Protective Crane Design ET 494 Senior Design Spring

Protective Crane Design ET 494 - Senior Design Spring 2017 Katelyn Cockrell Curtis Blank Jared Bush Zane Jacob

Design Goal • Design a protective crane to be used for protection against falls. • Design and fabricate a sensor and trolley system that will detect the movement of the worker in order to keep the worker directly under the anchor point on the boom of the crane. • The crane needs to be fairly mobile for different terrains and to allow the user to move freely.

Our Goals • Use the skills learned through this project and our curriculum to become a valuable asset to future employers. • Gain a full understanding of project design, planning, and cost estimation. • Develop a safe and cost sensitive crane design.

Tasks Completed Last Semester • Our design uses a popular Jib crane design, along with a trailer, stability jacks, and a motion sensing trolley • We calculated and configured the overall design of the trailer and crane, which included the overall dimensions and materials needed for construction. • We decided to design a crane that would incorporate a moveable trolley and a rotating boom that would follow the worker.

Tasks Completed Last Semester

Spring 2017 Tasks • Completed a full structural analysis of crane structure in COMSOL and Autodesk Inventor. • Designed a redundant locking mechanism for fall arrest. • Successfully designed a trolley system with active position monitoring capabilities. • Fabricated a prototype of the trolley and controls for proof of concept.

Prototype in Action

Trolley • We designed and fabricated a motorized trolley that moves along our I-beam boom

Trolley • The motion of the trolley is controlled by a Pololu Jrk 21 v 3 USB Motor Control and a Honeywell 360 degree hall effect sensor.

Trolley

Trolley • The trolley is chain driven using a 12 V 50 rpm DC motor, a #35 chain, and a permanently attached idler sprocket. • Motor produces around 2 lb. *ft of torque, moving the trolley at 2. 52 in/second

Locking Mechanism • We came up with a design using two inertia locking mechanisms. • The locking mechanisms are placed back to back, with the ends of each strap sewn together. • This allows the two locking mechanisms to function as one, but if one fails, the other can still function as a backup. • 4 feet of strap is stored in each locking mechanism, so even if both mechanisms fail the person will only drop a maximum of 4 feet. ** Prototype contains one locking mechanism**

Spring • To determine the spring needed for our design, we first calculated the potential energy at a fall of two feet. • Using the potential energy found, we then solved for the spring constant at a three-inch spring extension. This ended up being too high, so we found the constant at a six-inch spring extension. • At six inches, the constant was found to be 72, 454. 03 N/m and was more suitable for our design. • We were then able to use the constant to determine the spring force.

Finite Element Analysis • To complete the finite analysis of the entire crane and trailer, we used COMSOL. • Using 0. 25” elements for the mesh, we were able to produce a report showing the total mass of the crane (9, 685 lbs. ) and the center of gravity. • The force load of 3, 965 lbs. was applied and the fixed constraints were used to mimic the cranes contact with the ground. • After the program was ran, Von Mises stress and displacement was produced, telling us whether the structure would buckle or not and the total movement of a given part. • Final Stress Analysis Report (1). pdf

Deliverables Stress analysis of combined full scale model • Primary member: Curtis Blank • Secondary member(s): Jared Bush Design and construction of motor control (Sensing) • Primary member: Curtis Blank • Secondary member(s): Jared Bush Design and construction of motor control (Control) • Primary member: Zane Jacob • Secondary member(s): Katelyn Cockrell

Deliverables cont. Design of impact reducing spring • Primary member: Jared Bush • Secondary member(s): Curtis Blank Design of locking mechanism • Primary member: Katelyn Cockrell • Secondary member(s): Zane Jacob Design of back up locking mechanism • Primary member: Zane Jacob • Secondary member(s): Katelyn Cockrell • ** The construction of the prototype will be a joint effort. **

Protective Crane Design Katelyn Cockrell, Zane Jacob, Curtis Blank, Jared Bush Accomplishments • Designed a mobile safety crane • Completed a stress analysis • Designed and fabricated a mobile trolley • Fabricated a prototype