GPS speed

[Bryan Long]

Our purpose would not be for using GPS speed on the course, but rather to record it along with other parameters so that we can determine slip after the run. Is there a GPS device that would output a signal that we can record? Such as 0-5 volts proportional to speed? Or a pulse output?

[tauruck]

Bryan, I was busy on a deal with a tracking company. Their system is obviously designed to allow fleet managers to monitor vehicle.
The system could relay 8 or 9 parameters to your laptop in real time.
If that's what you meant?.
Mike.

[Bryan Long]

Tauruck, thanks for your input. I will try to be a bit more clear in what I would like to do. We already have a data acquisition system on board the race car. Among other things, we record pulses from a front wheel. From that I calculate speed and compare that with speed calculated from engine RPM. The difference is interpreted as rear wheel slip. This works quite well, but there are some uncertainties. I know that that the speed from front wheel pulses is quite accurate because I can compare it with timing slip data. But that front tire diameter can increase with speed and there might be some slip of the front wheel; not likely very much, but who knows. My thinking is that we could eliminate those two unknowns if we had accurate GPS speed as one of the recorded parameters.

[Stainless1]

Bryan, You are looking for something that is already available, no problem, all you have to do is ditch the data system you have and buy one with integrated GPS.  You can buy standalone GPS recorders, but outputting something that will record on your data system is improbable.  You could sync a time stamp between a GPS recorder and your data system that would help you compare data.

[RogerL]

Talk to the folks at Veracity Racing Data (veracitydata.com), they can fix you up. I run a GPS system on my AWD 'liner that they supplied and made it talk to the Motec for traction control and general speed ref. Works great.

[entropy]

... But that front tire diameter can increase with speed and there might be some slip of the front wheel; not likely very much, but who knows. ...

Bryan,
I too am concerned with the "slip": 
http://www.landracing.com/forum/index.php/topic,14323.0.html

At this point I'm looking for advice, not giving it. 
But it sounds like we are doing something like what you are planning.
Our new lakester is set up with a Racepak system to record calculated mph from both the front (driven) & rear (passive) wheels as well as directly record GPS mph. 
One of our priorities at WOS will be to calibrate F & R mph to GPS mph and from that data calculate and display % Slip of the front wheels.

I am 110% sure that I am way over the top on my obsession on logging mph & on our cool lil box, the % Slip Display.
But i got pretty successful at calculating gearing needs of my bikes, and found it satisfying to NOT be changing sprockets at the track.
Karl

[JC Sparks]

 A Racepak G2X gives you a GPS speed on the dash and also records in on the data recorder along with any other thing you want to record. It will also draw a map of the course that you can then divide  into how many sections that you want, for example you run a 5 mile course, you can break it up into 1 mile increments or how ever many you want. That way it is easy to see entry and exit speeds for each increment of the run. It has a built in G meter that along with engine RPM can help with gearing and tuning. It's a pretty nice recorder.  JC

[Buickguy3]

   So if you put a sensor on one corner of a roadster, will the GPS register rotational speed? 
  Doug 

[maj]

We use a garmin gps 18 to feed our logger an AEM AQ1
its good to reference events, but refresh rate at 1 hz is to little to get good wheelslip data
garmin do a 5 hz gps 18 , and if you want real accuracy look for a 10hz or better
The signal is probably not what you think , although 0-5v its relaying a 3 d position and needs a device configured to read such
nmea , if you want to google it

specs here may help

http://static.garmincdn.com/pumac/425_TechnicalSpecification.pdf   

[krusty]

 "So if you put a sensor on one corner of a roadster, will the GPS register rotational speed?  evil"

The GPS won't, but the RacePak system does measure and record lateral Gs .... 

  vic