Making a more efficient, aerodynamic soapbox gravity race car

[freebeard]

...what do you think?

Not dangerous? I was going by the pic at Permalink 252, and I was fishing for information on the white wedges forward of the wheels.

[aerohead]

Originally Posted by freebeard

That's the diagram I don't get.

I presume l(c) is overall length? What is the relationship between the angle and height graphs? The two curves don't track each other.

Maybe if there was a curve for l(d)/l(c)=1 I could get the sense of it.

They only offer us two different lengths,as a percentage of overall body length and without a 3rd example,we've got nothing to create a curve from,nor interpolate/extrapolate.
With the two versions shown they only structure the drag and lift as a function of up-sweep angle.
For us,we can only inspect what we've got and see which variety would best suit us,then go from there,hoping for the best.

[aerohead]

Originally Posted by orengomotors

i don't get it too

Here you can see that a diffuser isn't even possible

With the engine in front,the diffuser IS possible,and it can begin very 'early' on the underbody,allowing the lowest drag version

Here,whatever is under the pan,it won't allow the diffuser to begin as early

With the race car,there will be a point where the hard points clearance will just allow the diffuser to begin.Then it's a matter of what you want,rear downforce,or low drag.
Some current supercars (Bugatti and Ferrari),have active flaps which 'close' the diffuser for straightaways,and 'open' them for corners.
Here,you can see the 'shiny' diffuser flaps of the Ferrari LaFerrari

[freebeard]

Here you can see that a diffuser isn't even [always] possible

AKA the Beetle problem.

[noultimatum]

Don't have enough posts to make a link but I'm referencing this last video that OP posted watch?v=Lv3KRNy8E1U.

I just wrote a long winded response only to have the site tell me I wasn't logged in... I'll try to remember it as best I can. I want to focus on your driving since that's where I could contribute.

A few points before I critique the video.
A. You jerk the wheel a lot for seemingly no reason. Any time you turn like that it's an unnecessary slow down and increase in distance run.
B. Your camera is at a bad angle. Can you put it on the bottom of your chin? That way we can see both wheels.
C. I see you missing the apex a lot. When you have a vehicle without power, then driving/vehicle efficiency are your only variables.

Okay here's a breakdown

8s You jerk the wheel right then left.

16s You shouldhave just aimed for the hay bale on the right as soon as you started.

19s Should have stayed far right and just drifted gently left over the next 30m or so.

21s You move the wheel unnecessarily again.

25s You should have hugged the left curb since you're not going at your best speed to where you need to use that much of the track.

32s Same here. You could have just stayed far left.

39s First speed where you're going fast enough to use the whole track, but I can't see your left wheel so I can't judge, but you turned very tightly to the right and didn't use the road after the turn

46s You add a slalom. WHYYYY. kidding.

50 s. You have almost a meter to the curb. You're now going as fast as you will through these turns. You need to use the whole track. Same on the exit. You only use the left lane after you turn.

1:00 Is your best turn probably.

1:04 At this point you should have hugged the right curb and ridden as close to it all the way to the finish.

Good luck in the next races.

[freebeard]

Welcome(?) to Ecomodder. Is that Dallas, Oregon? since 2011?

You can be logged in and it will time out behind you back. Always hit Select All/Copy before you Post or Go Advanced. Sometimes reloading the page doesn't help and you have to leave it and come back and Paste again.

A big advocate here of the [hypothetical] hypermiling technique 'Drive Without Turning' would be slowmover. When I'm driving the Coast Range, I try to turn only in the middle of the short straights and hold a steady curve that touches the apex. A quick body roll while the car is not turning and then steady as she goes the rest of the time.

[noultimatum]

Haha. Edited... TX . Thanks for the comment. And yeah. Lesson learned about copying the text before submitting.