Introduction & Cross wind solutions to motorcycle Streamliners?

[freebeard]

[citation needed]

Do you have a link or search term to document that?

[godscountry]

Allert Jacobs claims stability in crosswinds up to 40 mph,is that a misprint and if not,whats going on here.I have read he has improved his mileage from around 130 to a best 221 with the addition of a manual clutch,sprocket change and a 88 lb body and hardware.If true,what makes his relatively short wheelbase partial streamliner so stable and could some of these designs be tested in a computer program? Could you test crosswind stability in a software program?

[Frank Lee]

Allert did and then... he didn't. Rather, his friend said it wasn't so good in x-winds. So who knows.

[aerohead]

Originally Posted by godscountry

Allert Jacobs claims stability in crosswinds up to 40 mph,is that a misprint and if not,whats going on here.I have read he has improved his mileage from around 130 to a best 221 with the addition of a manual clutch,sprocket change and a 88 lb body and hardware.If true,what makes his relatively short wheelbase partial streamliner so stable and could some of these designs be tested in a computer program? Could you test crosswind stability in a software program?

In bluff-body,3D,automotive work,CFD is okay for pick-and-shovel work,but the automakers always do a full-scale mockup for actual tunnel testing and aero tuning.
They can do an actual velocity/pressure profiles,locate the center-of-pressure at varying degrees of yaw,as well as lift/drag/pitch,and roll moments.
Smoke can reveal trouble spots.
Cal Tech's GALCIT tunnel has been used by racing teams to evaluate fully-enclosed Bonneville streamliner motorcycles.
One might underwrite some graduate studies in the tunnel to test out a design roughed in with CFD.A phone call or email would get you pricing info for tunnel time.

[Grant-53]

I recently priced two wind tunnels on the East Coast (NC and NH) for bicycle testing. Both charge $500/hr.
The NASCAR flaps are for stabilizing a spinning car.

[Cycle]

Having the daily opportunity to be in close vicinity to large passenger aircraft, I've started looking at how the aircraft designers do their aerodynamics... one thing I noticed is the nose cone 'stall strips':



And the underside aerodynamic treatment, which moves the separation point further rearward:


Note the slight widening of the underbelly, then it transitions into a narrower area that widens (at the blue strip) then narrows rearward. I'd taper that 'narrower area' upward to force the air underneath the body to exit more cleanly into the wake.

Now imagine a motorcycle with the same sort of underbelly. Take the wings and rear stabilizers off, put the rear wheel where the blue band extends across the rear of the underbelly, protruding just enough that if you get a flat, the body won't scrape. The front wheel would go just forward of the "U" or "V" shape in the underbelly, with a shortened nose.

Unfortunately, I have absolutely zero artistic ability... so using a CAD program or similar to mock something up is completely out... I might be able to mock up something rough using modeling clay, at least with that I can see in real-time and in 3-D what the shape is and change it as desired... those graphics programs always end up giving me some misshapen grotesquery that in no way looks like what I want it to look like... and the more I try to fix it, the worse it gets.

<sigh> This abortion is about the limits of my artistic abilities:

[Cycle]

Originally Posted by Ironside

Just a quick update on the 'storm strip' installed on the recumbent Honda.
I've recently returned from a trip to France for the D-day anniversary, we covered over a thousand miles, and I can report that the stability of the little Honda is acceptable.
It does squirm around when slipstreaming trucks, until a 'sweet spot' is found, but is no worse than a bike equipped with a conventional fairing, although the guys following said it looked a little scary.
At one point we were crossing a high bridge, the guy in front of me was riding a faired Honda 200 Benly and he said later that he had trouble keeping it within his lane, I had no real issues.
Ironside.

I just recently threaded the needle across the San Francisco Bay Bridge in high (~50 MPH) and gusty cross-wind conditions... that takes every bit of concentration you've got to keep from smacking into cars. You have to sort of anticipate what the wind will be like as you move from open areas (no vehicles) to areas between vehicles (especially as you move ahead of a large truck upwind, with a small car just ahead and downwind). I did it so I could get a feel for how the wind "feels" in those situations... the more you learn, the more you know, and all that.

[freebeard]

https://en.wikipedia.org/wiki/Messerschmitt_Me_262#Specifications_.28Messerschmi tt_Me_262_A-1a.29

IMHO the widened lower section is to accommodate the landing gear. But I agree a flat bottom is preferable to a rounded lower profile. The shark-like triangular profile of the ME-262 is like that all over, and it was referenced in the Aeromodeller2 project as improving the ground handling of an airship.


http://www.aeromodeller2.be/

[Cycle]

Originally Posted by freebeard

https://en.wikipedia.org/wiki/Messerschmitt_Me_262#Specifications_.28Messerschmi tt_Me_262_A-1a.29

IMHO the widened lower section is to accommodate the landing gear.

Not entirely, no.

I remember reading something about it in doing research... at the subsonic speeds that the passenger airliners travel at, the belly fairings help to keep the air from separating from the body at the wing-to-body intersection, thus improving fuel efficiency.

In the A380, they're over 100 feet long! Most of it is empty space, with the thru-wing supports, some hydraulics and fuel transfer equipment in there. I haven't had the opportunity to climb up inside an A380, although I walk under them all the time at work, so I get a pretty up-close look at how the designers worked to lessen aerodynamic drag. The 20 wheels of the A380's rear wheels tuck up into a small portion of the belly fairing just ahead of and just behind the rear of the wing.

The A380's not a very good example, though... practically the entire underside of the plane is belly fairing... almost like a flying wing.

The 787 has much more pronounced belly fairings at the wing bases.

[sendler]

I think you are making way too much of the bulging shapes of the under belly to try to project that up into the entire streamline of a motorcycle fairing. The top of the airplane fuselage where the majority of the area is located doesn't look anything like that.