Efficient everyday bike

[chbla]

Hi,

Edit: I've changed the plan, see post #10.
I'm planning a lightweight, efficient DIY e-bike based on a 10–13 kg fitness / flat-bar road / light gravel bike.
I don't need it for extensive/steep hill climbing. For this I have an E-Mountainbike.

Main goals:

• 700C / 28"
• rear geared hub with very low drag when unpowered
• disc brakes
• good efficiency at roughly 25–35 km/h
• torque sensing preferred
• standard 36 V batteries, ideally small daily pack + larger touring pack
• not a fully proprietary system
• configurable speed limit preferred
• value and efficiency matter more than high power, I've got an E-Mountainbike too.

Initially I considered the YOSE 350 W rear cassette kit, but the YOSE A3 Pro looks more elegant because it integrates the torque sensor and controller and seems very light.

From what I learned here, the A3 Pro uses an Aikema geared hub, KClamber cassette torque sensor and Lishui controller.
So in theory this seems more or less open (I'm new to this)?
I'm now also looking at LVBU MRT/TK and possibly AKM/Aikema alternatives.

A few questions:

• Has anyone run the A3 Pro with a third-party 36 V battery?
• Has anyone identified or modified/flashed the A3 Pro Lishui controller as this would be the only way to change limits I assume?
• Any successful way to change the fixed 25 km/h limit?
• Does anyone know the real no-load RPM / motor winding of the A3 Pro at 36 V?
• How does A3 Pro vs LVBU MRT compare in real efficiency and freewheel drag?
• Is there a better 2–3 kg geared rear hub with torque sensing for this kind of fast/light 700C build?
• Any real-world experience fitting these nominal 138 mm motors into 135 mm QR aluminium frames?

I'm open for suggestions - bike wise and motor wise...

Thanks a lot!
Christoph

 

[neptronix]

I don't know anything about YOSE.

I do know that Aikema dual reduction motors have pretty good efficiency and power per pound due to the dual reduction inside. Ideal thing for a bike that's more pedal bike than electric i think.

if you have a bit of cash, keyde has some lighter and more efficient motors but reviews on these are mixed, and they are 2-3x more expensive.

topebike kit will sell you a controller that goes with them... dual reduction geared motors require a special controller due to the very high RPM of the motor. I myself will pick a VESC as it will drive anything.. but it's throttle only out of the box.
Not sure what vendors are preferable for Austria. But there's a good amount of other vendors for Aikema motors.

Most 135mm frames are ~137mm uncompressed, moving each chainstay out by 0.5-1mm is not a big deal, and you can adjust around it easily.

Motors themselves don't typically have torque sensing in them, with few exceptions. I'd personally pick a bottom bracket based solution since it is easier to replace the part if it goes south, but i am a throttle guy so i'm no good to advise you on PAS.

 

[chbla]

Thanks, that was very helpful. I’ve narrowed the project down quite a bit now.

The bike will mainly be a lightweight, efficient commuter: mostly flat riding, only occasional climbs, and about 25–35 km/h assisted speed. I already have an e-MTB for high-power use, so this one should stay light and bicycle-like.
I like the thought of having a lightweight, efficient everyday bike instead of these heavy ebikes. There are plenty of good, used sports bikes for this purpose, it's interesting with how little budget you can nowadays get a decent ebike.

At the moment my shortlist is:

• AKM100 non-H
• AKM100H
• Shengyi SX2

I’m leaning toward a modular 36 V setup with a small sinewave controller and interchangeable batteries. Torque sensing is now optional rather than mandatory.

The AKM100 is very tempting because of the ~2 kg weight and low drag, while the SX2 looks better for efficiency/thermal margin under sustained assist - however, it's in a quite different price range, not sure if that's worth it.
Then again, the small weight difference to larger motors with might be more efficient, is eventually not worth it.

One morequestion: are there current AKM/Aikema versions with 12×142 thru-axle / modern axle standards, ideally cassette + disc? That would widen the choice of donor bikes considerably.

Also interested in real-world limits of the AKM100 on 700C at roughly 200–350 W continuous input.

What are your thoughts on this?

 

[docw009]

I have several 20" folders using AKM100's. Nice motor with a 20A controller. Plenty of power at 36V. Mine were 260 and 320 rpm units that spin out at 25 km/hour on the small rims. There were several users here running them on 700 cc wheels. You will probably want the 201 rpm motors. Not much drag that I can feel. A roadie would detect it though.

The AKM100CST was 142mm, if I recall. I used the AKM100H which was a freewheel version for 135mm dropouts. That could be shrunk further if you used a thinner freewheel and trimmed the spacers used to maintain the OLD.. I do not know much about thru-axles.

The AKM128 is 25mm larger in diameter, and will surely resolve any fears about power. The cassette version is 135mm. I have one on a 26" bike. Both my wife/I prefer our torque sense mid drive kits. They are probably less expensive than a Yose kit too.

I know Grin in Canada sells a BB torque sensor and their Cycle analyst allows it to plug into a throttle input on a hub controller. Not interested. They also sell a small thru-axle hub motor.

I think there is more to it than just recognizing the torque sensor input. If Yose were to sell a separate controller with the cassette based torque sensor. I would certainly try it out,

 

[neptronix]

Check topebikekit, i've seen thru axle AKM motors on there.
I'd prefer the H model for improved efficiency during climbing and higher power density.

The H models of AKM are very high RPM due to the 2 gear reductions and requires a special controller capable of high RPM too.

Shengyi SX2 is a really nice motor for a single reduction geared drive. I'm in a very hilly area so i'd rather have a dual reduction drive tor the extra gusto at lower rpm.

If you don't have serious hills then the only reason to get a dual reduction motor is to minimize weight of the bike. They have more moving parts and may be less durable.

 

[molybdenum]

I just purchased the AKM128H from Topbikekit to replace my worn out 128c cst. My old 128c motor and controller cost $140 total, lasted 10 years and 80k km in a very wet climate, so I'm definitely happy with these series of motors. The SX2 looks tempting, just a lot pricier.

 

[neptronix]

How is the motor noise and freewheeling/coasting on the AKM type motors?

 

[molybdenum]

How is the motor noise and freewheeling/coasting on the AKM type motors?

My AKM128H motor has a slight noise in the form of a subtle hum, and not completely silent in spite of KT sine wave controller. The motor freewheels well, with no noticeable resistance. Its predecessor, the Q128C cst, was purchased from BMSbattery, but is essentially a AKM motor with a sticker hiding the AKM brand, and identical to the AKM version. It had similar levels of noise as the new motor.

​

 

[neptronix]

Thanks for the info!

 

[chbla]

Thanks for all the answers and insights! Learning a lot.

After some thinking, I have to reconsider - and I'd like to have your feedback

So the point here was to create a very lightweight E-Bike for daily use, without too much power for steep climbs.
What I have at the moment though is:

1. Bulls Six50 E2, without battery
BULLS SIX50 E 2 STREET Review

2. Radon Urban Supreme (no motor) as my daily driver (~ 12kg)
https://marktplatz.bike/Radon-Urban Supreme FE | Modelljahr 2018

If I get a very lightweight bike now and add a small motor, it would end up in the same weight class as the Radon, which somehow doesn't make sense to me. Often, in summer, I want a fast sports bike and don't need a motor.
Therefore I thought it makes more sense to

1. convert the Radon to electric (lightweight), with a lightweight (daily) and a touring battery.

2. get a 7kg, stripped down, road bike for the summer fun

3. The older Bulls could still be used as a better bike for climbs (I used it for when I go climbing, hauling up equipment).
If I use one of these dongles: https://www.driveunitfix.com/ I could share the batterie with the radon.

What do you guys think about this plan?

The only downside is that I would have to use a front motor for the Radon, however, given the efficiency over performance approach, it probably would work.

 

[molybdenum]

Member chas58 electrified road bikes with the Q100 (same as the AKM100), and is probably most aligned with your philosophy. He hasn't been active here in years, but the threads are still up: Cute Q100 lightweight builds slow mtb, fast road. I took a moderate approach and put a 500W 128H on a lightweight hybrid. with modest battery in pannier, no one can tell the motor from a drum brake, so doesn’t look electric. My commute is hilly, so I need a bit of extra oomph compared with chas58. Most members here want lots of power, and there isn't much interest in low power minimalist builds, but I'm sure you'll find help here nonetheless.

 

[Apartunis]

You specify rear hub motor but your application suggests front hub motor would be better. You would have a better rear wheel and more gearing options with the hub motor in front. The motor drive would be completely separate from the pedal drive which has practical advantages.

If stealth is important then using a small diameter rear hub motor is probably best. There are tradeoffs however.

 

[chbla]

How do you mean?
With Post #10 Efficient everyday bike
only front wheel would be possible as I have the shimano alfine in the rear which doesn't make sense to replace.

Stealth is not that important I guess since I can stick to the allowed power.

 

[braunschweiger]

I have same radon bike converted with lightweight front akm 75sx 201rpm on 10S =36V with VESC controller plus homebrew PAS2throttle analyst. Limit for erpm is set to adhere 25km/h. in mostly flat area it runs by itself at 8A phase current limit
My smallest battery provides 2.5Ah which is good for one hour ride. probably not so good in the hills. https://www.pedelecforum.de/forum/i...gebnis-nicht-der-werdegang.24822/post-2408702

 

[Apartunis]

How do you mean?
With Post #10 Efficient everyday bike
only front wheel would be possible as I have the shimano alfine in the rear which doesn't make sense to replace.

In your "main goals" you said "rear geared hub with very low drag when unpowered". If that was by mistake then I guess you already understand a front hub motor is a good match for this project.

 

[chbla]

In your "main goals" you said "rear geared hub with very low drag when unpowered". If that was by mistake then I guess you already understand a front hub motor is a good match for this project.

Ah sorry - I've updated the goal in the thoughts in post #10 - so now I'm basically modifying an existing bike with a rear geared hub. Thus I need the motor in the front anyway. Overall it seems to be the better solution give my initial goals.

 

[chbla]

I have same radon bike converted with lightweight front akm 75sx 201rpm on 10S =36V with VESC controller plus homebrew PAS2throttle analyst. Limit for erpm is set to adhere 25km/h. in mostly flat area it runs by itself at 8A phase current limit
My smallest battery provides 2.5Ah which is good for one hour ride. probably not so good in the hills. https://www.pedelecforum.de/forum/i...gebnis-nicht-der-werdegang.24822/post-2408702

Very cool! I'm no expert as I never modified a bike, but that sounds very interesting!
My sparring partner is ChatGPT, so I'm only finding out about all these possibilities.

The size and weight of that motor - and also battery - are tempting.
However, so far I thought about the Bafang H600 for my purpose (~30 km/h and occasional slight hills).