TOPIC:

eddrick wrote:

It's easier & makes more sense if you have the bits in front of you than trying to make sense of the black & white stuff!

Definitely, I've had the same experience trying to read the manuals...

Another nice overview of Tamiya motor specs. Thanks waterbok.

Very interesting topic, but i dont think you can calculate the torque of the motor based on ampere and watts, cause it has to do with nr of turns and thickness, magnets, length of can, etc.

The given info about the good old standard 540 (can be found all over the internet) are probarly way wrong. "15080 rpm 5.9A 194 g-cm" match no motor from mabuchi, past or present. The closest match is the 5045 motor, which shares the same rpm and amp current,
(but first at 12v...) but torque is way off. www.mabuchi-mot.../12.0/12.0

second issue, the sport tuned motor! (no way near 350 g-cm) since i didnt noticed any differences in power when i upgraded my TXT-1 from stock 540-J to sport tuned i already knew that Tamiya overexaggerated the performance for their sport tuned motors but i could never believe it was THIS much!

250 g-cm is closer to the truth... not 350! translate.googl...NrNdxSloeA

Very interesting! And finally... a genuine curve :




I cannot see the first link though, it apparently needs some kind of (unknown) plugin...

hmmm, but heres a pic www.kraeuterbut...Bild3.jpeg

Thanks again, things are becoming clearer...
The 540 depicted looks like a well balanced motor with good efficiency - and indeed much torquier than expected.

Interesting graph - it shows why you need an ESC rated at a much higher amperage than the "official" figures claimed for a motor - a peak of around 60A vs 32A at max. power vs 3.2A lowest figure.

It also goes some way to explaining why a "faster" motor can be no quicker in the real world if you get the gearing wrong - overgear (too big a pinion) a "fast" motor & as the torque drops as revs go up, it gets "stuck" on the left hand side of the yellow line in the graph & never gets over the hump into higher revs.

Edou wrote:

Thanks again, thing are becoming clearer...
The 540 depicted looks like a well balanced motor with good efficiency - and indeed much torquier than expected.

Now i figured out how the "194 g-cm" came out... since the 5045 motor is 324 g-cm at 12 volts, someone only used simply math, like: 324 / 12 = 27. And then 27 x 7.2 = 194.4...

But according to the performance chart, the 540-5045 motor at 7.2v has 10500 rpm at no load (8700 at best eff) and 241 g-cm. But i highly doubt this motor has been used in RC cars, since it appear too slow(?) i think 27 turns motors always is used, and maybe 30 or 35 turns in the old days.

On the other hand, i dunno if we should trust those graphics i found too much since the claimed torque for the 540 round label motor seems a bit too high and weird imo. Because how can the same motor have a higher current draw and more torque at 6.8v than it has at 7.1? look this comparison www.rct.ne.jp/c...540-03.gif

Edou, graph shows there is more going on than the simple equations we started with, pretty much as I said. We see these types of graphs all the time at work for fans & pumps & they all relate to fixed test conditions & never truly reflect the performance of the equipment in the real world, as you can never anticipate what's actually going to be hooked up to the equipment. Pretty much the same thing with toy cars - these test ratings are all very well, but don't allow for the motor's owner not lubricating the bearings, running with dodgy batteries, having underrated wiring etc.
SID - same motor can have higher current draw & more torque at lower voltages depending on how the magnets are timed in relation to the rotor coils & commutator - if it's tuned for low rpm torque, excess voltage & current is wasted overcoming the magnet force when it tries to spin faster than optimum. Generally, more current means more rotor magnetism (Torque) & more voltage means more speed, but the 2 are directly related & will affect eachother