Braking System for
Hospital Bed
Approach
a
Calculations
The original design of the Med-Surg bed depressed a metal
ring onto each of the tires on the bed. These rings held tires
from rotating and swiveling.
D
d
SMpin = 0
Ro/2

Faculty Advisor
Dr. Seugik Baek
Industrial Advior
Chris Siler
Design Team
Nicholas Beechnau
Aaron Cole
Nicholas Nwabueze
Matthew Hays
Pin
(1)
FL
RF
RO/2
FBD of force of ring and lever arm on
tire with final design
RO/2
Background
Stryker Corporation, based out of Portage, Michigan
has been at the forefront of producing quality medical
products and services around the world since being
founded in 1941.
Problem Statement
The goal of this project was to create several innovative
braking designs that could be implemented into
Stryker’s current Med-Surg products or future products.
Design Constraints*
• Current break pedal and actuation must be used.
• Depressing pedal on one side of the bed must activate
entire breaking system.
• Maximum of 60 lbs. of force to actuate braking
system.
• The height and width of the base must not altered.
• Actuation of braking system must withstand a 250 lbs.
force.
• Economically, the new design cannot exceed $131 to
manufacture.
• Design must maintain the current “Ball Point Pen”
actuation characteristic.
• The braking system must have a lifetime of at least 15
years.
*Stryker allowed for many constraints to be ignored to increase number of conceptual designs developed
(2)
• Brainstorming sessions were initially held to generate
ideas for a new braking system.
• Designs were sketched on individual time and were
submitted to the industrial and faculty advisor for quick
feedback.
• Meetings were held twice a week for two hour sessions to
offer and receive advice on designs.
• Initial ideas were more conventional. Feedback from
advisors then led us to develop more unconventional
designs.
• Seventeen designs, which included twenty-one sketches,
were presented to the Stryker team. Both innovative
actuation designs and braking systems were included in
the presentation.
• After presenting the designs to the Stryker team, one was
chosen to be prototyped.
• The design chosen to be prototyped was selected based
on its ability to create instant improvements with only
minor modifications to their current bed.
• The design was optimized then tested and verified as an
effective design for increasing braking efficiency.
• The applied force to the tire (FA ) generated by the
prototype was calculated by assuming static equilibrium
and using equations (1) and (2).
• Using actual values taken from the prototype for D and d,
a theoretical increase of 28.6% in applied force was
calculated.
Final Design
The final design utilized a lever arm
attached to the caster that increased
force due to mechanical advantage.
The brake designed was manufactured and tested at one of
Stryker’s labs. Testing was done by loading a bed with
weight until brake failure was achieved as it sat on a 10°
incline. Due to a non-disclosure agreement exact results
cannot be released, but the new design well exceeded
Stryker’s requirements for brake holding force.