Understanding motors

[matelot]

.
A bare-bones 450 FBL kit (Tarot) is an option for my first build, but at the moment I'm a little stuck in understanding motors. Generally the 450 size seem to run on 11.1v 3S Lipos, so the motors will be designed with that voltage range in mind. I get that.

But, how does one know what current draw to expect, or will use in order to establish the battery amp size and ideal flight times? Chicken or egg.

Are 450 motors generally going to fit 450 airframes (thinking of Align and their clones)? Although some look very short in overall length.

What about shaft length and diameter where there is a choice? Seldom reference is made to a pinion, so don't know if one gets supplied or not. Pointless buying a motor to find it doesn't fit the frame...

Do 450 drive gears conform to any sort of industry standard/agreement so that pinions will mesh correctly? There are helical-cut gears out there as well for 450 clones.

Of course I could get a bare-bones kit with motor and Esc: that tells me the what, but not the why.

Any help to aid my understanding would be much appreciated.

Cheers

[tombo242]

Your power drawn will vary quite considerably with the style of use. For a 450 in 3D flight flash currents of 50A are quite possible, in gentle cruise the load may drop to around 20A. Expect a 2200mHa 20C to give around 6min gentle flight.

The motor fixing holes are usually a standard distance apart, I've never known a problem there, but I have sometimes found a very slight variation in the usual M3 fixing screws. (The replacement motor in my EXI 450 had M2.5 threads - I tapped them out to M3, no bolts supplied.) Make sure your motor comes with them.

Shaft size is likely to be either 3mm or 3.15~3.2mm diameter. Again make sure that you get the right gear, you might be able to drill out a smaller one but a loose fit on the shaft is asking for trouble.

Make sure that the length of the motor shaft is sufficient for the gear to mesh with the main drive. The teeth on the straight-cut gears all seem to mesh OK. I can't say about any other style.

In general I would say, get the kit first and then you can check the measurements to ensure a good fit.

Tom.

[tombo242]

On the battery choice, I've written a windows calculator for batteries. Does a variety of things and saves trying to remember all of the formulae.

If you can run windows (installs and works on my 64 & 32 bit systems) it's here for download and testing. Love to hear how you get on folks!

Tom.

[matelot]

Just downloaded it, made a directory, unpacked it and ran it under Wine in SolusOS (Linux).

Perfect first time.

The only woolly variable at my end is knowing with any particular chopper the average amp draw over the flight. But that will come when I start measuring flight times and what gets pumped back in to the battery etc.

Good and highly recommended little prog.

Cheers

[tombo242]

Thanks for testing and the positive report.

Tom.

[Raza01]

Think I'll stick to total discharge and scrapping. (Even if I could see the 'enjoy' part of the post.) I keep my rifle for rats! Mad


____________________
USMAN