physics of stationary and dynamic ergometers by: nathaniel brown tim beauregard andrew diorio bryan...
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Physics of Stationary and Dynamic Ergometers
By: Nathaniel BrownTim BeauregardAndrew DiOrioBryan Taylor
Ergometer Background
• Exercise machine that measures work done pulling a chain.
• Used to simulate the motion of rowing a boat on water.
• Different types of ergs = different feel and performance.
Static Ergometer
Static: Concept2 Ergometer Diagram of Static Ergometer
• The standard for testing a rower’s power output.• Does not mimic the feeling of a boat well.
Dynamic Ergometer
Dynamic: Oartec Slider Ergometer Diagram of Oartec Slider
• Better mimics the motion of a boat.• Times are generally faster than stationary.• Higher stroke rates are easier.
Problem Statement
• Develop an explanation for differences in measured performance for different ergometers.
• Create a “rule-of-thumb” formula for adjusting
scores on different ergometers.
Approach to Problem Solving
• Measure locations of selected points on rower and erg using video and image tracking.
• Find accelerations based on data.
• Use the accelerations and masses to find work and power.
Assumptions
• Forces only act in x-direction.
• Static center of masses based on three points at the ankle, hip, and neck.
• Frictionless environment.
Expectations
• Static ergometer will waste more energy accelerating masses than the dynamic ergometer.
• The dynamic ergometer will simulate motion
on water better than the static ergometer.
Equipment
• 1 Ortec Slider Ergometer• 1 Stationary 2 Concept Ergometer• Video Camera• Image Tracking Software (Tracker)• Matlab
Tracker
• Open source
• Tracks motion of points using image recognition algorithms
• Exported Data into csv files
Dynamic Erg with Tracker
Procedure
• Four, one minute pieces on each type of erg
• Two pieces at 20 spm, two at 30 spm
• Approximately even splits for each stroke rate (1:52 for 20 spm, 1:37 for 30 spm)
Results
Results (Cont.)
Results (Cont.)
• Rule of thumb: Static wastes 5 more watts for every beat above 16 spm.
Conclusion
• The dynamic erg is more efficient than the static erg.
• The efficiency gap increases with an increase in stroke rating.
• The efficiency gap has a significant effect on performance.
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