New to Sims. Couple of questions.

Hello Everyone,

I have been looking around for a week or so trying to get as much information as possible be for even designing a preliminary racing ( only) rig. I have come across numerous 2dof and 3dof diy rigs that seem to all share the same design principles when it comes to placement of worm gear motors.

What I really haven't seen are any rigs that mimic the set up of a real car. What I mean is basically a frame with 4 motors ( one in each corner similar to a dbox?). To me this seems logical as it would place the motors in relatively the same location as a real cars tires and shocks. Is there a negative to this sort of setup? Is it considered overkill or something to have 4 motors instead of just using 2 since its basically a glorified seat mover?

One thing that seems to be a concern when designing a rig is how to handle heave ( up and down jumps, kerbs ?). I thought if you were to use a 4 motor system to help lift the rig up and down that may help with the heavy loads? That brings up another issue. Now all 4 motors are supporting the weight of the entire rig and driver 100% of the time ( as opposed to a U joint supporting most of the rig).

What I was thinking of was using a support platform with a U joint under the rig that would help take stress off the motors during normal operation. Then when the rig needs to heave up and down, the support plate would be able to move up and down via some guide rods. I did a pretty crude drawing below. I'd love to hear any advice on what I've come up with. Please excuse the crudity of the drawing. I didn't have time to color it or draw it to scale...

I was thinking the guide rods would help to only allow the rig to move up and down when all 4 motors receive the 'heave' code. The rods would keep the support plate from rocking during surge, sway, etc. Springs could be added to the guide rods to help the motors lower or raise the rig.

*edit*
Also, I don't know if its possible in the software but I thought it would be cool if when you go over a kerb first the front of the rig would pop up and down then the back would do the same thing to simulate the bump. Does this already happen? I feel like it would be hard to reproduce this effect with only 2 motors in the back. Thanks !

While I agree heave for racing needs to be at a faster speed than for flight, I feel a need to strongly disagree that it is less important for racing, sorry! Of the three forces, heave is by far the most active since it is the one that provides the feeling of the road surface! While many 2dof rigs still incorporate heave into their profiles, doing so on axis that don't actually heave provides inaccurate feedback imho. After riding on a racing rig that properly reproduces heave I dare you to tell me it is less important than for flight!

2dof, 3dof, 4dof - sometimes a question of philosophy but IMHO there is no doubt which dof we should use if you are a pure racer. In this case a 2dof is the best way to get the best immersion. Hard to believe but I can tell you there is so much fun driving the track trento-bodone in Assetto Corsa because you feel every laser scanned bump, you will be shaked like a long drink and feeling is insane. Most of the Pro Racers say the 2dof seat mover is the only one which gives you the best and real feedback from the track in comparison to a real race car.
PS: racing sim = seat mover; flight sim = motion platform.

Ive had probably over 100 people play on my 2 DOF seat movers with 5 forces. I ask them how it feels, most of them comment that the motion is very realistic and gives a very good impression of the car in game.

@bsft, all gurus at xsimulator.net: IMHO once and for all we should cement this FAQ. Already I am "tired" to answer any questions about "I am a racer, which DOF should I build?" JM2C.

I dont have access to FAQ
Racingmat does and copy/pastes the info to FAQ
Ask him

Thanks everyone for you responses.

Basically the reasoning behind wanting a system in which the whole rig would be supported at the corners was the fact that I want the pedals and wheel to move along with the seat. I have seen the 2DOF rigs that also move the pedals and wheel, but there is something that just looks off about them. The fact that the front is just flapping around with no real support just looks unstable. I'm sure they work great for most, but are there any down sides to moving the entire frame with just 2 motors + U Joint? Would you venture a weight limit guess to that sort of setup? Any stability issues?

I wanted to try and achieve the same look and feel of a dbox but with worm motors instead ( to keep cost down). These seem to be the popular ones around here ( http://www.motiondynamics.com.au/worm-drive-motor-12v-24v-200w-180-rpm-20nm-torque.html ). I was hoping that 4 motors ( instead of 2) along with the U joint would help with stresses on the motors. My reasoning was more motors > less work each motor has to do = longer motor (internal gearing) life. Would this be a correct assessment?

I realize that a good percentage of a simulator is fooling the mind, So if the same motion can be achieved with less motors I'm all for it. The more I look into things "loss of traction" or sway seems to be a fairly important motion. I may forgo the whole 4 motor thing and concentrate more on 3DOF. I'm big into rally and drifting type games so I think I may benefit more from that.

Also, please don't take my questioning the wrong way. I really value everyone's input and I'm not second guessing your reasoning or criticizing your setups. I'm more or just less curious as to how these designs became standard practice so to speak ( I love researching ). Thanks again !

I propose to define a Seat Mover with traction loss as a "2DOF with TL" and not a 3DOF (of course, which meets the facts as well) to avoid any confusion about the concept or design we are talking about. Any other suggestions?

Full frame with pedals emulates the cars motion poorly to whats actually happening inside the car. Watch a couple of in car videos of a rally car and you will see what i mean, the driver is getting thrashed about in the seat, sorry the interia created in a full frame just doesn't feel right. See motion simulators is about fooling the brain into thinking you felt that bump or can feel the car surging forwards without you actully preforming the exact motion. Where 6DOF units fall over emulating a race car, big fail, beautiful for flight thou.

I totally agree with @Pit.

I have had professional drivers on my several rigs I have built over the years and built just about every type of design here on the forum, its easy to get addicted to this stuff, and every driver has commented immensely on the seat mover and do agree the only thing missing is a traction loss frame. And theses guys are all paid drivers, its their job to know. LOL one offered to swap his 20k dbox unit for my 2dof seat mover, "I told him ya can keep that crap", he sold it and knocked on my door and I built him one of mine, now his mates want one. I told him just copy it , go for it.

@eaorobbie wow, great stuff

My concern with only the seat moving was being thrown towards or away from the steering wheel and pedals. However if that sort of motion is more realistic , then I'll definitely explore that route. Does anyone have any quick suggestions for a LoT motor? I assume it would need to be a bit beefier than then seat movers since its swinging the entire rig.

Well a little misunderstanding of what goes on in seat mover, Mine only moves a total of 10deg in pitch, your feet might move maybe 5mm if that ,its more of a sensation of the seat rocking back, like said before in a surge forwards motion of the car, hard accellerating, the seat dips back 3-4deg and snaps back all in under 1 ms. This translates to the sensation of the wheels bitting in and the rear of the car dropping as you surge forwards, then as the seat rises its like you have been pushed into the seat by the acceleration. This is all happening in ms timings not secs resulting in the seat dances under you and most time your body can not keep up, this is where we fool the brain, full 2dof is very hard to achieve this.

That makes sense. I think I have Enough information to get planing now. Thanks everyone !

If you drive your car and hit the full brake, if not wearing the seat belt, you will probably ended up hitting the wheel with your head

This is what Seat Mover is doing too, hit the brake and it will push you towards the wheel.
Hit the gas pedal and it will put you back in the seat, away from wheel, but that's only for a few degrees, nothing more like @eaorobbie said.

I've tried those Ferrari's 6DOF platforms and I must say that I like Seat Mover type eventually with Traction Loss more than a full framer, I got better feel to it, at least in my brain

My foot motor mount sim was good as a full frame, nice and short and sharp, but you lose that seat mover effect though.

@bsft

Yeah, I remember that foot mount sim, it's one of the first videos I saw from you couple years back when I started having interest in sim building, you had a big "My Sim Collection" thread on other forum. Wow, the time is passing by quickly

And as I recall it was working very good because it wasn't setup to move the monitors too, just the wheel stand. It was something between full framer and seat mover.

I spent some time driving around my work's industrial complex last night paying attention to how you actually move around in the seat. 2DOF + TL is the way to go. From what Ive seen and what you have all said that set up should do a good job reproducing the way a car actually transfers forces onto a driver.

On the software side of things I have 2 questions. You don't have to write a long response if you don't want. Just a yes or no will do and I'll look into it. When using Simtools can you create a unique motion profile for several users? In other words something that will scale the forces up or down according to weight, age, height, driver skill level, etc. Also, is it possible to drive FFB motors using Simtools? For instance a shaker motor mounted under the pedals that will vibrate as speed increases. Admitting I haven't even looked at the software yet, these are just questions that come to mind.