Unconventional application of downforce?

[Beercaps]

Came across some interesting photos when I googled “time attack truck” and saw a few different builds/renders of small pickups with those chassis mounted GT wings sticking up behind the bed, presumably attached to the frame rails. It made me wonder if there would be any advantage/disadvantage if someone attached the wing directly to the rear axle so the downforce was applied directly to the wheels instead of having to transfer through a constantly reacting suspension. I tried searching up any example of this but didn’t have any luck, likely because I can’t seem to word it how it should be said but I know I can’t be the only person who’s thought this at some point. If anyone has some insight or knows of an existing example please chime in. It’s not currently something I’m considering for my own project but if the build dictates the need I’ll start considering options.

[89'HBV6]

Well, just read my tag line quote, below... v v v v

[Deerhurst]

The wing would be moving with the road which may shake it apart. Otherwise that sounds like the logical place to apply force to me.

[Beercaps]

Originally Posted by 89'HBV6

Well, just read my tag line quote, below... v v v v

I'm familiar with "if it was meant to be fast it wouldn't be shaped like a brick" but things like time attack kei cars and nascar trucks still exist.

This project I've been dragging my feet on takes inspiration from several subcultures of the car world from rat rods to kaido racers, the end goal is "visually abrasive, weird, and the balls to back it up". Drifting is cool, but I've shifted my priorities more towards rolling start higher speed sort of stuff.

I still plan to mess with KA for a bit, like fully documenting a carburetor swap (instead of offering half assed info and suddenly disappearing from the face of the earth the moment someone has a question), but I've got a spicy swap planned for the future. Did you know that a 428 police interceptor can be brought down to 500 pounds or even less with the right aftermarket aluminum parts? (That's the same weight range as an LS)

I admit I tend to think of weird things like "could I use my rear mounted radiator as a heater core?" or "is it better to put the downforce on the frame or the axle directly?" or "not that I want a rotary but how much of the cab would you need to carve out to make a mid engine rotary swap work?" The difference is, fabrication is my trade so I'm not just day dreaming or diving in blind.

[Beercaps]

Originally Posted by Deerhurst

The wing would be moving with the road which may shake it apart. Otherwise that sounds like the logical place to apply force to me.

Definitely couldn't modify some ebay special and expect it to last very long, but there are 800+HP time attack monsters with experimental homemade aero that don't fall apart so I know I have a decent chance.

I've seen the skill level of some of the japanese "fabricators" and it makes my butt pucker sometimes. Like, you can build a high output 4g63 in your sleep but you somehow managed to make spatter while tig welding and your sideskirts are plywood?

[street_rulerr]

you wouldnt get the fulcrum action. imagine the axles being fixed and not sprung, maybe hardmounted is the right word. with the wing hanging off the back of the frame you get a fulcrum action around the front axle. If you were to mount a wing directly to the axle it would be pushing directly down, no fulcrum. on a time attack car it might make sense, or a hill climb but the added drag and weight probably isnt right for a track car that has to lap consistently. plus very few actual race cars, if any run a solid axle any more so pushing directly o the axle isnt really possible.

[PorknBeans]

Originally Posted by Beercaps

I'm familiar with "if it was meant to be fast it wouldn't be shaped like a brick" but things like time attack kei cars and nascar trucks still exist.

I recall the NASCAR trucks used a hard “tonneau cover” over the bed and a tailgate mounted wing for the down force. The tonneau cover was probably not a vinyl cover, as there was visually no sag where the air hit the tailgate area. So probably a sheet metal cover cut to size and mounted.

Come to think of and visualizing those race trucks. I don’t believe those trucks even had a tail gate.

Edit - Here’s a photo of one of those trucks and their set up. No tailgate, “tonneau cover”; roll bar and rear mounted wing with the support hardware:

[Deerhurst]

Originally Posted by Beercaps

Definitely couldn't modify some ebay special and expect it to last very long, but there are 800+HP time attack monsters with experimental homemade aero that don't fall apart so I know I have a decent chance.

I've seen the skill level of some of the japanese "fabricators" and it makes my butt pucker sometimes. Like, you can build a high output 4g63 in your sleep but you somehow managed to make spatter while tig welding and your sideskirts are plywood?

800hp time attack vehicles have suspension and are practically rebuilt every time they run.

[Beercaps]

Originally Posted by street_rulerr

you wouldnt get the fulcrum action.

I was coming here to post about my racing cart epiphany but you beat me to it. (They use solid mounted live axles and while they do go for some aerodynamics literally no one uses a rear wing.)

Originally Posted by PorknBeans

I recall the NASCAR trucks used a hard “tonneau cover” over the bed and a tailgate mounted wing for the down force.

My bed was trashed and anyone selling a clean bed wants more than I paid for the truck so I’ve got a lot of open frame to play with. I could make it look like some 50’s future tech riveted aluminum airstream mess if I felt like it but I’ve got a 15 gallon keg I REALLY want to use for a gas tank. To stay legal I’ll be using sections of 55 gallon drum for rear fenders with home plates for mud flaps. The plan is mount the fenders off the bolts on the back of the hub so they travel with the wheel instead of getting bashed.

Originally Posted by Deerhurst

800hp time attack vehicles have suspension and are practically rebuilt every time they run.

I was just getting at the fact that for the most part time attack aero is a lot of shoulder shrugging and “let’s see what this does” and the quality of construction is often (and I’m being nice here) questionable. So if they can run their home brew and it doesn’t disintegrate on the front straight I feel like I have a shot. Good Lord willing at the end of it all I’ll be running an all motor 428 FE so you can overbuild and push like 450-500 hp and 500 tq without sacrificing reliability from what I’ve been reading. The kind of output to weight ratio I’d be looking at is enough to do some damage.

[street_rulerr]

one of my favorite quotes comes from dave coleman, engineer at mazda and former editor of sport compact car magazine...it goes something like



air is generally invisible and impossible to predict. so we spent hours having uninformed conversations about whether or not this would work.



my personal take on predicting air movement, you can analyze it by the molecule or the cloud but whatever approach you take its gonna be wrong.