Final Design

Figure 1: CAD of Final Car Cart Design

Figure 2: Photograph from Front of Completed Car Cart

Figure 3: Photograph from Back of Completed Car Cart

List of Major Components:

- Sliding Front Legs (A)
- Sliding Back Legs (B)
- Pin Locking Mechanism
- Wheels (Ground) (D)
- Wheels (Trunk) (E)
- Cart Basket (F)

Figure 4: CAD of Car Cart with Labeled Parts

Functional Requirements

- Carry a minimum of 23 kg (50 lbs) of groceries
- Fit inside a 2010 Prius Trunk (101 cm x 57 cm x 51 cm)
- Require at most 45 N of force to operate (The same as lifting a 10 lb weight)
- Front and back legs must fold underneath the cart
- Minimize pinch points
- Be able to rotate in trunk of 2010 Prius

Design Solution

The final design of the Car Cart has (4) steps of operation.

(1) Shopping

Figure 5: Car Cart in Shopping Position

While in the upright position with the legs fully extended, a Car Cart is loaded with groceries by a consumer. In this position the legs are locked in place using the pin locking mechanism(C). The center divider in the cart basket(F) can also be slid out for additional grocery space.

(2) Front legs folding, Car Cart halfway into trunk

Figure 7: Car Cart Collapsed

The Car Cart is now rolled into the trunk until the back legs are close to the rear bumper. Nearly all of the weight of the Car Cart and its contents are in the trunk. Then the consumer pulls a second lever, releasing the pin locking mechanism(C) on the sliding back legs(B). This allows the back legs to be rotated backwards manually by the consumer, and then slid underneath the Car Cart. At this point the entire Car Cart is pushed completely into the trunk.

(4)Removing the Car Cart from the trunk

Figure 6: Car Cart with Front Legs Folded Up

The consumer then stores the Car Cart in the trunk. To perform this operation, the front trunk wheels(E) are moved into the trunk. These wheels are now capable of holding the front portion of the Car Cart’s weight. A lever is then pulled at the back of the cart to release the pin locking mechanism(C) on the sliding front legs(A), allowing them to rotate freely. The sliding front legs(A) are pushed against the rear bumper of the car, using the normal force of the car to fold up the front legs underneath the Car Cart as the Car Cart begins to roll into the trunk on the trunk wheels(E). Then, the consumer lifts the sliding front legs(A) to the magnets under the Car Cart to keep them away for the path of the sliding back legs(B).

(3) Back legs folding, cart completely in trunk

Figure 9: CAD Model of Front Leg

Back Leg

Functional Requirements

- Minimize pinch points
- Motion of the legs pulling up and slide in must be simple to operate
- Motion must be smooth and require little force
- Legs need to lock in place and be stable when upright

Support weight of cart

Figure 8: Side View of Car Cart Being Removed

This works the same way as putting the Car Cart into the trunk, but in reverse order. The consumer brings the Car Cart to the edge of the trunk and slides out and rotates the sliding back legs(B) onto the ground behind the car’s rear bumper. At this time the pin locking mechanism(C) locks the back legs(B) into place. Then the consumer pushes down on the front legs(A) to release them from the magnets. Then the Cart is rolled further out of the trunk, allowing the sliding front legs(A) to fall freely into place under the force of gravity. The pin locking mechanism(C) then locks the front legs in place.

Now the Car Cart is free to be moved into the house and unloaded.

Individual Components

Front Leg

Functional Requirements

- Minimize pinch points
- Must fold up when pushed by normal force of bumper
- Hinge need to lock in place and be stable when upright
- Sliding motion must be smooth and require little force
- No damage to bumper must occur