Aerodynamics in off road racing

[bajaxp]

I am curious, why there is not much consideration for aerodynamics when building off road cars today. I have asked a few opinions and the overwhelmingly consistant theme that comes back is that 'it doesn't matter.' Really? Most desert race cars and trucks look about as aerodynamic as a bathroom door (haha). I find it odd that 800 hp Trophy trucks 'only' go 140-ish, and 120 hp 1600 lb Class 12's can't even break 100 mph. Back in the 70's and 80's you had Big Oly and MT's Challenger with big wings and Parnelli even went so far as to have his driving lights hidden and tucked into the leading edge of the aforementioned 'wing.'

So what say you Desert Familia...could better aerodynamics improve current desert rigs? Traction, cornering, top speed, comfort, etc.

 

[Will_Higman]

This should be a good thread I think opinions have changed greatly over the last 10 years.

The more aero the better…

 

[martein]

A lot of people are changing to smaller lights and LED's and finding another 5-7mph of top speed I know we did. It is hard to get an aerodynamic package up front with arms swinging 30". If you look at a lot of the class 1 cars they make an attempt to smooth the curves behind the tires and suspension but bottom line is your aerodynamics are shot by the time it reaches the body. I know our car builder has moved just about everything around on the car trying to free up some air flow but there is only so much he can do. The full body classes have it a lot easier

 

[Ol' Curmudgeon]

The ground clearance issue certainly complicates any aerodynamic improvements.

Has anyone tried skirting to direct airflow out from under the vehicles?

The frontend of the Class 1 I raced got pretty light over 110 MPH, with the front skid plate ramming air under the floorpan.

 

[GunnSlinger]

I am curious, why there is not much consideration for aerodynamics when building off road cars today. I have asked a few opinions and the overwhelmingly consistant theme that comes back is that 'it doesn't matter.' Really? Most desert race cars and trucks look about as aerodynamic as a bathroom door (haha). I find it odd that 800 hp Trophy trucks 'only' go 140-ish, and 120 hp 1600 lb Class 12's can't even break 100 mph. Back in the 70's and 80's you had Big Oly and MT's Challenger with big wings and Parnelli even went so far as to have his driving lights hidden and tucked into the leading edge of the aforementioned 'wing.'

So what say you Desert Familia...could better aerodynamics improve current desert rigs? Traction, cornering, top speed, comfort, etc.

Ive always wondered the same myself, and have always heard the same line "it doesn't make that much of a difference" but personally I think it would. To be quite honest, I think it has a lot to do with the way it would make a car/truck LOOK and thats why some people forgo the thought entirely.

If im not mistaken, Andy Mac took his Geiser into a wind tunnel when they first got it and tried a couple different things out to reduce the wind resistance.. shortly after, the front valiance became widely popular with TT teams running Geisers. Im prob way off on my info but I recall hearing him talk about this topic before..

 

[mike mcqueen]

I went to the GM wind tunnel with the SPD chevy of BJ Baldwins, with the collins crew. We learned quite a lot. They start off with a given number with the first pull (air) then you make changes for each pull. We managed to get the number way down with a lot of changes, Then we put the light bar on which brought it back to the starting point. The new small lights are a good help. The front air dam aka spoiler,or cow catcher(its original name from SCCA) is a plus, To be more effiecient
it has to have a forward pointing lip at the bottom. One big plus is to seal the bottom as in DAKAR cars. The tires are always a problem in any race vehicle. "think like the wind"

 

[bajaxp]

I went to the GM wind tunnel with the SPD chevy of BJ Baldwins, with the collins crew. We learned quite a lot. They start off with a given number with the first pull (air) then you make changes for each pull. We managed to get the number way down with a lot of changes, Then we put the light bar on which brought it back to the starting point. The new small lights are a good help. The front air dam aka spoiler,or cow catcher(its original name from SCCA) is a plus, To be more effiecient
it has to have a forward pointing lip at the bottom. One big plus is to seal the bottom as in DAKAR cars. The tires are always a problem in any race vehicle. "think like the wind"

Mike McQ...great info and thanks! Can you elaborate on 'One big plus is to seal the bottom as in DAKAR cars.' Are you talking skid plate or side skirts?

 

[mike mcqueen]

Most of it is sealing the bottom from the front lower a arms back. shielding the bottom so air will not get up into the car.
Air will blow the hood off almost any car that the hood is not latched down. I know from experiance. The A arms are done with flexable material that will move with suspension. Smooth is slippery.

 

[Rory]

Heard the same story from Robbie Goerke from Collins. Robby Gordon has also done wind tunnel testing and you can see the added material behind the "cow catcher" down to the bottom of the front skid plate, i believe BJ has the same sort of design. Light bars up top are almost like a mini parachute but with the Rigid/Vision X type lights being used now it helps.
Rumor was when Challenger IV was first built did a 150mph on the asphalt at the Mexico races (Per Danny Thompson and John House the builder) but was VERY squirrely and scared the hell out of Mickey Thompson. They kept playing with the narrow wing on top of the car then finally took off the back of the narrow part and put on a "top fuel" type wing and that seemed to calm it down. Talking with Bob Gordon and Parnelli about wings, they said they worked great but you constantly had to adjust them (electric actuator) for the terrain or it would upset the vehicle. Not sure what a wing would look like on a TT but 'd love to see some on a couple class 1 cars.......

 

[smt racing]

Here is a good link to some basic principles, in a nut shell its more important how you leave the air then how you enter it... good post

http://www.gmecca.com/byorc/dtipsaerodynamics.html#AeroGeneral

 

[randy s]

it seems like the course would be the factor as to how much aero would make a huge difference..on tight, technical, difficult courses, aero would be less of an advantage than the longer more wide open courses. kind of like bristol vs. daytona.....armin swartz [sp] runs a rear spoiler on his bmw tt and i don't know how much of an advantage he's attained. but i'm still having problems trying to figure out why the dimples on a golf ball make it go further than a smooth ball in tests so what do i know?

 

[Wendell #527]

Last years Mint 400 was our first time with a big light rack on top of our 5 car. As soon as we put the light bar on, it felt like it was doing wheelies at any speed over 85 mph. That Aero problem made me buy a Ridgid light bar with two fuegos. I raced that set up in last July's MORE race, and the Aero was better, but I couldn't see good enough. I ended up going back with 75 watt HIDs, I just ran two of them mounted real low right in front of the mirrors and two fuegos low on the front. That fixed my Aero problem, plus I can see! Now I made my car taller just because me and my co-drivers are tall. I bet that extra 4" of height affects Aero too. I just can't do anything about it... Aero is definitely important even in limited classes.

 

[mexracer10]

I have not seen it mentioned but gearing i think has more to do with over all top end than aerodynamics. Yes a class 12 car has enough hp to break 100mph but the gearing will not allow it, most cars are geared so they will stay on the power band of the engine, not all top end, how many race cars have gearing in the last gear close to or at 1:1, rare is it overdrive cus its not a fuel economy thing its a racing thing and a hp thing and a control thing not a top end speed thing. But i guess any little advantage will help in particular a race such as the b1k the long way where there are long fast roads some teams might change the gearing around to allow faster top speeds.

 

[DBMETALWORX]

I've thought about building a wing into the front of the hood on buggies, for some front down force. Instead of making it a point with a raised rounded hood. Never got around to it though.

 

[Zambo]

I understand the new Baja Designs LED light bars are going to let a lot of fast cars go faster without sacrificing light output.

 

[NIKAL]

I think a lot of guys have played with aero in the past. RG has probably done more then anyone else, but that is probably because he has had the resources to do so. I remember seeing all the louvers on the old Valvoline TT (now Riviera) and thought they were so different. Nobody was doing that back then. I think it was RG that brought the front valance and front skirting to desert racing. Now everyone does the valance. Look at RG's cooling package. His radiators sit low and do not disrupt air flow through the cab like 90% of the TT's do.

Developing a good aero package could cost as much as the vehicles themselves and that is probably the biggest reason it is not in our sport today. Look at NASCAR these teams and manufactures, they spend millions of dollars on wind tunnel time and simulators. I think one of the biggest hurdles is the fact that the goal to aero is to move the air over the vehicle. In our sport that is an impossible challenge as the vehicle jumps in the air and the suspension travels up to 30 inches on the unlimited classes. Due to the current suspension designs and our goal of transferring the weight to the rear wheels we lift the fronts of the vehicles causing the bottom of the cars to act as wings.

Every class can find an improvement by just thinking of aero and designing the vehicle with it in mind. Even our 5/1600 had aero thought into it. Our car sat lower then most, we cut/sloped our hood and rear fenders down, and tried to direct the air away from under the front hood. We even sat lower then many and at one point discussed having our co-riders sit several inches lower then the driver like in a rally car to help with lowering the center of gravity and keeping them out of the air flow. Problem is if you cant see you are more likely to get sick and it is an uncomfortable scary ride.

Does anyone remember Nye Franks Mighty Mouse? If I remember right that truck was designed with air bags, so they could lower the truck in the flat high speed sections.

 

[Forty1Racing]

Achieving better Efficiency is always desirable. But if I had to pay to have a truck tested in a wind tunnel, I would have to ask, how often am I really going 120+ in the desert for extended periods?
Then again I've never driven a TT so what do I know.... Haha

 

[mike mcqueen]

Having the truck work in the mid range is more important than overall speed. All the advice on here is correct. Ive had the pleasure of working with John House, take what he says with a few grains, after all
mickey won the year after John.

 

[bajaxp]

Great insights and input. As I said in my original post...in addition to top speed, what about traction, cornering and comfort. I look at those Outlaw dirt track cars and the HUGE wings they put on them! What about the comfort of a sealed cockpit like many of the DAKAR cars have? How could aerodynamics help put 600 to 800+ hp to the ground better in a Trophy Truck or Class 1. Thoughts? Good stuff!!

 

[RocketMan]

when i asked an aero guy here at work what would make our truck better(class 7 unlimited) he said front spoiler with a splitter min 1/2 extending forward of the spoiler, move all the coolers so air can flow through the cab, add a splitter to the bottom front edge of the roof (see above size),and tear drop any tube that is in the air flow....a brick has better aero properies than a round tube/cylinder ......