Sunday, December 30, 2007

Seat of the Pants

As many of you know, I'm an avid racing enthusiast and I've got a pretty good setup at home for playing PC based racing simulations. One of my particular favourites is Live for Speed (

Most of these games are now realistic enough calculate the forces acting on the car/driver and many people have developed home-brew "motion seats" allowing the player to "feel" the car in the simulation.

One company in Japan ( offers a commercial kit for building a home motion seat. I was particularly interested in this but concluded it is over expensive with prohibitive shipping costs and production delays.

I've decided to start out on a project to build a simpler kit providing a motion seat for home racing enthusiasts here in the UK and Europe. During my research I discovered a great piece of software called X-Sim ( which already contains links to Live for Speed and connects to a variety of hardware interfaces. So with X-sim and a basic design in my head I set out to build a small model prototype of a motion seat...

The video above shows my first attempt at getting motion from a crude cardboard platform (complete with Teddy that my girlfriend Lucy got me during a holiday in Gozo ;-) ). The PC interface is a Velleman K8055 USB i/o card connected to a dual h-bridge motor driver IC. The 2 servo motors are basic RC servos with the electronics removed.

Although the X-Sim software is great (I would recommend it to any diy motion builder) it has a couple of constraints that are causing the motion not to be completely accurate. Also the servos used here are relatively slow and only driven at a single speed currently.

Anyway, it works pretty well for a quick design test. Obviously being made from cardboard and paper clips it is not perfectly calibrated but as a first foray into PC controlled motion... quite exciting!