2DOF compact race / flight with Oculus Rift

about 6" in from the edge of the upper platform on both sides so when in leftmost or rightmost position during drift the coasters will be close to the edge of the bottom stationary platform. so the coasters will be approx 12-14" apart. i am not concerned with the stability of the rig because i will be using pillow block bearing at the front of the rig which should keep it stable

Hrmm........the pillow block at the distance away from the castor's Will NOT IMO be stable enough with the castors at 12-14" apart. I will bet you will get some "rocking" feeling if you wiggle from side to side.

I currently have the Exact same style/Size of pillow bearing that im using on buddy's Steel rig, However due to buddy's size and subsequent size of the rig, Im actually using 4 castor's 2 out back and 2 up front. My 12" lazy susan which is More Than 1/2 the width of my entire base rig, Has some wobble to it If I step on the front left/right corner. So a Pillowblock 1/5 the size is sure to have a little side to side rocking without Properly spaces castor's.

worst case i could always add something similar to your design like 6"wings" on both sides

adding another set of castors half way between front and rear of the rig or towards the front is not a problem and might be a good idea, i just don't want to make it wider then it currently is

I was more thinking 2 out back and as wide as possible and 2 right up front so essentially All 4 corner's of the Top Portion of the rig are supported by castor's and the ONLY thing the Bearing is doing is providing an axis to spin on.

i hear you, i just want to try without adding the "wings" to the lower frame first

@Nick Moxley, @SeatTime
This project is similar to what I originally was planning to do (except for full frame):
http://www.xsimulator.net/community/threads/my-2dof-with-dc-motors.6314/
I understand that leverage is better with motors located further back, but it seems to be working fine with wiper motors? I don't want to sacrifice the functionality but reducing the size would be nice....

yeah, but yours looks so much sexier...

The less efficient the Overall setup is, the slower the motor's, the More Work the motor's have to do and over all Sure it works, but there are better ways to go about it. If your limited on space, Then it is what it is.

since weather is warming up in the northeast, it is time to buy some square tubing. my choices are
1"x1" with wall thickness 0.12" (3mm) or
1.5"x1.5" with wall thickness of 0.12" (3mm) or
1.5"x1.5" with all thickness 0.18" (4.5mm)

any suggestions, i don't have a feel on how strong it is? thx

Not likely you need the Thick wall stuff, Pending what your doing, you might want some 1.5" some places and other's 1" So its all up to you.

@Nick Moxley , probably pretty close to the drawing I posted earlier in the thread, around 5' is the longest span i need to be able to support.

thanks, @noorbeast
i'll use 1.5"x1.5" with wall thickness of 0.12" (3mm) for the frame, 1"x1" with wall thickness 0.12" (3mm) for the seat

Small update. Purchased all square tubing. Actually found a local steel shop that has all sorts of metals so will be using them during the build. Everything is cut and per-drilled. managed to put base together. Since I am limited on space planning to use it to install PC, power supplies, hardware. This way it is tucked under the sim and is not in the way. Hopefully welds are strong enough, this is my first time welding and I can't really tell the difference. It is certainly has a solid and sturdy fill to it.

Looking good Reko, Welds dont have to be pretty, That's what the grinder is for, and In time you will improve the quality on the first pass. Keep it up.

Trying to figure out motors placement and mounting. Is there a scientific way to figure out arm levers length , or should I just assume 4-6". Thank you.

lever length directly related to your motor speeds and Torque requirements from the motor's. Placement you want it to look something along these lines. Lol already posted these on page 6.

I think my plan is very similar to what is shown on your picture, sketch could be found here:
2DOF compact race / flight with Oculus Rift
motors are similar to what @noorbeast is using, 12V, 80RPM, 50:1 gearboxes. Looks like your arms are about 4" long?