Lehner Power Ratings Help

[What's_nitro?]

So what's up with Lehner rating their motors at the same power at the same amperage for all of the winds in a series? Like this:

1940/6 - 1400W @ 50A
1940/7 - 1400W @ 50A
1940/8 - 1400W @ 50A

And so on down the line. It would seem like this contradicts the properties of electricity. You need more voltage to put the same amperage through a higher impedance. And thus with a constant amperage there would be an increase in power output as the impedance increased. I want to upgrade my Rustler to a 1940, but, I really don't want to have to cram an 8s LiPo in there too! Not to mention a controller that can handle the voltage. Help?

[BrianG]

Maybe the power rating is how much the motor can dissipate and the current is the continuous amperage of the wires themselves?

Or maybe someone simply got carried away with the cut-n-paste feature. :)

You're right though, if those figures mean what they say, each motor has a resistance of 0.56ohms. To get 50A and 1400w, you'd need 28v...

[What's_nitro?]

I think your right about the cut-and-paste thing. I've been reading lots of posts on this forum about people running 1940/50 series motors at 5s or 6s and I'm thinking to myself: "They can't be getting full power from that motor! Can they?".

[zeropointbug]

You're right, we usually aren't getting the full power from these motors.

Each motor version (# turns) in a series, such as 1950 has the same peak power that is able to be extracted from them. It's just a matter of what configuration you want to run, higher voltage/lower amperage requirements, or lower voltage/higher amperage requirements. However, the higher voltage/higher turn setups USUALLY can extract a little more power than vise-a-versa, because of higher resistance losses, and hence more efficient.

One thing I notice with the Lehner motors is that the lower turn motors have great efficiency at higher torque's. Whereas, the higher turn motors have great efficiency at lower torque's, and slightly less efficiency than lower turn motors at higher torque's (a couple % points); BUT, overall the rpm range, they have a better average efficiency. It kinda depends on the application really. :030:

[squeeforever]

Keep in mind, the motor can only produce as much power as the batteries can handle. 1400 watts isn't possible without batteries that can deliver it. Thats not something most batteries can do. Besides, with good enough batteries, you can get over 1400 watts out of the motors, even though they may only be rated for 1400. Make sense? Just keep in mind that its only a rating, or guideline.

Keep in mind that most of this stuff is over my head, but I read someplace that the amp draw ratings of a motor are supposed to be the maximum constant draw of the motor when you apply the maximum voltage to the motor. The maximum voltage is the highest voltage that you can apply without exceeding the maximum rpms. The wattage rating of the motor, from what I understand, is what the motor is capable of producing with a capable power supply.

[What's_nitro?]

Well you can get a minimum of 50A from a 20/25C 2480mAh LiPo. So That shouldn't be an issue unless you are poor and would rather eat dinner than buy new batteries. And I'm sure you could put tons more power into them if you wanted but I'd rather not blow a $300 motor.

[Gustav]

I always figured the wattage ratings are just a very rough guidline to help you choose a motor from the range,not a measured specification in any way.the lehner motors can pull an awful lot more peak power than those figures anyway.

[What's_nitro?]

Yeah I figured it was a constant power rating, but it's that constant amperage rating that is confusing to me. I want to get the maximum power from the motor, so if necessary I will cram 8s' worth of LiPo into my Rustler.

[Gustav]

Yeah,i see what you mean,i don't know where the @ 50A comes from,where does it say that?

btw,you don't want 8s lipos in a rustler,with a stadium truck and brushless,power is simply not a limiting factor regarding speed,eg you will have issues to work out with just a 1930/8 on 4s,like keeping it in one piece and on the ground,aerodynamically a stadium truck is already an aeroplane at those speeds.

[What's_nitro?]

Well I have a Novak HV 6.5 in it now on 4s LiPo and I would say it does an easy 40 MpH with 19/87 gears, maybe 45. And with 1" of ground clearance I have no problem with control. I mean it doesn't flip over it just spins out repeatedly if I corner to hard. How much power would you actually get from that 1930/8 on 4s? The HV puts out 400W already. I got the motor information off of the Fine Design page. Yep I said the "F" word.

[Gustav]

Originally Posted by What's_nitro?

How much power would you actually get from that 1930/8 on 4s?

Tons,trust me.more than a rustler that you could still call a rustler can use.With smaller systems than that,the power available is already not a limiting factor in any way with regards to speed or acceleration.you need wings front and back and you need to be prepared to break it alot when you venture that far above 60mph with a lightweight stadium truck,they produce a lot of lift.60mph already looks quite quick with one but is pretty easy to achieve.I use a 1920/10 on 4s in a xxxt sometimes and that will hit over 60mph,drop in a 1930/8 in the same truck and you start to wish it had less torque.
This thread is very worth checking out if you haven't already,http://www.rc-monster.com/forum/showthread.php?t=6165,impressive stuff for a little buggy that's meant to go 20mph round an offroad track.

[What's_nitro?]

Did I mention it's primarily aluminum, I have an RCM-RC chassis, and I turned the transmission around? It weighs almost 8 pounds with everything. I need new pictures...

[Gustav]

Is that chassis longer than stock?that would help a lot too if you're looking to hit some big numbers.

[Serum]

The lower the KV, the less current a motor can handle (since it's made for higher voltages and has got a higher internal resistance)

the motors with different KV's from the same serie take different currents. (lower KV, higher current) their 40A rating is simple rubbish.