|Jan 06, 2013, 05:37 AM|
Data graph from flight yesterday.....
Mega motor 16/40/1 with Kontronic 5.2:1 GB - AJM prop (10 x 19)
Zippy 5S 1800 40C packs - CC Icelite 100A ESC
|Jan 06, 2013, 07:10 AM|
Ive sent some special layup ones up to Bruce for testing. Hopefully he tries them out soon. Lets just say the layup is so crazy i'm pretty no one has built a prop this way before But I have high hopes that finally there will be a sawtooth blade for the masses. People wont have to worry about breaking them anymore. Atleast thats the idea
|Jan 06, 2013, 07:10 AM|
just watched your log,have some questions about it.
Rpm is pretty high about 36000 1/min.
As the mega is 6-pole but you setted the logger to 2-pole i assume it should be 12000 1/min which is still pretty high for the prop.
Not sure if you run the 4,2:1 gearbox as setted in the logger or the 5,2 GB as shown in your other logs and pictures.
With 5,2 GB rpm would be arround 9600 which seems more plausible but a bit low for the power.
Voltage is pretty low, less than 3,3V per cell, even my 1400 Gens keep almost 3,5V per cell at comparable loads.
Do you pre-heat your packs before flight?
OK, australia,maybe not compellingly necessary at the moment
I usually heat my packs to 45° which gives a nice performance step and longer battery life.
Currentdrop seem to be lower than usual with a 6pole,the graph looks kind of "draggy",was this straight levelflight?
Looks more or less like a dive at 375,5 sec,would be nice to have altitude at the log.
I dont have personal experience with the AJ prop, but one teammate tried it and found it to have quite a poor acceleration compared to other doublesquare ones, maybe it just needs longer than 8sec to speed out completly?
Last race in germany one competitor used the el nino in the F5d-Limited class(about 300w).
He competed in my race so maybe its possible to compare it to the Flipper or the Bathlet.
General behavior is smooth and handling is nice,but he had several times the problem that stab fell of at landinghit,which is not that nice during a raceweekend.
It was obviously much slower than Flipper and Bathlet, but it was his first race and he had to run lower power to get enough runtime to finish the race,due to the lack of experience.
But especially out of the corner it seem to loose a lot of speed and the airframe is quite "noisy".
But this may be solved with finetuning CG and trows.
I would not try to get the glasfiber version to 200mph, i think wing torsion will be the main problem.
maybe torsion is already limiting your speed,from the datas you showed it should be already faster than 180mph.
|Jan 06, 2013, 08:57 AM|
|Jan 06, 2013, 05:23 PM|
Thanks for that.. nice detailed diagnosis. I actually had a few errors in my posting.. I just double-checked the motor/GB - It's a Mega 16/40/1 and the GB is a Kontronic 5.2:1 (sorry for the wrong info).
The reason for the short blips - I think the cofg was back a little after changing from DD setup to the geared one - so the aircraft was not that longitudinally stable in flight - it was doing a bit of bucking. I will address that for the next set of testing.
I have posted the full zip file of the data log with corrected values .... hopefully that will give better info?
I do have the BB sawtooths to use, as well as a different size set of the AJM prop.
But I did note the Mega was very hot when it came down. The El Nino has no cooling slots etc.. so maybe I need to look at adding some to take the edge off. The temperature that day was 36 degrees C.. so probably the packs didn't need any pre-warming. Using HK Zippy 1800 5S 40C lipos, but they may have been abused a little... will order some fresh packs and re-try. I don't really want to spend the extra on the TP or similar packs... not at this stage as we are not racing this class yet.
Interesting to hear of the characteristics of the airframe from actual race conditions... thanks for that info... very few seem to be flying this model.
I will keep posting logs etc... and will get more accurate radared speeds as the aircraft becomes more predictable to fly (can fly lower and straighter to unit).
|Jan 07, 2013, 01:29 PM|
To be honest, i am not able to open your file, data analysis is part of my job but there i usually have some younger guys to support me with all this computer stuff.
i would have expected the mega to take these loads easy, maybe its not at the same eta level than a neu or kontronik but it can take a lot of overload and its quite flexible and easy in handling.
Can you post your controller settigs, maybe there are improvement-options in timing?
50000 rpm 6-pole at the inputshaft may already challenge some controllers!:
Regarding your log i assume you use a CC-controller so rpm should not be the problem.
Be aware that short bursts like shown in the log stresses your powerunit much more than a continuous run.
Check out your log, start current is about 35% higher than at full speed,(usually its even higher;up to 45% but it depends on your start-speed), a 60 sec run would generate 30%less load in average than 6 times 10sec runs!!!
After watching again your log,especially the current-power drop over excelerating looks to me like high weight or overpitched prop, but without altitude graph its hard to say.
As the fiber- el nino and your components does not seem heavy ( i guess its in the neighbourhood of 1000g?) i would try some other props.
But these doublesquare folders are not easy to calculate,seems like the manufacturers do not really take pitch and diameter numbers too serious!
As mentioned in other threads the big foldersetups are much more difficult to set proper up than the tiny screemers, small changes in pitch and diameter have massive effects in current draw and speed.
Would be nice to see some comparison to the sawtooth, from dimesions it might be much bigger, but only power-draw vs speedreadings would give an impression about performance.
The new GM 9x21,5 also seem to be promising,although it looks at the paper even more pitched than the AJ, i will get results soon.
|Jun 03, 2013, 04:57 AM|
Had some more flights on Saturday.. much more comfortable with the speed now having done some heat racing with the Reverbs... Still fighting the power on - diving issue. think I will just have to add a mix to the elevator on throttle.
Graph below (only 100% power section) - Had climbed out on lower power.
|Jun 03, 2013, 08:36 PM|
The launch problems have been put down to the launcher not throwing it hard enough. Launches great with a proper throw..
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