Seat mover vs DBOX? No...seat mover + DBOX!
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I had a random idea last night and figured to ask if anyone had experience or an opinion one way or another.

I know people tend to fall into camps: seat mover fans and DBOX fans.  I have a seat mover (stage 4+ SimXperience) but I always keep an open mind to what is out there.  I'll admit to being intrigued by how quiet and compact a DBOX setup can be, but I'm very happy with the way my rig forces me to tighten my core (i.e. basic seat mover principles).

My question is this, could we not combine the two?  Why not have a DBOX rig, but have the wheel deck supported stationary above the moving rig, essentially creating the same type of setup as a seat mover, but using the DBOX actuators in place of the SCN5 arrangement?

Good idea?  Terrible idea?  Doesn't work because ____?  Any thoughts?

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I have often thought that combination would make for the ultimate rig. I asked Berney the following question on iRacing and this was his reply. I am glad they are playing with the concept so you never know what might eventuate.

 

 

Through your experimenting did you ever try combining a seat mover with a platform mover? I have not seen anyone try this but I have often considered what would happen if I sat my SimXperience Rig onto a D-Box system. I don't even know if SimCommander and the D-Box software could work in unison and although expensive, would that not give you the best of both worlds?



Berney wrote:


This is indeed something that we have and continue to put a fair bit of energy into. I don't think it would be fair of me to draw a final conclusion at this point, however, I can share a few of the concerns and a tidbit of background on each: 

Is a D-Box Representative of 4-Corner Independent Suspension or Pitch/Roll/Heave 


If you think of your rig as a solid axle and your D-Box actuator as a shock/tire that interfaces between the solid axle and ground, it quickly becomes apparent that you can't control the actuators independently so as to represent a 4-corner independent suspension or you would either try to tear the rig apart of lift actuators off the ground. 

To solve this, the control software calculations basically wind up giving you pitch/roll/heave or something very close to it with maybe a VERY small tactile/vibratory representation of the independent suspension movements blended in. Any remaining tactile effects wouldn't be able to be independent either in theory. 

In short, I question what a D-Box can do that any other Roll/Pitch/Heave solutions couldn't do with fewer actuators and lower cost. 


If for the purpose of this conversation, we say that the D-Box really only provides Roll/Pitch/Vertical Heave, this presents an interesting challenge: the combination of Seat Mover Style G-Force simulation with Roll/Pitch simulation. 


ride_roll_anim1.gif


G-Force vs Pitch and Roll 

If you're not familiar with the concept/principles of our Stage Series motion, I'll spare you the pitch here and suggest that you wrap your head around it by visiting our website and reviewing the 'Motion Principles' tab on any of the Stage Series product pages. 

In short, we choose to focus on the most extreme component of what a driver feels and have concluded that to be G-Forces and related muscle tension/pressures followed by traditional motion simulation which aims to manipulate your inner ear/balance, etc... To simulate the impact of G-Forces on the human body in a convincing manner, you need to be able to make darn quick movements relative to simulating the impact of pitch/roll on the mass of an entire vehicle convincingly. 

That said, we've always prioritized flexibility/tunability so as to facilitate widely varying customer preferences so a Stage Series sim can do either G-Force simulation or Roll/Pitch simulation and even some interesting combinations of the two depending on how you setup your profile. 

The problem becomes that since the D-Box motions are very much like pitch/roll style motions, depending on how you setup your Stage Series (G-Force simulation or Roll/Pitch simulation) the D-Box movements simply become additive or canceling but with a bit of added weirdness since due to the amount of mass involved with moving an entire Stage Series, the D-Box movements are relatively delayed and probably would be perceived as such even with a lighter rig due to actuator performance differences. 


image001.jpg 


Timing 

Not all motion simulation software is created equal, in fact, the majority on the market induce an amount of lag that is just plain sloppy workmanship/unacceptable in my humble opinion. 

I find it just as important, if not more important than the motion style, that all motion devices on a simulator be in sync to an error of within a few milliseconds or less. Software lag aside, systems that move a large mass freqently have mechanical lag to go with it, or they have steep gearing that limits their top speed which makes them feel awkward when combined with a device that doesn't have these speed limitations. As an example, most (if not all) D-Box actuators as said above to have a 100mm/sec max speed, but the Stage Series actuators have a max speed of 400mm/sec. 


Bottom line, I beleive we can provide tuning options to to address most of these concerns and in fact we already do for several of them. The jury is still out on value proposition and whether or not there is method of achieveing the D-Box Pitch/Roll/Heave at a lower cost and with less compromnise when combined with other devices. The jury is also still out on whether or not a D-Box configured to do only heave so as to add what it can without adding anyting negative to the Stage Seres equation is cost justified. Those aren't the sort of things we make a final ruling on. I see this question as a customer preference type of thing. Our focus is on giving you options regardless of our opinion on what is or is not cost justified. 

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A subject near and dear to me.   I have Dbox and considered SimX at the time.  I currently have Dbox and GS-4 working together, with Accuforce wheel, and the systems do not "compete" with each other (yes, it's two programs to turn on/off, but not interfering).  Works very well imo. However, the Dbox tilt does likely add to the weight/load on the GS-4, which resists the momentum created by Dbox movement.  

Oh, and I think "lag" with Dbox is a myth.  Very powerful and (to my perception) immediate feedback. 

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Happy to hear everyone's thoughts and interesting that Berney is thinking of new ideas.

Perhaps I worded my thought poorly, because I see a few of the comments are wondering why I'd want to combine the two systems or that the heft would make the DBOX work harder.  That wasn't my idea.  

My idea was to utilize the seat-mover principle with a DBOX system.  To explain further, in a seat-mover, the seat moves (hey) independent of the wheel, thus creating the core-tightening forces Berney described.  The seat is being moved by two (not including my rear traction loss) SCN5 actuators.  What I am saying is that the entire rig, except the steering wheel, moved via DBOX.  There would be no SimX setup.  Imagine any DBOX style rig, say the Sim Labs P1, but instead of the wheel deck being mounted to and moving with the rig, it was suspended on standalone feet with a DBOX rig under it.  This way, the entire DBOX rig would move but the wheel would stay put, creating the seat-mover effects, but by using DBOX actuators instead of SCN5. 

Does that make more sense?

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Beef36 - when I tried DBOX it was many years ago, so I'd love to try a more modern setup...but I actually preferred the seat mover feeling to the DBOX feeling.  With DBOX I felt like I was on a fun suspension ride with no consequences.  With the seat mover, my whole body tensed as I felt like my actions had consequences.  Thats the best way I can contrast the two.  The reason for my idea was that I think the DBOX actuators are superior to the SCN5 actuators, mainly in size and with how quiet they are.  This is assuming they both have lag that is imperceptible.  I was thinking we could take the feeling I like (seat-mover) with the superior equipment (DBOX) to have the best of both worlds, but I see your point that they'd probably have to recalibrate how they deliver motion queues.

 

Lasanga Smoothie- Great name.  I can see what you mean in a way (even though he is not moving independent of the wheel which is paramount in a seat-mover), but that motion looks awful.  Its way too dramatic, poor guy in the vid looks like he wants to vomit a lasagna smoothie everywhere!  Lol  

 

estranged_coma - this seems to be a very popular setup.  I've yet to try a G seat, but the new GS5 Berney has been showing off looks slick.  We're really getting up there in cost with a GS5 + DBOX though, I sure hope its good.  I don't like iRacing, so I don't have an account which means I can't read your post on that forum.  Would you mind pasting it?

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Very interesting thread. I currently actually play with the idea of changing from a 3dof seat mover to either 6dof hexapod or a 3dof setup using 4 of the Prosimu PRS200 actuators.

Especially Berney's explanations make me think...again...whether it's worth it at all. There's Barry Rowland's review on his d-box setup, but, unfortunately, as much as I like and appreciate his videos, he's leaving some very important bits out. It's been a while since I watched it, but I remember his statements about rear traction loss are let's call it lame for the lack of a better word.

On the other hand, nowadays with dd wheels most of the cues in regard to what the rear end of the car is doing comes through my wheel anyway.

In regard to the question in the original post I think the d-box actuators would be too limited in travel in order to make this work...unless you position them very close to the centre...then (depending on your rig design) you get maybe too much leverage/load and that may slow down your system. I don't think that would work. However, you could just move the seat instead using the tri-motion concept. Then you deal with lateral force on your actuators...

 

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(pasted from my iRacing thread)

I’m the lucky owner of two rigs. The first is a GT Rig which is equipped with the ECCI 7000, CST F1 pedals, Butt Kicker 2, Fanatec CSL base with custom mounting for UltraForce GS-4 driven by Sim Commander 3. It is completed with 3x27” screens. 

My newest one is a Formula Rig which is a custom designed MDF cockpit that simulates an open wheeler seating position, Fanatec CSR Elite wheel & pedals, 2x- (2250i) D-Box actuators and completed with a SFOV screen from a projector. 

I’d like to focus on comparing my GS-4 and the 2x D-Box and in using them in the iRacing world. Over the past 2 years I’ve been lucky enough to also try other motion setups including DIYs and 4x actuator d-box systems. I will (try my best) to refrain from saying ‘this is better than that’ but rather comment on what I think which motion system is more suitable for what type of experience and user preference. In the end I will say what I prefer and why. 

I’ll structure my writing by going over questions that many of my friends and fellow sim-racers have asked me as I think it’s the best way to describe the comparisons. I won’t go into technical details of the GS-4 and the D-Box as those info can be found plentiful on the internet. Lastly, please keep in mind that this topic is a very subjective matter, what one person calls beautiful the other could describe as ugly 3b63d1616c5dfcf29f8a7a031aaa7cad.gif 

Before I begin it might be helpful to describe myself. I’ve been sim-racing since the late ’90s and have tried most mainstream race simulations. In real life, I have competed in amateur kart races in various tracks across Asia. I have also experienced sitting in race-ready street cars driven by professional drivers on circuit tracks and off road.  

Then let’s get onto the questions: 

How does my UltraForce GS-4 compare to my 2x D-Box system? 
I describe the GS-4 as a system that simulates how my body feels when being in a car and the D-Box as something that simulates how the race car reacts in its interaction with the road environment. In the GS-4 when going around corners the back and bottom panels pushes my body in a sustained manner that I feel the G-force present throughout the entire corner. Same thing during acceleration & braking and other forces. The D-Box on the other hand gives a very clear feeling of how your car’s suspension moves, how the tires rub against the track surface, how the car chassis rolls and bounces during over and understeers. When the gear changes I feel a thump, the RPM rumble of the car vibrates my rig impressively, and yes when I go off track and hit a wall I hold on for dear life. I’ve coupled my GS-4 with BK2 so that I feel additional effects of the car but the D-Box has this excellently built-in. 

Where does the GS-4 outshine the D-Box and vice versa? 
The G-forces that I feel on my body is where the GS-4 shines. I do not get this with the D-Box. On the GS-4 I also still feel the bumpiness of the track surface and the effect of the gear changes, etc. but where it lacks the most is in feeling connected to the 4 tires of the car. This is where the D-Box shines. The D-Box lacks providing me with the sustained g-forces so when going through corners, for example, I simply feel my body tilting in one direction. Recalling back when I was still using my fanatec wheel on my GS-4 GT rig and comparing it with my setup now where the GS-4 is coupled with the ECCI 7000 I have to say that I’ve had more of a workout in the GS-4 than in the D-Box. In other words the GS-4 it takes more energy on my body than my D-Box. (I will make a different statement later on when I describe 4x D-Box systems). 

 

If I only had to buy one today, which one will I choose? 
This is a hard one! The GS-4 was my first motion system (my first baby) so I have sentimental feelings about it. If I were rational, and the leading factors in my consideration are price and compactness then I’d still choose the GS-4. The D-Box is expensive, takes a much bigger space and more tricky to mount. But the motion systems is (oh so much) more complete despite the lack of sustained g-force because I can feel exactly what the car is doing. I can even say that the physics of iRacing really comes alive and really makes a lot of sense with the D-Box. It is almost like iRacing was meant to be experienced with a D-Box. Maybe this says a lot about how realistic iRacings physics is, and perhaps it may even be ‘too realistic’ that if you only experience it with a wheel and pedal you are only ‘seeing the tip of the ice-berg’. In hindsight this analysis makes sense when looking at the endless debates about ‘how realistic is iRacing’s physics’. 

How do I compare 2x D-Box and 4x D-Box? 
This is an interesting and highly subjective topic. Let me first state my personal opinion and preference. Taking away the consideration of price, and only focusing on the motion immersion, I prefer the 2x instead of the 4x. Why? Firstly in my opinion the 2x gives enough accurate cues to what the car is doing like what I described above. The 4x gives me ‘too much’ sensation that my brain and body can’t process it fast enough to handle it. Bear in mind not only would I have to process the motion effects, at the same time I have to also manage what the wheel FFB is doing, visual cues from the screens and the audio effects from the speakers. But this is not the failing of the 4x D-Box system but rather the failing of my lack of focus to be a real life racer. The reason I say this is because the 4x is as realistic as it can be, it really is. If you want a complete immersion experience and the ultimate setup and to feel what it really feels like to drive a real race car, then the 4x is the (only) way to go. A 4x D-Box system is the cheapest way to get a real (insert your favourite race car name here) inside your living room! But you also have to have the focus and skills of a real race drive in order to tame the beast that is 4x D-Box. 

Where do both my GS-4 and my D-Box lack? 
To this day I’ve yet to experience a motion system that gives me the sensation of the elevation of a track. Consider tracks like Brands Hatch, Spa, and Suzuka where in certain sections of the track goes steeply uphill like Eau Rouge or downhill like the last corner of Suzuka. Although these systems are advertised as being able to give you these sensations I still maintain that they do not. Even the 4x D-Box system does not do this, or maybe it did but as described above there were so much coming out of the 4x that I probably could not notice it. 

Both also still lacks a clear sensation of 2 other things: traction loss and slip angle loss. I did an experiment where I turned off the FFB of both my wheels and if I were to close my eyes I wouldn’t be able to tell. Maybe it has to do with fine-tuning the software side of the systems but so far I’m led to the conclusion that traction loss and slip angle loss come better simulated through the wheel and the visual cues. 

How loud are they? 
Easy question. D-Box is much quieter. The GS-4 squeaks audibly when the panels move. 

Others points? 
Achieving an equilibrium balance of how strong your wheel is in combination with the motion system and others such as how strong your audio is is paramount. I’ve experienced setups, including my own when it was not yet properly configured, where the motion system overpowers the strength of the wheel (imagine combining a D-Box with a G27 wheel). The key to getting the maximum benefit is to ‘orchestrate’ all the components so that they all play a beautiful symphony. 

The D-Box is heavy duty. It will break your rig if yours is not a rigid heavy duty rig. My formula rig is constructed out of MDF but they are properly secured at the joints with industrial bonding adhesives and reinforced with bolts and nuts. I then connect the rig to the D-Box using 80/20 frames to achieve the desired rigidity. I’ve set the D-Box software to be just slightly above default (around 35-40% strength) but I suspect if I go beyond 65% my rig will simply break. 

I’ve ordered the DK2 Oculus Rift and I’m curious and excited to try it on both of my systems. I wouldn’t be surprised if I arrive at slightly different conclusions when I’m completely inside a virtual world and where I’m not ‘planted’ to fixed references around my rig, i.e. the wall, the door, the windows, etc. 

Which system makes me faster? 
Neither. I'm still equally as slow. But I think the D-Box makes me more consistent. 

What would my ultimate motion setup be? 
If money, space & time weren’t an issue I’d combine a stripped down GS-4 and install only the panels onto a seat then onto a compact no-flex rig (preferably formula-type) and then mounted onto a 2x system. And then all then mounted onto another axis which could simulate the elevation of tracks. 


Well, thanks for reading. Feel free to comment, agree, disagree, or ask other questions. 

 

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Thirsty - what are you referring to by "tri-motion concept"?

estranged_coma - thanks for sharing the detailed impressions.  I think (Thirsty cover your eyes!) Fast Track Sims is centering their new rig motion theory around a rear 2 actuator DBOX setup with a front pivot point.  I'm interested to learn more about this as I'd imagine this setup with the GS5 would be a killer setup.

Errr...that setup, bolted to a platform with rear-traction loss...that would be a killer setup. 

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2 hours ago, switchface said:

Thirsty - what are you referring to by "tri-motion concept"?

estranged_coma - thanks for sharing the detailed impressions.  I think (Thirsty cover your eyes!) Fast Track Sims is centering their new rig motion theory around a rear 2 actuator DBOX setup with a front pivot point.  I'm interested to learn more about this as I'd imagine this setup with the GS5 would be a killer setup.

Errr...that setup, bolted to a platform with rear-traction loss...that would be a killer setup. 

Ah, well, I finally got over this Fast Track Sucks rig purchase nightmare ;-)

Have a look at this video showing a tri-motion rig:

It's basically a set mover with heave - just the seat moves, everything else is static.

I like this idea, but there are two things I'd be concerned about. Noise seems to be more of an issue than with conventional seat movers. The other thing is lateral forces being applied to the actuators. That can come from operating your brake pedal if you choose to work with high pedal forces.

Anyway you could combine that with a GS4/5 seat as well. I, for myself, decided against using it, but I think it may provide great immersion.

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Glad you were able to not let that bother you further (hey, I did say cover your eyes!).  To bring them up again, they have a new P1-R2 rig using 2 DBOX actuators with a front pivot point.  This is interesting and I'd like to learn more about it.  I messaged Mark on one of their Facebook posts about it but he never responded.

This concept above is exactly what I was describing in my original stoney idea!  Hmmmm.  I'm curious why noise would be an issue - the SCN5 are squeaky whereas the DBOX type actuators are usually quieter.  To offset your lateral force actuator, what if we simply put the pedals on the chair platform as well (I guess this is my exact idea from the OP). 

Well, all these ideas are coming at a weird time.  I may be selling my house, which means my beloved rig may have to go :(

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The problem with this front pivot design is, it, depending on the configuration, reduces not just travel but speed as well. That can be an issue in case you do not use very fast actuators.

You can get full speed out of them, but in this case you sacrifice pitch.

In regard to noise, our 2 SCN5's are sort of audible enough I would think. The 3rd one is not always active. With 3 of them permanently working and carrying load it may be different. It's hard to judge from these videos...only saying it's a concern.

Adding the pedals to the moving part increases weight with quite some leverage. The thing would have to be re-balanced.

Doing this with a 2-actuator d-box system may not give you enough speed. On the other hand, if you position the pivot very close to the seat and actuators, sort of in a triangle shape configuration like it the video above, it may actually work. Having the pivot somewhere at the pedals may not be good.

Sorry to hear you may have to sell your rig...would be a pity. Is it because of its size?

Again, I'm considering trying out something else as well...the bloody rig builder in me... ;-) . I tried a pretty expensive 6dof hexapod platform, which I had in mind changing to. That was a disappointment though. So I'm thinking too much downtime & money...for what? In the end these 3dof seat movers controlled by Simx's Simcommander are damn good...I love it :-)

Edited by Thirsty

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Yeah, I finally was able to watch that video with sound and the actuators are definitely loud there.  A lot of these newer motion platforms seem to use SCN5s in a setup that looks like a DBOX setup (similar to the one you just posted).  I love my current setup, but wouldn't want it any louder.

I'd imagine Mark/FTS has the pivot in the ideal spot, otherwise he wouldn't do it.  Its no like he hasn't build/designed/sold 4 actuator setups before, so their recommendation to save money and go with 2 has me at least intrigued to learn more.

Would be selling the rig only because of the regular added complications of a home purchase/move.  Its a high dollar kit that weighs a lot and takes up a good deal of space.  It would just be easier to not have to deal with all of that when I'd have a lot more on my plate.  I think I have about a dozen emails of people that have asked to purchase it over the years, but I have a local friend thats been wanting to get into sim racing and hasn't pulled the trigger yet - I'll give him a local/friend discount to pass along the fun.

6Dof Hexapod?!?  Wow, it would be something special, thats for sure.

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There are some new options that could potentially compete with a D-box setup to a large extent, and at a significantly lower cost while offering more travel and adjustability. I think the combination of a D-box type setup combined with the GS-5 seat would be really excellent for my use. I love the heave motion (although, 1.5" is not enough for me) and require a quiet setup for racing at night when my family is sleeping. I also need the rig to be compact and the D-box works great for that. Sustained G-forces are what is missing for me so I really think a G-seat is the last piece of the puzzle I'll need.

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I read in part of a thread that someone played on a dbox and gs4 and felt no sensation - motion of going up and down hills and camber (Brands Hatch).

interested as granted I have only lowly 2 DOF DC motor (seat mover )and DIy actuator rigs(full balanced frame 2 DOF) , however,  I can feel the hills and camber very well. 

Maybe its what the motion software puts out in forces available.

I run SImtools and pitch and roll are almost in all race game plugins. 

Even the games that only have sway and surge (flatout2) as example, theres still the tilting forces of pitch and roll.

Maybe adjust the motion settings on the dbox if it has it

 

 

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On ‎10‎/‎16‎/‎2018 at 4:22 PM, motiondave said:

 

I agree. I tried Dodge simulator (4x d-box) at 2017 Chicago Auto Show. Not that impressive at all. The iRacing guy used 2x d-box posted above seems make a sense, as described he is pretty happy with. This is consistent with others conclusion. In the comment section of SRG d-box review video

m.youtube.com/watch?v=bU7TJG8PUSk, 

anasmsk11 who owns both 2x and 4x setups said he and all others tried both found the 2x is far better and more realistic feel than 4x.  Thus I dont think that 4x is more realistic than 3x for 3dof motion. He may need to try 3x setup. People are initially overwhelmed/impressived by 4x d-box style probably not because of the 4x config, instead likely due the fact that who might have never tried linear actuators rig before.  Like those who had tried both actually prefer the 2x config. A simple common knowledge tells a truth about this. A turntable record player designed with 3 legs to move in 3dof. It would be difficult to level the player if designed with 4 legs. Often you end up with one leg lift up. Here are couple examples of DIY 4x D-box style: 

youtube.com/watch?v=TrQANt0KqW4 and youtube.com/watch?v=DDUe9WQ-Cl4

demonstrate that at relatively large movements (say high speed cornering) you can see a leg lift up.That not just means one leg was being too short at given a moment of time, but also means other leg(s) could be moving too far (long), which cannot produce 3dof motion accurately. It looks OK to roll one side to other, or pitch front side or back site solely. But if you want to do roll, pitch, and heave together at same time, then you will see the problem, as shown in previous two videos. Other example, see video: youtube.com/watch?v=EElowvFEpZQ who actually fixed 4 actuators on the ground. Also: youtube.com/watch?v=SCEKoEEE5fE  you see all 4 drivers are restrict/constrained each other cannot freely/independently move. Even with very shorter spacing between rear and front actuators to enhance pitch movement, like this D-box setup: youtube.com/watch?v=dlRjOJt7Nq0  there is no evidence to show it can do a combination movements (roll/pitch at same time). Thus, such configuration just cannot produce a realistic chassis movement at high speed cornering. For a small movement with such 4x config for vertical bounce and bump would be OK. However, if one changes front 2x actuators to 1x with only one actuator on mid of front mounted on a ball joint fixed on the ground, then one has a 3x configuration for true 3DoF. Hence can produce true smooth 3DoF motion with combination of roll/pitch/heave movements, like: youtube.com/watch?v=6UxeQVYAOaw  Thus will offer much more realistic feel on chassis movement.

4x drivers for 3DoF is difficult to implement although mathematically possible. This is because calculations of 4 actuators' positions (x1, x2, x3, x4) mapping to 3dof (roll, pitch, and heave) positions are totally different from that of 3x configuration. 4x config constrains all 4 actuators (x1, x2, x3, x4) they are dependent each other and have to move all collectively (each one just cannot move freely unlike 3x config).  Thus, for 4x config for 3dof the SW has to be specially taken care of, otherwise it will produce 3dof (roll, pitch, and heave) positions inaccurately. The previous two video offer a such proof.  It looks only D-Box SW offers for 4x config 3DoF. Searching through published papers and  robotics & motion platform industries just could not find 4x for 3DoF. Today, all motion platforms designed as n x drivers for nDoF config. I never have seen such n+1 drivers for n DOF, except from d-box.

Such 4x drivers for 3DoF config design just cannot be effective. I found only the most expensive sim NADS/Lexus/Toyota uses 4 actuators on the corners, but their purpose is for vibrations only, not for motion. The max vibration amplitude limits under < 0.2 inch though:

https://www.researchgate.net/publication/265664048_NADS_AT_THE_UNIVERSITY_OF_IOWA_A_TOOL_FOR_DRIVING_SAFETY_RESEARCH

Thus, it seems to make a sense to have a 4x d-box style setup with very small heave (vertical) movement only (tune down < 0.3 inch up-down movement) for bump and vibration only (1dof), and add a seat mover on the top for motion (2dof). Or use 3x d-box style with large > 3 inch movement for 3DoF motion.

As 2x for 2dof although not 3dof, but would be correct for full motion. I took anasmsk11's words and  build mine with 2x with SCN6 4-inch actuators and add a seat mover on the top.  One most important aspect of sim racing motion rig is to offer a "correct" motion cue on high speed cornering. This is all we go after. While cornering at high speed, due to weight transferring, the car will roll and pitch at same time. 2x drivers for 2dof will give correct movement and hence offer more realistic sensation feel of car and tire dynamics, while 4x config cannot offer such combination movement (pitch/roll at same time). You would not get confusion and struggle feel like 4x has, as the iRacing guy pointed above "The 4x gives me ‘too much’ sensation that my brain and body can’t process it fast enough to handle it"   I tried the 4x , to me the high speed cornering dynamics just not feel right. As  anasmsk11 said in the comment section of the SRG d-box review video: "...myself and everyone who tried both, all said the 2250i felt much better. You really need to try it. The 2250i system feels much more composed, predictable and realistic. Might be hard to believe, but it truly is much better. ....only 2 actuators, the cockpit feels much more solid, predictable, and more precise in the movement, you can tell exactly whats going on so it relates much better to the visual. Overall, the amount of motion you get is no less than the 4250i at all, you get plenty of motion and vibration from 2 actuators, just much more precise, which as a result, is more enjoyable and feels more realistic."

I had a discussion with folks on this subject recently at Race Dept forum: https://www.racedepartment.com/threads/simxperience-gs-5-seat.163116/page-6

People often has misconception thought because car has 4 wheels then the 4x must be better than 3x in terms of 3DOF. No, it is not. Your rig is a rigid body and you still get 3dof (roll/pitch/heave), nothing more, but in a struggle way (all 4 drivers are restrict/constrained each other cannot freely/independent move: youtube.com/watch?v=SCEKoEEE5fE), unlike 3x with much smoother (all 3 drivers independently/freely move: youtube.com/watch?v=VvBojB_RUBA). Such fashion of 4x actuators struggle for 3DoF could yield a fuzzy feel leading one to believe “better” or more “realistic” psychologically. Most of people using 4x D-box style rig is liking the small vertical motion to simulate the road bump and impact. This is normal for us since our brain trained to feel that way during daily driving to work and experience bump and road texture and impact etc every day. We do not often racing at 100 mph cornering, in fact I never did. So what do we need a motion sim rig at home for? For simulating daily driving experience or high speed cornering and braking experience? For owners of 4x D-box style rig will likely end up to add either a G-seat or a seat mover on top in order to experience g-effect feels on high speed cornering and braking.

On vertical motion, we all know that the seat and pedals are mounted on chassis so only chassis telemetry data are useful and make a sense to feed the actuators. Chassis is connected to absorbers/shock/springs etc. In terms of vertical motion (heave), using chassis motion telemetry data makes a sense.  Most sim games offer GC vertical g data (acceleration) and rideHeights data (vertical displacement). They are chassis motion data,which you need to feed the actuators since the seat and pedals mounted on the chassis. All other non-chassis related data, such as tire suspension drop/bounce, etc, shall not be added. Arguably, I see one added "tactile" data (cooked from suspension deflection data) to actuators and caused more fuzzy and struggle for 4x actuators on 3dof, but believes this is better and feel like suspension movements. I see many of them who stand behind this argument.  I believe the chassis rideHeight data shall be added to driver the actuators. Here is a video I made  “motion simulator vertical motion realistic”

youtube.com/watch?v=8qUo987IyIw 

explains details in the description why need of adding rideHeights data.

 

Edited by Joe Extraknow

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