SCA Develops Cartie Simulation Software

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Click on the thumbnails below for full size screen shots

The SCA's back room boffins and their clever little coding elves have been busy doing some fiendishly clever things with computers of late, and they are nearly ready to launch a full blown cartie simulator on the unsuspecting gravity racing world.

SCA CartieSim is a application that can predict the speeds of a cartie at any point on a course from some simple data describing the cartie and the coordinates of the course. The course can be loaded from a GPS data file or, if you don't have access to that, then a simple route from Google Maps or Google Earth can be loaded instead.

Taking into consideration such variables as overall mass, drag factor and rolling resistanc along with the gradient and turn radius of the course, the application plots a profile of speed against distance and can even identify sections of the course where you may need to use your brakes!

Key features:

  • Course data loaded from GPS file, CSV file or online from Google Maps and satellite altitude database
  • Simple "Course Wizard" guides you through loading a new course
  • Calculates speed profile, time and maximum speed
  • Calculates course data such as total length, average gradient, maximum gradient
  • "Critical Velocity" calculation predicts sections where braking may be required
  • Models dead, push and ramp starts
  • Models different cartie configurations for comparison
  • Calculates stopping distance after finish line
The program is currently in its final testing phase, and the first production version should be available in the next few weeks.
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WOW! This looks excellent,

WOW! This looks excellent, what a brilliant tool!

Even more "wow" is the prediction of a top speed of almost 79mph - !!!!!!!!!!!!!!!!!!!!!


azuma | February 12, 2011 - 20:50
scottishcarties's picture

In reality, probably a bit

In reality, probably a bit lower than that. Those big "critical speed" stalactites show where you'll need to brake. In reality, probably not much about 70mph. Still fast enough though.
scottishcarties | February 12, 2011 - 20:57

Woah, that looks awsume. So

Woah, that looks awsume. So using this would it be possible to pridict my speed for CSEX given my speeds for dalby, cadwell and belchford (dalby: 65mph, cadwell: 49mph, belchford(no barrels) 48mph)
Lee (not verified) | February 13, 2011 - 21:05
scottishcarties's picture

Yes, in theory. It would

Yes, in theory. It would help if you could give figures for any or all of the following;

  • all up mass (including driver)
  • total mass of wheels
  • frontal area
  • drag factor
  • rolling resistance
  • track width
  • static coefficient of friction between tyres and tarmac
  • estimated height of centre of gravity (with driver)
On which hill did you clock 49 at Cadwell?


scottishcarties | February 14, 2011 - 14:01

I saw this app today, and it

I saw this app today, and it looks very good indeed. We had a play around with it, simulating various potential tracks. I really like the braking perdition part of it. We played around with the cart parameters until we got a speed which roughly matched my top speed at dalby. we then changed the course to CSEx and it came out at over 75Mph (!!) of course that's only very approximate, I will need to fine tune the parameters, like accurately measuring my tyre friction etc and working out my COG etc as we just used rough estimates. We had to set the CdA rather low, 0.2 IIRC but looking at the drag factors of some HPV that does not sound too far off, have a look at for drag factors of HPVs
lee (not verified) | February 27, 2011 - 19:19
scottishcarties's picture

drag coefficients

The figures at are not drag coefficient (Cd) but drag area (CdA). CartieSim separates out the two terms and you need to enter both the frontal area (A) and the drag coefficient (Cd). Some typical Cd values are here and here.

If you want to use drag area (CdA) instead of drag coefficient (Cd), you'll need to set the area to 1 regardless of what the real area is.

scottishcarties | February 28, 2011 - 09:49

Any idea when this will be

Any idea when this will be ready?
Anonymous (not verified) | June 18, 2011 - 19:53
scottishcarties's picture

august. probably.

Unfortunately we ran into a few unexpected delays when we discovered that the "standards" for GPS data files are rather variable in their implementation. We're right in the middle of getting ready for Cairngorm Soapbox Extreme so are a bit pushed or time at the moment, and are hoping to have something available software-wise in August.
scottishcarties | June 20, 2011 - 13:51
scottishcarties's picture

Soapbox simulation software available soon

We're still on target for releasing SCA CartieSim in August - it's basically just testin, bug fixing and updating the help files now, with a few bits of polishing and tweaking as well. To whet your appetite, here are some graphs... (click on each one to see larger versions)

Graph 1
Team Caiman's final run at CSEX2011 (SatNav data, in red), with predicted speeds in green.
Speed data logged by Night Train at CSEx2011 (in red) with predicted speeds shown in green.

The effect of extra ballast... 10Kg is worth about 1.5mph

The effect of rolling resistance. The difference between perfectly frictionless wheels and the worst bearings you have ever seen isjust over 2mph

The effect of drag...
scottishcarties | July 22, 2011 - 15:11

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