The purpose of this tutorial is to show how the original Max '95 mobile robot base was constructed using mostly parts from your local hardware store. The Max '95 is a 12" x 12" mobile robot base.

Zagros Robotics sells several models of mobile robot base. This model is the great-grandfather of the Max '97 mobile robot base. The drawings are available one the company website and can be used a guide. However, they are not required.

Max '97 drawings:

Max 97 Base Drawing
Max 97 Deck Drawing

Step 1: Purchase Your Materials

Most of the materials should be available at your local hardware store. The one exception are the drive motors.

Base Material - 3/8" Plywood
- We has the hardware store cut a 2ft x 2ft sheet of plywood into 12 inch squares.
- One advantage of plywood it is cheap.
- One disadvantage of plywood is your robot will be made out of wood.
- Various type of plastic may also be available, these can also be used, but are more expense.
- Zagros sells ABS in various shapes and sizes
3 inch diameter swivel caster
(8) 3/8 inch coupling nuts (each should be about 1 inch in length)
(4) 1/4-20 bolts, 3-1/2 inches long
(4) 1/4-20 nuts
(20) 1/4-20 washers
(8) #10/32 screws, 1 inch long.
(8) #10 nuts
(8) #10 lock washers (optional)
(16) #10 washers
4 ft of 1/2 inch PVC pipe
(4) 3/8 inch bolts - 10 inches long.
(4) 3/8 inch nuts
(8) 3/8 inch washers

Any DC motors can be used, however we recommend motors with specification similar to these:

Voltage 12vdc
Torque 10in-lb
Speed 25rpm

Motors in this range allow the robot to move at a controllable speed and carry around a 30 lbs payload.

Motors can be purchased from Zagros Robotics here:

http://www.zagrosrobotics.com/shop/item.aspx?itemi...

A complete drive unit is also avaliable:

http://www.zagrosrobotics.com/shop/item.aspx?itemi...

Step 2: Drill Holes for the Base and Deck Mounting Hardware

This robot will have one base deck and a second upper deck. If you want a 3rd or 4th deck, you can also drill them during this step.

Compare each side of the plywood decks, select the least attractive side to make your measurement marks.
The deck mounting holes are 1 in from each side of the deck. Place one in each corner.
After the deck is marked, clamp all of the future decks together.
First, drill a small pilot hole.
Next drill a whole for a 3/8" bolt with a 7/16" drill bit. (If you are using a hand drill, you may want to add another step with a 1/4" drill bit.

Step 3: Add the Caster Wheel Mounting Holes

Unclamp the decks and put one aside.
Measure and mark the center of the caster mounting plate
Measure and mark the center of the 12 inch deck. Note, if you have the hardware store cut your plywood - it will probably not be exactly 12 inches.
Position the caster in the center of the deck and adjust it's position until the caster will only stick out an inch or so when swiveled out.
Mark the center of the caster mounting plate holes
Use a 5/16 inch drill bit to drill (4) holes for 1/4 inch bolts. (If using a hand drill, drill a pilot hole first)

Step 4: Mount Your Drive Units

If using the Max drive units.

Draw a line 1-1/2 inches from the front of the deck. This should keep the wheels tucked complete under the base.
Draw a line 2 inches from the each side of the deck.
Position the drives on the base and confirm they are parallel to each other.
Mark the position of the mounting holes.
Remove the drives
Use a 13/64 inch drill bit to drill the mounting holes for each drive.

Step 5: Mount the Hardware

Flip the deck over and mount the drive wheels with the #10 hardware.
Mount the caster wheel using the 1/4-20 hardware.
- drop the 3-1/2inch bolts through the caster mounting holes while holding it upside down.
- grab the caster wheel in a way that your hand holds the bolts in place and flip over.
- place (2) coupling nuts and (3) washers on each bolt.
- bolt the caster to the bottom of the deck.
Add or remove washers from the caster as required to level the deck.

1/2 inch aluminum tube can also be used for the caster spacers. This should also be available at your hardware store.

Step 6: Drill Drive Motor Wire Way

Before mounting the upper deck, drill a hole through the base for the drive motor lead wires.

Step 7: Mount the Upper Deck

Cut the 1/2 inch PVC pipe into 8-1/4 inch sections. (This assumes 3/8inch plywood, adjust length if plywood in thicker or thiner)
Drop all four the of 3/8 inch bolts into the upper deck mounting holes.
Sandwich the PVC spacers between the two decks and secure with the 3/8 inch hardware.

These spacers can be cut in 1/2 to add a 3rd deck if required.

24 inch or 36 inch threaded rod can also be used in place of the 10 inch bolts. Longer PVC spacers can be used and the robot can be much taller.