Interesting Aerodynamic Cars (Mike Vetter's ETV, also Avion)

[NeilBlanchard]

"Speed holes"?

[freebeard]

Homer is from the episode… | Simpsons Reference
wwwDOTsplittinghairsDOTorg/simpsons-reference/tag/homer/
[bullets hit the car] Homer: [suspicious] Hey, what are all these holes? Salesman: [quickly] These are speed holes. They make the car go faster. Homer: Oh, yeah.

What did you think it means? Speed holes legendarily make the car go faster. Maybe the better braking let's you get deeper into corners, etc. They would also serve as telltales for wheel-spin, like painting a white stripe on the tire sidewall.

[NeilBlanchard]

Okay, satire meets reality; got it.

[freebeard]

I guess I shoulda/coulda used 'air quotes'. Did not see that coming. I thought I'd get raked over the coals for posting a motorcycle in an Aerodynamic Cars thread.

moving right along.


http://jalopnik.com/the-lf-sa-is-lexus-freakish-answer-to-mini-1688569381

The Lexus LF-SA concept.

[cosmick]

After looking through the first 30 pages of this thread, I see they all have the same problem; side by side seating, rather than inline. That triples the total drag all by itself. Now I really want to get going on my own single seater or inline 2-seater, with either a 4G63T Mitsubishi engine or a turbo propane 22R Toyota engine in front of a V6 Passat transaxle.

[freebeard]

That triples the total drag all by itself.

Citation needed.

Would that drivetrain be front-engined or mid-rear?

[sgtlethargic]

Originally Posted by cosmick

After looking through the first 30 pages of this thread, I see they all have the same problem; side by side seating, rather than inline. That triples the total drag all by itself. Now I really want to get going on my own single seater or inline 2-seater, with either a 4G63T Mitsubishi engine or a turbo propane 22R Toyota engine in front of a V6 Passat transaxle.

I'm with you. Not everyone needs a 4-seater or more. I know I don't. Cut the frontal area and weight.

I've been thinking it'd be safer for a side-impact (T-bone), too, if the occupants were centered, further away from the doors.

I like turbo propane, too. But, I don't want the tank in the trunk again. It's easier and more assuring to have it completely separated from the passenger compartment.

Any more info on your plan?

[Madact]

Originally Posted by cosmick

That triples the total drag all by itself.

Originally Posted by freebeard

Citation needed.

Complex question with no easy side-by-side comparisons... but in the ballpark. CdA is Cd * A and you can reduce both those factors substantially for an 'inline' design.

For the very low speeds cars travel at, the optimal fineness ratio is probably somewhere in the 1:4 to 1:5 range (form drag being somewhat dominant over skin drag), which is much easier to achieve in reasonable length if the vehicle isn't as wide - just take a look at how much length a good boat-tail adds to a hatchback. With an inline design you can achieve a (seemingly) ridiculously low Cd and still have something that doesn't require a special parking space to fit the tail.

The frontal area may not quite go down by half, though you can get close to it - and that's quite a substantial factor.

Multiply both of those together, and a ballpark factor of 3 isn't unreasonable. It would only require a 42.5% reduction in each of Cd and A, for example, both of which are quite achievable.

A local example of an 'inline' design: Trev (two-seater renewable energy vehicle) and there are even reasonably comprehensive build instructions at Trevipedia . Though I can't find any Cd or CdA info, it apparently achieves 62 Wh/km (6.2 kWh/100km) at 80-90 kph cruising, which isn't too shabby compared with 'side-by-side' EVs currently on the market.



(Yes, I know this has been linked in this thread before, but it was a while back and it's relevant to the discussion)

[freebeard]

Fair points, but dropping a wheel is hardly 'all by itself'. I though fineness ratio should be 2.7 to 4 to 1.

I could see 75% of frontal area, Cd maybe the same. Sans other changes.

[Occasionally6]

Originally Posted by cosmick

After looking through the first 30 pages of this thread, I see they all have the same problem; side by side seating, rather than inline. That triples the total drag all by itself. Now I really want to get going on my own single seater or inline 2-seater, with either a 4G63T Mitsubishi engine or a turbo propane 22R Toyota engine in front of a V6 Passat transaxle.

I could live with a SmartForTwo/Mitsubishi 'i' driveline but otherwise I'm totally with you. (VW, where's the One Liter car you promised ?)