Another MN4014 v MT3515 ... please help

C

cbuk

Member
Hi guys


I think I've messed up with my calculations and am I'm hoping to get some advise on motor and prop selection (or maybe I should say reselection) for a skyjib X4 build.


The AUW will be between 8.5 and 10kg (depending on camera), running of 6S cells (currently 2 x 6000 mAh) with 40A optos.


I'm currently testing the bird with 15 x 4.5 torqpower beech propllers and MN4014-11 motors. It's stable and hovers well, but eCalc confirms its massively underpowered with this motors/prop combination. Even at the lower end of AUW, eCalc is indicating I need 80% throttle for hover...so no chance of lifting the heavier AUW with those propellers.


So do I beef up the propellers or change to the MT3515-15's which on the basis of ecalc may be better suited to my needs?


Can I stick 16” props onto a skyjib X4? Droidworx website suggests “suited for fitting up to 15 propellers”

Some eCalc results below; (for each AUW: first row is how it is now...not good!, Second row is option if I can fit 16" props on the SJ X4 and third row is 3515 route)



At the lower AUW:


MN4014-11's + 15” x 4.5” : Hover---> 81% throttle, 76.4% efficiency, flight time 8.6 min
MN4014-11's + 16” x 7” : Hover ---> 56% throttle, 75.4% efficiency, flight time 9.1 min
MT3515-15's + 15” x 4.5”: Hover ---> 60% throttle, 90.8% efficiency, flight time 9.7 min


At the higher AUW


MN4014-11's + 15” x 4.5”: Hover ---> 91% throttle, 79.8% efficiency, flight time 7.0 mins
MN4014-11's + 16” x 7”: Hover ---> 65% throttle, 79% efficiency, flight time 7.4 mins
MT3515-15's + 15” x 4.5”: Hover ---> 72% throttle, 90.8% efficiency, flight time 7.6 min


I suspect that I would be better of sticking with 15” props which pushes me in the direction of buying a new set of MT3515-15's.



I hope this post isnt too confusing and that I've explained myself as clearly as possible.


Any suggestions/alternatives?



Thanks
Chris
 



C

cbuk

Member
KaspInc said:
My MN 4014-11's get quite hot fairly quickly in the summer more than my MT 3515's or 3520's.
Click to expand...

Thanks for the reply; like Efliernz asks...what size props/craft setup are you using and what is the AUW when using the 4014-11's?
I notice from your sig you carry a Nikon D800E (which is the set up I'll be using for the higher AUW example I showed above); do you carry this on your skyjib with 4914-11's or 3515's.
 

dazzab

dazzab

Member
Hmm, I have the same copter with MN4014-11 motors, 15x6 props and 2x 8A 6S batteries. It lifts a Nikon D600 full frame DSLR with no problems at all with around 55% hover. The motors don't seem to get that warm at all but I haven't done a lot of flying yet and it's not summer here yet. I think you need to have another go with E-Calc as your results don't sound right to me.
 

C

cbuk

Member
dazzab said:
Hmm, I have the same copter with MN4014-11 motors, 15x6 props and 2x 8A 6S batteries. It lifts a Nikon D600 full frame DSLR with no problems at all with around 55% hover. The motors don't seem to get that warm at all but I haven't done a lot of flying yet and it's not summer here yet. I think you need to have another go with E-Calc as your results don't sound right to me.
Click to expand...

Dazza, thanks for your input.
When you say 55% hover do you mean calculated in eCalc or physical stick input on the radio (which I guess is controlled by the FC). When I put in an AUW of 9000g (which I'm guessing is close to your weight with 2 x 8000 mah and the D600) and 15 x 6 props, ecalc suggests 75% trottle to hover. I think I'm probably making a mistake somewhere. What weight and propeller properties are you using in eCalc?
 

dazzab

dazzab

Member
cbuk said:
Dazza, thanks for your input.
When you say 55% hover do you mean calculated in eCalc or physical stick input on the radio (which I guess is controlled by the FC). When I put in an AUW of 9000g (which I'm guessing is close to your weight with 2 x 8000 mah and the D600) and 15 x 6 props, ecalc suggests 75% trottle to hover. I think I'm probably making a mistake somewhere. What weight and propeller properties are you using in eCalc?
Click to expand...

When I say 55% I'm talking about actual flying. And it has plenty of spare thrust as well. My AUW is about 8.5Kg. I think you might actually be giving eCalc figures for four motors rather than eight. My SkyJib X-4 is a coax so it has eight motors.
 



C

cbuk

Member
maxwelltub said:
I think if you move to a bigger pitch it will make a huge difference. Look at 15x5.
Click to expand...

I ended up fitting 16 x 6's and its made a big difference. eCalc predicts a hover throttle of about 48% for my unlaidened craft at 6.7kg and sure enough if I switch into manual mode from atti when hovering, the bird slowly rises. I'm now fairly confident in eCalcs prediction that to lift my average and maximum AUW of 8.5 and 10kg I will need between 60 and 70% throttle.
 

J

jhardway

Member
my only thing that I can throw in there is that the bearing set on the MT series are not as good as the set on the MN series, my experiences in the past with the 3515 motors was that I found the bearing not as solid as I would like, since I have change over my motors I have replaced the bearing set but have not been able to fly them yet.
 

Q

Quinton

Active Member
I just set up a watt meter and a thrust meter to check out which propellers were more efficient on my T-Motors 3515-15
I need to get it all strrapped down first though as it wasn't very safe in the kitchen :)

How would be the best way to record the data, for measurement.
I only had the controller on a Servo/ESC tester, so I didnt know what 50 or 75% etc was, but already I can see some interesting results.

I just put the thrust up to 500g as a quick test as I was hand holding, and the 15x5 Wooden Xoars measured 55W and 2.2 A
Then I put on the Tiger props 15x5 and at the same thrust it gave a reading of 43W 1.72A

So what would be the best way to record the data on a spreadsheet to compare to other motor/prop comparisons?
Im surprised people haven't got together before to have this data already there, will be interesting though, if I can get the stats layed out properly.
Any ideas on the best format?
 

S

Scott Drysdale

Mixmaster
If your existing components can produce a "csv" file.... then MS Excel can be used to import "csv" data directly...... from that tabulated data it is a simple process to produce graphs and charts. If your system cannot store data of any kind, it is time to get out a pencil and paper to write it all down then type it into MS Excel.
 

You must log in or register to reply here.
Top