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E-Bike Conversion Kit

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(@lonksheep)
Posts: 2
New Member
Topic starter
 

Companies like ARRC and Swytch charge huge sums for self fit kits to convert your normal bike to an E-bike. 

I cannot wrap my head around £1900 that is asked for these. It’s cheaper to just buy an e-bike… so I feel this is a great topic for a full DIY job… and hoping this may generate some thoughts and ideas.

The ARRC uses standard Bosch rechargeable batteries.

 

there then just needs to be a new front wheel with a motor? 

a controller

 

and a sensor on the pedals. 

is this such a difficult project?? 

 
Posted : 01/04/2024 8:37 am
marcdraco
(@marcdraco)
Posts: 476
Member
 

Welcome to the forum and sorry this has escaped at least my attention. We only have one person to sort through the mass of spam (that we don't see) that comes in daily from "new" users. 

Difficulty depends in your skill level. The electronics aren't all that difficult because of pre-made control units, sensors and such. Quite a few makers have built them.

There are a few Chinese makers selling complete kits for around £250-£300 last I looked. That was a front hub motor, throttle (throttle?!) battery and control. 

The simplest one is the Rubbee which drives the tyre from the outer rim. Probably kill the tyres, but it's easy to fit.

I followed Swytch "this is a Swytchbike" from day one and did they pull the wool over our eyes! As you say the price was "it's HOW MUCH!?" - no wonder the creators are smiling in those ads.

I think Swytch is aiming at the high-end market, people who have ultralight combo and mountain bikes. I don't see much point on a road bike.

FITTING

There are three mounting options (if we ignore the stealth mods that run down the frame, yes they exist!). 

  • Front hub
    • Light, responsive and easy to fit.
    • Downsides include is the question of reliability as it takes a lot of hammer from the front wheel impacting kerbs or pot holes.
    • Most are throttle controlled so might be illegal to use in some parts of the world due to maximum speed regulations.
  • Rear hub
    • Similar weight but you'll need to remove the gear cassette or replace it entirely.
    • Seem to be the superior kits are the ones that come with a speed control but I haven't looked closely.
    • Superior balance compared to the front hub.
  • Pedals
    •  Best balance as the weight keeps the C of G close to the rider. (I nearly wrote driver then!)
    • Not really practical for home building.

Given these factors I would think that the rear axel version would be most suitable for this community although I would suggest someone tracks down a decent kit with a limiter.


Take everything I say with a pinch of salt, I might be wrong!

 
Posted : 17/04/2024 3:34 pm
(@lonksheep)
Posts: 2
New Member
Topic starter
 

@marcdraco great breakdown and I would class myself as a gifted novice. Not afraid to try and fail as that’s the best way to learn.

I’m considering taking each of those elements and building my own ‘kit’. Once I’ve got each of those elements working then my approach will be apply that to a mounting solution. 

I’m going to attempt to use some L-ion batteries from some older power tools (in a similar fashion to how ARRC do their kit)

If anyone else has done this or something similar. I’d welcome any further advice, but failing that I’ll post back with how I’m getting on… at some point. 

 
Posted : 17/04/2024 6:44 pm
marcdraco reacted
marcdraco
(@marcdraco)
Posts: 476
Member
 

Posted by: @lonksheep

@marcdraco great breakdown and I would class myself as a gifted novice. Not afraid to try and fail as that’s the best way to learn.

I would agree. If you've seen the fight I've been having trying to improve on Matt's "ultimate USB3 mic" you'll note how many times I've blown it. Usually by trusting solutions I didn't really understand (because I'm lazy...) and got repeatedly bitten on my rather ample backside. 😉 I'm only risking my beer money of course.

The upside (apart from honing my own skills and being forced to learn new ones such as SMD PCBs, KiCAD etc.) is I've developed a bunch of different solutions. The "best" ones are being manufactured right now, ranging from a 5V USB supply to a full "professional" p48.

Including a "universal" JFET head for many professional capsules. 

When the SCOTUS is done arguing presidential immunity, I'm building a test unit to adapt the appalling digital desktop mic (using it as a shell). Crucially, it's very simple.

Posted by: @lonksheep

I’m considering taking each of those elements and building my own ‘kit’. Once I’ve got each of those elements working then my approach will be apply that to a mounting solution. 

I’m going to attempt to use some L-ion batteries from some older power tools (in a similar fashion to how ARRC do their kit)

If anyone else has done this or something similar. I’d welcome any further advice, but failing that I’ll post back with how I’m getting on… at some point. 

Some students I've heard have used "Roadside LiOn cells" (from discarded vapes) and other have gone 48V and even higher voltage to produce e-bikes (*and scooter) that range from the modest to the illegal in most of Europe. (I don't agree with the 15 mph limit but it's what we have).

Most of this is pretty straightforward with a couple of "gotchas".

You're probably aware that it's the current that makes the motor go. The voltage is important for a different reason, but the current drain calls for some heavy, multi-core cables. I don't know the exact specifications, but that should be clear from the motor's specification.

Front motors (like that hideously overpriced "Swytch Bike" because it's more expensive to convert many everyday machines than just buy one off the peg as it were.

I assume you're going to buy a pre-made controller. I've done a little bit of work with high I controllers, all thanks to the wonderful power MOSFET. (Everyday bipolar power transistors just can't do this because they can't pull the collector and emitter close enough to each other. MOSFETs have such a low Ron (often a fraction of an ohm) far less power is lost to heat in the MOSFET (or bank of MOSFETs).

Ali seems to have a decent selection of pre-made units from street legal to HOOOOLLY COOOOOW (5000w) beasts that could destroy even the best e-bike tyres.

Ebike Controller - Controller - AliExpress

Tyres (and brakes) need to be able to cope with the huge amount of power and extra weight, which likely means pneumatic disc brakes.

But for those people who are more interested in going fast rather than stopping (holds hands up in shame) it's vital to get tyres that can take the speed AND the torque. E-Bikes are so powerful they are quite capable of twisting a tyre clean off the rim. Speed also brings the spectre of heat - and that means the internal pressure increases potentially causing a tyre to blow during use. 

 

 


Take everything I say with a pinch of salt, I might be wrong!

 
Posted : 25/04/2024 4:00 pm