Scale wind tunnel model testing

[98ciHemi]

Has anyone here tried anything like this? I am considering trying to make a 1:16 scale clay Escort so that I can play with different aero stuff. I have limited access to a small windtunnel, and I have done wood sculpting before, so I believe that I could make a pretty decent model. Would this be an accurate way of testing? The way the wind tunnel is set up now it measure only lift and downforce, but I may be able to make it measure force inline with the car if I work on it. I also may be able to bum a fog machine to judge airflow. Any thoughts?

[DanStokes]

A couple of lads from Dayton Ohio had pretty good luck with this syatem. Their tunnel is now in Dearborn, MI. It's a perfectly viable method but is only as good as the instrumentation and your ability to accurately scale the car and the measurements. POST PICS!

Dan

[White Monster]

Sounds worthwhile Walt, go for it and report back here on your results.
;)

[DanStokes]

Anyone have a model of a '78 Camaro lying around? I'll send it off to Walt.

[98ciHemi]

Gimme the track widths, wheelbase, tire size and wheel size and I will start working on a base for it. My plan right now is to form the bulk of the car with pine or basswood, and then lay up clay around that. To measure the drag, I will make a small air cushion table sort of like an air hockey table to get eliminate surface friction, and then use my airbrush compressor as an airpump. the car will go on a base that will ride on the air cushion and then be held back by a light rubber band. I can use a powder scale to establish the rate of the rubber band, and then use a scale to measure rearward movement of the car, and hence measure the drag of the car. If that makes sense to anyone. Downforce is easy, and just requires fixing the car to a kitchen scale and sticking it in the wind tunnel.

[98ciHemi]

A couple of lads from Dayton Ohio had pretty good luck with this syatem. Their tunnel is now in Dearborn, MI. It's a perfectly viable method but is only as good as the instrumentation and your ability to accurately scale the car and the measurements. POST PICS!

Dan

And those lads you speak of were losers. Hmmph. Bicycle mechanics. :)

[White Monster]

Anyone have a model of a '78 Camaro lying around? I'll send it off to Walt.


Umm, Dan, I know you have a Camaro, but Walt has an Escort.
He wants to check out different aero stuff on HIS car.

So, if anyone has a 1:16 scale Escort model lying around, sent it to Walt.
;)

[studemax]

Keep in mind you can do aero testing in water, too.
Since water is denser, you can get good results at lower speeds.
Just an idea, if you'd like to follow it.

[98ciHemi]

Hadn't thought of that. Air seems a little easier since I already have a windtunnel. I may keep that in mind though.

[greenjunk]

It was my intention to do something similar to this and test a model of my camaro in it to see if I can replicate the results I learned in a real tunnel. seems like if you built your own tunnel with a couple digital meat scales you could get some sort of results assuming you had the fan to pull it.

[fahrenschnell]

Walt.....You never cease to amaze me.....Go for it.

Seth

[squirrel]

lmao...neat idea!

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=190343410833

[White Monster]

Good catch Jim.
Not sure if the 1/18 size will be a factor, but it is a 1984 Ford Escort RS 1600i Diecast model car ...

http://i.ebayimg.com/15/!Be-bQjgB2k~$(KGrHqEOKisEryPK(ZvEBK+drpC!T!~~_12.JPG

[98ciHemi]

That would sort of work, after removal of the spoiler and the front fascia. The U.S. spec Escorts used a different front end design. The Escort shown there had a stock drag cooefficient of .38. Not sure how good that is, but it gives me an idea where I am at.

I cut out my wooden base last night, and now I am putting wooden blocks together to form the bulk of the body. I will take pics of the base when I have it put together.

[White Monster]

Walt, yeah ... with the model being diecast metal, kinda makes it hard to modify it.
I am really interested in the progress and eventual outcome of this project.
Keep us updated as you move along.
;)

[squirrel]

pictures!

[DanStokes]

I was teasin' Walt that he could tunnel mine in addition to his. Just offering to help the young fella out with an additional test subject.





Anyone have a model of a '78 Camaro lying around? I'll send it off to Walt.


Umm, Dan, I know you have a Camaro, but Walt has an Escort.
He wants to check out different aero stuff on HIS car.

So, if anyone has a 1:16 scale Escort model lying around, sent it to Walt.
;)

[White Monster]

I was teasin' Walt that he could tunnel mine in addition to his. Just offering to help the young fella out with an additional test subject.


OK, that's your story and you're stuck with it !!
;D

[DanStokes]

I've been thinking about this. First of all, I'm guessing you would be better off with a hair dryer than the little compressor. What you need is volume, not pressure, and the volume out of that little compressor would be pretty low.

Second, the wind resistance isn't of much use if the car tries to fly. So for instrumentation you really want a 4 corner scale setup so you can get downforce on each wheel. The wind resistance measurement you were contemplating is useful, too, but only with enough and not too much downforce. Keith probably has some of these values for a full sized car that you can scale for the model.

Good luck - cool project
Dan

[squirrel]

two scales (front/rear) would probably work, since there should not be much (any) side to side difference.

[98ciHemi]

I will be testing downforce and lift, but since I have maybe 85 crank HP, I am thinking that staying on the road won't be a big deal. Anyway, since the weather here has gone crappy, and Mom's van is living in the garage, today, instead of working on the model, I am working on the support table that will provide the air cushion. I started with a piece of plexiglass and some faux wooden flooring scraps from a procect that dad is working on. The is what I have so far. And I came to the same conclusion about the airbrush compressor, but instead of that I will just use a regular garage compressor regulated down. Here are a few pics of what I have for now. Hopefully I will go to pick up the windtunnel tomorrow so I can work on figureing out fitment issues.

http://i293.photobucket.com/albums/mm57/RoninRDS/HPIM1671.jpg
http://i293.photobucket.com/albums/mm57/RoninRDS/HPIM1672.jpg
http://i293.photobucket.com/albums/mm57/RoninRDS/HPIM1673.jpg

Not pretty, but it should work. and if it doesn't, I am out maybe $3 in supplies.

[DanStokes]

Good start. I'll be curious to see if the compressor does the job. Remember the hair dryer or shop vac as a fallback.

Dan

[68 Valiant]

Just curious? With a scale test like this would you have to keep your weight proportional from the actual car to the model?

[squirrel]

Kind of depends what you're trying to do. My guess is he's looking to see what happens when he makes changes to the car (spoiler, dam, lowering, wheel covers, etc). so the percent change in drag is what's important, not the actual drag number

[98ciHemi]

Squirrel has got it. What my cd is isn't important to me. What I want to know is what I can do to make the car sleeker without making it takeoff. Tonight I used a floorjack under the front of the car to make the rocker panel level from front to rear. I then took and seperated my car into 8 5" sections from top to bottom. I then measured the smallest complete longitudinal dimension in each section. After that was finished I took some leftover flooring that was 5/16" thick and then cut it to scale size for the car. I now have 8 blocks from top to bottom that will form the base for my model.

[greenjunk]

I think you need to think more suck than blow. Blow creates turbulence, Suck creates happiness, I mean less turbulence ;D

[98ciHemi]

I just got some cool news in the way that if I program it, I can use the cnc mill to cut out the basic shape of my scale model from machinable wax.

[White Monster]

Cool, a project within a project.
We want pics !!!
;D

[terry russell]

Cool, a project within a project.
We want pics !!!
;D

X2
terry

[std]

I just deleted my whole long post.

[White Monster]

Remember, don't go faster than your license allows !!

Check out this site -> www.f-body.org/gears/

Plug in your tire size, ring gear ratio, transmission gearing and this site will give your theoretical speed at rpm and top speed. USE YOUR TACH to indicate your speed!

Good luck and be safe!

[TheSilverBuick]

That's been my gear ratio/rpm/mph calculator of choice for years. Found it when I had a '69 Firebird.

[Fordplay0621]

For my streamliner project, I built a scale model from Fiberglass and weighted accordingly.

The windtunnel was made from:
10inch PVC Pipe, 10 ft long
cut the side out of it
used CLear Lexan to make a window down the side about 6 ft long
put a platform inside with one inch markings the whole length, Masking tape and spray paint worked great.
Used a 10 inch fan with variable speeds, you can make wind cones for higher speed funneling air down the PVC Pipe.
used a hinge on the front of the platform and a jackscrew at the back to tilt the platform towards the fan.
I used a rolling platform specially made for the model to sit on and the wheels were up inside the model,
it ran down a rail made from welding rods end to end.


TEST
Set the model in
Turn the fan on
Tilt the table platform with the jackscrew
Model rolls toward the fan.

Results:
The closer the model runs towards the fan the more aerodynamic the car model is.
I tried 7 different nose cones for the Streamliner and found one that works very well.
Started with an uncarved styrofoam block as a Control Test
Then whittled it down, (actually made seven Blocks different) then started to fine tune them until I found my results.

Looks alot like a NURSE SHARKS NOSE. Go figure, Nature wins everytime.

[White Monster]

Randy, do you have any pictures taken during the testing or of the mock up wind tunnel, streamliner model or various nosecones, (etc.) ??

That would be cool for everyone to see and may be useful to Walt as well.
;)

[Fordplay0621]

I can t find them after I moved, a few people have seen the Model though, all banged up. I can draw a diagram for it and send it to him, if I can get an Address, right now I am in Savannah GA doing work on an Aircraft for Hunter Army Air field, but I can work on it at night here and send it to him. It worked well for what I was doing. There is a pic of the model on the front page of my website.

www.saltfever.com

[DanStokes]

Randy - glad to see a post from you. Hope all is going well. This has got to be a tough Christmas - remember we care.

Dan

[Fordplay0621]

Thanks Dan, It makes it all better to know everyone is here. I think I'm gonna build another Windtunnel to, and see if I can make a few more changes to the streamliner. Finally got a Sponsor for the Car and it is now gonna happen. hope to help out whereever I can.

I like the projects like this little Ford, just to see how fast it can go.

[White Monster]

I think I'm gonna build another Windtunnel to, and see if I can make a few more changes to the streamliner.
... hope to help out whereever I can.
I like the projects like this little Ford, just to see how fast it can go.


That's the spirit old boy !!
Make sure you take some pictures of your experiments and post them up, along with the notes of your observations and results.

[KeithTurk]

While all of this is interesting ... Walt you can most likely learn more doing real life coast down testing from say 70mph to 40mph... and measuring the distance.... make a significant change and then do it again... record every bit of information about the weather and time of day.... make temp checks on Everything... and pretty soon you'll know a ton about what works on your junk at 70mph and what works there most likely works at 120mph....

Wind tunnels are the most fun you can have with your pants on.... Better then racing and damn near as good as sex...

K

[DanStokes]

Keith - I thought you needed an infinite supply of grasshoppers to learn much on the road/track?

Walt - the rumor is that most of Keith's early aero tuning was accomplished by observing the spread of grasshopper guts from runs at Maxton. Then he discovered the tunnel and the rest is history.

Dan

[Fordplay0621]

I love all of the high tech talk, from grasshoppers to the Salt flats. makes me want to stick the hand out the window at 60 mph and figure out how mush downforce there is.

[std]

Scale models don't act the same as full size. You would need an EXACT duplicate of your scort to find any useful numbers.

Keith is right about his testing procdures....He seems to be a bit mistaken about the rest

[White Monster]

He seems to be a bit mistaken about the rest


Now that there is very funny, I don't care who you are !!!
:D

[greenjunk]

I would imagine its hard for the ladies to get into with someone like turk smiling down at them... ;D

[KeithTurk]

Dave... maybe I'm just not having sex right eh???


( Pretty bad when you gotta supply your own punch lines )....

K

[Fordplay0621]

The way I see it, Any kind of testing is a step forward.

I also took the approach that there are some really aerodynamic shapes in nature, thats why some of them have been around for 250 million years. Sharks and F1 cars look alot alike. Wonder why? Same thing with the Streamliners, most of the successful ones look like you know what? Sharks.

I also found that Most Sharks Teeth look like the Dorsal Fin of the Shark they came from. (That's not in any books). Just something I noticed, and now there are alot of Shark guys looking into it.

I still think Grasshoppers are the key. Good call Keith.

[98ciHemi]

Remember, I am not trying to find out what my car's cd. or downforce is in real life, I am trying to find out what changes to the car make the most difference before I step up to full scale testing. Unfortunatly, I lack the skill to make the front of my Escort look like anything from nature. It just ain't happening. There are no roads up here right now that would be safe for 70-40 coast down testing, but I will try that out in the spring. Grasshoppers are also out of the question until I get down there in June.

[DanStokes]

Walt - can't you get a few thousand 'Hoppers at a bait store and find a frozen lake? Of course, getting them to jump in front of the car at the right time might be tricky. Sort of Kamikaze for grasshoppers, I guess.

Dan

[std]

Dave... maybe I'm just not having sex right eh???


( Pretty bad when you gotta supply your own punch lines )....

K



Well Keith, maybe you should......oh, never mind

[KeithTurk]

Walt here's what I know works 99% of the time....

Lower is WAY better by a lot and a bit...

Air into the car is ALWAYS bad.... so think about how you can cover openings and remember it's only 1 mile....

Lower is WAY better by more then a lot and a bit...

Did I mention LOWER???

K

[White Monster]

OK, now that we have LOWER covered, depending on what class you want to run in, a front air dam that goes to within about 1" of the ground will keep air from traveling under the car, which prevents "lift".

[STINEY]

Walt - can't you get a few thousand 'Hoppers at a bait store and find a frozen lake? Of course, getting them to jump in front of the car at the right time might be tricky. Sort of Kamikaze for grasshoppers, I guess.

Dan


This time of year, we just substitute deer in these here parts. Rebuilding between test-rounds is rather costly though....

[DanStokes]

Are the deer stains useful?

Dan

[98ciHemi]

Up here deer use Escorts for aero testing. I have been off of the project for a short time while I am working on some Christmas gifts. I usually make at least one gift for a family member, and this time I am doing some woodworking, which is time consuming and labor intensive.

[KeithTurk]

I always make Tonya a small aluminum ornament with the date on it... usually has a Stamped holdiday greeting on it...

Good stuff... just 1/8th inch sheet cut out in a 1.5" star or cross.... tomorrow's is going to be a wreath... Should be fun...

K

[std]

I always make Tonya a small aluminum ornament with the date on it... usually has a Stamped holdiday greeting on it...

Good stuff... just 1/8th inch sheet cut out in a 1.5" star or cross.... tomorrow's is going to be a wreath... Should be fun...

K




Dave... maybe I'm just not having sex right eh???


( Pretty bad when you gotta supply your own punch lines )....

K


Good start Keith....Maybe you'll get to work on.......Oh, nevermind

[White Monster]

I always make Tonya a small aluminum ornament with the date on it... usually has a Stamped holdiday greeting on it...
Good stuff... just 1/8th inch sheet cut out in a 1.5" star or cross.... tomorrow's is going to be a wreath... Should be fun...


That is pretty cool and I'd like to see some pics of what you've done.
How about a few pics there Buckwheat ?
It is much more "from the heart" to hand make a personal present than just buying something.
Those are usually the gifts that are cherished for years to come ...
:)

[greenjunk]

This thread is getting way to feminine...

BALLLSSS!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

There thats better. ;D

Did I mention lower, waaayyyyy lower ;D

Steve, did you and the other 2 stooges figure out lower yet?

[White Monster]

Did I mention lower, waaayyyyy lower ;D
Steve, did you and the other 2 stooges figure out lower yet?


Actually, it's the other Three Stooges trying to figure out lower, I'm just the not so well known Fourth Stooge (Shemp I think).
:D

[greenjunk]

so you're the four quacks; hughie, dewie, lewie, and daffy.

[White Monster]

so you're the four quacks; hughie, dewie, lewie, and daffy.


LOL !!
Daffy Duck is my hero .. same as Goofy !!
:D

[min301]

Escorts are a bottom breather thru the radiator, IIRC,
would it be a good idea to vent that airflow,
like say raising the back of the hood slightly?

[98ciHemi]

Not quite sure what you mean min. This shows what lives behind my fascia:
http://i293.photobucket.com/albums/mm57/RoninRDS/HPIM1283.jpg

Since it is only a mile, I may just plug the grill and keep air out of the engine bay. It has an electric fan to pull air through, and I will wire that up to come on with a switch. The shroud could use some work, though. When I finish my air intake, it will draw from my cowl instead of underhood.

[min301]

Yeah, I guess those aren't.

Airflow thru the radiator should still be vented.
It could pop the hood at high speed.

[98ciHemi]

It couldn't hurt. I can add a slit or two to allow air from the bay out of my cowl vents.

[White Monster]

It could pop the hood at high speed.


That made me laugh ... thanks min !
Other than the Time Only category, hood securing devices are required for safety.
Looks like Walt has that covered with four hood pins already installed.
:D

[98ciHemi]

Question on that- the pins are all that hold the hood on. No latch or hinges anymore. I that legal and safe or do I need to change something. I didn't see anything in the rules against it.

[greenjunk]

or you could just block the grill.....
its less than 100hp it won't overheat in a mile or probably 10 miles

[DanStokes]

I know it's preferred to replace the hood latch with pins so the safety crew can easily gain access to the engine in case of an underhood fire. Not sure on the hinge end as I haven't removed mine but it seems good to me.

This raises a question - Should the hood have a handle (hook, strap, or some such) to facilitate the safety guys raising the hood quickly? I don't recall seeing anything in the book on it but it seems reasonable. Sometimes it's hard to get ahold of the edge of the hood to pull it up.

Dan

[White Monster]

Question on that- the pins are all that hold the hood on. No latch or hinges anymore. I that legal and safe or do I need to change something. I didn't see anything in the rules against it.


Rules that I see are more concerned about keeping the hood securely in place, as opposed to being able to quickly remove it. If your hood is securely fastened down, you are good. Doos not necessarily require the latch or hinges.
;)

[greenjunk]

turks camaro uses 750 twist locks, if that things on fire with the hood down, someone needs to get weenies, buns, and relish. ;D

[White Monster]

I'll bring the Ketchup and Mustard ...

[DanStokes]

All the safety guys at Bonneville carry Dutz (sp?) fastener screwdrivers for just such an issue. I secretly suspect that they also carry hot dogs, buns, marshmallows, etc. just in case.

Dan

[YELLA BRICK]

Escorts are a bottom breather thru the radiator, IIRC,
would it be a good idea to vent that airflow,
like say raising the back of the hood slightly?


Remember, the area at the base of the windshield is a high pressure area. Good for forcing air INTO the engine room but no good for EXITING air out of the engine room. Good place for intake air source ala NASCAR.
NOTE: In ORR we run in 100 plus degrees for many miles. There is a 20-30 degree air temp difference between pavement level and 24 inches off the pavement. That's why my forced air intakes are through the headlight openings instead of way down on the deck.

[98ciHemi]

This is what I have now as far as engine bay setup.
http://i293.photobucket.com/albums/mm57/RoninRDS/HPIM1665.jpg
The intake I am working on at school will start out like the one I have, but will turn backward through the seperation between the engine bay and the cowl area.

[std]

Did I mention lower, waaayyyyy lower ;D
Steve, did you and the other 2 stooges figure out lower yet?


Actually, it's the other Three Stooges trying to figure out lower, I'm just the not so well known Fourth Stooge (Shemp I think).
:D


Hang on everyone...I know about lower. There were time and money restrictions that were being delt with last year.

[KeithTurk]

I've had 3 under the hood fires .... one on the starting line with Tonya in the car.... it sucked out loud to have to remove the hood with all the 1/4 turn fasteners... but if you'll notice there is a duez fastener tool taped to the roll cage right behind the driver with painters tape... ( easy to tear off )....

Walt your escort is fine .... 4 pins works... don't need to vent it... mine's not only not vented it's Sealed!!!

K

[98ciHemi]

I'll listen to the guy with the green hats. He seems strange, but I guess strange works.

[DanStokes]

Actually, he has 'em in all colors (depends on the track). ECTA is green, B'ville is red, etc.

And yeah, I listen to him too. Although he probably doesn't think I do.

Dan

[std]

If no air gets in, no air has to get out.

Just make sure you lower your car.

[greenjunk]

leave the air intake where it is and seal the hood if its vented, it might be worth a little bit on the big end ::)

[Fordplay0621]

I close off the whole front end of the Kia when it was running, I even drove it Home with it covered up, and it sttill ran the same temp. And it was good for about 7 MPH Wrapping the Header was the biggest Gain when it came to Temps under the hood.

[98ciHemi]

Now that I have a functional temperature gauge, I will be able to start testing out how well it works on the Escort

[BangShiftChad]

1200 hp, one electric fan, no airflow through the grill, wide open for 5 miles at Bonneville, 200 degrees.

Tonya went 250 on that pass. Don't do any of that engine builder bullshit warming the engine ahead of time, etc. Start it, drive it like a rental, and see how fast it goes. Your car CAN'T overheat in a mile.

Also, have fun with the wind tunnel testing. For what you are doing, it will work perfectly Walt. I have had a lot of experience with small wind tunnel testing and if you are smart about the data, it is extremely useful. Your goals for the data are realistic and it will give you a good starting point for modifications on the car. It will not help with small things like windshield wipers on or off, but it will help with ride height, air dam or no air dam, spoilers, etc. Again, keep the changes dramatic and you'll get close.

We used small windtunnel testing in a project with GM in college. They helped spec the tunnel, and it was used in our hybrid and electric vehicle projects.

The single biggest thing you can do to go faster is to lower the car as far as possible. Slammed will be faster. It's amazing how many LSR guys don't understand this. Trust me, there are dozens of cars at Bonneville that could go 10 or more mph faster if they lowered them. Or used an air dam! Some people just don't think.

[greenjunk]

the easiest way to lower your car, think smaller tires. i run 22" tall 205 autocross tires on my car. they're z, or y rated can't rember which. BUt for getting it off and on the trailer I use a set of 26" tires, and will be going to some narrow 28's so i can "drive it around a little" ;D

[White Monster]

Bringing some relevant topics back to the top.
;)

[Fordplay0621]

It's a balancing act, and thats the fun part of all of this. Dont go to tall on the tires, you will run out of gear, and to small you just run out. Lowering and cleaning up the front, and getting the air off the back end and you will do fine. The Kia Runs better without the rear spoiler,it was making the front end raise up. and it would drift around over 100 MPH
Make the front Air Dam down as low as you can and then put a rubber strip at the bottom. Wrap the header even if its stock to cool things down, Cold air intake from the fender well or Fog light openning worked well to. Without the mirrors and wipers and closed openings you can run in the Altered Class. Dont worry about records, just have fun.

Remember most of the Advice you get are from guys running 700 HP. they usually dont have to worry about power to weight ratios like we do. we need every ounce of power we have just to keep moving. Being to heavy or to light. Yeah LSR cars are better when they are heavy for traction. but when you have 120 HP in a 2200 LBS car, that issue is just out the window. Unless you have 700 HP we dont know about.

[98ciHemi]

I am working on the scale model right now, it is coming along. I will post pics later, but right now I am just on a warm up from out doing some bodywork.

[jezzicaz789]

lmao...neat idea!

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=190343410833



Such a very amazing link!
Thank you for the post.

__________________
Watch Green Zone Online Free (http://moviesonlinefree.biz)

[Caveman]

http://autospeed.com/cms/gallery/article.html?slideshow=0&a=109778&i=9

Walt - check out the airflow on the car in the link. The strings taped to the body that are 'out straight' in the wind are 'laminar' flow.... i.e., smooth as hell. Of course, its a swoopy late year RX-7 too.... that doesn't hurt.

Look closely at the strings taped on that are waving wildly in the wind: these represent turbulent airflow, and DRAG.

You can replicate this easily with some string or thin ribbon, some bits of tape, and a couple of buddies driving alongside taking video of your car at 60-70mph. Or even 50. Then look at the video; ask them to do close ups of various points on the car. You'd be surprised how much you can learn.

But unless you are gonna chop it, do fender skirts, a full bellypan, or a massive swoopy aero hood scoop to ease the flow over the car, you'll be kinda limited on how much you can gain from just popping off the mirrors, wipers, etc.

Here's another good article, just on general production car aero stuff...
http://www.atzonline.com/index.php;do=show/site=a4e/sid=10989940534b9445c70422d319209847/alloc=35/id=147


Tony