New Product: Competition Chin Splitter
01-28-2012, 01:09 PM
#32
Developer
Thread Starter
Interesting note on relative pressures - above and below the chin splitter. We found at Bonneville that once the chin splitter got within about an inch of the ground, that last distance was easier to travel and pound the splitter into the salt than all the other inches of front end travel before it.
"Why", we wondered, especially when spring pressures are accumulative, would be pushing the nose down from 1 inch of clearance to zero be easier than say the travel between 2" and 1 inches? Said another way; why, at the very end would it suddenly get easier to bottom out just when the spring load is highest? (Not the spring rate - the spring load.)
The answer was in the relative pressures. Augmented by the complete belly pan, rear diffuser, the front-to-rear rake angle and the side skirts - we had turned the whole underside of the car into a downforce device. Intentionally. And it was working.
We found that, when the chin splitter got about a half inch off the ground, the low pressure under the chin splitter was actually sucking the chin splitter down, of course at the same time it was being pushed down from above.
That's where we had to put our suspension stops, and why we had to make them.
For more on this - the story of our 3 days at Bonneville is in this months "9 Magazine", and I describe in some detail the chin splitter hitting salt at 200 MPH.
"Why", we wondered, especially when spring pressures are accumulative, would be pushing the nose down from 1 inch of clearance to zero be easier than say the travel between 2" and 1 inches? Said another way; why, at the very end would it suddenly get easier to bottom out just when the spring load is highest? (Not the spring rate - the spring load.)
The answer was in the relative pressures. Augmented by the complete belly pan, rear diffuser, the front-to-rear rake angle and the side skirts - we had turned the whole underside of the car into a downforce device. Intentionally. And it was working.
We found that, when the chin splitter got about a half inch off the ground, the low pressure under the chin splitter was actually sucking the chin splitter down, of course at the same time it was being pushed down from above.
That's where we had to put our suspension stops, and why we had to make them.
For more on this - the story of our 3 days at Bonneville is in this months "9 Magazine", and I describe in some detail the chin splitter hitting salt at 200 MPH.
01-28-2012, 01:14 PM
#33
Developer
Thread Starter
just by stopping the air from going under the car it vastly improved engine cooling, which forces air through the radiator & then it gets sucked out the hood vent which does increase downforce a little bit.....I don't have any data to back it up, but the car handles better with it, than it did before...
01-30-2012, 01:04 PM
#35
Rennlist Member
I can send you a couple of video discs. unfortuantely at the time, I have a lot of video of crawling up Don's bumper for a couple of events, thunderhill and Lagna. (because he beat me, but had 200 more hp! 
) Now, fortunately i was crawling up Dons bumper for these events because it made for some good video!
On Carl's website, this video is there (from the PCA laguna race), but ill try and get a copy on cD for you too.
Mark
) Now, fortunately i was crawling up Dons bumper for these events because it made for some good video! On Carl's website, this video is there (from the PCA laguna race), but ill try and get a copy on cD for you too.
Mark
01-30-2012, 01:15 PM
#36
Rennlist Member
Interesting note on relative pressures - above and below the chin splitter. We found at Bonneville that once the chin splitter got within about an inch of the ground, that last distance was easier to travel and pound the splitter into the salt than all the other inches of front end travel before it.
"Why", we wondered, especially when spring pressures are accumulative, would be pushing the nose down from 1 inch of clearance to zero be easier than say the travel between 2" and 1 inches? Said another way; why, at the very end would it suddenly get easier to bottom out just when the spring load is highest? (Not the spring rate - the spring load.)
The answer was in the relative pressures. Augmented by the complete belly pan, rear diffuser, the front-to-rear rake angle and the side skirts - we had turned the whole underside of the car into a downforce device. Intentionally. And it was working.
We found that, when the chin splitter got about a half inch off the ground, the low pressure under the chin splitter was actually sucking the chin splitter down, of course at the same time it was being pushed down from above.
That's where we had to put our suspension stops, and why we had to make them.
For more on this - the story of our 3 days at Bonneville is in this months "9 Magazine", and I describe in some detail the chin splitter hitting salt at 200 MPH.
"Why", we wondered, especially when spring pressures are accumulative, would be pushing the nose down from 1 inch of clearance to zero be easier than say the travel between 2" and 1 inches? Said another way; why, at the very end would it suddenly get easier to bottom out just when the spring load is highest? (Not the spring rate - the spring load.)
The answer was in the relative pressures. Augmented by the complete belly pan, rear diffuser, the front-to-rear rake angle and the side skirts - we had turned the whole underside of the car into a downforce device. Intentionally. And it was working.
We found that, when the chin splitter got about a half inch off the ground, the low pressure under the chin splitter was actually sucking the chin splitter down, of course at the same time it was being pushed down from above.
That's where we had to put our suspension stops, and why we had to make them.
For more on this - the story of our 3 days at Bonneville is in this months "9 Magazine", and I describe in some detail the chin splitter hitting salt at 200 MPH.
. this is more than likely the reason that the ease of travel downward, happened. progressive resistance in the springs, but suddenly , the splitter , is not acting like a wing and thats not how its designed to work, but fortunately, yours is strong enoug to work like that. remember, my liittle sheet aluminum splitter is stable and strong at 135mph and still providing a lot of downforce.
Im going to do an experiment with my splitter for you. ill mount a hard mounted bar to about .5" off the ground, and mount a camera to the splitter to see how much downward travel i get with my splitter at speed. I will then tape off the splitter flush with the nose, so there is no splitter and do the test again.
How did you find that the last "1" " of travel was easier than the first inch? was that in the wind tunnel? Im sure you know the aerodynamic forces are going up with the square of speed, so small changes at speed will be huge changes in pressure and force at speed.
01-30-2012, 01:16 PM
#37
Carl, looks like a great product and great price!
01-30-2012, 01:41 PM
#38
Not the sharpest tool in the shed
Rennlist Member
Rennlist Member
I like the discourse here relative to things that represent performance improvement. The gain comes when an idea or new product is completely debated, this sometimes means taking a couple more whacks at a horse that is so dead it is beginning to decompose. That makes for the best analysis. So, Mark K. and others keep challenging the obvious.
Now for me, I think there are too many variables to state what is and what is not directly attributable to the downforce created by the splitter. Having played around with some scientific measuring equipment in the day, to include a wind tunnel, there are those who calculate with a slide rule, er, I mean software (TunnelSys) to good effect but I'm not like that. In many instances you just cannot account for the many variables that generate the end effect. I had plenty of people smarter than me calculate out a desired response, would engineer to that and when it came to the tunnel the results were poor. Too many variables, in this I agree with Mark K.'s assertion there are other forces/influences at work here that affect the downward pressure on the car.
Carl used a pressure measuring device under the front wheels to indicate the increased down force. That is good but does not necessarily represent the other contributions to the down force, such as the general aerodynamic result of the car at wind speed.
How I would have tested the efficacy of the splitter. I would have put pressure measuring devices under all four wheels. Would have made a few runs at different speeds on the stock car (prior to modifications) in order to get a baseline of the aerodynamic down force effects of that configuration. From there you add on the components incrementally with a few wind tunnel runs in between to measure the true contributing factors. Once you optimize the chin splitter, add a rear wing and start all over. It's just damn hard to account for all variables by mathematical means. Especially for use in this community. If it were possible, well, then, there would be no need for wind tunnels.
I used to practice brute force science, was forced to learn how to use a K&E slide rule by my bosses who had no appreciation or trust of my HP41c or TI-59. It was fun.
There is lots of evidence of the value of chin splitters, just not sure the 300lb downforce claim is wholly attributed to Carl's design.
Now for me, I think there are too many variables to state what is and what is not directly attributable to the downforce created by the splitter. Having played around with some scientific measuring equipment in the day, to include a wind tunnel, there are those who calculate with a slide rule, er, I mean software (TunnelSys) to good effect but I'm not like that. In many instances you just cannot account for the many variables that generate the end effect. I had plenty of people smarter than me calculate out a desired response, would engineer to that and when it came to the tunnel the results were poor. Too many variables, in this I agree with Mark K.'s assertion there are other forces/influences at work here that affect the downward pressure on the car.
Carl used a pressure measuring device under the front wheels to indicate the increased down force. That is good but does not necessarily represent the other contributions to the down force, such as the general aerodynamic result of the car at wind speed.
How I would have tested the efficacy of the splitter. I would have put pressure measuring devices under all four wheels. Would have made a few runs at different speeds on the stock car (prior to modifications) in order to get a baseline of the aerodynamic down force effects of that configuration. From there you add on the components incrementally with a few wind tunnel runs in between to measure the true contributing factors. Once you optimize the chin splitter, add a rear wing and start all over. It's just damn hard to account for all variables by mathematical means. Especially for use in this community. If it were possible, well, then, there would be no need for wind tunnels.
I used to practice brute force science, was forced to learn how to use a K&E slide rule by my bosses who had no appreciation or trust of my HP41c or TI-59. It was fun.
There is lots of evidence of the value of chin splitters, just not sure the 300lb downforce claim is wholly attributed to Carl's design.
01-30-2012, 01:50 PM
#39
Rennlist Member
Umm like if anyone mentions gearing, track aerodynamics, and HP and torque. No mater what anyone puts forward on these topics, you always disagree. Carl's product was designed in a WIND TUNNEL and designed to be effective with the added bonus of flipping up for loading.
Carl, looks like a great product and great price!
Carl, looks like a great product and great price!
Carls product was not "designed in the wind tunnel" it was verified. he calibrate the downforce that it created in concert with the other mods. the fliping up part could be very dangerous in a race condition, because if you ever were bump drafting off your compeitor, you could have it flip up, create LIFT and you could loose control and die.
. i would personally , pin that feature.not to digress. i was challenging Carl on the assesment , not design besides the cross members that restrict flow to the sides ,as where the air does travel, and the basis of the splitter concept. it stiill works, but would work better due too that fact. (plus look better) .
It seems you have discounted reality of my testing on the street and track, sucessfully i might add. there is a reason that the top race car and team in the country , producing a GT3 porsche race car, driven by a pro, 20 years newer, is behind me in the picture ini the avitar
oh yeah, im just lucky, thats right.
01-30-2012, 02:22 PM
#41
Rennlist Member
I like the discourse here relative to things that represent performance improvement. The gain comes when an idea or new product is completely debated, this sometimes means taking a couple more whacks at a horse that is so dead it is beginning to decompose. That makes for the best analysis. So, Mark K. and others keep challenging the obvious.
Now for me, I think there are too many variables to state what is and what is not directly attributable to the downforce created by the splitter. Having played around with some scientific measuring equipment in the day, to include a wind tunnel, there are those who calculate with a slide rule, er, I mean software (TunnelSys) to good effect but I'm not like that. In many instances you just cannot account for the many variables that generate the end effect. I had plenty of people smarter than me calculate out a desired response, would engineer to that and when it came to the tunnel the results were poor. Too many variables, in this I agree with Mark K.'s assertion there are other forces/influences at work here that affect the downward pressure on the car.
Carl used a pressure measuring device under the front wheels to indicate the increased down force. That is good but does not necessarily represent the other contributions to the down force, such as the general aerodynamic result of the car at wind speed.
How I would have tested the efficacy of the splitter. I would have put pressure measuring devices under all four wheels. Would have made a few runs at different speeds on the stock car (prior to modifications) in order to get a baseline of the aerodynamic down force effects of that configuration. From there you add on the components incrementally with a few wind tunnel runs in between to measure the true contributing factors. Once you optimize the chin splitter, add a rear wing and start all over. It's just damn hard to account for all variables by mathematical means. Especially for use in this community. If it were possible, well, then, there would be no need for wind tunnels.
I used to practice brute force science, was forced to learn how to use a K&E slide rule by my bosses who had no appreciation or trust of my HP41c or TI-59. It was fun.
There is lots of evidence of the value of chin splitters, just not sure the 300lb downforce claim is wholly attributed to Carl's design.
Now for me, I think there are too many variables to state what is and what is not directly attributable to the downforce created by the splitter. Having played around with some scientific measuring equipment in the day, to include a wind tunnel, there are those who calculate with a slide rule, er, I mean software (TunnelSys) to good effect but I'm not like that. In many instances you just cannot account for the many variables that generate the end effect. I had plenty of people smarter than me calculate out a desired response, would engineer to that and when it came to the tunnel the results were poor. Too many variables, in this I agree with Mark K.'s assertion there are other forces/influences at work here that affect the downward pressure on the car.
Carl used a pressure measuring device under the front wheels to indicate the increased down force. That is good but does not necessarily represent the other contributions to the down force, such as the general aerodynamic result of the car at wind speed.
How I would have tested the efficacy of the splitter. I would have put pressure measuring devices under all four wheels. Would have made a few runs at different speeds on the stock car (prior to modifications) in order to get a baseline of the aerodynamic down force effects of that configuration. From there you add on the components incrementally with a few wind tunnel runs in between to measure the true contributing factors. Once you optimize the chin splitter, add a rear wing and start all over. It's just damn hard to account for all variables by mathematical means. Especially for use in this community. If it were possible, well, then, there would be no need for wind tunnels.
I used to practice brute force science, was forced to learn how to use a K&E slide rule by my bosses who had no appreciation or trust of my HP41c or TI-59. It was fun.
There is lots of evidence of the value of chin splitters, just not sure the 300lb downforce claim is wholly attributed to Carl's design.
one thing about the splitter end results and forces, is that when i mounted my splitter, a size very close if not bigger than Carls, i measured actual air pressure in that area with a very sensitve pressure measureing device. (that was in my line of work, if you know my background).
the splitter is just that , a splitter. air that is already going under the car, its still ambient. the nose of the car is splitting the air as well. over or down goes the air hitting the nose. the air that goes down, goes under the car, unless it enters the radiator inlet. sure if the air goes under the car, it will have to speed up (venturi effect) and pressure can (Not always) . thats another discussion.
But, with a splitter, this air that is heading down from the nose, is litterally pressure trapped by the splitter the pressure front, increases to a big bulge in front of the radiator inlet , and the excess air is routed to the sides. the flatter the nose ,the larger splitter you need. those brackets Carl has holding the splitter up are way too beefy and disrupt this flow. the air should have a clear path side to side from the nose, because thats how it works. how much of a difference?? probably not a big deal, i agree. but it would look a lot better if the brakets were hollowed out so you had no "matter cage" look to them.
then, it was to my next point is that the brackets could be carved out, because the 500lbs of downforce is not all on the splitter itself. its different than a wing in the rear, its a splitter. the differnetial pressure is not what gives the splitter its downfoce effects , its the "splitting" of the air that goes under the car and to the sides. further enhanced by what Brian said, with the hood vents, the air that now travels into the radiator , and normally vented under the car , increasing pressure underneath, and creating lift, is now vented to the top of the car, neutralizing the low pressure zone in the middle of the hood area (as shown by the pressure graphs we have all seen of the 928 aero engineering plots).
So, the pressuree i measured. *(just as valuable as the wind tunnel wheel force measurments that carl saw) is .22psi at 130mph and around .11psi at 80mph. (very close to prediction using air flow flat plate pressure theory)
i just measured my splitter. its 6" old one was 8", and the width of the splitter is 48". do the quick math. 288 sq in, x .11psi, is a total force distributed grossly unevenly over the splitter of 30lbs!! 30lbs!!!!!!! if carl is measuring 100 to 300lbs of downfoce at 80mph, its coming from the effects of the "splitter effects" , not the pressure on the splitter. THIS is why i can have the same function as cars, using something paper thin, and rinkydink as 1/6" aluminum from home depot, or old 928 fender aluminum and a couple of cable supports. you dont need to stand on the splitter. now, who will survive a crash better? im sure both will be a messs with any contact.
01-30-2012, 02:38 PM
#42
Rennlist Member
im just saying.
the orange one (in the other avitar) started out ahead as well. thats an RSR, with a now sucessful pirelli cup diver at the wheel, who ive raced before when he had a hot vintage mustang many years ago.Point is all us that race, are racing cars that have similar lap times where the advantage is subtle in cars and driver. Point is, we have a xxx-Box 928 running door to door with these incredible cars for a fraction of the cost and fuss. (and i drove mine home too! )
again, just saying.
01-30-2012, 02:43 PM
#43
Rennlist Member
Ed, Here is the link to Carls web page with videos.
scroll down to the PCA laguna race, as well as I think the PCA Sears point race is a good one too against Don's beast.
http://www.928motorsports.com/othervideos.php
scroll down to the PCA laguna race, as well as I think the PCA Sears point race is a good one too against Don's beast.
http://www.928motorsports.com/othervideos.php
01-30-2012, 02:44 PM
#44
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He was holding me up, thats why it took me 30mins to get around him.
im just saying. the orange one (in the other avitar) started out ahead as well. thats an RSR, with a now sucessful pirelli cup diver at the wheel, who ive raced before when he had a hot vintage mustang many years ago.
Point is all us that race, are racing cars that have similar lap times where the advantage is subtle in cars and driver. Point is, we have a xxx-Box 928 running door to door with these incredible cars for a fraction of the cost and fuss. (and i drove mine home too! )
again, just saying.
im just saying.
the orange one (in the other avitar) started out ahead as well. thats an RSR, with a now sucessful pirelli cup diver at the wheel, who ive raced before when he had a hot vintage mustang many years ago.Point is all us that race, are racing cars that have similar lap times where the advantage is subtle in cars and driver. Point is, we have a xxx-Box 928 running door to door with these incredible cars for a fraction of the cost and fuss. (and i drove mine home too! )
again, just saying.