Introduction & Cross wind solutions to motorcycle Streamliners?

[Otto]

For these strips, as noted previously I suggested L-shaped clear plastic corner reinforcements for drywall, from a home improvement center:

http://www.corner-guard.com/componen...0ba0a7de04.png

The idea noted above of using a piece of 7mm rope, taped to the fairing, is probably better than mine, perhaps cheaper, too.

Here's a thought, if using L-shaped plastic: Why not cut it with pinking shears, such that its edge is a zigzag? This might turbulate the cross wind as well or better than a uniform wall height, with less drag.

Thoughts?

Also, in the movie World's Fastest Indian (now available on Netflix, well worth watching) Burt Munro's motorcycle fairing has a longitudinal ridge similar to what we're discussing here:

https://encrypted-tbn0.gstatic.com/i...FI6pL7Irtd0kEX

I'd assumed it was a simple external joint for the two fairing halves, but now I wonder if (assuming the movie prop is a true replica) Munro had sorted out this crosswind device 50 years ago. Anybody know?

[Ironside]

Otto, thanks for your suggestions, rope was the easiest and quickest way to asses effectiveness, it will be replaced by something more permanent when I'm satisfied that I've optimised the size and shape of the 'stall strip'. In the meantime, the rope or something similar will stay, I wouldn't want to be without it now.
I have a copy of 'The worlds fastest Indian', one of my favourite movies.

After reading Tony Foal's article on aerodynamics (again), noting that a side wind combines with the head wind, to create an airflow at an angle to the machine. I set the fan at a 30 deg. angle from 'straight on', this seemed to have the most effect on the tufts.
I was careful to ensure that fan was not moved, so all the parameters apart from the stall strip were identical in both videos.
According to Tony Foal, an unstreamlind shape causes eddies and a low side force and is less affected by side winds. So I was looking for an early separation of the flow with the stall strip installed.
To be honest, I can't see any discernible difference, but then again I don't know what I'm looking for.
Here are the videos, I had to use my mobile phone to record so the quality is not special. Make of it what you will.

Click on the image to play.


[IMG][/IMG]



[IMG][/IMG]

[Teri_TX]

Hi Low&Slow,

Originally Posted by low&slow

Hi Teri, Welcome to Ecomodders! Interesting discussion about the storm strip in front of the nose. I got into streamlining almost 4 years ago and have enjoyed some success with my bikes.
<snip>
I run a Vetter fiberglass nose and I built a Vetter-style tail using plywood, doorskin and fiberglass.
<snip>
Craig's , Alan's, Terry's and mine are pretty similar in profile. All us do pretty well in windy conditions though Craig's struggles a bit more than ours. We suspect is due to the Helix scooter steering geometry , low center of gravity and small wheels.

As I alluded to in a previous post, motorcycle system dynamics is largely an unknown science (Honda probably knows a lot more). A quick search shows the Ninja has a smaller trail than the Honda CBR250R. Not a lot but less. I can't find the trail spec for a Honda Helix. Tony Foale said less is better in side wind conditions. I wonder if the Helix's trail is the reason. Roller skate wheels can't help either.

I agree that the Honda cbr250r is a good choice as your base platform. Single cylinder , fuel injection and water- cooling are all desirable features. Sendler has had great success with his. The Ninja 250 is cheap, durable and does surprising well despiteits sport tuning. Good luck with your efforts !

The Honda CBR250R is just my paper (so far) choice. Unfortunately Honda has only produced them for only a few years before bumping up the displacement to 300cc while Kawisaki has made the Ninja 250 for a 1/4 century! No wonder there are more Ninja's available. I really dislike excessive noise and a screaming Ninja motor inches from me is a disincentive. Long life is likely less due to the higher rpm's.

I'm retired on a limited budget so getting a base bike is a large investment for me. I may have to settle on a Ninja for financial reasons. I suppose someone out there makes a muffler for less noise although preliminary search shows the very opposite! I guess a car muffler can be used with some possible extra back pressure (maybe not) penalty.

Back on topic, Craig just replied to me and said his prelinimary testing indicates a stall strip seems to help a lot. I'm waiting for his full report.

Edit: On another "problem", long tails, Vetter has said his long tail presents no problem for him. Others may have a storage problem in their garage or shop. Has anyone considered a hinged tail like Navy carrier aircraft wings? A simple double hinge link would allow the extra tail length to fold back on itself for storage.

-- Teri

[Teri_TX]

Hi Otto,

Originally Posted by Otto

0Here's a thought, if u
sing L-shaped plastic: Why not cut it with pinking shears, such that its edge is a zigzag? This might turbulate the cross wind as well or better than a uniform wall height, with less drag.

Thoughts?

An interesting thought. Pinking shears I've seen are have pretty small zigzags. Also, unless made of something compliant like rubber they could be hazardous if you brush against it or worse yet hit a pedestrian. The victim's lawyers would have a field day! I've said before that a simple fence behaves as a degenerate form of a stall strip (on aircraft they are usually triangular in section). Maybe a line of vortex generators set in a straight line rather than the usual angle would be more effective. Again, they should be made of something like rubber to avoid injuries. However, a fence or similar would almost always produce turbulance (and drag) on the lee side as a perfect head on apparent wind is a very transient condition at best. I would think a small amount of lateral lifting force is acceptable for very low apparent cross wind angles. A proper triangular stall strip would be nearly "aerodynamically transparent" until the apparent cross wind angle exceeds the half included angle of the stall strip.

I hope I'm not using too scientific/engineering terminology for most readers, that's my training and nature.

Also, in the movie World's Fastest Indian (now available on Netflix, well worth watching) Burt Munro's motorcycle fairing has a longitudinal ridge similar to what we're discussing here:

https://encrypted-tbn0.gstatic.com/i...FI6pL7Irtd0kEX

I'd assumed it was a simple external joint for the two fairing halves, but now I wonder if (assuming the movie prop is a true replica) Munro had sorted out this crosswind device 50 years ago. Anybody know?

I looked at the picture you linked to and studied it. The longitudinal ridge is obviously more than a body section join line as it is rectangular in form (as far I can see from the AMA's museum (I think) replica) and continues on the top of the tail.



The fiberglass can clearly be seen to roll over the edge of the rectangular section The rectangular section could simply be a practical implementation to provide a structural stiffener when the halves are separated. Otherwise they would be a bit floppy and difficult to handle. A preliminary Google search for it's aerodynamics has yielded nothing so far.

Maybe Bert (original spelling per Wikipedia) Munro stumbled onto a stall strip a half centry ago. He seemed to be the "tinkerer type" of guy and not much of a scientific documentary type person. He apparently died with his reasons.

As George Santayana said: "Those who cannot remember the past are condemned to repeat it". In my defense, I never knew it, so I didn't forget!

-- Teri

[Teri_TX]

Hi Pete,

Originally Posted by Ironside

Otto, thanks for your suggestions, rope was the easiest and quickest way to asses effectiveness, it will be replaced by something more permanent when I'm satisfied that I've optimised the size and shape of the 'stall strip'. In the meantime, the rope or something similar will stay, I wouldn't want to be without it now.
I have a copy of 'The worlds fastest Indian', one of my favourite movies.

The rope is a very practical implementation. In fact, if it were mine, I'd leave it as nautical note, maybe a couple of loose "figure 8" knots to add to the nautical theme After all, the English have a proud naval history.

After reading Tony Foal's article on aerodynamics (again), noting that a side wind combines with the head wind, to create an airflow at an angle to the machine. I set the fan at a 30 deg. angle from 'straight on', this seemed to have the most effect on the tufts.

30 degrees in real life would be an extreme cross wind at any reasonable forward speed. However, I do understand your reasons for this angle in this test.

[IMG][/IMG]

I can't see the video but the still image clearly shows flow separation.

I also noticed you did not extend the rope up through the windscreen. I wonder if that would help too. Some may think it would be too distracting. If that's the case, maybe a clear thin plastic fence on the windscreen would not be too objectionable.

Regards,
Teri

[Ironside]

Another windy day today, gusting at 38 mph. There was a gathering of vintage and classic motorbikes at a local beach, a perfect excuse for another run. This time I had a length of 10mm rubber tubing as my stall strip.

Despite these being the worse conditions so far, I was always in control, and apart from a couple of surprise gusts, was quite comfortable. It may be that I'm gaining confidence, but I would say that this is the best set-up so far.
Interestingly, even though the bike felt as though it was moving around, it was steening precisely.

Even though I'm happy with the result, further testing with a triangular and a straight 'fence' is planned, I will report on findings.

Teri, just for your information, us Welsh are fiercley proud of our heritage, and would prefer not to be called English (ask Catherine Zeta Jones, Anthony Hopkins or Tom Jones). We have our own flag, language and National anthem British - yes, English - definitely not.
Can't resist an opportunity to put Wales 'on the map'.

Thank's for all the help and encouragement, without you I would be waiting for calm weather before my next ride.

Regards,
Pete.

[Teri_TX]

Hi Ironside,

Originally Posted by Ironside

Teri, just for your information, us Welsh are fiercley proud of our heritage, and would prefer not to be called English (ask Catherine Zeta Jones, Anthony Hopkins or Tom Jones). We have our own flag, language and National anthem British - yes, English - definitely not.
Can't resist an opportunity to put Wales 'on the map'.

My apologies. Sorry about calling you an Englishman. I wasn't aware of the tension between the Welsh and the English. I was only making a joke about the nautical theme of using rope. Here, most folks just refer to themselves as Americans even though there are many different origins. Interesting that the Amish here in the US refer to ANY outsider as "English". I need to research the origin of that apparently derisive term, I suspect they (and other religious groups) were persecuted by the English before migrating here. I only know of the Cornwall region because of the "Doc Martin" series on BBC TV here.

Another windy day today, gusting at 38 mph. There was a gathering of vintage and classic motorbikes at a local beach, a perfect excuse for another run. This time I had a length of 10mm rubber tubing as my stall strip.

Despite these being the worse conditions so far, I was always in control, and apart from a couple of surprise gusts, was quite comfortable. It may be that I'm gaining confidence, but I would say that this is the best set-up so far.
Interestingly, even though the bike felt as though it was moving around, it was steening precisely.

Even though I'm happy with the result, further testing with a triangular and a straight 'fence' is planned, I will report on findings.

Interesting that the bigger tubing was apparently more effective. I had suspected that a larger stall strip would be more effective although there are probably diminishing returns. My best guess is that a fence would be most effective for any given height or protrusion but as I had said it would almost always cause turbulence and thus some drag. I do believe a triangular shape is best for a given height and can be designed for a given apparent cross wind angle. What angle you should design for is a function of what conditions you experience and feel comfortable with.

Thank's for all the help and encouragement, without you I would be waiting for calm weather before my next ride.

Regards,
Pete.

No, THANK YOU for testing and demonstrating the effectiveness of a stall strip like device. Your first hand observations and pictures of the tuft test experiment are the only known evidence of a possible solution to making streamlined single track vehicles safe in cross wind conditions. I only posited a theory based on a problem and some research.

Not that I'm much of racing fan anymore, but IF the FIM could be convinced ...

Regards,
Teri

[user removed]

Just a thought and advice from Pop who is almost 93 and flew a B17 in WW2. Flying in close formation for mutual protection, turbulence would make the planes bounce around quite a bit. Some pilots would fight it with control imput changes to try to avoid the bouncing in all 3 axes. Pop found out that if you just let the plane bounce around a little and kept your control imputs very small you would be fine as every plane in the formation was flying through the same turbulence. It also meant when you got back to base you had as much as 100 gallons more fuel than any one else in your group. He once flew a gal from Alabama to Virginia in an AT6 Texan. When they landed she asked him how the controls worked on the plane (trainer with dual controls). When he showed her she told him she had watched and never saw the stick move.

Moral to the story is when riding in strong crosswinds, make corrections to maintain your position, but don't try to keep a perfect line or you are fighting a loosing battle and wasting fuel. I've been hit by a 45 MPH gust on top of a bridge that really started to run me into the next lane, but I corrected enough to stay in my own lane. I still moved over probably 5 feet, but was in no danger.

Folowing this thread with interest if I run into problems with my tadpole.

Welshmen consider the English as target practice. No insult intended.

regards
Mech

[visionary]

A word of thanks

Hi Teri, I hope you will not mind if I use your thread to congratulate Ironside on his sterling efforts to quantify the side-wind stability effects of the stall strip. The two videos posted in his post #82 are the most detailed public domain research that I have seen.

Prior to this work, Craig Vetter’s tuft test photographs from an accompanying vehicle were about the best stuff out there. However, Ironside has trumped Craig for two reasons, firstly by choosing video footage which imparts far greater information than a single still image, and secondly because he has focussed on sidewind stability as a specific issue rather than the general drag reduction which was the point of Craig’s image.

So I think due recognition for this important step is warranted.

But, and I hate that there is a “but” , but the videos are of limited value as Ironside himself pointed out "To be honest, I can't see any discernible difference, but then again I don't know what I'm looking for."

I have taken some time to study the videos and have some experience of tuft testing myself, so here are my observations, which I hope will be seen as positive and helpful

Point 1 – Poor quality air – if you pause the first (no stall strip) video and look at the tufts in the first row (lets call it row A) at the centreline of the fairing, you will see that most tufts exhibit rapid direction change in a random sequence. Some side-by-side tufts have almost opposite flow direction, even nearest the centre where flow is greater. Compare this with tufts on an undisturbed area of a car body, which would appear almost motionless, and the problem is clear. What is needed is a “flow straightening device” to eradicate the turbulence created by the fans own blades. You could make such a device quite cheaply using the tube stacking method, but before you do see point 2 (below)



Point 2 – Insufficient air - Although the fan is not shown, my guess is that its only about 12” diameter ducted fan (single phase). From the video it can be observed that it produces a strong central flow and a weaker peripheral flow. This shows up as a divergent angle between the tufts at the extremities. A similar effect is produced by the rounded body profile but the tell-tale in this case is the energy level between the central and edge tufts. My guess, and it is a guess, is that you would need approximately ten times the mass airfow to cover the relative frontal area for this test


Ironside, please don’t give up, you are almost there. I would suggest real world riding rather than fan tests. I would keep the tufts on and take a ride with a couple of friends in a car alongside. One driver and one camera operator (simple handycam will do, phone footage will not work at suitable clearance distance) who can shoot you from slightly ahead and off to side, in windy and still conditions. Compare and contrast the footage with and without the strip(s) attached, and you will own this subject area.

An alternative method would be to fit a GoPro camera on a suitable mount and do it all yourself. You could also use a “flow visualisation grid” with this method, located at a critical point it will show more than just the boundary layer flow.

I hope you get to do more testing and I look forward to seeing the results. It would seem that your test rides have shown some promise but I hope you can find a scientific method for accurate measurement of results.
But heh, a genuine world leader!

[Teri_TX]

Hi Visionary,

Originally Posted by visionary

A word of thanks

Hi Teri, I hope you will not mind if I use your thread to congratulate Ironside on his sterling efforts to quantify the side-wind stability effects of the stall strip. The two videos posted in his post #82 are the most detailed public domain research that I have seen.

Prior to this work, Craig Vetter’s tuft test photographs from an accompanying vehicle were about the best stuff out there. However, Ironside has trumped Craig for two reasons, firstly by choosing video footage which imparts far greater information than a single still image, and secondly because he has focussed on sidewind stability as a specific issue rather than the general drag reduction which was the point of Craig’s image.

So I think due recognition for this important step is warranted.

Absolutely no objection from me on congratulations to Ironside. When I started this thread, I only expected an armchair discussion of what I perceived to be a cause of cross wind instability and a possible solution. I didn't think someone would step up and actually try out a stall strip so soon on a faired motorcycle. Ironside's tests are very encouraging.

Let us not forget Theo's report of "storm strips" on his velomobile. It showed great promise but the speed regime he operates in is less than a motorcycle's. One thing I've learned in my career is that one has to be very cautious about extrapolating data. Theo says Allert is planning to add "storm strips" on his streamlined motorcycle but that he rarely rides it now.

Much remains to done. Height and shape of the stall strips are just a couple of things that come to mind. Perhaps a second set of stall strips parallel to the center one ... Tests on a full streamlined motorcycle need to be performed. Vetter in a private email has told me "... this is consistant with my preliminary result". I await the official full report on his site.

I'm still holding my breath for a fully enclosed (no side gap) streamlined motorcycle. Allert's is the only one I'm presently aware of.

Ironside has "won a battle" to use a phrase, but there is still a war to be won. I congratulate Ironside for his battle victory in any event.

But, and I hate that there is a “but” , but the videos are of limited value as Ironside himself pointed out "To be honest, I can't see any discernible difference, but then again I don't know what I'm looking for."

I have taken some time to study the videos and have some experience of tuft testing myself, so here are my observations, which I hope will be seen as positive and helpful
<snip>
...

I wish I could see the videos but all attempts on Firefox, Internet Explorer and Google Chrome have failed. I have no idea of the cause. I'll have to just rely on your observations.

Ironside, please don’t give up, you are almost there. I would suggest real world riding rather than fan tests. I would keep the tufts on and take a ride with a couple of friends in a car alongside. One driver and one camera operator (simple handycam will do, phone footage will not work at suitable clearance distance) who can shoot you from slightly ahead and off to side, in windy and still conditions. Compare and contrast the footage with and without the strip(s) attached, and you will own this subject area.

Having a car filming beside Ironside may be tricky and/or dangerous in cross wind testing. The danger should be obvious, particularly if Ironside should get blown toward the car. Tricky because the filming vehicle needs to be distant enough to avoid altering Ironside's local air flow. Vetter didn't have this problem since he was not interested in cross wind effects on the tufts. Also, no slight toward Ironside, Vetter is an experienced accomplished motorcycle rider. Just be careful.

An alternative method would be to fit a GoPro camera on a suitable mount and do it all yourself. You could also use a “flow visualisation grid” with this method, located at a critical point it will show more than just the boundary layer flow.

I hope you get to do more testing and I look forward to seeing the results. It would seem that your test rides have shown some promise but I hope you can find a scientific method for accurate measurement of results.
But heh, a genuine world leader!

The GoPro camera seems to be a lot safer but does require fabricating a suitable mounting bracket sticking out several feet. The authorities may take a dim view of such a bracket. Hope Pete [Ironside] can borrow a GoPro if he doesn't have one already.

-- Teri