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Old Jul 17, 2009, 08:39 AM
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epwierman's Avatar
United States, CA, Los Angeles
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Wisdom?

Quote:
Originally Posted by jjmouris
Steve, i didn't. I am comparing whatever Eric had to mine as he flew mine.
That's correct Joe, you did not.

Some differences on my set ups might factor into your prior observation;
- small 3000 and 3300 packs, vs the larger 4100 and 3700's, I was going for 450 gram pack weight, keeping it light, flying high entries.
- preheating the packs, up to 130F prior to flight (just to see how that would work and effect run times), thats 20F higher than your typical post flight temps. (pushing the limits to see where they are, and crossing that line unfortunately a few times)
- your drivetrain was totally different compared to mine, yours being alot more efficient
-you ran V1.23 and the Gearge modified esc i think, vs my stock esc with 1.55 software.
- my props were 18x19, and 18x21 vs the cut down Sergey Pills clone and rfm's you ran.


Here is some data that might be usefull to others regarding new Neu batts:
-on the new 3700's, I've got 30 or so flights on the original set, and 3 flights on the second set. The original 30 cycle set shows within 1/4 volt under load compared to the new set. The original set have been "abused"; stored full, pushed to peak post flight temps of 145F (due to pre heating).
-These are by far the highest performers I've used to date.
-If these new 3700's are preheated to 100F, flown in a 25 second set up, the peak temp at post flight is about 115F.
-This based on Castle Creations Phoenix 180 / Neu 5S3700 / 1509 1.5D 6.7 and a 17-ish prop.

This weekend, we might be trying the Neu "100 dollar" 5S specials. I haven't put the logger on them yet, but they feel stronger than the version they replaced.

The price sure is right and it may "cool off" one of my set ups that just a bit toooo hot. :-)

So, onto other topics... What are some successful 6S neu combos? Who is doing 6S on castle 180's? In seeing Joe's last set up, and his run times, I was very impressed; that B1-2xT was a ripper!

Eric
-guy trying to see similarities and differences
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Old Jul 17, 2009, 08:52 AM
The props of tomorrow
Varna , Bulgaria
Joined Feb 2007
945 Posts
Can you guys post some fly data on the cells you have ?

I will appreciate if someone post here F5B discharge graph of the Neu 35/70 C.
I will run 1512 1D 4S setup and want to buy the best batteries.
Only logged data requested.
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Old Jul 17, 2009, 09:09 AM
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George,

If you can, also note the ouside air and pack temps prior to flight.

I just use the mini display for the Unilogger, so I am unable to post graphs.

In case it helps, the 1509 1.5D 6.7 on 5S3700's preheated to 100F, resulted in an average of 17.2 volts with a load; climb that starts off at 275 amps and tapers down to 225 after 1.5 seconds.

I do have the usb cable if someone wants to walk me through the steps of getting the data onto the pc.


Thanks,

Eric
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Old Jul 17, 2009, 09:22 AM
Needs to do 52 legs !!
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Verenigd Koninkrijk, Fareham
Joined Aug 2008
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Yeah, i should really get some of those new 5S 40C Neu packs to really play around and compare. But what is the point?

The 5S 3850mah and 6S 3300mah Pro Power packs i am using now come out so cold and deliver constant performance climb after climb. I think i'll just try and figure out a motor prop combo that will give me the motor run time i am after.

I guess only when these fail will i wonder...... maybe the Neu's would have lasted longer?!..... who knows!

At the moment i am more concentrating on cleaning up my plane. The B1 double carbon wing might still be almost as new (even after trimming some corn fields), it has no linkage covers and the fuselage is basically a flying brick with no spinner cap and pointy corners.

I give you a hint;
http://www.ackfoto.nl/rompmal.htm

Note that along with the smaller packs we can get away with now, we might need slimmer fuselage's (Go one 6 style) to fit around them perfectly.

Ain't new battery's fun?!
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Old Jul 17, 2009, 11:48 AM
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Quote:
Originally Posted by epwierman
George,

If you can, also note the ouside air and pack temps prior to flight.

I just use the mini display for the Unilogger, so I am unable to post graphs.

I do have the usb cable if someone wants to walk me through the steps of getting the data onto the pc.

Eric
About 25C I would guess, but it is not important. The IR is so low that at the end of the flight the voltage is falling due to pack emptying. Heating at the beginning will only exacerbate the difference in voltage between the beginning and the end.

The web site www.f5b.co.uk has all the instructions you need. The Unilog stuff has been translated into English by Dick. I would suggest (of course I would) that you skip the Excel stuf and just install the UniF5B program also described on the site. This is simpler and tells you all you want to know. The important thing is to install the USB driver first as described in the Unilog documentation. Before plugging in the USB. Do not let Windows install it automatically for you. If it is already there (FTDI USB serial interface) delete it as the default version three times slower.

I use the CC125 on 6S. This is the equivalent in losses to a CC180 on 5S and 1.5 times better than a CC180 on 4S.
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Old Jul 17, 2009, 12:48 PM
Needs to do 52 legs !!
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George, so what would be the math on a CC180 on 6S vs 4S on a Schulze 200 ?!



Joe, who thinks we need bigger more efficient motors!
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Old Jul 17, 2009, 01:40 PM
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I can't say as it is not like for like. It depends on the resistance of the Schulze which depends on the niumber of FETs, their type, how hard they are driven, the size and thickness of the PCB tracks, and how optimal is the software.

I think we need efficient motors, ideally 100%, but to what extent they have to be bigger? RPM comes into the efficiency equation, and high rpm motors such as Remo's can be as efficient as larger lower rpm motors.
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Old Jul 17, 2009, 02:36 PM
Needs to do 52 legs !!
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Yeah, so having asked Steve for a 1910 or 1912 motor for F5B and not getting any reply. What other big motors could we try?

I think this should prove to be interresting!
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Old Jul 17, 2009, 03:53 PM
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George or others,

I haven't done the sums but looking at the resistance figures quoted in the Neu calculator for an ESC it doesn't seem to me that the ESC resistance or the difference between 4S and 5S is going to change the amount of motor runtime by even 1 second for 1750 watt minutes. Or have I got that wrong?
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Old Jul 18, 2009, 03:06 AM
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It is not about motor run time, it is about efficiency.
Low efficiency hits us two ways: firstly it reduces the number of legs which can be done with a given amount of energy, 1750 watt.minutes in our case. Secondly it increases the heating inside the controller/motor/plane which can have delterious effects.

Losses, the flip side of efficiency, come in part from the resistance of the circuit, I^2*R. If the total resistance (not including the battery or wiring before the limiter) is 5 milliohms and the current is 200A, then the loss is 200 watts for say 30 seconds run time, so 100 watt.minutes. More than enough for all those who ran out of motor in Biella to have finished easily.

Comparing 4S with 6S, the current has to go up by 1.5 to get the same power. So the resistive losses go up by 2.25. So the resistance (motor, controller, wiring) has to be better than halved. The CC180 only has 50% more resistance reducing stuff than the CC125, and 8mm connectors are also only part way.
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Old Jul 18, 2009, 03:06 AM
The props of tomorrow
Varna , Bulgaria
Joined Feb 2007
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Hello guys , will someone post flight logs please ?
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Old Jul 18, 2009, 07:45 AM
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George

Thanks for a clear explanation. Can you use 8 mm connectors with the limiter? I guess you have to take off the old connectors and put on some new ones. 56% more resistance losses in going from 5S to 4S.
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Old Jul 18, 2009, 08:18 AM
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The Netherlands, NH, Amsterdam
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Hey Jos,

it seems like my idea and our discussion on the dutch thread of efficient flying and efficient drives is waking you up.
In theory, the more amps you put in a drive, the less efficient it gets.
In a few weeks I have my Schulze 18.200 and a Markus-RC SL300.
I will try to compare it but i think the loss is not in the controller but in the motor.
I think the man that can tell us all about the motors and efficiency is Ralph Okon (Powercroco).
But he hates gears....

Gert-Jan
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Old Jul 18, 2009, 09:55 AM
Needs to do 52 legs !!
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Me waking up?!

You are right.... the only thing that gets hot is the motor. So there are the losses.

The losses on the prop you can not measure with a temperature gun unfortionately.
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Old Jul 18, 2009, 12:39 PM
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Quote:
Originally Posted by jjmouris
Yeah, so having asked Steve for a 1910 or 1912 motor for F5B and not getting any reply. What other big motors could we try?

I think this should prove to be interresting!
Lehner had a formula for the optimum weight of motor, Wim is the expert. I think it was
weight = power * 10000 / rpm
For 30 sec motor run the average power is 3500 watts.
For Remo's 90000 rpm this gives 388 gm motor.
So you are right that our motors are too small for maximum efficiency, especially at lower rpms. But two points:
Firstly such optima are flat so a factor of two won't affect the efficiency too much.
Secondly extra weight wastes watt.minutes pulling it round the course. There are two types of drag, profile drag and induced drag. Profile drag depends on the total frontal area and the streamlining such as tail servos hanging out in the breeze.
Induced drag comes from the weight, a little to keep the plane up in the straights and a lot to heave it round in the turns. So you have to balance the efficiency gain of a heaver motor against the drag losses of the extra weight.
Increasing the rpm of the motor is the best way out which is why we use a gearbox.
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