**Team Members**

Jack Moldave

Anthony Harris

Justin Chung

**BASE**

The
base measures at 7.5 inches tall and maintains the 6Ó x 6Ó floor with a width
and length of 5 inches. We altered our truss structure into a 2 layered box configuration. To minimize the deflection we
attached a 8.5 inch transverse support along each of
the 4 sides of the base. To minimize total weight we only used one support per
side since the desired stability was reached. Another major design
consideration was that each beam was bent 90 degrees into an L-shape. The new
bent members allowed applied forces to be better distributed and brought our
base to the level of rigidity that we had desired. The final modification was
the implementation of an extension from the base to the crane arm. We used
triangular supports (4Ó x 5Ó 3.75Ó) to allow the arm to line up directly with
the obstacle window.

**CRANE ARM**

We
designed our lifting member with a triangular cross-section(3.5Ó
x 3.5Ó x 3.0Ó) as opposed to our
rectangular base. We expanded our transverse support modification in the base(8.5Ó) to a full-blown truss pattern throughout the
arm(30.5Ó). As we found it necessary we added more cross-bars to distribute
the forces and minimize the overall deflection created by the given weight and
bearing. The trusses we decided to use for the greatest effect and material
conservation for the arm are 30-30-120 degrees in measure. We didn't feel that
the added strength for more trusses would be necessary and we were correct in
our assumption. Initially our arm was too wide to make it through the small
window on the playing field. We compensated by utilizing the flexibility of the
aluminum and bending the arm as it extended so that its cross section became smaller(1.5Ó x 1.5Ó x 2.0Ó) towards the end near the weight.
Like the base we only utilized bent L-shaped members throughout the arm's
construction. We found that doing this allowed us to be more conservative with
the amount of truss sections we created and the amount of material we used as
well as producing a very strong frame that is significantly resistant to
bending.

Here is a picture of the square base and the triangular truss we used to
support the servo motor and lifting arm.

**LIFTING MEMBER**

For
the actual lifting piece that makes contact with the weight we simply used a thin
strip of aluminum that loops around the bolt that is attached to the weight. We also used an aluminum counterweight weighing
about 5 ounces. The motor connects to the member at 3 inches away from where
the ribbon attaches to the weight leaving 7 inches for the counterweight to
create an opposing moment. From the first design review we made adjustments to
the counterweight and lifting member in order to reduce the failure rate when
lifting the weight and bearing. On a minor note we also took a second look at
our base's floor so that our project fits properly in the clamp. In conclusion
our crane successfully lifted the weight under the specifications given to us.

**Theoretical
Predictions **

**2.5 inch arm**

**Given Stats: In a theoretical world.**** The maximum
the motor could lift. **

, , , Calculate distance of lever arm x is the distance of
the motor from the sliding collar weight. So the maximum
theoretical lift would be So assuming that the
torque is linear throughout the lift, the percent of torque used to lift it 2Ó
is |

Real World Calculations

, , , We decided to use a lever arm of 2.5 inches to account for deflection,
non optimal servo motor performance, and a general
safety net. So the maximum
theoretical lift would be Our final lift result
was 2.5Ó so it was a good thing we used a smaller lever arm. The overall efficiency
of our system compared to the theoretical value is fairly small. We are technically
using the full 90¡ to lift the weight, but we are only using 31.4% of the
motors theoretical value. Significant amounts of energy are lost in the
bending of the beams, inefficiency of the motor, and general bending of the
lever arm and system. |

The following are pictures of our overall crane and a close up of the
lifting mechanism.