" Aerodynamics doesn't begin to have an effect until 60 MPH "

[aerohead]

Originally Posted by Autobahnschleicher

When I was a lot into road cycling, my topspeed used to be about 60 km/h.
That was in an all out sprint, I do not have a power meter but the Kreuzotter calculator says 1249 W of power are required for that on my roadbike in my sprinting position.
If I went with my most agressive TT position (Superman), I'd need only 570W for the same speed.
With a fully faired recumbent I'd be at a sustainable 180W.

Aerodynamics matter a lot even at that kind of speed.
And I love to show it to road cyclists by passing them on my rather comfortable and aerodynamic recumbent.

Somewhere, maybe some book on human factors, they mentioned that top athletes can momentarily generate around 2- horsepower ( 1,491- Watts ), so your numbers certainly reflect the real world!

[Autobahnschleicher]

Originally Posted by aerohead

Somewhere, maybe some book on human factors, they mentioned that top athletes can momentarily generate around 2- horsepower ( 1,491- Watts ), so your numbers certainly reflect the real world!

Given my build and exact position I suppose the calculator estimate is a little on the high end.
And also given my height and gender I probably will never reach pro athlete levels.
But to be fair, olympic track sprinters can reach a lot more than 1500W in an all out sprint.
They often reach in excess of 2000W

[ALS]

Aerodynamics matter at all speeds. Be it 10-20-30 and so on. Ask any soap box derby racer if aerodynamics matter during his or her coasting race? BTW with just gravity they can hit speeds up to 21 mph on a 950 ft track.

The best fuel mileage will always be attained by running in the highest gear at the lowest possible engine speed RPM's with out lugging the engine.

Most vehicles have a sweet spot for fuel mileage between 40 and 45 mph. That is the point where in most cases wind resistance becomes a factor with the power needed to over come it starts to accelerate quickly as your speeds increase.

Here is a white paper from Cummings Diesel that goes over speed and aerodynamics vs fuel mileage. Yes it involves big rig trucks and trailers but the principles they talk about still apply across all classes of road vehicles. BTW it is a PDF when you get to the page.

Cummins_Secrets_of_Better_Fuel_Economy.pdf

[racprops]

Oh well and good, but it seems to me Aerodynamics does not really matter all that much unless your drive a tiny car with a TINY motor and trying for as much MPG as possible,

I drive a 93 Star Craft full sized G20 Van.

Forever I keep hearing IT IS A BOX, your never get good MPG out of a box.

YET Chevy in 2019 made a full sized Express Van, long wheel base 3500 155" with a 4.30V6 Direct injected, 8 speed:

AND it is officially on the window sticker listed as its MPG of 19 City and 29 Highway.

It is a brick sitting high on its wheels and get 29 highway.

There is no real Aerodynamics on it.

Rich

[Autobahnschleicher]

Originally Posted by racprops

Oh well and good, but it seems to me Aerodynamics does not really matter all that much unless your drive a tiny car with a TINY motor and trying for as much MPG as possible,

I drive a 93 Star Craft full sized G20 Van.

Forever I keep hearing IT IS A BOX, your never get good MPG out of a box.

YET Chevy in 2019 made a full sized Express Van, long wheel base 3500 155" with a 4.30V6 Direct injected, 8 speed:

AND it is officially on the window sticker listed as its MPG of 19 City and 29 Highway.

It is a brick sitting high on its wheels and get 29 highway.

There is no real Aerodynamics on it.

Rich

That's pretty bad fuel efficiency compared to let's say a Mercedes Sprinter, long and tall version.
You can drive them with 6-7L/100 km when going slow because of the rather efficient engine and super tall gearing.
However these high cda's realy bite you at speed, when I set cruise to 160 km/h I usualy see ~18L/100km

[Isaac Zachary]

Originally Posted by racprops

Oh well and good, but it seems to me Aerodynamics does not really matter all that much unless your drive a tiny car with a TINY motor and trying for as much MPG as possible,

I drive a 93 Star Craft full sized G20 Van.

Forever I keep hearing IT IS A BOX, your never get good MPG out of a box.

YET Chevy in 2019 made a full sized Express Van, long wheel base 3500 155" with a 4.30V6 Direct injected, 8 speed:

AND it is officially on the window sticker listed as its MPG of 19 City and 29 Highway.

It is a brick sitting high on its wheels and get 29 highway.

There is no real Aerodynamics on it.

Rich

Vans are/can be, aerodynamic in their own sort of way.

As a vehicle increases in size, it's volume increases faster than it's external area. Because of that you can haul more stuff or people with less aerodynamic drag per person or quantity of cargo.

Bigger vehicles also end up becoming longer in proportion to their height and width. That is also an aerodynamic improvement. For an example, trains are very aerodynamic because of their length.

Not that curves can't help. But a curvy vehicle body isn't everything.

[racprops]

Originally Posted by Autobahnschleicher

That's pretty bad fuel efficiency compared to let's say a Mercedes Sprinter, long and tall version.
You can drive them with 6-7L/100 km when going slow because of the rather efficient engine and super tall gearing.
However these high cda's realy bite you at speed, when I set cruise to 160 km/h I usualy see ~18L/100km

Can you translate that to Miles and MPH and MPG??


Please.

Rich

[racprops]

Originally Posted by Isaac Zachary

Vans are/can be, aerodynamic in their own sort of way.

As a vehicle increases in size, it's volume increases faster than it's external area. Because of that you can haul more stuff or people with less aerodynamic drag per person or quantity of cargo.

Bigger vehicles also end up becoming longer in proportion to their height and width. That is also an aerodynamic improvement. For an example, trains are very aerodynamic because of their length.

Not that curves can't help. But a curvy vehicle body isn't everything.

That is another reason I believe my 93 will do well:

[freebeard]

6-7/~18 ≤ 3

Hope this helps.

My Type IIs had better Cd than any of my Beetles, just more A.

[classicalgas]

That's been proven to be very wrong over the last decade or so...down force and drag can be produced and changed in very obvious quantities well below 60 mph.

My current project is an electric bike with only 750 watts of power, it's getting a vintage moped race fairing, and both top speed and watt consumption will be compared before and after fitting the fairing.