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# Simple Machines in Technical Theatre - PowerPoint PPT Presentation

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. There are three classes of levers: Class 1, Class 2 & Class 3.

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### 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

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

• 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

USITT 2008 – Houston, Texas

• 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

USITT 2008 – Houston, Texas

• 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

USITT 2008 – Houston, Texas

Pop Up Door – Down Position

Pop Up Door – Up Position

USITT 2008 – Houston, Texas

• 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

Effort