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Design Considerations & Resources

Design Considerations & Resources

There are many things to consider when designing a DIY motion simulator.

SimCalc - Calculate linear speed and forces of your design


DOF, Angles & Forces

axis definitions: [​IMG]

yaw, roll and pitch are actual angles: [​IMG]

Sway, Surge and Heave give forces: [​IMG]

What kind of simulator for me?

You would like to have as much fun as us?!
Your first questions should be the following:
What do you want to simulate?
driving or flying ?

flying requires wide angulations: often joyrider, 6 DOF models or gSeat like military
driving requires short range and quick movements: all models (rarely joyrider), but ideally a seat mover (2DOF) **
What principle?
2DOF seat mover (Frex, CXC, benefit of additional motion cues explained) **
2DOF with wheel and pedals on gimball
2DOF with wheel and pedals joyrider (acesim)
2DOF Flatbed (design)

3DOF with heave or under seat heave here, under frame heave here, or compact heave here.
DOF with traction loss
3DOF 360°


6 DOF (CKAS) vulbas merchan-e wannabeaflyers RiftFlyers

unpowered flight simulators:
What is your budget?
budget=sim + wheel + pedals + (shifter) + Gamer PC + screens or videoprojector + games licences

Depending on what you have left for your sim:
DC motors (Wiper, Worm) + HBridge : cheaper
SCN: more expensive
AC motors + VFD : expensive but powerful
or motorbike (credit @AlBuw) ? [​IMG]
or skying ? [​IMG]
or riding ? [​IMG]

How to animate Sketchup 3D model with Simtools?

See the instruction here by @pillowsack on how to configure MSPhysics for use with SimTools, as the latter has superseded SketchyPhysics: https://www.xsimulator.net/community/threads/proof-of-concept-sketchyphysics-alternative.9944/

A quick start guide using SketchyPhysics:

Use the latest 32bit version of Sketchup, even on a 64bit system: http://dl.trimble.com/sketchup/SketchUpMake-en.exe

Run Sketchup once to create the folders needed to install SketchyPhysics.

Drop theses files in the SketchUp Plugin folder C:\Users\Your_User_Name\AppData\Roaming\SketchUp\SketchUp 2016\SketchUp\Plugins: https://drive.google.com/file/d/0B2QcRBB299sSdFpuVUN2MUJwRlk/view?usp=sharing

Here is a simple pre-configured 3DOF SketchUp model: http://www.xsimulator.net/community/attachments/motionsimmodel-zip.27340/

Be aware that complex models may create issues for SketchyPhysics: http://www.xsimulator.net/community/threads/sketchup-sketchyphysics-simulation-faq.7864/#post-95619

Here are the interface and axis settings:

1.jpg 2.jpg

As @speedy points out the files in the 'Wackelstuhl.rb' file which is located in the C:\Users\Your_User_Name\AppData\Roaming\SketchUp\SketchUp 2015\SketchUp\Plugins folder has the 3rd axis inverted: http://www.xsimulator.net/community/threads/sketchup-sketchyphysics-simulation-faq.7864/#post-95596

The 'Wackelstuhl.rb' file can also be edited to provide a full 6DOF like this:
Untitled.jpg Screenshot (1).jpg
require 'socket.so'
socket = UDPSocket.new
socket.bind("", 3157)
timer_id = UI.start_timer(0.01, true) {
message, sender = socket.recvfrom_nonblock(100)
message1, message2, message3, message4, message5, message6 = message.split(";")
$axis1 = message1.to_f / 256.0
$axis2 = message2.to_f / 256.0
$axis3 = message3.to_f / 256.0
$axis4 = message4.to_f / 256.0
$axis5 = message5.to_f / 256.0
$axis6 = message6.to_f / 256.0}

If you want to try a 6DOF SketchUp model @DocLove has kindly made his model available: http://www.xsimulator.net/community/attachments/stewart-platform-3-zip.27976/

Download the pre-configured SketchyPhysics_3Axis_ SimTools V2.0 axis preset: https://www.xsimulator.net/community/threads/sketchyphysics_3axis_-simtools-v2-0-axis-settings.9551/

Full documentation:

Sources for SketchUp connection 1.00
Thanks to @value1

How to Connect SimTools to SketchUp
Thanks to @value1

WireViz - document your wiring

WireViz is a tool for easily documenting cables, wiring harnesses and connector pinouts. It takes plain text, YAML-formatted files as input and produces beautiful graphical output (SVG, PNG, ...) thanks to GraphViz. It handles automatic BOM (Bill of Materials) creation and has a lot of extra features.: https://github.com/formatc1702/WireViz


A calculator for just about anything

3D model of PGSW/Motion Dynamic motors

FOV for various screen options

Speed Needed For Good Motion

There are many factors to consider when designing a motion simulator. One is how fast should it move for a good experience.

The speed needed for good motion is a bit subjective and is significantly affected by design choices, but general wisdom suggests between 150-700mm/s http://www.xsimulator.net/community/threads/minimum-rpm-needed-for-a-2dof.7009/

Check here for a guide to working out linear speeds and forces for different motors, gear ratios and levers: http://www.xsimulator.net/community/faq/calculating-basic-linear-speed-and-forces.89/

Build a working model to test your design ideas

Here @insanegr shows how to use @eaorobbie's Arduino code to build a 2DOF RC servo driven model to test out your design ideas: http://www.xsimulator.net/community/threads/2dof-simulator-servo-model.6851/#post-7727
maquette InsaneGr.jpg

You can start small. If you are really adventurous and are looking for the ultimate test model then check out @hooshang's impressive 6DOF model: http://www.xsimulator.net/community/threads/6dof-platform-with-small-dc-motors.5634/

Thanks to @Leo Salo you can use a RaberryPi to drive your RC model simulator: https://www.xsimulator.net/community/threads/3dof-concept-model-using-raspberrypi.10570/#post-136827
maquette LEo Salo.jpg

@MarkusB https://www.xsimulator.net/communit...th-integrated-g-seat-fans-and-vibration.7684/
maquette FT MarkusB.jpg

If you have a 3D printer, or at least access to one via the 3DHubs, then @EricSteijlen has provided the stl file for this really neat 6DOF model: https://www.xsimulator.net/communit...ype-with-arduino-and-servos.9504/#post-121437

maquette 3.png

Full Frame VS Seat Shaker Designs - Which is better?

It is unlikely that there is or ever will be a consensus regarding full frame Vs seat shaker designs, as it depends a lot on the individual.

Many hard core sim racers tend to favor the seat shaker design, where only the seat moves, and counter intuitively it actually generates some additional motion cues at the wrists and ankles. Many commercial rigs follow that path.

Others favor a full frame, particularly for flight sims, but some racers also prefer them.

Both designs work well and in the end it is a bit of personal preference to which you prefer.

Either way traction loss is often considered as furthering immersion for both designs. After implementing heave I would have to say that it also brings a whole new dimension to how you experience the sim.

There are somewhat similar posts around the same sort of topic, here are some:





Credit @noorbeast: http://www.xsimulator.net/community...vs-seat-only-which-is-better.7713/#post-92445

There are also other design possibilities, such as foot mount, knee mount and compact simulators. @bsft provides a useful comparison here and in summary concludes that a good motion profile can address many of the pros and cons of various designs: http://www.xsimulator.net/community...tion-system-for-a-racing-sim.7298/#post-85795

Comparisons between simulators. Other people will of course differ with this comparison, so please add your thoughts.

First things to consider, angle of actual swing of the frames and the profile written. Also, its a brain trick.

If you want a big swinging frame, go hard, the biggest swing I have had is 14 deg total, but others have frames up to 25 deg. And thats for race, not just flight.

Both frames use same motors and JRK control boards

Seat mover with shoulder mounted motors.

Generally, a seat mover can give more precise motion detail as it has less over all weight to move than a full frame. However, too much movement can make it hard to hang onto the wheel or mash the juice pedal. And yes, the wheel and pedals are stationary, so proper placement to allow you being pulled away and pushed around has to be taken into consideration. But as said, it does give you the feeling of being moved around in a seat in a vehicle, even with a race seat to hold you in more. You tend to shift your body around to compensate for movement and also what your brain thinks you are moving like. You can still feel pitch and roll of track, but maybe a bit less as legs are still.

Some SCN seat movers on videos have HEAPS of throw. It might look like fun, but can be too much and eventually make it tiring to drive the game.

As mine is DIY and has 70mm travel of motor lever and at 600mm from the pivot , total angle is 6.5 degrees. Not much, but then again, too much may make it too hard. Other people will of course differ with this comparison.

I had a seat mover of 12.5 degrees at one stage, so with a good profile, it was nice, but a harsh profile and WHOA! Fun but hard to hang on.

Full frame with motors mounted near feet

Full frames allow you , wheel and pedals to move with you. You dont really get sensation of being pulled, pushed around from pedals and wheels. Obviously not as much as a seat mover, but still there. You tend to feel a bit more of the motion of roll and pitch , when your whole body is getting moved around, I find.

Seat mover can lose this a bit, but not really much.

Motors mounted at feet on the frame in question, may take away some of the finer vibration and motion that shoulder mount gives, but then again, shoulder mounting motors would return that finer detail due to higher leveage point. It may lessen a bit due to the fact that a full frame requires a bit more power to move. But hey, just change the profile and increase the motor power a bit more.

Although, I must say, once again, a good profile can give the same sensation in motion, be it from a different spot. Feet or knees instead of shoulders.

Full frame is about 8 deg total swing. May not sound like much considering 4 deg from centre, but again, throw a decent profile in it and you feel like you are moving a lot more.


After a while I get the same sort of feeling from both my frames, even though they are different in design.

In your choice of motion sim build, It will come down to watching videos of other frames, opportunity to play on sims when they are around to do so. Taking a look at pics, seeing what takes your fancy. Heck, even a seat mover can be converted to full frame later, add the extra bit, move pivot, and off you go. 2 seat movers I have sold, the owners have since converted them to full frames, their choice of course. They enjoy both frames they tell me.

I have played on dbox, and scn simulators and the motion is set tame. Although others whom have such rigs wind it up and get great results. Mind you, I dont have that sort of money to get one.

I have been through 14 different 2DOF designs, starting with joyrider design with about 9-10 deg total swing with screen on it. Good fun, but I found it a bit difficult to focus on a screen moving with you. But thats just me.

I had 2 hire sims based on the Desk Racer for a while and over 100 players though they were immersive.

8 professional drivers have played on those simulators as well, and they admit, its not real, but the immersion of being in game is.

Then I moved onto development of more compact designs, with motors under rear, at knees, out the side, shoulder mount, at feet. Still 2DOF. Screen static.

So thats how I go here. Each frame design is a new learn to drive experience I find. Nothing makes me go faster I think.

Shoulder mount rod angles

Cockpit Design Dimensions

Design Software

Working out what you want to build is not always easy, but there are some design tools that can help.


The basic version of Google SketchUp is free and it is a useful 3D modelling tool. You can even make your model motion controlled by a game of your choice and SimTools:

The latest version of SketchUp: http://www.sketchup.com/download

How to connect SimTools to SketchUp: http://www.xsimulator.net/connect-simtools-sketchup/

See @SilentChill's tips for configuring Sketchup 2015 for SimTools: http://www.xsimulator.net/community...v-dc-motors-mms-and-arduinos.6948/#post-79442

And @SteVoortwis advice re 2015: http://www.xsimulator.net/community/threads/actuators-move-randomly-in-lfs.6996/page-2#post-83933


FreeCAD is a totally free Open Source design program: http://sourceforge.net/projects/free-cad/

FreeCAD can include motion simulation capabilities: http://www.ar-cad.com/freecad/tutorials.html


While created to design and sell profile aluminum MayCAD can be a simple to use tool work out a basic motion simulator frame design, even if you plan using other types of build materials: http://www.may-cad.org/en/p1.htm

Fusion 360

Fusion 360 is free for hobbyists: https://www.autodesk.com/products/fusion-360/free-trial

Activate free license: https://knowledge.autodesk.com/support/fusion-360/troubleshooting/caas/sfdcarticles/sfdcarticles/How-to-activate-start-up-or-educational-licensing-for-Fusion-360.html


Linkage is computer aided design software used for quick prototyping of linkage mechanisms: http://blog.rectorsquid.com/linkage-mechanism-designer-and-simulator/

Universal joint placement

For a pivot point wherever possible it is best to use a Universal Joint (often found on the steering and tailshaft of rear wheel drive cars) rather than a Constant Velocity Joint (often found in independent suspension and front wheel drive cars), or DIY rod end based joint, as both may allow unwanted lateral twist. If you do use a CV or DIY rod end based joint then consider a cross brace with heim joint ends between the top and bottom frame to prevent unwanted torsional twist.

The Universal Joint should be placed as close as possible to the actual base plate of the seat. You also need to balance the rig to determine where it bolts to the seat base, find out how to do so here: http://www.xsimulator.net/community/faq/find-the-center-of-gravity-to-balance-a-motion-simulator.55/


As @SeatTime explains the proper placement of the Universal joint best simulates a race car, as detailed in this image:


Calculating basic linear speed and forces

There are many factors to consider when designing a motion simulator. One is how fast should it move for a good experience. Generally the speed needed is a bit subjective and is significantly affected by design choices, but general wisdom suggests between 150-700mm/s http://www.xsimulator.net/community/threads/minimum-rpm-needed-for-a-2dof.7009/

You can design a motion simulator based on the collective wisdom of the community, without going into detailed calculations. But if your ideas are outside the mainstream it is worth delving into a little mathematics to work out basic speed and force that is available from a particular motor/design combination.

To give some comparable performance context for DC motors and wormdrive gearboxes, here are the specification for the SCN linear actuators, which are often found on commercial simulators:

A SCN6 runs 200mm/sec max. speed, which is a linear velocity of 0.2 m/s: http://miraiintertech.com/home/scn6.php

A SCN 5 runs 400mm/sec max. speed, which is a linear velocity of 0.4 m/s: http://miraiintertech.com/home/scn5.php

For the purpose of the exercise these motors are used as the basis for the example of calculating linear speed and forces, but calculations will be included for different CTC levers and gear ratios: https://www.motiondynamics.com.au/worm-drive-motor-12v-24v-200w-180-rpm-20nm-torque.html

The linear velocity is how fast the motor arm moves for a given Center To Center distance. You can divide the motor torque by the CTC to calculate Newtons. Note the outcome is a trade off between speed and force.

Use this calculator to work out linear speeds from RPMs and CTC lever length: http://www.endmemo.com/physics/rpmlinear.php

A 3600rpm/25:1 with 60mm CTC at 144 rpm gives a linear velocity of 0.9047808 m/s with 333 Newtons.

A 3600rpm/25:1 with 50mm CTC at 144 rpm gives a linear velocity of 0.753984 m/s with 400 Newtons.

A 3600rpm/25:1 with 40mm CTC at 144 rpm gives a linear velocity of 0.6031872 m/s with 500 Newtons.

A 3600rpm/25:1 with 25mm CTC, which is as small as it is practical to go, at 144 rpm gives a linear velocity of 0.376992 m/s with 800 Newtons.

A 3600rpm/50:1 with 40mm CTC at 72 rpm gives a linear velocity of 0.3015936 m/s with 1000 Newtons.

A 3600rpm/60:1 with 40mm CTC at 60 rpm gives a linear velocity of 0.251328 m/s with 1200 Newtons.

You can then take the known Newton for a given CTC, the distance from the motor to the pivot point and the angle used. Run that through the calculator gives you the magnitude of the torque that is possible per motor. Again the angle affects the outcome.

If 500 Newtons is applied 600mm from the pivot at a 90 degree angle then the magnitude of the torque is 300 N m.

If 500 Newtons is applied 600mm from the pivot at a 30 degree angle then the magnitude of the torque is 150 N m.

Disregarding mechanical loss, to know what Newtons it will take to move something it will be Mass (kg) x Acceleration (m/s) = F (N). So to move 100kg at 0.7 m/s needs 70 N. It takes 9.8N per kg to counteract gravity. Keep in mind there is significant mechanical loss in things like the gearbox, depending on the ratio you may want to allow between 10% to 50% loss for worm gears and the greater the gear ratio the higher the % loss is: http://www.meadinfo.org/2008/11/gear-efficiency-spur-helical-bevel-worm.html

If you use pulleys for your simulator ... so you need some torque and speed calculations

Monitors moving or not? Flight - Racing

(Edited) Explanation by BlazinH

A racing simulator needs to be able to maintain fast transitions for the most part so large swings are not needed or desirable where you would need to move the monitors too. Moving monitors just slows things down and can be hard on equipment, especially when attempting something like a large triple screen setup. ‘

Better immersion is felt when the screen stays level. The natural tendency in a turn is to lean your body opposite the turn in real life so leaning in on a simulator just feels correct. But also in real life, leaning in only counteracts g forces and your eyes still stay level with the horizon for the most part. So this also feels correct when the screen stays level because as you lean in your eyes also stay level more or less.

But for flight, and depending on what dofs you use and how much tilt you want, it may be desirable to move monitors also.