Wheel Slip Indicator?

[entropy]

Sumner,
I much appreciate your input, but I'm not looking for closed loop traction control, or an engine management control system.  Those are great additions to a vehicle and i've heard many good things about megasquirt.

I'm not one of those rocket scientists, i'm just looking for a simple device which displays % slip.

We will be logging % slip, and that signal could trigger one of the 4 warning lights on the Racepak dash.
However i'm thinking a line of progressive LED's could help me anticipate and maybe mitigate a traction problem.
I just want put my right foot to work in 1st and see how hard i can accelerate without letting the slip get too bad.  I could probably simply get a 270 degree gauge displaying volts, but i like the idea of a an LED strip.

[manta22]

I think the basic problem is to get a wheel speed from each rear wheel and a front wheel. Maybe a sensor from an ant-lock brake system could be used to do this. Take the difference between the front wheel speed and each rear wheel and display the difference. This way you can monitor which rear wheel is spinning. If the tire diameters are different front to rear, some scaling would be necessary before taking the difference.

Regards, Neil  Tucson, AZ

[sabat]

Karl, is there a 0-5V output on your Racepak? If you could send your math function of GPS x wheel speed, there are digital gauges out there that can give you a visual indicator for any 0-5V signal. -Dean

[sabat]

http://www.veisystems.com/ws/v1-series-single-gauges/34-v1-series-universal-voltage-signal-monitor-.html

[Sumner]

I'm not trying to be a smart a$$ but I think before someone would see the lights and decide what to do about it their butt would already be telling them what is going on.  I will agree that in 1st you can be looking at stuff like this to some degree but in higher gears the ability starts to go away and things happen a lot quicker.

Neil with a spool or say a Torsen one should only need one driven wheel sensor I'd think.  

I realize traction control is still an evil concept to some and might always be, but the writing is on the wall.  Cars like Speed Demon have shown if you want to go real fast with big HP numbers traction control and other computer controls like what is possible now with computerized wastegate control is going to be hard to beat

Sum

[entropy]

Karl, is there a 0-5V output on your Racepak? If you could send your math function of GPS x wheel speed, there are digital gauges out there that can give you a visual indicator for any 0-5V signal. -Dean

Dean,
Racepak sells gauges which can be plugged straight into the system. 
1) the 1st question becomes whether math channel output is available to drive a gauge
2) if it is available, then the 2nd question can that signal drive non-Racepak devices

I am pursuing those questions now.
Karl

I like that lil gauge you linked, and it is kind of along the lines I am thinking.

[entropy]

Sumner,
I have zero car experience and nearly all my LSR bike experience has been on asphalt, so i could easily be WAY off base in looking for a device to display % wheel slip.

Even still, i am determined to get a gauge or a linear strip of LED's (preferably) which tells a glance how traction is trending.  I agee with you that a warning light wouldn't help me. 
Heck, even a strip of 12 progressively colored LED's might not help me give my right foot sensitivity training.
Karl

[entropy]

back to the drawing board.
I appears that my Racepak system math channel output is NOT available to drive external devices
My ever helpful Racepak supplier, Greg Kelley, has contacted Donny at Racepak and he is cogitating on this.
(to be continued...)
Karl

[Sumner]

..back to the drawing board.....Karl

OK now I will be a smart a$$  .  You connect your throttle linkage to a potentiometer/rheostat that is connected to 12 volts and a 12 volt bulb.  The more you lift the brighter the light gets  ,

................... or...............

A non-smart a$$ idea.  A second set of your speed sensors connected to the 0-5 volt aguge if they can output a 5 volt signal. I think most speed sensors have a frequency or switched digital output that wouldn't work with the gauge but I guess there are some that have an analog voltage output. 

The lights are going to require a more sophisticated circuit.

Good luck,

Sum

[bbarn]

Hall sensor on the drive shaft, hall sensor on a front wheel some minor calculations and one of these would do the trick.
http://www.arduino.cc/.

These Arduino boards are pretty slick. There are analog, digital, drivers, switches, software, hardware.. everything you could think of available in these little buggers. They aren't expensive and they are fairly easy to use.

Something to consider in measuring wheel slip. If the front and rear wheels grow at different rates, you could actually slip the rear wheels and show that the there is no slip at all. As the rear tires grow, the ratio of ground speed to RPM will change. I would do a little bench testing to see how your tires grow at speed and measure the growth. With that, you can probably supply better data into your function to determine if the wheels are slipping.

For those that don't believe tires grow, I'll include a little video and some data.
This is a 30" M/T Bonneville tire spun to s surface speed of just about 540 MPH. The static height of the tire is 29.2" and the full growth in this video is 34"!

http://youtu.be/CBhiJNbB6KA

[Richard Thomason]

In tuning your slip system, whatever you have, use the coast down data at the end of the run. You will have zero slip at that point and the growth is there. You should be able to then train your system with good base line numbers to work from.

[entropy]

Hall sensor on the drive shaft, hall sensor on a front wheel some minor calculations and one of these would do the trick.
http://www.arduino.cc/.

These Arduino boards are pretty slick. There are analog, digital, drivers, switches, software, hardware.. everything you could think of available in these little buggers. They aren't expensive and they are fairly easy to use.

Something to consider in measuring wheel slip. If the front and rear wheels grow at different rates, you could actually slip the rear wheels and show that the there is no slip at all. As the rear tires grow, the ratio of ground speed to RPM will change. I would do a little bench testing to see how your tires grow at speed and measure the growth. With that, you can probably supply better data into your function to determine if the wheels are slipping.

For those that don't believe tires grow, I'll include a little video and some data.
This is a 30" M/T Bonneville tire spun to s surface speed of just about 540 MPH. The static height of the tire is 29.2" and the full growth in this video is 34"!

http://youtu.be/CBhiJNbB6KA

bbarn,
thanks a million for the Arduino link.  I had never heard of it.  What a concept, make it easy to build electronic lil electronic gizmos".  Interesting to know about and possibly I could even do it.
 

[robfrey]

Radio Shack carries Arduino but it will be a few bucks more than getting it from Amazon. You will just need a an UNO not a MEGA. Welcome to the Arduino world!

[maj]

I cant see where the Uno reads frequency ? or can the 0-5v inputs be programmed for freq ?
but my understanding of electronics is pretty basic

i was wondering about a frequency comparator of some sort using simple ic's

Update
called a mate thats good with this stuff and he suggested this

http://www.altronics.com.au/index.asp?area=item&id=K6220
http://www.siliconchip.com.au/Issue/2009/November/Twin-Engine+Speed+Match+Indicator+For+Boats

gauge supply could be intercepted for logging , and you could make pickup reading adjustments to dial in tire size differences

He also explained Arduinos , they would work well ,but depends on the level of complexity you want to which system would be the better choice   

[donpearsall]

I am happy to see that there is still some interest in a Slip Indicator. I originally started this thread and after determining that nothing existed that I could just bolt on, I began prototyping an indicator that may work for me while riding my bike. My name for it was "Slipometer".

The prototype works as designed - BUT when I tried it out at Bonneville I found out that I was paying way too much attention looking where I was going than at the slip indicator. Then on one run my engine blew and I got busy rebuilding the bike and engine and the Slipometer has just been sitting in a box.

Here are a few features:

1. The Slipometer is merely just a counter that keeps track of two inputs - the front wheel and the rear wheel speed.
2. Input is via a stationary hall-effect sensor that counts passes of a rare-earth magnet as the wheel revolves.
3. The indicator has 15 sequenced LEDs that are green, yellow, red. You can program the LEDs to light up at a certain percent of slippage.
4. Display is a 16 x 2 LCD.
5. It has a crude menu system where parameters such as the slippage limit, KPH or MPH, wheel circumference, etc are set.
6. While running, the speed is displayed in MPH or KPH.
7. While running the RPM of each wheel is displayed.
8. At the last minute I added a feature that would close a switch and ground an input wire at a certain % of slip. This was to act as a sort of traction control in conjunction with my Dynatek piggyback ignition. Grounding a particular wire retards the ignition.

It was a fun and educational project. However for racing I don't know if it is practical. In a bike environment you are hunched over, can barely see out of your helmet, the displays are real close and out of focus (for me at least), and there is way too much concentration just to stay on course and upright. Something like this may be better suited to a car environment.
Here are some pics.