Transcript Skirt Design - Columbia School of Engineering and Applied

The Cialitron
by LevTech
OPERATION
• 30 minutes continuous use by single
operator
• Maximum operator payload of 200lbs
• Steering column mounted thrust throttle
• Operator adjusted lift power
• Standing position
• Dual rudder steering
SAFETY
• Lift power adjusted prior to mounting
• All motors started and checked prior to
•
•
•
•
mounting
Pre-operation inspection of steering and skirt
integrity
Protective gear to be worn
Fan-blade housing
Initial trials conducted with supervision and
balance assistance
LIFT FAN ANALYSIS
• Air flow vs. rpm curves for various fan
manufacturers require a 12 inch fan, 6
and 8 blades, and fixed pitch of 10-15
degrees
• A fan of this size needs to rotate at
approximately 3600 rpm
LIFT ENGINE
• Air pressure and lift calculations with a fan
efficiency of 70% and a motor efficiency
of 85% require a 2.5HP motor
• The lawn mower engine is oversized by
approximately 0.3HP to compensate for
pressure losses in the skirt, fan, and
platform assembly
THRUST ANALYSIS
FORCES ON HOVERCRAFT
• Reynold’s #:
• Air Drag:
Re 
Lv
 4.83105  1000

F
1
2
C D Av c (t )
2
• Exposed surface, plate approximation: 1.1mX1.6m
• μk assumed to be ~ 0.04
THE GOVERNING EQUATION
• Newton’s 2nd Law:
• After solving
•
differential eq. and
taking t to  gives
max velocity
Select a fan that
satisfies the
constraints

V 2
1
2
F  ma


W

C

Av
k
D
c
2
r 2

vc 
t 
V 2
  kW
2
r
1
CD A
2
SELECTION OF FAN AND MOTOR
vc 
t 
(1.25kg / m3 ) (4.484m3 / s ) 2
 0.04(159kg )
 (.381) 2
 6m ph
1
(1)(1.25kg / m 3 )(1.1m 1.6m)
2
• 30’ diam. 2 blades, 6 hp, 1725 max rpm, 9500 max
•
•
cfm, 13 degree pitch
Eq. yields 6 max mph
The important properties that affect hover speed:
weight, kinetic friction, and fan volumetric flow rate and
diameter
SELECTION OF THRUST
ENGINE
• Gas engine with at least
•
•
•
4.5 hp
Engine inefficiency: need
5.5-6 hp
6.4 hp, ¾’’ diameter
shaft, 4 stroke, electric
start, on/off start, choke,
and throttle
16.9 L x 13 W x 13.8 H,
55 lbs
PLATFORM DIMENSIONS
• Dimensions for the plywood platform are
2.5’ x 6.25’
• 6” extended outrigger system maintains
the necessary space for all equipment and
the rider
• Balance was a contributing factor in the
sizing of the platform
BOARD DIMENSIONS
STRESS ANALYSIS
• Max Moment = PL/4
• Max Stress
•
•
MY/I = 535 PSI
Yield Stress of
wood = 4,350 PSI
Safety Factor ~ 8
TOTAL WEIGHT
Board
Outrigger
Structural 2 x 4's
Handlebars
User
Thrust engine/fan
Lift engine/fan
TOTAL
Load (lbs)
23
20
5
2
200
80
20
350
CONTROLS
• Rudders swing side to
•
•
side by moving
handlebars
Rudders attached
with door hinges and
supported by rod
Throttle cables for lift
and thrust engine
attached to
handlebars
SKIRT DESIGN
• Pliable and Durable
• Material: Reinforced
•
•
nylon from a
whitewater raft
Attached to outrigger
and base to form
semi-circle ring
Reinforced holes
BUDGET
1
2
3
4
5
6
Parts We Have/Have Materials For
2x4s
Rudders
Handle Bar
Cables
Skirt
Thrust Fan
Cost
$0.00
$0.00
$0.00
$0.00
$40.00
$0.00
1
2
3
4
5
7
8
9
Parts We Need
Projected Cost
Outrigger
$0.00
Platform
$0.00
Lift Engine
*
$100.00
Lift Fan
$16.00
Thrust Engine
$200.00
Heat Shield
$0.00
Fan Shields
$20.00
Misc
$40.00
Sub Total
$40.00
Sub Total
$376.00
Total Cost
$416.00
*We currently have a useable engine for lift, but, since it cannot be left on the
Cialitron after the final demonstration, we are looking for a permanent engine
WAIVER AND RELEASE
Since our project has a notable
risk of injury to the person and
property of the rider, we thought
it best to draft a waiver releasing
Columbia University from liability
for any/all injury sustained while
riding the Cialitron.
All members of LevTech have
signed this waiver.
Any person wishing to ride the
Cialitron must sign a waiver.
Where do we go from here?
Next Steps:
• starting fabrication of the parts for which we
currently have materials (including the lift
engine)
• ordering parts from McMaster et al.
• continuing our aggressive search for engines that
fit within our budget
• increasing the intensity of our donation campaign
REFERENCES
•
Baker, Russell, et al. “Solar Splash 2002 Columbia University Technical Report Boat #13.” Columbia University, 1 May 2002.
•
Beaty, William J. “Ultra Simple Hovercraft.” Science Hobbyist. 1997 <http://www.amasci.com/amateur/hovercft.html>. 27 Jan 2005.
•
“A Comparison of Different Hovercraft Lift, Thrust and Transmission Systems.” Airlift
Hovercraft.<http://www.airlifthovercraft.com/HC%20Lift%20&%20Thrust%20Systems.htm>. 29 Jan 2005.
•
“Episode 17: Elevator of Death, Levitation Machine.” Mythbusters. 6 Oct 2004. The Discovery Channel, 29 Jan 2005.
•
“Hovercraft Theory.” Ben’s Hovercraft. 24 Sept 2003 <http://www.rchovercraft.com/theory.html>. 27 Jan 2005.
•
Kurtus, Ron. “Determining the Coefficient of Friction”. School for Champions. 15 Dec 2002. 8 Feb 2005. <http://www.school-forchampions.com/science/frictioncoeff.htm>.
•
McMaster-Carr Supply Company. 2005. 8 Feb 2005. <http://www.mcmaster.com/>.
•
P. Ponk Aviation. “Propeller Tip Speed Calculator.” Hoverhawk. 10 Feb 2005. <http://www.hoverhawk.com/propspd.html>.
•
Vawter, Richard. “Drag Force in a Medium.” Western Washington University. Dec 2005. 10 Feb 2005.
<http://www.ac.wwu.edu/~vawter/PhysicsNet/Topics/Dynamics/Forces/-DragForce.html>.
•
White, Frank M. Fluid Mechanics. Fifth Edition. New York: McGraw-Hill, 2002.