Final Design

Design description:

The fixture facilitates two tests of dirt bike frames, the first being a twist test to model the twisting stiffness of the bike, and the second being a bending test to model the bending stiffness of the bike. The bending test imitates the bike's reaction to it landing from a jump with the rider on it, while the twist test would model scenarios like hitting a curb. The fixture is designed to have the bike frame on its side attached to a bracket at the location of the swing arm (back of the frame). In the twist test, the bike's head tube is resting on a swivel pivot that eliminates the bike's vertical translation. For the bending test, the head tube is resting against a post to eliminate rotation about the bracket.

Twist test setup

Twist Test:

The test is conducted by inserting a steel rod into the bike's head tube
The frame is supported by a swivel pivot to eliminate vertical translation
Gym weights are attached to the rod to apply a moment to test the twist stiffness of the frame
Defelction is measured off the head tube with a know distance from the swivel pivot and the weight application

Bending test setup

Bending Test:

The test is done using a bottle jack to imitate the bending load applied to a bike frame through a plate
The frame is supported by an 80/20 extrusion to eliminate rotation about the pin joint
Both the 80/20 extrusion and plate have a rubber sheet to eliminate metal-on-metal contact.
The head tube is supported on a post that is reinforced with steel plates to minimize its deflection
The deflection is measured off the head tube

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