Doctorbass
100 GW
dnmun said:
I would say Yes on that.. it is better to back of the throttle when switching.
I don't like hub motors - (crappy ones)
- Thread starter swbluto
- Start date
I would say Yes on that.. it is better to back of the throttle when switching.
johnrobholmes said:
That's interesting. Higher efficiency should mean a higher continuous power limit so I was wondering what a comparable power limit on a popular Inrunner would be, the 3210, and this paper at http://www.google.com/url?sa=t&sour...0ejYCg&usg=AFQjCNG12Z9Yz-7Ka6kb0kmHpkMs5zVVNg
seems to suggest it's somewhere north of 3 HP. Care to comment? It seems the HXT 80-100 outrunners can handle >6 HP continuously.
johnrobholmes
10 MW
Can HXT motors really handle 6hp? Can't trust numbers from the manufacturer or retailer in most cases. I found the numbers for Scorpion motors inflated last I ran mine, and they are pretty reputable.
recumpence
1 GW
Bob from Astro (spoke to him directly about this) said 5kw for 30 seconds is reasonable. He rates his motors very conservatively.
I can tell you I have pulled 7kw with my Terminator a bunch of times untill I blew the controller. It handled that just fine. Bob said his motors are every bit as rugged as my Terminator. Hmm, that would be awesome because that freakin Terminator cost a cool $1,100!
Remember, very few people will be pulling several KW for more than a few seconds at a time.
Matt
I can tell you I have pulled 7kw with my Terminator a bunch of times untill I blew the controller. It handled that just fine. Bob said his motors are every bit as rugged as my Terminator. Hmm, that would be awesome because that freakin Terminator cost a cool $1,100!
Remember, very few people will be pulling several KW for more than a few seconds at a time.
Matt
johnrobholmes
10 MW
There is an energy fair on my local campus, and they had a full fairing recumbent that used 440 watts to sustain 51mph. Now side breezes would be a problem, but think if our bikes could be so efficient!!
recumpence said:
That depends, really. If someone had set their system up to go 30 mph up an 8% hill, then I can imagine you'd easily be pulling more than several kW for more than a few seconds. Ideally, I want my future bike to be able to go up an 8% hill at 40 mph just so accelerating to 30 wouldn't be a problem.
Just to dispel some common assumptions(Including ones I've made):
I was checking out the max efficiency data for a common hxt / budget outrunner motor: http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=5141&Product_Name=HXT_80-85-B_170Kv_Brushless_Outrunner_(eq:_70-40)
and using the test data they provided, I found the max efficiency was between 75-78%. So, yeah, it seems the "quality motors" have the edge on efficiency when it comes to R/C motors. It seems that the budget motors are about as bad as hub motors when it comes to max efficiency on the motor itself, but adding a drive train means less overall efficiency for the budget ones. However, they seem to routinely handle 4 kW continuous which 40x motors usually can't so this is evidence of better cooling and a higher power limit.
I was checking out the max efficiency data for a common hxt / budget outrunner motor: http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=5141&Product_Name=HXT_80-85-B_170Kv_Brushless_Outrunner_(eq:_70-40)
and using the test data they provided, I found the max efficiency was between 75-78%. So, yeah, it seems the "quality motors" have the edge on efficiency when it comes to R/C motors. It seems that the budget motors are about as bad as hub motors when it comes to max efficiency on the motor itself, but adding a drive train means less overall efficiency for the budget ones. However, they seem to routinely handle 4 kW continuous which 40x motors usually can't so this is evidence of better cooling and a higher power limit.
I also ran the numbers on HXT's "quality line"(Turnigy-SK) and it appears the max efficiency only improved by about 5%, so it seems like 73-81% are realistic peak efficiency numbers with Hobby-city motors. Quality brands seem to easily reach into the high 80s like close to 90%.
Oh yes, very true. Meaning, you have a practical power limit of nearly twice as much at max efficiency(Except the output power wouldn't be at its max at max efficiency, but it sounds like you'll get some significant improvement of that kind of scale.) for the same mass/cooling scheme.
I just wonder if there's anyone that manufacturers sub-250 kV quality outrunners that'll take 4-5 kw continuous. I've seen things like the 10kw plettenberg, but 1-grand seems like it's getting a tad ridiculous. I'd more than be willing to double up on the cheap motors than to buy one big expensive motor if the power limit was my concern.
I just wonder if there's anyone that manufacturers sub-250 kV quality outrunners that'll take 4-5 kw continuous. I've seen things like the 10kw plettenberg, but 1-grand seems like it's getting a tad ridiculous. I'd more than be willing to double up on the cheap motors than to buy one big expensive motor if the power limit was my concern.
Miles said:
Yes, true.
I was looking at this AXI, http://www.modelmotors.cz/index.php?pag ... &line=GOLD, and it appears that with the data available at 30V for no load current, the peak efficiency would be 88-89% which compares with their claim of 94% max efficiency. Peakeff.com seems to think it's ~90.5%. I wonder where they're getting 94?
Also, my simulator suggests this motor would good at 2.2-2.4 kW out(continuously) or what corresponds to ~2.8 kW in at 80% efficiency which is pretty good considering that a similar weight hobby-city motor could only probably tolerate 2 kW in and 1.5 kW out. At $600, though, I'd probably get one of hobby-city's $200 "6kw-7kw" (4kw continuous, likely) motors and just upgrade the bearings and glue as needed. But, I'm hesitant to buy a more expensive hobby city motor since I actually haven't seen an "verified improvement" on endless-sphere, yet, with one of these motors to know if the glue can be satisfactorily replaced.
Here's the "hard data" as opposed to mere speculation and various opinions.
Okay, here's a fair comparison between two different "typical" type of systems. They both use the same battery (A 48V 10Ah ping), and the only thing changed is the motor. The one motor is an HXT 74-63(? Something like that) that has a kV of 200 and internal resistance of .03 ohms and the hub motor bike is a 407 on a 26" wheel. They're both limited to 20 amps and the power is the OUTPUT power - this is the power that gets you moving on the road, not just the power going in the motor and being partially wasted. The outrunner is on a scooter with 8 in. wheels but the results are mechanically equivalent on a bike if it had "equivalent gearing".
At 10 mph:
HXT outrunner motor: Power ~625 watts. Efficiency ~68%
C'lyte 407: Power ~ 475 watts. Efficiency ~52%
At 20 mph:
Outrunner motor: Power ~775 watts Efficiency ~ 83%
C'lyte 407: Power ~690 watts Efficiency 72%
At 30 mph:
Outrunner: Power ~785 watts Efficiency ~84%
C'lyte 407: Power ~425 watts Efficiency ~83%
As a quick observation, you'll notice the outrunner "plateaus" relatively quickly in power and efficiency (Like shortly after 15 mph) and stays nearly constant past that whereas the 407 motor is more "peaky" with a maximum power at 26 mph of 730 watts and it quickly plummets past that (coincidentally enough, my top speed on the crystalyte 407 was about 26-27 mph without pedaling), and its peak efficiency doesn't even come close until it gets past 24-25 mph. Also, since the outrunner had more power going out in the lower part of the speed range, it has significantly greater acceleration and hill-climbing speed. On an 8% incline, the simulator predicts 9 mph for the C'lyte 407 whereas the scooter has a speed of 16 mph.
So, yeah... with proper gearing, these outrunners easily beat hub motors with the same type of batteries. The secret is that it efficiency and power peaks and plateuas early which is the result of the motor having a much lower internal resistance than a typical hub motor. Just to let you know, the scooter would go about 27 mph in this situation on flat land and so would the crystalyte so not much way in terms of top speed, but that really has to do a lot to do with the sucky ping batteries. :lol: On a hill and during acceleration, though, outrunners ROCK! On higher power batteries, all you really have to do is increase the current-limit and you're going to go faster (upto a certain point, and then you'll need to increase the voltage) whereas you have to increase the voltage to make a hub motor go faster and that quickly approaches its limitations.
(An example, on 48V - 27 mph was all that I was going to see with the 407 no matter if the current limit was 20 or higher. On a mere 33 volts, I could increase my speed upto 35 mph by upping the amp limit to 50 amps! Right now, I'm currently getting 30 mph at a current limit of 40 amps just to conserve energy so I can get reasonable distance.)
Okay, here's a fair comparison between two different "typical" type of systems. They both use the same battery (A 48V 10Ah ping), and the only thing changed is the motor. The one motor is an HXT 74-63(? Something like that) that has a kV of 200 and internal resistance of .03 ohms and the hub motor bike is a 407 on a 26" wheel. They're both limited to 20 amps and the power is the OUTPUT power - this is the power that gets you moving on the road, not just the power going in the motor and being partially wasted. The outrunner is on a scooter with 8 in. wheels but the results are mechanically equivalent on a bike if it had "equivalent gearing".
At 10 mph:
HXT outrunner motor: Power ~625 watts. Efficiency ~68%
C'lyte 407: Power ~ 475 watts. Efficiency ~52%
At 20 mph:
Outrunner motor: Power ~775 watts Efficiency ~ 83%
C'lyte 407: Power ~690 watts Efficiency 72%
At 30 mph:
Outrunner: Power ~785 watts Efficiency ~84%
C'lyte 407: Power ~425 watts Efficiency ~83%
As a quick observation, you'll notice the outrunner "plateaus" relatively quickly in power and efficiency (Like shortly after 15 mph) and stays nearly constant past that whereas the 407 motor is more "peaky" with a maximum power at 26 mph of 730 watts and it quickly plummets past that (coincidentally enough, my top speed on the crystalyte 407 was about 26-27 mph without pedaling), and its peak efficiency doesn't even come close until it gets past 24-25 mph. Also, since the outrunner had more power going out in the lower part of the speed range, it has significantly greater acceleration and hill-climbing speed. On an 8% incline, the simulator predicts 9 mph for the C'lyte 407 whereas the scooter has a speed of 16 mph.
So, yeah... with proper gearing, these outrunners easily beat hub motors with the same type of batteries. The secret is that it efficiency and power peaks and plateuas early which is the result of the motor having a much lower internal resistance than a typical hub motor. Just to let you know, the scooter would go about 27 mph in this situation on flat land and so would the crystalyte so not much way in terms of top speed, but that really has to do a lot to do with the sucky ping batteries. :lol: On a hill and during acceleration, though, outrunners ROCK! On higher power batteries, all you really have to do is increase the current-limit and you're going to go faster (upto a certain point, and then you'll need to increase the voltage) whereas you have to increase the voltage to make a hub motor go faster and that quickly approaches its limitations.
(An example, on 48V - 27 mph was all that I was going to see with the 407 no matter if the current limit was 20 or higher. On a mere 33 volts, I could increase my speed upto 35 mph by upping the amp limit to 50 amps! Right now, I'm currently getting 30 mph at a current limit of 40 amps just to conserve energy so I can get reasonable distance.)
Ypedal
100 TW
If it's not too hard to do.. try a Clyte 409 in a 20" at 72v 20 amps.. and the outrunner at 36v 40 amps. ( Same potential wattage, just " geared " differently )
Okay, I'll basically take the current gearing for the scooter and apply the 36 volts. Since I assume the 72volt battery has the same energy capacity (for fairly comparing) (Let's say you converted a 36V20Ah battery into a 72V10Ah battery), it would also have four times the internal resistance of the 36 volt battery (twice at less "parallel resistors"/half capacity, and twice as many "series resistors/2x the voltage).
For that, since both appear to be within the domain of a ping's discharge ratings, the 36V20ah would have an internal resistance ~ .095 mOhm and a 72V10ah would have .375 ohms.
Bike: C'lyte 409, 20 inch wheels, 72 volts limited at 20 amps, .375 ohms
Scooter - Stock gearing (4:1), 8 inch wheels, 36 volts at 40 amps, .095 ohms, 200kV Motor_resistance = .03 ohms
Okay, slight hiccup. My simulator doesn't have the 409's data as that ebikes.ca's simulator doesn't have that motor. So....we have a choice of the 408 and 4011. I'll do both.
For that, since both appear to be within the domain of a ping's discharge ratings, the 36V20ah would have an internal resistance ~ .095 mOhm and a 72V10ah would have .375 ohms.
Bike: C'lyte 409, 20 inch wheels, 72 volts limited at 20 amps, .375 ohms
Scooter - Stock gearing (4:1), 8 inch wheels, 36 volts at 40 amps, .095 ohms, 200kV Motor_resistance = .03 ohms
Okay, slight hiccup. My simulator doesn't have the 409's data as that ebikes.ca's simulator doesn't have that motor. So....we have a choice of the 408 and 4011. I'll do both.
So, it seems you see the same trend. Greater efficiency and power from the beginning with the geared system with the characteric "plateua", whereas the c'lytes tend to be peaky and optimally powerful and efficient only within a narrow higher-speed band.
As noted, this means better acceleration and more speed and efficiency when it comes to climbing hills.
The first example was one example that I did comparing my 407 bike to my current scooter, and my experiences definitely confirm the results contained on the graph. I mean, I'm certainly much faster climbing hills on the scooter than the hub motor bike - I was actually pretty amazed that electrics *could* be good at climbing hills (The hub motor kind of ruined my impression of electrics). :lol:
As noted, this means better acceleration and more speed and efficiency when it comes to climbing hills.
The first example was one example that I did comparing my 407 bike to my current scooter, and my experiences definitely confirm the results contained on the graph. I mean, I'm certainly much faster climbing hills on the scooter than the hub motor bike - I was actually pretty amazed that electrics *could* be good at climbing hills (The hub motor kind of ruined my impression of electrics). :lol:
WonderProfessor
100 W
- Joined
- Feb 20, 2009
- Messages
- 126
Uh, okay, I'll ask the dumb question. After these umpteen pages of posts, is there any particular reason that no one has brought up the use of mid-range motors? How are they that much different than the R/C motors? My guess is you're collectively going to say, "Cost and available kits."
Personally, I'm still agonizing over whether to go with a hub motor (Love that eZee!) or a mid-range (blackbirdbikes.com, ecospeed.com, stokemonkey on cleverchimp.com). I really like the idea of being able to use the bicycle's gearing with the motors but I think I really like the idea of being stealthy better. (We have one officer who patrols the area I ride through on my way to work who is really an a__hole!)
I just constructed a mock-up of two ping batteries -- a 48-volt, 15 amp and a 48-volt, 20 amp. Next step is to fill each with 16 pounds and 22 pounds, respectively, and ride around with each in my bike rack. Want to experiment with just how squirrelly each would feel. Would rather put just one big battery on the bike rack than two smaller batteries in parallel lower to the ground in panniers.
As always, many, many thanks for such a great resource here at endless-sphere.com.
Personally, I'm still agonizing over whether to go with a hub motor (Love that eZee!) or a mid-range (blackbirdbikes.com, ecospeed.com, stokemonkey on cleverchimp.com). I really like the idea of being able to use the bicycle's gearing with the motors but I think I really like the idea of being stealthy better. (We have one officer who patrols the area I ride through on my way to work who is really an a__hole!)
I just constructed a mock-up of two ping batteries -- a 48-volt, 15 amp and a 48-volt, 20 amp. Next step is to fill each with 16 pounds and 22 pounds, respectively, and ride around with each in my bike rack. Want to experiment with just how squirrelly each would feel. Would rather put just one big battery on the bike rack than two smaller batteries in parallel lower to the ground in panniers.
As always, many, many thanks for such a great resource here at endless-sphere.com.
I haven't thought of the mid-range motors. My impression of them is that they're not as small nor light and possibly not as efficient as an RC motor, but if you can gather some numbers (Mainly, the resistance of the motor and the Kv Kv being the RPM divided by the voltage you apply), I can chart their performance. One of the main advantages is that you have variable gearing, so you could, in theory, be even more efficient and powerful than the RC motor when, say, climbing a hill. The stoke monkey seems like it'd be much quieter than a cyclone (Which seriously gives external motors a bad name with noise), but I can't seem to find any video evidence of that.
So, if you're concerned about performance and you're mostly on flat land, a hub motor will probably do you fine. You might not have as excellent acceleration, but that shouldn't matter too much. If you're on hilly terrain, I definitely would suggest looking at some kind of external motor+gearing. There are geared hub motors out there, too, and they should have a somewhat similar performance profile it seems but they seem to cost a pretty penny and have their own seemingly unsatisfying power limits, even with the noisier steel gears.
Ok, I just looked at the stoke-monkey's cost. At >$1300, I'll cite that as a reason they haven't been seriously considered.
So, if you're concerned about performance and you're mostly on flat land, a hub motor will probably do you fine. You might not have as excellent acceleration, but that shouldn't matter too much. If you're on hilly terrain, I definitely would suggest looking at some kind of external motor+gearing. There are geared hub motors out there, too, and they should have a somewhat similar performance profile it seems but they seem to cost a pretty penny and have their own seemingly unsatisfying power limits, even with the noisier steel gears.
Ok, I just looked at the stoke-monkey's cost. At >$1300, I'll cite that as a reason they haven't been seriously considered.
Drunkskunk
100 GW
WonderProfessor said:
Cost and available kits
And quality
And power to weight ratios
Miles said:
So, I take it that's ~59 Kv?
Okay, so I didn't have gearing information but I used the optimization feature to maximize efficiency and came up with a gear ratio of 5 on flat-land with 26 inch wheels. Your wheels are probably smaller, but that's not going to affect the shape of the efficiency and power curve if efficiency is maximized.
Anyways, Mile's mid-range motor at 36 volts and 40 amps of pure ping power.
It looks like it similarly plateaus. If you have variable gearing, your also able to change the "how fast it's going to plateau rate" - it could be much more efficient and powerful than an RC motor at a given lower speed, if you want. It looks like this motor has more power going out than the HXT motor, which is probably due to the lower no-load current of this particular motor and that might be what I would expect from similarly quality mid-range motors. And, *surprise*, it's generally more efficient than an HXT.
Miles said:
Oh dear god! I love your bike's general set-up! I think I need to consider a "mid-range motor" with a low kV driving the cranks. Driving the cranks for some kind of variable gearing (using the hub gears) sounds really awesome as it seems to be a straight and simple way for getting the needed gear ratio(s) without messing with actual variable transmissions!! Now, I just have to wonder about the realistic power limits of a bicycle chain and hub gears... a bicycle chain's power limit seems kind of an open question and so do hub gears (Although the NuVinci said it could take upto 5 kW or so). And, also, I wonder if there are economic sources for a "mid range" motor - Stoke Monkey and EcoWheels does quite a bit to heavily dissuade me, even though the motor itself doesn't seem like it should be that costly compared to something like a hub motor's cost and hub motors seem like they should even be more expensive as they're "specialty" and are lower kV and generally seem to have more copper.
