I dont get it why DD wheels using 20, 25 or 30 Nm

[Deleted member 963434]

I think about simracing community is more like simp community, they swallow everything, everything what devs say, what prices they make for game, prices for stuff. i mean i saw real life quick releses for real cars cheaper than those yo can buy from sim racing sites for your sim racing wheel xD
But im not talking about it, i want to ask why DD wheels using even 20 NM?
I mean OSW DD wheels build on mige 130ST-M10010 are always 20 Nm wheel. And i dont even mean why would anybody use 20 Nm as no real life car can have wheel so strong resistance, not even car without power steering. I droven opel corsa without power steering and i tell yo its strong to turn when standing, or at low speeds but when speed increases it goes lighter, and when i set my DD on 20 nm i think this non power steering corsa can output like 10-15 nm when standing still at max..
But i dont mean why would somebody use 20 nm on them wheel, as even car in real life than would give you such strong resistance dont exist. but what i mean i checked just from curiosuty fanatec dd1 and dd2 recomendations for settings for AC and i saw they recomend using 50% FFB in wheel and 50-60% in AC.... so wtf? i think? why as even fanatic released wheel that can output 20 nm and they straight away recomend to use it at 50% xD so why is it 20 nm then not 10 nm?
also i was wondering how OSW building around MIGE 130ST-M10010 guys wound that them wheel have 20 nm as i myself own this motor and i checked official spec at mige site and this specific motor MIGE 130ST-M10010 cant even output 20 nm, but it has 10 NM constant/holding torque (that it can hold at 10 nm and force be same) or it has peak torque of 15 NM (that it can shoot 15 NM force but not hold it for long)
So my final question it why TF? them building OSW around mige 130st-m10010 tell its wheel has 20 nm as its motor yo can check at official site not even outputs 20 nm by itself...
i dont get it...

 

[Tom_Hampton]

Still for a sim I think it would be nice to have a safety feature that allows you to load up the wheel in corners and gives you plenty of detail, but that dampens out any potential wrist breaking forces.

I'm not saying to make the forces go away completely, I'm just saying it would be nice to have something like dynamic range control with a high range where there is an exponential curve approaching a predefined limit.

Oh....I agree. I was just countering the argument that iRacing isn't "realistic" when it comes to impacts---ie, that wheel forces aren't that bad. They most certainly are. Ok...iracing isn't realistic....but, that's because the simulated forces in that scenario arenot strong ENOUGH. But, as you point out....I don't want the risk of breaking my wrists in a game.

Same thing with Tactile. I don't really need to have my tactile units put out a signal proportional to 20g just because I have to gain turned up to increase low=end sensitivity. A ClipAboveThreshold would be nice. I killed three exciters hitting a wall in a nascar truck at Daytona. Mostly because I'd tuned the tactile for road-racing the MX-5. G-forces are a little different between those two extremes.

All that said....maybe that would clean up some of the crap driving, if there were some real skin in the game. "That's gonna hurt" is a real deterrent. No joke. Give all those demolition derby drivers 50NM wheels with no clipping---and duck tape their hands to the wheel. go ahead...crash into me. Lessons will be learned.

 

[wolit]

Specifications of the Mige motors can be downloaded here:

https://granitedevices.com/w/images/3/3a/Mige_servo_motor_catalogue.pdf

As you can read, the peak torque of the Mige 130ST-M10010 is not 15, but 20 NM.

The topic is overlooked, generally speaking, because it's not as easy as it looks at first glance.

First of all, the holding torque isn't that important, because the highest torque levels are experienced while driving only for brief moments --> they are only needed to communicate to the driver bumps, irregularities, surface changes and eventually collisions.

Secondly, it all obviously depends on the diameter and weight of the rim in use.
The assertion that everything above 10 NM is overkill is only correct when using just 28 ~ 30 cm rims (open wheelers / GT / go karts).
Obviously, when using huge and heavy rims like the TM Sparco 383 or the Moza CS, a lot of detail gets lost. That's due firstly to Newton's 2nd law: F = M * A (A = F / M --> if the force does not change, a higher mass implies forcedly a smaller acceleration --> a wheel that accelerates slower is less able to communicate details, aka less precise); and secondly to the wider diameter itself (think about the difference which exists between loosening a bolt with a short wrench and with a long wrench).
This is also generally speaking the reason why in reality a small and lightweight rim is used on sportscars: in order for the driver to get as much detail as possible.

So, basically, long story short: if you want to use huge and heavy rims (not just for rallying) without loosing fine details, you forcedly need - at least - 12 NM of torque. Torque is of course not a measure of how "good" a DD system is; but it's of course a measure of the freedom that the system provides in using every kind and size of rim.
Typical examples are the Fanatec Podium DD1 and DD2, which are still considered better than entry level DD systems, even though they produce a torque ripple - noticeable at lower speeds and when stationary -, which is absent on more modern entry level DD bases.

Finally it's also important not to forget that high end systems use metal quick releases (and often also full metal rims) which do add further weight to the rims (in return for stiffness).

So please think before speaking.
And above all, don't lucubrate about a topic if you don't have even the basics of the necessary knowledge to do it.

 

[Enzo Fazzi]

use metal quick releases

These are in the center, their extra weight is not that big of a deal.

 

[wolit]

These are in the center, their extra weight is not that big of a deal.

of course that's also true, but not completely.
Basically, the closer to the center the additional weigth is placed, the less negative effect on the moment of inertia (m * r^2) it has. Correct... But this negative effect may only be totally canceled if all this additional weight is located exactly in the center (r = 0), which is physically impossible.
Hence, if a 200 gram spacer and a 500 gram quick release are added to the hub, a certain amount of accelaration gets lost anyway (if the torque isn't increased).

 

[Enzo Fazzi]

of course that's also true, but not completely.
Basically, the closer to the center the additional weigth is located, the less negative effect on the moment of inertia (m * r^2) it has. Correct... But this negative effect may only be canceled if all the additional was located exactly in the center (r = 0), which is phisically impossible.
Hence, if a 200 gram spacer and a 500 gram quick release are added, of course a certain amount of accelaration is lost.

I never said they have no effect, just that they have very little effect (to the point where on a lot of rims with heavy grips, it can be considered negligible)

 

[RasmusP]

J = m*r²
QR + spacer:
700g, 4cm
= 0.7 * 16 = 11.2

50g heavier rim grip:
50g, 16cm (32cm rim)
0.05 * 256 = 12.8

That's having a QR and spacer vs air though.
You won't get a QR+spacer below 200g...
Then it would be 200g, 4cm = 0.2*16 = 3.2

11.2-3.2 = 8.0

So making the outer rim slightly different already has 50% more impact than making the QR + spacer out of metal vs composite material.

Changing the rim size from 32cm to 30cm with a weight of 300g for the whole outer rim:
0.3 * 256 = 76.8
0.3 * 225 = 67.5

Difference = 9.3


Do whatever you want with that data

 

[RCHeliguy]

Theoretical vs Noticeable....

Reminds me of a question in college.

There are two trains heading towards each other 500 miles apart.

One train is going 60 mph. The other is going 80 miles an hour.
A bird flies back and forth between the two trains at 100 miles per hour.

How many miles does the bird travel before the trains meet.

The answer wasn't important. How you solved the problem was what mattered.

Supposedly a more theoretical mathematics minded person would create an infinite series converging on a value and an engineer would turn it into a simple time rate equation.

In engineering we frequently tossed out "insignificant" parts of equations.

To my mind we are debating insignificant values.

 

[wolit]

yes, that's because the moment of inertia increases quadratic with the radius.
You should always use meters for length; your calculations are only correct because you used cm everywhere.
Then, the moment of inertia is defined as the integral sum of every point which the object is composed of.
What you have done here is considering the whole weight as being concentrated in one single geometric point.
But all in all, that's Ok just to get an idea of the situation.

 

[Eric Rowland]

lucubrate

I learned a new word today ... thank you ...