Step 1: Install 123D Design App on Your IPad2
I then recommend you go through all the tutorials online for using the iPad app like I did. It makes things a TON easier.
I would also recommend you sign up for the free account at 123D app's website so you can save your projects to the cloud and open them up in the web browser version, iOS, and Mac and PC versions.
Everywhere you see a rectangular shape like for the walls and floor and top started as a simple cube. I just used the scale tool to resize them to very thin with the orange height handle then drug out the width and length handles to get them to the right size.
You have to lay them on the grid in order to measure them if you want them to be a certain size. From what I could tell there was no way in the iPad app to specify the width, height, and lengh to an exact number. When you use the scale tool to change the size and just tap on one of the handles it will display the "calculator" looking dialog to type in a number to resize but that is a scale factor like "1" will be 100% of the size or "no change" where "2" would be TWICE the size and make the object two times bigger in that direction.
So I had to make the walls on the grid next to the floor in order to measure them then I used the rotate tool to rotate them 90 degrees to stand them up. Note that once I placed one wall I just did a long press on the first wall to get the context menu and picked Duplicate to make the second wall right next to it. I could then use the move tool on that second wall and tap and drag on the arrow that would move it directly sideways to the other side of the floor. I also use this move tool and drag the arrows to move the walls and top far away from the model in order to show what's on the inside. I also haven't figured out a good door to put on the side yet so for now it's just a wall.
Step 2: Add the Chair
I then used the fillet tool then tapped on the top, front edge line of the seat back then just tapped and drug the little white handle that appears back until it looked nice. I did the same for the seat back edge lines and again for the top, front line of the seat bottom.
Then I just placed a cube on both sides of the chair bottom by tapping on the cube in the bottom drawer then tapped on the side of thee chair bottom to stick it there. then I used the scale tool on each to set their size so that the right side for the joystick was up as high as a normal armrest might be then the left side down lower where you might rest your hand on a car's gearshift for example.
I then used the combine tool to tap on each cube then another cube. Then tapped on the other cube then the other until it was all combined into a single object I could move around and scale as I wanted.
I then made rails on the floor for the chair to slide forward and back on for people that might be taller or shorter than most by using the Primitives - Extended - C Shape object. I rotated it 90 degrees in two directions so it would sit with the C shape pointing up like a rail. Then I just used the scale tool to make them small and long. After making the first one for the left side I just long pressed on it and tapped Duplicate from the menu. I then used the move tool on the new one and moved it over to the other side. Then I lowered the chair onto the rails.
Step 3: Make the Joystick and Throttle
I made the throttle first by making the cube base and scaling it to be flat but fit on the cube side we made on the left side of the chair earlier. I then placed a cylinder on the grid then used the rotate tool and tapped the cylinder. Then orbited around and tapped the rotate handle that would make it lay down on the grid and typed 90 in the input and rotated it 90 degrees. then I used the orange handle of the scale tool to shrink it down so it would look like a wheel of sorts. Then I used the magnet tool and tapped the curved outer face of the cylinder then the top face of the base to make it snap on there. Then I used the move tool on the cylinder to move it down into the base until the top edge of the cylinder was sticking out. I then picked another cylinder out of the drawer and tapped on the edge of the wheel to place it there. I then had to use the scale tool to shrink it down by the white corner handle so it would scale down evenly making sure to drag the orange handle up to make it taller as it got skinnier. That was my vertical part of the stick. I used the rotate tool to rotate it -12 degrees so it would lean forward a bit. I then placed another 90 degree rotated cylinder on the top face of that cylinder and used the move tool to center it and make it sink onto the vertical stick so it would look flush. I finally used the combine tool to combine it into one object but make sure you combine everything to the base last. If you do like I did and combine it to the rotated stick part then your move tool will make the move arrows line up on a rotate x y z plane so it won't move as nice. Once it was all combined I could use the move tool to move it all at once to the spot I wanted on the left cube of the chair.
To make the joystick I also used a cube for the base and scaled it to be flat and the size I needed. Then I used the Dome from the Primitives - Extended drawer on the bottom and placed that on the base. I had to use the scale tool and its white corner handles to shrink it down to fit, also making sure to drag the orange height handle up as I went. I then grabbed a filleted cylinder from that same Extended drawer and placed it on top of the dome. I then used the rotate tool to rotate it forward -12 degrees and the move tool to sink it down into the dome a bit. I was then able to use the combine tool to put them all together into a single object and move it onto the cube on the right side of the chair.
Step 4: Make the Pedals
I then long pressed on the pedal and picked Duplicate from the menu. It created a copy right next to it so I just had to use the move tool to drag the sideways arrow right over to the other pedal holder.
Step 5: Make the Screens
These were just cubes that were picked from the drawer then tapped on the front wall face to snap them there. Then I used the scale tool to set them to the sizes that looked right. I then snapped an extra cube on the face of all three cubes then sized it to be thin like a frame. Then I used the Hollow tool on these top frame cubes and just drug the white handle around until it looked right.
Step 6: Finally 3D Print Your Scale Model
At this point you'll have to save this project to the cloud using the save arrow button. You'll need a free account on the 123D website then log in to that. I would set the switch to private (public NO) at the top then give it a name you'll remember.
Then you can use the windows or mac app to get your model and export it to a file type that shapeways or a 3D printer would need.