World's lowest drag vehicle

[Blue]

Just had an interesting read in ESPN magazine on human powered vehicles.  The land class record holders are, of course, recumbent bicycles with ridiculously low drag.  I was a little stunned at how far they have come since I last saw some of these in 1990. 

The current record is 81 MPH!  (200m trap, running start).

The current 1 hour record is 53.5 MPH.

Taking it from where I remember this, a fit human racer can sprint at about 2 HP and sustain about 1 for any length of time.  The numbers above work perfectly for .9 HP=53.5 MPH and 2.1 HP for 81 MPH. 

Anyone for 200 MPH on 13 HP?!!!!!!!!!

The current record holder is a small guy riding a vehicle where they clearly traded off some wetted area for his small size.  This reduced the total surface area.  They seem to be running about 70% laminar flow on the vehicle sides and have stuck the canopy at the far back to reduce wetted area vs. having a longer laminar run like their nearest competitor.

The obvious advantages of these designs vs. common LSR are IN ORDER:

1. Absolute minimum separation: No blunt rear ends, minimal wheel openings, fairings in front and behind the tires.
2. Ground clearance:  "ground effects" may sound sexy, but they are high drag.  If we need downforce, we should use a low drag wing, high up in clean air like Teague did.
3. Absolute minimum wetted area:  They are SHORT!  Shorter means more aggressive pressure recovery, the first trade-off.
4.  Significant percentage of laminar flow:  Up to 60% of the record holder's wetted area is in laminar flow with favorable pressure gradients and no joints, hatches, vents, or other BS to trip the layer to turbulent.

Sites to check out are:

www.ihpva.org

and pictures of the best of the best:

http://www.speedbikebgl.de/eng/sbc2004e.html

And the open motorcycle guys could use some of these tail section ideas:

http://www.speedbikebgl.de/eng/galeriee.htm

A lurker on this site who's a race HPV builder contacted me on the side, I think there's still some speed to be had in these things... 

[sockjohn]

81 mph with nothing but spandex shorts, a foam bike helmet, and a few layers of carbon fiber shell to protect you?  NO THANKS!   

Not to mention bike tires with what speed rating?

But it does make you think. 

[Ratliff]

Dick Keller, a co-designer of The Blue Flame, is closely involved these days with human powered vehicles.

[Ratliff]

Just had an interesting read in ESPN magazine on human powered vehicles.  The land class record holders are, of course, recumbent bicycles with ridiculously low drag.  I was a little stunned at how far they have come since I last saw some of these in 1990. 

The current record is 81 MPH!  (200m trap, running start).

The current 1 hour record is 53.5 MPH.

Taking it from where I remember this, a fit human racer can sprint at about 2 HP and sustain about 1 for any length of time.  The numbers above work perfectly for .9 HP=53.5 MPH and 2.1 HP for 81 MPH. 

Anyone for 200 MPH on 13 HP?!!!!!!!!!

The current record holder is a small guy riding a vehicle where they clearly traded off some wetted area for his small size.  This reduced the total surface area.  They seem to be running about 70% laminar flow on the vehicle sides and have stuck the canopy at the far back to reduce wetted area vs. having a longer laminar run like their nearest competitor.

The obvious advantages of these designs vs. common LSR are IN ORDER:

1. Absolute minimum separation: No blunt rear ends, minimal wheel openings, fairings in front and behind the tires.
2. Ground clearance:  "ground effects" may sound sexy, but they are high drag.  If we need downforce, we should use a low drag wing, high up in clean air like Teague did.
3. Absolute minimum wetted area:  They are SHORT!  Shorter means more aggressive pressure recovery, the first trade-off.
4.  Significant percentage of laminar flow:  Up to 60% of the record holder's wetted area is in laminar flow with favorable pressure gradients and no joints, hatches, vents, or other BS to trip the layer to turbulent.

Sites to check out are:

www.ihpva.org

and pictures of the best of the best:

http://www.speedbikebgl.de/eng/sbc2004e.html

And the open motorcycle guys could use some of these tail section ideas:

http://www.speedbikebgl.de/eng/galeriee.htm

A lurker on this site who's a race HPV builder contacted me on the side, I think there's still some speed to be had in these things... 

Combine a powerplant like the one in this bike...

http://www.landracing.com/forum/index.php/topic,4010.0.html

...with those shapes and the results could get real interesting real quick.

[Blue]

...But it does make you think. 

Ahhhh, that is the idea.

Yeah, they are a little shy on safety features that we would be comfortable with (not to mention compliance with the rules).  OTOH, the numbers are so much better than what we expect in LSR that it's worth taking a closer look at it.

Let's say we doubled the size of the current HPV record holder to put real tires on it (note that the design allows for decent diameter wheels!), a real person in a fire suit (I'm not fat, that's insulation!), roll cage, real helmet, ice vest, breathing bottle, and an actual engine.  If we did all of this without adding drag beyond the size change ( bear with me here...) we'd need 24 HP for 200 MPH and 74 HP to match BUB-7's current speed.  100 HP would break through the 400 MPH barrier.

WOW.

I'll design it, I've even got shop space; anyone want to build it?

[jdincau]

Hard to keep that laminar flow percentage as the speed increases.
Jim

[interested bystander]

Fascinating subject - wonder if Mr Reynolds and his number enters into projecting the bike's performance into 440plus mph?

Remarkably, the record holding Varna bicycle bears a more than passing resemblance to the eforts by NSU with motorcycles in the '50s.

 Taking things a step farther, does this skateboard racer attached ready to race DOWN Shell Hill @ Signal Hill (Long Beach, Ca)  in '78resemble Jack costella's latest two wheel efforts?

Nothing new under the sun!

[John Noonan]

...But it does make you think. 

Ahhhh, that is the idea.

Yeah, they are a little shy on safety features that we would be comfortable with (not to mention compliance with the rules).  OTOH, the numbers are so much better than what we expect in LSR that it's worth taking a closer look at it.

Let's say we doubled the size of the current HPV record holder to put real tires on it (note that the design allows for decent diameter wheels!), a real person in a fire suit (I'm not fat, that's insulation!), roll cage, real helmet, ice vest, breathing bottle, and an actual engine.  If we did all of this without adding drag beyond the size change ( bear with me here...) we'd need 24 HP for 200 MPH and 74 HP to match BUB-7's current speed.  100 HP would break through the 400 MPH barrier.

WOW.

I'll design it, I've even got shop space; anyone want to build it?

I would ride it... even if it only ran 400 mph..

[Rex Schimmer]

Blue,
I would like your opinion on doing a flat bottom lakester that is a NACA 66012 section in plan view with a flat bottom that runs about 1 inch off the ground and the top of the car would also be the 66012 shape in side view. I would not try to produce down force with the flat bottom, i.e. no rake and no diffuser, flat,straight and parallel to the ground plane and with pretty small area. I am think that using a 22 inch width the body would be around 180 inches long. Is this to much wetted area?

Thanks in advance for your comments.

Rex

[Blue]

Blue,
I would like your opinion on doing a flat bottom lakester that is a NACA 66012 section in plan view with a flat bottom that runs about 1 inch off the ground and the top of the car would also be the 66012 shape in side view. I would not try to produce down force with the flat bottom, i.e. no rake and no diffuser, flat,straight and parallel to the ground plane and with pretty small area. I am think that using a 22 inch width the body would be around 180 inches long. Is this to much wetted area?

Thanks in advance for your comments.

Rex

Jim and IB: Cd(wet) decreases with increasing Rn faster than laminar run decreases.  Yes, the laminar to turbulent transition moves forward with Rn, but any decent favorable gradient can keep the layer laminar up to millions of Rn.  Beyond that, the Cd(wet) is so low it doesn't matter.

Rex: The flat bottom is the single worst feature after the LSR-typical blunt tail.  Far better would be to get rid of the corners (vortex generators) and round the lower surface up to meet the sides.  Get the whole thing up off the ground and fair the wheels.  A flat bottom will always be 100% turbulent and leads to a difficult aft closure with a greater potential for separation.

The 66012 is a good section for laminar run, the 60's torpedo data shows that we can be even more aggressive with bodies of revolution (like a lakester).  Remember, the 66xxx series were designed as wing sections.  Bodies of revolution can achieve much more aggressive fineness ratios and closure for the same degree of pressure recovery.

[hawkwind]

And the open motorcycle guys could use some of these tail section ideas:

http://www.speedbikebgl.de/eng/galeriee.htm


[/quote]

sadly the partial streamlining rules preclude the use of most if not all those tail sections , any further  benificial streamlining  is frowned upon for our own personal safety in the event of an unexpected sidewind,which may or may not  upset the apple cart  , brute horsepower has flirted for to long with marginal traction and is on a loosing bet , fiddling around the edges with frontal area is all thats left ,unless the rules regarding partial streamlining change ,sad but true 

[Stainless1]

Rex: The flat bottom is the single worst feature after the LSR-typical blunt tail.  Far better would be to get rid of the corners (vortex generators) and round the lower surface up to meet the sides.  Get the whole thing up off the ground and fair the wheels.  A flat bottom will always be 100% turbulent and leads to a difficult aft closure with a greater potential for separation.

The 66012 is a good section for laminar run, the 60's torpedo data shows that we can be even more aggressive with bodies of revolution (like a lakester).  Remember, the 66xxx series were designed as wing sections.  Bodies of revolution can achieve much more aggressive fineness ratios and closure for the same degree of pressure recovery.

Blue, when you fair the wheels, you are no longer a lakester...
Don't lakester bodies need to be designed with the rotating open wheels considered?  And will the placement of those wheels effect the outcome?
And sorry, I like flat bottommed lakesters... 

[Ratliff]

Rex: The flat bottom is the single worst feature after the LSR-typical blunt tail.  Far better would be to get rid of the corners (vortex generators) and round the lower surface up to meet the sides.  Get the whole thing up off the ground and fair the wheels.  A flat bottom will always be 100% turbulent and leads to a difficult aft closure with a greater potential for separation.

The 66012 is a good section for laminar run, the 60's torpedo data shows that we can be even more aggressive with bodies of revolution (like a lakester).  Remember, the 66xxx series were designed as wing sections.  Bodies of revolution can achieve much more aggressive fineness ratios and closure for the same degree of pressure recovery.

Blue, when you fair the wheels, you are no longer a lakester...
Don't lakester bodies need to be designed with the rotating open wheels considered?  And will the placement of those wheels effect the outcome?
And sorry, I like flat bottommed lakesters... 

I suppose wind tunnel tests or side by side runs with otherwise identical cars would be required (or maybe the same car with different rear axles), but I have often wondered about the differences in aerodynamic effects of the wheels being at a distance from the body as opposed to being flush against the body. According to a paper published by Dr. T.P. Torda (chief aerodynamicist on The Blue Flame), The Blue Flame despite its struts and open rear wheels had only about a .22 subsonic drag coefficient.

The 1921 Tropfenwagen (see link below), despite its ungainly appearance, when wind tunnel tested by Volkswagen a few years ago had only a .28 drag coefficient!

http://en.wikipedia.org/wiki/Rumpler

[maguromic]

Blue, Just curious why then does all of Jack Costella's cars with their flat bottoms are so fast?  Is it because of the top shape? Or?

[Rex Schimmer]

OK Blue time for some definition of terms. Fines ratio: If I make my body as a body of revolution as you said does "being more agressive with the "fines ratio" mean that I can shorten the length and still have good attachment and low aero drag? As I said the plan is for a lakester so I will have expose wheels but my plan is to have them at least 20 inches away from the car and all of the axles and connections covered by wing section shape fairings. I also plan to have both the inside and outside wheel coverings on the front wheels be non rotating and on the rear the inside wheel cover would not rotate. Is this worth the effort?

I have attached, I think, a picture of the Nissan gravity racer which does have faired wheels but I would of course not have the wheel fairings, but is this what you are describing?

Blue, I really appericate all of your input, and you will find on this site we are all greatful for any kind of aero info from an expert. Trouble is that we will use you like a "rented mule" to keep getting your ideas!!

Rex