QS 138 70H with Gearbox

[j bjork]

*ehrm* indicate a winding change where 60*70/90*(20/16) gives kV 58 for the 90H with some basic assumptions behind.

I get all the other things you said, but not really this calculation.
I can do the calculation and get the result, 58,3333.

So 60x70 is 60kv for the 70h? And then divided by 90 for 90h and 20/16 for the difference in copper dia?
So I just feel dumb, and I only did math A

 

[larsb]

Yes, you’re correct, it’s based on the assumption of kV60 for the 70H, then assumption that kV is inversely proportional to stator length to 60*(70/90) which gives kv=47 for a 90H with same winding as the 70H.

Then an assumption that both motors have the same copper fill which means that the possible number of turns is inversely proportional to the phase wire area. Any good motor is wound to the maximum possible copper fill so this assumption is quite safe.

The assumption can very simplified be expressed that:
1turn x 100mm2 and 100turns x 1mm2 will make the same copper fill but a 100x difference in kV.

Why i don’t think they did anything else than make the stator and magnets longer is that for each stator width there’s an optimum magnet width. For each magnet strength (airgap field) and slot count there’s an optimum lamination design (this assumption is going out on a limb a bit) and i assume they use the same laminations for both motors also since the lamination stamping is tooled already —>
Same magnets spec, just longer.
Same laminations, just longer stack

If QS was aiming for the same kV with the 90H motor as the 70H it’s reasonable since then it will reach the same rpm on same voltage with the new motor.

I wonder if they use the new fardriver controllers in combination with the 90H to use the full power potential? This would be interesting:

 

[DEHiCKA]

I wonder why they changed output shaft from 20mm to 17mm splines while torque almost doubled? Bearing clearance?
Considering 20mm splines does not hold well on non geared QD 138 with sloppy fit chinese sprockets, 17 mm does not look good.

 

[larsb]

no sprocket will last long term with sloppy fit due to the grinding created so the sprocket slop is the main issue and not the spline size.

 

[Elektrosherpa]

That's it.
And I am really asking myself why QS is not able to provide properly fitting sprockets.
Probably because we dummies buy their stuff anyway...

 

[DEHiCKA]

no sprocket will last long term with sloppy fit due to the grinding created so the sprocket slop is the main issue and not the spline size.

Sure, but it will get even worse with less contact point of a smaller spline.
And if I want maximum reduction I have only seen chinese 9T-11T #428 or #520 with this spline pattern.

The output shaft is 18mm on the inner side and 20mm on the outer. Bearings on the output shaft are 6203 and 6004 made by C&U. They look decent, but it's an easy upgrade if needed....

I am thinking about making a custom shaft.
Is it possible to disassemble the gear from the output shaft and reassemble on the new one without damage?

 

[Overclocker]

wait, so there aren't any tight-fitting 428 sprockets for this motor yet???

 

[DEHiCKA]

I believe any brand name sprockets with proper 17-14/4mm splines will be good fit, but cannot confirm since I did not received the motor yet.
The smallest sprockets I have found online that should fit on paper are 12T for #428 and 11T for #420. If anyone aware of high quality small #428, please let me know.

 

[Overclocker]

problem is even a "good" fit isn't good enough. it has to be so tight that you have to heat up the sprocket first then tap it in w/ a hammer.

even the smallest amount of movement gets larger the more you use it then pretty soon the shaft is so screwed up that the only way is to weld the sprocket

btw i noticed you have the same qs120 motor based on your sig. how's the shaft holding up?

 

[Elektrosherpa]

IMG_20210620_111831 (1).jpg

Welded sprocket... hmm.....and what will you do, when the sprocket is worn out?

 

[DEHiCKA]

btw i noticed you have the same qs120 motor based on your sig. how's the shaft holding up?

For trials use I did not even bother with the original spline. Luckily 20-16 spline have just enough room for a 5/8" bore.
So I have rebuild it right away for B Type #420 case hardened sprockets.
Worn two 8T sprockets in 6 month (I train trials almost every day). Thanks to much thicker body and set screws the shaft is still looks good.

QS120 H70 have around 40-45Nm stall torque, 37kV and with huge 8/62 reduction I am maxing it out to 120C windings temp on trials sessions (mostly RW jumps from zero speed to zero speed with ~10-12kW peaks)

 

[Stevebequik]

I think the main issues is the width of engagement with the splines.
Both shafts have have driving surface of 6 splines x 1.5mm high x sprocket width.
Those that are putting 520 sprockets on these, I think will run into problems as the width is only 6mm vs 7.2mm for a 428 sprocket.
I plan on modifying a 530 plate wheel sprocket( dirt cheap as a 10b or #50 industrial sprocket)
This way I have a width of 9.17mm.
Most gas 520 sprockets have a flange to increase their width.

 

[john61ct]

From my notes, not sure from whom?

loose spline issue - buy with belt axle use this adapter to fit a chain

14T 14 tooth 428 chain Sprocket Adapter for QS138 QS120 Mid Drive Motor
https://m.aliexpress.com/item/1005001456567871.html

 

[Overclocker]

Welded sprocket... hmm.....and what will you do, when the sprocket is worn out?

grind off the 6 little tack welds. should come off w/ a 3-jaw puller. i could probably do this 10 times without screwing up the shaft too much :lol:

 

[Overclocker]

For trials use I did not even bother with the original spline. Luckily 20-16 spline have just enough room for a 5/8" bore.
So I have rebuild it right away for B Type #420 case hardened sprockets.
Worn two 8T sprockets in 6 month (I train trials almost every day). Thanks to much thicker body and set screws the shaft is still looks good.

QS120 H70 have around 40-45Nm stall torque, 37kV and with huge 8/62 reduction I am maxing it out to 120C windings temp on trials sessions (mostly RW jumps from zero speed to zero speed with ~10-12kW peaks)

interesting... so if all else fails i still got a backup plan. i just need to check if there are 428 type-b sprockets. in your case #420 is the same sprocket as #41 so there's definitely "industrial" type-b sprockets. unfortunately 428 isn't exactly the same as #40

got a pic of your modded shaft?

as for the qs138 v3 w/ gearbox the shaft is a lot thinner so that solution might not work. but if you can make a modded sprocket that'll interface w/ the entire width of the shaft splines then maybe... but then the problem is sprocket retention, that's why i ended up welding my sprocket :lol:

 

[Jordan325ic]

Haha... I've welded a sprocket onto a shaft once, on an '86 DR600. Of course I was stuck in the middle of the Gobi desert at the time.

For anybody who doesn't plan on welding the shaft I did get a set of 520 sprockets made and I have some left over.
https://endless-sphere.com/forums/viewtopic.php?f=31&t=113162&p=1673324#p1673324

 

[DEHiCKA]

got a pic of your modded shaft?

You asked

as for the qs138 v3 w/ gearbox the shaft is a lot thinner so that solution might not work.

I have broken the ends on a couple of custom made shafts for smaller GNG motor.


Probably it will hold if the sprocket will face the motor. Then it will be less strain on the shaft's end.
I was afraid of frame clearance issues, so I did not do QS120 this way.

 

[Overclocker]

probably a stupid thing to do but i turned down my GNG motor's shaft to 10mm to mount this 11t #25 sprocket. hope it doesn't break :lol:





here are some ideas i found on the www, to use all the available splines on the shaft of the qs gearbox motor.

 

[Clueless1]

Anybody have a wiring pinout for the hall sensor, thermals, and motor power phase?

Completely mind boggling how they can ship you a motor without any documentation, and your only source of info is from a poorly translated alibaba sales page.

 

[john61ct]

That is normal.

More than that is what would be mind-boggling.

We gweilo are supposed to be grateful they are willing to bother doing business with us at all.

 

[DEHiCKA]

Anybody have a wiring pinout for the hall sensor, thermals, and motor power phase?

All the QS mid drives i have seen are pretty straightforward.
YGB wires from 6-pin connector goes from hall sensors.
Black is ground, Red is the +5V and the rest if present is the KTY temp sensor.
Actual hall sensor/phase wires connection will depend on your controller and rotation direction

 

[DEHiCKA]

Still waiting for my motor to arrive. Can anyone measure the length of the output shaft form the gearbox cover?

 

[juman]

Still waiting for my motor to arrive. Can anyone measure the length of the output shaft form the gearbox cover?
AcroRd32_1sqzqPkwCf.png

Motor just arrived for myself and looks to be about 21.5mm from the cover. The splines for the shaft stop about 3mm from the cover.

Still waiting on battery so will be a bit before I actually try to fire it up with the EM-200sp they sent with it.

 

[hugok]

Where do they sell it paired with EM200? I have only seen paired with EM150 on aliexpress.

 

[juman]

Where do they sell it paired with EM200? I have only seen paired with EM150 on aliexpress.

Bada boom:
https://www.aliexpress.com/item/1005002011835391.html?spm=a2g0s.9042311.0.0.2c564c4dp6vU6S

It wasn't there a few weeks back though and showed up like 2 days after I was asking them if this kit existed. Quite fast shipping, only about 2 weeks.