World's lowest drag vehicle

[RichFox]

On the Salt Snake and the 5050 bike they are so close to the ground and a single track vechile I don't see how the bottom can't be scraping at any time any correction is being made. Lean the bike it scrapes. Seems to work anyway.

[Ratliff]

Discussions of vortices and use of vortex generators to reduce drag/increase lift

http://www.mulsannescorner.com/vortexlift.html

http://www.b737.org.uk/fuselage.htm#AFT_BODY_VORTEX_GENERATORS

http://www.aerospaceweb.org/question/aerodynamics/q0255.shtml

http://www.aerospaceweb.org/question/planes/q0176.shtml

[Blue]

I want to apologize to the bike racers who have reminded me to read the rules on tail sections.  I had no idea they were so restrictive on the tail and allow so much up front.  This is bad from a stability side:  front fairings move the aerodynamic center forward and cause the bike to be more susceptible to crosswinds than a longer tail.  Tails help point the vehicle into the wind and counteract the side force blowing the bike off course.

There is discussion among some aero people about "too much tail" causing the vehicle to steer into the wind in excess of the side load.  The top people in LSR that I have asked haven't seen that, if fact, just the opposite.  The longer tailed streamliners seem to have a better time in a given crosswind than short tailed ones.

Pork Pie: "Blunt" refers to the chopped off rear ends that we see at the back of parachute tubes and the back of most cars.  Getting rid of that on a streamliner means doing movable cover doors like BUB or Burkland.

Rex: Yes, that's getting close; for a lakester, just take the wheel fairings off.  As for airfoil sections, a body of revolution up in clean air can have a fineness ratio (length over max diameter) of as little as 3 or 4.  Beyond 7 is a lot of drag, but could still be a good "liner" if there's minimal separation.  A fineness ratio of 4 would mean a 66-025, a 66-020 = 5, and so on.

[Ratliff]

I want to apologize to the bike racers who have reminded me to read the rules on tail sections.  I had no idea they were so restrictive on the tail and allow so much up front.  This is bad from a stability side:  front fairings move the aerodynamic center forward and cause the bike to be more susceptible to crosswinds than a longer tail.  Tails help point the vehicle into the wind and counteract the side force blowing the bike off course.

There is discussion among some aero people about "too much tail" causing the vehicle to steer into the wind in excess of the side load.  The top people in LSR that I have asked haven't seen that, if fact, just the opposite.  The longer tailed streamliners seem to have a better time in a given crosswind than short tailed ones.

Pork Pie: "Blunt" refers to the chopped off rear ends that we see at the back of parachute tubes and the back of most cars.  Getting rid of that on a streamliner means doing movable cover doors like BUB or Burkland.

Rex: Yes, that's getting close; for a lakester, just take the wheel fairings off.  As for airfoil sections, a body of revolution up in clean air can have a fineness ratio (length over max diameter) of as little as 3 or 4.  Beyond 7 is a lot of drag, but could still be a good "liner" if there's minimal separation.  A fineness ratio of 4 would mean a 66-025, a 66-020 = 5, and so on.

A fineness ratio of 3 is about what Bob Rufi had on his body of revolution liner back in 1939.

[tortoise]

On the Salt Snake and the 5050 bike they are so close to the ground and a single track vechile I don't see how the bottom can't be scraping at any time any correction is being made. Lean the bike it scrapes. Seems to work anyway.

I spoke to 5050's driver on the salt last year and he described a run where scraping in a sidewind slowed the bike 30mph.

Porkpie has described how when Costella's bikes are steered the front wheel displaces sideways to the right when the bike is steered left (and vice versa), providing a sort of "virtual lean". 

[tortoise]

There is discussion among some aero people about "too much tail" causing the vehicle to steer into the wind in excess of the side load.  The top people in LSR that I have asked haven't seen that, if fact, just the opposite.  The longer tailed streamliners seem to have a better time in a given crosswind than short tailed ones.

I read a paper somewhere recently, focussed on sit-on bikes, purporting to demonstrate that the center of pressure on a bike needs to be a bit ahead of the center of gravity for safe handling. With the center of pressure behind, a wind from the left leans the bike to the right and steers it to the left; not the best situation, seems to me. Perhaps this is the source of the problems which led to banning extended tails on sit-on bikes.

[willieworld]

the person that wrote that article has never ridden a motorcycle in the wind before  willie buchta

[bak189]

O.K.......O.K.  all these numbers  impress
me..........but I like to believe in FACTS..................
the Can-AM wind-tunnel tests back in the early 1970's showed that a tail (not unlike the ones shown on the push-bikes) made a very big improvement in the Aero of the 125c.c. bike
tested...................but the FACT is that the bike
could not be riden safely above approx. 80mph.
.................with a very lite cross-wind..........FACTS
..............not theory on paper or wind-tunnel......
FACTS...............................FACT....a Dustbin fairing
makes for better Aero........return record run
of our sidecar at last years BUB.........approx. 5 to 8 mph cross-wind (in addition to bad traction)
the outfit got completely sideways in the speed- trap....only the sidecar driving skill of Larry Coleman saved the day.......FACTS............................

[tortoise]

the person that wrote that article has never ridden a motorcycle in the wind before  willie buchta

I bow to your practical knowledge, but do you know where the center of pressure is on the bikes you've ridden?

[Ratliff]

http://www.youtube.com/watch?v=gg6UOLiHD3o

http://www.competitionplus.com/02_18_2004/photos/wsid_04.jpg

Jay Upton, 230 mph fully enclosed sit on Top Fuel bike.

[willieworld]

never bow to anything --i know of what i speak from practial experience because im a long distance motorcycle rider ive ridden in every kind of weather --if i were to guess i would say ive ridden well over 500,000 miles my best year was when i was 61 i rode 41,620  and i dont comute to work my shop is 25 feet from my house --i can tell you this if you are traveling east and the wind is blowing south the wind will move you to the south --if you want to keep going south you will have to lean your bike over to the left --im talking about a street bike --the bike i race is a sidecar bike 2 wheel rules dont apply its like driveing a car with 3 wheels  just some thoughts  willie buchta

[hawkwind]

partial streamlined aerodynamics and rules ,its like a wheel it goes round and round , from the ban bikes or at least wrap them in cotton wool ,to the allow anything and be danmed with the consequenses ,to every thing in between ,its one of those we all agree to disagree subjects ,by the way Im in the anything and be damned camp 
cheers

[joea]

facts......the canam ordeal was ONE incidence......

NOT a real impressive study to base others on.....
impressive effort, but one teams results.......with one bike
and no systematic rework.....

now i know there have been other applications with
tails that seem to cause issues ie one of the HD bikes
many moons ago.....

BUT.....i for one am not going to make the ASSumption
that because team A had a handling issue with x tail that
tails are bad...for example....for my bike with cg horizontal of B, and cg vertical
of C, and center of pressure D......etc

its the total system that i would be much more interested in studying....

because sidecar E going 160-180 with a dustbin doesnt imply that sidecar
F that already goes 210+ without dustbin, will fail miserably with appropriately
applied aero resembling a quote dustbin fairing.......

it troubles me to see blanket comments......without due system analysis.....

it was OUTLAWED for decades to have a front fairing that had the nose beyond a vertical
line through the front axle...........THEN production bikes did this with higher stock speeds
than many bonneville records..........

additionally we were OUTLAWED to have tailsections extend beyond rear edge of rear wheel....
THEN stock bikes began coming out with tail sections beyond this illegal point....with fine
success, speeds and stability.......

THEN the scta rules makers MANDATED that any tail beyond rear wheel must be above
the top of rear tire....thereby requiring that extra surface area be high on the rear of the bike....

no we have bikes with MONSTER hp, hanging significant wt off swingarms trying to increase speeds.....

whats worse, incrementally refining a design to higher speeds, or having blanket beliefs relegate rules
to the point of potentially riskier practices

[hawkwind]

bravo ,well said Joe 

[willieworld]

well its 5:51 friday morning and im leaving for el mirage in about 15 minutes and i was just wondering of all the members- guests-lurkers and experts how many i will see there going down the lake WFO hopefully everyone    willie buchta

its going as fast as you can go --its not rocket science