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- Feb 15, 2013
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- 1,903
a mid mounted hub motor runs at much lower rpm than bldc .. thus lower decibel noise level.. but yes add sine wave and belt for even lower noise levels..
surron bicycle with qs205 middrive
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- Start date
j bjork
100 kW
I like the torque of the 4t ,now i have a 14tooth in the front and a 25 rear so its arround 1.8 on 1. Maybe next year i will rebuild it then i would use a 5t with a 30s battery for even more torquej bjork said:
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What I mean is, you can get the same torque but higher rpm from a "faster" wind. Then you can have more reduction to get the same speed with more torque
But you will need a better controller.
To go to 30s is also an option of course, but no need to change to 5T. Just more reduction.. Maby even go 3T and 30s, but there will be a limit when the losses get higher with higher rpm. LarsB knows a lot more about that then me.
Maby look at the nucular 24 fet? I will get one of those for my qs 205 50H 4T, but I use it as a hubmotor. Seems like a nice controller, but limited to 90V, so no 30s there..
Do you usually ride nice tracks like that?
I usually ride a bit more demanding tracks, with rocks and roots and stuff. I would like a middrive too, I need a new rear rim now..
The few times I ride on the street I would like a 3T, for more power at higher speeds.
My build if you want to see: https://endless-sphere.com/forums/viewtopic.php?f=6&t=98723&start=25
The noice from a standart surron comes from the controller ,chain and high rpm-wining of the motor, i use sinus controller and low rpm hubmotor, first transmission is by 2 big 25 tooth sprockets with minor chainnoice, second is 14 to 25 with good lubed chain the noice is almost negligible.Tommm said:
j bjork said:I like the torque of the 4t ,now i have a 14tooth in the front and a 25 rear so its arround 1.8 on 1. Maybe next year i will rebuild it then i would use a 5t with a 30s battery for even more torquej bjork said:
What I mean is, you can get the same torque but higher rpm from a "faster" wind. Then you can have more reduction to get the same speed with more torque
But you will need a better controller.
To go to 30s is also an option of course, but no need to change to 5T. Just more reduction.. Maby even go 3T and 30s, but there will be a limit when the losses get higher with higher rpm. LarsB knows a lot more about that then me.
Maby look at the nucular 24 fet? I will get one of those for my qs 205 50H 4T, but I use it as a hubmotor. Seems like a nice controller, but limited to 90V, so no 30s there..
Do you usually ride nice tracks like that?
I usually ride a bit more demanding tracks, with rocks and roots and stuff. I would like a middrive too, I need a new rear rim now..
The few times I ride on the street I would like a 3T, for more power at higher speeds.
My build if you want to see: https://endless-sphere.com/forums/viewtopic.php?f=6&t=98723&start=25
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I know fasterwinding can have more reduction but lower windings can take more amp-abuse and have less rpm (noice)
For the controller part i also like the 24fet nucular but i am more familiar with sabvoton so the next will be the 96120.
j bjork
100 kW
You sure have some nice, long tracks where you live
I have´nt heard that before, that the higher turn counts can take more abuse. So you mean a 300 amp rated 4T will heat up less at 450A than a 400 amp rated 3T at 600A?
Is that something you have confirmed yourself, or where is that info from?
I have´nt heard that before, that the higher turn counts can take more abuse. So you mean a 300 amp rated 4T will heat up less at 450A than a 400 amp rated 3T at 600A?
Is that something you have confirmed yourself, or where is that info from?
I don't have confirmed it myself, but that was what i understand reading here on esj bjork said:You sure have some nice, long tracks where you live
I have´nt heard that before, that the higher turn counts can take more abuse. So you mean a 300 amp rated 4T will heat up less at 450A than a 400 amp rated 3T at 600A?
Is that something you have confirmed yourself, or where is that info from?
j bjork
100 kW
Alright, it would be interesting to see if someone with more knowledge would like to comment on that.
It sounds wrong to me, I think all the windings have the same potential if you can feed them the same wattage.(if they have the same copper fill) It just means you will need higher voltage for the higher turn counts, but lower amps.
As I understand it, as the lower turn counts can take more amps, they will give more performance if you go for higher voltage and the higher amps they can handle. Up to a point where the rpms get to high.
It sounds wrong to me, I think all the windings have the same potential if you can feed them the same wattage.(if they have the same copper fill) It just means you will need higher voltage for the higher turn counts, but lower amps.
As I understand it, as the lower turn counts can take more amps, they will give more performance if you go for higher voltage and the higher amps they can handle. Up to a point where the rpms get to high.
larsb
1 MW
You got it backwards there since the low turn motors don't need high voltage to go fast. They also create proportionally less torque per amp.
Either go 1 turn motor with 2 amp * 1 volt input or 2 turn motor with 1 amp * 2 volt input. They're the same torque and power out.
What is a bit unlogical is that same copper fill has same resistance losses per torque from motor. Whatever turn count you got. So no added high benefit there from low or high turn count, it's just a balance of volt¤t. But higher amps equals high resistance losses in all the system apart from motor.
Where's the downside of high volts then? It can kill you. Controllers get more expensive. Todays mosfets (still, as far as i know..) are less efficient with higher resistance when you go over 100V.
A side note on turn counts that support the high turn "torque" motor in a way:
I haven't had more than one controller that really maxed the current at zero rpm though.. this means that a high turn motor probably is stronger on really low rpm no matter if it's theoretically the same as a low turn motor in max torque because of the "common" controller limitations!
Bleh, not true you say?
Kelly, adaptto, APT, Votol controllers called and beg to differ. It's subjective since not on the dyno but the only controller i've had that i've found powerful at low rpm was a crappy infineon controller from Lyen. Full blast on low rpm with poor current control.. But it also broke quite quickly
This thread is a good one:
https://endless-sphere.com/forums/viewtopic.php?f=2&t=64907&hilit=MYTH+speed+torque
j bjork
100 kW
What I mean is:
If you have a given voltage and you can feed the motor enough amps, both will have the same torque but the lower turn count will have more rpm. That means with more reduction you will have more torque at the wheel.
Well, just give the higher turn count motor more voltage? Sure, but you can give the lower turn count motor more voltage too. Then it would still be ahead. But of course it needs more amps for the same torque output.
It really is about how much wattage you are able to put in the motor, U x I. (Yea, and how much is lost to heat..)
Up to a point where iron losses in the motor is getting too high with the higher rpm. I don´t know if a 3T will work with 30s for example, but if it does I think you would get more power from that than a 4T or 5T. If you can give it enough amps that is. If you are limited in amps then 4 or 5T might be better. But how much amps is "enough" is also a question..
I have read that tread before, but it may be time to do it again.
If you have a given voltage and you can feed the motor enough amps, both will have the same torque but the lower turn count will have more rpm. That means with more reduction you will have more torque at the wheel.
Well, just give the higher turn count motor more voltage? Sure, but you can give the lower turn count motor more voltage too. Then it would still be ahead. But of course it needs more amps for the same torque output.
It really is about how much wattage you are able to put in the motor, U x I. (Yea, and how much is lost to heat..)
Up to a point where iron losses in the motor is getting too high with the higher rpm. I don´t know if a 3T will work with 30s for example, but if it does I think you would get more power from that than a 4T or 5T. If you can give it enough amps that is. If you are limited in amps then 4 or 5T might be better. But how much amps is "enough" is also a question..
I have read that tread before, but it may be time to do it again.
larsb
1 MW
Bottom line is that every motor needs to be run at max rpm (and max torque) to get max power.
No matter if you achieve it through high kV/low voltage or low kV/high voltage.
High rpms alone can burn a motor - at no load. The eddy losses will eventually get that high so there's always an rpm limit. Or motor explodes due to the centrifugal forces and heat combined.
An example:
Run a motor at 50% of the rpm, it's half a motor.. So when the RC motor you want to buy is said to produce 10kW and has a max RPM of 25K then that power is at 25krpm. Max torque can be derived from P=M*n/9.55 --> M=9,55*P/n --> 3.82 Nm. Not much..
But 25krpm can be geared down 25 times or so to get 100Nm torque at the wheel at a comfortable 1000rpms.. Also not so much
If you run it at 12.5krpm max then you can gear same motor 12.5 times to get a 1000 rpm. Now you only get about 50Nm out of it at the rpm you wanted.
But.. The downside for EV application is that RC motors still have a lot of losses at 25krpm due to eddy currents. It works on propeller motors since at 10kW output there's effectively a 10kW cooling fan blowing on the motor.
In a traction motor you'd get a lot less possible output before overheating, i've heard less than 10krpm in some cases. So the 10kW motor is then only 10x10/25= 4kW capable unless it's only a short burst.
But all of you knew this already :wink:
No matter if you achieve it through high kV/low voltage or low kV/high voltage.
I get what you mean, wouldn't call it "ahead" though as that would mean that low turn motor is always better. kV is not a merit figure, it's only a constant to adjust and match with the rest of your system.
High rpms alone can burn a motor - at no load. The eddy losses will eventually get that high so there's always an rpm limit. Or motor explodes due to the centrifugal forces and heat combined.
An example:
Run a motor at 50% of the rpm, it's half a motor.. So when the RC motor you want to buy is said to produce 10kW and has a max RPM of 25K then that power is at 25krpm. Max torque can be derived from P=M*n/9.55 --> M=9,55*P/n --> 3.82 Nm. Not much..
But 25krpm can be geared down 25 times or so to get 100Nm torque at the wheel at a comfortable 1000rpms.. Also not so much
If you run it at 12.5krpm max then you can gear same motor 12.5 times to get a 1000 rpm. Now you only get about 50Nm out of it at the rpm you wanted.
But.. The downside for EV application is that RC motors still have a lot of losses at 25krpm due to eddy currents. It works on propeller motors since at 10kW output there's effectively a 10kW cooling fan blowing on the motor.
In a traction motor you'd get a lot less possible output before overheating, i've heard less than 10krpm in some cases. So the 10kW motor is then only 10x10/25= 4kW capable unless it's only a short burst.
But all of you knew this already
:wink:now i have a 4t and 20s battery and thats fine it go's like a spear with full battery to 50km/u before fieldwakening qicks in.
With a 5t and 30s it will go arround 70km/u before fieldwakening. And a 5t has more startingtorque( i believe).A 3t motor would make arround 1700rpm at 126 volt, thats, to much for a hub not? I did choose the hub for the low rpm( low noice), otherwise i had taken the qs 3000w middrive like on my senda.
With a 5t and 30s it will go arround 70km/u before fieldwakening. And a 5t has more startingtorque( i believe).A 3t motor would make arround 1700rpm at 126 volt, thats, to much for a hub not? I did choose the hub for the low rpm( low noice), otherwise i had taken the qs 3000w middrive like on my senda.
j bjork
100 kW
I think you will get more starting torque if you keep your 4T and go 30s and more reduction. But you are limited in amp with your controller, so I am not sure.
I want to try the 96120 sabvoton unlocked with a 30s 7p samsung 40T, so it wil be good for 250 battery-amps.j bjork said:
About the 4t motor i don't think the gearing will give me that much more, i changed from 17 in front to 14 and cannot say the torque increased much. Also calculated diffrence in gearing between a 4t and a 5t motor, for a 5t motor it would be 1.78 to 1 ,for a 4t motor that would be 2.2 to 1.
larsb
1 MW
17t to 14t is 20% more torque :wink: so i guess to satisfy your torque needs it has to be at least 50%?
qs kv table for the 205 goes to 1200 rpm, thats still lower than 20 000 erpm and not a lot. I'd guess you can go to 30s 3t and 1700rpm and downgear it
what controller would you use though? isn't 30s/126V too much for a 96v controller?
You could ask QS what they think about it. I can't see bearings getting issues or structural issues, maybe balancing.
qs kv table for the 205 goes to 1200 rpm, thats still lower than 20 000 erpm and not a lot. I'd guess you can go to 30s 3t and 1700rpm and downgear it
what controller would you use though? isn't 30s/126V too much for a 96v controller?
You could ask QS what they think about it. I can't see bearings getting issues or structural issues, maybe balancing.
I prefer to stay around 1000 rpmlarsb said:qs kv table for the 205 goes to 1200 rpm, thats still lower than 20 000 erpm and not a lot. I'd guess you can go to 30s 3t and 1700rpm and downgear it
what controller would you use though?
You could ask QS what they think about it. I can't see bearings getting issues or structural issues, maybe balancing.
For the controller i will use the 96120 sabvoton unlocked can do 300batt and 500 phase@maximum, i go for 250batt and 400 phase thats enough j bjork
100 kW
For startup torque you need phase amps, not battery amps. From what I saw about the sabvoton 96120 it has 300 phase amps. From what I remember, that is about what is recommended for the 4T. I don´t know how much more it can take, but I guess at 300A the 5T will give more torque but lower efficiency.
Thats why I think you will get higher torque from the 4T with more reduction (or downgear, I dont know the right words in English)
From what I remember the 3T is recommended with 400A, If you had a better controller that could do maybe 500 phase A I think that would be the way to go.
But as you already have the 4T, and want to go 5T, I would be very interested to see the result if you tried both with what your controller can give, and gearing so you get the same wheel speed
Edit, ok your controller can give 500 phase amps.. Alright, well I guess you have better chances of the controller to live longer your way :lol:
Thats why I think you will get higher torque from the 4T with more reduction (or downgear, I dont know the right words in English)
From what I remember the 3T is recommended with 400A, If you had a better controller that could do maybe 500 phase A I think that would be the way to go.
But as you already have the 4T, and want to go 5T, I would be very interested to see the result if you tried both with what your controller can give, and gearing so you get the same wheel speed
Edit, ok your controller can give 500 phase amps.. Alright, well I guess you have better chances of the controller to live longer your way :lol:
larsb
1 MW
says 193Nm peak at QS if we're talking the 50H
kV for full torque is 9,55*A/T so to match a 300A controller needed kV is <15; 4T motor (aaalmost 3T)
kV for 500A controller is <25; 3T with margin
kV for full torque is 9,55*A/T so to match a 300A controller needed kV is <15; 4T motor (aaalmost 3T)
kV for 500A controller is <25; 3T with margin
j bjork
100 kW
Yes, but if you had the 3T the lower inductance would put more stress on the controller.
From what I have read, a sabvoton is not the best controller for startup torque. But better then kelly. But still with soft start and speed throttle as I remember it.
From what I have read, a sabvoton is not the best controller for startup torque. But better then kelly. But still with soft start and speed throttle as I remember it.
j bjork
100 kW
larsb said:kV for full torque is 9,55*A/T so kV to match a 300A controller is 15; 4T motor (aaalmost 3T) and kV for 500A controller is 25; 3T with margin
Now it is getting interesting, can you explain the calculation a little more?
larsb
1 MW
Don't know about inductance risk. hasn't it got 32slots? and massive stator? based on their figures for the other turn counts it would be 180uh for a three turn.
That's not small.
That's not small.
larsb
1 MW
j bjork said:larsb said:kV for full torque is 9,55*A/T so kV to match a 300A controller is 15; 4T motor (aaalmost 3T) and kV for 500A controller is 25; 3T with margin
Now it is getting interesting, can you explain the calculation a little more?
No, it's top secret.
torque constant =9.55/kV
torque= torque constant*A
move them around, given motor torque in this case is 193 Nm and calculating two different controllers with 300A or 500A output
It assumes linear relation torque vs amps all up to max torque which is not really true. But it's an estimation, not a guesstimation :wink:
j bjork
100 kW
It says 106uh in the chart for 3Tlarsb said:
http://www.cnqsmotor.com/en/article_read/QS%20QSMOTOR%20350W%20-%203000%20Watt%20Peak%2014kW%20205%2050H%20V3%20Brushless%20DC%20electric%20bike%20ebike%20hub%20motor/536.html
larsb
1 MW
:thumb: this table was complete.. i had to interpolate the one i had without success
Electric time constant (which determines the rise time for the current) for the 3T is 6.4mS. thats still not really small. As a reference the QS3000w mid motor has 1.4mS - 5 times less. So it should not be hard on controllers.
The hub motors are normally easy to drive vs any of the mid drives, not to mention compared to RC drives.
Electric time constant (which determines the rise time for the current) for the 3T is 6.4mS. thats still not really small. As a reference the QS3000w mid motor has 1.4mS - 5 times less. So it should not be hard on controllers.
The hub motors are normally easy to drive vs any of the mid drives, not to mention compared to RC drives.
John1deere
10 W
- Joined
- Jul 9, 2018
- Messages
- 75
taught i would chime in since i have a 3t and similar setup (vector vortex) i currently use the kelly 8080h 700 amps controller.
3t has thicker winding making it capable of handling more phase amps so like someone said before the optimal setup would be bigger rear sprocket or smaller front and a 3t for maximum torque. im currently maxed out at 400 battery amps and 700 phase amps on my 3t qs205 and it pulls ridiculously hard. im sure im losing a lot of power in heat but so far it never over heated and i dont even have statorade so i guess its not that bad.
3t has thicker winding making it capable of handling more phase amps so like someone said before the optimal setup would be bigger rear sprocket or smaller front and a 3t for maximum torque. im currently maxed out at 400 battery amps and 700 phase amps on my 3t qs205 and it pulls ridiculously hard. im sure im losing a lot of power in heat but so far it never over heated and i dont even have statorade so i guess its not that bad.
