Simple Machines in Technical Theatre

1. Levers Simple Machines in Technical Theatre Chip Haas – Technical Director, University of North Carolina Greensboro Drew Pritchard – Technical Direction Student, North Carolina School of the Arts USITT 2008 – Houston, Texas

2. There are three classes of levers: Class 1, Class 2 & Class 3. All three classes have the same three components 1. Fulcrum (‘F’) – the pivot point 2. Load (‘L’) – some kind of weight or resistance 3. Effort (‘E’) – the force that is trying to move the load The differences lie in the location of these components Remember: ‘F’ always proceeds ‘E’, ‘L’ is the only part that moves. USITT 2008 – Houston, Texas

3. Class 1 Lever – ‘LFE’ • Fulcrum is located between the load and the effort • The longer the effort arm (D2), the less force necessary to move the load • Effort Arm(D2) / Resistance Arm (D1)= Load / Effort USITT 2008 – Houston, Texas

4. Common Class 1 Levers USITT 2008 – Houston, Texas

5. Class 2 Lever – ‘FLE’ • Fulcrum is located at one end and the effort is located at the other end of the lever • The load is situated somewhere between those two points. • The closer the load is to the fulcrum, the less force necessary to lift the load • Effort Arm(D1 + D2) / Resistance Arm (D1)= Load / Effort USITT 2008 – Houston, Texas

6. Common Class 2 Lever USITT 2008 – Houston, Texas

7. Class 3 Lever – ‘FEL’ • Fulcrum is located at one end and the load is located at the other end of the lever • The effort is situated somewhere between those two points. • This allows the load to be moved faster, however the effort must be greater than the load • Effort Arm (D1) / Resistance Arm (D1 + D2)= Load / Effort USITT 2008 – Houston, Texas

8. Common Class 3 Levers USITT 2008 – Houston, Texas

9. Failed Use of a Class 1 Lever Pop Up Door – Down Position Pop Up Door – Up Position USITT 2008 – Houston, Texas

10. Problems with this attempt at a lever • Effort arm is shorter than the resistance arm • Made door even heavier to lift – solved using counterweights • Trapdoor platform behind effort arm prevented any extra length to the effort arm • Door Flat too close to end of resistance arm • Couldn’t move high enough – 9” too short • Angle of arm became too steep to keep raising door • Couldn’t extend resistance arm, not enough room • Couldn’t raise fulcrum – structural steel in the way • Door wasn’t heavy enough to come back down, unable to attach lever to pull the door down. How was it solved? - Made it even simpler – eliminated the lever - had crew member raise and lower like a window - Not quite as smooth – locking mechanism was kind of jury rigged USITT 2008 – Houston, Texas

11. Use of a Class 2 Lever – ‘FLE’ Effort Load Fulcrum/ Pivot Point • Example presented is a pivoting wagon unit which is attached to a pivot point. • The pivot acts as a fulcrum, the scenery and people on the unit act as the weight, and the actor moving the unit acts as the effort. • When moved from the end opposite the fulcrum, it acts as a class 2 lever • Effort Arm(D1 + D2) / Resistance Arm (D1)= Load / Effort USITT 2008 – Houston, Texas