500 size quad motor help

[AaronB]

Hi please let me know if this is in the wrong place👍🏻

im building a 500 sized quad and just need some help with what motors i can use, i have been looking at the Multistar Elite 4006 740kv to spin 11" props,30a afro simon k ESC's and running a 4S setup with an estimated weight of 2kg.
Hoping to get 10-15 min flight times.
link for motors Multistar Elite 4006-740KV Multi-Rotor Motor

any advice or help welcome.

[GIXERMAN]

bump to ttt

[Ruston]

You could try using the multi-rotor calculator on ecalc (eCalc - the most reliable RC Calculator on the Web) to work out the performance which includes estimated flight times baseb on your motor, battery and esc combination. The free version only provides a random selection of motors so you'll probably need to subscribe for a few dollars to get the full version with your particular motor choice.

[Toolman]

Hi Aaron,

It looks like your setup is perfectly sensible,
looking at the motor data on the HK website (assuming its correct) the current draw at hover power 500g thrust (on 11" props & 4s Lipo) is around 3.3A.
If you weight is 2kg, 500g is 1/4 of the weight.

so 3.3A * 4 = 13.2A current draw in a hover.
So for Lipo size to get 15 mins, you would need around a 4500mAh allowing for 20% capacity remaining.

That would be fairly heavy & may put up your AUW above 2kg though.
A 2200mAh pack would give around 7.5 mins, for comparison. You could try a pack size somewhere between the two.

Tim.

[AaronB]

Big thanks Tim!!!

would i be right in thinking if i went up to a 12" prop the added thrust would make up for the bigger battery? Thus allowing a tad longer flight times?
Anywhere near the 10 minute mark is good for me,just buy a handful of batteries to kkep me going!

[Toolman]

Hi Aaron,

The motor data on the HK page requires some interpretation here,
It shows data for a 12x4M.S.W. prop, I am not sure what that is.
I am guessing that it is Multi Star Wood, which would have different chracteristics to the more common slowfly or multi rotor props.

The Current draw actually goes up slightly but when you look at the data for the 13" prop it seems to follow the sort of trend you would expect to see.

As you increase the dia you get an increase in max thrust & current draw but also the increased efficiency gives you lower current for a given thrust value.

So I would expect the 12" prop to give you slightly less than the 3.3A at 500g thrust, but the value for a 13" prop is only down to 3A so the different isn't going to be huge.
somewhere between the 2. This isn't on the face of it going to make a huge difference.

There is another factor though with multi rotors in that running a smaller prop faster can give you better gust performance & allow the motor/flight controller to correct faster.

I think I would stick with the 11" if you can keep the weight to around 2kg.
It might be interesting to try 12" props sometime though to see whether you like the difference & if you notice any increase in flight time.

Tim.