About 540 motor

[mechplas]

Joe: For testing purpose on the bench, I tried to hook up my 540 with a GWS prop 5030 and 1250 3Slipo. the measured RPM was 20,000+ and the current draw was 7.5 amps. I am not sure how to relate this results for the next project. And what is the weight of the plane that the 540 can carry?


For All those "who have been there done that" please share:

I have intentions of doing a twin. What ESC is required and I am planning on getting the 3000mAh NiMh as power supply although the sketch shows lipo and should it be 9.6 or 12V?. I have sketched the schematic. Let me know if there is a short circuit in it... Also what prop should be used or what read outs should I expect.

Thank you.

[joe yap]

For 540 motor direct drive, 5x3 is too small, even for a speed400. For 540 motor, 3S lipo voltage is too high and you may want to stay at around 7-8 cells. For racing 'hot' 540, you should be using only 6-7 cells. Usual prop size should be 6x6, 7x5 or 8x4. It's simple, for every 1" increase in prop diameter, you drop 1" for pitch. Or to make it easier, just add the 2 values ,eg 6x6 prop add 6 to 6 and you get 12. So whatever prop you use, the diameter and pitch should ad up to 12.

For comparison, see the following data on the GWMP Kwik-E which uses a direct drive 'hot' buggy 540 motor :

Wingspan : 40"
Wing area : 278sqin
Weight : 32oz
Motor : Kyosho Endoplasma
Battery : 6 cell 3000mah nimh or CP1700
Prop : 6x6
ESC : 50amp

For less hotter 540s, use higher cell counts and lower current draw. 30amp ESC minimum

[joe yap]

For direct drive motor, the airframe needs to be relatively 'clean'. This is what the Kwik-E looks like.

[mechplas]

Thanks Joe.

Forgot to post the sketch of the twin setup. Is the 30 or 50 Amp ESC sufficient if I use say 6 cells on this setup?

[joe yap]

Oops, Sorry. I missed the your intension for twins. If each motor draws less than 25 amps continuos, 50 amps will be good. Check the current draw again before decideing your ESC. You circuit looks good. The other way is to use 2 motors with 1 ESC each and Y-harness them to your RX and battery. However, some ESC, like the SHS ones does not work with Y-harness. Kontronik ones are okay. Good Luck!

[joe yap]

Check your Lipo current draw capabilties as well!

[mechplas]

I can't find the right pic. What you are see in this picture is a trike but w delta wing. I am planning to do a straight wing with tension cables and alum tubes., and the twin motors tractor instead of pusher.

[mechplas]

[joe yap]

Sounds good. Good luck!

[AstroBoy]

Mechplas,

I wonder if this is what you're looking for, it's a 3-axis microlight, can find it on www.airliners.net

[joe yap]

For this kind of draggy design, your best bet is on geared 540 motor driving a large,broad high pitch prop. Most gearbox comes in reduction ratio of 2.5-3.5:1, which means your max prop RPM unloaded is in the region of 5000-7000. With such low RPM, you need deeper pitch to compensate for your prop velocity, and lower RPM allows you to use broader blades which has better efficiencies. Master Airscrew electric prop are designed this way and since there are less stress on the prop driven at lower RPM, this thin down the blades and even undercamber the lower surface to increase thrust even further. Don't be too worry that the static RPM is lower than your favourite APC electric, since you won't be doing motor ground run for too long. You'll quickly find that the static thrust is very powerful and your prop will unload in flight.

By the way, if you choose to use Lipo cells, use either 'hot' racing motor on 2 cells ( 7.4V), or very cool motor (=> 8.4V rated) on 3 cells(11.4V). Unless you can find some Lipo with voltage in between 7.4V and 11.4V, stick to conventional cells for your regular 540s.

[Jcho]

For direct drive motor, the airframe needs to be relatively 'clean'. This is what the Kwik-E looks like.

Hi Joe,

cool plane, can you share where you brought it from? Saw you flying another plane similar.

Cheers

[mechplas]

Mechplas,

I wonder if this is what you're looking for, it's a 3-axis microlight, can find it on www.airliners.net

OMG....that is fun looking man! Buay tahan liao... Can you quickly draw a building plan on Autocad...thanks man...

[mechplas]

For this kind of draggy design, your best bet is on geared 540 motor driving a large,broad high pitch prop. Most gearbox comes in reduction ratio of 2.5-3.5:1, which means your max prop RPM unloaded is in the region of 5000-7000. With such low RPM, you need deeper pitch to compensate for your prop velocity, and lower RPM allows you to use broader blades which has better efficiencies. Master Airscrew electric prop are designed this way and since there are less stress on the prop driven at lower RPM, this thin down the blades and even undercamber the lower surface to increase thrust even further. Don't be too worry that the static RPM is lower than your favourite APC electric, since you won't be doing motor ground run for too long. You'll quickly find that the static thrust is very powerful and your prop will unload in flight.

By the way, if you choose to use Lipo cells, use either 'hot' racing motor on 2 cells ( 7.4V), or very cool motor (=> 8.4V rated) on 3 cells(11.4V). Unless you can find some Lipo with voltage in between 7.4V and 11.4V, stick to conventional cells for your regular 540s.

Thanks for all the info man! I might take two or three days to digest these before rolling the project on.

[mechplas]

Mechplas,

I wonder if this is what you're looking for, it's a 3-axis microlight, can find it on www.airliners.net

U also found a picture with the moon!!! So Punggolian

I love it. This is very close to what I want. Can it be redesigned to be a tractor instead of pusher?