ThinkFast Engineering LLC is a motorsports engineering consulting service led by Neil Roberts, a 30 year veteran of both amateur and professional auto racing. From autocross to Indy, and everything in between, TFE has the know-how to help you win.
The ThinkFast Engineering web site http://thinkfastengineering.com/ shows TFE's experience and expertise, past projects, consulting services description, contact info, the FastBits by TFE product line, and a blog with progress updates on the current TFE projects that can be discussed.
TFE will guide you toward your goals within your budget. Whether you need advice on one specific problem, occasional guidance when complicated things pop up, overall program development, designing a new body for your car, a clean-sheet race car design, or something completely new that has never been done before, TFE knows how to help you succeed. Contact TFE and tell us about your problems and your goals, and we will guide you toward victory.
Thanks Neil, that was a great read! I can hardly wait to put it to practice at my next autocross with my new (to me) formula enterprise.. Although I'll be limited to checking temps right after the run. Just don't have $1000 or more to spend on collecting this data "real time" !!
That was a great read. Thanks for taking the time to write about the technology used as well as how you use it to tune the car. Special thanks for actually showing us the data! I wish more "tech" had this much information.
Your blog states that you don't feel like a gold contender at the Solo Nats this year so you may not attend. A "get acquainted" visit to Nats might be a good idea prior to feeling you are a gold contender. You "need" to see how quick the top CM drivers (and maybe the "not so quicks ) that ran at Peru last weekend really are and the whole Nationals experience is like no other autocross you have ever attended. Personally I stopped being a gold contender many years ago so we can compare with each other if you really aren't faster than you admit.
FYI: I've been doing mild versions of the "solar roll" for 20 years in the paddock and sometimes on the grid. Also, relative tire heating hints can be seen on the tread surface after all runs and on tire pressure build up after initial runs before pressures stabilize.
Do you know what the optimum operating temperatures are for the DOT R tire rubber and/or the expansion joint tar that we will pick up and will coat our front slicks after each run?
You "need" to see how quick the top CM drivers ... really are.
In my last go-around in 1995-6, I competed with Tommy Saunders, Stuart Lumpkin, and Bruce Dickey on a regular basis. Now that's a tough crowd! If not for a cone, I would have won a divisional against them, but most of the time they were just out of reach.
In my last go-around in 1995-6, I competed with Tommy Saunders, Stuart Lumpkin, and Bruce Dickey on a regular basis. Now that's a tough crowd! If not for a cone, I would have won a divisional against them, but most of the time they were just out of reach.
Me too at Nationals and Pro Solos. Some of the "new guys" may be even quicker.
Do you think this is a sensor bracket that would be allowed during road racing events on open wheel cars?
I sure hope so! I plan to run them for test days, practice sessions, and qualifying sessions, but I'll take them off for races. I painted mine red and yellow to make them as visible as possible.
Last edited by Neil_Roberts; August 8th, 2012 at 3:26 PM.
Reason: clarity
That was very interesting data to see along with your great analysis.
Can the suspension be tuned so that inside tires are doing more work to help improve cornering ability of car?
I have an FC that I have been autoxing for the past 1 1/2 years, and hopefully, I can do some HPDE events here in Texas in the near future. I am running 13.5 lbs F and 14 on the back so that infrared temps across the tread are close but, I keep seeing higher temps on the inside so I definitely need to take out a bit of neg camber front and back. I have very stiff springs so I dont need the -1 1/2 deg in front. I will try to make some adjustments before my next event this weekend.
Thanks for the excellent info! BTW, your book was a great read and there are several very informative points I am mentioning to my racing buddies.
Great read - but I am biased. I have known Neil a long time. I have watched him autocross and race - both extremely well. Especially once he got his equipment dialed in.
He always undersells his driving - as do most good drivers. How do I know he is good, I have been there and done that on the racetrack with him and also at solo events. I did win a National tour in CM over Bruce, Stewart, Tommy and Peter Raymond back in the day. Made it onto the cover of North American Pylon and the whole deal - Neil was advising me back then - circa 1994 I believe.
Neil knows what it takes - yes, practice on a given course always help - especially related to the surface and the aforementioned rubber pickup issues, but knowning the level of competition that is expected would be zero surprise.
Jay
__________________
Sportsracer Challenge
Messenger Racing
Muleshoe, Texas USA http://thinkfastbook.com/
There are several ways to make better use of the inside tires:
Lower the center of gravity of the car
Add aerodynamic downforce
Camber the tires toward the turn center
Set the toe angles so that each tire operates at the slip angle for peak grip for its particular cornering conditions
Run a softer tire compound and a tire construction that is optimized for lower loads on the inside tires
Drive where the banking is steeper
Set the rear toe angles to achieve the best compromise between inside wheelspin and power oversteer
Of course oval track racers do the first six of those things, and since they usually run spools, inside wheelspin isn't a problem. Staggered rear tire diameters are only distantly related to making better use of the inside tires.
Would you be able to XY plot tire temperature vs lateral acceleration, and tire temperature vs longitudinal acceleration?
Of course! I looked at that, but since the results were entirely predictable, I didn't include them in the original post. I'm sure you aren't the only one interested in this trend, so here is an update with those graphs.
1) Do you know whether or not the ultimate grip of different race tire compounds (i.e. 25B, 35B, etc.) is the same when they are in their individual design operating temperature range? It seems, for example, that in F1 and Cart that the "softer" compound is frequently (but not always for all teams) significantly faster than the "harder" compound. When they are not it seems that the "explanation" is that the team/driver cannot get the balance right or the car to "work" on the soft compound. Any thoughts?
2) Given the nature of autocross and also other racing with the tire temp changing constantly to you have any feel/data for how much the grip is dependent on the temperature versus how much the temperature is the result of how "hard" the driver is working the tire due to the course/track elements? I couldn't find the reference but many years ago someone such as Paul Van Valkenburgh published some oval track tire temp data that showed huge changes in tire temp in a corner. Of course we've all seen this on TV shots of tires in F1 also. Obviously as drivers we experience lack of grip with cold tires (or too hot tires) but once we get into a decent temp range then what?
3) How do you minimize rubber deterioration between autocrosses assuming UV, "evaporation of the good stuff" and "curing" during long tows on an open trailer in hot weather are a concern?
Thanks for the extra information. Indeed there is a trend towards more grip as the tire temperature increases. It would be interesting to show a longer run and potentially identify the surface temperature limit of the tires.
On a slightly different note, there's a few different opinions on the benefits of swerving the car during a warm up lap to increase tire temperature. I've heard some say the swerves are not long enough to build any temperature in the tire, hence the technique is useless. When I was gokarting it was forbidden to swerve, supposedly there was no benefit to the technique.
On the other side, of the believers of the method, there seem to be a split between those who think you have to swerve in quick sharp turns (since supposedly tires warm faster than they cool, this can actually be seen on your graphs). The other side think you have to heavily load the tires for them to generate any substantial amount of temperature, hence long type swerves.
I can see how a sensor setup like your could provide great information on this.
So far the only data I have on a warm up lap is lateral acceleration plotted in time. Over several swerves I can see a slight increase in maximum lateral G, but at this point I am not sure it is tire or driver's confidence related.
The difference I'm seeing is half to the min/max you are displaying on the temperature vs lateral G plot, that is 0.1G constant. 0.1G roughly corresponds to a 25F raise on your graph. I think I could see how this temperature increase would be attainable on a warm up lap, but the G difference I'm observing is rather small (though this is the average increase) again I am not sure the lateral G improvement is hardware or driver induced.
Jean
Quote:
Originally Posted by Neil_Roberts
Of course! I looked at that, but since the results were entirely predictable, I didn't include them in the original post. I'm sure you aren't the only one interested in this trend, so here is an update with those graphs.
__________________
----------------------------
Jean-Sebastien Stoezel
Western Canada Motorsport Association (WCMA)
FV #0
Dang it, doesn't seem like we can edit posts anymore!
Based on the data you are showing it looks like the best way to warm up tires is heavy braking, though it might not be the best thing to do on a warm up lap.
__________________
----------------------------
Jean-Sebastien Stoezel
Western Canada Motorsport Association (WCMA)
FV #0
1) Do you know whether or not the ultimate grip of different race tire compounds (i.e. 25B, 35B, etc.) is the same when they are in their individual design operating temperature range?
Just guessing here, but I'd say that in general a softer compound will have a higher grip limit, but for a shorter number of laps / runs. The current Pirelli F1 soft tires are intentionally designed to go off after a handful of laps. It's likely that when the soft tire isn't as fast as the harder one that the conditions are such that the softer tire is overheated.
Quote:
Originally Posted by Dick R.
2) Given the nature of autocross and also other racing with the tire temp changing constantly to you have any feel/data for how much the grip is dependent on the temperature versus how much the temperature is the result of how "hard" the driver is working the tire due to the course/track elements?
Which came first, the chicken or the egg? In this case, I'd say that the sequence of events is 1) driver action causes tire slip 2) tire temp increases due to slip 3) grip increases due to heating or decreases due to overheating. As I said in Think Fast, the driver doesn't have direct control of grip. We do have direct control of slip and weight transfer, and the resulting grip depends on those things plus several other factors that we don't have direct control over, like tire temperature, downforce, banking, pavement changes, suspension motion, etc.
Quote:
Originally Posted by Dick R.
I couldn't find the reference but many years ago someone such as Paul Van Valkenburgh published some oval track tire temp data that showed huge changes in tire temp in a corner. Of course we've all seen this on TV shots of tires in F1 also. Obviously as drivers we experience lack of grip with cold tires (or too hot tires) but once we get into a decent temp range then what?
I'm really surprised that my tire temps didn't respond more strongly to slip. That's probably because the nature of the course limited the duration of right hand turns, so the sensors mounted on the left side of the car didn't see much heating because the thermal mass of the tires is high for the weight of the car in autocross conditions. I'm running road course events on the first two weekends in September at Buttonwillow, so I'll have a lot more to report after that.
Because surface temps in long corners increase dramatically while grip usually doesn't change much, I'm guessing that the lateral accel vs temp graph will show a broad, soft peak. So, the tires will work best over a fairly broad range of temps rather than one specific temp.
Quote:
Originally Posted by Dick R.
3) How do you minimize rubber deterioration between autocrosses assuming UV, "evaporation of the good stuff" and "curing" during long tows on an open trailer in hot weather are a concern?
I have never done much to try to preserve tires between events. If I had a basement, I would probably store tires there. The obvious solution to open trailering is tow tires.
Last edited by Neil_Roberts; August 10th, 2012 at 10:23 AM.
Reason: punctuation
FYI since tow tires are not practical with our towing setup I use a combination of black pallet wrap (very popular with autocrossers) and white RV/Trailer tire covers for my multi-day long tows. The pallet wrap is the "norm" in the Midwest and East for autocrossers with or without enclosed trailers.
there's a few different opinions on the benefits of swerving the car during a warm up lap to increase tire temperature.
Paul Haney and I got into a heated discussion about this. He stated that swerving was only good for cleaning the tires, and didn't heat them at all, quoting some French tire engineer. Having actually done it myself many times and felt the grip come in every time, I tried to point out the obvious nonsense in his position, but I didn't get anywhere with him.
You do have to really work at it, of course. Minor wiggles won't do it - it takes sustained hard cornering, using most of the track width to produce enough g's and keep your down-track speed below the pace car. When the tires come in, I will use one swerve to do a brake bias check - while cornering with constant throttle and steering, adding braking shouldn't change the balance. The end that slides more when braking is added has too much brake bias.
The way to keep that tire heat while the grid forms and tightens up for the start is to drag the brakes against full throttle. The drag from the front tires is balanced by equal and opposite thrust from the rears, so all four tires and the brakes are heated, and it helps get the oil and water up to temp as well. Dragging the brakes may be even more effective at tire heating than swerving is. It also helps scrub off some of the marbles that you will pick up from having to drive off-line because of the rolling grid.
The way to keep that tire heat while the grid forms and tightens up for the start is to drag the brakes against full throttle.
I wonder how much of this can be done between grid and start at a typical autocross . . .
I've traditionally dragged my brakes (street compound) simply to make sure the pads are not stone cold and to clean off any rust from overnight or towing rain.
Watching the F1, etc. drivers on their recon lap certainly shows some pretty aggressive swerving/power/braking even though the tires have been in tire heaters prior to the lap. Apparently per all the driver and commentator statements the F1 tires have a very narrow sweet spot for tread, carcass, and air pressure even with use of nitrogen or whatever gas to minimize pressure change.
Paul Haney and I got into a heated discussion about this. He stated that swerving was only good for cleaning the tires, and didn't heat them at all, quoting some French tire engineer. Having actually done it myself many times and felt the grip come in every time, I tried to point out the obvious nonsense in his position, but I didn't get anywhere with him.
You do have to really work at it, of course. Minor wiggles won't do it - it takes sustained hard cornering, using most of the track width to produce enough g's and keep your down-track speed below the pace car. When the tires come in, I will use one swerve to do a brake bias check - while cornering with constant throttle and steering, adding braking shouldn't change the balance. The end that slides more when braking is added has too much brake bias.
The way to keep that tire heat while the grid forms and tightens up for the start is to drag the brakes against full throttle. The drag from the front tires is balanced by equal and opposite thrust from the rears, so all four tires and the brakes are heated, and it helps get the oil and water up to temp as well. Dragging the brakes may be even more effective at tire heating than swerving is. It also helps scrub off some of the marbles that you will pick up from having to drive off-line because of the rolling grid.
Translating surface temp (IE your IR reading) is part of the picture when warming tires as you are only seeing the heat created on the outside surface. Tire warming is about building Core heat and critical to building a consistent grip in the tire.
Some years ago we attempted tests at the best way to build pre race tire temp using 12 IR sensors and internal tire pressure/air temp. This involved scrubbing (lateral), braking and small burnouts. Individually used each had it's own result with the least effect on surface temp, lateral scrubbing. The biggest effect was braking heat, at least on internal temps.
The brake heat heats the wheel and radiates to the inside air temp, which is why it's effective.
Using all three together provided the fastest climb to tire temp both inside and outside. A scrubbing technique like this..... brake, turn (scrub) while braking, throttle at end of scrub with no brake...repeat in other direction. CARE must be taken on cold tires as you can spin the car very easily using this. The fronts typically will heat up faster than the rears using this technique even on rear engine cars, so once you feel the fronts respond, you beat up the rears with more aggression of the throttle on the way out of the scrub.
BTW, all of this on the "clean" section of the track, IE the racing line. IMHO
Neil, out of interest what sampling rate are you using? The signal looks very digital and appears to be at a low level.... Most tire temp testing I've done was at 50hz-100hz each for the IR's. Internal tire temps @ 25hz..
__________________
George Main
SpeedSense consulting
George, thanks for the writeup of results from an extensively instrumented test car. Very interesting! There must be enough data there to base an SAE technical paper on it.
Quote:
Originally Posted by George Main
Out of interest what sampling rate are you using?
The logging rate was 100 Hz. But as I discovered, the update rate of the sensor processor is only about 3 Hz. That's one down side to inexpensive sensors. The data sheet states "Response time 500 ms", which would be 2 Hz. The data sheet shows the same stair-step output. Of course each sensor updates at a different time, so the stairsteps don't line up between any two sensors.
Neil, you mention that with optimal camber the inside and outside temperatures would be the same. I've always read that the inside should be 10-20° hotter than the outside, to provide some camber thrust.
Neil, you mention that with optimal camber the inside and outside temperatures would be the same. I've always read that the inside should be 10-20° hotter than the outside, to provide some camber thrust.
It's typical to target a temp spread with the inside hotter, but that applies to needle probe temps which measure the work that the tread did over most of the in lap. In that case, the inside should be hotter because the usual static negative camber works the inside of the tread when it's the inside tire in a corner, and the outboard portion of the inside tire doesn't even touch the track. It's that phenomenon, not camber thrust, that moves the optimum needle probe temps toward hotter inside.
For real time IR temps, I believe that uniform temps across the outside tire while cornering are the target. If that's not the case, then please educate me as to why.
It's typical to target a temp spread with the inside hotter, but that applies to needle probe temps which measure the work that the tread did over most of the in lap. In that case, the inside should be hotter because the usual static negative camber works the inside of the tread when it's the inside tire in a corner, and the outboard portion of the inside tire doesn't even touch the track. It's that phenomenon, not camber thrust, that moves the optimum needle probe temps toward hotter inside.
For real time IR temps, I believe that uniform temps across the outside tire while cornering are the target. If that's not the case, then please educate me as to why.
I would add that on the straightaways you will see a rise in temp due to camber as well, IMHO due to car riding on the inside edges of the tire from the camber....
__________________
George Main
SpeedSense consulting
I would add that on the straightaways you will see a rise in temp due to camber as well, IMHO due to car riding on the inside edges of the tire from the camber....
Would inside temps at the front be higher not only from negative camber, but also from running toe-out?
__________________ "Driving a Lotus is a triumph of bravery over intelligence." Stirling Moss
Would inside temps at the front be higher not only from negative camber, but also from running toe-out?
On the straights, perhaps. Negative camber produces some camber thrust that makes both tires on that axle push toward the middle of the car. Toe out reduces that effect, so it depends on the magnitudes of camber, toe, and the slope of the camber thrust vs camber angle graph.
General Classifieds
ThinkFast Engineering
) that ran at Peru last weekend really are and the whole Nationals experience is like no other autocross you have ever attended. Personally I stopped being a gold contender many years ago so we can compare with each other if you really aren't faster than you admit. 
In this case, I'd say that the sequence of events is 1) driver action causes tire slip 2) tire temp increases due to slip 3) grip increases due to heating or decreases due to overheating. As I said in 
