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Gettin all AMP'ed up!
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Dean Pappas
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Prop optimization
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Topic: Prop optimization (Read 957 times)
TDM
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Prop optimization
«
on:
October 18, 2017, 07:57:27 AM »
We have technology to make light props with multiple blades and there I little discussion on how to max the performance of the system using alternative prop layouts.
We have the 12x6 2B classic set with medium high RPM then we have the 12X4 12X5 in some cases 12x3.75 2B 3B high RPM setups that work well. There is little discussion of the third possibility and that is low RPM high Pitch multi-blade prop. From practical point of view it is certainly easier to make two and three blade props but this is not what I am worried about.
So for the sake of discussion let’s assume equal performance for stunt, I want to compare the alternatives of low pitch high RPM 2B vs high pitch low rpm multi blade props (5-6 blades). Any platform is open for discussion like narrow blades vs wide blades. As long as the goal is to reduce power consumption and as long as it maintains or boosts the performance of existing setups.
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Each goal you meet is a moment of happiness
Happiness is the harmony between what you think and what you do. Mahatma Gandhi
TDM
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Re: Prop optimization
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Reply #1 on:
October 18, 2017, 04:30:12 PM »
I found a prop thrust calculator. It is not perfect but at least i get some raw data to see if this idea has any merit. I think it is a good start.
If you want to play along here it is
http://rcplanes.000webhostapp.com/calc_thrust.htm
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Each goal you meet is a moment of happiness
Happiness is the harmony between what you think and what you do. Mahatma Gandhi
Russell Bond
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Re: Prop optimization
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Reply #2 on:
October 18, 2017, 04:56:08 PM »
I use 13 x 7 three-blade props doing about 7600 rpm static and they work very well with heavier models like mine.
Great speed control using the Igor system.
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Bandolero
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Re: Prop optimization
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Reply #3 on:
October 19, 2017, 07:56:57 AM »
I entered the numbers you provided in the calculator. 3B 13x7 and 7600RPM. I have left everything else default as a matter of fact i have left everything else default for the remainder of the exercise. What i did was to try to find equivalent setups that produce
equal thrust and speed
. After that i found something surprising here. Feel free to enter those number in the calculator.
13x7 3B 7600RPM Results Thrust 118.2oz Speed 60mi/hr Power 768W
13.73x8 3B 6600RPM Results Thrust 118.3oz Speed 60mi/hr Power 713.3W
14.86x8 2B 6600RPM Results Thrust 118.1oz Speed 60mi/hr Power 711.4W
15.48x9 2B 5900RPM Results Thrust 118.2oz Speed 60mi/hr Power 668.2W
16.25x10 2B 5300RPM Results Thrust 118.3oz Speed 60mi/hr Power 652W
I think we are missing the boat here guise. We have not even started to explore the possibilities of Electric. Electric motors are not restricting us to use a narrow RPM range as the IC motors do. We can do anything we want to do. The strange thing is when I was looking at the range of props that can be used in a motor it looked strange that fit them with unreal big props, I think this is why. After I played with these numbers what i found is that Russel can potentially save 15.1% power usage just by changing to another equivalent setup. Moreover lowering the RPM opens the door to go to 3S with a 650KV motor. That means cheaper batteries. I think another advantage is if you go active accelerometer the motor has a softer narrower range from upper and lower limit which makes the transition to the high or low RPM faster. The downside is the current as the system will have to handle more Amps on 3S and you need batteries with higher C rating. That is not bad at all.
I guess a preliminary conclusion 2B is most efficient for now (I didn't try 1B props because is ugly and requires thing i do not want to do). Another conclusion is that as we increase the pitch and lower the RPM we can use less power for sure and potentially cheaper batteries but we have to accommodate larger ESC. Lower RPM also means the gyroscopic precession is cut in half compared to the high RPM low pitch props. Also there is less load on a prop at 5300 compared to 10000+ so tey can still be light enough (sub 20g 15in dia prop) and have the prop stay together without braking.
Traian
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Each goal you meet is a moment of happiness
Happiness is the harmony between what you think and what you do. Mahatma Gandhi
Frank Imbriaco
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At the 69 Willow Grove NATS with J.D. FALCON II
Re: Prop optimization
«
Reply #4 on:
October 20, 2017, 05:03:57 AM »
Not on topic or in the classifieds, but I have many, many new APC Pushers for u-control electric from 9"- 13". Some are limited production and likely won't be produced again.
If you need something in this range , PM me ONLY.
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