QS 138 70H with Gearbox

[j bjork]

Very nice, more info please :wink:
I dont see any splines for the gear, is it shrink on?
I suppose the shaft is custom made and not available to buy?

And the bike, I like the little I can see.
Looks like some nice welding and some interesting looking brackets for the motor.
A build thread would be nice to see

 

[El Gaucho]

That is a great idea, you should sell those! I feel like the 428 chain size is better suited for the e moto setup, and quieter than a 520

 

[JTR]

I do have some spares if people wanted to do some testing.

No splines, factory is shrink/interference fit. I agree 428 is the go, mostly to avoid huge rear sprockets for me.
Bike is this one, but with QS138 and 24f now https://www.electricbike.com/jeremy-webbs-husqvarna-e-conversion/

 

[Mallie]

So what are people’s recommendations for the front and rear sprocket ratios for this motor with the built-in gear reduction?

Am I correct that QS says 1:3?

I’m looking to use the QS138 70H in a vintage scooter, with a 12” wheel. Scooter will probably weigh around 130-140kg (285-310lbs). Scooter would be mainly for commuting, but my commute includes a bit of motorway, so want to be able to do 100km/hr (65m/hr). Was thinking I’d probably just use the Votol EM150 or may EM200. Looking at CALB CAM72 batteries in a 23s 1p config for 72V 72ah, but should handle 150A continuous.

The scooter has a 40 tooth rear sprocket originally - which would be the easiest option. So the standard 14 tooth front sprocket that QS ships these with should be pretty close to 1:3. By my calculations, though, that’d only get me something like 75km/hr at, say, 5,500 motor RPM?

It seems like I’d need more like a 1:2 ratio (19 or 20 tooth front sprocket with a 40 tooth rear) to get 100km/hr at that sort of RPM. (This assumes a rolling wheel circumference of about 1529mm (for a 130/70 x 12 tyre).) Or am I calculating this wrong?

Is 5,500 motor RPM a reasonable assumption? It looks like that may be what QS has used to calculate the 100km/hr for their QS138 70H motor kit (with swingarm and belt drive).

The QS138V3 will not fit a 420 19t or 20t front sprocket without modifying the front case. I have a 16T and it is pretty close. With such small tires it doesn't seem like the V3 (built in gear reduction) is the best choice. You could run a QS138V2 (non-geared) and achieve 100kmph without spinning the motor up to 5500rpm (which is achieved by heavy field weakening which pulls more current).

Im Also Building A Bike For Commuting Its A Yamaha DT400 That Im Transforming Into A Bobber.
Im Hoping To Be Able To Hit About 60-70mph But Im Not Sure What Motor I Should Get.
I Saw That You Also Have A DT And Im Wondering If You Ever Finished Your Project And
Whats The Performance You Get With The V3? Is It A Good Option For My Use?
Im Deciding Between The 70h Or 70h V3

 

[Eastwood]

What size rear sprocket are you guys running with the factory 15t front? obviously voltage/rpm’s and wheel size plays a huge factor as well but just curious of any feedback with gearing with this V3?

With having a custom 428 sprocket made as you know it’s not cheap so trying to get this right on the first attempt

Considered the 520 Front sprocket but would rather keep the smaller chain for less noise and less weight. Would definitely be cheaper to run the 520 front so you could buy a regular rear sprocket

 

[Jordan325ic]

Im Also Building A Bike For Commuting Its A Yamaha DT400 That Im Transforming Into A Bobber.
Im Hoping To Be Able To Hit About 60-70mph But Im Not Sure What Motor I Should Get.
I Saw That You Also Have A DT And Im Wondering If You Ever Finished Your Project And
Whats The Performance You Get With The V3? Is It A Good Option For My Use?
Im Deciding Between The 70h Or 70h V3

At 60v@120A (~7kw continuous) I can cruise at 55mph with the v3. No field weakening. The motor is not the bottleneck. To go faster I would either change the gearing and add amps or go with a higher voltage battery.

The V3 just allows you to simplify your drivetrain so you don’t need custom, oddly sized sprockets. To get to your desired top speed, figure out what speed your rear tire needs to rotate at, then work backwards. You probably want something like 1000rpm rear wheel for 70mph.

 

[MomentFD]

Is anyone on a EM-150SP/2 controller? I have my QS 138 70h v3 spinning forward with the rear wheel elevated, but once I put it on the ground it can't produce enough torque to roll the bike. Instead I hear a slight hum from the motor like it's trying. My phase wiring is shown below and motor settings screen. I've posted on the EM100/EM150 thread page 87 if you want to see more screens or my ini file.

I would be anxious to see a .ini file and phase wiring connection that works for this setup. I haven't connected much of the harness or port assignments other than 1 line to display. I would like to confirm the 23 pin pinout and mapping to port assignments before I go further there.

Thanks for any help! I can communicate fine with controller which I'm happy about - feeling close.

 

[MomentFD]

Fixed this one with a base config file and adjusting my motor settings to -60, exchange phase wires blue-green, new file is attached.

From your guys experience, is there an area of parameter tuning that can be risky for safe controller/motor/battery operation? Just in general I want to know what areas to be more cautious with, if they exist.

Thanks & cheers!

 

[Jordan325ic]

Just a note for anyone considering this motor:

It sounds awesome. Those straight-cut gears have a very good sound. Not noisy by any means, but it does cover up the noise of the chain drive pretty well.

I'm at 1,600 miles so far on my conversion.

 

[romelec]

Some people might be interested, here is the motor drawing in PDF format.

 

[MDG]

Is it normal for this motor to get pretty warm? I did a 10 mile test ride today. 125A continuous at around 40-45mph. Everything felt fantastic but motor was quite warm, almost too hot to touch. First time dealing with these mid drives so wanted to ask! Love it though, very well made unit!

 

[Hummina Shadeeba]

A lot of people above are writing about the work they did to get a tight fit of the sprocket on the shaft but in my looking the very loose fit it comes with is standard for “pit bikes” and some other dirt bikes. It’s supposedly intended for misalignment. Why it would be designed for misaligned I can’t fathom. I’ve also found a video of a guy who adds a washer on the shaft then bangs the sprocket holder part on so it’s a rigid fit.

All revealed here:

Reddit - Dive into anything

reddit.com

I’m finally getting this going this long weekend as soon as I figure which little wires go to which pins in the plug