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Aim_Slip_factor (Mychron question)
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Ray Lovestead



Joined: 21 Dec 2011
Posts: 206
Location: United States, Colorado, Louisville

PostPosted: Thu Jul 04, 2013 8:40 pm    Post subject: Aim_Slip_factor (Mychron question) Reply with quote

Any Race Studio pros out there?

I'm looking at the aim_slip_factor math channel which compares engine RPM to speed. I can't tell whether this slip factor is merely clutch slip or tire slip (understeer vs. oversteer). Does anyone know what the formula they are using means?

Also, I'm running a shifter. So the scale on the left is a little strange considering I'm running gears up and down.

Does anyone know how to detect understeer/oversteer using Mychron?

Ray
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joseph hollinger



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PostPosted: Thu Jul 04, 2013 9:41 pm    Post subject: Re: Aim_Slip_factor (Mychron question) Reply with quote

Ray Lovestead wrote:
Any Race Studio pros out there?

I'm looking at the aim_slip_factor math channel which compares engine RPM to speed. I can't tell whether this slip factor is merely clutch slip or tire slip (understeer vs. oversteer). Does anyone know what the formula they are using means?


Clutch slip. If you want to measure tire slip you have to have a speed sensor that is not part of the acceleration or braking system (e.g., a fifth wheel).

Ray Lovestead wrote:

Does anyone know how to detect understeer/oversteer using Mychron?

Ray


I'm just speculating, but I would think that you would need to measure steering angle or something else that would function as a proxy for the actual slip angle of the tires. Does not sound do able.
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Adi RocK



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PostPosted: Fri Jul 05, 2013 3:53 am    Post subject: Reply with quote

I use GPS speed vs axle speed to measure slip. Not sure its the right way tho.
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Ray Lovestead



Joined: 21 Dec 2011
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PostPosted: Fri Jul 05, 2013 6:20 am    Post subject: Reply with quote

So I agree that this is clutch slip (aim_slip_factor). But does this graph also mean that I've have a lot of slip at lower speed? I don't understand the magnitude of the y-axis.

This is the longest straight on the track. I'm getting 0.6 slip as I apply throttle at the apex. And 0.35 at the end of the straight. To me this means 3 things.
1. slip of my clutch occurs most at low speed.
2. I am slipping through the entire length of the straight.
3. I never have a slip of zero. My clutch is slipping all the time??

This doesn't seem right. Especially since this lap was the fastest lap I've ever run at this track.. and a competitive time.


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Bill Boxell



Joined: 22 Aug 2007
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PostPosted: Fri Jul 05, 2013 6:26 am    Post subject: Reply with quote

Adi RocK wrote:
I use GPS speed vs axle speed to measure slip. Not sure its the right way tho.


AIM_Slip_Factor = (Speed/GPS_Speed)

As Adi said, Speed is axle speed.
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Bill Boxell



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PostPosted: Fri Jul 05, 2013 6:33 am    Post subject: AIM Push / Loose Reply with quote

http://www.aim-sportline.com/download/doc/eng/on-track_sessions/gps_mxl-pro_analisi_adria_eng.pdf
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Ray Lovestead



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PostPosted: Fri Jul 05, 2013 8:33 am    Post subject: Reply with quote

Bill I ran Engine(RPM)/GPS Speed and it is nearly the same as slip_factor.

It couldn't be speed/GPS_Speed for me, because I don't have Speed.

And now that I'm looking at the data closely, it appears to me that Race Studio is applying a filter to RPM/mph to get it to look smooth. One of my complaints about Race Studio is that it does too much processing to make it look good. I need to see it more raw.
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Bill Boxell



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PostPosted: Fri Jul 05, 2013 9:18 am    Post subject: Reply with quote

Ray,

It's not the same. The normal slip channel is compairing axle speed (axle mph really) to gps speed. You get a channel that is about = to 1 when going down the strait and not spinning the tires. It may go negitive under braking and positive spinning the tires off the corner.

You could get the same result by having a math channel the generates axle speed (axle mph) based on RPM, the gear (ratio) your in and tire circumference. Then the result of that math channel (axle mph) could be used by the slip math channel.

Bill
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Ray Lovestead



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PostPosted: Fri Jul 05, 2013 12:34 pm    Post subject: Reply with quote

That sounds right. I'll work on getting that put together.

Any tips on how to detect understeer/oversteer? Does that require a steering wheel sensor?

Ray
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Walt Gifford



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PostPosted: Fri Jul 05, 2013 7:22 pm    Post subject: Reply with quote

I use the rpm vs time plot and any clutch slip is shown as a horizontal line.


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Chris Parks



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PostPosted: Sat Jul 06, 2013 4:53 am    Post subject: Reply with quote

Ray Lovestead wrote:
That sounds right. I'll work on getting that put together.

Any tips on how to detect understeer/oversteer? Does that require a steering wheel sensor?

Ray


Run a steering sensor against lat_accel is most probably the best way.
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Chris
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Bill Boxell



Joined: 22 Aug 2007
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PostPosted: Sat Jul 06, 2013 5:46 am    Post subject: Reply with quote

Ray,

If you decide to get a steering sensor I would recommend getting the Mychron kit to get the connectors, pulleys and belt but then spend another $15 or so and get a 10k ohm 270 degree potentiometer. The Mychron kart sensor is a 5 turn pot. and the channel ends up being quite noisy when trying to see fairly small differences.

Bill
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Ray Lovestead



Joined: 21 Dec 2011
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PostPosted: Sat Jul 06, 2013 7:26 am    Post subject: Reply with quote

The examples of the steering sensor look very noisy indeed. Has anyone tried using the additional math channel filtering to clean it up?

Ray
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Ray Lovestead



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PostPosted: Sat Jul 06, 2013 7:31 am    Post subject: Reply with quote

Walt,

Why would RPM vs Time show up as a horizontal line? The RPM can still go up with a slipping clutch. I would guess that when the clutch is slipping, the RPM would quickly shoot up (as there is less load on the motor).
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Roger Caddell



Joined: 18 Jul 2001
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PostPosted: Mon Jul 08, 2013 4:36 pm    Post subject: Reply with quote

Would anybody like to join a quick Webinar to discuss AiM data and basic items brought up in this thread regarding karts? I would suggest the topics brought up in this thread (clutch slip, basic math channels, under/oversteer)

I am thinking tomorrow Tue July 9, 2013 at 5pm Pacific. This would allow anybody in the Eastern timezone to join at a decent hour.

Drop me a note at roger@aimsports.com and lets make it happen! I have limited spots, first come, first served but I certainly want the thread starter Ray to have a spot. Smile
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