Ben Kenobi
Member
I'm planning a self build, am using eCalc extensively to assess battery, prop and motor combinations.
Just as an example I looked at a Turnigy NTM Prop Drive 28-26 1000kv, they recommend a 9x6 prop for 14S - .973kg thrust.
eCalc reckons this motor won't even get off the ground - stating that a 9x6 propeller will stall despite the Turnigy recommendation and a larger but lower pitch prop blows the power out the water - and the flight time, a smaller prop has a hover rpm beyond 80%. Thought this may be down to weight so set the model weight without drive to 100g - and it still claimed that the propeller will stall, tried a few different motors - same result - propeller will stall - either Turnigy are wrong or eCalc is ...
This is just one example I've tried loads of motor / prop combinations and eCalc complains about most of them - over current or too many Watts - reckons I have a longer flight time with a low battery than a normal or fully charged ones - can't figure that one ...
eCalc also changes it's mind about a motor overpower (watts) if you select a 2P pack as opposed to 1P - sorry don't agree with this - adding a parallel DC source does not increase current or watts, simply what is available for the motor to use, it makes no sense. I can add a hundred batteries in parallel and the motor will still only draw the power needed for the work it's doing. I thought this may be down to weight but I selected a 1P and added the weight of 4 cells to the 'without drive' weight and the calculations barely changed but no overpower - but same all up weight.
eCalc is also recommending an optimum rpm that's way beyond APC slow fly limits, on several occasions eCalc has rejected the motor manufacturers prop recommendation, I reduced the 'without drive' weight to a stupid low level and it's opinion didn't change.
Starting to wonder whether I'm expecting too much or eCalc isn't all it's claimed to be.
Just as an example I looked at a Turnigy NTM Prop Drive 28-26 1000kv, they recommend a 9x6 prop for 14S - .973kg thrust.
eCalc reckons this motor won't even get off the ground - stating that a 9x6 propeller will stall despite the Turnigy recommendation and a larger but lower pitch prop blows the power out the water - and the flight time, a smaller prop has a hover rpm beyond 80%. Thought this may be down to weight so set the model weight without drive to 100g - and it still claimed that the propeller will stall, tried a few different motors - same result - propeller will stall - either Turnigy are wrong or eCalc is ...
This is just one example I've tried loads of motor / prop combinations and eCalc complains about most of them - over current or too many Watts - reckons I have a longer flight time with a low battery than a normal or fully charged ones - can't figure that one ...
eCalc also changes it's mind about a motor overpower (watts) if you select a 2P pack as opposed to 1P - sorry don't agree with this - adding a parallel DC source does not increase current or watts, simply what is available for the motor to use, it makes no sense. I can add a hundred batteries in parallel and the motor will still only draw the power needed for the work it's doing. I thought this may be down to weight but I selected a 1P and added the weight of 4 cells to the 'without drive' weight and the calculations barely changed but no overpower - but same all up weight.
eCalc is also recommending an optimum rpm that's way beyond APC slow fly limits, on several occasions eCalc has rejected the motor manufacturers prop recommendation, I reduced the 'without drive' weight to a stupid low level and it's opinion didn't change.
Starting to wonder whether I'm expecting too much or eCalc isn't all it's claimed to be.