Project 'Wheel' Begins

Welcome to this blog. With the release of GT5 on the PS3, I have decided to build a custom set of pedals for use with a logi-tech DFGT wheel. To mount the wheel, I will also build some sort of driving rig/wheel stand. This blog will detail all the technical aspects of achieving this.

The Pedals


The pedals will be constructed from aluminium pieces with standard steel fixings. I have sketched out a rough concept design and am currently working on converting this into something more exact. The idea is that the pedal is relatively compact in design with the main 'spring assembly' being mounted vertically. To achieve this, the link between the pedal arm and the spring assembly will be a length of wire rope which pulls the spring through via a length of rod going through the spring. I have not seen this design used anywhere else for this purpose, so I hope it will work. 

My rough concept sketches for the pedal

As the Driving Force GT ('DFGT') wheel comes with two pedals, I will make the same. My custom brake pedal will use a load-cell in the design. My idea is to rig up some sort of 'L' shaped bracket to transfer the force from the pedal to the load-cell. The idea behind the load-cell is that it gives a more realistic feel to the brake: it is the force on the pedal, and not the distance of pedal travel, which transfers to the braking force of the car. This is how a real car brake feels. Most commercially available gaming wheel pedals tend to use a 'potentiometer' to control the brake.

My design will have to enable me to build the pedals without the need do any welding.


The Wheel


The wheel is a logi-tech DFGT. The unit does not come with a clutch, although I don't really understand why you'd want want for a racing game, so this is fine. This wheel is an obvious choice as a value-for-money but still functional wheel.



Rig/Wheel Stand

The rig I am planning to build out of MDF. My concept for the rig is that it will be in the form of a fold away box. The purpose of the rig when it is in the 'closed' configuration should not identify what it is used for. The pedals will be mounted inside in an 'overhang' configuration. There will be a wheel shelf inside that the wheel clamps onto.

First Parts Arrive

I have already started ordering a few bits and pieces for this project. The first part I ordered a few weeks ago was the load-cell. I have been browsing a few racing simulation forums and saw this particular load-cell mentioned (I got the 30kg version). I had a search around the web for alternative places to buy load-cells, but couldn't find any load-cells for sale that weren't at least 4 or 5 times more on price.

The battered box containing 
the load-cell arrives from China.

Testing the Load-cell


Ok, so electronically the load-cell consists of a series of resistors arranged in a 'Wheatstone bridge' configuration. Basically, as the load is applied, the resistance somewhere with the load-cell changes causing the voltage across the bridge to change. I'm sure you know all this already. 

The load-cell itself (and a ruler).

Anyway, to test load-cell works I get out my multimeter. I connect the cell up to a 9V DC power source using crocodile clips (red and black wires). Then connect the multimeter across the bridge (white and green wires). I hold one end of the load-cell flat on the bench, pressing down hard with my palm. I use my other hand to press down on the load-cell. I am well chuffed to see the measured voltage change in response to the pressure I apply. Chuffed because this means the thing works.


When the load-cell is in the pedals, it will need to be connected to an amplifier circuit: the voltage from the load-cell alone is very small (in the few millivolts range) and therefore is not large enough to be of use. 


As well as the four wires that I connected up, there is a fifth wire coming from the load-cell. I have no idea what this is for (maybe an earth?), so in true "bodger" fashion, I'll ignore it and hope it isn't important. 


Now I have a (working) load-cell it will help me to finalise the design for the brake pedal.