Mr.E.G.

calm down turbo


this thread wasnt going anywhere for a month or better so i didnt expect to find any new replys so quickly.

also, if i go forward with this explanation i would appreciate it if you naysayers would think objectively about this. im no expert, im only a creative guys who has read and read and read and experimented and experimented and experimented. i dont claim to know it all, but i do feel that i have come along way and accomplished a good deal more than most amatuers so pretty please with sugar on top dont break my *****, and respect my work.

ok i can explain my testing methods, but i kind of dont want to since i have spent a lot of ******* time perfecting homemade aerodynamic testing devices and as much as i would like to help it kind of sucks to have my ideas "borrowed" from. ahh, expletive it... here is an example o one of my methods.

i isolate each component individually, and to keep things realistic and simple for me i dont quantify the data except to quantify the amount of change. so for example i cant tell you an exact amount of how much downforce any of the wings i have built are making but i can tell you how much change they have applied to the vehicle.

here is one test that i have done.

i made a wing and i wanted to dial it in for the best combination of downforce and drag. i started with some baseline tests.

aerodynamic changes to the chassis act upon the suspension. i found a brand new extremely smooth road in a new subdivision that was being built. it was long and as about as perfect as you can get without being on a race track. i wrapped zip ties around the rod of my dampers. i made a starting point and an ending point for my "track". i decided to test at speeds of 60 mph then 80 then 100 then 120. so i would start at the beginning of the street and slowly accelerate as to avoid compressing the suspension as much as possible. i drove until i got to 60 mph and then i held it there. from my starting pint to my ending point. i slowly decelerated as to avoid compressing the suspension and i got out and measured. my zipties had moxed x amount up the length of the shaft as the shaft was driven into the damper body. i did my basline run three times at all of the different speed and since the road was pretty freaking smooth there was very little difference between the measurements which was a good sign.

so now that i knew what type of suspension compression to expect as a result of aerodynamic load at various speeds. the tricky part was that as i did the 120 mph test the zip tie didnt slide up the shaft at all as the car was experiencing a noticable amount of lift. i came up with a trick to measure lift using this same method, but i didnt impliment it since i could use the amount of change that resulted from the lower speed tests and get a pretty good idea of what was happening at 120. also, it didnt really matter to me excatly what the exact amount of change was as i knew that i could at least eliminate that lift even if i couldnt make a lot of downforce (i ended up doing both)

now here is the good part. i riged up a mount for the wing that moved in two directions. vertically and longitudinally. i dont want to share the exact specifics of my design, but if you spend some time guessing it wont be hard to imagine how it was done. the vertical movement was regulated by a piston type setup that was very similar to your cars suspension. there was a spring and a "damper" type device, only the damper wasnt there to actually dampen anything. it was more of a guide to control the movement.

so basically we are talking about wing mounts that allow vertical sliding comletely perpendicular to the ground (in theory) the spring was not a suspension spring obviously but rather it was a pull type spring that i got from ace hardware that i beleive is used for screen doors. it was mounted in such a way that as the air forced down on the wing (generating downforce) the spring was pulled against. so it was actually the exact opposite of the way that your car suspension works.

i used zip ties on the "rod" of this system and i conducted speeds at various speeds and various angles of attack until i determined a good range of angles that delivered a spectrum of downforce levels (as indicatied my the travel of the zip tie, just like my baseline suspension tests) i charted all of my results in a notepad all along the way.

but this still didnt answer the question of drag. well i had constructed my mount assembly to slide on rails longitudinally. i locked this part in place when i was downforce testing, and i locked the vertical travel if the mount when i was drag testing, naturally.

the forward and back motion was regulated by a pull type spring very similarly as the other test.

i couldnt use a zip ties due to the shape of the rail so i used an "L" bracket on the lower portion of the driver side vertical support of the wing and i attached a grease pencil to it. the grease pencil would draw a line on the roof of the car that i could wipe right off after i recorded the results from each test. i would set the angle of attack of the wing and then drive to reach my testing speed. the drag would force the wing back on the rails and it would slide. as it slid the grease pen would draw a line to show the distance that it had moved. i recorded the movement that resulted from various angles of attack.

i sat down with my paper and observed all of the data over lunch. i found the angle of attack that had the best compromise of downforce and drag.

i secured the wing with a "real" mount and i dialed in that angle of attack.

i then redid the suspension compression test at the various speeds and the suspension was compressing considerably further than it had been before. SUCCESS!

there were a few anomalies to the data that i blame on wind (which there was very very little of) and road irregularities but for the most part it was very straight forward and nothing too unexpected. the wing was very effective... to the point that uprgrading or at least retuning the suspension would have been neccessary had the wing been inteded to stay there.

there were a few more things i tested but that was the meat and potatoes of it. it took all freaking day, but i learned a TON.

i have tested various other devices but i dont wish to share that information. one day i plan on making a huge thread on all of my homemade aerodynamic experiments and i dont plan on hoarding my accumulated knowledge, i just want to get teh credit i deserve and if i slowly leak it i dont think that will happen.

did that answer your question?

Mr.E.G.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by kb58 &raquo;</TD></TR><TR><TD CLASS="quote">

Real testing will be to monitor shock absorber travel over speed to get an idea of lift/downforce.
</TD></TR></TABLE>


dammit, you beat me to it.


your car is so ******* awesome. obviously you have a slightly easier platform to work with in terms of developing an underbody, but i think you clearly illustrate what is capable of being made "at home"

Mr.E.G.

also to answer you guys questions more simply, no i dont use lap times or the butt dyno to quantify and of the changes that my home made aerodynamic parts make.

kb58

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mr.E.G. &raquo;</TD></TR><TR><TD CLASS="quote">...i dont use lap times ...</TD></TR></TABLE>

But when it's all said and done, is't that the only thing that matters?

Mr.E.G.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by kb58 &raquo;</TD></TR><TR><TD CLASS="quote">But when it's all said and done, is't that the only thing that matters?</TD></TR></TABLE>

my goal is increased lap times, sure, but they are unreliable as a means of testing how effective my design is.

but lap times are very subjective. if you just happene to drive slightly better on one lap versus another there could be a difference in times and it may have absoluetely nothing to do with whether or not you actually made any signifcant improvements to your vehicle by means of aerodynamic enhancement.

perhaps a better explanaition would be to say that I am not a good enough driver to deliver lap times that are so consistent that i could use lap times to quantify the result of my design.

if you've read Katz and McBeath you should know that lap times arnt the best way to test they both say so.

so maybe i didnt make myself clear, and for that i appologize. to reiterate, yes lap times ar importnat and thats really the over all goal, but i dont choose to use lap times so determine the effectiveness of my design.

my testing, i feel, is pretty accurate

RandomNeeha

ive been thinking more about making sure i have the air run through my engine bay and fire down off the firewall. So i was thinking about making a cooling plate and an underbelly right to the front of the tranny with lip down to pull air through the dam in the bumber and under the car to foil around to cool the tranny and exhaust heat. By the way its a Del Sol

k24em2

You mean Mr. EG doesn't have his very own wind tunnel and has to use the butt dyno?!?!

haha...engineering stuff like back in the 1930s!

CaymanDragR

Thought this thread deserved a bump. Classic artwork too!

xzodiackillerx

let the air exit the front wheel area. this will help cool the brakes and let the air go someplace other than under the car ..

MoiMotorsports

Me workin on the belly pan