From Concept to Prototype: Ultra-Light Ebike Kit for Road Bikes Now in Development!

[Katrina92]

Hi everyone,
The enthusiasm from our previous discussions about a lightweight road bike-compatible hub motor (targeting bikes like my Scott Addict) inspired my engineer partner and me to take the leap — we’ve built a functional prototype!

Why This Matters:

• There are few ultra-light e-bike conversion kits on the market for thru-axle riders. Although systems like the Mahle X20 meet the lightweight requirement, they're only available on complete bikes. So, it seems that riders like me, who don’t want to buy a whole e-bike, have few options left.
• Our goal is to create an ultra-light, super-compact hub motor, which can assist climbing without being a burden, only helping when needed, while preserving the essence of the cycling experience.

Here is my previous post:
https://forums.electricbikereview.c...-the-idea-in-my-head.57724/page-3#post-681391

What We’re Sharing:

• A design sketch

• Prototype structure components

Welcome to leave your comments. Any thoughts will be appreciated

 

[Base]

kindernay like hub-shell would be great to be able to service the motor and easy-er building wheels. Also how are you going to include a torque arm/ non turn washer like thing to the hub? Build in rotation sensor or pressure sensor?

 

[mschwett]

Hi everyone,
The enthusiasm from our previous discussions about a lightweight road bike-compatible hub motor (targeting bikes like my Scott Addict) inspired my engineer partner and me to take the leap — we’ve built a functional prototype!

Why This Matters:

• There are few ultra-light e-bike conversion kits on the market for thru-axle riders. Although systems like the Mahle X20 meet the lightweight requirement, they're only available on complete bikes. So, it seems that riders like me, who don’t want to buy a whole e-bike, have few options left.
• Our goal is to create an ultra-light, super-compact hub motor, which can assist climbing without being a burden, only helping when needed, while preserving the essence of the cycling experience.

Here is my previous post:
https://forums.electricbikereview.c...-the-idea-in-my-head.57724/page-3#post-681391

What We’re Sharing:

• A design sketch

View attachment 194018

• Prototype structure components

Welcome to leave your comments. Any thoughts will be appreciated

how is the reaction force against the frame handled? there’s a reason lightweight carbon road eBikes have much heavier rear dropouts than their acoustic cousins - to house the non-rotating nut and transmit those forces into steel pieces embedded into heavier carbon members.

i would guess the chainstay is where you’ll need to do this, with some kind of external arm. seat stays are too thin and of more variable geometry. power wires also have the potential to be super messy, are you going to get them through a custom through axle?

 

[Rás Cnoic]

Thought there was something fishy in your previous messages. Something about the tone was a head scratcher. I even began to suspect this was AI.

It didn't quite add up that you were just looking for help in finding a lightweight motor.

I feel used...

 

[PedalUma]

From experience, lightweight road bikes are already pushing limits without margins of redundancy for strength. You will kill the bike, not enhance it.

 

[Stefan Mikes]

Good luck Katrina. I'm waiting for your future report. I still wonder where you intend to house the battery and what battery. Hopefully, the bike frame would not crack at the most unfortunate moment, so you'd be able to report!

There were thousands of bike inventions that now pave the Hell.

 

[Gionnirocket]

The factory has already started trimming weight off the unnecessary. . .

 

[PedalUma]

But it could work if rolling backwards. First an aside: I was working as an inside sales support advisor for a large bike company. Someone called in. Their bike rolls forward in their apartment but does not roll backwards. The answer was KICKSTAND! When rolling forward the freewheel coasts. It only engages when rolling backwards. So according to the drawing it could work going backwards, but not forwards. It would not engage but only spin without moving the gears in the forward setting.

 

[harryS]

Hope you succeed, . Seems like you'll be using a lot of gears in there to push a bike..

 

[Katrina92]

Hope you succeed, . Seems like you'll be using a lot of gears in there to push a bike..

Thanks! Are you talking about the gearbox inside the motor?

 

[Katrina92]

The factory has already started trimming weight off the unnecessary. . .

View attachment 194034

The weight and size of a motor are strongly correlated. Shrink the volume, and the weight tends to drop too.

 

[Katrina92]

Good luck Katrina. I'm waiting for your future report. I still wonder where you intend to house the battery and what battery. Hopefully, the bike frame would not crack at the most unfortunate moment, so you'd be able to report!

There were thousands of bike inventions that now pave the Hell.

I’m planning to mount the battery on the bottle cage and will probably go with a lithium pack.
I don’t need that much range cuz I won’t be using full assist all the time or staying in the highest power mode for long.
The frame’s not going to crack — like I mentioned before, I’m not after crazy amounts of power.

 

[Katrina92]

From experience, lightweight road bikes are already pushing limits without margins of redundancy for strength. You will kill the bike, not enhance it.

Totally fair point.
The idea isn’t to overpower the bike, just to complement it.

 

[Katrina92]

how is the reaction force against the frame handled? there’s a reason lightweight carbon road eBikes have much heavier rear dropouts than their acoustic cousins - to house the non-rotating nut and transmit those forces into steel pieces embedded into heavier carbon members.

i would guess the chainstay is where you’ll need to do this, with some kind of external arm. seat stays are too thin and of more variable geometry. power wires also have the potential to be super messy, are you going to get them through a custom through axle?

That’s definitely something worth thinking about — I haven’t fully worked out how to handle it yet, to be honest.
Just to clarify — what do you mean by 'a custom through axle'? I’m not quite sure I understand that part.

 

[Katrina92]

kindernay like hub-shell would be great to be able to service the motor and easy-er building wheels. Also how are you going to include a torque arm/ non turn washer like thing to the hub? Build in rotation sensor or pressure sensor?

I think a built-in torque sensor is a must. I want the motor to respond based on how hard I’m actually pedaling.

 

[Katrina92]

But it could work if rolling backwards. First an aside: I was working as an inside sales support advisor for a large bike company. Someone called in. Their bike rolls forward in their apartment but does not roll backwards. The answer was KICKSTAND! When rolling forward the freewheel coasts. It only engages when rolling backwards. So according to the drawing it could work going backwards, but not forwards. It would not engage but only spin without moving the gears in the forward setting.

Just to make sure I’m following — are you saying that, based on the drawing, the motor might only engage when rolling the wheel backwards, not forwards?

 

[Base]

That’s definitely something worth thinking about — I haven’t fully worked out how to handle it yet, to be honest.
Just to clarify — what do you mean by 'a custom through axle'? I’m not quite sure I understand that part.

just been thru some reading on thru-axle motors, the ones we have seen do not have non-turn washers or reaction arms

 

[harryS]

Thanks! Are you talking about the gearbox inside the motor?

Yes.

The Fazua, as I read it, puts out 1.9N at its output shaft, and that motor is much longer than a 135 mm dropout on a typical bike. It multiplies that with a gear that turns the pedal axles, with further increases thru the derailleur.

Your concept drawing show a motor not much wider in diameter than a hub, around the size of a Fazua. Give it it a 1 nm output for being half as long. I'm no mechanical engineer, but seems to me it's going to need some innovative gear design to even get 5X multiplication.

 

[Chargeride]

The drive unit off an electric drill, two planetary gear reductions...bit whiny thought