https://www.evwest.com/catalog/index.php?cPath=8&sort=2a&page=2I guess i asked the wrong question. What kg/kw ratio is realistic for current motors?
I don't think so. The two DC motors you have rated by HP and weight.https://www.evwest.com/catalog/index.php?cPath=8&sort=2a&page=2
Warp 9: 32 HP and 65kg = 0.0027 kg/kw
Warp 11: 44hp and 106kg = 0.0032 kg/kw
Roughly, ballpark, any DC motor's going to be in that range.
Tesla Model S: 400kw and 295 lbs = 0.00034 kg/kw
That's an AC motor, but it includes the controller and gearbox, and if you missed it, it's 1/10th the kg/kw as the DC motors above.
"HP" means horsepower, which is simply a unit of power... and power is power.I don't think so. The two DC motors you have rated by HP and weight.
The AC motor is rated by power and weight.
Can't compare apples and oranges.
A horsepower is 746 watts; I assume you're using 800 because you are throwing in an assumed 93.25% efficiency. That's about right for absolutely ideal conditions.The Tesla, at 400 KW, and at 800 watts per HP, works out to 500 HP!!!!
Performance information published for DC motors sold to EV enthusiasts is almost random, and certainly not subject to any oversight or standards. A DC motor value could be a one-hour rate, a one-second rate, or just fiction.The DC motors, rated at 32 and 44 HP sound like a one hour rate.
The Tesla, at 400 KW, and at 800 watts per HP, works out to 500 HP!!!!
The Tesla motor weight, at 295 pounds equals 134 KG, similar to the DC motors.
Soooooooo, the Tesla weights just a little more than the DC motors, but produces 500 HP.
Maybe for five seconds. Poof!
If it sounds too good to be true, it probably is.
I agree. The 295 pound value is the complete drive unit (which is what is being sold in this listing), consisting of motor, inverter, and transaxle. For comparison, someone who disassembled a Leaf weighed the motor + transaxle at 180 pounds (82 kg), but the motor itself is only 58 kg.The Tesla motor does NOT weigh 295 lbs - that is probably the weight of the transaxle - the motor is more like 70 kg
Right - the question about what is related to weight was about torque, not power, and it is torque which is roughly related to the "amount" of motor (radius to the flux gap, length of the rotor, windings producing flux).... TORQUE is related to WEIGHT
Modern AC motors produce a lot more POWER by revving at a very high speed
The Torque is supplied by the magnetic effects - and is proportional (ROUGHLY) to weight
The maximum torque is also proportional to weight - due to the heating effect
But if you can spin faster you can develop more power
Big DC motors are limited to about 6000 rpm - AC motors?? - 15,000??
Erm, oops. Correct.Those are mass per watt (not kilowatt)
I mean, at best it's a 12 minute rating, as, in ~12 minutes the batteries are going to be empty at 400kw draw, even if you could sustain that as voltage sags with drain.It's true that in practice the car only needs to run at this power for about 5 seconds to reach highway speed
All the info we've given will be nearly completely useless to you.i was doing a some calcs for a quad copter project and wanted to estimate the motor mass for the motor power i needed.
The problem is that for even a "full-size" (person-carrying?) aircraft the brushed DC motors will be inadequate and modern automotive motors will be far too large (even if their power to mass ratio is adequate).Not useless. Calcs are for full size copter. I want to aee what is commonly available. I know siemens / remy / emrax have some ultralight 5kw/kg motors but those arent really an option yet.
It doesn't seem reasonable to me to define a suitable motor without knowing anything about the target application, beyond the very vague "full size quadcopter". No weight, no payload or performance requirements from which to guess a weight...
From the E-bike world, where RC motors are commonly used as mid-drives on E-bikes, they can actually sustain that kind of load just fine.It has a 9.8 kW power spec, which I'm guessing is only momentary and wildly optimistic at that
E-bikes don't run multiple kilowatts.From the E-bike world, where RC motors are commonly used as mid-drives on E-bikes, they can actually sustain that kind of load just fine.
That makes sense to me. Cooling air will definitely be critical; that seems okay in an aircraft which is always moving at significant speed, but in a rotorcraft one would need to be careful.... Then the conversation came up about power density in motors, and someone doing some destructive testing on that versus a Series DC or maybe Permag motor the same power rating. What they concluded was that the RC motors are on the knife's edge. 5kW max is 5kW max. Where, other motors can easily be pushed well beyond their rated spec. Also, thermal mass plays a role in both directions. More thermal mass means brushed DC motors can soak up some abuse, but, brushless motors air cool themselves and, if they can handle the power at all, they can handle it steadily.
Yes, they sure do.E-bikes don't run multiple kilowatts.
Okay, good to know - I was thinking of legal, commercially-available electrically-assisted bikes, not motorcycles.Enforcement knowledge hasn't really kept up with the DIY community, so, almost no one respects the 500 or 750w legal limits. 1500 is about the minimum most DIYers bother with, plenty of guys running 5kW or twin 5kWs.
They're functionally hill climbing mopeds that still look like bicycles.