liveforphysics
100 TW
johnrobholmes said:
Yep.
Yet, oddly, every bike/scooter etc they had at Joby used a hobbyking BLDC outrunner as it's drive system.
Joby Motors Santa Cruz, CA
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Yep.
Yet, oddly, every bike/scooter etc they had at Joby used a hobbyking BLDC outrunner as it's drive system.
johnrobholmes
10 MW
If the motor is already available and CHEEP, why reinvent one until money is waived at you?
I wonder how large in diameter a Joby motor would need to be to produce 3hp at 44v and something like 2000 rpm. Something that would only need 3:1 geardown on a bike.
I wonder how large in diameter a Joby motor would need to be to produce 3hp at 44v and something like 2000 rpm. Something that would only need 3:1 geardown on a bike.
Thud
1 MW
After seeing those phot's of the motors.....I think I am in love....simple, clean, nearly perfect.
Time to really sell a kidney!
Time to really sell a kidney!
full-throttle
1 MW
Those motors DO look good.
A quick comparison of JM1S with the Astro 3220 (please correct me if I made a mistake) - same weight, double the power, double the volume, 2.5x the torque, 30% increase in price
@ Luke: do you think the can fit Halls?
A quick comparison of JM1S with the Astro 3220 (please correct me if I made a mistake) - same weight, double the power, double the volume, 2.5x the torque, 30% increase in price
Code:
Joby JM1S Astro 3220
RPM (Nominal) 6,000 7,500 RPM
RPM (Maximum) 9,000 12,000 RPM
Torque (Continuous) 13 5.3 N-m
Torque (Peak) 20 7.1 N-m
Power (Continuous @ nominal RPM) 8.2 4.2 kW
Power (Peak @ nominal RPM) 12.6 6.0 kW
Poles 22 8
Diameter 154 81 mm
Height 53.1 86 mm
Mass 1800 1814 grams
Volume 989 448 cc
Price 899.00 695.50 $US@ Luke: do you think the can fit Halls?
liveforphysics
100 TW
Yes, it could easily fit halls.
Keep in mind, these power numbers are for a motor with a propeller blowing on it.
Keep in mind, these power numbers are for a motor with a propeller blowing on it.
Very very impressive 
Do you have any pics of the dual bearing configuration? Do you think these motors would need an outboard bearing or could we simply just bolt a sprocket on the rotor? Do they shield the motors from debris or just run it open?
I wonder if Makani Power over in Alameda is also designing their own motors. I know they already have a in-house high voltage controller...I doubt they will be as open as JoeBen
Do you have any pics of the dual bearing configuration? Do you think these motors would need an outboard bearing or could we simply just bolt a sprocket on the rotor? Do they shield the motors from debris or just run it open?
I wonder if Makani Power over in Alameda is also designing their own motors. I know they already have a in-house high voltage controller...I doubt they will be as open as JoeBen
johnrobholmes
10 MW
Astros can be spun up to 30k without fear. 12k is taking it pretty easy on them. I wonder how fast a JM1S could spin? They obviously do a damn good job for them to hit 9k without flying apart.
Hillhater
100 TW
I would be more interested in the low KV (19) versions. (850 rpm @ 44v !)
Think how much gearing reduction you could ovoid using !
Think how much gearing reduction you could ovoid using !
liveforphysics
100 TW
Hillhater said:I would be more interested in the low KV (19) versions. (850 rpm @ 44v !)
Think how much gearing reduction you could ovoid using !
Remember, the power you get from a given motor size is directly proportional to how fast you spin it.
Take a given size motor, spin it to 1000rpm, get 1hp, take the same motor, spin it to 5000rpm, get 5hp.
Hillhater
100 TW
liveforphysics said:
Yes understood & agreed, ..
..however,..if you guys can get a 300rpm hub motor to give 3-5 kW, and if i was only looking for 2 - 3 kW from a non hub drive, then there has to be a lot of scope for one of these low kV motors to drive via the BBracket or direct to hub, with only a single stage reduction. Stokemonkey style ?? :|
doesnt low kV imply higher torque ?? .( for any given voltage)
Hillhater
100 TW
Miles said:I'm afraid not........Hillhater said:
Ahh, yes ...its higher torque for the same current on a low Kv motor ?
liveforphysics
100 TW
Hillhater said:Miles said:I'm afraid not........Hillhater said:
Ahh, yes ...its higher torque for the same current on a low Kv motor ?
If the copper fill is the same, the KV is irrelevant, being a 1/2 turn motor or a 100 turn motor makes no difference, the continuous torque output is identical if the copper fill is identical.
Hillhater
100 TW
liveforphysics said:
So what is missing from this formula..
such that Nm = 9.549 *A * Volts/Kv *Volts ...
or .. Nm = 9.549 *A/kV
or... Nm is inversley proportional to Kv (at any given current) ???
liveforphysics
100 TW
Say your hub does 100Nm of torque at 10amps, and it's a 4 turn. I^2(R) determines the copper loss heating. In this case, heating would be 100R
You re-wind it to be a 2 turn, now you apply 20amps to get the same 100Nm of torque, but R dropped to 1/4th, so I^2(R) still works out to be 100R.
You re-wind it to be an 8turn, now you apply 5amps to get the same 100Nm of torque, but R increased by 4x, so I^2(R) still works out to be 100R.
etc etc.
The heating is identical for any motor wind combination to produce a given torque value is the copper fill percentage is the same. This means the continuous torque of a motor is unrelated to the motor wind.
You re-wind it to be a 2 turn, now you apply 20amps to get the same 100Nm of torque, but R dropped to 1/4th, so I^2(R) still works out to be 100R.
You re-wind it to be an 8turn, now you apply 5amps to get the same 100Nm of torque, but R increased by 4x, so I^2(R) still works out to be 100R.
etc etc.
The heating is identical for any motor wind combination to produce a given torque value is the copper fill percentage is the same. This means the continuous torque of a motor is unrelated to the motor wind.
johnrobholmes
10 MW
What if we consider a controller with a fixed phase amp limit? I know people would adjust it to suit the voltage and motor in the real world, but how would it affect the different winds?
liveforphysics
100 TW
johnrobholmes said:
For the same battery current x voltage in (power), it will make no difference.
The lower turn count motors simply get lower FET duty cycles, and hence greater batter current multiplication. (or if its too low of a turn motor, your controller turns to plasma trying to make it have the same torque)
If you have a controller that can actually see phase currents, like a Kelly or Sevcon, then you can pick the wrong controller/voltage combo for your application, and end up not being able to realize the motors full torque potential.
full-throttle
1 MW
I'm an engineer not salesman, John :wink:johnrobholmes said:
Point taken. Don't get me wrong: Astros are the benchmark and I like their simplicity and the inherent seal.
flathill said:
don't feel too bad, ur in good company.
been trying to pin down the source of this common misconception, whereby juggling the # of turns in a coil but maintaining the coils same physical size supposedly gains u something4nothing.
i think it was this guy who also got it wrong falling into the same trap that got the snowball rolling with the wild claim of a massive increase in energy storage.
(still tracking down why a circle is divided into 360 equal parts, i'm almost there)
Nicky T. said:
what i'm pointing out is the underlined part.
the seductive trap that's in the same vein as thinking a lower Kv produces more torque.
that somehow it's possible to get free energy by simply repositioning a few wires.
lorentz proves that it can't be so.
the seductive trap that's in the same vein as thinking a lower Kv produces more torque.
that somehow it's possible to get free energy by simply repositioning a few wires.
lorentz proves that it can't be so.
boostjuice
10 kW
The larger Diameter, higher torque, lower RPM, smaller width, 10.5Kw JM2S model is now available for sale from the Joby webstore
https://www.jobyrobotics.com/category.php?id_category=6
https://www.jobyrobotics.com/category.php?id_category=6
