Motor anyone?

[Hickoryhead]

I am building a E-Revo. I need a motor. I will be running a Mamba Max ESC with 6000 mah 3s Lipo's. Which motor would be the best? I am new to this sport so please keep it simple for me to understand. Thanks.

I would strongly suggest going to at least 4S lipo for a truck the size of a Revo. For inexpensive motors, you could go with either the Feigao 8XL or 9XL. For a better motor, you could go with either the Lehner 1940/8 or 1940/9.

I would advise against running the 3S packs. Any motor that will deliver any sort of acceptable performance on 3S is going to draw way too much current and things will get hot.

[GorillaMaxx360]

too hot

[Hickoryhead]

Can you all explain more? I am new. Keep it simple for me. I am not stupid but new to all this.

[BrianG]

To move any vehicle, you need power. The heavier the vehicle or the faster/more powerful performance you want, the more power you need. Power is volts times current. Let's say you need a maximum of 1500 watts to get the performance you want for the revo. At 11.1v (3s) that would be 135 amps. However, if you increase the voltage to 4s (14.4v), you need 104 amps.

There is a bit more to it than that, like selecting the right motor and gearing, but you get the idea.

[Hickoryhead]

Ok I have got the answer I wanted about the motor. The Lehner 1940 is it. Whats the difference between the 1940\8 or 1940\9?

[BrianG]

The 8 or 9 is the number of turns.

Once you decide the voltage you want to run (the higher the better up to the limit of your ESC if possible and finances allow), you figure out the motor kv by taking 35000 and dividing by your desired voltage. The answer is the kv of the motor you need. Pick something as close as possible. The 35000 number is the maximum rpm you want to run your motor at for best efficiency.

So, for 4s, you'd need a motor with a kv of around 2400. A 1940/7 or 1940/8would work well.

Brian is a bit of a speed nut. I like to keep things on the conservative side. I like running motors a bit milder and keep the rpms at about 30,000. Still lots of power, but easier on the batteries and everything else too.

[BrianG]

ok, for the "slower folks", use 30,000 instead. :)

[miniGranis]

A possible thread hijack but I'll have a go.
I am still not sure if I should go for a 8 or 9 XL for my upcomming E-Revo.
Would a 9XL run cooler then a 8XL if geared for the same speed, say around 40mph ?
Would it be wiser to run a sensible geared 8XL (with trottle EPA turned down, ie no full trottle) and would that run cooler then an 9XL with "full throttle enabled" ?

I will be running 2x 2s2p 8000mAh LiPo and long runtime (30-40 minutes) normal bashing style without too much heat issues is what I am looking for.

Brian, I'm not sure of how to take that. LOL

mini, if you gear the 9XL for the same speed as the 8XL, it's going to pull just as much current and will likely still get hot. Personally, I like the 9XL. You get more of a practical gearing range, IMO.

As for the runtime, that doesn't just depend on the batteries. Depending on your driving style and climate, you may very well be having to take a break so that the motor can cool long before the batts go dead.

Also, turning the epa down on the throttle might not be a good idea, again depending on your setup. If you have to turn it down to 50%, the esc might over heat. The esc runs at its greatest efficiency when at full throttle. If you never hit full throttle, it will never see this. It's usually best to setup and gear so that you will be hitting full throttle at least some of the time.

[BrianG]

Originally Posted by AAngel

Brian, I'm not sure of how to take that. LOL

No offense - I didn't mean anything by that. What I meant was "ok, for the folks who like slower motors...". :)

A little off topic but related: I get a kick out of those street signs that say "Slow Children". Your post reminded me of that. :)

[rschoi_75]

what pinion sizes are you guys using?

I'm all set on the motor (fegaio 9xl), but now I need some pinion advice. I plan to buy two or three of them, so what range would be good for a stock e-maxx spur. I'm using an e-maxx tranny in my revo...

[miniGranis]

Thanks AAngel, I keep hoping that someone can tell me use this and that and your are all set and wont have any problems... now it's just chocies choices... I guess I am in the wrong hobbie .
Thanks again for helping out, I will go for a 9XL geared for about 40 mph.

[gasshead]

man you cant say that rc is the wrong hobby. i am only haveing problems with desesions for batteries. for now i beleve i will use 2 B&T blister packs and every now and then 14 2400 cadiums