This Linear Actuator was designed for company use; so due to the context of this Instructable, no information will be discussed of the products: they are prototype systems. However I am free to discuss the Linear Actuator itself and how it was built. In addition, I knew that the members of Instructables would appreciate the project.
As I write this, the project is completely finished. I will discuss the Mechanics portion and then the Electrical portion.
How could an Instructables Member benefit from this?
This project demonstrates a practical, sturdy and robust method of lifting and pushing heavy objects; the featured Linear Actuator for example, only stands about 10 inches tall, however it can lift up to 54 pounds! (See the calculations page for the conclusion of this)
This strength is accomplished at a modest price as well; the featured model cost less than $100, not including the electrical. However the electrical is easily emulated through any Micro-controller and simple pieces.
The Instructable even provides suggestions to alternatives for the more intimidating components of the project.
Step 1: Mechanics
There were some mechanical obstacles to overcome when designing the robot. The specs for the project were:
- The robot had to push down and lift up a sealed container to close and open. The weight of the lid on the container does not close the container on its own.
- The project needed to be very robust and strong. It had to run hundreds of times every night.
- The robot shouldn't be ridiculously expensive to create.
- The sealed container did not have to be opened all the way. A couple inch gap would be sufficient.
- The robot needed to hold the bottom of the container down while lifting the lid open. The friction in the seal is enough to lift the entire container.
Learn more about Linear Actuators here: http://en.wikipedia.org/wiki/Linear_actuator
Unfortunately, they are fairly expensive to purchase on their own: roughly $130. Also this Instructable inspired me to build my own:
List of Mechanical Parts:
-  90 RPM Precision DC Motor http://www.servocity.com/html/90_rpm_precision_gear_motor.html
-  3/8" Bore 0.77" Clamping Hub http://www.servocity.com/html/0_770__clamping_hubs.html
-  6mm Bore 0.77" Clamping Hub http://www.servocity.com/html/0_770__clamping_hubs.html
-  Aluminum Motor Mount http://www.servocity.com/html/aluminum_clamping_motor_mount.html
-  1/2" x 36" Square Steel tubing (Home Depot)
-  3/8" x 12" O.D. Threaded Rod (Home Depot)
-  1/8" x 2" x 36" flat Steel (Home Depot)
-  1/4" x 36" O.D. Steel Rod (Home Depot)
-  3" C-clamps (Home Depot)
See the draft document for the design of the linear actuator. The pieces were professionally machined, welded and painted.
The shaft on a Linear Actuator (Shuttle, I'll call it) needed to remain in place and couldn't spin, otherwise the threading would never pass through the nut on the shuttle. So Guiding Rails were implemented in the design. The Guiding Rails hold the shuttle from spinning. They are covered in wheel bearing grease.
DC Motor Diagram provided by Servocity: http://www.servocity.com/html/90_rpm_precision_gear_motor.html