Independently Operated Laptop Mounting System

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Independently Operated Laptop Mounting System

Designers: Jonathan Dennis, Peserai Chinoda
Client Coordinator: Michael Papp, Alabama Department of Rehabilitation Services


The laptop mounting system was designed for a male in his early twenties who has a condition known as spinal muscular atrophy (SMA). This condition is characterized by muscle fatigue and general muscle pain, and generally leads to confinement in a wheelchair.  The client currently has a laptop mounting system that permits him to use the laptop, and which stores the laptop in a rear position in order to avoid obstruction of the client’s view during normal operation of his wheelchair.  The system requires an aide to change the laptop position for use or storage.  As a result, the client’s independence is restricted due to his need for assistance each time he wishes to use or store his computer.

The design was required to be completed in 15 weeks, with a maximum budget of $1,500.  In addition, the system was required to be detachable in order to ensure the original manual system would still be usable in case the new system was to malfunction.  The device was also required to not exceed a clearance of four inches from the side of the client’s wheelchair, in order to not hinder the client’s movement through doorways and the use of his car lift.

Technical Description


The system was designed using a CAD program (Pro-Engineer) to establish the necessary stroke lengths and attachment points for system actuators.  A CAD image of the final design is shown in Figure 5.  The approved design for the laptop system involved new structural stainless steel tubing with an inner diameter of 0.7 inches, an outer diameter of 0.9 inches, and a yield stress of 75,000 psi.  Two linear actuators (Firgelli Automations) were attached to move the arm holding the laptop (3 in. actuator) and the main arm (4 in. actuator), controlled by a timing system and two micro-light switches.  The actuators are resistant to splash and dust damage.   The maximum force produced by the linear actuators is 110 lbs, which was determined to be more than enough to move the laptop from the rear storage location to the front of the wheelchair for use.  The actuators move at 1 inch per second, which translates into a total movement time of 10 seconds from storage to use position of the laptop.  Each one of the actuators was attached to the tubing using special brackets (Firgelli Automations) that allow movement of the arms in an arc.

The torque required to lift the laptop lid was calculated to be 32 in-oz.  A small dual direction rotary motor was used to open and close the laptop (Herbach and Rademan), which produces a maximum torque of 40 inch-oz.  It was mounted on the base of the mount that attached the laptop arm.  The motor was attached to the laptop cover by a small rod with a bracket attached at the end.  This bracket was attached to two thin strips of acetal-delrin plastic that hold the cover in place while it is moving.  A control system composed of a programmable logic controller, relays, one micro-light switch (Tash, Inc.) and three limit switches was used in order to move the arms of the mount in order to open and close the laptop.  The switches were mounted next to the joystick, which controls the wheelchair. Both the actuators and the motor run on the 24 Volt source that powers the client’s wheelchair.

This resulting device fit all design constraints at a cost of approximately $900.  In the event of a malfunction, everything on the mount is detachable.  At the time of the present document, final alterations were being performed prior to delivery to the client.

25 - independent laptop mounting system
Figure 24.  Pro-E drawing of the Independently Operated Laptop Mounting System