Design Considerations & Resources

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:

[IMG]

: #108

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
http://www.blocklayer.com/pulley-belteng.aspx

: #89

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.

: #49

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