G27 brake mods

[stribbeck]

Hi all

Are these any good? Looking at getting the rally version

Brake Pedal MOD “Rally/GT” [Logitech G25, G27, G29, G920] (PC) | 3DRap

This MOD simulates a load cell on the brake pedal. It makes the pedal progressively harder, more realistic. Compatible with Logitech G25 / G27 / G29 / G920. Watch the video that you find at the end of the page. The original spring always opposes the same force to your foot, whether you are...

www.3drap.it

Thanks

 

[Deleted member 1234936]

Go to a local plumbers merchant/hardware store (mine was wilkinsons), and purchase a pack of Tap Washers, Think I paid a pound for five, they are about 4mm thick rubber with a very small hole in the centre. Strip you brake pedal as if replacing the spring, and place the washer at the bottom under the spring.

This gives the pedal press much more controlled resistance and gives the feel of a hydraulic pedal, like a real car.

Although my g27 sits unused due to upgrades, this was the best mod I ever did, and I could trail brake a treat.

A couple of side notes, you have four spare washers, so could play with hole size to suit, although I never did, and Don't be tempted to just block the pedal hole up, it's like pressing on a solid rubber ball with no feel.

hth

J

 

[GeekyDeaks]

Hi Scott, that sounds amazing, what other bits would I need?

You'll need some hardware to construct a plunger and an amplifier (the load cell is just a piece of metal which changes resistance by a tiny amount depending on the force applied, so you need something to convert this tiny change into something measurable).

I have an example of what I used for the plunger:

@Locoblade came up with a pretty neat variation

For the amplifier, the simplest option is to get the leo bodnar board. @Locoblade took the time to put together a shopping list! https://github.com/GeekyDeaks/g29-load-cell/issues/1#issuecomment-626574665

@Neilski ^^

I probably recommend that approach, the only reason I didn't do it was because I didn't have a PC and was using my G29 on a PS4 so I needed the amplifier to replicate the OEM pot. I have since bypassed the wheel with an Arduino and it's made quite a noticeable difference.

One final thing to note. You need a *very* sturdy setup. You will be applying something in the region of 20kg of force to the pedal, so if you are on an office chair you'll find you just end up pushing yourself back!

 

[Neilski]

@Locoblade took the time to put together a shopping list!

Nice one, ta! The bit I'm still slightly scratching my head about is the mechanical bits - did you get the M10 stud+nuts+washers online or did you just have them lying about?

 

[GeekyDeaks]

I already had the hardware, although I think I bought the low profile nuts. You should be able to pick them up in any hardware store, but the trick is to make sure you have some adjustment to tweak the feel. I re-used the little rubber block you get in the G29 as the 'hard' secondary part of the pedal travel and the spring was used for the initial application to try and emulate the tiny bit of travel to get the pads to move into place

 

[Neilski]

You should be able to pick them up in any hardware store

Doh, yes. I'm so used to buying everything from Amazon recently that I have forgotten that real shops exist!

One other thing I'm thinking about, and this is probably a "having cake and eating it" thing: I would love to be able to have a hard stop on the travel. That way I can be sure I'm at the limit, and that a slight backing off from there will reduce the brake signal to the game. Without a hard stop, I'm fearing that I'll be inconsistent, and unable to reliably trail-brake. (Worse still, the way the G27 electronics work, I'll be at risk of adjusting the "max braking" calibration point each time I brake really hard. The only way I can think of to avoid that would be to adjust the gain to make the voltage clip, which might be a worse issue anyway.)
Achieving a hard stop with a load cell is probably somewhere between tricky and impossible though.
Any thoughts?

 

[GeekyDeaks]

You might be able to workaround the self-calibration by ensuring the amp clips at Vcc just beyond what you consider 'full' braking. Then you can just press the pedal really hard on start-up

EDIT: properly re-read what you wrote originally and realised you already suggested that!

Ok, from experience I have found it doesn't seem to matter, you quickly learn how hard to press the pedal. Mechanically it's going to be tricky, but I guess all you really need is a means to stop the pedal from travelling, so maybe you could glue in a few washers between the pedal base and the bottom arm of the pedal? Would make minor adjustment a little tricky, but you probably only need to do it once.

 

[Neilski]

Ok, from experience I have found it doesn't seem to matter, you quickly learn how hard to press the pedal.

Yeah, I think I'll be banking on that!

glue in a few washers

Mmm, intriguing idea. Might look at that as a backup option if I don't get the feel of it quick enough.

 

[GeekyDeaks]

I cannot stress how important the configuration of the plunger is for the 'feel' of the pedal. The loadcell hardly moves at all, maybe ~0.8mm. My initial attempts used some plumbing washers, but it felt incredibly hard (even though my friend told me it felt like a real race pedal), so I ended up softening mine by using the rubber block in the G29 to give a more squishy feel, which is funny considering the block is supposed to make the G29 feel firmer!

 

[blekenbleu]

Here is a hint for mods using 50Kg body load cells;
many are sold in sets of 4, offering opportunities for better matching a pair.
For example, if load cells are labelled 0, 1, 2, 3, then testing showed
no-load differences of 1, 2.4, 1 mV between cells 0 and 1,2,3, respectively.
Luckily, 1 and 3 difference measured only 0.1mV, where it could have been nearly 2.

Reading changes with moderate forces are only about 1mV for the same (6V) excitation;
using the most nearly matched pair frees more range from zero for useful signals.
This is also a good time to label which red wire gives positive signal
for a black+white pair connected to positive excitation..

 

[blekenbleu]

Have already bought the load cells (damn, but it's hard to get them to register anything on a multimeter

For the truly frugal (and lazy) among us, a $5 INA333 module works,
although the included on-board gain pot is erratic and should be shorted for 1000x gain.

More gain can be obtained e.g. by jumpering the 100 Ohm ("101") resistor by 33 Ohms or so.
Load cells are connected between the 3.3V and adjacent ground pin.
If load cells are used in a bridge (so nearly no difference between VIN- and VIN+),
then VREF should be grounded.
The board defaults VREF to half of 3.3V using a pair of 10K ("103") resistors.

 

[Neilski]

For the truly frugal (and lazy) among us, a $5 INA333 module works

Thanks, might try that. I already have a bunch of MCP6002s that I bought for something else, and was planning to see if I could make them work (they might be utterly useless though ).

 

[blekenbleu]

I already have a bunch of MCP6002s

Rail-to-rail with appropriate supply voltage and 1MHz gain bandwidth should work.
Personally, I try to limit surface mount component aggravation.

 

[Neilski]

surface mount

I never use 'em either (not so far at least). Mine are all DIL. Somewhat easier to solder