What does Astro Motors PDF Data indicate?

[SoSauty]

I'm edgin' closer to an RC bike build with an Astro 3210. Studying AstroFlights' Data raises more questions than it provides answers. Now I possess an average "Joe's" working knowledge of electricity, but the data makes me skeptical, verry skeptical For now I'm going to try to post their data and ask knowledgable folks, "Is the data valid?" If not, I have a list of concerns and perceived mathematical discrepencies and will post those later. Here it is:

• Astro 3210 Brushless Motor $399.95
  
  Stock number P/N 3210
  Typical Winding 6 Turns #13
  Speed Constant 275 rpm/volt
  Torque Constant 5 inch ounces/amp
  Winding Resistance 30 milliohms
  No Load Current 1 amp
  Max Continuous Amps 75 amps
  Peak Amps 1 minute 100 Amps
  Typical Voltage Range 12 to 48 volts
  Typical Power Range 2,000 to 3,000 watts
  Typical Efficiency Range 90 to 95%
  Typical Speed Range 6,000 to 10,000 Rpm
  Stator 24 slot 8 pole winding
  Rotor 8 pole Sm Cobalt
  Bearings Two Ball Bearings
  Motor Diameter 3.2 inches
  Motor Length 2 inches
  Motor Weight 32 oz.
  Motor Shaft 3/8 inch diameter
  
  Motor Constants for Various Winding Options
  Motor Kv Kt No Load Winding Best Motor
  Windings rpm/volt in oz/amp Amps Resistance Amps Efficiency
  2 turns 677 2.0 3.0 amps 0.005 ohms 85 amps 93%
  3 turns 451 3.0 2.0 amps 0.011 ohms 57 amps 93%
  4 turns 339 4 1.5 amps 0.020 ohms 42 amps 93%
  5 turns 271 5 1.2 amps 0.030 ohms 34 amps 93%
  6 turns 225 6 1.0 amps 0.045 ohms 28 amps 93%
  7 turns 194 7 0.9 amps 0.060 ohms 24 amps 93%
  8 turns 169 8 0.7 amps 0.080 ohms 21 amps 93%
  10 turns 135 10 0.6 amps 0.120 ohms 17 amps 93%
  12 turns 113 12 0.5 amps 0.190 ohms 14 amps 93%
  
  Operation at maximum continuous torque for various winding options;
  Motor Operating Continuous Shaft Motor Shaft Motor
  Winding Voltage Amps Torque Rpm Power Efficiency
  2 turns 12 volts 187 amps 375 in oz 7,500 rpm 2.8 Hp 90%
  3 turns 18 volts 106 amps 375 in oz 7,500 rpm 2.8 hp 90%
  4 turns 24 volts 94 amps 375 in oz 7,500 rpm 2.8 Hp 90%
  5 turns 30 volts 75 amps 375 in oz 7,500 rpm 2.8 Hp 90%
  6 turns 36 volts 63 amps 375 in oz 7,500 rpm 2.8 hp 90%
  7 turns 42 volts 54 amps 375 in oz 7,500 rpm 2.8 hp 90%
  8 turns 48 volts 47 amps 375 in oz 7,500 rpm 2.8 Hp 90%
  10 turns 60 volts 38 amps 375 in oz 7,500 rpm 2.8 Hp 90%

Also: http://www.astroflight.com/pdfs/3210WEB.pdf

 

[Miles]

If you have specific questions, just ask them......

Astroflight are one of the few firms that actually give all the pertinent data....

 

[recumpence]

We have found many typos in Astro's spec list. That should change with the new owners.

What are your specific questions?

Matt

 

[SoSauty]

If I contemplated a bit, there's many questions from various angles, here's a few from the top of my head to start with;

Kv is 135 @ 10T, a Castle HV160 ESC sorta limits the voltage to 44.4V (12s Lipo); so that's 6000 rpm, yet all continuous torque results have '7500rpm' beside 'em. Under what load can the 3210 hit 7500rpm or higher? Will 6000 - 10,000rpm motor speed range apply to the 10T 3210, 2T to 12T, equally?

For 6Turn 3210, one may run 75amp continous or 100amp burst for 60 sec. 6T likes 30V yet 10T uses 48V (tested with 60V elsewhere). Can a motor rated for higher Voltage utilize the same number of Amps? Ypedal says he relies on his CA to keep from 'burning down' his Astro rig; 1 rush trip trip home he ran 60-80A, seems that's his peak Amp usage. Also, a 10T maxes torque @38A while a 6T maxes @63A. Mathematically, a 10T might hit max power around 67.5A and handle a burst around 89A if Watts reflects the limit. Can a 10T handle 100A for 60sec or even 90A for 15sec? What burns down an Astro3210? What Amp can be throttled safely?

Is the 2000 to 3000W rating input or output? Will the motor pull 44V @ 85A = 3,750W X .90% efficiency =3350Watts for 15seconds?

Just looking for educated trends, surly I can sense when the motor is maxed out. Sorta like you know when you feel cold yet a weather report is useful.

 

[Miles]

So your question should have been: Will someone please explain the basics of motor theory to me, because I can't make sense of the specifications?

 

[SoSauty]

We have found many typos in Astro's spec list. That should change with the new owners.

Thank you Matt.

Yes, suppose much can be extropolated from the data if one has a solid basis in motor theory.
Back in the 70's, I paid a typist to pretty up a graduate math education project. That individual never could clear out the math error/typos after numerous attempts. I admittedly have a limited understanding of motors, yet have enough life experience/ knowledge to suspect the data as it's purported.

AstroFlight Inc is a 10min drive from my L.A. cardiologist, so I could drop in on 'em. Yet right now they are in an ownership change and being a busy business, I'd rather put this sort of discussion out on this forum, especially since the expertise shared here has been truly amazing

As the situation exists, Matt has paved the way for adventurous e-bike hobbyist to attempt RC builds Wouldn't it be nice to know what the limits are for the motors? If I can pull this together and run it in Tucson next April, be great to know if I screw the throttle over another 15amp without risking a DNF.

I have invested in a bike frame, CA, forks, Astro & drive, disc brakes and other misc. . . Wouldn't it save money and time to learn now, rather than after a number of blown motors? So yes Miles, both tips on motor theory and clearing up some spec typos would be insightful, not just for myself, but others looking at an RC venture :wink:

http://www.endless-sphere.com/forums/viewtopic.php?f=30&t=13265

 

[Miles]

Ok. Forget watts, for a moment. The maximum continuous amps value is the most important thing (for the 3210 this will give 375 inch ounces of torque for a specific winding). If you are doubtful about the max. continuous amps values, you can check them using the Kt (torque constant) given. You can cross check Kt against Kv, too.

 

[SoSauty]

OK, set aside Watts, sounds as my numbers maybe some sort of guide. Max continous torque 38A would yield 67.5A as max continous (using 3K) and 89.9A as a burst (though I'd be more conservative in applying hi Amps). Thus Y-pedal's conservative application of Amps. This assumes a 6T motor handles 75A continous and 100A burst. (375 in/oz = 1.95 lbs torque)

In considering a single speed motor drive, I'm hoping to get a sense of "loading" the little 2lb buzzer.

Next, the 135Kv and 38A yields a trend toward 3400rpm for max torque and 135Kv@44.4V for 6000rpm provides clues to its' operational range.

Proportionally: (given that in reality rpms can vary alot)
3600rpm to 6000rpm if referenced to orginal 6,000rpm to 10,000rpm
3400rpm to 6000rpm if 67.5A applied w/38A being the low range
2535rpm to 6000rpm if 90A applied w/38A being the low range

Or, the speed constant for 10T is 1,500rpm less than for a 6T, so possibly a 4800rpm to 8000rpm operating range.

Surly, rpms will be greater at 89.5A than 67.5A regardless of Kv.
Assuming the ESC doesn't blow under low speed loads.

That's quite a difference. Which is more realistic operational range; 3600/6000rpm or 4800/8000rpm.

Anyway, If I can figure this out I'd like to supplement Astro's Spec sheet to suit those of us getting an Astro3210.

 

[Miles]

For the 10t winding, 38 amps is the maximum continuous rating.

Kt (torque constant) tells you how much torque you get for each amp. As Kv goes up, Kt goes down.

 

[drewjet]

I'll put this as simple as possible. Stop looking at torque and amp numbers. If you are building a racer you need to step up to a 3220, or even better Matt's motor when it finally becomes available. I don't believe 3210's are up to racing competitively. What you need to look at is volts, gear reduction, tire diamater and top speed desired. Once you have all that it is easy enough to figure out what KV you need. Keep in mind the higher the KV the more potential power the motor has. However the more KV you have means less windings, which increases the strain on the ESC, thus making it more likely to have a plasma event.

Max amps will come at low speed and high thottle. Trust me on this you won't be there long as the Astro will be up to speed very quickly. My bike is geared for 30 MPH and the only thing keeping the acceleration to speed below about 3 seconds is not pulling the throttle back too far too fast or you end up on your ass.

Why don't you post the above info and what kind of performance you are looking for and I am sure we can help you pick a motor.

 

[SoSauty]

Thanks Drewjet, I can only hope my 3210 has half that power

Actually, I don't wish to get on the podium, just hope to make the main event at Tucson. I'm 55 and have crashed enough, just want 1 (or more) last fun race and Tucson is too far to drive just to run in a heat. I'm set for a 3210, my bike geometry and brakes are not really for the 50mph+ that the 3220 would deliver. I think I can build a sub 50lb bike, pad my safety margin, squeak into the main, and have a hoot doing it.

By the way, my wheelbase is 42.6" 68 degree fork rake, 3 speed freehub (yes), 24" X 2.00" tires, 203mm front disc brake.
(Update: just ordered 15AH 12S Lipos)

Reliability. I'd love to know if it's better to gear hi to max mph on the two 200yd straights, or gear lo; and some parameters to run the buzzing motor.

One comment you made about lo-speed Amps helps. I guess just watch the CA and not exceed (?)60A.

(I'm actually pretty interested in the 8150 motor but can't determine if it yields a few 100W more than 3210 or a Kw more using the Castle HV160 ESC.)

Are you planning on going to Tucson? I dare you to lap me on your Astro 3220

 

[drewjet]

In that case my reccomendation would be to go with a 7 turn 8150 wired Y with a KV of 107. Run an 11 tooth front and 92 tooth rear 219 chain on 12S Lipo and an Ice 160. Probably will need at least 15 AH maybe 20. Left side drive (one of the Currie hubs) That give you a no load speed of 45 MPH and probably a real world speed of 40 MPH. I think you will have a hard time staying under 50 Lbs, but not over by much. My bike, a similar set up, except a 3220, Matts reduction drive and only 10 AH, weighs 52 lbs.

Sounds like a fun ride. Unfortunately I don't see me being able to make it. I do 6 or 7 electrathon races per year and that is about all I can handle.

 

[SoSauty]

Still, if I can nail down Amps and motor operational rpms, think this would be good info for others considering an RC build.

6T max torque at 63A; max continous 75A w/ 100A burst
Is my thinking valid;
10T max torque at 38A; So, max continous 67.5A w/ 90A burst? (max continous 45A w/ 60A burst)
(the 67.5A number is an old value I got by dividing 3000W by 44.4V)
6T motor operation range 6000 to 10000rpm
Which is more realistic for e-bike geared hi-speed;
10T 3600/6000rpm or 4800/8000rpm?

 

[Miles]

10T max torque at 38A; So, max continous 67.5A w/ 90A burst?

SS,

I'm not sure what you are doing here?

38 amps is the maximum continuous amps rating and corresponds to the maximum continuous torque output. Where do you get 67.5A from?

 

[SoSauty]

Sure, my understanding of the spec sheet is that there are 1)Max continous torque amps, 2)Max continous amps the motor can handle, and 3) short term burst amps. Let's disregard the burst amps for now.
http://www.astroflight.com/index.php?main_page=product_info&cPath=9&products_id=122
The 1st page is based on the 6Turn motor and states it can run at 75 continous amps. Yet the PDF also states that max continous torque is acheived at 63A, so I assume the page1 75A and PDF 63A are 2 separate ratings. Some of the PDF columns have IMO nonsense values. However, the max torque values seem sensible, so a 10Turn motor developes max torque at 38A vs 6T 63A. Hmmm, different Kv and max torque amps.
http://www.astroflight.com/pdfs/3210WEB.pdf
math:
6T; 63A to 75A is to
10T;38A to 45A. I estimate that a 10T can run continously at 45A with available data.
(38A is given when 60V is applied, so the 45A could be higher, since 3000W/44.4V=67.5, perhaps as hi as 67.5A )

Yet can someone validate or correct me?

 

[Miles]

Yes, there is a discrepancy. I would just use the data from the PDF and assume that it was a fairly conservative rating.

 

[liveforphysics]

Also, keep in mind, the amps you read at your CA have no bearing on the amps the motor winding is getting. (for example, the CA could say 50amps while the motor is getting 150amps etc)

All the winds are capable of identical performance, as they all have identical copper fill.

If you're limiting yourself to 48v, then choose the motor that maxes the mechanical RPM limits of the rotor at 48v (or perhaps 0.8x48v if you're going to resist from ever free-reving the motor) if you're looking to max performance.

This gives you maximum performance for your voltage limits, and determines the gearing needed after you choose a desired speed range. If this reduction seems difficult for your appliction, then choose a lower KV value, and understand you will be decreasing performance potential in favor of ease of construction.

If you're looking to get sporty/racey with it, I think the 3210 is a bit of a toy IMHO, and I would stick with the 3220.

 

[liveforphysics]

Also, try to understand, when they list a wattage and/or current spec, a multiplier of >5-10x could be at work between having the motor powering something like a ducted fan jet vs running in still air on a motor dyno etc. This is why it's impossible to give a "continous power" or "continous current" rating for a motor that is much more than a +-500% ball park guideline.

If you mount your motor into a giant aluminum clamp bracket that is finned and has excellent airflow, and always runs at an efficient RPM, it might handle 10kw continously. If you mount it in a little PVC shrowd with minimal airflow, or cover it etc, it might burn up at 500w continous.

 

[Miles]

Also, try to understand, when they list a wattage and/or current spec, a multiplier of >5-10x could be at work between having the motor powering something like a ducted fan jet vs running in still air on a motor dyno etc. This is why it's impossible to give a "continous power" or "continous current" rating for a motor that is much more than a +-500% ball park guideline.

The PDF is under "Industrial Motors", so I should imagine the ratings listed are pretty cautious

 

[SoSauty]

Great info LFP, you answered one of my unasked questions, (I think) wouldn't dialing in close to max Volts enhance performance vs the concept that Volts & amps balance to equal a Watts operating limit? So, would an 8T Astro3210, suggested for 48V (or is this a typo?)have any advantage over the 10T 60V (?typo?) for hi-end performance when limited to 37-48V 12S by the HV160? Specs suggest the 10T can handle 60V yet the HV160 won't. Do you know if I can bolt in/exchange motors with Matt's motor/drive mounting? I would utilize the 10T motor but have the 8T for Spooky Tooth.

Luke, you raise another thought, do you think streaming air to the motor would noticeable increase its' performance on a 40ish mph e-bike?

Miles, appreciate your remarks, they caused me to look again at my arithmetic :wink: which I need to do more often. Good observation about the 'Industrial Motor' heading. With your 'basic motor theory', 'ya think I could milk a tad more performance out of the 8T vs the 10T relying on a 12S 44V Lipo threshold?

As to the 3210 being a toy, I started off wanting to run 1000W but no one showed interest. Then I threw out 1500W and 1 soul said "yeah!" Then I found the winners lap times at Spooky Tooth DR, as well as Dogman's lap times. I perused Google Earth Tucson Kart track. With e-bikes jumping into the foray along with ICE racers ramping up, a 1500W setup might not make the main in 2011. Yet 3000W should. I enjoy competition, middle pack is about as fun as being TopCat. Those aiming to take all the cookies from the jar have their challenges. I have mine. Making the main with a 3210 could be a test if many of the bikes are a higher caliber 2011. Then again, not getting lapped in the main would be an even greater feat. There are trade offs, not all are negative. With a 3210, I can probably make it thru the heat on 15Ahr batt, or somewhat less than with a full sz racer.

If I were running 3220, my wheelbase would be 2" longer with heavier frame and possibly double disc brakes up front. To benefit I'd need 60% more Lipo. With a simple bike build, I aiming for sub 50lb. Later I can enhance performance, maybe the 8150 motor, lighter build enabling a stronger controller and a few more LIPO