| |
| playfair | Key Veteran - Location: Rochester, NY - |
Continuation from SERVOS: An in depth look - Part 1
In order for a speed vs. torque graph to be really significant, we need to understand what the actual servo loads are during flight.
This is made possible in part by using a data logger to monitor the current draw of a particular servo. The exact servo used isn't important, as long as its current draw vs. output torque is calibrated.
For the field test, I asked my buddy Kyle Stacy to fly his 90 eccpm heli with the logger installed, which uses BLS451 servos on the swash.
The following graphs were created to find the relationship beween current and torque at 6 volts:
The resulting polynomial equation is used to convert current to torque for each reading through a spreadsheet.
The flight data looks similar to that from my R90, where I put the logger on the S9351 collective servo, calibrated for 5.3 volts:
This shows that 60 ounce-inches was easily exceeded during flight in this dedicated position. The eCCPM machine, which monitored the "elevator" servo, peaked at about half of this (the "center" servo on a 120deg eCCPM swash is arguably the hardest worked).
Either way, the graph by itself doesn't tell the whole story, as we have no idea what happened with what input.
To visualize this, I wrote a program to display it in bar-graph form, and synchronized it with the flight video.
The following was the ultimate goal in this "investigation":
In flight Servo Torque Video (43mb wmv file)
The sky is our canvas |
| 04-14-2008 08:10 PM | | | |
I have always asked and wondered about this question...what amount of power is really needed to fly our airplanes and helis. I remember back in the day we would never of dreamed of putting a sub micro (futaba S-133) on an aileron, etc and now a days we put HS-55 on EDF jets, etc.
