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Aerodynamics in off road racing

michael_loomis

Well-Known Member
You can test major aerodynamic drag questions like this - just get an airspeed sensor (pitot tube) for your data system and run the truck at full speed so it's drag limited. Do this several times back and forth over a relatively smooth paved surface, like a runway or deserted Nevada road, logging the airspeed data. Then make your major aerodynamic change (e.g., seal up the back of the cockpit), and do the same test again.

You can then compare your top airspeed with the cab sealed and with the cab unsealed. Since you make a number of passes, small variances will tend to average out. And since you're looking at airspeed, rather than ground speed, you will factor out the influence of any wind. This should be wildly cheaper than a wind tunnel, and good enough when you're looking at huge changes like sealing versus unsealing the cab. But it's probably not accurate enough to help you with smaller changes, like moving the light bar around.
IMO, still too many variables. WOT down a smooth road is not necessarily the body angle it will spend the majority of the time operating at. Might work for your rally car, but not on a TT.


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BajaFand

Well-Known Member
Ok. I can’t stand it any more. You have all miss the most obvious spot on a truck that makes lift and there for drag.

The hood. That’s why there are loovers in the hood. It’s not for cooling. The radaitors are in the back.

When you distroy the lift over the hood with loovers it kills the drag. This makes for more speed. And it increases stability at high speed by not lifting the nose and squatting the rear. It helps on L O N G jumps by flying the truck more level.

If you guys can find some pics of the old #8 Endure tt it had a lot of aerodynamic touches done to it. One of the big locations was inside the cab. The glare shield was streamlined into the cab headliner so the wind would flow through the inside of the cab smother. This dates to 1998. They learned that from tunnel testing at JPL in about 1992. The A & B pillars being flared helps too.

View attachment 192691

It’s hard to see but this the old class 4 that turned into the to 8 and its circa 1995. It’s hard to see but it had some of the aero inpovments done to the roof line.

View attachment 192693

Same truck with aero.



People have been looking at aerodynamics for a long time now.

And just to be clear. None of this was done for “down force”. That a bad thing. It’s just done to reduce drag.

Same truck. No aero.
Look at the difference in just the bumper and skid plates. I bet those were big improvements.


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TwistyItch

Well-Known Member
. The glare shield was streamlined into the cab headliner so the wind would flow through the inside of the cab smother. This dates to 1998. They learned that from tunnel testing at JPL in about 1992. The A & B pillars being flared helps too.

Same truck. No aero.
I was working at JPL in 1992 and am not/was not aware we had a wind tunnel as our mission was unmanned space missions where aerodynamics don't really come into play (as far as I know). Not that big a place really so I am surprised to hear this. Just the same, I am surprised they managed to get it done there even if it existed. Pretty cool environment at JPL so I bet they had fun doing it as a great change of pace for the engineers.
 

Josh 8

Well-Known Member
Ok. We are splitting hairs here.

For 100% clarity, I wasn’t a part of the team in the early 1990’s. I showed up about 1998. The first year of the trophy truck. They still had the 8 truck in the room next door. I started chasing with them in Mexico about 2002. I have never been a paid employee. Only a chaser/crew/volunteer member.

I could easily be wrong about the wind tunnel testing being at jpl. It vary well could have been cal-tech. Isn’t that the just about the same location north of Pasadena?

Anyway. The truck they did the testing was the Furicowa? Image truck. I know I spelled that wrong. It was a beautiful 8 truck that was built by a guy with a name close to that in riverside. Never raced. Just the image truck for the rought riders. They used it in the tunnel. Dave told me they raised the wind speed up to about 150-160 mph on the top end and the air going through the cab got his head wobbling so bad that he nearly passed out. Even holding the helmet strap down.

I sold that truck for them when they closed the shop to a machine shop guy in Orange that made parts for the super hydra 400 transmission. I can’t think of the name but I know guys here will know the truck and owner of it.

I just thought of this too. I know just a little of the history of Enduro Racing, and Dick and Dave. I just remembered this time of about 1992 corispons to when the Craftsman truck series began in NASCAR. I am not 100% sure of the details but I was always told that Dick and Dave were one the first if not the first guys to get that going. It might have been Landfields baby. Not sure. But there was deep involvement with the team in the nascar truck series in the beginning. This would have been through the Ford factory.

When the nascar trucks were developed, (it’s speculation) they vary well could have got the off road truck in the tunnel for some base line data numbers. I am not sure about that. But it would make sense as to how it happened.
 
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TwistyItch

Well-Known Member
You are right in that it is splitting hairs and I did not mean to sound dubious, just that I thought I might have missed some cool technology onsite. Caltech runs JPL for NASA, technically I guess I was a Caltech employee. Yes they are pretty close to each other. JPL is in the arroyo to the east and Caltech is in Pasadena towards south Pasadena (if memory is not too messed up :). Caltech I can believe has a wind tunnel! And as posted here by Offspring there is proof. At JPL we had facilities for zero gravity testing (basically drop tubes) so if you need to test it's performance on the way down then JPL is your place! Cool bit of trivia for me. Thanks for the education. In space there is no drag but it would be a lonely race...
 
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BajaFand

Well-Known Member
Ok. We are splitting hairs here.

For 100% clarity, I wasn’t a part of the team in the early 1990’s. I showed up about 1998. The first year of the trophy truck. They still had the 8 truck in the room next door. I started chasing with them in Mexico about 2002. I have never been a paid employee. Only a chaser/crew/volunteer member.

I could easily be wrong about the wind tunnel testing being at jpl. It vary well could have been cal-tech. Isn’t that the just about the same location north of Pasadena?

Anyway. The truck they did the testing was the Furicowa? Image truck. I know I spelled that wrong. It was a beautiful 8 truck that was built by a guy with a name close to that in riverside. Never raced. Just the image truck for the rought riders. They used it in the tunnel. Dave told me they raised the wind speed up to about 150-160 mph on the top end and the air going through the cab got his head wobbling so bad that he nearly passed out. Even holding the helmet strap down.

I sold that truck for them when they closed the shop to a machine shop guy in Orange that made parts for the super hydra 400 transmission. I can’t think of the name but I know guys here will know the truck and owner of it.

I just thought of this too. I know just a little of the history of Enduro Racing, and Dick and Dave. I just remembered this time of about 1992 corispons to when the Craftsman truck series began in NASCAR. I am not 100% sure of the details but I was always told that Dick and Dave were one the first if not the first guys to get that going. It might have been Landfields baby. Not sure. But there was deep involvement with the team in the nascar truck series in the beginning. This would have been through the Ford factory.

When the nascar trucks were developed, (it’s speculation) they vary well could have got the off road truck in the tunnel for some base line data numbers. I am not sure about that. But it would make sense as to how it happened.
Dave Leeper is the one who bought it but I believe sold it recently.


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BajaFand

Well-Known Member
Ok. We are splitting hairs here.

For 100% clarity, I wasn’t a part of the team in the early 1990’s. I showed up about 1998. The first year of the trophy truck. They still had the 8 truck in the room next door. I started chasing with them in Mexico about 2002. I have never been a paid employee. Only a chaser/crew/volunteer member.

I could easily be wrong about the wind tunnel testing being at jpl. It vary well could have been cal-tech. Isn’t that the just about the same location north of Pasadena?

Anyway. The truck they did the testing was the Furicowa? Image truck. I know I spelled that wrong. It was a beautiful 8 truck that was built by a guy with a name close to that in riverside. Never raced. Just the image truck for the rought riders. They used it in the tunnel. Dave told me they raised the wind speed up to about 150-160 mph on the top end and the air going through the cab got his head wobbling so bad that he nearly passed out. Even holding the helmet strap down.

I sold that truck for them when they closed the shop to a machine shop guy in Orange that made parts for the super hydra 400 transmission. I can’t think of the name but I know guys here will know the truck and owner of it.

I just thought of this too. I know just a little of the history of Enduro Racing, and Dick and Dave. I just remembered this time of about 1992 corispons to when the Craftsman truck series began in NASCAR. I am not 100% sure of the details but I was always told that Dick and Dave were one the first if not the first guys to get that going. It might have been Landfields baby. Not sure. But there was deep involvement with the team in the nascar truck series in the beginning. This would have been through the Ford factory.

When the nascar trucks were developed, (it’s speculation) they vary well could have got the off road truck in the tunnel for some base line data numbers. I am not sure about that. But it would make sense as to how it happened.
Didn’t Walker play a big role as well as Rob Mac to some degree?


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Josh 8

Well-Known Member
Dave Leeper is the one who bought it but I believe sold it recently.
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I cant remember the name. But I was at Culhane's shop and he told me the owner was either selling it or sold it about a year ago. So that sounds right.

Didn’t Walker play a big role as well as Rob Mac to some degree?
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I do not know. I am sure Todd Z or BroG would have an idea. They seem to have most of the history on micro fish.

Any way, back in the day, Dan and Dave were really secretive about there set ups. Talking about this here 20 years ago would have got me thrown of the shop for good.

They still have secretes that I don't see anyone using. Enduro probably did more with less that any other "pro" team. Those guys have been a positive influence on me and I have the highest respect for them.
 
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jcorsico

Well-Known Member
IMO, still too many variables. WOT down a smooth road is not necessarily the body angle it will spend the majority of the time operating at. Might work for your rally car, but not on a TT.


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Okay. Just lower the back of the car. Use some ratchet straps to pull down the rear suspension, and do the test. You don't need a $50 million wind tunnel to do basic aero testing.
 
NASCAR fabricators in the early 70's did a fair amount of use with the roll cage tubing for fuel storage. They were finally caught and today the tubes are still tested for fluid storage.
SST trucks use the cage as radiator coolant transfer lines.
I saw pictures of them in SA with yarn taped to it when they were having overheating issues. I don't recall the Hummer or the Gordini's getting any real tunnel time. Where is Fly, he would remember all this.
The Monster had extensive wind tunnel testing at GM, They also used GMs test facility in AZ for real top speed development. What they learned from that brick they carried over to the TT. As for the Gordini, I think most of the aerodynamics were done in the tube with a virtual model rather than a scale model or full-size mock up. Then the full size parts are CNC cut as negatives. The last 10 years this has been the process for most development. Rather than mill the parts then cast, just mill the mold and make parts. When you do this, it's more styling guys and less engineering so stuff like cooling flow gets missed or underappreciated.
I'm sure the Dakar guys are missing The RG Show. I bet he has the name your price tool. But that is just a guess.
 
To get real useful info on a TT in a wind tunnel, you would need a 5 post rig in it. There is such a change in ride height and pitch on a TT that static testing would tell you how it does across the lake bed and that's about it.
You can get pitch and yaw numbers pretty easy. But now with the available cad model plugins the data available on any design
is pretty vast.
 

Wilson

Well-Known Member
You can get pitch and yaw numbers pretty easy. But now with the available cad model plugins the data available on any design
is pretty vast.
It's been a few years since my "rocket scientist" days but I believe that you are referring to calculated predictions rather than empirical data..... Predicting performance via a software package may be convenient but the results will only be as good as the test article modeling, the sophistication of the software and the test parameters used. Garbage in, garbage out; you would still need to verify the software predictions with physical testing of some sort.....
 
Some thoughts from the peanut gallery here. In off road racing downforce isn't a huge concern. However aero can assist in any form of motorsports. IF you can cut down on drag then that'll help. It can help speed marginally but it can also help with fuel range. Maybe it'll only save a gallon but over a long distant that adds up. What i would like to know is how much the enclosed rear of some trophy trucks (like the black diamond) can help. It looks like it'll create an "air bubble" allowing high velocity air to flow over it. What do all of you think?
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Some thoughts from the peanut gallery here. In off road racing downforce isn't a huge concern. However aero can assist in any form of motorsports. IF you can cut down on drag then that'll help. It can help speed marginally but it can also help with fuel range. Maybe it'll only save a gallon but over a long distant that adds up. What i would like to know is how much the enclosed rear of some trophy trucks (like the black diamond) can help. It looks like it'll create an "air bubble" allowing high velocity air to flow over it. What do all of you think?
Two different people have told me that it makes it less turbulent in the cockpit. Which makes me think that youre correct. It creates a buffet and air goes around the cab better or easier. I wonder if dust does also...
 
Two different people have told me that it makes it less turbulent in the cockpit. Which makes me think that youre correct. It creates a buffet and air goes around the cab better or easier. I wonder if dust does also...
huh never would have guessed it makes the cockpit less turbulent. It would help with dust, ass its a particulate that floats in the air. Dust can actually demonstrate aerodynamics. If you look at the unlimited class pikes peak cars back when it was primarily dirt, you can see columns of dust come out through the venturi tunnels/ diffusers. But if it creates a bubble then that would mean the dust already in the cockpit is just floating and circulating at low speeds.
 
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