Current feeling on U7 and equivalent KDE?

Carapau

Carapau

Tek care, lambs ont road, MRF Moderator
Im tottally with Econfly on this althought what I would say is that the KDE Esc and Motor combo is way more reactive than the Tiger equivelent. As for Castle I suspect they make excellent ESCs now but for a long time in the single heli world they were known rather than Castle Creations as Castle Cremations due to the amount of failures and resulting fires that were happening at the time. If you want the very best ESC forget any of these and look at Kontroniks.
 

econfly

econfly

Member
Totally agree about the responsiveness of the KDE ESC/Motor combination as compared to Tiger --- that was the driver for me to pick KDE for my X8 build.
 

Pumpkinguy

Pumpkinguy

Member
I have my own opinion on that. Yes kde way more responsive but what does that really mean? For a full sized camera ship do you want it to have a sports car feel or do you want it to be a little soft and forgiving? Think about this. I don't think it is really a benifit here. Maybe it is the exact opposite.

For a racing quad absolutely. That lightning fast throttle response us what you want. Cheers.
 

econfly

econfly

Member
It's a good point. My thinking (with no objective measurement) is that the flight controller is really controlling the response to stick input or deviation from desired position/orientation. Ideally, the ESC/Motor combination would respond the the flight controller quickly and consistently, and then it's up to the FC to adjust the signal in order to get the flight characteristics desired. But, I admit, I am completely making this up. If any given FC isn't smart enough to take advantage of responsiveness at the ESC/Motor level (or, worse, assumes a less responsive system than exists) then this is all wrong. Ultimately, the proof is in the results, and if something works (or not) that's all that matters. I can't report on my X8 results because I can't find time to finish it. Hopefully soon.
 

Old Man

Old Man

Active Member
Responsiveness can be somewhat tailored using transmitter exponential. The larger, heavier stuff needs the maximum/fastest response available to deal with larger props in a constantly changing wind environment.
 

Hexacrafter

Hexacrafter

Manufacturer
Been watching this thread...
Still waiting for anyone to address the original purpose.....
Comparison/ Info on KDE 5215-435 kva to T-motor U7 -420 kva... NOT the 490 kva....
This is apple to apples.... except the completely different motor geometry (pole count), which from our experience switches high ESC temperature with high motor temperature as the excess mechanical energy MUST be dispersed somewhere.... at the ESC, the motor or both...
I would really like to have someone post Real world Motor & ESC temperatures, props used, thrust obtained.. etc.... from the KDE.
I have MANY clients using the U7 in both 420 & 490..... our experience are very positive when using 17" max props & the T80a ESC as recommended by T-Motor.
Some are posting here I see.
I have not one client currently using KDE, so it would be interesting to hear actual facts from the KDE user camp on motor & ESC temperatures...
A couple other of things..... experiences & opinions...you are welcome to have a differing opinion.
1. I do not like the faster Simon K style ESC for a Heavy lift platform. From my flying experiences of MANY rigs... both ours & others..... The faster ESC seem to add to the aircraft "nervousness" in windy and gusty conditions. I have taken two identical rigs... one with T series ESC and one with Simon K..... and flown both under similar conditions..... A2 & WKM FC.... The T series are much smoother & less "nervous". I like to describe it like the difference between a jet fighter & a 747.... I want a 747 when flying the camera during most incidents. The 747 can still fly fast, but is not to unstable in reacting to turbulence & gusts.
2. I NEVER advocate using unmatched ESC & motor combinations.... The respective manufacturers have tested the ESC & motor combinations.... using anything but what they recommend is just an "experiment".... with your time & money. This is especially true today with the very highly engineered motors that require tailored firmware to correctly react to timing & needed high current draw conditions when turning larger propellers...
I like the friendly debating of the forum, many have very strong feelings.... I try to stick to facts.... but I am human also...
Thanks!
Andrew
 

R

Rick James

Member
i have used both the U7 420 Kv motors with T80amp esc and the KDE 5215 435kv motors and 55amp kde esc(at the time that was the recommended esc). we have ran both 17" and 18" props on our t-motor setup and had great results. the rig AUW was around 33lbs with a movi and red. we ran 2 6s 10,000 mah packs and was giving us about 7-8 minutes of flight time and still having 25-30% left in the packs. the T-motor setup setup has been our go to rig and has worked for about 400 flights now.

we only tested the KDE 5215 motors and 55 amp esc's on a frame to see if it was something we wanted to switch over to. at the time the we were told the 55 amp esc's were enough but they were getting quite hot (around 160° with 50° ambient temperatures). we lost about 1.5-2 minutes of flight time with the same packs. 8 5215 kde motors were all together about 2lbs heavier then the U7 setup. i will say however they had quite a bit more power then the U7s with the same prop( we tested 16-18" props). running 16,000 mah batteries would have given us better flight time and it would have been able to handle the extra weight just fine. we ended up getting another set of U7s and have been running them on that same airframe ever since and have had no issues.

i wouldnt say i didnt like the KDE setup, i was more upset that the 55 amp esc's were supposed to be enough but they are really not. and now they only recommend the 75 amp esc's for the 5215 motors. we contacted KDE and they wouldnt swap ours out so we just stuck with the T-motor setup.

we also tested the 4215 380kv motors and found those to be a little closer in power and efficiency as the U7 420 kv motors. this was just bench testing with a thrust and watt meter. we never flew those motors with the same payload.
 






fltundra

fltundra

Member
Rick James said:
i wouldnt say i didnt like the KDE setup, i was more upset that the 55 amp esc's were supposed to be enough but they are really not. and now they only recommend the 75 amp esc's for the 5215 motors. we contacted KDE and they wouldnt swap ours out so we just stuck with the T-motor setup.

we also tested the 4215 380kv motors and found those to be a little closer in power and efficiency as the U7 420 kv motors. this was just bench testing with a thrust and watt meter. we never flew those motors with the same payload.
Click to expand...
The 95+ amp esc's are the safe route to go with the 5215 motors. I wouldn't fly the 75's with those.:)
 

Pumpkinguy

Pumpkinguy

Member
I think most of us will agree that tmotors posted specs are pretty much bang on. Good, honest engineering data that we can take and apply in the design of a new aircraft.

I question what advantage a company hopes to assume by stretching numbers. Fluffing up components to look more efficient or powerful on paper than they actually are. Or is it a case of different testing equipment?
Either way, if I am marketing a product, I want the specs to be on the modest side. Then the customer hooks em up and goes "Wow" rather than "wtf"
 

R

Rick James

Member
I had emailed back and forth with KDE asking about how they did their testing. they use a power supply that is always maintaining 25v. so no matter what load you put on the motor the powersupply will feed 25v. unfortuneatly our batteries do not do the same and usually drop a 1.5v or so just in a hover when you take off. a battery can't sustain the same voltages a power supply can, thats why there numbers are not a good refference for building a multirotor and why they seem inflated.
 
Last edited by a moderator:

fltundra

fltundra

Member
Rick James said:
I had emailed back and forth with KDE asking about how they did their testing. they use a power supply that is always maintaining 25v. so no matter what load you put on the motor the powersupply will feed 25v. unfortuneatly our batteries do not do the same and usually drop a 1.5v or so just in a hover when you take off. a battery can't sustain the same voltages a power supply can, thats why there numbers are not a good reference for building a multirotor and why they seem inflated.
Click to expand...

It can't be that hard to write a piece of software that would follow the average lipo discharge curve in controlling power supply output. That way you could have repeatable data for different sized lipos and loads. I have great ideas on how to solve the problem. Just don't write software.
 


Old Man

Old Man

Active Member
Bartman said:
@Pumpkinguy
what is that unit you're using to display amps/volts/watts?
Click to expand...

Another version, the original, is WattsUp volt and ammeter. Available at hobby shops and online. Good unit, reliable and accurate. I use one all the time and send it up in line with the power system to accurately record peak loads. Small and relatively light.
 

Old Man

Old Man

Active Member
Rick James said:
I had emailed back and forth with KDE asking about how they did their testing. they use a power supply that is always maintaining 25v. so no matter what load you put on the motor the powersupply will feed 25v. unfortuneatly our batteries do not do the same and usually drop a 1.5v or so just in a hover when you take off. a battery can't sustain the same voltages a power supply can, thats why there numbers are not a good refference for building a multirotor and why they seem inflated.
Click to expand...

T-Motor uses the same constant voltage methodology. When testing U-8's I had to take the discharging battery into account, but found the T-Motor specs to be reasonably accurate at the T-Motor referenced voltage.
 

violetwolf

violetwolf

Member
Putting my engineer's hat on for a second, I think using a power supply may be the lesser of two evils.. If using batteries for testing there would be differences between batteries depending on brand, age, temperature etc. At least with a power supply you could compare apples to apples.

But great discussion and food for thought when specing motors. Allow a little extra for Batt sag :)
 

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