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[22:19:55] <codepython777> 16000mah, 14.8v - lets say
[22:20:10] <codepython777> 2400 W - > isnt that too much?
[22:20:13] <anonnumberanon> z64555, just two of these turbines, actuated so that it lifts the thing correctly, can go high, fast, for 10-15 minutes.
[22:20:49] <z64555> Ah, that's right. W's are power, J's are energy
[22:21:01] <anonnumberanon> A bit of experimenting and equation writing to use an IMU's output into the control algorithm.
[22:21:04] <z64555> W = J/t
[22:21:04] <Wetmelon> Okay and you're drawing (peak) 44A * 4 = 176A. 16Ah / 176A = 5.45 minutes. So it will last 5.45 minutes if you stall all of the motors and sit there melting wires lol
[22:21:21] <Wetmelon> If you're using them at a normal power level, it'll probably last (this is me just estimating) about 30 minutes
[22:21:38] <Wetmelon> Probably less
[22:21:56] <Wetmelon> Depends if you're doing a lot of slow speed rock crawling straight up a hill or what
[22:21:58] <codepython777> I'll have to gear them down like crazy
[22:22:07] <z64555> anonnumberanon: ok, so a bi-copter configuration with a robot on the front
[22:22:20] <codepython777> Wetmelon: I'm mostly slow speed
[22:22:46] <z64555> what'll you use for attitude control?
[22:23:13] <anonnumberanon> z64555, wait a sec, I need to find the correct turbine, this thing needs to at least be able to lift from a rest
[22:23:25] <anonnumberanon> z64555, standard IMU
[22:23:40] <codepython777> anonnumberanon: how do you power that turbine ? :)
[22:23:54] <anonnumberanon> tanks of alcohol or something
[22:23:57] <z64555> that's sensing. I asked for control. which implies control surfaces or other devices that can control. :D
[22:24:06] <anonnumberanon> hopefully it runs kinda long and is not too heavy
[22:24:07] <z64555> s/tanks/kegs
[22:24:28] <z64555> could put an umbilitcal on it
[22:24:29] <anonnumberanon> z64555, i said actuated
[22:24:36] <anonnumberanon> I don't think that part is too hard
[22:24:41] <z64555> where'd you say that
[22:24:47] <anonnumberanon> just 2 weak servos per turbine
[22:24:47] * z64555 looks at scrollback
[22:24:59] <codepython777> Wetmelon:
http://www.enertionboards.com/electric-skateboard-parts/190kv-electric-skateboard-motor/ - are there similar motors with 1/2 the power requirements, well built? half the price preferably :)
[22:25:00] <z64555> nahh
[22:25:05] <z64555> not 2 per turbine
[22:25:26] <z64555> just two
[22:25:48] <anonnumberanon> z64555, just two of these turbines, actuated so that it lifts the thing correctly, can go high, fast, for 10-15 minutes.
[22:25:55] <anonnumberanon> (i quote)
[22:26:06] <z64555> ok, sorry. half asleep
[22:26:15] <anonnumberanon> z64555, you think can be done with only one axis per turbine?
[22:26:20] <z64555> yup
[22:26:26] <z64555> one to control elevation
[22:26:29] <anonnumberanon> making the math thus more complicated?
[22:26:33] <z64555> the other to control roll
[22:26:53] <z64555> weight of the robot will keep it level
[22:26:55] <Wetmelon> codepython777: Well that's hard to say
[22:27:06] <anonnumberanon> roll, pitch, yaw are the things in general, but what is elevation, you mean power?
[22:27:13] <Wetmelon> They're much slower, so they probably have higher torque, and you won't have to gear them down as much
[22:27:14] <z64555> nah
[22:27:18] <z64555> elevation of fthe ducts
[22:27:22] <rue_shop4> damnit it smeared the top layer
[22:27:25] <z64555> thing like an elevator
[22:27:30] <z64555> on an airplane
[22:27:49] <z64555> for a cesna it's the control surface on the tail. the horizontal one
[22:27:58] <anonnumberanon> ill paste you something interesting (but that only has one motor)
[22:28:36] <z64555> heading would be controlled by differences in rotation speed
[22:29:41] <anonnumberanon> https://www.youtube.com/watch?v=A5b9LnzjGgU
[22:30:03] <z64555> videos. always with the videos
[22:30:12] <z64555> does nobody write articles anymore
[22:30:15] <anonnumberanon> haha on 3G?
[22:30:27] <codepython777> Wetmelon: 150kv vs 300kv - what is better for my application?
[22:30:43] <anonnumberanon> if you've noticed z64555 I don't usually post uninteresting videos
[22:30:49] <Wetmelon> mmm probably the lower one, because you want the torque
[22:30:57] <Wetmelon> And you don't want to add weight through gearing
[22:31:20] <codepython777> Wetmelon:
http://www.hobbyking.com/hobbyking/store/__18184__Turnigy_Aerodrive_SK3_6374_149kv_Brushless_Outrunner_Motor.html
[22:31:50] <Wetmelon> Oh man that's a beefy motor
[22:31:59] <codepython777> Wetmelon: arent gears a requirement? I need 500rpm at most, right?
[22:32:11] <Wetmelon> No idea what your RPM reqs are
[22:32:32] <codepython777> 150rpm/v => 4V and I am done !
[22:33:47] <z64555> looks nice
[22:34:02] <z64555> anyway as I was saying with your jetpack
[22:34:23] <z64555> You can tilt the rotors both up/down for elvation. this'll control pitch
[22:35:10] <Wetmelon> codepython777: lol. Only if you don't put a load on the motor ;)
[22:35:14] <z64555> you can tilt the rotors respective to each other to do heading. (sorry got that backwards earlier)
[22:35:26] <z64555> and do different rotor speeds to control roll
[22:36:09] <anonnumberanon> yeah for some reason i wasn't thinking that turbines rotate, so you can use them just like propelled spinny motors?
[22:36:10] <z64555> 2 servos, 2 motors
[22:36:39] <z64555> turbines are like continous servos. you control speed via PWM min/max
[22:36:41] <z64555> instead of angle
[22:36:53] <codepython777> Wetmelon: as the mm size of the motor decreases, its kv increases, why?
[22:37:14] * z64555 is barely awake
[22:37:19] <codepython777> Wetmelon: so if i put a load, I get 150rpm from 14v?
[22:37:37] <anonnumberanon> z64555, they all seem to be $2.5k
[22:37:41] <anonnumberanon> it's ridiculous
[22:37:49] <z64555> make your own
[22:37:49] <Wetmelon> I'll answer question 2 first: Not necessarily. it all depends on how *much* load there is
[22:38:05] <Wetmelon> THe problem is that these manufacturers don't really give good specs on load vs RPM vs power etc
[22:38:12] <Wetmelon> Proper motor manufacturers give you graphs of that stuff
[22:38:17] <z64555> kV is a propertey of motor speed vs. voltage
[22:38:42] <z64555> As the rotor diameter decreases, the amount of torque needed to spin it decreases
[22:38:50] <z64555> this is before applying a load
[22:38:51] <Wetmelon> As for question #1: Very good observation! What you're seeing is as much a property of the windings of the motor as it is rotational inertia
[22:39:21] <z64555> wetmelon is correct. :)
[22:39:40] <Wetmelon> Conversely, z64555, the larger the rotor, the longer the moment arm, so you get more torque / amp (generally)
[22:39:50] <z64555> yes
[22:40:22] <codepython777> can i drive a truck directly without gearing using the 149kV 63mm motors?
[22:40:59] <z64555> heh. I have no idea. kV is a measurement of speed vs. voltage
[22:41:08] <z64555> not torque
[22:41:10] <Wetmelon> From what you said - 20lb, 4 motors, and thsoe specs... I'd say probably yes. But it'll probably go too fast xD
[22:42:23] <codepython777> I think 2 motors are more than enough for that kind of load
[22:42:25] <z64555> there's a calculation somewhere that if you know the no-load torque and current draw, you can calculate the load torque and current draw
[22:42:28] <Wetmelon> It's really hard to say though, z64555's right. They're missing "Ki" (torque / amp) rating
[22:42:30] <codepython777> I think one could drive it with one motor
[22:43:00] <z64555> Yeah. motors like these are generally rating for speed. not torque. because usually it's speed you're after
[22:43:24] <z64555> If you were wanting a motor that was used for torque, it'd say something like 5Hp or 12N
[22:43:53] <codepython777> z64555: are there motors similar to these which have low rpm, high torque and are efficient in using power?
[22:44:12] <z64555> yeah. they're called stepper motors
[22:44:23] <anonnumberanon> z64555> make your own
[22:44:28] <codepython777> z64555: I forgot to mention efficent in using power and weight :)
[22:44:30] <anonnumberanon> what a fun project that would be...
[22:44:53] <Wetmelon> codepython777: Your best best is a brushless DC outrunner for high torque, high power, low weight
[22:44:56] <z64555> anonnumberanon: just cut open a 2L soda bottle. bamf. you have a duct.
[22:45:12] <codepython777> Wetmelon: outrunner = turnigy?
[22:45:14] <Wetmelon> OR a brush DC outrunner for higher torque honestly
[22:45:29] <z64555> no. outrunner is the type of motor. it describes which part is the rotor.
[22:45:31] <Wetmelon> No, outrunner means the rotor is on the outside and the stator is attached to the frame
[22:45:37] <Wetmelon> What he said ^
[22:45:41] <codepython777> ah ok
[22:45:49] <z64555> vs. an in runner which the rotor is on the inside. a traditional motor
[22:46:00] <codepython777> So I'm looking for an outrunner with high torque, low rpm
[22:46:08] <z64555> brushless inrunners are fascinating. :D
[22:48:15] <Wetmelon> Dat RPM doe.
[23:01:34] <z64555> anonnumberanon: get how I was envisioning your twin-rotor?
[23:02:57] <z64555> it might be more practical to have the two servos control the elevation of the rotors independantly, rather than to have one servo control elevation, and one to control the twist
[23:03:23] <anonnumberanon> Elevation, twist?
[23:03:38] <z64555> elevation -> pitch
[23:03:39] <anonnumberanon> (i still don't understand what you mean by elevation by the way)
[23:03:42] <anonnumberanon> okay
[23:03:51] <anonnumberanon> twist being roll?
[23:04:00] <z64555> no, twist controls heading
[23:04:19] <z64555> twist is the axis that goes through both centers of the rotors
[23:04:30] <z64555> one rotor pitches forward
[23:04:35] <z64555> the other rotor pitches back
[23:05:05] <anonnumberanon> You are implying two turbines with opposite spin directions?
[23:05:10] <z64555> yes
[23:05:18] <z64555> that would control the roll
[23:05:24] <z64555> well
[23:05:45] <z64555> no. that would also control the heading, but the thrust differential would control roll
[23:06:05] <anonnumberanon> it would be random and dangerous as fuck is what you are to mean
[23:06:14] <z64555> nah, not that random
[23:06:23] <anonnumberanon> now I like dangerous, but I hate random
[23:06:25] <anonnumberanon> :)
[23:06:58] * anonnumberanon remembers fondly his first botched quadcopter controller that was very random
[23:06:58] <z64555> the heading change due to differences in rotor speed is predictable, and can be countered by the twist amount
[23:08:08] <z64555> k. understand yet? :P
[23:11:00] <anonnumberanon> yes just like a quadcopter
[23:11:14] <anonnumberanon> i see what you mean though yes
[23:11:27] <anonnumberanon> 2 actuators feels good
[23:11:53] <anonnumberanon> now to find $500 ones or make them myself
[23:11:54] <z64555> well, no, not *just* like a quadcopter. it's different in terms of how the thrust is manipulated
[23:12:08] <z64555> just get a 2-liter bottle
[23:12:31] <anonnumberanon> yeah okay with some cocacola and a mentos in them? that'll surely work
[23:12:39] <ace4016> look at the H-46 Sea Knight or the H-47 Chinook for examples. differential control like that isn't new or uncommon
[23:12:42] <anonnumberanon> and cut out some vents in the bottle connected to servos...
[23:12:53] <z64555> ace4016: both of those use a rotor head
[23:13:01] <z64555> here is just a simple prop
[23:13:04] * ace4016 should probably read up
[23:13:15] <z64555> with a duct around it
[23:13:23] <ace4016> rotor heads are just bigger props :P
[23:13:30] <z64555> anonnumberanon: no I'm serious. all the ducting there is to reduce the amount of backflor
[23:13:39] <z64555> *backflow from the downdraft
[23:13:44] <z64555> ace4016: no
[23:13:53] <anonnumberanon> z64555, oh
[23:13:53] <z64555> they're actuated. with swash plant
[23:14:32] <ace4016> so are modern props
[23:14:37] <z64555> Ducted fans are cheifly cylindrical, with a tiny bit of taper
[23:14:54] <z64555> ace4016: we're talking hobby airplane propellors here
[23:15:02] <ace4016> ah
[23:15:06] <z64555> which are fixed pitch. no swashplate
[23:15:21] <ace4016> shame :P
[23:16:23] <z64555> the top of the duct would be ideally be level with the center of the propellor
[23:16:49] <z64555> but realiestically, sticks up by about a cm
[23:17:33] <z64555> since the propellor can flex
[23:18:05] <anonnumberanon> not only hobby airplanes!
[23:18:21] <anonnumberanon> military drones! (the winged kind)
[23:19:19] <z64555> fascinating use of ducting:
http://imgur.com/gallery/3wqS2
[23:19:40] <z64555> (more like funneling, really)
[23:20:56] <z64555> ok. The reason why ducted fans have small tapers, instead of a large taper, is that you lose energy from the downdraft fighting against the sides of the duct
[23:21:38] <z64555> but you still have a bit of a taper, to promote a laminar flow
[23:23:36] * z64555 sleeps