Parts

Torsion Spring

The torsion spring we selected provides a maximum torque of 175 lbin at 120 degrees and costs $7.42.

Here is the link to purchase it:

https://www.amazon.com/Torsion-Handle-Return-Spring-Right/dp/B00V59BGTE/ref=sr_1_3?dchild=1&keywords=heavy+duty+torsion+spring&qid=1622301649&sr=8-3

Motor

The motor we selected provides an operating torque of 23 lbin at 161 rpm. It's max speed is 179 rpm, and it costs $300.

Here is the link to purchase it: https://www.mcmaster.com/2709K17/

Gear Box

Ramp Pieces and Mini Stationary Ramp 

We recommend that these parts be built out of aluminized steel. According to Braunability, it is industry standard to use aluminized steel for vehicle  wheelchair ramps.

Chain

We recommend that the chain be bike chain since the required tension force of our mechanism is about 46 lb, and bike chain can withstand thousands of pounds of tension force. (For further details, see the Final Report)

Sprocket

We recommend that the sprocket be made out of an aluminum alloy. Since the teeth on the sprocket will be experiencing a force the same magnitude as that of the tension force, the sprocket needs to made of a strong material. An aluminum metal alloy will suffice. 

3rd Bar

We chose carbon steel as the material for the 3rd Bar since it needs to support the weight of the ramp while rotating with the motor.