Introduction & Cross wind solutions to motorcycle Streamliners?

[PeterS]

I've been reading but not contributing .... for the very simple reason that I learn more by listening .

Ironside do you have a side on photo of your fairing ?

and thanks for the input , this has been really useful!

[Ironside]

PeterS - look for 'Recumbent Honda 90' thread, I'm sure you'll find something there.

Teri - I would have no problem whatsoever riding in close proximity to another vehicle in the conditions I have already experienced, so long as the 'stall strip' was installed. Without it I would certainly not be comfortable, such is the difference with and without.

As I mentioned earlier, by a 'seat of my pants' feeling, I could feel the bike being moved by the wind (is that roll or yaw?) but it could still be steered within inches with little or no steering input. I suppose it must be self correcting, or what Royce would call 'good cross wind indifference', quite amazing as the all up weight is around 180 Kg.

I don't know how bad conditions would have to be before they become 'too bad', I expect I'll find out, hopefully before I end up in a hedge or as you might say 'on a grassy verge' ?.

Visionary -

But heh, a genuine world leader!

Praise indeed, but I'm just a tinkerer capitalising on the hard work of others.

I'm happy to share the results of any further testing, in the hope that others with more knowlege can come up with something that would benefit us all.
I got 2 metres of 20mm x 30 mm of 'L' profile plastic today, guess what I'm doing tomorrow.

I found the fan tuft test useful for showing the airflow over the panniers and top box, there's more work to be done in these areas, so I won't abandon that just yet.
I'm sure something can be arranged with regards real world tuft testing, the 'funny looks' I get don't bother me much.

Please stay in touch, we are not a million miles apart geographically or in our aims and ambitions, maybe our paths will cross and we can compare notes.

Pete.

P.S. Please don't be offended by that English/Welsh thing, I wouln't use you as target practice any more than I would my Scottish or Irish neighbours.

[Michael Moore]

One of the things that Tony Foale wrote about is that with a FFE (funny front end) with steep rake (around 13-16 degrees) you don't need any offset between the steering axis and the wheel axle to have sufficient trail. That lack of offset means that the side wind blast against the wheel is balanced to either side of the steering axis. With a normal rake and fork clamps that are offset 50-75mm moving the axle in front of the steering axis the wind blast will push the wheel around the steering axis and perturb the steering.

cheers,
Michael

[Teri_TX]

Originally Posted by Michael Moore

One of the things that Tony Foale wrote about is that with a FFE (funny front end) with steep rake (around 13-16 degrees) you don't need any offset between the steering axis and the wheel axle to have sufficient trail. That lack of offset means that the side wind blast against the wheel is balanced to either side of the steering axis. With a normal rake and fork clamps that are offset 50-75mm moving the axle in front of the steering axis the wind blast will push the wheel around the steering axis and perturb the steering.

cheers,
Michael

Hi Michael,

Please don't think I'm picking on you.

Is the "offset" you referred to an imaginary line (as viewed from the side, otherwise known as elevation view) from the rotation axis of the steering axis (about the bearings in the head tube) and the wheel bearings?

<rant on>

Maybe it's me but I get awfully confused whenever bicycle and motorcycle people speak of front fork geometry. To me, it is SIMPLE GEOMETRY and nothing more, confounded by terminology concocted by the respective groups (bicycle or motorcycle).

From simple geometry, a steep rake will inherently put the center of rotation of the steering axis far ahead of the contact point of the tire unless there is a huge offset of the fork clamps or a non-parallel clamping of the forks. Most of the fork clamps I've seen appear to be interchangable (maybe not). That difference is the trail.

As an aside, a steep rake will cause what (to my knowledge) is known as "flop" which causes the front of the bike to raise and lower as the forks are rotated about the steering axis. This is a separate effect on the handling.

Bicycle people argue a lot about forks that have bent lower ends toward the front and straight bladed forks as to whether which has less or more trail. A straight bladed fork can have exactly the same trail as the bent ones if the attachment angle at the head tube is adjusted accordingly. To this engineer, it's just elementary geometry and no magical fairy dust. It's my opinion that most bicycle people are simply "geometry challenged".

<rant off>

-- Teri

[sendler]

Most of this has been well discussed in the "windy slope" thread:
.
http://ecomodder.com/forum/showthrea...tml#post285297

[Teri_TX]

Originally Posted by sendler

Most of this has been well discussed in the "windy slope" thread:
.
http://ecomodder.com/forum/showthrea...tml#post285297

???????????

Not that I know much (practically none) about motorcycle dynamics or bicycles (which I have ridden extensively) the discussion left me even more confused.

However, further down at post #149 your link to Tony Foale
Rake and Trail made the very muddy water a bit clearer.

Interesting discussion but this is threadjacking. Please start another thread.

This thread is about aero fixes for improving cross wind behavior.

-- Teri

[PeterS]

Hightechpete ?? Ironside ?

[sendler]

Originally Posted by Teri_TX

aero fixes for improving cross wind behavior.

Not threadjacking. Just guiding you to some reading to answer your questions so we don't have to sit and type it all out again. Tails and rudders were considered at length.
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The Tony Foale pages were very ingenious to show that trail, not rake angle, is the active ingredient in making a motorcycle stable regardless of rake which is really just set as a compromise between withstanding the bending forces that are trying to push the wheel back when you hit something, and the weight of the bike trying to bend it forward. But I disagree with some of his statements regarding longitudinal center of pressure and long tails which are true for an airplane but are more complicated and counter intuitive when you still have two wheels stuck to the ground that are far and away the determining factor on the path of movement.
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The interesting addition to the conversation that was brought up in this thread was the nose foiler. I wonder if that is why many modern sport bikes have some sharp protrusions in the front bodywork on either side of the headlight?
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[Teri_TX]

Originally Posted by sendler

Not threadjacking. Just guiding you to some reading to answer your questions so we don't have to sit and type it all out again. Tails and rudders were considered at length.

Hi Sendler,

Sorry, I didn't mean to sound so harsh. The position of the link you sent was an endless confusing argument of bike handling. However the link to Tony Foale was very interesting. I hadn't seen it before and it doesn't show in his articles link. How did you find it?

Tails and rudders are indeed a point of disagreement among other things, I'm neutral on them so far. Indeed, much is endlessly re-hashed in forums but not everyone reads every thread (and can remember). Posting a permalink to the applicable discussion would be extremely helpful and enlighting. Please do so when you can so your fingers can get a rest

The Tony Foale pages were very ingenious to show that trail, not rake angle, is the active ingredient in making a motorcycle stable regardless of rake which is really just set as a compromise between withstanding the bending forces that are trying to push the wheel back when you hit something, and the weight of the bike trying to bend it forward.

Going off topic for a moment, Foale's article cleared up a point I had always been curious about. His conclusion would suggest the Hossack or BMW's implementation, the "Duo-Lever", would be the ideal front suspension. For scratch builders of a streamliner not constrained by convention and appearance, this may be a fruitful approach.

... But I disagree with some of his statements regarding longitudinal center of pressure and long tails which are true for an airplane but are more complicated and counter intuitive when you still have two wheels stuck to the ground that are far and away the determining factor on the path of movement.

In my opinion, the Center of Pressure (CoP) should be slightly behind the Center of Mass (CoM) but not excessively so. Vetter is a long tail advocate mainly because of his obsession with lower drag. Hard to argue with but sometimes "too much is just too much" (vs. "too much is not enough") and a compromise must be made. Modern sailplanes have their rear empennage on a long boom for yaw and pitch stability due to their extremely long wings to avoid "close coupling". "Close coupling" makes for extremely manueverable airplanes but is potentially very dangerous for anything but aerobatic and fighter planes. Even 4th and 5th generation fighters aren't close coupled but are inherently unstable (for other reasons) anyway. The weight of the boom is a negative but it is a compromise for yaw and pitch stability. I am of the opinion their cockpit profiles are merely low drag envelopes and contribute little toward any other handling aspect contrary to someone's opinion.

The interesting addition to the conversation that was brought up in this thread was the nose foiler. I wonder if that is why many modern sport bikes have some sharp protrusions in the front bodywork on either side of the headlight?

I've wondered about this (sharp protrusions) too. I initially dismissed this as merely a styling exercise but I wonder if they have accidentally stumbled onto something. I believe they do this as Viagra (as if they need it) for wannabe boy racers. Spoilers, strakes, foiler, or whatever you care to call them would cause turbulance and drag on both the upwind and downwind side contrary toward Fuel Efficiency (FE). Conventional motorcycles are anything but low drag. Virtually everything on ordinary production motorcycles is for raw performance and appearances as this is what the market demands. Our goal here is FE which means low drag is a requirement. We have to keep our eyes on the prize, fuel efficiency. When subsidized (yes, it is) gasoline in the US gets to EU (and intensionally taxed) and unsubsidized prices, maybe FE will become the market demand.

Have you considered puting a stall strip (temporarily) on your bike's nose? Pete's [Ironside] initial experiments are easily implemented on any fairing. From your other postings, you report your Honda is very stable in cross winds with you laying on the tank. What about other body positions? At my age, bending my neck so extremely in a belly on the tank position is an absolute NO-NO for more than a couple of minutes.

Meanwhile, I eagerly await the results of Pete's [Ironside] additional experiments with the "L" sections he purchased.

-- Teri

[P-hack]

Originally Posted by Teri_TX

Tails and rudders are indeed a point of disagreement among other things, I'm neutral on them so far.

From my perspective, their use is limited by wheel traction. That becomes the fulcrum in any aerodynamic counterbalance.

Originally Posted by Teri_TX

Vetter is a long tail advocate mainly because of his obsession with lower drag.

gotta agree with him that is the ideal, and nose fences and cross ventilation and steering geometry and short tails and etc seem to be workable compromises with already proven examples, so the target again becomes efficiency for those wanting to maximize efficiency.

Originally Posted by Teri_TX

Modern sailplanes have their rear empennage on a long boom for yaw and pitch stability due to their extremely long wings to avoid "close coupling".

Not entirely. A longer boom means the frontal area of the empennage can be smaller. You don't need as much control surface area on a long boom so you can lower overall drag and have the same moments.

Originally Posted by Teri_TX

Our goal here is FE which means low drag is a requirement. We have to keep our eyes on the prize, fuel efficiency.

And that is why vetter likes long tails and wants to find solutions that enable them. Streamlined is streamlined.