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Old Sep 10, 2011, 10:34 PM
Flyextreme is offline
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Problems with Plettenburg calculations


I have tried a few calcs (with no luck) for the following set-up.

Plettenburg HP 220/25/A1 P6 7:1
Shultz FUT 18.129F
17x18 w/7 degree twist

First of all I don't know how to figure the pitch with the 7 degree twist (guessing around 21 or 22).
Second, The motor/prop calcs don't have this motor on the list as an option.

I am trying to just get some general estimate of what kind of power (amps/watts) a strong 3S...4S...5S ??? would draw...or how many cells it can handle without killing everything. And what kind of numbers can be expected.

Any answers, direction, or help of any kind would be greatly appreciated.

Bill
Last edited by Flyextreme; Sep 10, 2011 at 11:46 PM.
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Old Sep 10, 2011, 11:49 PM
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As there are 4 17x18 RFMs gold,red,green,blue that I know of, that adds to the problem(this is also the power absorption order). The props with +5,and +7 were supposed to be 18in of pitch on those hubs, but that is not how they measure( 18in could be designed pitch with blades at some angle of attack).
so which prop do you have, I have calculated some N100 for the red and green(RPM for 100 watts).
A Pletti 220/37/A1 P4 7:1(your motor has same Kv) was soft on 4S with the 18x19+7 but with the 18.129 4S might be the limit for this motor controller on 4S with the 17x18.
5S on the 220/37 with 16x17 skinny cooked the motor.
Old Sep 11, 2011, 12:09 AM
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Quote:
Originally Posted by David H View Post
As there are 4 17x18 RFMs gold,red,green,blue that I know of, that adds to the problem(this is also the power absorption order). The props with +5,and +7 were supposed to be 18in of pitch on those hubs, but that is not how they measure( 18in could be designed pitch with blades at some angle of attack).
so which prop do you have, I have calculated some N100 for the red and green(RPM for 100 watts).
A Pletti 220/37/A1 P4 7:1(your motor has same Kv) was soft on 4S with the 18x19+7 but with the 18.129 4S might be the limit for this motor controller on 4S with the 17x18.
5S on the 220/37 with 16x17 skinny cooked the motor.
I don't recall what color and don't have the prop on hand to check at the moment.

I never can keep the numbers of all the different motors straight. What's the "37" in the 220/37 and 220/25 mean?

At this point, not knowing the exact prop, it seems that the ESC is the weak link.....not the motor?

What is this motor capable of with the right esc?

So without more info...it seems like....

3S is weak
4S would be better but not great

Does this sound about right?

I'll find out about the prop in the morning.

Thanks so far, Bill
Old Sep 11, 2011, 12:26 AM
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What's the "37" in the 220/37 and 220/25 mean?
this is the rotor length like the 2nd 2 digits in Neu motors. P6 or P4 is the number of pole so 37/25 x6/4=1 i.e. Kv the same.
4S should be fine and good, the smaller motor will get hot quicker so the 17x18 would be about as big a prop you could safely use on this motor.
Old Sep 11, 2011, 12:34 AM
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Originally Posted by David H View Post
this is the rotor length like the 2nd 2 digits in Neu motors. P6 or P4 is the number of pole so 37/25 x6/4=1 i.e. Kv the same.
4S should be fine and good, the smaller motor will get hot quicker so the 17x18 would be about as big a prop you could safely use on this motor.
This has all very helpful. At least now I have "some" idea.

Thanks, Bill
Old Sep 11, 2011, 12:39 PM
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I would recommend you try mailing Pletti, they have great guys that can help you out, and also a few team pilots that probably run this or similar setup, so it would surprise me if you dont get the answers you need.
Old Sep 11, 2011, 02:08 PM
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I would recommend you try mailing Pletti, they have great guys that can help you out, and also a few team pilots that probably run this or similar setup, so it would surprise me if you dont get the answers you need.
That's a very good idea.

Thanks
Old Sep 12, 2011, 01:40 AM
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Quote:
Originally Posted by David H View Post
As there are 4 17x18 RFMs gold,red,green,blue that I know of, that adds to the problem(this is also the power absorption order). The props with +5,and +7 were supposed to be 18in of pitch on those hubs, but that is not how they measure( 18in could be designed pitch with blades at some angle of attack).
so which prop do you have, I have calculated some N100 for the red and green(RPM for 100 watts).
A Pletti 220/37/A1 P4 7:1(your motor has same Kv) was soft on 4S with the 18x19+7 but with the 18.129 4S might be the limit for this motor controller on 4S with the 17x18.
5S on the 220/37 with 16x17 skinny cooked the motor.
If it makes any difference know...it's the "BLUE" RFM.

Bill
Old Sep 12, 2011, 03:24 AM
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Quote:
If it makes any difference know...it's the "BLUE" RFM
That big wide high current drain prop. I am a little worried about the controller with that, but i don,t know for sure
Old Sep 12, 2011, 08:54 AM
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What would be a more conservative prop to use with this ? Would a standard spinner /prop combo be advised?


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