tools and/or info on lap data analysis

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i-Zapp
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tools and/or info on lap data analysis

Post by i-Zapp »

So now that i've got all this great data, how do i make my rider faster with it???!!!

some questions that come to mind:
* what is the max lateral g's capable? our cornering data occasionally exceeds 1.0g (spikes) - should/can i expect more from the tires?
* can we expect the same capacity during braking (lineal)?
* is there a way for users to share laps (via internet); for sure, comparison to other riders would be ideal

are there any books, internet sites, etc that might help?
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Harry
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Re: tools and/or info on lap data analysis

Post by Harry »

Hi i-Zapp,

Good topic, I hope a lot of user will join the thread!

On the items raised: the question always needs to be "overall G", not "lateral G". Overall G is the combination from all forces that finally need to be transferred to the road by the car's tires. If for example you drive around a corner with 1G lateral force at constant speed (0G longitudinal acceleration) things will be fine for most cars. In case you press the brakes in this situation, generating -0.5G longitudinal acceleration on top, your tires need to transfer the combination of 1G lat and 0.5G lon (which is sqrt (1.0^2+0.5^2) = 1.12 G, check http://en.wikipedia.org/wiki/Circle_of_forces for more information) to the street - which is probably beyond the car's capabilities. The overall G a car can transfer to the road depends on the tire's capabilities, on the position of the center of mass, and other factors. A well balanced sports car for public roads will be around maybe 1.2 G max, others will be below or above. You really need to know your car and your driving capabilities... The difference in G a vehicle can transfer is the reason LapTimer allows you to set the threshold of acceleration color changing from green to yellow to red individually.

Sharing laps is possible on a peer to peer basis: just export any lap to .hlptrl and send it to a friend (peer). He/She can import this .hlptrl file from his/her Mail app.

- Harry
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i-Zapp
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Re: tools and/or info on lap data analysis

Post by i-Zapp »

Harry wrote:Hi i-Zapp,

Good topic, I hope a lot of user will join the thread!

Sharing laps is possible on a peer to peer basis: just export any lap to .hlptrl and send it to a friend (peer). He/She can import this .hlptrl file from his/her Mail app.

- Harry
i presumed the 'Online' feature would offer this capability when i accidentally found it the other day. i was hoping that the ability to upload your lap to a server (Harry hosted?) existed, and that it would be possible then to DOWNLOAD laps from others to compare.

i will prepare some images re g-loads to initiate some discussion... hopefully all the smart guys arent too tight-lipped!
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Harry
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Re: tools and/or info on lap data analysis

Post by Harry »

The Online function does not distribute all the data collected within LapTimer. The set of data is documented here: http://www.gps-laptimer.de/Online_Racing.html

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i-Zapp
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Re: tools and/or info on lap data analysis

Post by i-Zapp »

ok, i'll kick this off was some data generated by my son on a Kawasaki Ninja 250 trackbike, using an iPhone and XPGS150 running at 4hz. The GPS data was recalculated for acceleration (no iPhone accelerometer data was used).

keep in mind that this machine is fairly underpowered bike (~25 hp), so maximizing the tires' potential and maintaining momentum is the name of the game. i'm keenly interested in analyzing this data in the hopes that it might reveal areas for improvement.

so let the games begin!!!
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i-Zapp
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Re: tools and/or info on lap data analysis

Post by i-Zapp »

here is my swag at analyzing Turn 1 which is a good one because it it occurs at the end of long straight and is fairly high g's.

comments and discussion appreciated!
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gplracerx
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Re: tools and/or info on lap data analysis

Post by gplracerx »

I don't think a bike is going to be able to generate the same overall acceleration as a car. And even a car won't do 1.2g on street tires on a flat corner. It will if the corner is banked, but that's because some of the lateral acceleration in the GPS frame of reference is actually vertical acceleration in the car frame. I'll have to post some of my data from some laps around Bristol Motor Speedway to demonstrate. And most cars or bikes won't generate 1 g lineal either braking or accelerating.

That being said, the transition from braking to cornering in turn 1 could have been better. Ideally you shouldn't see a dip in the overall acceleration.
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Re: tools and/or info on lap data analysis

Post by i-Zapp »

for sure this is not a straightforward exercise (no pun intended) - here's my assumptions:

1. the 1.2 µ value comes from an SAE paper that used a traction trailer under braking only. You'd have to make the assumption that a motorcycle tire's lateral CoF is the same as its longitudinal. (i've been told it may even be higher); one issue we do have is that we can't seem to warm the tire up sufficiently due to small bike, small rider. We may switch to softer compound if we can find.

2. mathematically speaking, the vehicle's acceleration in g's is limited to the tire's CoF (g's <= µ)

3. braking g's are limited NOT by the tire CoF but by the tendency of the rear wheel to lift. it's virtually impossible to lock a front tire on a racing bike (while not cornering)

While the math and all the data is very interesting, it does come down to the actual rider's comfort level on the bike. If he FEELS the bike wiggle and get loose, THAT is the limit, and no amount of techno talk will convince him to push harder.

It may turn out that the benefit of the analysis of these lap traces may be just looking for "holes" where there's opportunity to brake later, turn in sooner, or exit quicker. There's got to be other spots too... like going SLOWER in one corner to go faster in another...
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