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06-08-2020, 04:03 PM | #155 | |||
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06-08-2020, 04:12 PM | #156 | ||||
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06-08-2020, 05:58 PM | #157 |
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Do you have a math channel for slip angle yet?
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06-08-2020, 07:07 PM | #159 |
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It's a little tricky, but here goes. Credit goes to Precision AutoResearch for providing these in a seminar a few years ago. Understeer = (WheelAngle-RadiusAngle)/LatG The output is in "deg/g". RadiusAngle is measured in degrees, and LatG is measured in g. A negative value indicates oversteer and a positive value indicates understeer. As you can see, you have to do two nested formulas: Wheel angle = Steer/SRatio The output is in degrees. SRatio is the steering rack ratio. A negative value indicates left and positive value indicates right. The wheel angle is telling you how far the front wheels are turned for any steering wheel input. Radius angle = 57.3*(wheelbase/12)/CornerRadius This is also called the Ackerman angle. The output is in degrees. Wheelbase units are INCHES and corner radius units are FEET. Negative values are left, positive values are right. This formula is telling us the nominal angle the front wheels have to be turned for a given radius.
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06-08-2020, 07:25 PM | #160 | |
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06-08-2020, 07:31 PM | #161 | ||
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Dan - do you have an example of how you've done this for MSRC ? |
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06-08-2020, 08:43 PM | #162 | |
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It's no different than a skidpad. Radius = (velocity^2 / acceleration) I had to Google it for AIM since I don't have their software, so I think it's this: abs(1/(GPS_Speed*MPH2FTS)^2/(GPS_LatAcc*32.2)
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06-08-2020, 09:07 PM | #163 |
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06-08-2020, 09:20 PM | #164 | |
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Here it is in Pi Toolbox as I'm going through "wagon wheel", where I always have fun dancing the car right on the limits of oversteer and understeer. You can see it in the trace -- notice how the line dips up and down, which indicates I am inducing and then catching very small slides.
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06-08-2020, 09:30 PM | #165 | |
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06-09-2020, 03:58 AM | #166 |
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Thunder, are you working on the whole formula?
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06-09-2020, 10:07 AM | #167 |
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My advice is to build 3 separate math channels, then simply embed them. It's much easier to troubleshoot that way. Give it a shot, I think you'll find this is easier than you think. Plus, it will open the door to other interesting things. Understanding the "why" in the formula will be enlightening...it's all physics, in the end.
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06-11-2020, 02:12 PM | #168 | |
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06-12-2020, 11:24 AM | #171 |
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I didn't even notice her.. ha!
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06-12-2020, 07:05 PM | #172 |
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Not a bad day today.
The Corvette did a track record of 1:27.8. Self reported. I don't have a way to verify it. But the driver promised to send my a video link to verify. Driver said car is 3050Lbs with him sitting in the car Previously it was a Viper ACS @ 1:28.9 The Ferrari driver (not the long hair) self reported 1:32 in previous track day. He was not keeping time today. He said. I managed 1:37.35 but the Cup2 were gone in 5 x 20min sessions. Cruised the 6th on 1:44, and gave up on the 7th. Did many 1:38.x and 1:39.x My camera got knocked off position and my 1:37.3 had the data feed, but the camera was pointing at the dashboard. Grrrrrr Here is a spent 2016 sticker MPSCup2. It got me home. Temp hot was inside 152 and outside 152. I am happy with the setup and the -3.5 camber. It is the first time I consume the middle of the tire. PSI was 36 hot. I started at 31 and thought it would go up to 38. but it did not. |
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06-13-2020, 06:01 AM | #173 |
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Date: June 12 2020 Organization: GottrackLi Track: NYST Weather: Dry Tires Front: Stickers MPSCup2 Star 265/35/19 Tire Rack new day 1 Tires Rear: 2018 Proxa RR 2018 eBay new day 2 Brake Threshold: 600 psi (the tone you hear) Best laptime: 1.37.35 DSC: On Comments: This was a fast setup. 1:37.35 is the fastest I went with none slicks on the front. For the first time I went thru 8-9-10 starting at 107mph at 8 and over 100 between 8 and 9. I am happier with my trail braking but it is no perfect by any means. I was carefully to not induce understeer with getting in the throttle too early but the car still understeer. But it feels like a safe understeer so I am happy about that. I reviewed the Corvette 1:27.8 video and the one impression I had is that he goes the shortest distance and cut thru all the corners. With 315 A7 he just take the turns straight with out trying to ne clever. I can do that line if I go 1:44, but no way for me to do that at sub 1:40. I also noticed he does not go over the curbs. perhaps because he is so low that he can't, and at the same time, he does not need to. Anther observation is that his lowest speed thru the turn is not night and day, but most of the turn he is faster than 1:37 pace. What I am going to try on next NYST day is to go his line at the speed I can do it and see how fast I can do that line. I don't have a video as I said previously because the camera got nocked down and was filming the dash :-( Oh... one can dream about A7 all day long.... |
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06-13-2020, 10:37 AM | #174 | |
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06-13-2020, 10:59 AM | #175 | ||
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I have another pair of 2016 Cup2 so I can try 32? The interesting thing is that I ran Cup2 MO-1 on 38 hot and they were consumed as expected. |
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06-14-2020, 09:57 AM | #176 |
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Date: June 13 2020 Organization: SCDA Track: Lime Rock Park Weather: Dry Tires Front: Stickers Ecsta PS91 2019 275/30/19 Tire Rack new day 1 Tires Rear: MPSS 2019 275/35/19 used eBay day 1 Brake Threshold: 1000 psi (the tone you hear) Best laptime: 1:03.2 DSC: On Comments: Oh Boy. This is so much faster track than NYST. End of straight 138mph Worked on trail braking and not hitting the throttle too early. I just could not get bellow 1:03. I don't have a good explanation. Car felt good. Perhaps driver fatigue? Perhaps the much faster pace that it was just too scary to push harder? Many congested laps with slow traffic?. It was a perfect trackday but I just could not get faster than 1:03. Perhaps the tire combination never gave me the confidence to go faster. Perhaps the the setup was too soft for the speed. For the last session I did clicked +1 on the shaft for all 4 corners. The car felt better and more reassuring but did not resulted in a better time or willingness to push harder on the last session. Should have done it first session Video is not very interesting, but will upload later for completeness ** Edit ** Video link |
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