Go modify > Change Parameter

Edit certain specification like height,length, weight and thickness to desire parameter

Create new component, name "Front plate"

Create sketch on the ZX plane

Create a rectangle with dimension of "length" and "height"(dimension use follow parameter)

Extrude the image with distance of "thickness"

Next, create tabs on both sides and bottom, create rectangle(whixh is the tabs),dimension using the parameter(length of tabs on width is wtabs or length of tabs on height is htabs) by thickness

Extrude cut the tabs with dimension: thickness

Create a new component on the right face of the front plate

Create rectangle and colinear to constraint the side and dimension the width

Using same setting on desgin front, similar steps, add tabs but now only do on the width, or bottom face of the right plate will do

Extrude and rectangular pattern to form the tabs

Create midplane on both component, mirror both components(front and side plate) (for mirror front, no need to mirror the holes created)

Combine cut all the plates at side in order to create joins.

Create component for making a cover on the bottom surface of either front or side component

Create a rectangle and extrude with a dimension of "thicknes"(parameter)

Combine the base using all other 4 plates as cutting tool to cut the cover.

Create component for making a cover on the top surface of either front or side component

Create a rectangle and extrude with a dimension of "thicknes"(parameter)

Combine the cover using all other 4 plates as cutting tool to cut the cover.

Create sketch on the top surface of the cover design holes in order to place the motor.

The image show distance is 40 because thats the distance from center of gear to another, so please check again on the gears center distance before hand.

Include in the design of Sensor Box to modify the top in order to place the ultrasonic sensor, combine to cut the cover using the sensor box.

The arrow indicates to create some space for the wires to go through.

Next, create and extrude a ring at the hole created previously, with the ring outer diameter is the gear hole size diameter -0.7mm / -0.8mm so the gear able to use the ring as support to rotate.

Box Design: