High-speed, long-distance (heavy "30^3") Q128 commuter build

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mystryda
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Re: High-speed, long-distance (heavy "30^3") Q128 commuter b

Post by mystryda » Nov 14, 2017 12:21 am

Parts came!!! Yay!!!

I ended up ordering the Q128C (328rpm @ 36V). (I had wanted the Bafang CST because it seemed like the "safer bet" but I couldn't source it in the voltage/rpm to match what I needed.)

I've got the bike upside down and the motor sitting in the drops so that I can test it out before building up the wheel. Here's what I'm finding:

1) The inline power meter that I bought (https://www.ebay.com/itm/191907345162) shows a significantly different power consumption that the LCD6 controller (33W vs 23W, respectively). Since the inline power meter is in agreement with my multimeter, I'm assuming that the current measurement on the LCD6 is less than stellar. Anyone else find this?

2) The two motors have different current draws at no load, WOT. According to my power meter, one motor consumes ~33W, the other a full 50W. Does this mean that something's wrong with one of the motors?

3) I measured 10.79 revs/volt.
--Measured at two points: 380rpm @ 35.2V & 424rpm @ 39.3V.
--I had to set the wheel size to something really small, otherwise I was running up against the "45 mph" max speed limit.
--This is rather different from the 328rpm/36V listed, but it's totally workable. Is this consistent with what others have found on the Q128C?

4) How is the controller measuring speed?!? Anything voltage that I can it above the 30V cutoff when running with a 700C wheel shows 45 mph at WOT, no load. My motor sim shows about 30mph at 380rpm, not 45mph. Is this a motor pole parameter or something?

But, yay, parts, the motors run, etc.

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Re: High-speed, long-distance (heavy "30^3") Q128 commuter b

Post by d8veh » Nov 14, 2017 8:11 am

Hmmm! A lot of strange results. You're using 36v? You wouldn't want to run a 36v 328 rpm one at 48v.
Are the two motors both Q128Cs? With these sort of motors, the no-load power is generally around 36W at around 20 mph.

The motor has a one pulse per ritation speed sensor in it, which the controller will be using if the speed display continues while the wheel is free-whheling. If the speed goes to zero when free-wheeling, the controller is using a motor hall sensor for the speed signal so you have to set the parameter in the settings to change it.

Your speed seems to be too high. You should check it with an independent cycle computer.

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Re: High-speed, long-distance (heavy "30^3") Q128 commuter b

Post by mystryda » Nov 14, 2017 2:09 pm

d8veh wrote:You're using 36v? You wouldn't want to run a 36v 328 rpm one at 48v.
I've used 36V and 40V in these tests because that's simply convenient for the testing setup that I have.

Consistent with Chas58's recommendation and the analysis from the simulator, I was planning on running them at whatever voltage gets a no load speed of about 440 rpm (34mph). When I thought that the motors would run at 328rpm @ 36V no load, that number actually about 48V. Now I'm thinking that it's going to be 40V/11S.
d8veh wrote:Are the two motors both Q128Cs? With these sort of motors, the no-load power is generally around 36W at around 20 mph.
Yes, both are Q128Cs.
d8veh wrote:The motor has a one pulse per rotation speed sensor in it, which the controller will be using if the speed display continues while the wheel is free-whheling. If the speed goes to zero when free-wheeling, the controller is using a motor hall sensor for the speed signal so you have to set the parameter in the settings to change it.
This is hard to check. The motor's bare/not laced to wheel and consequently has a relatively little rotational mass (a small moment of inertia), so when I let off the throttle the motor stops spinning almost immediately. The controller and/or display is doing some sort of smoothing or interpolation, and so it's still counting down after the motor has completely stopped.
d8veh wrote:Your speed seems to be too high. You should check it with an independent cycle computer.
The speed displayed on the LCD6 seems too high? I agree. 380 on a 700C corresponds to 30mph, so when it shows 45 mph it's too fast by 3/2.

I measured the motor speed in rpms by sticking a piece of electrical tape like a flag on one of the flanges that then flaps against a piece of 3x5 card. I counted clicks as the motor was running. (4 clicks were treated like 16th notes--semiquavers for you brits--to the quarter note that I tapped into a metronome. It's crude, but effective and very repeatable.)

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Prototype Build: Considerable resistance while freewheeling

Post by mystryda » Nov 21, 2017 12:22 pm

The bike's built and runs! Yay!!!

The Q128C is laced up to an Alex R450 rim with Sapim "Race" double-butted (14/15) spokes and brass nipples. I used both nipple washers at the rim (since it doesn't have eyelets) and brass SAE #2 spoke washers to take up the wiggle at the rim and distribute the load. I'm running a Continental GP 4 Season 28C, which is the largest tire that I can fit in the bike.

There's a lot of drag when the wheel is freewheeling. I had read on this forum that a geared hub more freewheeled like a regular rear wheel, but this isn't what I've found. If I stop pedaling the drag is immediately noticeable. Here's a video of me giving the cranks a kick and how quickly the wheel spins down. (If I'd done the same thing with a normal wheel in good condition, it would've continued spinning for several times as long.)
https://youtu.be/oDuANY9qTac

Is this expected? Does it get better with use? Is there something that can be replaced or modified to improve?

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Re: High-speed, long-distance (heavy "30^3") Q128 commuter build

Post by motomech » Nov 21, 2017 12:47 pm

Sounds like something is wrong.
My Q100's will spin almost as long as the bicycle ASM.
Are you sure the washers/spacers are connecting the wheel bearings and nothing else?
I would probably would flip the bike up-side down, loosen the axle nuts and see if it will free-wheel better.
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'03 Rocky Mountain Edge 2WD 260 Q100H frt and Ezee V1 rear 2 Elifebike 20A & 25A 9-FET controllers 12S/20Ah Multistar Lipo rear 5Ah Turnigy frt Luna Cyclops Extra lite Alex 24DM rims, 2.4 Holly Rollers run ghetto tubeless. 25 mph. Mean Well HLG-320H-48A
https://endless-sphere.com/forums/viewt ... =3&t=83430
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Re: High-speed, long-distance (heavy "30^3") Q128 commuter build

Post by mystryda » Nov 21, 2017 3:37 pm

Thanks. I’ll try that tonight.
motomech wrote:
Nov 21, 2017 12:47 pm
My Q100's will spin almost as long as the bicycle ASM
What’s “ASM?”

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Re: High-speed, long-distance (heavy "30^3") Q128 commuter build

Post by motomech » Nov 21, 2017 6:47 pm

Assembly
Motomech

'03 Rocky Mountain Edge 2WD 260 Q100H frt and Ezee V1 rear 2 Elifebike 20A & 25A 9-FET controllers 12S/20Ah Multistar Lipo rear 5Ah Turnigy frt Luna Cyclops Extra lite Alex 24DM rims, 2.4 Holly Rollers run ghetto tubeless. 25 mph. Mean Well HLG-320H-48A
https://endless-sphere.com/forums/viewt ... =3&t=83430
'07 GT Idive 4 4.0, Q100C 201 12S LiPoly elifebike 9-FET 17A controller. 20 MPH.
https://endless-sphere.com/forums/viewt ... 8#p1237928

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Re: High-speed, long-distance (heavy "30^3") Q128 commuter build

Post by d8veh » Nov 22, 2017 7:29 am

Is the brake binding? The wheel doesn't look true enough for a rim brake.

mystryda
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Re: High-speed, long-distance (heavy "30^3") Q128 commuter build

Post by mystryda » Nov 22, 2017 8:01 am

d8veh wrote:
Nov 22, 2017 7:29 am
Is the brake binding? The wheel doesn't look true enough for a rim brake.
The wheel was within 1mm of true when I built the wheel, but I know more about wheel building than I have experience doing it, so I'll double check when I get home. I checked the video and I think I see what you're seeing, but I can't tell if the effect is just me moving the camera.

Things got busy at home last night and I didn't get a chance to check what motomech described, yet, either. Life happens!

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Re: High-speed, long-distance (heavy "30^3") Q128 commuter build

Post by 1N4001 » Nov 28, 2017 8:04 am

An interesting build. I've been following this as I am planning a fairly similar one soon, also with the fast Q128C.

The high amount of drag on the wheel can't be right. Even my BionX motor (direct-drive with no freewheel) has less drag. Which motor did you lace in, the one which previously needed more power to spin? There might be a correlation. I would open it up and have a look.

motomech wrote:
Oct 06, 2017 12:36 pm
What about running at 72V and trimming back the controller? Is there a downside to the higher voltage? If nothing else, the batteries would be easier to put together.
Nooooooo :shock: The Q128 is basicly a bigger Q100 and we well know the Voltage limits of that motor as they have been tested to destruction. Phase wires will start to melt first and by the time the Voltage gets into the 60's Volt range, the winding are likely to start cooking.
I don't understand this. Battery voltage influences potential maximum current flow, but isn't the point of a controller to limit and control this current? If I want 10A phase current, I can limit to 10A phase current, regardless of battery voltage.

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Re: High-speed, long-distance (heavy "30^3") Q128 commuter build

Post by Buk___ » Nov 28, 2017 11:05 am

1N4001 wrote:
Nov 28, 2017 8:04 am
I don't understand this. Battery voltage influences potential maximum current flow, but isn't the point of a controller to limit and control this current? If I want 10A phase current, I can limit to 10A phase current, regardless of battery voltage.
It's the resistance of the phase wires & windings that is the problem. Thin wires have high(er) resistance, and the more volts you put in the more of the amps supplied will be converted to heat before the motor even turns.

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Re: High-speed, long-distance (heavy "30^3") Q128 commuter build

Post by 1N4001 » Nov 28, 2017 12:10 pm

Buk___ wrote:
Nov 28, 2017 11:05 am
1N4001 wrote:
Nov 28, 2017 8:04 am
I don't understand this. Battery voltage influences potential maximum current flow, but isn't the point of a controller to limit and control this current? If I want 10A phase current, I can limit to 10A phase current, regardless of battery voltage.
It's the resistance of the phase wires & windings that is the problem. Thin wires have high(er) resistance, and the more volts you put in the more of the amps supplied will be converted to heat before the motor even turns.
You are of course correct, but nobody proposed running more amps. Does a a higher battery voltage on its own increase current flow, assuming a controller is limiting power?

Plus, you could run a slower motor with beefier windings and reach the same speeds.

So I really don't get why it would be detrimental to this motor.

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Re: High-speed, long-distance (heavy "30^3") Q128 commuter build

Post by motomech » Nov 28, 2017 12:56 pm

1N4001 wrote:
Nov 28, 2017 8:04 am
An interesting build. I've been following this as I am planning a fairly similar one soon, also with the fast Q128C.

The high amount of drag on the wheel can't be right. Even my BionX motor (direct-drive with no freewheel) has less drag. Which motor did you lace in, the one which previously needed more power to spin? There might be a correlation. I would open it up and have a look.

motomech wrote:
Oct 06, 2017 12:36 pm
What about running at 72V and trimming back the controller? Is there a downside to the higher voltage? If nothing else, the batteries would be easier to put together.
Nooooooo :shock: The Q128 is basicly a bigger Q100 and we well know the Voltage limits of that motor as they have been tested to destruction. Phase wires will start to melt first and by the time the Voltage gets into the 60's Volt range, the winding are likely to start cooking.
I don't understand this. Battery voltage influences potential maximum current flow, but isn't the point of a controller to limit and control this current? If I want 10A phase current, I can limit to 10A phase current, regardless of battery voltage.
In the end it's simply a matter of total Wattage.
Raising the Volts and reducing the Current eventually takes a motor that is limited in top speed by rpm (Volts), and turns it into a motor that is Power (current) limited.
My experience is w/. the smaller Q100 variants, so my est.s on when and where this would be the case w/ the Q128 on my part is conjecture.
I do know that the first area I ran into problems w/ the Q100's was the cheesy Hall wire connectors. I imagine the Q128 comes w/ the same connectors, which should be replaced. I strongly suspect the Hall wires themselves would be the next vulnerable component.
Motomech

'03 Rocky Mountain Edge 2WD 260 Q100H frt and Ezee V1 rear 2 Elifebike 20A & 25A 9-FET controllers 12S/20Ah Multistar Lipo rear 5Ah Turnigy frt Luna Cyclops Extra lite Alex 24DM rims, 2.4 Holly Rollers run ghetto tubeless. 25 mph. Mean Well HLG-320H-48A
https://endless-sphere.com/forums/viewt ... =3&t=83430
'07 GT Idive 4 4.0, Q100C 201 12S LiPoly elifebike 9-FET 17A controller. 20 MPH.
https://endless-sphere.com/forums/viewt ... 8#p1237928

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Re: High-speed, long-distance (heavy "30^3") Q128 commuter build

Post by Buk___ » Nov 28, 2017 1:18 pm

1N4001 wrote:
Nov 28, 2017 12:10 pm

You are of course correct, but nobody proposed running more amps. Does a a higher battery voltage on its own increase current flow, assuming a controller is limiting power?
Take a (longish) length of wire, put 36v across it and a certain current will flow: I = V/R, R doesn't change, so if V increases, I increases. At 48V, it will require 50% more current just to overcome the resistance!

If you set the controller to limit the current at 48V to be the same as at 36V, you'd have to set it so low that there would be no current to make the motor turn.

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Re: High-speed, long-distance (heavy "30^3") Q128 commuter build

Post by cycborg » Nov 28, 2017 6:05 pm

Buk___ wrote:
Nov 28, 2017 1:18 pm
Take a (longish) length of wire, put 36v across it and a certain current will flow: I = V/R, R doesn't change, so if V increases, I increases. At 48V, it will require 50% more current just to overcome the resistance!

If you set the controller to limit the current at 48V to be the same as at 36V, you'd have to set it so low that there would be no current to make the motor turn.
The controller regulates the voltage. Say your operating conditions require 20 V and 15 A to the motor. Then the controller will take the 36 V from the battery and apply 20/36 = 55% PWM, drawing 15*0.55 = 8.3 A from the battery. For a 48 V battery, it will apply 42% PWM, drawing 6.25 A from the battery.

Notice that for the same operating conditions, the phase amps are the same in both cases, and the battery amps are actually less for the 48 V battery.

Higher voltage allows you to run at higher speed. But for the same speed and torque, the controller will take whatever voltage you give it and regulate it down to the appropriate level.

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Re: Prototype Build: Considerable resistance while freewheeling

Post by docw009 » Nov 29, 2017 11:46 pm

mystryda wrote:
Nov 21, 2017 12:22 pm
Here's a video of me giving the cranks a kick and how quickly the wheel spins down. (If I'd done the same thing with a normal wheel in good condition, it would've continued spinning for several times as long.)
https://youtu.be/oDuANY9qTac
Didn't you kick it backwards? It's spinning pretty good against the clutch.

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Re: High-speed, long-distance (heavy "30^3") Q128 commuter build

Post by dogman dan » Nov 30, 2017 7:20 am

That video looks exactly normal to me, for a gear motor wheel. They coast fine on the road, but in the shop, there is clearly a lot more friction in the hub than a normal, well operating bike wheel. There is also more mass, so maybe you don't get quite the same initial rpm from one pedal stroke as well. The bike wheel is nearly perfect, after a century of development to reduce all friction in the hub. The motor has the additional clutch inside adding some drag, but nothing you will feel when pedaling really. You WILL feel the extra weight big time, when pedaling unpowered.

With the motor wheels, you won't have quite the same coasting ability, but it will still be plenty to extend range by coasting all you can. You will find that on the flat, your extra weight will affect coast distance then as well. On a slight downhill, you will coast fine.

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Re: High-speed, long-distance (heavy "30^3") Q128 commuter build

Post by docw009 » Nov 30, 2017 1:58 pm

Ok. I see it now. I thought I was looking at a front wheel. My Q100's spin a lot more free than that, but I have a Q128H still unlaced, and I can barely turn the axle with my fingers. It should loosen up.

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