Assembling Simula lower
Put "BatteryCase" with the wide side up on a table in front of you, with the plus sign on the left and the minus sign on the right. and insert the double-sided battery terminals as shown. The fit is tight! A screwdriver or other implement can be put in the small central holes in the battery terminals so you can push down with more force.
Add the soldered battery terminals
Now add the remaining two terminals as shown. Make sure the spring terminal (battery negative) is on the right! These parts go in loosely compared to the previous terminals.
Insert "BatteryCase" into "Lower" and secure with four #2 3/8" screws.
Add BatteryCase side screws and motors
The battery pack is heavy and needs a lot of support. Install four #2 1/4" screws (the short ones) through "Lower" and into "BatteryCase."
Insert the two motors into the motor channels, and be sure the brass motor plate is flush with the outside edge of the motor channel.
Install the Motor Plates
Slide the right Motor Plate into place and install two #2 3/8" screws. Tweezers can be helpful with this step as it's tight in there. Before tightening, reconfirm that the brass motor plates are flush with the outside edge of the motor channel.
A strong magnetic screwdriver can help with the screws, or just put them in place using tweezers and then screw them in. The screws should be medium tight, not enough to crush the Motor Plate plastic. Once installed, the motors may wiggle slightly, but the rubbery treads will pull them taut.
Repeat with the remaining Motor Plate and two #2 3/8" screws on the left side.
Install Mainboard & Analog Sensors
At last some real electronics! Install Mainboard 3.11 and two Analog Distance Sensors. Secure with four #2 1/4" screws as shown. Solder the two Battery Terminals to the Mainboard.
Install the idler wheels
Press the two "IdlerBearing" parts onto the "Lower" hexagonal axle projections. It's a tight fit. Test fit the Idler Wheels as shown and note where plastic will be rubbing against plastic. Apply a light amount of grease on that area. The grease used to lubricate 3D printer moving parts generally works, but use your favorite PLA/ABS lubricant. Don't get any grease on the electric motor axles.
Install two of the Large Screws as shown and hand tighten. Do not tighten so hard that the wheels cannot move, and not so loose that the wheels are floppy.
It's normal for the wheels to stick a bit at first. Rev them back and forth with the heel of your hand to smooth out the contact area and the wheels will begin to move more freely.
Install the Drive Wheels
Take the two Drive Wheels and screw in two of the machine screws. This is the only place on Simula 5 where Machine Screws are used. Look through the axle hole on the drive wheels and tighten until you can just see the screws poking into the axle space, then back up the screws a bit.
Slide the screws onto the motor axles until the wheels are even with the Idler Wheels in the back. Tighten the machine screws until snug and the wheels are held firmly in place on the axles.
Add the Treads
Wipe a little more of the grease you used earlier inside the flexible treads. This may seem a little strange, but it reduces the friction on the gear "teeth" of the tread going into the wheels, and allows Simula to move with less effort.
Congrats, you're done with the Lower Assembly!