QS 138 70H with Gearbox

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larsb   10 MW

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Re: QS 138 70H with Gearbox

Post by larsb » May 12 2021 3:08am

I’ve seen 7500 rpm max stated by qs for the 138 motor. Might be less depending on the gear setup

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Re: QS 138 70H with Gearbox

Post by Greggio_f » May 13 2021 2:13am

larsb wrote:
May 12 2021 3:08am
I’ve seen 7500 rpm max stated by qs for the 138 motor. Might be less depending on the gear setup
Thanks, Larsb. So what sort of ratio would you suggest for the standard QS 138 70H for a street bike with 12” wheels?

I’d prefer to avoid a huge rear sprocket - which is why I was looking at the gear reduction motor. Would something like 10 front 40 rear work for the standard motor? (It’s not that far off the QS motor kits, which are 1:4.78, I think).

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Re: QS 138 70H with Gearbox

Post by larsb » May 13 2021 2:39am

About 1:8 on 19” wheels gives wheel popping on my bike at 72V500Aphase so between 1:4 and 1:5 on 12” wheels should be good.

With 12” wheels i’d guess you’re on a bike that pops more easily so closer to 1:4 would be my starting point

Depends on what you’re after, speed or wheelies :wink:

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Re: QS 138 70H with Gearbox

Post by niels_ » May 16 2021 5:45pm

does anyone use a ND72490 with this motor?
i can't find anything about this controller anywhere.
https://nl.aliexpress.com/i/1005001971351434.html

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Ianhill   100 MW

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Re: QS 138 70H with Gearbox

Post by Ianhill » May 27 2021 1:05pm

Just ordered the qs138 70h spined shaft none geared motor i thought they used a 13mm kart shaft but from reading a page back that does not seem to be the case its ISO 14.

Ive gone and ordered the motor now bastardio so its case of what usually happens in life.

I wanted 219 chain i can get sprockets 9-11t front and 65-104t rear for a wide range of choice but looks like my motor sprockets not gonna fit, wondering if i can find someone that can make it fit mod my shaft but im not done with the idea yet my kuberg needs this.
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Re: QS 138 70H with Gearbox

Post by Ianhill » Jun 01 2021 1:32am

niels_ wrote:
May 16 2021 5:45pm
does anyone use a ND72490 with this motor?
i can't find anything about this controller anywhere.
https://nl.aliexpress.com/i/1005001971351434.html
Ive had a look at those controller they are interesting theres a nd96800 model that looks ripe to push the 138 90h fair way up the rev band.

The nd72490 looks to use a smaller footprint so its heatsink area is fairly small and its total amount of fets must be in the 24 range, one good point is the spec figures on all the controllers seem legitimate enough so id say its a good call for maxing out on a budget but as with all these import stuff comes risk but so far ive seen on the good side of it.

Id like to use 2 qs 138 90h motors on a kart with the nd96800 controllers but thats alot of cash to save up but the sound of 50kw kart thats not an overheating mess appeals to me dual motor setup would really make for a mutant machine only wise crazy fools will appreciate proper widow maker.
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Re: QS 138 70H with Gearbox

Post by EVOXY6768 » Jun 09 2021 6:13pm

Has anyone got this set up and running in there conversions yet ? Haven't seen many video's or complete builds beside the one posted here on endless sphere and what controllers is everyone using, QS suggest Votel EM 200
Considering this in my next build in a 125 motor cross bike.
Cheers

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Re: QS 138 70H with Gearbox

Post by jhoexp » Jun 10 2021 5:39am

EVOXY6768 wrote:
Jun 09 2021 6:13pm
Has anyone got this set up and running in there conversions yet ? Haven't seen many video's or complete builds beside the one posted here on endless sphere and what controllers is everyone using, QS suggest Votel EM 200
Considering this in my next build in a 125 motor cross bike.
Cheers
I just completed my mounts and placed the motor inside the frame, but I am still too busy to complete the bike (I will do in the summer, as originally planned). I will start my build thread soon anyway (Husqy TE 250 + qs138v3 + sevcon gen4 size4).

Zalo moto completed his CR with the V3 in it, but there isn't much info, besides this video: https://www.youtube.com/watch?v=zhzN1Eg4tSk

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Re: QS 138 70H with Gearbox

Post by Elettro » Jun 16 2021 6:20am

jhoexp wrote:
Jun 10 2021 5:39am

Has anyone got this set up and running in there conversions yet ? Haven't seen many video's or complete builds beside the one posted here on endless sphere and what controllers is everyone using, QS suggest Votel EM 200
Considering this in my next build in a 125 motor cross bike.
Cheers
I just completed my mounts and placed the motor inside the frame, but I am still too busy to complete the bike (I will do in the summer, as originally planned). I will start my build thread soon anyway (Husqy TE 250 + qs138v3 + sevcon gen4 size4).

Zalo moto completed his CR with the V3 in it, but there isn't much info, besides this video: https://www.youtube.com/watch?v=zhzN1Eg4tSk
[/quote]

I will follow you very willingly.
Here in Italy (Acqui Terme :wink: ) it is very difficult to find people who carry out these works but,Although I don't speak English and my knowledge is not the best, I am determined to convert my Honda CRF 450 into something that can climb
Honda CRF 450 Being Edited

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Re: QS 138 70H with Gearbox

Post by Ianhill » Jun 18 2021 9:22am

Whats the delivery time about ? Sure mines gone for a walk.
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Re: QS 138 70H with Gearbox

Post by larsb » Jul 05 2021 4:06pm

jhoexp wrote:
Mar 15 2021 6:52pm
john61ct wrote:
Mar 15 2021 5:18pm
OK how about "better" for long steep hills & heavy loads at low speeds. Very slow top speeds.
Yes, exactly. It sure depends mostly on what use you want to make of it.
More mass means slower to overheat in that context?
I think you can say so, probably not much of a problem in most use cases.
Or are the magnets a small component of overall mass? When people talk about iron, and "moar copper", how do magnets fit in?
In this kind of IPM motors, magnet are embedded in the rotor laminations. Copper wire is in stator windings. How they influence performance is so complex that you can't really say much just from the lenght of the motor. I think you can probably assume that the longer motor will have higher torque and turn slower.
Shouldn’t answer when you don’t know..

Longer magnet motor will also have larger stator and airgap area. You will get roughly proportional larger power out of the motor.
2x the stator and magnets, 2x the motor.
Motor will not be slower just because it’s got longer magnets, the peak rpm depends on winding, voltage, stator and magnet materials and structural design. The winding is not the same for the 90H motor as for the 70H.

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Re: QS 138 70H with Gearbox

Post by jhoexp » Jul 05 2021 4:25pm

larsb wrote:
Jul 05 2021 4:06pm
Shouldn’t answer when you don’t know..
Shouln't reply when you can't read and understand what's already written.
Longer magnet motor will also have larger stator and airgap area. You will get roughly proportional larger power out of the motor.
2x the stator and magnets, 2x the motor.
Motor will not be slower just because it’s got longer magnets, the peak rpm depends on winding, voltage, stator and magnet materials and structural design. The winding is not the same for the 90H motor as for the 70H.
As I said, there is so much more that influence motor performance... but still with qs138 90H and 70H, with everything else staying the same, the first have more torque and turns a little slower than the smaller one.

So you just stated the obvious and nothing more than what already said, but being a dick. Well done, dumbass. :thumb:

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Re: QS 138 70H with Gearbox

Post by larsb » Jul 06 2021 12:19am

jhoexp wrote:
Jul 05 2021 4:25pm
As I said, there is so much more that influence motor performance... but still with qs138 90H and 70H, with everything else staying the same, the first have more torque and turns a little slower than the smaller one.

So you just stated the obvious and nothing more than what already said, but being a dick. Well done, dumbass. :thumb:
I guess it hurts to be wrong :wink:
The original question was for 70H vs 90H motor. Most things are indeed the same between these so why muddy the waters with “complex things”?
When i checked the QS data for the kV for 70H and 90H they have close to the same kV. Why do you say it’s slower? Have you measured them?

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Re: QS 138 70H with Gearbox

Post by john61ct » Jul 06 2021 1:21am

Really would be better for everyone if the personal attacks, we're all just trying to learn together and share with each other

that sort of negativity only hurts this great community.

I've been guilty of engaging at that level myself, but learned best to not reference idiots directly as people

not contradict their mistakes so directly

just lay out what you believe to be the truth best you can, and let the rest just lie.

OK, now my noobish question, for anyone:

The 70H vs 90H is just the width of the magnet, right?

Why would there necessarily be any relationship between that and the winding / kV factor???

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Re: QS 138 70H with Gearbox

Post by larsb » Jul 06 2021 3:29am

There is an optimum magnet width for the stator width so normally it would not be just the magnets that are longer.

With a longer magnet and stator (all else being the same) you get more field/force/torque produced per current so kV will be lower if the winding isn’t changed.

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Re: QS 138 70H with Gearbox

Post by jhoexp » Jul 06 2021 4:14am

larsb wrote:
Jul 06 2021 12:19am
I guess it hurts to be wrong :wink:
I bet you know well the feeling, right? :D
Go read the original questions from john61ct, you :twisted: !
The original question was for 70H vs 90H motor. Most things are indeed the same between these so why muddy the waters with “complex things”?
When i checked the QS data for the kV for 70H and 90H they have close to the same kV. Why do you say it’s slower? Have you measured them?
No, the original question was generic and about wich is "better", with a lot of "" to clarify things, etc... if again you just cared to READ!
Anyway, my answer was necessarely vague because there is so much more to say about this than just magnet lenght, but still right overall and in regard to the QS138 90H vs 70H, with the 90H being more "torquey" and a little slower because of the lower KV and higher inertia. Yes I have both motor (the 70H in the v3 edition).

That's why I answered. And that's why you shouldn't have, expecially in that stupid way.

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Re: QS 138 70H with Gearbox

Post by larsb » Jul 06 2021 5:12am

0AEAACC4-50D0-4C7E-BA17-398358BEAD0F.jpeg
0AEAACC4-50D0-4C7E-BA17-398358BEAD0F.jpeg (58.04 KiB) Viewed 989 times
Here we go from 90H vs 70H and then the magnet question. Since we’re discussing a really similar motor with increased length it’s not complex. there’s no point to compare two motors with different diameters or such difference and ask what is the best magnet height.

So what’s the kV for 70H and 90H in comparison? This data will help a lot of folks with their builds.

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Re: QS 138 70H with Gearbox

Post by jhoexp » Jul 21 2021 3:28am

larsb wrote:
Jul 06 2021 5:12am
Here we go from 90H vs 70H and then the magnet question. Since we’re discussing a really similar motor with increased length it’s not complex. there’s no point to compare two motors with different diameters or such difference and ask what is the best magnet height.

So what’s the kV for 70H and 90H in comparison? This data will help a lot of folks with their builds.
John asked if "higher" (he was confused by the "H", while it meant "longer") magnet was "better", more powerfull. That's generic and not that simple even with similar motors with different rotors. And yes, that influences the KV as you seem to understand now (what happened?). Also rotational inertia is different. KV is around 55-57, I dont have the dcf here and can't check now.

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Re: QS 138 70H with Gearbox

Post by larsb » Jul 21 2021 9:45am

Seem to understand? You did not understand: i said there was a change in the winding to keep the kV the same or it would have been roughly 60*70/90, so 47 for the 90H motor.

I just asked to prove you don’t know what you’re talking about. Give a man enough rope..
Last edited by larsb on Jul 21 2021 10:36am, edited 1 time in total.

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Re: QS 138 70H with Gearbox

Post by larsb » Jul 21 2021 9:52am

Next thing i’ll ask is how relative torque vs inertia changes when a motor is made longer.. :mrgreen:

Does it change..really?

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Re: QS 138 70H with Gearbox

Post by jhoexp » Jul 21 2021 12:45pm

larsb wrote:
Jul 21 2021 9:45am
Seem to understand? You did not understand: i said there was a change in the winding to keep the kV the same or it would have been roughly 60*70/90, so 47 for the 90H motor.

I just asked to prove you don’t know what you’re talking about. Give a man enough rope..
No, it's you, man. You seriously need some vacation, because you can't read and undertand even your posts. You have no clue about what KV is and how this change, what you said is completly wrong. Stop wasting time here and go back to school.

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Re: QS 138 70H with Gearbox

Post by jhoexp » Jul 21 2021 12:47pm

larsb wrote:
Jul 21 2021 9:52am
Next thing i’ll ask is how relative torque vs inertia changes when a motor is made longer.. :mrgreen:

Does it change..really?
Yes really!! Lars, this is not your thing... you have limited undestanding of how complex this is and there is much more to it. Also the point was not relative torque vs inertia, but max rpm. You continue to make stuff up that just makes no sense. Stop polluting this thread. The qs138 90H is more torquey and turns a little slower than the 70H, given the same battery/controller/tuning is used. This statement is absolutely true, many have tested them (like me) and can confirm.

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Re: QS 138 70H with Gearbox

Post by spinningmagnets » Jul 21 2021 1:07pm

Lengthening a stator (both are 138mm.diameter, 70mm length vs 90mm) will make the wire runs in the coils a bit longer, increasing resistance, and also making the kV lower/slower.

Same number of turns, different kV.

If you double the length of the motor (diameter remains the same) you do increase its torque potential...

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Re: QS 138 70H with Gearbox

Post by j bjork » Jul 21 2021 1:29pm

I wish you could both stop fighting about this, we are all learning from each other here..

From what I understand you are supposed to determine kv from back emf or how it was.
But when I only tested no load rpm to get close I got about 60 on the 70h from what I remember.
How is your kv for the 90h determined jhoexp?
And what have you got for the 70h?

I guess if the 90h is one turn less (would that be likely?) it should mean less copper loss with more strands even if they are longer, or what do you you guys think?

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Re: QS 138 70H with Gearbox

Post by larsb » Jul 21 2021 1:53pm

I can’t really be bothered to check it but i vaguely recall 16mm2 phase wires stated for the 70H and 20mm2 for the 90H. That would *ehrm* indicate a winding change where 60*70/90*(20/16) gives kV 58 for the 90H as compared to the 60kV for the 70H calculated with some basic assumptions behind.

There you go. What you could think about is the motor as a slice of stator and rotor. Make this slice twice as wide and the torque per amp will be double (and kV halved). How do you then get same kV? Wind less turns.
(The inertia per stator length and torque capability per stator length is naturally kept the same.)

How will the motor be a higher torque motor if the kV - and torque per amp is the same then? It needs more phase current to produce more torque and it can also take more phase current due to the changed wiring.

The bottom line is also that if your controller is maxed out with the 70H you won’t get more out of your drive with the 90H. Counterintuitive.

@jhoexp: I’m on vacation, thank you, just down from some mountain running. Please forgive me if i took some wrong turns :D in this long post. I am sweaty and tired.

@jbjork: Sorry. I was a bit cranky before. Don’t like to be called wrong when i’m not. What would be more fun is if jhoexp opens his motor, proves that the 90H is not just a longer stator version of the 70H and proves my assumptions were wrong. That would bring some more understanding than this bickering.
Last edited by larsb on Jul 21 2021 3:29pm, edited 3 times in total.

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