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12S power systems ideas and options

rcbirk21

70cc twin V2
You'll have to give me RPMs because I've not seen any data where batteries help 4.15v per cell under load after a little while at WOT in any of the testing we've done over the last three years. The key is RPMs and prop specs because regardless of what the different meters and logging software says, the true comparison is how fast each motor can spin the the same prop over a decent block of time. With the prop specs and RPMs, we can calculate Watts-out and make a clean comparison. Especially since you're using a meter setup different than Watts-Up, Eagle Tree, and Castle log data.

thank you. i have seen so many people saying "this esc gives me 100 more watts than that esc, so it must be better". it could be an inefficiency that is causing that, basically meaning that you are pulling more amps with no added benefit. but it could also be the complete opposite. rpm is a measurement that is not used enough for electric setups
 

Aeroplayin

70cc twin V2
Here are some things to consider when hearing Watts measurements. Unless a lot of the 6000 Watts is going to heat, magnetic field, noise, light, etc, and the motor is instead operating a high efficiency as all Motrolfly motors do, then even at 83% efficiency, 6000 Watts-in is about 5175 Watts-out, which is just about 7 HP.

The only way to get 7 HP from a electric beechwood prop like the 106g 24x10 PJN is to rotate it about 7350 RPM. If you can do 7 HP and 44 pounds of thrust on a 985 gram motor in a static test after holding WOT for even only 20 seconds, then we need to put a red cape on that motor with a big "S". The only way I see that happening with the 24x10 PJN is on a really efficient 202Kv motor with a little more size and weight to it. I could be wrong byt 7 HP on a motor this size would be extraordinary.
 

gyro

GSN Contributor
Here are some things to consider when hearing Watts measurements. Unless a lot of the 6000 Watts is going to heat, magnetic field, noise, light, etc, and the motor is instead operating a high efficiency as all Motrolfly motors do, then even at 83% efficiency, 6000 Watts-in is about 5175 Watts-out, which is just about 7 HP.

The only way to get 7 HP from a electric beechwood prop like the 106g 24x10 PJN is to rotate it about 7350 RPM. If you can do 7 HP and 44 pounds of thrust on a 985 gram motor in a static test after holding WOT for even only 20 seconds, then we need to put a red cape on that motor with a big "S". The only way I see that happening with the 24x10 PJN is on a really efficient 202Kv motor with a little more size and weight to it. I could be wrong byt 7 HP on a motor this size would be extraordinary.

I can't wait to get it out and get some more measurements for you... so you can appropriately adorn this motor with a red cape.

BTW, my numbers were with a 24x9 Xion Carbon Fiber Propeller. Prop weight was 149g
 

Aeroplayin

70cc twin V2
That could be worse, actually. Although the prop is stiffer, it has less pitch, which means less power at the same RPMs. From what I've seen from experience, less pitch may calculate to needing more RPMs unless the area of the blade is bigger, like with a wide prop, but the added mass may make more RPMs a real task for the motor and voltage source. There is also a possibility that the 149g on a 192Kv on 12S is a high load for the motor, and therefore the high Watts and Amps, but not a relative amount of Work at the shaft (force, distance, time). With a 24x9 149g CF prop, we'll need 7416 RPMs so the 6000 Watts makes sense and I can forget about going gas every again. I'm rooting for you Gary.

:popcorn: :popcorn: :popcorn:
 

Aeroplayin

70cc twin V2
FYI -- for those that don't know me as well as Gary, I'm a BIG Subsonic/Motrolfly fan and have owned nine Motrolfly motors. I actually sold my two Q80 motors and if this ZTW, DM5335-192, Xion 24x9 CF prop is going to spin 7400 RPMs on two decent 6S batteries, on only 135A, I'm in.
 

gyro

GSN Contributor
That could be worse, actually. Although the prop is stiffer, it has less pitch, which means less power at the same RPMs. From what I've seen from experience, less pitch may calculate to needing more RPMs unless the area of the blade is bigger, like with a wide prop, but the added mass may make more RPMs a real task for the motor and voltage source. There is also a possibility that the 149g on a 192Kv on 12S is a high load for the motor, and therefore the high Watts and Amps, but not a relative amount of Work at the shaft (force, distance, time). With a 24x9 149g CF prop, we'll need 7416 RPMs so the 6000 Watts makes sense and I can forget about going gas every again. I'm rooting for you Gary.

:popcorn: :popcorn: :popcorn:

FYI -- for those that don't know me as well as Gary, I'm a BIG Subsonic/Motrolfly fan and have owned nine Motrolfly motors. I actually sold my two Q80 motors and if this ZTW, DM5335-192, Xion 24x9 CF prop is going to spin 7400 RPMs on two decent 6S batteries, on only 135A, I'm in.

I wish we could have gotten more data... It was late in the day after I got off work, and we just wanted to get at least one flight in before I had to get home to my family.

What I can say, (as @Brian Yak Dude was at the sticks) was that the pull out from hover was nasty, (even with throttle limited to 85% of max via EPA in Tx) like 60" EXP on a 4315 at 1800w nasty. Honestly as LEAST as much punch as my GP61 from what it appeared to me...

Now I'm going to shut up until I can back up my boasting with some numbers (or suffer the shame of being wrong).
The Xoar 23x10 PJN should arrive tomorrow, but no later than Saturday, and I know that is a popular prop with some known characteristics for calculations.
 

skibum44

70cc twin V2
That's good news Gary... If I could even get close to 80% of my 60" 4315-480/16x8pjn combo I will be satisfied.
Get any data on the operating temp of the motor?
 

gyro

GSN Contributor
That's good news Gary... If I could even get close to 80% of my 60" 4315-480/16x8pjn combo I will be satisfied.
Get any data on the operating temp of the motor?

yeah, it wasn't hot :)

I had an alarm set for 165 and it never got near it. I'll try and get more temp data this weekend.
 

Tim H.

50cc
OHHHHHHHHHHHH..... I LIKE nasty... From everything I've seen so far (videos and numbers), It looks like this will be one awesome setup.

I'm going to go play with my new motor now...
 
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Aeroplayin

70cc twin V2
I have been fortunate enough to be involved with a group of really great guys that have contributed a great deal to our understanding of motor and prop production. Bryan is certainly one at the top of the list. Last week, I mailed out a box of props that we are testing, and they arrived in MI where TimmyC has been able to test some of them, along with some of his own, on the DM5335-189Kv motor. He sent me the log data for analysis and this is what I have come up with. I hope you find it as valuable as we do in comparing motor, prop, and battery setups.

Here is a clear view of what Tim's data looks like. First, I want to thank Tim for this great data documentation and taking the time to try different props on different batteries. The results are revealing, to say the least. Great data, and if we can continue to get data this well executed, we'll have some true comparisons. This is what I posted on another thread and many may have seen it already.

I took some time to think about how to present this since I didn't want to cherry-pick rows because they don't show a true relative comparison that is valuable to us. Peak values are meaningless since they last for seconds, and are more likely an electrical anomaly. I'm still open to suggestions, but for this round, I ended up with a view that shows two things... how the power starts off, and how the power settles in later, over a short period of timer. How things end up several minutes later are mostly about the battery pack's potential, so skewing prop and Kv values with battery health is something I did not want to include.

The data takes all 100% throttle readings sorted by time. Each power combo is labeled with motor, Kv, prop specs, and the battery specs. The output is represented in two rows per combo. The first row is the average of the top ten rows of data after the first three or four rows are eliminated since they typically have no statistical relativity. The second row represents the average of rows 40 through 50. This will illustrate where the power settles in without going too far into the capabilities of the battery.

The data columns represented are Volts per cell, Amps, Watts, the calculated Watts-out using the calculated pK and recorded RPMs, the calculated HP, the calculated Thrust, the Kv efficiency, which is the difference between the calculated unrestricted RPMs and the recorded RPMs, and the Watts efficiency, which is the margin between the recorded Watts-in and the calculated Watts-out.

Keep in mind that the true power is represented by the power needed to spin a prop of a specific size and load to a specific RPM. We have the prop specs, and we have the load, so the Watts-out and HP represents the output of the motor with that prop.

Values highlighted in red are relatively low values, and high values are highlighted in blue.
 

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