salt blaster - engineering design
TRANSCRIPT
The SaltBlaster
Cecilia Robinson, Colby Ye, Emma Lape, Sara Gabriele, Shreya Indukuri, Erik Skarin (TA)
Group 06ENGS 21 – 14W
Ron JohnsonFO&M Grounds
TeamDartmouth College
In one Hanover winter…
16 Snow Days8 Staircases2-4 Rounds16 Steps
6,144 Steps
Frequency
Magnitude
Spreading salt manually on stairs is inefficient in terms of time, salt, and
effort.
Our solution: an automated salt blaster.
State of the Art: Steel Pail
Limited Capacity
Strain on user’s wrist
Uneven salt distribution
Literature reviewRisk Factors
Repetitive motion
Awkward postureHeavy lifting
Occupational Safety & Health Administration
Low capacity
Cannot maneuver stairs
Cleaning time
State of the Art: Walk Behind or Hand Crank
Sprayer
Relevant Products:Fertilizer Blower and Backpack
Blower
Patent Application PCT/JP2012/075405
User ≠ Purchaser
Maintenance Crew Workers in Cold Regions
Overseer of Maintenance Crews
Specification Justification Quantification Test Results
Salt-carrying Capacity
Cutting back on trips to refill salt
spreaders speeds up salting.
Greater than 3 gallons
Close orifices of the salt receptacle and measure how much water the receptacle
can hold
Pass19.4 Gallons
PortabilityThe device must be as easily carried on a staircase as a pail
Greater than or equal to the pail
The user rates the portability on a scale
from 1 to 10
FailPail: 6.2/10
SaltBlaster: 5.2/10
Weight
Any added weight reduces the amount of salt that can be
carried safely.
Under 15 pounds Weigh the device Pass12 pounds
Specification Justification Quantification Test Results
Evenness of Distribution
The more even salt distribution is, the less
salt must be used to effectively clear a
patch of ice.
At least two points higher
than the bucket on a ten point
scale
Photograph the spray from the
bucket and from our device; have users rate which
is more even
PassSaltBlaster:
7.6/10Bucket: 3.1/10
Flow Rate Control
It is important to our user that he be able to target
thick ice with large amounts of salt, while using less elsewhere
Yes or no; you can either control
the flow or notYes/No
FailedUser was unable to control the rate
of salt flow
Physical effort
We do not want our device to promote
unnaturally strained muscles.
Rated less than a 5 on a user
survey, where 5 marks the pail.
User rates physical effort on a scale
from 1 to 10
PassSaltBlaster:1.5/10
Cleaning time
If preparing or maintaining the device for use takes too long,
the time saved by salting is nulled.
Less than 5 minutes to
prepare or stow.
Time how long it takes to maintain each device and
compare
PassMaintenance
includes charging the battery and removing any excess salt.
Specification Justification Quantification Test Results
Salting time(x3)
Increasing the salting speed
lets Ron do his job faster
Must be faster than the bucket system by 25%
Measure how long it takes users to salt one
flight using each device
FailedSaltBlaster is not
faster than the bucket
Safety(y/n)
The device must not promote a
motion or activity that increases the
danger to the user.
Does not reach dangerous levels
of salt speed, noise, or dust
inhalation
Sound does not exceed 93 decibels when measured with an
audiometer; blows salt no faster than 10 m/s;
send dust samples to a lab to find safe levels for
respiration, and measure our device
against these
PassWith ear and eye
protection and a dust mask, SaltBlaster
does not pose unreasonable risk to
the user
Ethicality(y/n)
The solution must adhere to ethical considerations.
Yes/No Consult conscience and code of ethics Pass
Legality(y/n)
The solution must be legal to be
used.Yes/No Consult New Hampshire
state law Pass
Alternatives Matrix
Salt Capacity
Portability
Weight
Evenness of Distribution
Flow Rate Control
Physical Effort
Cleaning Time
Salting time Fun Sum
walk-behind spreader 1 -1 -1 -1 -1 -1 -1 1 0 -4Hand crank spreader -1 1 -1 -1 1 -1 1 -1 -1 -3Hand and bucket -1 1 0 0 1 -1 1 0 0 1Automated Robot 0 1 1 1 0 1 1 1 0 6Gravity-Powered Spreader 0 1 -1 0 0 1 0 0 0 1Walk behind (moves vertically up stairs) 1 -1 -1 1 -1 -1 -1 0 -1 -4Walk behind (moves horizontally across stairs) 1 -1 -1 1 -1 -1 -1 0 -1 -4Salt shaker -1 1 1 1 1 -1 1 -1 -1 1Hand crank spreader on arm -1 1 1 -1 1 -1 1 -1 0 0Salt gun -1 1 0 -1 -1 1 1 -1 1 0Spreader on waist 1 1 1 0 0 1 1 0 0 5Spreader on back 1 1 1 0 0 1 1 0 0 5
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56
Design MethodologyPrototype 2: Salt Belt
Prototype 3: Salt backpack
Prototype 4: Reversed Vacuum
Prototype 5: Vacuum Salt Container
Design MethodologyPrototype 7: Funnel salt hopper
Prototype 6: Vacuum Salt Box
Prototype 8: Backpack Compatible
Prototype 9: Venturi Tube
TESTING THE PROTOTYPE.
Back to the specs:1. Salt carrying capacity2. Evenness of
distribution3. Flow Rate Control4. Weight and Physical
Strain5. Portability6. Cleaning Time7. Salting time8. Fun
19.4 gallons 3 gallons
1. Salt carrying capacity
2. Evenness of distribution3. Flow Rate Control4. Weight and Physical Strain5. Portability6. Cleaning Time7. Salting time8. Fun
DOES OUR PROTOTYPE BEAT THE STATE OF THE ART?
1. Salt carrying capacity2. Evenness of distribution3. Flow Rate Control4. Weight and Physical Strain5. Portability6. Cleaning Time7. Salting time8. Fun
DOES OUR PROTOTYPE BEAT THE STATE OF THE ART?
Prototype Bucket
60
81
68
18
57
100+
1. Salt carrying capacity2. Evenness of distribution3. Flow Rate Control4. Weight and Physical Strain5. Portability6. Cleaning Time7. Salting time8. Fun
DOES OUR PROTOTYPE BEAT THE STATE OF THE ART?
One discharge rate (~90g/s)
Variable discharge rate
1. Salt carrying capacity2. Evenness of distribution3. Flow Rate Control4. Weight and Physical Strain5. Portability6. Cleaning Time7. Salting time8. Fun
DOES OUR PROTOTYPE BEAT THE STATE OF THE ART?
1. Salt carrying capacity2. Evenness of distribution3. Flow Rate Control4. Weight and Physical Strain5. Portability6. Cleaning Time7. Salting time8. Fun
DOES OUR PROTOTYPE BEAT THE STATE OF THE ART?
0
5
10
15
20
25
30
35
40
45
Total torque on body (N*m)
PailSaltBlaster
F=mg
dMA
SS
mass
D
F=mg
1. Salt carrying capacity2. Evenness of distribution3. Flow Rate Control4. Weight and Physical Strain5. Portability6. Cleaning Time7. Salting time8. Fun
DOES OUR PROTOTYPE BEAT THE STATE OF THE ART?
1. Salt carrying capacity2. Evenness of distribution3. Flow Rate Control4. Weight and Physical
Strain5. Portability6. Cleaning Time7. Salting time8. Fun
DOES OUR PROTOTYPE BEAT THE STATE OF THE ART?
Average ratingPrototype: 5.2Bucket: 6.6
• Hits awkwardly in behind
• Hose is short and stiff
• Uneven weight
No maintenance time No maintenance time
1. Salt carrying capacity2. Evenness of distribution3. Flow Rate Control4. Weight and Physical Strain5. Portability6. Cleaning Time7. Salting time8. Fun
DOES OUR PROTOTYPE MATCH THE STATE OF THE ART?
1. Salt carrying capacity2. Evenness of distribution3. Flow Rate Control4. Weight and Physical Strain5. Portability6. Cleaning Time7. Salting time8. Fun
1. Salt carrying capacity2. Evenness of distribution3. Flow Rate Control4. Weight and Physical Strain5. Portability6. Maintenance Time7. Salting time8. Fun
DOES OUR PROTOTYPE MATCH THE STATE OF THE ART?
1. Salt carrying capacity2. Evenness of distribution3. Flow Rate Control4. Weight and Physical Strain5. Portability6. Maintenance Time7. Salting time8. Fun
DOES OUR PROTOTYPE MATCH THE STATE OF THE ART?
User Prototype
A 6
B 9
C 5
D 9
E 8
F 8
G 9
H 6
Average 7.5
The Next Prototype
Clear Plastic Hose
Auger
Nozzle
Motor
Battery
Analysis of prototype
Ideal salt flow rate: 550 cm3/s
Q = vA
gives flow speed in each pipe diameter.
Expected speed: 2.4 m/s
Actual speed: 4.2 m/s
Analysis of prototype
Actual vs. Expected
Trial 1 Trial 2 Trial 3 Ideal0
100
200
300
400
500
600
75.5 77.6 72.8
547
Volumetric rate of salt flow through the tube
Volumetric Flow Rate
Trial
Flow
Rat
e (c
m^3
/s)
Actual vs. Expected
vSalt speed
ACross-sectional area
QVolumetric flow rate
Ethics and Liability • Weight-bearing
3 simple protective measures
My weight How much can I carry?
180 lbs 28 lbs (55% of the bag)
200 lbs 32 lbs (65% of the bag)
220 lbs 36 lbs (70% of the bag)
Sustainability
• Has potential to use less salt
• Lithium ion battery
• PVC and polyethylene
There are some things that money can’t buy.For everything else, there’s McMaster-Carr.
Component
Cost
Straps & Padding
Fan & Power Source
NozzleAssembly
LaborVariable Cost
Hopper $80
$5/half hr.
$10
$2
$50
$172
Funnel, Hose, Piping
$25
The SaltBlaster Experience
Priceless
Variable Costs
Annual Fixed Costs and Market Size
Rent (factory and warehouse) $15,000 Leasing of computers, etc $500
Heat $500 Electricity $400
Marketing/Advertising $2,000 Trade Shows $4,000
Insurance $2,000 Salespeople (1 @ $20K/yr) $20,000
Executive Salaries (1 @ $24K/yr) $24,000
Total Fixed Costs$68,4
00
Per Month$5,70
0
7,500 Organizations20 States
150,000* Purchasers
3-Year Cash Flow ProjectionsMonth Profit
Cumulative Profit Month Profit
Cumulative Profit Month Profit
Cumulative Profit
Jan-15 -$1,493.55 -$1,493.55 Jan-16 $3,444.44 -$26,538.20 Jan-17$12,192.
40 $5,686.72
Feb-15 -$853.55 -$2,347.09 Feb-16 $4,578.24 -$21,959.95 Feb-17$14,200.9
9 $19,887.71
Mar-15 -$149.55 -$2,496.64 Mar-16 $5,825.42 -$16,134.53 Mar-17$16,410.4
4 $36,298.15
Apr-15 -$5,333.55 -$7,830.18 Apr-16 -$2,773.55 -$18,908.08 Apr-17 -$213.55 $36,084.61
May-15 -$5,333.55 -$13,163.73 May-16 -$2,773.55 -$21,681.62 May-17 -$213.55 $35,871.06
Jun-15 -$5,333.55 -$18,497.27 Jun-16 -$2,773.55 -$24,455.17 Jun-17 -$213.55 $35,657.52
Jul-15 -$5,333.55 -$23,830.82 Jul-16 -$2,773.55 -$27,228.71 Jul-17 -$213.55 $35,443.97
Aug-15 -$5,333.55 -$29,164.36 Aug-16 -$2,773.55 -$30,002.26 Aug-17 -$213.55 $35,230.42
Sep-15 -$5,333.55 -$34,497.91 Sep-16 -$2,773.55 -$32,775.81 Sep-17 -$213.55 $35,016.88
Oct-15 $624.85 -$33,873.06 Oct-16 $7,197.32 -$25,578.49 Oct-17$18,840.8
4 $53,857.72
Nov-15 $1,476.69 -$32,396.36 Nov-16 $8,706.41 -$16,872.08 Nov-17$21,514.2
8 $75,372.00
Dec-15 $2,413.72 -$29,982.64Dec-16
$10,366.40 -$6,505.68 Dec-17
$24,455.06 $99,827.07
Break Even Point
(January 2017)
Thank You
Appendix A—Battery Life
Appendix B—Potential for wider distribution
Literature Review
Backpack safetyNo more than 20% of bodyweight
American Academy of Orthopaedic Surgeons, “Backpack safety.”