salt blaster - engineering design

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


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.


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

1234

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


Prototype Bucket

60

81

68

18

57

100+

One discharge rate (~90g/s)

Variable discharge rate



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


Average ratingPrototype: 5.2Bucket: 6.6

• Hits awkwardly in behind

• Hose is short and stiff

• Uneven weight

No maintenance time No maintenance time


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


1. Salt carrying capacity2. Evenness of distribution3. Flow Rate Control4. Weight and Physical Strain5. Portability6. Maintenance Time7. Salting time8. Fun


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)



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.”