Load cell brake progressively less sensitive

[conticreative]

I recently installed a new Load Cell brake from Apix electric.

When I first received it was very sensitive. So much so that I had to recalibrate all my sims to avoid pressing 25% brake just by resting my foot on the pedal.
I also used the Bodnar calibrator to build in a 10% dead zone in the padal because of the same reason.

As I Have been using the pedal it has obviously gotten less sensitive. To the point where I had to take out the dead zone and recalibrate everything again.

Now in GTR2 and Race 07 I Have the problem that it takes a lot of effort to brake at all and to reach full brakes I am afraid I'll have to push so hard I'll drive the pedals through the floor.

I am wondering if this is normal but above all, I would like to find a way in Race 07 and GTR2 to increase pedal sensitivity (in game is all already maxed out).

Iracing and NKpro are fine since they Have internal calibration but GTR2 and Race are starting to be a problem and if it continues to "lose power" I'll soon be unable to brake.

[ermax]

I have the same problem with my loadcell but it isn't the loadcell that is the problem. It is the rubber that sits between the pedal and the LC that breaks down with time which puts less force on the LC as it breaks down. I am not sure how the Apix unit works but if there is rubber in it, it is most likely the rubber loosing it's stiffness.

[tINKER]

I have a sim probm. I notice with my Club Sport Pedals after they been used for an extended period, they are very stiff then loosen up after use but they stiffen up again the next time I use them. I thght it was all in my mind or that my left leg was just getting stronger :laugh: as the race went on...:-).

[johnw]

I had a similar problem with mine, but it wasn't due to the rubber block - I tried various different replacement blocks after the original disintegrated and the sensitivity problem was the same.

The difference with mine was that if I unplugged the pedals and plugged them in again, the sensitivity would return to normal...for a while. The only way I found to fix it was to connect the pedals to the Leo Bodnar adapter (http://www.leobodnar.com/products/DFPG25conn/). Once calibrated with the adapter the sensitivity remained constant, no matter how hard I stomped on the pedal :-D

[Christopher Snow]

I've been running a hydraulic pressure brake for more than four years now (my own DIY version), which operates using the same principle as a mechanical load cell, in that the progressive output to the PC* is controlled by how hard you press on the pedal, not in any way by measuring the movement or displacement of the pedal pad or arm itself.

[the pressure sensor output is fed to a "Plasma Lite V2" manufactured by the now defunct Canadian company "Beta-Innovations," but I believe one of Leo Bodnars boards would do the job too]

I think one of the bigger advantages of going "hydraulic" is that it's probably less sensitive to damage from overpressure than is a dry load-cell brake...or at least this one seems to be.

I believe it's true that a mechanical load cell can be damaged or ruined by overpressure of perhaps 50% beyond it's output rating...150 lbs in the case of a 100 lb load cell.

In my case the pressure sensor range is 0-100 PSI , I've actually TRIED to damage it with over-pressures well in excess of 200 PSI...perhaps even beyond 250 PSI but it's just as solid now as it ever was.

That said, the version I'm currently racing with sports almost NO physical movement at all once once the slight amount of loose play is taken up. There is all of 3mm of measurable movement at the pedal pad, and it isn't until that small movement occurs that I reach the pressure zone and can begin to build up pressure and braking power.

It's certainly quite drivable this way, but it isn't completely realistic, I grant you, in that even the "tightest" and most well built race cars still do necessarily sport a small bit of pedal pad movement as pressure is increased on the brake pedal--it's an unavoidable consequence of having four rubber brake lines in the hydraulic circuit (whether they are metal braided lines or not)...and perhaps of having compressible rubber seals in the calipers or drums too.

In order to provide a bit more pedal pad movement I did build a second version which incorporated a section of expandable tubing into the hydraulic circuit, and I think I will ultimately come to use such an "expansion" chamber in whatever version I build next...but unfortunately the first time I tried it I simply had too large a chamber (or perhaps I did not bleed the circuit of air as completely as I had intended) before giving it a go...so I really couldn't build up any pressure at all. :D

Ah well, experiment #1 results in failure. I'll give it another go soon and will let you know if I get it worked out.

Meantime, the "full stiff" version still works a treat, and it's just huge fun to use.


Christopher Snow

[conticreative]

I stupidly posted again about this topic in the GTR2 forum, since GTR2 is really the sim that is most affected by this. iRacing has it's own calibration and can overcome the loss of sensitivity, but I am at a point in GTR2 where I am not braking as hard as I need to unless I really stop on the brake.

In other words, I have to brake so hard I am losing "modulation".

I too thought it may be the rubber pad. In fact, I can test that easily by just replacing it. I have 2 brand new ones I can mount. I will let you know about that.

However, I am betting that's not the case. I inspected it manually and it seems as strong as it ever was.
Christopher, would you be interested in sharing your hydraulic brake plans?
I would love to build my own as well, and I even thought about getting a motorcycle rear disc brake and rig my own, but if you have a less messy idea, I am all ears.

Making it too stiff is certainly an issue, but if one uses a realistic setup there should be enough play to obviate that. And it's all a matter of getting used to it anyway. Using rubber like my load cell does may work too.

[Christopher Snow]

Certainly, cc, but I don't have time at the moment.

I did find the old photos of the original testbed, plus the failed "expansion chamber" version yesterday...and it's really those that will have to suffice as plans (since I really haven't bothered drawing up anything formal--you'll understand when you see it).

In the meantime, I was just sent a link to a pressure controlled brake option (commercial) for use in the G25/G27:

http://www.perfectpedal.com/whispepe.html

The description suggests this offers some tweaking features, probably similar to what I'm hoping to do. Don't know yet of anyone who's running one, but maybe someone else might?

More later I hope....


CS

[ermax]

I have a mechanical stop on mine so I can press as hard as I can and it still doesn't get a full reading on the LC. So I never run mine past it's limits. Probably only really use it up to about 85%. Most of the commercial rigs have mechanical stops though.

[conticreative]

I have never used the perfect pedal, but a couple of my friends have and they report that it was too stiff for them. My guess is that they didn't take the time to calibrate it properly.

I was actually seriously considering it, but $250 is still a good chunk of money for a brake pedal. If I get a windfall I may buy it but until then I want to try to make my own if possible. Or try to fix my load cell.

[stagman]

In my case the pressure sensor range is 0-100 PSI , I've actually TRIED to damage it with over-pressures well in excess of 200 PSI...perhaps even beyond 250 PSI but it's just as solid now as it ever was.

That said, the version I'm currently racing with sports almost NO physical movement at all once once the slight amount of loose play is taken up. There is all of 3mm of measurable movement at the pedal pad, and it isn't until that small movement occurs that I reach the pressure zone and can begin to build up pressure and braking power.

It's certainly quite drivable this way, but it isn't completely realistic, I grant you, in that even the "tightest" and most well built race cars still do necessarily sport a small bit of pedal pad movement as pressure is increased on the brake pedal--it's an unavoidable consequence of having four rubber brake lines in the hydraulic circuit (whether they are metal braided lines or not)...and perhaps of having compressible rubber seals in the calipers or drums too.

In order to provide a bit more pedal pad movement I did build a second version which incorporated a section of expandable tubing into the hydraulic circuit, and I think I will ultimately come to use such an "expansion" chamber in whatever version I build next...but unfortunately the first time I tried it I simply had too large a chamber (or perhaps I did not bleed the circuit of air as completely as I had intended) before giving it a go...so I really couldn't build up any pressure at all.
I too had run a hydraulic setup but only used it for the pedal feel. I never got around to developing it further due to various reasons.
-Cost of sensors was too much, with or without amp. I prefered a 0-5V one to do away with amp.
-Win7 doesn't recognise my wheel/cockpit setup properly so a lot more $$ and time involved.
-Playing with real cars gives me more bang for the $, so guess where my attention and dosh goes to?

To get it all working as I want it would require a (2nd hand) wheel that works in Win7 and a decent sensor w/wo
amp. My guess that alone would cost me in the region of 200+ euros. Then there is the time involved. I cannot justify that for the little time I would spend using it. Not now at least anyway.

You mention using a 0-100psi sensor. Have you measured the attained pressure in your setup? I did once and found I was getting 220-250 in the line when braking hard. Getting a sensor to cope with that proved expensive.

Setep I have still has a pot meter operated via linages for the signal. For me the oily bits were for the feel, which wasn't easy to get right. Pedal travel needed to be around 10mm, if not more as older racing cars (and many new ones too) have non servo assisted brakes which generally give a longer travel You also need to push a lot harder than your average modern road car brake pedal.
Tried tuning the feel with a flexible polyurethane tube - didn't work as it bubbled and lost pressure.
Tried tuning with different fluids - didn't work. Don't bother with water or vege oil.
Tried tuning with varying ammounts of aair in system. Didn't work.
I eventually got a decent pedal by placing two polypropelene blocks between the caliper, with a piece of 3mm diameter wire between them. This wire was jammed in on the edge, way off the centre line of the pistons, in order to allow the PP blocks to flex slightly. Just enough to give the right pedal travel and feel.

[Christopher Snow]

The attached photos of my very simple (and fairly ugly) brake controller and raw plywood testbed were originally posted at the (now-defunct?) site "Race Sim Central" back in 2008.

I think I had been running various versions of this rig for at least two or three years by then, which means I probably put it together for the first time back in 2005 or 2006. I know I used in when I raced N2003 mods online (GTP, Trans-Am, and the Ferrari 330 mod).

A more comprehensive version was first built (as best I remember) by a Scandanavian GPL driver by the name of M(arcel?). Lindqvist perhaps as far back as 2001. I remember that his system consisted of a used, Mercedes Benz steering pressure sensor (for system output) operating over the range of 0-100 lbs or so...a brake master cylinder, a single brake caliper, a system pressure guage, pedals, hoses and associated electronics to capture the sensor output and convert it to something usable by the PC (and specifically GPL in his case). All very much "cutting edge" at the time.

I felt it would work reasonably well too if I simply mounted a similar sensor directly to a master cylinder, while bypassing most of the rest of the hardware. It did.

It's true my own unit does not sport enough "sponge" in the pressure range, but it still works very well in use--I'm not handicapped in any way, as far as laptimes or driving ability are concerned.

The 0-4v. output from my own 0-100 lb sensor interfaces directly into one of the eight analog inputs on my Beta-Innovations "Plasma-Lite V2" USB interface card...and then directly into the PC. No amplification of any sort is required (on any of my pedal channels).

In the case of all three of the pedals I'm currently using, the input feeds into one of those analog channels...and the two that are potentiometers function exactly like the one that is the pressure sensor, at least as far as rFactor is concerned. They are completely indistinguishable from one another inside the sim.

As can be seen, my (very crude) kart type brake pedal offers only marginal "leverage" at best to the master cylinder (and sensor) input...so I must push with 100 lbs of force to make the sensor read 85 lbs, etc (this is a matter of the distance from the pedal pivot to the pedal pad divided by the pivot to MC output distance.

No, not pretty, but quite functional.

Also seen is the "failed" experiment adding in an expansion chamber (the orange hose added to the second testbed--the hose was not braided, and simply expanded too much...or had an airbubble I failed to remove..or perhaps a combination of both.

What's needed is to drill and tap the square "plug" on the opposite end of the tee with a bleed nipple, so as to ensure removal of compressible bubbles. I'll get round to it someday, perhaps (and in the meantime, it's still pretty bulletproof as it is).

Hope it's of some interest...if not outright humor. :-P

[EDIT: Trouble ATM attaching jpgs, but I'll try again shortly--it seems I will have to downsize them first]


Christopher Snow

[Christopher Snow]

I've reduced the filesize of all the jpegs so they are smaller than the 150.0 KB filesize limit, but each attempt to upload even one eventually returns an "Error 500 - Internal Server Error"* (upload attempts appear to time out after ~ 5 minutes). I THINK this indicates a problem at the NoGrip end of things, and if anyone knows for sure (or knows what else I might be doing wrong), I'd appreciate any help. Thank you.

Stymied, in the meantime.

[* "The server encountered an unexpected condition which prevented it from fulfilling the request"]


CS

[conticreative]

I got the same error a couple of times. If I remember I had to change my pics to jpg instead of PNG.

By the way, just recently my load cell brakes returned to their old strength. I am not exactly sure how that happened but suddently it was braking a lot better.

Since then I found that if I press on the pedal and I snap it (let it return to the up position on its own) it resets and it brakes a lot better.

In fact, yesterday in a race at SPA with a Mosler I started losing my brakes big time, so I snapped the pedal and I locked the wheels and almost wrecked the next time.

Eventually it sorts of adjusts and works best. It could be that I need to calibrate it more often and make sure I disconnect the cable/restart. I am not sure what did it but at least I now know that the sensor itself works. It may even be a mechanical issue . At least, I am able to make it work and eventually I'll try to solve the "fading" issue (how realistic though).