Has anyone tested how weight and rim size affects force feedback?

Discussion in 'Sim Racing Hardware' started by Elaphe, Jul 6, 2018.

  1. Elaphe

    Elaphe

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    I have a TS PC Racer and I've tested 2 rims. One is 32 cm and weights only 850 gr. The other one is 33 cm and has button plate attached with a resulting weight of 1.2 kg. I don't know if it's a subjective impression, but I think the larger and heavier one turns a bit more slowly and reacts with some delay. As regards effects, I have not noticed much differences, but I must say I'm not too sensitive in that sense. Could it be that the increase weight adds some inertia and that's why I feel it a bit sluggish. Do you think that weight is more crucial than the rim's diameter or viceversa? Have you noticed differences between rims of difference sizes and weights when using more powerful systems such as OSWs?
     
  2. RasmusP

    RasmusP
    AC Stuff and G27 help Staff

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    Didn't test it but I can explain the math behind it I think :)
    Inertia of the rims is:
    J = mass * (r1²+r2²) / 2
    Let's say they're both 2cm thick, the bigger rim weights 900 gr. and the Plate is a square with 20x20 and weights 300 gr.

    J_Rim32cm = 0.85 * (32²+30²) / 2 = 820
    J_Rim33cm = 0.90 * (33²+31²) / 2 = 920
    J_Plate = 1/12 * 0.30 * (20²+20²) = 20

    So the 32cm Rim has an inertia of "820" and the 33cm+Plate have an inertia of "940".
    Making the relation of the inertia 100% to 115%. 15% aren't much but you might feel it. I mean, we do feel 14% lowered FFB settings, don't we? :)

    Now let's compare the same weight with 5cm difference:
    J_Rim32cm = 0.85 * (32²+30²) / 2 = 820
    J_Rim37cm = 0.85 * (37²+35²) / 2 = 1100

    Now that is quite a difference! 35% to be precise.

    So the responsiveness is like a 35% reduced FFB slider. The next problem is that your hands add a lever too, making the FFB 'weaker'.

    This is why you shouldn't replace the steering wheel of your car with a too small one. The forces you need to overcome will increase quite a lot!

    Hope that all is making sense and helpful :)
     
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  3. Hiro Abe

    Hiro Abe
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    Okay... my brain hurts. :O_o:

    Seriously, though... it just makes sense to me that a lighter wheel will be more responsive. Now, I think the usual dd base can handle any wheel regardless how weighty. But when talking T-Master, Logitech bases, I would think you will feel a discernible difference. I THINK I feel a difference with my Fanatec McLaren wheel vs the CS Forza wheel I had. I find the CSW base is pretty strong though so I'm guessing the differences are minimal.

    Total speculation on my part.:p
     
  4. RasmusP

    RasmusP
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    The Forza wheel is a full rim and the McLaren only the "2 grip rectangle" correct?
    Then it makes sense as when you look at the inertia formulas it's, even when they would weight the same:
    1/2*blubb for full rim and 1/12*blubb for the rectangle!

    Inertia is all about how far away from the rotation axis the mass lays. Do a pirouette swing with arms wide open and then pull them towards your body, then you'll see the big difference of energy. And yes, my brain already hurt a lot as I'll have an exam with exactly this stuff on Tuesday :rolleyes::roflmao:
     
  5. Hiro Abe

    Hiro Abe
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    Correct though I believe the diameters are the same. The weight, however - the McLaren is much lighter... relatively speaking. But to your point, take their - Fanatec's - F1 rim which is definitely smaller in diameter and that thing felt very responsive and quick. Especially, compared to the RSR wheel I had at the time.

    Interesting stuff!
     
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  6. Elaphe

    Elaphe

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    What makes me think that weight is important, no matter how strong the motor is, is the fact that some brands make very expensive carbon fiber rims with the aim of getting strength combined with ultra light weight, so if a driver of a real car can notice a difference, I suppose we all should do.
     
  7. Hiro Abe

    Hiro Abe
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    Maybe I'm wrong but I've always considered things like carbon fiber wheels lend to overall weight savings of the vehicle. When talking pure race vehicles in general, builders look at everything in regards to weight saving. Even if it is only a gram or two, everything is scrutinized to be as light as possible but strong enough.
     
  8. Furnace Inferno

    Furnace Inferno

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    Weight makes no difference on a DD wheel because the motors are already rotation speed limited given they are designed to casually spin at 1500RPM+ 24/7 which would literally break you if allowed to spin that fast.

    I have seen graphs of it being tested with different wheel rims specifically on the Fanatec clubsport wheels but not sure where those are now. Maybe try searching RFR wheelcheck?
     
  9. HoiHman

    HoiHman

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    The size, weight, position of the handgrips are all a big factor in how a wheel performs. This applies to mid-range wheelbases, but also to the high-end direct drive wheelbases.

    A DD wheelbase is strong enough to make sure that the larger wheels give more than enough feedback, but even with powerfull solutions as the AccuForce, i can feel the difference between a heavy and a light wheel ( with equeal size)

    Just a 10mm difference in diameter can give an entire different experience, but bigger handgrips or handgrips that are tilted 5 degrees inwards also are a gamechanger.

    I have learned the craft of building my own rims and currently a collection of 13 different wheels.

    [​IMG]

    And yes every one feels quite different
     
    Last edited: Jul 6, 2018
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  10. Andrew_WOT

    Andrew_WOT

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    There is a difference between heavy and light wheels on OSW. While FFB strength is the same, heavier wheel feels more sluggish as if having extra dampening. Makes sense as it needs to overcome inertia when quickly changing direction.
     
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  11. Neilski

    Neilski
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    Weight may make no difference to the maximum rotation speed but it makes a very big difference to the angular acceleration you can achieve. (Or to be more precise, the moment of inertia, not the weight.)