yet another new build - needing some guidance

S

si3po

Member
I've plugged some numbers into eCalc and got some interesting results.

I had to use 'Custom' battery and ESC so i could enter more accurate weights (eCalc says a 4000mAh 3S 25C/30C is just over 110g - i couldn't even find one under 250g online!). The details i used were for the Zippy Compact 3S 4000mAh which weighs in at 286g according to HK.

I found that with any 9" prop, my flight times for 'mixed fight' were under 7 minutes with the battery as having a "full charge". Upping to a 10" x 3.8"pitch prop got me closer to 10 minutes 'mixed flight' timings, with additional capacity for payload. I took a screenshot of the eCalc page and posted it below for my best example setup using the Zippy Compact 3s 4000mAh battery above - what do you think, could i improve that by dropping to a lower capacity, and therefore lighter, battery? :confused:

 
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Motopreserve

Motopreserve

Drone Enthusiast
Si,

The 110grams is for the single cell - eCalc will multiply that by however many cells you have (3S, 4S etc). Just plug in the info normally. Sometimes it errs on the side of caution with weight - but it's better and safer in the end.

Your throttle is up over 60% - try to mess around and get that down closer to 50%.

Also, I thought that I read on the HK site, in the comments section at the bottom of that frame page, that the weight of thr frame was 400grams??? Maybe I was wrong? If I wasn't, that difference will open up possibility for bigger battery and longer flight time.

Check out how I entered things here and then you can mess around from there...

 

S

si3po

Member
Motopreserve said:
Si,

The 110grams is for the single cell - eCalc will multiply that by however many cells you have (3S, 4S etc). Just plug in the info normally. Sometimes it errs on the side of caution with weight - but it's better and safer in the end.
Click to expand...
ahh, i see. that makes sense! i'll switch back to just using the frame weight then and plug a few more numbers...

Motopreserve said:
Si,
Your throttle is up over 60% - try to mess around and get that down closer to 50%.

Also, I thought that I read on the HK site, in the comments section at the bottom of that frame page, that the weight of thr frame was 400grams??? Maybe I was wrong? If I wasn't, that difference will open up possibility for bigger battery and longer flight time.

Check out how I entered things here and then you can mess around from there...
Click to expand...

regards the weight, you're right. i had a read in the comments on the product and, indeed, most say it is closer to 400g than 500g so i'll use that.

i'm still playing with prop diameter/pitch combinations versus a larger mah battery at 25/30C to see what i get. So far, the 9x4.7 with a 4000mah battery and frame weight set to 400g gives a mixed flight time of ~6.7min. Keeping in mind that eCalc is probably over-compensating the battery weight, i'm reckoning the mixed flight times would be closer to 8mins with this set up.... what are your thoughts, am i nearly there regards set up?

also, i'm struggling to find a UK supplier of 'decent' CW and CCW props in every size. I'd like to get the APC SFs as an absolute minimum since these seem to provide more lift for their size, and if i can source them multirotor specific prop sets, but i'm still looking for them in the UK.
 

Motopreserve

Motopreserve

Drone Enthusiast
Looks like you're getting close. The way I worked it was I just kept messing with the numbers in eCalc until it seemed decent. The closer you can get to 1o minutes the better, while keeping throttle around 50%.

Cant help ell you with the UK dealers. But I'm sure there is a list on this forum somewhere will a bunch of the bigger, better stocked shops.
 

S

si3po

Member
Motopreserve said:
Looks like you're getting close. The way I worked it was I just kept messing with the numbers in eCalc until it seemed decent. The closer you can get to 1o minutes the better, while keeping throttle around 50%.

Cant help ell you with the UK dealers. But I'm sure there is a list on this forum somewhere will a bunch of the bigger, better stocked shops.
Click to expand...

thanks moto, i did try with a 4S 4000mAh lipo, but the motor max. power draw went beyond its limits at over 335W so i assume i'll need to stick with the 3S as initially spec'd....just out of curiosity, what would the outcome of using the 4S battery be on the motor if i did use one?

I've spoken to a few UK suppliers and they've agreed to try and source the props but offered no promises on when they could expect stock, if at all, but at least they're looking. Until then, i'll be looking at getting a set of the APC SF 9x4.47 props as well as spares for this set up.
 

Motopreserve

Motopreserve

Drone Enthusiast
si3po said:
thanks moto, i did try with a 4S 4000mAh lipo, but the motor max. power draw went beyond its limits at over 335W so i assume i'll need to stick with the 3S as initially spec'd....just out of curiosity, what would the outcome of using the 4S battery be on the motor if i did use one?
Click to expand...

Without being completely specific to this setup - ohms law would provide for approximately double the watts being produced (11.1v increased to 14.8v) - which would be flowing to the motor. Something to note would be that as I understand it (which may be very little!), it's not so much the power DRAW as much as it is the amount of juice you are sending TO the motor - which in this case went over the motor's limited capacity. If too much wattage goes to the motor - the motor can burn up.

Of course, eCalc is looking at it for bursts, as well as normal operating ranges (less than full throttle for most circumstances). So it tries to calculate it on the safe side - and kicks back an error if it has the potential to go over the limit. That is to say that if you were to run a motor at too high a wattage, but never went above a certain threshold, you would probably be OK. But it's the what if scenario that would get expensive real quick :)
 

SoCal Blur

SoCal Blur

Member
The issue going with a 4S as opposed to a 3S in your case is the voltage increase. Think of voltage as water pressure. the higher the voltage, the more pressure. Motors are designed to be able to handle a certain amount of that pressure. If you have too much pressure, you will destroy the motor.

Current (mah) on the other hand can be thought of as the supply of water. Motors will only draw as much as they need. As the RPM of the motor increases, so will it's draw of the available supply. The more supply (Current/mah) you have, the longer the motor can run. So the key is not to exceed the pressure max of the motor (voltage) but to have as much supply (current/mah) as you reasonably can.
 

Motopreserve

Motopreserve

Drone Enthusiast
SoCal Blur said:
The issue going with a 4S as opposed to a 3S in your case is the voltage increase. Think of voltage as water pressure. the higher the voltage, the more pressure. Motors are designed to be able to handle a certain amount of that pressure. If you have too much pressure, you will destroy the motor.

Current (mah) on the other hand can be thought of as the supply of water. Motors will only draw as much as they need. As the RPM of the motor increases, so will it's draw of the available supply. The more supply (Current/mah) you have, the longer the motor can run. So the key is not to exceed the pressure max of the motor (voltage) but to have as much supply (current/mah) as you reasonably can.
Click to expand...

Well put. :)
 

S

si3po

Member
SoCal Blur said:
The issue going with a 4S as opposed to a 3S in your case is the voltage increase. Think of voltage as water pressure. the higher the voltage, the more pressure. Motors are designed to be able to handle a certain amount of that pressure. If you have too much pressure, you will destroy the motor.

Current (mah) on the other hand can be thought of as the supply of water. Motors will only draw as much as they need. As the RPM of the motor increases, so will it's draw of the available supply. The more supply (Current/mah) you have, the longer the motor can run. So the key is not to exceed the pressure max of the motor (voltage) but to have as much supply (current/mah) as you reasonably can.
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SoCal, this makes perfect sense and positively clears up my curiosity - Thanks!! :encouragement:

Basically, then, i should stick with 3S and see if i can up the battery capacity to extend flight times...i'll see what the budget allows, but currently looking at the Turnigy Nano-tech 4000mah 3S 25C.

I'm also considering swapping to the HK F-20A ESCs. They allow a burst of 25A, so above the D2830-11 motor's max current draw of 21A. I'll reflash them to SimonK soon as i get them to ensure i get the very best out of their potential, but will dropping to these over the F-30A's negatively affect the over-all set up?

p.s. as you may gather, my electric flight knowledge is rather limited thanks to me only flying nitro fixed wing a/c and rtf micro helis and quads up till now, so please excuse my ignorance if i'm asking basic questions.
 
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Motopreserve

Motopreserve

Drone Enthusiast
The other thing to think about is possibly getting a lighter frame. Inexpensive options are out there like the DJI which weighs in at 282 grams. I have found that my HK frame (x650f) is far heavier than it needs to be. That obviously effects flight times as well.
 

SoCal Blur

SoCal Blur

Member
si3po said:
SoCal, this makes perfect sense and positively clears up my curiosity - Thanks!! :encouragement:

Basically, then, i should stick with 3S and see if i can up the battery capacity to extend flight times...i'll see what the budget allows, but currently looking at the Turnigy Nano-tech 4000mah 3S 25C.

I'm also considering swapping to the HK F-20A ESCs. They allow a burst of 25A, so above the D2830-11 motor's max current draw of 21A. I'll reflash them to SimonK soon as i get them to ensure i get the very best out of their potential, but will dropping to these over the F-30A's negatively affect the over-all set up?

p.s. as you may gather, my electric flight knowledge is rather limited thanks to me only flying nitro fixed wing a/c and rtf micro helis and quads up till now, so please excuse my ignorance if i'm asking basic questions.
Click to expand...

Personally, I would not change to 20A ESCs. I prefer to have some "headroom" when it comes to current rating. There is an ongoing debate about how ESCs work. One camp says that The ESC will use all of the current it is rated for continually, bleading off unused current as heat when the throttle is less than 100%. The other camp says that ESCs only uses what the motor draws through them so that the primary concern is making sure that the Current rating isn't too low for the load the motor will put on it. I have not done any direct testing to verify one theory over the other but I personally am in camp #2- I use 60A ESCs even though my current motors max out at around 17amps at full throttle. I've changed from 60A to 40A in eCalc and it didn't make a bit of difference as far as flight time for my configuration.

I would rather have the piece of mind that I won't be burning up a ESC because i'm working it too hard and have a few seconds less flying time than getting the Current rating on the ESC as low as possible and risk a failure and possible crash.
 

Motopreserve

Motopreserve

Drone Enthusiast
I actually fall into a 3rd camp. I try to ensure headroom without going too unnecessarily high. My suggestion for 20A ESC was when I was swapping a bunch of components - and unfortunately can't even remember what I had plugged in at the time. The more recent data included only 30A ESCs.
 

S

si3po

Member
Motopreserve said:
I actually fall into a 3rd camp. I try to ensure headroom without going too unnecessarily high. My suggestion for 20A ESC was when I was swapping a bunch of components - and unfortunately can't even remember what I had plugged in at the time. The more recent data included only 30A ESCs.
Click to expand...

well, i'm now wondering of sitting in the middle and using the Turnigy PLUSH 25A ESCs might be better? Are the PLUSH ESCs raterd better than the HK F-30s?
 

Motopreserve

Motopreserve

Drone Enthusiast
I think the newer Plush might not be able to be flashed at this point??? I could be wrong. I have the F-30A and flashed them myself. I've been reading up on the ESC situation - and even most experts agree there is very little difference (if at all) between the manufacturers.

Some people go for more pricey ones simply because they trust that it may be better QC. But no one seems totally sure about it.
 


Motopreserve

Motopreserve

Drone Enthusiast
I would imagine that's about the same as the DJI (direct knock-off). But I'm not sure if the parts are interchangeable - making the extra $15 for the actual DJI worth it - since you can get replacement arms/parts anywhere, without dealing with the 'slow boat from china' dance.
 

S

si3po

Member
Motopreserve said:
I would imagine that's about the same as the DJI (direct knock-off). But I'm not sure if the parts are interchangeable - making the extra $15 for the actual DJI worth it - since you can get replacement arms/parts anywhere, without dealing with the 'slow boat from china' dance.
Click to expand...

I figured it was a copy of the DJI since they look so similar. Looking at the reviews for it, most seem to say it's a solid unit, and the inbuilt power distribution pcb means no extra weight. There seems to be a good number of spares for the Q450 so I may be tempted to use it and run the gauntlet....
 
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