Mechanical Structure and Arrangement

The robot is consist from 3 major parts. I call each part "The Cover", "The Frame", and "The Leg-unit". I managed to build them to have enough strength and reduce the weight.

Material for Structure

I chose plastic plate for structural material. This plastic plate is provided from miniature model maker "TAMIYA". It is same as the material that consists miniature model. The characteristic of the material is easy to cut, cheap, easy to glue. They are the reasons why I chose the material.

From the left, plastic plate(plaplate), plastic square bar, and tolls to work plastic.

Adhesive

I use thinner for paint as adhesive of plastic. It smells like liquid adhesive for miniature model. So I think the content of the thinner is similar to the adhesive. The thinner dissolves and combines plastic plates together like one thing. It takes several days for them to gain full strength.

From the left, adhesive for plastic and metal, thinner for paint, and liquid adhesive for plastic.

Cover

This is the part that looks like tank. It is made from plastic plate. The thickness of the plate is 1(mm) and 0.3 (mm). The structure is similar to ship's skeleton.

Underside of the cover. This picture shows how the cover keep its shape.

Frame

The frame is made from plastic plate. (Thickness is 1 mm) The frame is just an empty box that has three bulkheads at the base of a leg-unit.

Birdview of the frame.

Leg-unit

Bird view of the leg-unit.

Layout of servomotors

I think that to increase inertia of parts to be actuated is not good from the point of stability and power consumption of a robot. But all the servomotors are putted inside of each leg-unit for make it easy to change the arrangement of the legs and to reduce the complexity of the mechanism.
No. 0 and No. 2 servo is connected directly to acquire wide range of the joint movement. No.1 servo is connected to No.1 joint via a linkage to support the weight of the robot.

This picture shows the leg-unit and the frame. The robot in this picture is under construction.

Arrangement of the leg-units

I arranged the leg-units in line just not to interfere each other. When the robot supports its own weight with three legs (ex. 0, 2,4), leg 4 must generate two times as much force as leg 0 and 2 generate. So the maximum total weight of the robot is restricted by the power of leg 1 and 4 for this arrangement.

Mechanism of the joints

All the axles that are opposite side of servomotors have a simple mechanism to reduce the cost for the construction and increase productivity. And I don't expect these axles long life. The axle is consists from 3mm-diameter bolt and a hole on plastic plate.

	Joint 0
	This picture shows how servo 0 is mounted.
	This picture shows around joint 0. The leg-unit is mounted to the frame with 4 2mm-diameter bolts.
	Joint 1
	This picture shows how servo 1 is mounted. The servo is mounted to the leg-unit with 2 3mm-diameter bolts. I use a part for RC aircraft to connect the servo-horn and the servo-rod.
	This picture shows around joint 1. I use a part for RC car to connect the leg and the servo-rod.
	Joint 2
	This picture shows how servo 2 is mounted. The servo and the part 3 is connected with 2 2mm-diameter bolts.
	This picture shows the opposite side of servo 2.
	This picture shows the opposite side of servo 2. The joint is aparted.
	This picture shows underside of the leg-unit with no servomotors.

Reinforce of the joints

These pictures show how leg-unit reinforced. The servo-controller for the robot output the signal that makes servomotors to move out of the moving range, when the batteries exhausted. One day, I missed to find the sign of it. And the leg-unit had broken.

	Upper part of the joint 0 is reinforced with aluminum plate of 0.5mm-thichness.
	The joint 1 is reinforced with plastic plate of 1.0mm-thichness. The base of the servo-rod is reinforced with aluminum plate of 0.5mm-thichness.