asm student night
TRANSCRIPT
The RiderThaylor Cacador
Kevin Chow
Patrick Neville
Tashi Sangpo
Brandon Shafran
ASM International, Long Island Chapter, Student Night November 18th 2015 1
Problem Statement
The static nature of the system transfers a great amount of energy to the user, when moving on rough surfaces.
Standard designs are nearly impossible to move over curbs.
Motion requires a lot of energy from the user.
Standard wheelchairs lack comfort and outdoors efficiency
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GoalsDesign a wheelchair modification that improves motion and comfort without interfering with mobility of original design
Be able to go over a 8 inches street curb. (Curbs range from 4-8 in)Reduce the amount of vibration when traveling over pavement.Require less effort from user to travel. Maintain 360 degrees rotation freedom.Keep model within ADA standard dimension. 3
Market Availability
● $3000-$5000● Improves propulsion ● No vibration improvement● Fits most wheelchair
models
● Hard to assemble● Impedes accessibility ● Does not conform with
ADA dimension standards● For outdoors only.
● $3000● Improves propulsion● Not foldable ● Front wheel impedes
accessibility
proactiv-gmbh.com/adaptive_bike_nj1gear.mit.edu/Research_Projects/LFC.htmlhttp://wijitcom.ipage.com/images/wijit.jpg
WijitDrive Mechanism Attachment
ProactivAdaptive Trike
Freedom ChairVersatile Wheelchair Model
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Drive Mechanism Testing
● Lever assisted wheelchairs allow a user to put in less force for more motion than a standard design.
● Efficiency testing will show how our design compares with the efficiency of other lever designs on the market.
● This qualitatively shows how users of a wheelchair react to riding up an incline with different mechanisms.
5http://www.rehab.research.va.gov/jour/2013/5010/jrrd-2013-02-0034.html
Vibration Testing
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● Comfort over pavement, small bumps and terrain can be measured with vibration tests.
● Accelerometers are placed on the wheelchair and measures acceleration in x, y and z.
● This qualitatively shows a more comfortable ride by comparing the data from a standard wheelchair to our design.
http://www.rehab.research.va.gov/jour/08/45/7/pdf/requejo.pdf
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Standard ModelGoal: Take a standard wheelchair and modify
some of its characteristics to improve its performance outdoors.
Traveller L4 by Everest & Jennings
● Manual Folding● Weighs 32 lb● Load capacity: 300 lb● Represents what a Medicare wheelchair is
today
Modified Design Third Wheel in the Back ● Improves accessibility in and out of
chair. ● Reduces vibration. ● For balance of the system, front
wheels must be moved forward from original position.
Lever Drive System● Adjustable lever length to
manipulate output torque to the gear train.
● Gear train system with calculated gear train ratio and mechanical advantage.
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Assembly
Gray ComponentsOriginal Standard Wheelchair FrameYellow ComponentsAre connectors either welded or clamped to the frame Blue Components (Addition)Assembly parts Red PartsANSI Fixtures (Bolts and Nuts)Green Gear train system
Representation of modified parts from original model
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12”
Gear Train Ratio
Wheel
21
AB
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Drive Mechanism Design for #40 ANSI chain, standard in most bicycles.
(American National Standards Institute) An average velocity of a travelling
wheelchair is around 3-4 mph approximately =70 in/s
Since: V=ωr where: ω= angular velocity ω
wheel=5.8 rad/s ≈ 1 rev/s
● Since sprocket 2 is concentric to the wheel, as the lever moves from point A to point B. ω
wheel=ω
2
ω2=5.8 rad/s
● The two sprockets are connected by a chain. Therefore, have the same linear velocity.
V1=V
29.5 in
Mechanical Efficiency
Wheel
21
A B
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Continued: V1=V
2Since: V=ωrω
1r
1=ω
2r
2
We assume a rotational speed of 1/2 rps of the input sprocket 1 to be reasonable due to design characteristics.
ω1=3.2 rad/s
Then, Gear Ratio (GR) = r2 /r
1 = ω
1/ω
2
GR = 0.55 ≈ 1/2For sprockets r
2/r
1=N
2/N
1 where N= # of
teethChosen sprockets after calculations:
N1= 35 & N
2=19
Compliance with ADA Standards● These are some of the basic
standards given by the ADA, which
was created with the Americans
with Disabilities Act in 1990.
● The ADA have a variety of standards
regarding whose disabilities require
the need of a wheelchair.
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Telephone and Intercom Placement
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Dimensions
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Balance Challenge
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● The primary position of the center of mass will be behind the hub of the front wheels.
● This center of mass is due to change during entering and leaving the wheelchair.
● To counter this, the seat will be reclined by a certain angle, θ.
Materials Selection & CalculationForce
max = pound force (lbf) * cos(θ)
= 300 lbs * cos (20°) = 280 lbs
σmax
= (½) Forcemax
/ Area = (½) 280 lbs / ((π * (0.25 in) 2)-(π * (0.13 in) 2) = 1000 psi
Safety Factor: 3.0σ
yield > 3.0 * σ
max
σyield
> 3.0 * 1000 psi = 3000 psi or 21 MPa
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4130 Alloy Steel
- easy to weld
- σyield
= 70,000 psi
- within our budget
- galvanized (corrosion resistant
Safety Feature
1800wheelchair.com
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User Safety is Priority● Rear anti-tippers will be used as front anti-tippers
to prevent forward tipping. ● They have a adjustable height. ● User can change to prefered setting depending on
their comfort with the equipment.
Suspension Implementation
● Coilover shock absorbers consist of a kind of twin tube shock absorber which has been mounted a large metal coil.
● Allow adjustment between the distance between a level surface and any contact of the tire by using a threaded spring perch.
● Chromed springs. 2in. maximum compression
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Suspension calculation
F = -kx
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● Apply hooke’s law to determine spring’s stiffness
applied from the load of the wheelchair
● Standard wheelchair weight + modification = 40 lbs ● Maximum load capacity of our = 260 lb ● x = amount by which the free end of the spring was
displaced from its position.x=(8in-6in)= 2in
PE=mgh=(300lb)(8in)= 2400 lb.in
PEspring
=½kx2
k=2(2400lb.in)/(2in)2 = 1200 lb/in
Single Back Wheel
Curb
A.
B.
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www.northerntool.com www.walgreens.com http://www.zipp.com/
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Questions & Answers