Wikispeed

[freebeard]

Goggling Google's results for "dune buggy curb weight" it looks like 1000-1400lb, although I remember claims as low as 800lb. Consider the differing requirements for a drag racer (minimal) and off-road racer (maximal).

They appear to use a large thin-wall aluminum box tube in an un-triangulated structure, If I read their pictures right. You couldn't just leave the top tube off to make way for a door, the thing would collapse.

But they have an interesting design management process, scrum. Maybe that would allow them to accommodate the changes that would reverberate through the rest of the car if doors were added.

[aerohead]

I did some back of the napkin cyphering and came up with some numbers to consider.
*MOTOR TREND reported in January 1993 that they had run a Honda VX from Los Angeles,Calif. to San Francisco and back, and claimed 64.6 mpg.
*From Hiroyuki Ozawa et al. Japanese Society of Automotive Engineers Paper JSAE 9835285 for the 1996 Honda Dream Solar race car,their Road Horsepower graph would put a VX-like car at 10.7kW (14.348 hp) road load @ 55 mph.
*At 92% mechanical efficiency for the driveline,the shaft power would be 15.596 bhp.
*At 64.6 mpg and 55 mph,the VX would use 0.8513 gallons of gas/hour.
*0.8513 gallons is approximately 5.108 pounds/hour.
*At 5.108 lbs/ 15.596 bhp = 0.3275 BSFC.
*This establishes a BSFC for a very efficient HONDA engine.
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*If the WIKISPEED car gets 114 mpg @ 67 mph,then it uses 0.5877 gallons/hour
*Or, 3.5263 lb/hour..
*At 0.3275 BSFC the Road Load Brake Horsepower would be 10.767 bhp.
*Again,at 92% mechanical efficiency,the Road Horsepower at 67 mph is 9.905 horsepower.
*From Ozawa's curve,and a 'test weight' of 1,400-lbs,the power absorbed by Rolling Resistance at 67 mph would be 4.11 hprsepower.
*Subtracting the R-R from the total Road Load yields 5.795 aero horsepower load at 67 mph.
*Using the aerodynamic horsepower formula,using standard air density,at 67 mph,the WIKISPEED drag factor would have to be 0.262 m-sq (2.822 sq-ft) to balance the energy equation.
*If we use the frontal area of the smallest convertible ever sold,the 1966 Lotus Elan,at approx. 1.304 m-sq (14.038 sq-ft) and solve for the drag coefficient,we get Cd 0.201 to balance the equation.
*The Mazda MX-5 Miata,at Cd 0.38 is at the lower end of the drag spectrum for convertibles.
*I have no idea how the WIKI team could achieve something around Cd 0.201.
If their car is any larger than the Lotus,the Cd will need to be smaller to maintain the CdA.
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It would be polite for the WIKI team to provide more definitive data for their car.

[Otto]

Originally Posted by freebeard

Goggling Google's results for "dune buggy curb weight" it looks like 1000-1400lb, although I remember claims as low as 800lb. Consider the differing requirements for a drag racer (minimal) and off-road racer (maximal).

They appear to use a large thin-wall aluminum box tube in an un-triangulated structure, If I read their pictures right. You couldn't just leave the top tube off to make way for a door, the thing would collapse.

But they have an interesting design management process, scrum. Maybe that would allow them to accommodate the changes that would reverberate through the rest of the car if doors were added.

Seems like they could eliminate the upper square tubes, and replace them with two arches running diagonally from the strut towers, an intersecting X above the cockpit to form a roof/rollover structure. That way, they'd get both torsional bracing and rollover protection, and could have doors to actually get in and out of the car. Gussets at all intersections a good idea, too. Need to beef up the wimpy upper shock/spring mounts, which will last about 3 blocks without such improvements. I have serious doubts about their aero efficiency, as that LeMans shape is more about downforce than efficient streamlining.

[oil pan 4]

These numbers remind me of the early "chevy volt" hype.

[freebeard]

Originally Posted by otto

Seems like they could eliminate the upper square tubes, and replace them with two arches running diagonally from the strut towers

It looks like the aluminum box sections with front and rear end plates act as a monocoque. Your suggestion is a reasonable one. Or they might turn the top and bottom box into a single U-shaped piece.

Here's how they handle it on the MaRussia supercar: