While i’ve been tinkering with many things over the time since my last post. Most of it has not really been very noteworthy or at least nothing that would probably be of interest or use to anyone else.
However, inspired by now owning a 2L turbo sports car and some recent participation in some motorsport events i’ve decided to build a racing simulator. It’s nothing new, i don’t claim it to be but i’ve decided to collaborate some of the things i have done in hope that it might help someone else going down the same path.
The aim of this project is to produce a somewhat life-like simulator without using a standard shop bought wheel/pedal set. I’ts not going to be real, i know, but here’s my ‘requirements’:
- Realistic steering wheel with as much rotation as possible
- Analogue Clutch
- ‘H’ pattern gear shifting
- Analogue Hand/E brake
- Force measured brake (not movement like normal pedal sets)
- Small/Storable/Disassembleable (I don’t have a spare room for a sim cockpit)
- Strong/Durable
- Cheap!
The intended target platform is a PC running ‘Live for speed’
I started this project a couple of months back, starting with the wheel and now i have just completed the pedals. The steering mechanism was construced utilising a 2:1 ratio cam belt driven gearbox giving a theoretical ‘lock to lock’ of 540 Deg. A little less than i wanted but it works ok. There’s nothing too technical about it other than the gear reduction. It uses a real sports steering wheel too. A keen eye might also be able to tell what the bearing/shaft supports are recycled from 
The pedals were heavily based on the design of the commercial product from http://www.cannonsimulationtechnologies.com. Todd of CST also sells a ‘DIY’ guide for making a pedal set that is somewhat comparable to his commercial product for only US$12. I probably could have constructed my pedals without the need for the guide but i went and bought it anyway. I saw it like paying royalties for his design and i think it’s only fair he gets some reward for his efforts.
The main difference with my pedals are basically the fact that i have constructed them almost entirely of things i had at home already or i could acquire for free. The problem for someone attempting to replicate what i have done is, not everyone would have the stuff lying around like i do but parts can easily be substituted.
So far, the build has only cost me about $80. The bulk of that cost is for the rod ends that go to the tops of the pedals at ~$16ea. The springs were about $7 each. The steering mechanism has been totally free so far.
All these mechanics are no good without some way to interface them with a PC. I tinkered with the idea of using an optical mouse to track an encoder mounted to the steering wheel at first but this was not far from epic fail. It worked but was too unreliable, lost it’s center and basically sucked. One advantage it did have was an almost unlimited number of rotations. Pity it sucked everywhere else. Abandoning the optical mouse idea, i moved to the old pot style joystick. I happened to have an old E-Sky USB trainer in the cupboard that i never use anymore so i gutted that – The result is the ability to have 4 axis analogue joystick control. Only problem was that ideally i needed 5 analogue inputs but it was enough for ‘proof of concept’ for now.
Not long after destroying the USB trainer I came across Leo Bodnar’s site. He sells a generic USB interface that provides 6+ Analogue inputs as well as 32 odd buttons. While his product is good, it did not really follow the rule of cheap. At about $80 to get one to my door, it would have doubled the current cost of the build. Some more googling turned up a ‘product’ called Mjoy by Mindaugas Milasauskas. It’s a DIY USB joystick interface based on an Atmega8 AVR. It seems that his legacy goes on but for some reason his website is gone. I am making Mindaugas’ and version of the joystick interface (for a fraction of the cost of Leo’s). All of my designs and ideas will be published here.
The interesting thing with the CST pedals is the use of a load sensor for the brake sensing. This is a superb idea (Although Todd admits it was not his). This will give a much more real feel to the brake pedal. I managed to salvage a load sensor from some industrial scales some time back – I knew it would be good for something! The problem is the interface between the load sensor and the joystick controller. The load sensor only puts out ~2mv at full load, we need 0-5v scale for the joystick interface. Some more googling dug up an ‘off the shelf’ chip designed for this exact task. It’s an INA122 by Burr-Brown (owned by Texas instruments i believe). As it turns out, this appears to be the chip Leo uses in his controller with load cell interface. The difference with me is, i’m going to give you all the info you need to get it running with Mindaugas’ design for free.
Details to come….
Tags: DIY USB Joystick, LFS, Live for speed, Mjoy, Racing Sim
Hi mate, beautiful looking project, love your work.
I am looking at undertaking my own set of custom pedals with the load cell brake as you have done.
I was very close to purchasing Leo’s board until I read you article, and now am very interested in the cheaper alternative you speak of. Like yourself, I will be aiming to do this on the cheap, and using mostly recycled aluminium and such, its amazing what people throw away!
What rating (kg/lb) is the load cell you used, and also where did you find the large springs?
Thanks again for your info, this is exactly what I was looking for.
Hi, Thanks for the comments.
My load cell is a 100kg item. Not by preference but by coincidence – It’s just what i had. It doesn’t really matter if it’s a bit bigger than the normal ones (30/60kg) people are using as you can just bump up the gain on the load cell interface or add mechanical advantage over the cell on the pedal. My pedal feels firm for the response but i would even say it could be harder.
After looking around on Leo’s forum, it’s also apparent that he seems to have gone missing or something. Many people have ordered his boards and not receiving them even months later with no contact from him whatsoever. It may have changed since but beware….
The Springs were purchased from my local hardware store (Bunnings). They have a collection of CSC springs there. They were about AU$6 each.
I’ve actually done more work on my setup since but i have not posted details yet. Check back soon and you’ll see the somewhat finished product.
Sounds good, I look forward to the updates.
I had read similar things about Leo going missing. I noticed most of his boards were listed as ‘out of stock’, so I shot him an email, but no response yet. Yet another reason I am so interested in the details of your build.
I had been advised on a 30kg cell, but was thinking along the same lines on the bigger ones, mainly in the mechanical advantage area. The load cell itself will probably be the biggest single cost in this project. A quick scour on ebay found a 35kg for just under $25, or a 60kg for just under $50, so plenty of options to play with.
Anyway, keep up the great work, I look forward to the updates.
Great work here! I really enjoy following your posts as I’m in the process of building my own Pedals.
Just thought I’d say in Leo’s defense, I just orderd from him and got my order in 4 days. So he’s not missing.
I thought a while about making my own PCB and such, but I’m not that gifted in the way of souldering! haha
Thanks for these very informative posts!
Thanks for the comments. Glad to hear Leo’s back on board. Making your own is not for everyone. If you’re not confident/competent doing it yourself, it could easily end up costing you as much as Leo’s board anyway. I just posted the info here for people to DIY if they can and want to. It’s also helpful for those that want to convert existing pedals to load cell brake with the load cell interface.