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Electric Stunt => Gettin all AMP'ed up! => Topic started by: Larry Renger on December 14, 2014, 04:28:22 PM
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I have been trying to figure out how to search this question, as I am sure it has been answered, but haven't the search skills to find out. So here goes:
If you increase or decrease the prop load on a given system, does the available peak rpm change or only the power draw?
For example, I need a bit more speed and the motor is going flat out. Can I trim the prop and get another 100 rpm?
Either an answer or a link to where the answer is would be welcome! Thanks H^^
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The timers setting will change the speed(rpm), if you trim the prop the timer still tells the esc how fast to spin the motor. Trimming the prop will give more ground clearance, less load and less thrust. Shorten the lines and you pick up a faster lap time.
Bob
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I have been trying to figure out how to search this question, as I am sure it has been answered, but haven't the search skills to find out. So here goes:
If you increase or decrease the prop load on a given system, does the available peak rpm change or only the power draw?
For example, I need a bit more speed and the motor is going flat out. Can I trim the prop and get another 100 rpm?
Either an answer or a link to where the answer is would be welcome! Thanks H^^
My guess is to put in a tad more pitch.
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If you cut prop tips, you will unload motor, and you will reach higher RPM, but it does not work like IC engine. If you unload IC engine, you will get more power (at RPM we fly - means not limited by engine ability) ... while unloaded electric motor does provide LESS power. Means it is hard to expect that smaller prop with lower efficiency on motor with less power can handle model at higher speed. Prop will simply work at higher slippage what will result in slower lap time. So you need to do just opposite. My experience says that if I use 12" prop instead of 11" I can reach higher speed and shorter lap times.
However as Howard wrote, more pitch is trivial solution.
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Is this for a normal stunt plane with a speed-governed ESC, or is this for one of your little half-A things?
In general the answer is still the same -- you need more pitch, or more voltage. But some details may change.
You can run a motor/battery/prop system at an operating point where there's more power to be had by trimming the prop. But this situation can usually be readily discerned by the smoke, and perhaps even sparks, flying out of the motor, wires, ESC and/or battery.
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Hi Larry,
You cannot trim the prop tips to get a little more speed.
Any (small) RPM gain will go hand in hand with a small loss in airspeed.
If you're going to fly faster, you will need to consume more power, not less.
take care,
Dean P.
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Part of the problem is that I am right at the battery power limit, so I found a higher kv motor and trimmed the prop.
I'll post the result when I have a chance to fly the model.