Question about load cell brake pedals

Discussion in 'General Discussion' started by Marc Collins, Nov 18, 2015.

  1. Joe

    Joe Registered

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    OK, I will email him. thanks. Sorry I have no experience on real GT cars. Since I could not get "reasonable" travel distance on the pedal, I thought it might be not realistic. The site of HE pedals offers HE brake pedal curves, but not HPP site. Anyhow, there is no way for me to "objectively" verify either. All depends on some ones real-life experiences and their subjective view.
     
  2. smbrm

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    If you have an unattached pedal set braced against the wall and your chair keeps backing away from the pedals the next simple solution is to connect the chair to the pedals. I did this with my G25 load cell mod pedals by mounting them to a board. I then had a second board that would connect with the pedal board. This second piece was placed between the pedal set and the chair. The end at the chair was shaped like the top of a "T". Two of the five office chair wheels would be locked on the pedal side of the "T" preventing the chair from moving away from the pedal mount. Work great, but not as rigid as as a rig. I now have a home built wood rig which is much more appropriate.
     
  3. Joe

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    Yes, I agree. I read online now. It seems most believed that Hydraulic brake pedal is more realistic than loadcell, due to the fact that real brake is hydraulic. It is stiff because of small compressibility of fluids. So travel distance is not an attribute to measure. In real race car, the brake (fluid) lines are pretty long, and fluid reservoir is large too, hence some travel distance will be seen. The bump rubbers play the role to model such stiffness and travel distance. I will, as suggested, email Mark to ask for small black bump rubbers....
    Ideally, no bumper rubbers, but with very long fluid line and open loop design with reservoir. That will be just like real brake! In this sense, the Frex pedal design may be most realistic (?) Well, who knows actually feel. But in theory it seem to be:
    http://www.frex.com/gp/pedal/
     
    Last edited by a moderator: Nov 19, 2015
  4. Panigale

    Panigale Banned

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    There is no shortage of schools out there that would be more than happy to take some of your green so you can develop your own subjective view of what a brake pedal should feel like. I highly suggest you give it a try.

    The brake pedal actuates a piston, buy using softer bumpers the piston is able to move further while using less force to move it, hence more pedal travel and less effort. With the kit I was provided you can get duplicate say a 911 or Z06 with a good amount of travel all the way to F1 stiff with very little travel if that is what you need. The OOB kit does not allow for duplicating the feel of an SUV brake pedal or Hertz's finest Chevy Cruze, which sounds like what you may be going for. The travel distance of a properly bled brake system in a real car with performance brakes is (and should be) very short. Old expanding soft lines and old calipers with sticky pistons can affect this as well as not properly bleeding all the air out of the system. Heat soak with using non racing brake fluid can be an issue, etc. and I'm sure there is likely a dozen more.
     
  5. Emery

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    Oh, heat soak is an issue even for race cars. NASCAR drivers at roadrace tracks can often be seen giving their brake pedal a test pump to make sure the pressure is in place before they HAVE to use the brake. Having your pedal go soft is no fun!

    "I'm still waiting for simulations to increase pedal travel due to worn brakes or boiling fluid"
     
  6. smbrm

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    I am assuming that everyone appreciates that the brake fluid is for transferring pressure. It is just a column of oil transferring pressure. Unless you have a recirculating brake fluid system the fluid only moves a minimal distance based on its limited compressibility and in a correctly functioning system the brake fluid in the master cylinder never gets to the caliper. The master cylinder only replenishes the front end of the fluid column. There are recirculating systems in some applications( Wilwood I think has one). The idea being to recirculate the fluid so it can be cooled and its properties optimally maintained.

    The other thing we forget about non race car brakes is that vacuum assit power brakes on most street cars make them feel quite different from non power racing brakes. Street car brakes from the time before power brakes were quite stiff in comparison to power brakes. I just thought I would mention this as it never seems to come up in discussions about how stiff racing brakes should feel when wondering about how stiff is unrealistically too stiff or not.

    Feel free to ignore if intuitively obvious!
     
  7. coops

    coops Banned

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    You buy them because they are 10 times better than using pedals without a load cell and they do improve your lap times that has been mentioned on many forums. But seems you're more worried about if they move. To be honest you don't have to jump on them to get them to work and yes i prefer them to be mounted. As i have a racing rig.
     
  8. Joe

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    This is my concern, and interesting topic. I recalled one review (a few years ago) on both Emery Emond and HPP Hydraulic Pedals by asking several real GT racing car drivers. They did blind test on both pedals. But I could not find that link anymore. When I google online, I am flooded by the "Sim Racing Garage" reviews. This is how bad internet today. If some one finds that link, please let me know. @Panigale, thank you for your inputs. You seem to have some limit experience on real race car as you mentioned.
     
  9. Joe

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    funny, but interesting though! Lets look at what Fanatec website says on their V3 pedals:

    "The new vibration motor on the gas pedal can be used by games to indicate if you lose grip and should power down. The second motor on the brake could warn you if you brake too hard and lock the tyres."

    "vibration motor to simulate ABS and indicate locking tires
    Controlled by Fanatec wheels: Compatible to all games
    Dynamic control by games is possible via Fanatec Wheel SDK"

    Now see :
    "The completely new design of the brake allows to adjust the stiffness and travel of the brake pedal without using any tools."

    Not too far, if they can implement this with a new motor to dynamically change the pedal rod leverage, then DONE!
    (of course, rF2 needs to implement a "brake wear/damage" model).
     
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  10. Helium

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    You could just change the sensitivity of the loadcell itself. The loadcell signal is amplified and the sensitivity can be changed via a potentiometer. Cannot be too hard to implement a solution that is able to do that via the drivers.
    Even a software only solution is possible. In rF2 you can change the linearity of the pedal inputs. The game could just change the slope of that curve. But I am not sure if I really want stuff like fading brakes during my racing :D.

    I find the motor behind the brake pedal of the CSP pedals quite useless. Maybe I have just dumb feed but in the heat of the moment I am not able to sense any valuable input.
     
  11. Joe

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    I am itched by the V3. I owned their v1 pedals long time ago. it was crap. I like some inputs of owners on V3. Is any one here who owns the V3?

    Here is bottom line,
    1) according to the V3 spec my estimated the max foot pedal brake force is about 100lb. That is close or better than my HPP max brake pedal force I measured. (but I have no data of V3 to back up to support that. Just my estimation).
    2) travel distance and stiffness cost noting. It can be adjusted anyhow. That shall not be in the equation.
    3) load cell vs Hydraulic, the HPP used close-loop and with little fluid. I see no considerable difference or advantage.
    4) price: <$400 vs $1200.

    Update: Just saw a video on V3 strongest setting. OK, just forget what I say. I will keep my HPP.

     
    Last edited by a moderator: Nov 20, 2015
  12. Skan

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  13. smbrm

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    I Keep wondering about the use of terms when the term "hydraulic" is compared to "Load cell". Hydraulic is a transfer mechanism not a measurement mechanism. A load cell is a measurement device. A hydraulic system has to have a measurement transducer that can either be a position based transducer or a pressure (load cell) transducer. The hydraulic has to move or press against a transducer to create a signal that can be read. Obviously a position based transducer has to have some change in position for it to register. A load cell has very minimal change in position for it to register a change pressure. The transducers by themselves, while they may secondarily contribute to the feel, their primary function is measurement and signal generation.

    Feel is created by induced resistance that imparts progressive feedback to the driver. Progressive feedback should be achievable with either springs(coil wound or rubber) and/or mechanical leverage(rods & levers or piston areas) if the desired effect to be created can be defined in recreatable engineering terms. The hard part is translating the feel into precise engineering terms that can be used as a goal. The result also has to be similarly interpreted by the driver( their subjective interpretation) before one could suggest that the feel has been simulated. The feel also has to create a perceivable change in feedback(feel) relative to activation.

    Just saying hydraulic is more realistic because it is hydraulic seems an over simplification when trying to mimic the feel of brake pedal feedback of stopping resistance for a simulation.

    The development of brake feel in real automotive brakes, while now mature, is the result of much research and evolution over the years. It seems unrealistic that attempting to simulate it in a system with different dynamics would be any less difficult?

    Just some thoughts.
     
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  14. smbrm

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    I wonder if the V3 brake damper is one way or two way?
     
  15. Joe

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    @smbrm

    To me, this is very straightfoward. Because real brake system is using fluid to transfer pressure, therefore using fluid to transfer pressure on sim pedal is more realistic.
    Yes, one can use bumper rubbers and springs to simulate fluid compression. In theory, they will never be the same as fluid.

    So, my argument is that the Frex pedal (using fluid only.... no bumper rubbers, no springs) is most realistic sim pedal I can think of. That did not says with loadcell/bumper/spring is not good sim. Could be good too. But if Frex pedal did right, it will be the best I believe.
     
  16. Skan

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    My apologies. I thought You were wanting a way to make the load cell "feel real" as the hydraulics do. I thought it was about combining the two of them, of course the hydraulic part is only for peddle pressure but the load cell is the data input.
     
  17. smbrm

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    Hi Paul

    My comment wasn't directed at you, but at the gist of the discussion and other submissions referring to hydraulic vs. Load cell. My note just came after yours in the Que.

    I think what has always been required is some way of replacing what we don't have as brake feedback, things like inertia, pedal resistance against a rotating disc, whatever you can think of that may contribute to the feel of real brakes? The key though is to maximize "cause and effect" in the brake feel so that whether it's pressure or distance or whatever additional measures, the driver can appreciate the difference as it relates to modulating the end result of how fast the car slows on track.

    If HPP is astute enough to do his sums right, should V3 and GT-1 be able do the same, I would assume so given the appropriate imformation?

    Interesting, GT-1's should be in the hands of multiple customer's by now, but I haven't heard much feedback about them other than a few reviews. Usually we hear if there are things that users don't like, but when something is good, do "we" like to keep it quiet for awhile??

    I too am looking to the future for when Ap Electrix g25 load cell packs it up.

    Cheers
     
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  18. Emery

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    Brake fade is already simulated adequately. Drive the Cobra around Longford... if you've been using max braking effort on the downhill to the viaduct, then you'll get brake fade at the corner in town after a couple laps. Brake fade can be somewhat managed by using more pressure on the pedal when you realize the brakes are fading and then drive conservatively to let the brakes cool down.

    No, what I'm talking about is the loss of hydraulic pressure because you've boiled the fluid in the brakes or have worn through a set of brake pads. When that happens, then the first stroke of the pedal often goes to the floor with no effect and you have to give a second or third stroke to get any pressure in the system. Similar to driving a poorly bled brake system or, for old-timers, driving an 850 Mini with the original single-reservoir "bean can".
     
  19. smbrm

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    I guess you would have to try one and compare it to something appropriately real to determine?
     
  20. Joe

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    I will think so too. But I am not currently at that mood or crazy enough to buy the Frex to try. One fact we know for sure that HPP is not pure Hydraulic. It uses bumpers/rubbers in connecting to the master cylinder to partially simulate fluid compression. Also, it is close-loop design,which is deviated from real brake system. Good thing is it does not use spring (of which the force is linear depends on displacement, F = -kd). My Fanatec V1 used a spring inside to connect the loadcell. What a joke! HE pedals used both rubbers and spring.
     

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