Flixbike 1.0 - CLWB semi-recumbent from scratch

[qwerkus]

After more than 1.5 years of work and lots and lots of setbacks, I finally finished my CLWB (Compact Long Wheel Base) fully. The whole process started years ago, when personal health limitation forced me to look for alternate bicycle design. Than I came to realize there was no bicycle available meeting all my requirements. All I wanted was a stable, comfortable e-bike with a backrest that is as low-maintenance as possible, has a solid luggage rack at the front and still fits in the car if required. So I started drawing stuff in Blender and step by step made it all the way to this bike. The biggest help was by far the framebuilder who had tons of experience with alternate designs, but the entire project would not have been possible without the many little gestures and advices from people all along the way.

So far I've ridden slightly over 200Km and can't stress enough how enjoyable it is: most semi recumbents come with some sort of bent steerer which make steering awkward. This bike comes with a straight direct steering tube, which makes it super reactive. The flat steering angle comes with the additional benefits of allowing a generous font rack and a large front wheel trail, which increases stability as you go faster, just like a harley. The front fork is a regular 20" suspension one, compatible with most models on the market - proving hereby that it's actually possible to design a CLWB without using some exotic small front forks and wheels. The rack is very handy, and allows up to 25Kg of luggage, this also increases stability, especially on lose ground. Another common issue is the very long chain going from the BB to the rear wheel. This bike solves that problem by splitting it: front transmission is a clean belt, so no need for chainguards, and the rear transmission can be a chain .. or a second belt, since the middle jagshaft is concentric with the rear suspension axle: works very well!

The electric part took longer than expected: while the battery was no real issue since I designed the frame to clamp it down, the vesc controller proved more of a challenge. Like many here know, the key problem is the display. You can write a custom lispBM script to communicate with almost all chinese ebike displays available, but those are often sluggish and don't show the information you need. So again I started from scratch and programmed my own display. Luckily there are plenty of knob style displays available nowadays with decent screens so I picked the best amoled with a reasonable size and coded an lvgl based gui: looks good and is very reactive. Also, it allows for CANbus or uart communication which might come in handy, and since it packs an esp32s3, future possibilites include OTA and remote control of the vesc.

And last but not least, one might wonder where that funky motor comes from. It took me a while, but I found a chinese manufacturer that still makes Direct Drive hubs with integrated geared hub. Getting a sample proved near impossible, so I looked for a used sparta r5te bicycle and found one in the netherlands. Had to convince the owner to send the motor only via international shipping all the way here but it worked and I finally had my motor. Than I realized there were no halls and the stock cable was garbage. So I opened up the beast - which helped confirming it had 34 Poles - added 3 halls, a temp sensor and soldered a L1910 cable, before lacing it again into a 20" rim. And look, now it's working!

Next step would be marketing: should enough people show up that are interested into the CLWB, I'd start a first series, maybe to be sold as framekit.
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Flixbike Fully CLWB - 2024
Design: Felix "qwerkus" Schalck, felix.schalck@gmail.com
Framewelding: Sebastian Lindler, seli-online@gmx.de

Tires: 20x2.6 front and rear
M sized frame for 1.65-1.85m people
Seat height: 72cm
Wheelbase: 1420mm
Total length: 1950mm
Weight: 22.5kg without motor
with direct drive and 104cell battery: 35kg
Frame: CrMo4 + stainless steel for vulnerable parts (dropouts, for example)
Suspension travel: 80mm front and rear
Seat: Van Raam
Fork Spinner 300 AIR
Shock: SR Suntour
Brakes: Shimano
Drivetrain: Front Gates CDX, rear 1 1/8" chain + 5 speed SA IGH or 7 speed shimano IGH
Electric:
Motor: Nantong-Leisheng direct drive with integrated hub gears, 34 Poles max power (short period) 1.5Kw, continuous 500-700W
Battery: 48V 104xSamsung 35E cells = approx. 27.5Ah or 1.32Kwh
Controller: VESC with own-programming
Display: custom made 1.5" Amoled knob display with rotary encoder.

Folding mechanism: Remove the center shock and tilt the swing arm forward, then remove the wheels as required, pull out the seat and handlebar extension and remove the fork + rack. Completely disassembled, the bike fits into a 95*70*40cm box.

 

[amberwolf]

Quite a long while back, this would've been a great bike for my purposes (but I require much more cargo space nowadays :lol: ). I'd've used a suspended-mesh framework seat, but most of the rest I think would've worked for me.

Does it handle well at low speeds; startups from a stop?

I like the battery box; is the charger integrated?

Clever display/control interface; is it waterproof? I assume it's like some of the ones i've seen here and there that you rotate the outer edge for changing input, push down for "select" (either the whole surface or just one spot on the edge like a cursor pad), etc.?



I see the headlight and taillight--does the tail do brake light duty as well? Are there turn signals?


One thought about the taillight: In my experience, having the light as close to driver eye level (for following traffic), or at least the level of the average vehicle rear lighting, makes it more certain they pay attention to it. As large a surface area as possible helps them react more quickly as it makes you appear closer, and/or larger, both of which put you into the category of "things to pay attention to now and not dismiss" for the purely reactive brain used for such things. Brightness isn't nearly as important as size, for this.

The latter applies to the headlight also, for people coming out of driveways, etc., to make them pause longer as you approach instead of dismissing you as too far away or too small to worry about, and just going anyway even though you are actually right there. :/ But the taillight size and placement is more important.

 

[neptronix]

super cool bike and happy to see it running!

How is high speed cornering on this thing?

 

[qwerkus]

super cool bike and happy to see it running!

How is high speed cornering on this thing?

During a downhill ride yesterday, I cornered easily @50km/h. Didn't realized the speed until a car had to accelerate to overtake me. The whole thing feels like pressed to the road - no sure which physics are in play here. On loose ground though the unloaded front wheel tends to loose traction and I would not recommend cornering over 25km/h, especially if you might have to brake. Notice that I have very good tires (continental e contact plus) which are still pretty new.

 

[qwerkus]

Quite a long while back, this would've been a great bike for my purposes (but I require much more cargo space nowadays :lol: ). I'd've used a suspended-mesh framework seat, but most of the rest I think would've worked for me.

There is an stainless M6 Threading on the end of the seat-tube to mount a trailer hitch.

Does it handle well at low speeds; startups from a stop?

With a torque sensor, start from standstill are easy. But I already burned through one, so I added a throttle function to start from 0 anywhere, since the law changed here, and now throttles are allowed up to 22km/h

I like the battery box; is the charger integrated?

Nope, Rosenberger ropd charge socket. There is plenty of space left inside though despite the 104 cells, since the orginal plan was to put the controller inside the battery box. Than during the countless tweaks on the vesc it became tedious to re open the box, so I bolted the controller onto the battery box top rail. Not as clean, but easier access. Both battery and controller box are siliconed, so ip67.

Clever display/control interface; is it waterproof? I assume it's like some of the ones i've seen here and there that you rotate the outer edge for changing input, push down for "select" (either the whole surface or just one spot on the edge like a cursor pad), etc.?

Display is nowhere near waterproof. It's ip55 at best, but the pcb could easily be potted and the amoled is casted, so ip67. So far rainy test runs worked but I suspect in heavy rainfall the encoder might behave strangely.

I see the headlight and taillight--does the tail do brake light duty as well? Are there turn signals?

Turn signal can be mounted on the seat though after seeing how quickly they get ripped off on a van raam, I went without. There is a spare wire left for brake duty, but I did not solder a second LED in the taillight yet.

One thought about the taillight: In my experience, having the light as close to driver eye level (for following traffic), or at least the level of the average vehicle rear lighting, makes it more certain they pay attention to it. As large a surface area as possible helps them react more quickly as it makes you appear closer, and/or larger, both of which put you into the category of "things to pay attention to now and not dismiss" for the purely reactive brain used for such things. Brightness isn't nearly as important as size, for this.

True. I only have two cross bars on the seat to mount the backlight; the upper one is better for visibility, but in my experience it's also one of the best "handle" to grab the bike which would break the led - hence the lower mounting. It's still a whopping 30cm higher than on conventional 28" bikes! I think the best solution is a led on the back of your helmet!

The latter applies to the headlight also, for people coming out of driveways, etc., to make them pause longer as you approach instead of dismissing you as too far away or too small to worry about, and just going anyway even though you are actually right there. :/ But the taillight size and placement is more important.

 

[PaPaSteve]

Always a joy to see someone's personal project done so well.
Big thumbs up.

 

[qwerkus]

Always a joy to see someone's personal project done so well.
Big thumbs up.

Cool - thanks!

 

[neptronix]

Okay so great cornering but you have a front-rear weight balance problem probably as a result of putting the pedals so far backwards and sitting so far backwards.

Maybe it only takes 1-2 inches of rear wheelbase to fix that if it's a substantial problem.

 

[qwerkus]

Okay so great cornering but you have a front-rear weight balance problem probably as a result of putting the pedals so far backwards and sitting so far backwards.

Maybe it only takes 1-2 inches of rear wheelbase to fix that if it's a substantial problem.

Wouldn't call it a problem since it's WAD. In comparison to other semis I've ridden, this one has actually better unloaded front traction, mainly thanks to the optimized battery placement, but it's loaded where this bike really shines. One of the main points of this design was precisely to re-balance a clwb by putting all cargo on top of the front wheel instead of the usual rack behind the seat: it allows for a shorter wheelbase while still improving stability and handling.

 

[Epithemeus]

This bike is basically my dream bike (well, dream bike for solo riding without my kid) The amount of TLC in the build is just incredible.

One teeny question, isn't the front light really low to the ground and potentially covered by luggage on the rack? I'd worry about it not being visible enough. I personally would move it up to the handlebars. Maybe that's just my paranoid brain though.

 

[afzal]

law changed here, and now throttles are allowed up to 22km/h

Where is here?

 

[qwerkus]

This bike is basically my dream bike (well, dream bike for solo riding without my kid) The amount of TLC in the build is just incredible.

One teeny question, isn't the front light really low to the ground and potentially covered by luggage on the rack? I'd worry about it not being visible enough. I personally would move it up to the handlebars. Maybe that's just my paranoid brain though.

Where I live, blending leds from cyclist and motorcyclist are a real issue, hence the front led placement. Also it's well protected there so no risk of accidentally breaking or ripping it off. I also basically rebuilt the light using a quality cree led and most importantly a dc power module with adjustable output, so I can tweak manually the luminosity, it can go all the way to 360lm but I don't need it. The cable is a simple 3 wire one with +, - and backlight so you can easily swap it with a longer one and place the frontlight on the handlebar or where ever you want.

 

[qwerkus]

Where is here?

CH and EU

 

[Epithemeus]

also basically rebuilt the light using a quality cree led and most importantly a dc power module with adjustable output

Lol, this does not surprise me at all. Is there any part of this bike you haven't customized/tweaked? Amazing

 

[SlowCo]

Nice bike build. Looks somewhat like the Gazelle Easy Glider I have.

 

[qwerkus]

Nice bike build. Looks somewhat like the Gazelle Easy Glider I have.

How do you like it ? It's actually one of the rides I considered, but there where too many issues, starting with the awkward riding position somewhere between a semi and an upright bike. If it had been easier to properly motorized and add a front rack, it would have saved me a lot of troubles !
This niche bike in germany was one of my inspiration source as well: atl-Modelle | Alltagslieger von Radnabel
Tried it and found the riding position much better, though the lack of backrest was a problem.

 

[maiz]

This niche bike in germany was one of my inspiration source as well: atl-Modelle | Alltagslieger von Radnabel
Tried it and found the riding

These are amazing!

 

[qwerkus]

These are amazing!

Yes, but not very open to changes unfortunately for me

 

[Papa]

This niche bike in germany was one of my inspiration source as well: atl-Modelle | Alltagslieger von Radnabel
Tried it and found the riding position much better, though the lack of backrest was a problem.

 

[A-DamW]

The electric part took longer than expected: while the battery was no real issue since I designed the frame to clamp it down, the vesc controller proved more of a challenge. Like many here know, the key problem is the display. You can write a custom lispBM script to communicate with almost all chinese ebike displays available, but those are often sluggish and don't show the information you need. So again I started from scratch and programmed my own display. Luckily there are plenty of knob style displays available nowadays with decent screens so I picked the best amoled with a reasonable size and coded an lvgl based gui: looks good and is very reactive. Also, it allows for CANbus or uart communication which might come in handy, and since it packs an esp32s3, future possibilites include OTA and remote control of the vesc.

This whole project is a beautiful display of craftsmanship and engineering!

I am especially interested in the vesc compatible display, are you open sourcing the code?

 

[qwerkus]

This whole project is a beautiful display of craftsmanship and engineering!

I am especially interested in the vesc compatible display, are you open sourcing the code?

Depends: I'm trying to find partners to commercialize the bike and the display is one of the things I can bring to the table. If it doesn't work out, or if they don't care, I'm going to publish it on github under gpl3 for sure. The matching lisp code is already available on the vesc discord.

 

[qwerkus]

Already working on a version 2.0. The goal is to make it cheaper, so I ditched the suspension fork and went with larger 20x3" tires. According to my experience so far, the weight imbalance on this design only requires a front suspension travel of around 20mm, which should be doable with tires alone, at least up to 33km/h. I'm not designing fast bikes anyway.

Ditching the suspension fork allows for a rework of the handling: I can use a steeper angle which in turn will significantly reduce sag and front wheel backlash.

Also simplified the swingarm axle design, so this model could work with dual chains, and a short chainguard on the front.

The main element I'm still unsure about is the motor: DDs are great but heavy and very inefficient in dense traffic. You need long open lanes at higher speeds to reach optimal rpm, so I'm considering going either geared hub, or mid drive for the next prototype.

 

[amberwolf]

The main element I'm still unsure about is the motor: DDs are great but heavy and very inefficient in dense traffic. You need long open lanes at higher speeds to reach optimal rpm, so I'm considering going either geared hub, or mid drive for the next prototype.

Some thoughts: In my limited experience with the GMAC in a 20" wheel, vs a couple of Fusins and an Ezee in 26" wheels, the noise at the higher RPMs the motor has to spin in a smaller wheel can be....annoying. Above a few MPH it got pretty loud, and was, for me, nearly intolerable at 20MPH.****

It gives more torque for less (wasted) power this way, and does so for more of the speed/torque curve, vs a winding of the motor that spins proportionally slower to give the same wheelspeed...but at the cost of more noise the closer you get to the full wheel speed.

This was with a phaserunner, so it wasn't controller noise, just gear noise. Packing the gear area of the case with grease didn't change it significantly; it might make a difference if it was completely grease filled to dampen casing vibrations, but that would also fill the motor with grease; never tested a motor that way, suspect there would be leakage thru the usual places oil also gets out.

There are motors with quieter gears, like the few with helical ones (I think there's a Shengyi like this?) but I have no experience with them.


A DD motor can be quieter but will take more power at startups from a stop, so frequent stop/starts in traffic will take more battery to do the same thing.


A middrive, if running thru a correctly shifted pedal drivetrain, could be quieter, as long as the drive itself is designed that way to start with and not running a teeny tiny motor thru a high reduction noisy geartrain, and some of them also use helical gears that would be quieter.

However...the design of the frame may preclude a number of such drives that fit on the BB; you'd have to check on that.




****but I'm not normal (autistic, among other issues), so many people might not be bothered by it, or not as much so, as I was.

 

[qwerkus]

Some thoughts: In my limited experience with the GMAC in a 20" wheel, vs a couple of Fusins and an Ezee in 26" wheels, the noise at the higher RPMs the motor has to spin in a smaller wheel can be....annoying. Above a few MPH it got pretty loud, and was, for me, nearly intolerable at 20MPH.****

It gives more torque for less (wasted) power this way, and does so for more of the speed/torque curve, vs a winding of the motor that spins proportionally slower to give the same wheelspeed...but at the cost of more noise the closer you get to the full wheel speed.

This was with a phaserunner, so it wasn't controller noise, just gear noise. Packing the gear area of the case with grease didn't change it significantly; it might make a difference if it was completely grease filled to dampen casing vibrations, but that would also fill the motor with grease; never tested a motor that way, suspect there would be leakage thru the usual places oil also gets out.

There are motors with quieter gears, like the few with helical ones (I think there's a Shengyi like this?) but I have no experience with them.


A DD motor can be quieter but will take more power at startups from a stop, so frequent stop/starts in traffic will take more battery to do the same thing.


A middrive, if running thru a correctly shifted pedal drivetrain, could be quieter, as long as the drive itself is designed that way to start with and not running a teeny tiny motor thru a high reduction noisy geartrain, and some of them also use helical gears that would be quieter.

However...the design of the frame may preclude a number of such drives that fit on the BB; you'd have to check on that.




****but I'm not normal (autistic, among other issues), so many people might not be bothered by it, or not as much so, as I was.

True that geared hubs can be quit loud in small wheels; even the x1 from shengyi in a 16" wheel is very loud in my experience. In terms of quietness and robustness, nothing beats a DD hub. They are just soooo heavy. And the GAA is too expensive for a series. What I need for this bike is an affordable frame-integrated open source mid drives in my opinion - maybe like the m600 with a vesc controller.