Total time: 
2 hours 
Objectives: 
* To demonstrate and discuss the mechanical principles of torque, momentum, inertia end sprocket ratios * To discuss the application of these mechanical principles to pedal/treadlepowered devices * To practice facilitation skills 
Resources: 
* Meriam, Mechanics * Attachment III5A, "Demonstration of Torque" * Attachment III5B, "Demonstration of Momentum and Inertia" * Attachment III5C, "Demonstration of Sprocket. Ratios" * Attachment III5D, ''Ratio Designs" Worksheet; 
Materials: 
Newsprint and felttip pens; materials listed in attachments. 
Trainer Notes
This session will require advance preparation. Part of this preparation should have been made at the end of Session 4 with the selection of three participants to present the demonstrations in this session. Each of the three participants/facilitators should choose one of the three demonstrations and be provided with the corresponding attachment. (See Resources.)
Be certain to allow sufficient time before the session for the facilitators to prepare their demonstrations and provide them with the materials necessary. If the participant feels that he/she can present the principle in a more effective manner, encourage the development of that demonstration. Explain they they have 15 minutes to present the demonstration and 20 minutes for followup discussion.
Plan for time at the end of each of the three demonstrations for feedback on the facilitation skills of the individual giving the demonstration. You can encourage this feedback by asking the facilitator what he or she feels was best during the demonstration and where improvements could be made.

Step 1. (40 minutes)
Have the participant/facilitator demonstrate the concept of torque as outlined in Attachment III5A.
Trainer Notes
You should fill in any points missed or not covered to your satisfaction during all three of the demonstrations or discussions.

Step 2. (40 minutes) Have the second participant/facilitator demonstrate the effects of momentum and inertia as outlined in Attachment III5B.
Step 3. (40 minutes) Have the third participant/facilitator demonstrate the principles of sprocket ratios as outlined in Attachment III5C.
Trainer Notes
At the end of this session, distribute Attachment III5D, the "Ratio Designs" worksheets, explaining that the worksheets should be completed for the next day's session.

DEMONSTRATION OF TORQUE
Through this demonstration, the participants will gain practical understanding and experience with the effects of torque and its relationship to pedal/treadle power devices.
Total time: 
40 minutes 
Materials: 
2 boards of equal length and nails 
Procedures:
Step 1.
(15 minutes/Steps 14) Nail 2 boards together in a Vshape.
Step 2.
Have a participant grasp the two boards at the middle and attempt to pull them apart by opening the V. Point out the force required to move the boards.
Step 3.
Repeat the experiment by having another participant grasp the ends of the boards.
Step 4.
Compare the force required to move the boards when they are grasped at different distances from the juncture.
Note
The conclusion will be that it takes much less force to pull boards apart at the end mark, i.e., equal forces exert more effect on the juncture when they are at a greater distance from it.
Encourage the participants to express the relationship between applied force and the distance at which it is exerted, using the boards as an example. Such a relationship describes torque and may be expressed in the following formula:
torque = force applied x distance of applied force to the point of juncture

Step 5. (20 minutes)
Facilitate a discussion of the methods that might be used to minimize the effects of torque.
Step 6. (5 minutes)
Encourage feedback on your facilitation skills.
DEMONSTRATION OF MOMENTUM AND INPRTIA
This demonstration will enable the participants to experience the effects, parameters and relationships of momentum and inertia to pedal/treadle power.
Total time: 
40 minutes 
Materials: 
Wheel or disk, axle, 4 weights (total weight approximately equals that of the wheel or disk) 
Procedures:
Step 1. (15 minutes/Steps 15)
Mount the wheel or disk on a shaft so that it can be easily rotated.
Step 2.
Have a participant rotate the wheel at an approximate set speed, taking note of the force required to start it rotating and the time it takes to coast to a stop after the force is withdrawn. Then, have a participant again rotate the wheel up to speed and then try to stop it quickly, noting the force required to stop the motion.
Step 3.
Distribute four weights equally around the outside of the wheel and repeat the procedure.
Step 4.
Ask the participant to note the effects of the added weights.
Note
The conclusion will be that it takes more effort to start the wheel rotating with the added weight but that the wheel rotates freely for a longer time.

Step 5.
Encourage a discussion of the relationships between parameters of momentum (which are the initial weight of the wheel and its added weights), the wheel's rotational velocity and its radius.
Step 6.
(20 minutes) Facilitate a discussion of the application of the principles of momentum and inertia to pedal/ treadle design.
Step 7.
(5 minutes) Encourage feedback on your facilitation skills.
DEMONSTRATION OF SPROCKET RATIONS
This demonstration allows the participants to experience the effects, parameters and relationship of sprocket ratio to pedal/ treadle power.
Total time: 
40 minutes 
Materials: 
Multiple speed bicycle 
Procedures:
Step 1. (15 minutes/Steps 14)
Put the bicycle in low gear and lift the rear wheel off the ground. Ask the participants to observe how many times the rear wheel rotates for each revolution of the pedal crank.
Step 2.
Change the gear ratio to a higher gear and repeat Step 1.
Note
In the above two steps, ask the participants to observe the relative difference in force necessary to turn the pedal crank.

Step 3.
Have the participants develop the formula which defines the relationship between sprocket sizes and rotation speed.
Note
This relationship is defined as: _{}

Step 4.
Facilitate a discussion of the potential mechanical advantage when sprockets are oriented in the proper fashion.
Note
The conclusion will be that transferring energy from a small to a large sprocket results in a velocity loss but in a mechanical advantage or gain.

Step 5. (20 minutes)
Facilitate a discussion of the application of the principles of sprocket ratios to pedal/treadle power.
Step 6. (5 minutes)
Encourage feedback on your facilitation skills.
RATIO DESIGNS WORKSHEET
1. Given the mobile dyne pod designed to power a food grinder that operates at 100 revolutions per minute, size the sprocket that will be connected to the grinder shaft:
Available sprockets:
35 teeth
42 teeth
48 teeth
18 teeth
22 teeth
30 teeth
RATIO DESIGNS WORKSHEET 1
2. Given the stationary dynapod, size the two sprockets in question to provide the required 400 revolutions per minute output in low gear on the bicycle.
1st gear: 1.4/1
2nd gear: 1/1
3rd gear: 111.4
RATIO DESIGNS WORKSHEET 2
3. Design a mobile dyne pod unit that will provide the driven output shaft speed of approximately 1,200 revolutions per minute necessary to power a bench grinder. The bicycle used will have a front sprocket of 48 teeth and a rear hub sprocket of 18 teeth.
Available sprockets:
35 teeth
42 teeth
48 teeth
18 teeth
22 teeth
30 teeth
RATIO DESIGNS WORKSHEET 3
4. Design a system which will deliver power in a linear mode for a water pump designed to operate at 15 cycles per minute. Pedaling speed of 60 revolutions per minute will be used with a belt/pulley combination. The pump has a driving rod throw of 8".