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

2. 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.
Alex

3. 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.
Alex

4. 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.

5. Tasks Completed Last Semester

6. 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.

7. Prototype in Action

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

9. Trolley
The motion of the trolley is controlled by a Pololu Jrk 21v3 USB Motor Control and a Honeywell 360 degree hall effect sensor.

10. Trolley

11. Trolley
The trolley is chain driven using a 12V 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

12. ** Prototype contains one 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**

13. 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, N/m and was more suitable for our design.
We were then able to use the constant to determine the spring force.

14. 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

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

16. 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.**
Katelyn

17. 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
Alex