wrong way. Definitely.
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For motorcycles, keep your bodywork as small as possible while preserving low drag from the front. And the side. And keep the center of pressure from side winds as low beneath the cg as possible to help the bike lean into the wind the right way. And keep your cg high.

Try checking out Team Delft.

Human Power Team Delft & Amsterdam

Although they are working with streamlined bicycles, they have accumulated a fair amount of data about streamlining in the past few years which may apply to motorcycles as well. AFAIK each iteration has been tested in a wind tunnel. They are also the only other team to reach the 80 mph speed at Battle Mountain. Hopefully a lot of their info is public and available since they are a school.

This is correct. The vehicles at Battle Mountain generally race in near no-wind conditions and still can crash due to stability issues. Some of that has to do with rider input but any more than a few mph wind can easily blow these vehicles across the road.
JJ

So we can at least look at these HPV's to see what they are doing wrong.

Before adding the tail to my Honda Insight, I would have read your statement and agreed with you, as I had nothing more to add.

But, after adding the tail, and driving the car in some nasty 50 mph sidewinds, I have some comments to make.

1) In heavy sidewinds, the car still pushes the front. This is how the car was when I first purchased it, and it still remains this way after adding a 3.5 foot long tail.

2) The car has been driven on icy-slick roads in the winter, and yet still needs turning into the wind to compensate for high side pressure.

3) I would have thought that adding the tail would allow for more "neutral" steering, but this has not proven to be the case

4) The cross-sectional area of the tail, is I admit, much smaller than a tail on a tall motorcycle would be, so your point may be well taken for a more slab-sided air foil shape for a motorcycle.

5) Would be interesting to hear from any of the older members who have ridden in the Craig Vetter High Mileage Contest from the late 1980's.

I've got several articles scanned in from those days, and they are located here...

None of the articles make much mention about handling in high sidewinds however.

https://picasaweb.google.com/threewh...leAeroArticle3

Just adding to the discussion....

Thanks, Jim.

Tony Foale Designs, article on motorcycle aerodynamics.

This tells it like it is,again the long wheelbase helps,pushing the back out,turning the front into the wind for better control,where as the short bike gets blown off course and you have to gain control.

The HPV's are optimized for speed above all. If it can be ridden with "relative" safety it probably will be. However, all bikes are checked for particular safety requirements in case of accidents.

I wouldn't try to see what they are doing wrong, but see what they are doing right and modify that to work with everyday vehicles. The two technologies I like best are velomobiles(generally three wheelers) and the Segway gyroscopic balancing technology. I believe this or an extremely similar technology is being use in the Lit Motors cycle.

JJ

heres some more on side winds,interesting Stability Or Control

That is an excellent experiment with the string. Maybe the best position for the side CoP will be on the vertical line which runs through the center of the head set to best activte the countersteering of the trail. But still as low as possible below the roll CG.
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With the string tied at the head tube, Max pulled sideways (gently at first!) and I found that it was very easy to make a slight steering correction to return the bike to roll-and-yaw equilibrium and to keep the path essentially straight. With a little practice, I was steering and rolling the bike slightly and could resist as much side force as he could pull. Sharply varying side forces (gusty winds) were tried next with the same ease of control.


Next, we moved the string back to the seat post simulating a CP aft of the CG. We kept the height above ground the same. Here the control required was much more difficult. With practice, I could steer and roll the bike to counter this side force but there always were several big swerves and the heading always changed. A varying "gusty" side force was very difficult to
control -- most of the effort went into roll stability (keeping balanced) and the heading went all over the road!


Finally, we moved the string back to the head tube and reversed the front forks to increase the trail. Now the side force also produced a large steering torque. This torque steered the bike "down-wind" which resulted very quickly in a roll angle "up-wind", just what is required to "lean into the wind". With a loose grip on the handlebars, the bars wiggled around as the string was jerked but the bike kept going nearly straight.

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The first question I have is where do the reaction forces take place when a side wind acts on a motorcycle? Newtons 3rd law.

Good point. The strings experiment is interesting but less relevant than I first thought. It is only a side wind when the bike is parked. Any time the bike is moving forward faster than the side wind's velocity, the apparent wind will be a vector off of the front. Making the streamlined bike a symmetrical wing with an angle of attack.
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https://fbcdn-sphotos-a-a.akamaihd.n...94962551_n.jpg
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regardless of where the static CoP from the side is, The streamline shape with an angle of attack will have the greatest lift (side) force somewhere toward the front near the point of maximum width.
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Thanks to 3-wheeler and godscountry for two useful sources.

As Scott says the string tests were quite insightful, but ultimately difficult to quantify and that makes it impossible to draw scientific conclusions – but thought provoking nonetheless.

The Aero articles, centring on 80’s Vetter mileage contests, and particularly the wind tunnel testing of different types of motorcycle were most useful. This is some of the most accurate information I have found available – published windtunnel numbers from a reliable source.

In this article https://picasaweb.google.com/threewh...leAeroArticle5 page 2
The figures for the rifle faired Vetter Challenge bike were a shock –Cd 0.3627.
This is way higher than I would have imagined for a streamliner. I don’t imagine that my design would be as good yet I was hoping for a lower figure – some recalibration of my targets may be in order.

I cannot remember where, but I recall a Cd 0.19 for the Peraves Ecomobile and I based my expectations on this figure. Now, in light of this article I question if the eco could make that number. I wonder if we could compile a table from different sources of the top aerobody designs.

I wanted to post a link to a page that I feel contains some of the best information on the stability issue. Its from Kraig Schultz’s Deltabike site and it draws on some opinions of highly influential designers.
Delta Bike USA - Forge Design Competition A - Cross Wind Stability

Even in this page there are some discrepancies between views
“but leans automatically into the wind, the more forward the LCP (longitudinal center of pressure) the more leaning against the wind. “ is a quote from Arnold Wagner (the Ecomobile designer)

and this appears at odds with the views of Royce Creasey who wrote
“ This 'rollout' force should be minimized and this has been done by keeping the nose area fairly low”

Many other people have made the assertion that a rearward biased centre of pressure is most desirable, but I feel this is influenced by misapplication of principles that apply specifically to bodies in free flight. Arnold’s design seems to contradict these ideas, has a high side area and a rearward CofG. The ecomobile shell has no obvious transition points to initiate detachment of cross flows, yet it looks like the most stable vehicle in this class.

All of which seems to muddy the waters.

This is a good article but there are a couple places where he miss-spoke.
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Tony Foale Designs, article on motorcycle aerodynamics.
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From the article:
Him..."The component of the wind side force, acting at the front of the machine is passed to the road surface through the tyre via the steering axis, but the steering axis is in front of the tyre contact patch by the amount of the trail, and hence the sideways force on the bike will tend to steer the wheel with the wind. Exactly the situation that we might wish to avoid"
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Me...Bikes don't make lateral acceleration without first having to lean. He is correct in saying that the trail will take any side force that acts on the bike and translate it through the steering geometry to turn the front wheel WITH the wind. But this exactly what we DO want. The wheels are way below the CG of the roll axis and much lighter than the core of the bike/ rider, so the nose of the bike moves with the wind very little while the wheels counter steer freely out from under the bike by a great amount. Which makes the bike lean and corner into the wind.
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His 3 summations at the end are all not quite right.
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Him..."1. Smaller wheel;----- The precessional forces will be reduced in line with the reduction in weight close to the wheel/tyre circumference. This will reduce the coupling between yaw and roll movements."
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Me...He is saying a lighter wheel is more stable but I disagree. It is true that a lighter/ smaller tire and wheel will make less gyroscopic force but if you want more stability, you want more wheel. Yaw forces from a side wind acting on a vehicle with front and rear tires planted to the ground will be miniscule compared to the roll forces and the lateral forces. Unless there is a huge overhang to shift the Center of Pressure, the yaw force will be applied somewhere between the two contact points and have very little leverage. The gyroscopic interaction of yaw, roll and steering in the front wheel with trail is ideal. Side winds will act well above the contact patches and try to roll the top of the bike with the wind. The precession of the movement of the top of the wheel to the right is to steer the front of the wheel to the right. Good. Exactly the counter steering input we want in order to lean and corner to the left, into the side wind. There will now be a slight yaw of the front of the bike to the right, not so much from the side wind, but as the rear wheel tracks to get back in line. Any slight yaw of the front of the bike to the right (whether from steering or the force of the side wind acting at the aero point of max differential, which will always be forward of the CG of a fast moving bike, even with a tail), will precess to roll the top of the wheel into the wind. Very slight but in the right direction again. And the counter steering input that the trail imparts away from the wind to the right, precesses the same way as the yaw, by forcing the top of the front wheel to lean into the wind. Good again.
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A bigger wheel/ tire is more stable. We already knew this.
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He then states that less trail is better in side winds:
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Him..."2. Less trail;----- The component of the wind side force, acting at the front of the machine is passed to the road surface through the tyre via the steering axis, but the steering axis is in front of the tyre contact patch by the amount of the trail, and hence the sideways force on the bike will tend to steer the wheel with the wind. Exactly the situation that we might wish to avoid."
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Me...Automatic counter steering from increased trail is exactly the situation we might wish to implement. More trail equals more stability. At the expense of requiring heavier steering efforts.
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Him..."3. Zero offset;----- With normal steering geometry with about 1-2" of offset, the bulk of the wheel side area is forward of the steering axis, this combined with the effect of today's large tyres and discs means that a considerable steering force can be generated by the action of a side wind on the wheel. But with the zero offset geometry used on the hub-centre arrangement, this wind force is balanced about the steering axis and no turning effect is produced."
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Me...Not quite right again although much less of a factor than having too little trail. Looking at just the wheel assembly, a slight bias of the CoP toward the front will tend to generate a beneficial counter steering force.
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It is a good article and he clearly addresses the aero issues of side winds and at what point they act on a fast moving vehicle which is nowhere near the static side CoP, but (like many of my own hurried posts) some of his statements could benefit from some proof reading and constructive discussion.

The Delta 11 has an inherent design disadvantage in cross winds of an ultra low CG from the batteries. But he still seems to manage. The important thing to keep in mind is that the lift (side) of a fast moving vehicle in side winds is nowhere near where you think it is by looking at the static side CoP. And having it centered on the steering head may be better than having it further back, like an arrow, until you get up to salt flat speeds where the tires are barely contributing to the direction control.
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Is a big streamliner easier to blow off the stand? Yes. Is it worse in side winds on the road? Not necessarily.

I would have also thought the Rifle bikes would have a lower cd. Too short I guess. The other big surprise is the race bike at still way over .6cd. This shows that the front of a vehicle is way less important than the rear.
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https://sphotos-b.xx.fbcdn.net/hphot...28346871_n.jpg
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https://sphotos-b.xx.fbcdn.net/hphot...48480311_n.jpg
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https://fbcdn-sphotos-d-a.akamaihd.n...42126275_n.jpg
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Do you remember BMW's concept vehicle the Simple ?I maybe off a little, but I thought it had a cd of 0.18.What's interesting is the body consist's of mostly flat panels.With some photographs and scaling it may be a good choice for your vehicle.It looks good and it would keep the cost's down.You could in fact build it out of aluminum honey comb panels and some Kevlar.I would suggest a couple of cross bars[chromemolly] with disconnects to protect your sides or if you use a door,incorporate it into the door or doors.

MC streamliner info
 

*There is a very good SAE Paper that was published for the HONDA Hawk MC streamliner project which has heavy emphasis on directional stability.
*The Easy Riders' dual-engine Harley-Davidson remains the fastest bike I believe.It's body was tested at Texas Tech in 1990 and returned Cd 0.11.
*The E-Z HOOK MC streamliner is the fastest single-engine bike and its body was developed in the Cal Tech wind tunnel and was reported as the lowest drag of any wheeled vehicle ever tested there,at Cd 0.103 If memory serves me.
*Early 1950s (NSU,Moto-Guzzi,etc.) streamliners from Germany,Russia,and Italy in most cases had provisions for rider body re-positioning/weight shifting as an aid in crosswind conditions by way of body openings.
*The IHPV competitions and USFRA racing at Bonneville have limits for crosswind conditions on the course.I've seen cyclists in the weeds at Battle Mountain.They have no provision for weight-shifting inside the body shells and are at the mercy of gusts.

Unfortunately, these land speed vehicles are so far removed from daily drivers that very few of their design characteristics apply.

The AeroBike Enclosed Motorcycle
 

Here's the AeroBike, made by some guy in the UK over the last couple of years.

AeroBike Enclosed Motorcycle

The lean of a body might cause a bit more lift from side wind than at vertical. Angle of attack affects lift and in turn traction. I would like to try using stretch material such as Lycra to allow a rider to put a knee down. It might be that the change in shape would reduce side lift and add a bit drag to steer into the turn.
Bicycles using front disc wheels have not worked in crosswinds. Trek has an article on its aero shaped tubing which is a 5:1 airfoil with a Kamm length to meet rule requirement.
Sport Rider magazine did an article on wind testing motorcycles in 2006. The racing rules limit the height of the body work behind the rider.

http://www.vintagesailplaner.com/Sheet1bis-9.pdf
This is the drawing of a vintage glider fuselage that I believe is a useful starting point for a motorcycle fairing. The number 6 bulkhead is about optimum for a Kamm tail. Zoom out to 25% size and rotate right (clockwise)

A Cd of 0.36 seems high to me as well, but several comments are in order:

1) The Insight has a advertised Cd of 0.25
2) At 35 mph, it coasts about 1/4 mile and ends up at about 20. This is an estimate so don't quote me on it.
3) My Honda VF500 only coasts about 1/8 mile and is not going 20 mph at the end. It has a custom full size fairing, and I would guess that it's Cd has to be closer to 0.8.
4) The car gets 40 more mpg than the bike in the summer (120 vs. 80)
5) The egg-shell fairings at the end of Craig Vetter's High Mileage Contest were good enough to achieve 480 mpg, so a motorcycle *can* be very efficient with fuel.

Jim.

In 1928 a man named Ernst Henne bought a BMW R37, he then took it apart and thew most of the bits away. Once he had the bike back to its bare essentials he set about building one of the most successful record breaking motorcycles ever built.

All in all, Ernst Henne’s BMW took 76 world records with the bike staying in a state of active development for 6 years between 1929 and 1935. In ’29 he set the fastest ever recorded speed for a motorcycle at a blistering pace of 216.75 km/h, by ’35 Henne had developed the car to the point he set an all new motorcycle world speed record of 256 km\h. That’s fast by today’s standards and he did it all in a backyard shed before the start of WW2.

The BMW R37 had a twin cylinder engine in a boxer configuration, the total capacity was 749cc and the bore/stroke was 83mm/68 mm. It’s estimated that with the supercharger installed, the engine was producing 100+hp, a staggeringly high number in 1929 and significantly higher than almost any road car of the era.

Ernst Henne's Supercharged BMW R37 - (SILODROME)
http://silodrome.com/wp-content/uplo...percharged.jpg

http://3.bp.blogspot.com/-nVEYMU2ubI...600/nsu007.jpg



This fabulous 2-cylinder, 250cc, Rennmax NSU out 36hp @ 11000rpm dominated the sport in 1954. Werner Haas of Augsburg defended his world championship in superior style, by decisively winning the first four World Championship races on the silver Dolphin. The bike could go 131.4 mph, an astonishing feat for such small displacement. NSU had a 6-speed transmission, and weighed in at only 117 kg complete with fairing. NSU only built six of these bikes and were not-for-sale factory racers.

If I'm correct,Authur Wagner,Peraves,designer and builder of the Ecomobile had built gliders before building his enclosed MC.I have always said,glider cockpits ,fuselages make for a great start in building a low drag enclosed Motorcycle.Thanks for the post.

On the Delta-11, it actually doesn't have a low Center of Gravity due to low battery weight. Two of the battery packs, the external ones, are mounted high (they weigh 100 lbs total). These external packs are about the same as having an extra rider on the bike. I believe this helps stability in gusts. The bike now has 8,500 miles on it and I'm very happy with the handling under wind speeds of 25mph. When the wind gets stronger than that, it's unnerving and I worry about safety when I am crossing a local metal grated bridge - I always wonder if I'll have enough traction for the wheels to not slide sideways from under me. Here is a link showing the location of the external battery packs.

The bike self corrects for wind gusts when the wind velocity is less than 25mph. Above that, I have to admit that I'm a bit of a chicken about seeing what will happen, having the nagging memory of how I was pushed across the centerline into oncoming traffic on a 600cc Ninja in high gusting winds...a few years back.

What's tricky is not riding on straight roads during gusting, the bike does a great job of self correcting and I just sit there and let it lean itself correctly. What's tricky is leaning into a high speed corner in traffic and then getting hit with gusting winds. You need to lean to steer through a corner, and then the lean is being affected by a gust, the question of how to compensate the lean is urgent. Will the gust intensify or diminish? It doesn't happen regularly or with predictability so it's hard to study - but it does cause my heart to skip a beat or three when it happens.


http://www.schultzengineering.us/june4a.jpg

My mistake. You have had so many different versions of your electric streamliner it is hard to keep track. I was thinking of one of your drawings which showed a stack of lead batteries along the bottom, under your legs.

Here is a good page on cross winds.
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Delta Bike USA - Forge Design Competition A - Cross Wind Stability
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To my mind the main issue with streamlining is lift from crosswinds and how to kill it. (I an using lift in the sense of a force generated by an airfoil with a positive angle of attack not as in vertical lift.) I imagine front mounted spoilers in the same region where vortex generators are placed on wings They could be either passive or active. This would reduce side lift dramatically. As we all know, streamlining reduces the force transmitted by the wind to the vehicle except when lift is an issue.

As an example, I know that nascar vehicles have strakes on the roof, parallel to normal flow which act as spoilers to kill lift if the car goes sideways. I have also seen this in Hucho somewhere in relation to sidewinds on cars or trucks

An active system could use air pressure differences to activate spoilers on the lift side in gusts although moving parts are less attractive than passive spoliers.

This narrow focus on C of P could be why there is so much discussion around tails and why weight and center of pressure fixes did not work. Don't move the lift or the C of G, Kill the lift! If there is still lift generated at the front of the bike it does not matter much how long the tail is, it will still cause a large side force near the front of the bike.

My $.02

The lift (side) from yaw winds creating an angle of attack to the symmetrical airfoil of a streamlined motorcycle can be minimized by venting the resulting pressure differential across the rider's legs and lap. Which must be open for egress and holding the bike up at stops anyway.

That's why most modern faired motorcycles are OK in crosswinds.

I was addressing enclosed bikes, although there would still be lift created on the section in front of the rider gap which might still benefit from a yaw spoiler.

The cross section of the body and the ground clearance go a long way in determining side lift and drag. The fairing I built for a city bike is essentially two cones, two feet from the ground. It is barely affected by cross wind. Generating down force instead of lift is key to stability along with reducing drag.
The dustbin fairing Kraig is using generates lift. The cross section is close to being a circle. A tail section helps turn the body into the wind. The Morelli/Aptera body has an horizontal oval shape for lower side drag. The shape looks to be a symmetric air foil with the center line bent in a shallow S curve.
The stability versus response balance is often a rider's preference. A low nose and a higher tail box seems to be a good balance to reduce lift and drag. Angled strakes at the nose can generate down force at the price of more drag.

The Monotracer,fully enclosed,has no real problems with side winds.Long wheelbase,with lots of surface area behind the center of gravity,kind of like a arrow with feathers.The Monotracer turns into the wind,people who have been in it says its does the opposite of what you would expect.I really think ,looking at sales of high mileage[Toyota] vehicles,people will embrace the technology.I think a body like the BMW Simple concept packaged on a tilting chassis or 2 wheel motorcycle platform would work,safe,comfortable,incredible range with it 0.16 cd ?no matter what the propulsion.Lit Motors ,generated a lot of interest,whether or not they can deliver is to be seen.they are going to control the lean via the gyros.I always thought ,the best is the natural physics,no mechanical assist,but it is very complicated process and I'm not a expert on the physics of the steering input,lean etc internal,external forces etc.Learn math, guys and gals,at least you can come up with some numbers to work off of.:o