SEEDDown Hill Aerial Transportation TeamDesign Night PresentationMay 4, 2011

Daniel SturnickChris Abbot-KochLance Nichols

Our client Mr. Milson needs a safe and reliable means of transportation from his house to his pond. He is no longer able to access his pond under his own power. The pond is located roughly 245 feet in the linear direction and has a 200 foot vertical drop in elevation. There are obstacles such as wetland and rough terrain standing in the way as well.

245 ft

SolutionCable Cart SystemLet’s take a minute to explore the design

Design Process• Early Leading Design:

Tracked Tramway▫ Pros:

Safety – one the ground Reliability Affordable

▫ Cons: Doesn’t account for

change in elevation, can’t get all the way

High Maintenance▫ Design Change => Go

over the change in elevation, get up in the air

Design Process

• Final Concept: Cable Cart Lift▫ Customizable

Direct Porch and Pond Landings

Through Cart Fit to Scooter

▫ Engineerability Design flexibility

▫ Minimize Material Use▫ Maximize client unique

experience while riding and aesthetic appeal

Constructability

1. Lay out design over field: final measurements

2. Excavate for concrete: Locations for top/bottom/intermediate footers.

3. Form concrete how to get concrete poured (portable mixer vs. chute)

4. Intermediate pole installation5. Install/fix cables6. Install drive/control system7. Install cart on cables

Cart Designs

Design 1

• Length: 5’•Width: 4’•Height: 3’

• Door opens to be 29” wide •Metal frame: 2” thick Aluminum Square Stock

Cart DesignsDesign 2 •Length: 4’

•Width: 3’(Handicap accessible standard)•Height: 3’

•Collapsible front and rear door that turns into on/off ramp•Transparent sides and bottom

Cart Designs

• 3’ x 4’ x 3’ design• Rollers set at pitch angle

of 14o

• Stabilizing Cable Rollers set 2’below cart

• Transparent Walls and Floor.

• Gate deploys into a loading/unloading ramp.

Design 3

ASME A17.1Safety Code for Elevators and Escalators

Key Requirements for Private Residence Inclined Elevators:

• Car must be enclosed on all sides to a height of 42 inches.

• The inside net platform area may not exceed 15ft^2• The fixed cables may not be less then 0.25 inches in

diameter, while the hoist cables may not be less then 0.1875 inches in diameter with both having a factor of safety of 8.

• The driving motor may not be mounted to the same structure as the fixed cable.

• An emergency switch must be located on the car operating panel.

• Hand rope operation shall not be used…

Electric Motor With Worm-Gear Drive Mechanism• Large speed reduction ratio

• Self-locking, the gear cannot reverse drive the worm

•Good for low horsepower applications

•Low cost

•High output torque in a small package

Electrical SystemsACH550

Practically Solves all of our electrical needs:- Ramp Up/Ramp Down- Speed Governor- Forward/Stop/Reverse

Can be connected right to a household circuit breaker.

Electrical Systems- As the cart approaches the upper and lower

landing docks, there will be a pair of limit or rocker switches.

- As the cart rolls over the first switch, it will send a signal to the variable frequency drive (ACH550) to ramp down the motor.

- As the cart rolls over the second switch, it will send a signal to the VFD to stop the motor.

Human Perception of Vibrations

There is a range of frequencies that are physically disturbing to the human body.2.5-10 Hz

Outside of these bounds, there is no disturbance to the human body.

Tension Calculations

The largest deflection will be when the dead and live load are in the middle of the track.

Tension calculations had to be conducted at this point.

Tension Calculations

Frequency – F= (2∏ F)2 m

Stiffness – k = δ =m/k

Where: = Live load + Dead load = Deflection of cable at midpoint

Tension Calculation

By making a right triangle, we can solve for β 2 , since we know the angle the tension cable makes with a horizontal ( 14.47o )

β 2 = 180 – 90 – 14.47 = 75.53o

Knowing β 2 , we also know µ1.

µ1 = 180 – 75.53 = 104.47o

β 2

µ1

Tension Calculations

•Known: δ ,C2 , B1

C2

B2

δ

δ

B1

C1

α1

µ1

µ2 α2

β1

β 2

Upper Tension Angle (90 - µ1)Lower Tension Angle (µ2

- 90)

Tension Calculations

•Now knowing C1 , B2 , δ , µ1 , β 2 , we can apply the Law of Sines and Cosines to solve all remaining unknowns.

C2 = A2 + B2 – 2ABCos(c)Once the tension angles, α1 , α2, the tension

can be found by the equation T =

Footer Calculation

•Sum of the Forces in the X and Y direction and a sum of the moments about point O.

H3

H1

LL/2

mg

Sf2

T

Point O H2

Sf1

Footer CalculationSum of the Forces in the X direction yields

Tcos(14.47) – Sf1 – 2Sf2 = 0

Sum of the Forces in the Y direction yieldsTsin(14.47) – mg = 0

Sum of the moments about point O yieldsTsin(µ)*(3L/8) – Tcos(µ)*(h1 + h3/2) - Sf1 *(h1 / 2) -2Sf2

*(H2 / 2)

- W ((2h2mgL + 6h2mgL + L2 h3 + 4hL2 ) / (8h1 L + 8h2 mg +4Lh3 ))

Support Column Footer Calculations

Sum of the Forces in X and Y will give sufficient information to solve for footers.

Sf

mg

T

T

Safety Features

•Emergency Break on Cart•Speed Governor Acts as an Additional

Safety Break at motor•Safety Switch at Landings so motor can’t

engage with gates open.•Back-up battery for power failure

Future Steps

•Get design out there is search of outside funding

•Transfer design to Professional Engineer•Sign contractor to project•Install lift for David Millson to get back

down to his pond

Any Questions?A special thanks to Professor Eric Hernandez, our mentor on short notice, to David Boehm, with help from Engineering Ventures, and to the excellent clients, the Millson’s for their hospitality and the great design opportunity.