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peter hudson
Joined: 11 Dec 2012
Posts: 10
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 Posted: Sun Mar 31, 2013 10:06 am Post subject: lateral g question |
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Hi All,
New guy here, with a question on mychron with gps05 data. When looking at the lateral g channel, the peak values are up around 2 gs. that was a surprising number to me. I expected something a lot closer to 1. The track builder routine seems to construct the track alright from the data so maybe it's about right.
what sort of gs do those of you with acceleration data typically see?
-Peter- |
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Mike Unger
Joined: 18 Jul 2001
Posts: 308
Location: United States, Ohio,
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| Posted: Sun Mar 31, 2013 10:56 am Post subject: |
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I have measured Gs using GPS and using an accelerometer.
Karts typically see Gs from 1.8 to 2.5 Gs.
Typical street cars 0.9
Typical non winged race cars 1.5
Why?
The weight if a kart relative to how much tire it has is enormous.
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peter hudson
Joined: 11 Dec 2012
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| Posted: Sun Mar 31, 2013 3:32 pm Post subject: |
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Thanks Mike,
I'm not sure why but that really makes me happy. Karts continue to amaze me for the cost to performance ratio.
-Peter- |
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Paul Makarucha
Joined: 11 Jun 2002
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Location: United States, New Jersey,
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Mike Unger
Joined: 18 Jul 2001
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Location: United States, Ohio,
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| Posted: Sun Mar 31, 2013 6:53 pm Post subject: |
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Wait till you start comparing yaw rate capabilities of a kart compared to Anything else.
Even for an engineer like me who has been doing this for quite a while karts continue to impress me.
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joseph hollinger
Joined: 12 Sep 2002
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Location: United States, California, san francisco
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| Posted: Sun Mar 31, 2013 7:21 pm Post subject: |
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Maybe you guys are looking at the numbers in a different way, but when I look at my data its pretty clear that the high G numbers are basically instantaneous. As in they last for fractions of a second. When you see numbers quoted for cars, its typically the value that the car can sustain on a skid pad. Karts can't sustain 2.5G on a skid pad any more than a car can (absent some type of aero assist).
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Mike Unger
Joined: 18 Jul 2001
Posts: 308
Location: United States, Ohio,
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| Posted: Mon Apr 01, 2013 3:28 am Post subject: |
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I am comparing karts on a race track to cars on a racetrack.
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Chris Livengood
Joined: 24 Jul 2001
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Mike Unger
Joined: 18 Jul 2001
Posts: 308
Location: United States, Ohio,
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| Posted: Mon Apr 01, 2013 5:48 pm Post subject: |
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I have the AIM GPS system on the kart now and the one that caught my eye is the Yaw rate.
My son navigating Kershaw at the limit but not spinning or sliding measured a yaw rate of 61 degrees / sec. That might not sound impressive but when compared to passenger cars that is nearly 3X the capability. I don't know what a open wheel car would read.
But considering a kart has a very very low CG, very lightweight and very very low polar moment of inertia I guess its easy to understand why.
I hope to get to the track and have my son to a slalom maneuver on the straights where he will increase his steering input until the kart becomes uncontrollable. I am curious to see what the max Yaw rate is possible. |
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peter hudson
Joined: 11 Dec 2012
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| Posted: Mon Apr 01, 2013 6:20 pm Post subject: |
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| joseph hollinger wrote: | | Maybe you guys are looking at the numbers in a different way, but when I look at my data its pretty clear that the high G numbers are basically instantaneous. As in they last for fractions of a second. |
I see it ramp up early in a turn, peak somewhere near the apex at about 2.1 g then drop off as I exit ... I expect if i were a better driver it would be nearer to the peak through more of the turn, but it still would only last a short duration. |
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joseph hollinger
Joined: 12 Sep 2002
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Location: United States, California, san francisco
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| Posted: Mon Apr 01, 2013 7:35 pm Post subject: |
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Really? Is that with GPS or accelerometers? Just asking because that is not at all what I see. Mine has a lot of variation within each turn and generally the peak value lasts for about one sample (i.e., 1/10 of one second). I'd love to see a sample trace.
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Mike Unger
Joined: 18 Jul 2001
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Location: United States, Ohio,
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| Posted: Tue Apr 02, 2013 3:29 am Post subject: |
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Teach me how to post pictures and I will be happy to.
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Paul Makarucha
Joined: 11 Jun 2002
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Location: United States, New Jersey,
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| Posted: Tue Apr 02, 2013 5:14 am Post subject: |
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| Mike Unger wrote: | | Teach me how to post pictures and I will be happy to. |
[img] LINK TO PICTURE .JPG [/img]
Example: Fantastic KZ1 driver and all around nice guy. Alessandro Bressan:
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Last edited by Paul Makarucha on Tue Apr 02, 2013 5:17 am, edited 2 times in total |
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Paul Makarucha
Joined: 11 Jun 2002
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Chris Livengood
Joined: 24 Jul 2001
Posts: 2432
Location: United States, Pennsylvania, Da Burgh
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| Posted: Tue Apr 02, 2013 10:28 am Post subject: |
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| Mike Unger wrote: | I have the AIM GPS system on the kart now and the one that caught my eye is the Yaw rate.
My son navigating Kershaw at the limit but not spinning or sliding measured a yaw rate of 61 degrees / sec. That might not sound impressive but when compared to passenger cars that is nearly 3X the capability. I don't know what a open wheel car would read.
But considering a kart has a very very low CG, very lightweight and very very low polar moment of inertia I guess its easy to understand why.
I hope to get to the track and have my son to a slalom maneuver on the straights where he will increase his steering input until the kart becomes uncontrollable. I am curious to see what the max Yaw rate is possible. |
Low mass, bias ply tires, and soft compound tires are likely the biggest factors contributing to the yaw. Radial tires are a good bit harder to drive in general, let alone slide. Also, be careful with GPS data. When overlaid with wheel speed data there is always a large margin of error.
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