ba4x
Junior Member
Hey folks,
Thought I would share. Today I used my GoPro camera to generate a dyno plot fot my bike. Check it out! It's not that hard, although it's not too accurate either... :thumbup:
You strap the GoPro (or any video camera) near your dash so it can record your speedometer and tachometer.
Do a pull through second gear on a flat ground, 2k all the way up to redline.
Watch the video and record the bike's speed and RPM while clicking through the frames. I recorded one data point every 10 frames, which is about 3 per second (at 29.97 FPS).
Enter this info into a Google Doc's spread sheet.
Set up a column for time, and one for Kinetic Energy. Time will be frame_count / 29.97 (or your frame rate). Kinetic Energy = (1/2) * mass * speed^2. Make sure the mass is in kg, including the bike, rider, gear, and fuel. Make sure speed is in meters per second (multiply mph by 0.44704 to get m/s). The unit for KE will be Joules.
Set columns for delta time and delta KE. This is the change between each data point in the previous columns you just made. (ie, C2 = A2-A1)
Set up a column for power. This is delta KE / delta time. The unit will be Watts.
The last column is HP, which is approximately Power / 745.
And boom, you have dyno numbers! Plot the HP numbers over the RPM numbers, and you have a chart.
Here's what I came up with:
https://docs.google.com/spreadsheet/ccc?key=0Ao1VS_nTAyx9dHVYQ0NXQnRIZVMxU00xTVFRbHpqUXc
(dyno plot is under "chart 1" at the bottom)
You have to take into account the flatness of the road, the wind drag, and the accuracy of the speedometer when interpreting the chart. 40 HP is a little lower than I expected for my 1992 FZR600 (will try the FZ6 next time). But I made a lot of approximations and didn't adjust for aero drag yet.
Also, I wasn't sure what to use for my speed numbers. The numbers that came right off the speedometer didn't agree with the Tach sometimes. It should be a linear relationship. I generated speed numbers from my tach reading (using a clear data point such as 6k RPM = 35mph). Then I averaged my "RPM speed" and "Speedo speed" numbers for an approximation.
I know this can be done with an accelerometer on the bike, but I figured concrete speed numbers from a camera would be more accurate, considering you'd have to calibrate the accelerometer and account for the shift in the bike while accelerating.
Any ideas to improve on this method?
Nick
Thought I would share. Today I used my GoPro camera to generate a dyno plot fot my bike. Check it out! It's not that hard, although it's not too accurate either... :thumbup:
You strap the GoPro (or any video camera) near your dash so it can record your speedometer and tachometer.
Do a pull through second gear on a flat ground, 2k all the way up to redline.
Watch the video and record the bike's speed and RPM while clicking through the frames. I recorded one data point every 10 frames, which is about 3 per second (at 29.97 FPS).
Enter this info into a Google Doc's spread sheet.
Set up a column for time, and one for Kinetic Energy. Time will be frame_count / 29.97 (or your frame rate). Kinetic Energy = (1/2) * mass * speed^2. Make sure the mass is in kg, including the bike, rider, gear, and fuel. Make sure speed is in meters per second (multiply mph by 0.44704 to get m/s). The unit for KE will be Joules.
Set columns for delta time and delta KE. This is the change between each data point in the previous columns you just made. (ie, C2 = A2-A1)
Set up a column for power. This is delta KE / delta time. The unit will be Watts.
The last column is HP, which is approximately Power / 745.
And boom, you have dyno numbers! Plot the HP numbers over the RPM numbers, and you have a chart.
Here's what I came up with:
https://docs.google.com/spreadsheet/ccc?key=0Ao1VS_nTAyx9dHVYQ0NXQnRIZVMxU00xTVFRbHpqUXc
(dyno plot is under "chart 1" at the bottom)
You have to take into account the flatness of the road, the wind drag, and the accuracy of the speedometer when interpreting the chart. 40 HP is a little lower than I expected for my 1992 FZR600 (will try the FZ6 next time). But I made a lot of approximations and didn't adjust for aero drag yet.
Also, I wasn't sure what to use for my speed numbers. The numbers that came right off the speedometer didn't agree with the Tach sometimes. It should be a linear relationship. I generated speed numbers from my tach reading (using a clear data point such as 6k RPM = 35mph). Then I averaged my "RPM speed" and "Speedo speed" numbers for an approximation.
I know this can be done with an accelerometer on the bike, but I figured concrete speed numbers from a camera would be more accurate, considering you'd have to calibrate the accelerometer and account for the shift in the bike while accelerating.
Any ideas to improve on this method?
Nick
