Feasibility Study of Replacing an Industrial Hydraulic Lift System with an Electro-Mechanical Lift System Critical Design Review Thursday, 21 September 2000 Professors: Dr. Ram & Dr. Buckner Students: Jeremy Bridges & David Herring

Overview  Problem Statement  Potential Candidate Designs  Selecting Candidate Designs  Finalizing Design Solution  Proposed Design Implementation  Conclusion  Questions & Comments

Problem Statement Hydraulic lift systems occasionally leak fluid. This raises environmental issues. A high number of NACCO’s customers are concerned with this issue and have expressed a willingness to pay a little more for an electro- mechanical lift system. NACCO now would like to research the feasibility of replacing this hydraulic lift system with an electro-mechanical lift system in the most cost effective way so the customer can justify the increased cost.

Potential Design Solutions 1.Ball Screw Jac 2.Machine Screw Jac 3.Electric Cylinder Linear Actuator 4.Cam/Cylinder Lift 5.Rack and Pinion 6.Cable/Chain Lift 7.Scissor Truss (Car Jack)

Ball Screw Jac 1. Accurate lifting with little drift 2. Smooth performance 3. Little horsepower required from motor (1/3 Torque needed compared to Machine Screw Jac) 4. Compact system 5. Can operate at high speeds 6. Capable of lifting more than 2 tons that lift desires 7. Horizontal input with vertical output 8. Duty cycle can be extended longer than Machine Screw Jac 9. Corrosion resistant 10. Long predictable life 11. A motor needs to be added 12. Reasonable cost 13. Reasonable size that can work within space constraints

Machine Screw Jac 1. Accurate lifting with little drift 2. Smooth operation 3. Compact system 4. Self-locking during manual operation with no vibration when using 20:1 or higher gear ratio. 5. Will not back-drive during mechanical failure with 20:1 or higher ratio. 6. Corrosion resistant 7. Preferred for static vibration 8. Slower travel speed compared to hydraulic, ball screw, or electric cylinder actuator 9. A motor needs to be added 10. Reasonable cost 11. Reasonable size that can work within space constraints

Electric Cylinder Linear Actuator 1. Extremely accurate 2. High cost 3. Smooth operation 4. Limit switches included 5. Requires input voltage rather than a shaft or other mechanical input 6. Integrated motor 7. Includes ball screw with long life 8. Recommended as ideal solution to hydraulic (per Nook Linear Motion Design Guide, pg. ajec-6) 9. Perfect size that can work within space constraints

Cam/Cylinder Lift 1. Smooth operation 2. Will back-drive without brake during mechanical failure 3. Medium cost 4. Relatively equal travel time compared to hydraulic system 5. Size that may cause problems within space constraints

Rack and Pinion 1. Best during manual operation 2. Mechanical brake preventing back-drive on pinion 3. Low cost 4. Fast travel cycle time 5. Reasonable size that can work within space constraints

Cable/Chain Lift 1. Requires new lift point for lift truck forks 2. High torque 3. Cable wrapping is potential problem 4. If cable or chain break there is a sudden and quick back-drive 5. Medium cost 6. Slower travel time compared to the hydraulic system 7. Reasonable size that can work within space constraints

Scissor Truss (Car Jack) 1. Will not back-drive 2. Can be operated manually 3. Needs large amount of space for mounting 4. Low cost 5. Slower travel time compared to the hydraulic system 6. Size not ideal to work within space constraints

Criteria for Decision Matrix  Cost (5%): evaluated on single mechanism basis for general price ranges  Safety (40%): evaluated on back driving risk during a mechanical failure  Performance (20%) : educated comparison against current hydraulic system  Reliability (35%): evaluated with expected life and risk for a mechanical failure

Candidate Design Selection Scale: 1 = poor 5 = neutral 10 = best

Candidate Design 1.Ball Screw Jac 2.Machine Screw Jac 3.Electric Cylinder Linear Actuator

Selecting Final Design  Size (45%) : evaluate component size and spacing requirements  Ultimate Cost (30%) : overall cost including additional hardware  Ease of Assembly (5%) : implementation of design  Performance (10%) : travel speed and load handling  Safety (10%) : ability to back-drive

Final Design Decision Matrix Scale: 1 = poor 5 = neutral 10 = best

Ball Screw Jac Clevis (2) Drive shaft Aluminum Housing

Ball Screw Jac - Space Issue Fork support unit Ball Screw Jac Interference w/ Drive Unit

Machine Screw Jac Aluminum Housing Drive Shaft Clevis (2)

Machine Screw Jac Lower Mounting Option 1 Upper Linkage Fork Unit Support Machine Screw Jac Lower Mounting Bracket (Option 1) Bracket welded to existing chassis

Option 1:  Stress Analysis must be conducted to select appropriate geometry and ensure structural rigidity  Material must be cut away from interior flanges of fork unit support  Weld strength must be determined

Machine Screw Jac Lower Mounting (Option 2) Upper Lift Linkage Fork Unit Support Machine Screw Jac Lower Mounting Bracket (Option 2) Welded to Chassis

Option 2:  Stress Analysis must be conducted in order to determine correct thickness and geometry of bracket  No material will need to be cut away from fork unit support  Strength will be main concern and testing must be conducted  Possible Interference with drive unit at maximum turn radius

Upper Mounting Bracket Option 1  Will require additional hole drilled in fork unit support and filling of existing hole  May allow additional undesired degrees of freedom

Upper Mounting Bracket Option 2  Additional hole will be drilled and existing hole will be used (No filling will be needed)  More rigid support than Option 1

Machine Screw Jac Assembly Upper linkage Fork Unit Support Machine Screw Jac Upper Mounting Bracket Lower Mounting Bracket

Motor Information Brake Motor  3-Phase, AC Induction  HP depending on desired speed  230/460 VAC Input Voltage  NEMA 56-C Motor Size  Recommended by Nook Industries (~$1000)  Would require DC-AC Inverter (~$500)  Brush DC Motor  HP depending on desired speed  24 VDC Input Voltage  Needs to be researched further Note: More Motor Information will be provided later

Cost of Final Design (Prototype) Machine Screw Jac:$500 AC or DC Motor: $600-$1200 (depending on HP requirements) Limit Switches:$100-$200 Fabrication:$200 (if needed) DC-AC Inverter:$200-$300 (if needed) Misc. Hardware:$ Estimated Total Cost:$1250-$2450 (depending on configuration)

Conclusion  We recommend the Machine Screw Jac as the electromechanical solution  Option 1 - Lower Mounting Bracket  Option 2 - Upper Mounting Bracket  We desire feedback from NACCO on the configuration we have selected before we proceed with prototyping

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