The post by Outspacer accurately describes the problem i.e. The G29 only uses a small part of the potentiometer rotation; approx 60 degrees, corresponding to the movement of the pedal, and in this 60 degrees you need to achieve 0-100% of the resistance of the pot. There are no readily available pots in the world with this characteristic. I found one Burns B5 taper pot that was close, but no supplier would stock or order it. Obviously Logitec had them custom built (minimum order 10,000 units + tooling fee, in China. I checked). After some experimenting, and many failures, I also discovered that the overall resistance doesn't really matter, only the relative resistance between the slider resistance and the overall resistance i.e. percentage.
So the solution is to NOT use a rotational pot, and instead use a slide pot and mount it on the rear of the pedal itself. I got this idea from looking at the expensive sim pedals, as they all mount their sensors directly onto the back of the pedals.
Unfortunately regular slide pots have an expected life of around 5,000 operations, which would last less than a week if you raced every day. So after a bit of research I found an industrial application "Linear Motion Position Sensor" which is good for 2-5 million operations. It's not cheap, but it's less than a new set of pedals, and will last many times longer than the standard logitec pots.
https://www.sensata.com/products/position-sensors-encoders/9600-spring-return-linear-position-sensor
These are readily available via RS components (check for your country's distributor)
https://uk.rs-online.com/web/p/linear-transducers/9234139/
As you can see there are three sizes, but I could only order the largest one, 1.5 inches of travel, 5.1 k ohms. Turns out this was a very good thing... See below mounting position.
Despite Covid lockdown, the pot arrived promptly by international courier and I set about finding a way to mount it. This obviously requires approximately 1.5 inches of pedal travel and if you measure your pedal you'll quickly realise that you need to be OUTSIDE the plastic housing to get that much movement :-0
This is also NOT a pretty solution! But hey, the final outcome is freaking awesome IMO.
It turns out that if you mount the pot directly on the outside of the angled plastic cover, it achieves exactly 1.5 inches of travel. Bam!
Now, I know what you're thinking, what about dead band? What about calibration? How do I connect the wires? All of this is possible with some amount of cunning.... I used double sided tape and a cable tie (because no solution is complete without a cable tie). Drill a hole and poke the wires out through the housing, and you can connect the wires before mounting the pot. Start GTS, go to a track, and position the pot in such a way that it's got the desired amount of dead zone, then stick it to the double sided tape. Mine achieved perfect calibration on the first attempt but if you need more/less dead band just move the pot back/forward before sticking it down, and for more/less travel you could wedge something under either end of the pot to adjust the angle before applying the cable tie. I think GTS auto calibrates the maximum position anyway, similar to how it does for the brake (every time you press the pedal :-/ ) Obviously two small holes are required for the cable tie, or you could take your chances with just the tape.
Because the pot has a spring return you don't need to fix it to the back of the pedal, the slider is nicely rounded on the end and the pedal is smooth chrome so it slides smoothly. I found that in between the plastic insert and the side return was perfect. CHECK that the pedal doesn't hit the pot, or the wires, when full depressed. I have a slight angle on the pot so it just misses both. See photos below.
So there it is! It's not pretty, and it's not cheap, but I reckon it's a good solution which achieves:
1. Improved throttle accuracy (1.5 inches travel vs a few millimetres in a rotational pot + high quality industrial sensor vs cheap ass pot construction)
2. Calibration of dead zone & throw
3. Long term reliability (2-5 million ops)
4. Replaceabilty
This solution could also be applied to the brake, but I've purchased the Ricmotec load cell, so essentially I now have a high performance pedal set, for a fraction of the cost, and which can be easily maintained (I'm guessing this pot is cheaper than the high end pedal sensors). I only have my pedals on the floor (carpet) and I'm sitting at the dining table on a regular chair. With this setup I have achieved four Diamond times on LHC and can easily maintain my S S ranking.
"It's not pretty, but it works", said......... every engineer in history!
I hope this helps anyone who's G29/27/25 pots are dead.
Notes:
- If you're on PC or play any game with calibration settings, you don't need this solution. Just install any regular pot and calibrate it accordingly. GTS doesn't offer calibration of the zero point, so that's why we need zero ohms at the start of the pedal travel.
- I also extended the earth wire so it wasn't tight when the wires are pulled out of the housing.
- I chose to orientate the electrical connections towards the inside to (hopefully) avoid physical damage. Alternatively you could build a protective cover, but in reality the exposed pot is not as vulnerable as it first appears, because it's made for heavy industrial applications. Sweet!
- The pots of all three pedals are connected together in parallel (overall resistance), so the original 3 x 10k pots appear to the wheel as 3.3 k when all connected. This is not massively important but it's not ideal to increase the circuit current continuously which might shorten it's life (5.1k in lieu of 10k would give a total of 2.52 k when connected in parallel). I had already removed my clutch anyway because it's pointless in GTS (and I stole the pot for the accelerator - it lasted less than 2 months). This means my overall resistance is 3.38k which satisfies my OCD. If you do this be sure to insulate the connectors so they don't touch anything. I used electrical tape because it's doubly satisfying to include electrical tape in all projects :-) Also I broke one wire on the clutch pot when pulling it off violently, so I had to twist the wire back together because the wheel wouldn't turn on at all with the broken pedal wire.
- Since this solution uses the plastic housing to mount the pot, you would need a different solution for rig mounted or inverted pedals. If you're that serious, you'll find a way to mount the pot, and please send me photos. I'd like to reverse mount my pedals because the load cell brake works better when pushing on the very end of the pedal. Next project :-)
- The Ricmotec load cell brake also requires some modifications to work well with GTS, so if you go down this route, message me.
- I've tried to be thorough but if I've missed anything, let me know.
- Anyone who uses this solution is contractually bound to buy me a beer, if I ever meet you in person.
- Mudda Chod is not my real name.
