/ Building an electric bike

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The Wild Scallion 17 Jan 2020

Good morning UKC

I've decided to sell one of my TT/Road bikes and invest the cash in building an electric mtb .

It seemed a sensible choice as it combines 2 things I love , namely electronics and bicycles .  Also I don't need 2 TT bikes , In fact I might sell both anyway.

Has anyone else built their own ? 

I have an 48 volt rear wheel and the controllers so far . 

I'm just now looking for either a new cheaper bike to convert or a second hand mtb from somewhere to use.

TWS

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WaterMonkey 17 Jan 2020
In reply to The Wild Scallion:

A mate at work built one. He can do 47mph without pedalling now!

He carries the batteries in a rucksack and has to keep the top unzipped to aid with cooling.

It's like the start of casualty or London's burning when you see him leave!

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Rigid Raider 17 Jan 2020
In reply to The Wild Scallion:

No, electric is vulgar and arriviste. Steam is what you need:

https://www.youtube.com/watch?v=yvS8wtnNQz4

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The Wild Scallion 17 Jan 2020
In reply to WaterMonkey:

> A mate at work built one. He can do 47mph without pedalling now!

> He carries the batteries in a rucksack and has to keep the top unzipped to aid with cooling.

> It's like the start of casualty or London's burning when you see him leave!

I've gone for the slightly less illegal model.   Possibly 35-40 .  If I bypass the limiter

But of course I would do no such thing. Me no .

;-)

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elsewhere 17 Jan 2020
In reply to Rigid Raider:

> No, electric is vulgar and arriviste. Steam is what you need:

Excellent. I wonder if it might be road legal and as what - does a <250W e-bike need to be electric or does steam make it a moped?

Post edited at 11:10
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wintertree 17 Jan 2020
In reply to WaterMonkey:

> A mate at work built one. He can do 47mph without pedalling now

Beware the law.  Many “do it yourself” kits are wilfully non compliant with the law and certain online marketplaces facilitate their sale without a care in the world.

The bike as you describe opens your mate up to charges of driving without insurance, driving without an MOT, driving without tax (even if it would be free it’s a crime not to do it), and potentially driving without a valid class of licence.  All of which added together could price them out of their motor insurance (if they hold any) and be a problem for some employment, as well as potentially leading to a confiscation of their driving licence.

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LastBoyScout 17 Jan 2020
In reply to WaterMonkey:

> A mate at work built one. He can do 47mph without pedalling now!

> He carries the batteries in a rucksack and has to keep the top unzipped to aid with cooling.

> It's like the start of casualty or London's burning when you see him leave!

15.5mph pedal assist is the legal limit for a bicycle - any more than that, or if it has a separate throttle, and it's classed as an e-moped/e-motorbike with all the legal requirements they come with, as stated by Wintertree.

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Swig 17 Jan 2020
In reply to LastBoyScout:

Yes, 15.5 is a frustrating speed! I borrowed an e-MTB from the local bike shop and spinning along on a flat track and roads on the way back found I couldn't pedal slowly/gently enough to get assist even though I was tired and would have been happy to fully drain the battery having a gentle roll home. 

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WaterMonkey 17 Jan 2020
In reply to LastBoyScout and Wintertree:

Yes, yes he's aware of all that.

To be fair the government is miles behind in terms of allowing suitable electric transport. There's a girl I see every morning and she rides an electric scooter along the path, again illegal.

I'd be tempted to get a Segway or electric skateboard or something to go to work on but again the government haven't woken up yet.

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LastBoyScout 17 Jan 2020
In reply to WaterMonkey:

> Yes, yes he's aware of all that.

So why is he doing it, then?

> To be fair the government is miles behind in terms of allowing suitable electric transport. There's a girl I see every morning and she rides an electric scooter along the path, again illegal.
> I'd be tempted to get a Segway or electric skateboard or something to go to work on but again the government haven't woken up yet.

They may well be, but, until they go through the process and change the law, it's still illegal.

I've seen a few people on electric scooters and a couple of clearly illegal bike conversions around here, one of which is a Deliveroo rider with a small petrol engine bolted on!

So far, there's been 1 e-scooter fatality and 1 (legal) e-bike collision fatality I'm aware of:

https://www.theguardian.com/uk-news/2019/jul/13/tv-presenter-emily-hartridge-dies-in-scooter-crash

https://www.theguardian.com/uk-news/2018/sep/14/e-bike-crash-death-prompts-debate-over-safety-on-uk-roads

The first story has a link to the Government's regulatory review to include the ideas.

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WaterMonkey 17 Jan 2020
In reply to LastBoyScout:

> So why is he doing it, then?

I don’t know you’d have to ask him. I suspect it’s because he isn’t motivated or in good enough health to cycle and doesn’t think driving an engine powered machine to work and back is justifiable.

Have you honestly never done something you know is illegal?

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LastBoyScout 17 Jan 2020
In reply to WaterMonkey:

> Have you honestly never done something you know is illegal?

Of course I have, but riding an obviously illegal bike at 47mph on a public road seems a good way of drawing attention to yourself, quite apart from the danger to yourself and others.

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WaterMonkey 17 Jan 2020
In reply to LastBoyScout:

> Of course I have, but riding an obviously illegal bike at 47mph on a public road seems a good way of drawing attention to yourself, quite apart from the danger to yourself and others.


I tend to agree. It’s quite a big fast road though, 40mph limit, with most vehicles going faster. It’s annoying when I’m cycling and he comes past not even pedalling! 
 

I do think he’ll come a cropper one day. He’s already had chains and hubs fail. Hopefully he doesn’t hurt anyone else.

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L NERD 18 Jan 2020
In reply to The Wild Scallion:

I converted my mountain bike with a 1000w cyclotricity hub. The hub was pretty awesome, lots of torque and power and I could spin out around 30mph with fat tyres. The problem was the hub had much more resistance than a normal hub and the bike was at least twice as heavy. So riding anything other than downhill felt like uphill. This meant I hammered the battery all the time and the battery died in an hour. Would have been great for a ten mile off road commute to work but not much else. This was a midrange 14amp battery. 

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artif 19 Jan 2020
In reply to The Wild Scallion:

Interesting project, but where are you going to use it. If you stuck a petrol motor on a mountain bike the hordes would be in uproar if you rode it on bridleways but an e motor on a bike seems to get a free pass.

Electric or petrol it's still motorised, so you'd be restricted to Byways (BOATS) that require registration insurance, tax mot etc. 

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Martin W 19 Jan 2020
In reply to LastBoyScout:

> So far, there's been 1 e-scooter fatality and 1 (legal) e-bike collision fatality I'm aware of

I think that at the moment it's not clear that e-bike was legal (as in, it met the EAPC rules).  The rider is being prosecuted for causing death by dangerous driving, which AIUI would only be possible if the e-bike was actually classed as a motor vehicle:

https://road.cc/content/news/267863-london-e-bike-rider-court-accused-causing-death-pedestrian-dangerous-driving

Will be worth keeping an eye out for the reports of the case when it comes up (due to be heard 24th Feb).

Of course, saying that an e-bike that's not compliant with the EAPC rules is illegal isn't strictly correct: so long as it has been type approved, is registered and taxed, and the rider has the appropriate license, insurance and is wearing a motorcycle helmet then it's fine...

Post edited at 18:03
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The Wild Scallion 20 Jan 2020
In reply to The Wild Scallion:

Further to this project,  this weekend I  brought at cheap but fully featured mountain bike from the shops and converted it to an e bike .

Just ordered the battery today so I should be able to give it a whirl by next weekend if not before.

In answer to the questions about what I intend to do with it . I fitted a switch to the limiter cable for the pedal assist so I can switch it between road use and off road use.

Should make my commute more pleasant when I don't feel so sprightly. 

I intend to upgrade to a more substantial bike when I can source one suitable .

TWS

Post edited at 08:29
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Rigid Raider 20 Jan 2020
In reply to The Wild Scallion:

I wonder how different this discussion would be if the size and capacity of batteries wasn't a limitation?

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jkarran 20 Jan 2020
In reply to The Wild Scallion:

e-bike legislation is a rather unclear barrier to cleaning up our personal transport but while that's true it's still worth bearing in mind. It's hard at the moment, despite the fact most I see around here are clearly non-compliant and plenty ridden poorly, to imagine a proactive crackdown on them but if you find yourself in conflict with someone else you may have to defend the design and product choices you make.

Personally I'd like to see a rise in the pedal assist unlicensed e-bike speed limit to 20-22mph, impose a vehicle weight and probably age limit, add a requirement for a cycle type helmet and full time lighting.

I'd also like to see the wording clarified. At present it's not at all clear what constitutes pedal assist or whether the 250 legal limit for bicycles is peak or average power, electrical or mechanical, shaft or wheel, whether electronic limiting is acceptable etc etc... Until this is clarified or tested it's a risky business for a small player to get into.

jk

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jkarran 20 Jan 2020
In reply to Rigid Raider:

> I wonder how different this discussion would be if the size and capacity of batteries wasn't a limitation?

Is it really a limitation? If you focus on power you can get roughly two horsepower per Marsbar sized battery from a modern high power lithium polymer battery. For example 5 of these (link below) under 1kg could deliver 10 horsepower electrical without exceeding their continuous power rating, 20 short term! Won't last long (55-25 seconds!) but the power density is absolutely incredible. Or you could go for high energy density and range instead, the performance of the best batteries in this respect is still very impressive.

https://hobbyking.com/en_us/turnigy-bolt-2400mah-3s-11-4v-65-130c-high-voltage-lipoly-pack.html

jk

Post edited at 09:50
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The Wild Scallion 20 Jan 2020
In reply to jkarran:

I've yet to see anyone riding a ebike recklessly personally.

I've seen a fair few out on the hills and around the city centre so I'm not concerned as I don't plan on racing around and drawing attention to myself .

I needed a project to build to distract me from family issues at the moment.

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jkarran 20 Jan 2020
In reply to The Wild Scallion:

> I've yet to see anyone riding a ebike recklessly personally.

Most I see are ridden sensibly by commuters and older folk, most clearly not pedalling yet keeping up with traffic. Personally I don't have a problem with that, good for them and the city, but they're clearly not legal. One old boy has a full size electric moped he rides around, mostly on the pavements. Not so impressed by him!

> I needed a project to build to distract me from family issues at the moment.

Fair enough but do check out the rules though, forewarned is forearmed even if you decide not to comply. I'm pretty sure for example an easily switchable road/off-road limiter is mentioned, and forbidden.

jk

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wintertree 20 Jan 2020
In reply to jkarran:

> I'm pretty sure for example an easily switchable road/off-road limiter is mentioned, and forbidden.

What about a control system with firmware only in RAM that is passive if unprogrammed and an emergency kill switch?  Then any evidence collected is of a system unable to engage itself.  Allegedly this is how a lot of the electronics intelligence stuff on US spy planes is rigged with FPGAs programmed by ground support before takeoff and no non-volatile storage of their programs, and with small explosive charges stuck on anything that has to be non volatile.  That last bit probably isn’t a good idea on a bicycle given modern sensitivities...

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jkarran 20 Jan 2020
In reply to wintertree:

Overkill perhaps Though I'd not rely on the kill switch, it should die if unused in an evidence room if for example you're separated in a crash. I've seen a similar approach recommended for those transiting US airports requiring access to commercially sensitive material. Blank computer, OS on ROM, all data and software stored/run remotely.

I doubt any prosecution for illegal e-bike use would go so far as to extract, against the chip's will, and de-compile the firmware so avoiding all but the most obvious external de-limiter switches in your own design and the application of some sense to your riding is probably all that's needed to avoid legal trouble.

jk

Post edited at 10:22
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Martin W 20 Jan 2020
In reply to jkarran:

> I'm pretty sure for example an easily switchable road/off-road limiter is mentioned, and forbidden.

https://www.cyclinguk.org/cyclists-library/regulations/eapc-regulations

"The Department of Transport say that electric bikes limited to 15.5mph but fitted with off-road switches or modes that, when triggered, enable a bike’s motor to continue assisting to speeds beyond 15.5mph, do not comply with UK e-bike law"

I'm pretty sure that limiting use of a non-EAPC-compliant e-bike to off-road use is not sufficient: as a motor vehicle, it must comply with all applicable regulations to be legally used in any place to which the public have access (you can be done for driving offences in a supermarket car park, for example).  Thus a speed pedelec cannot legally be used at an MTB trail centre like Glentress, where the public are free to come and go at any time.  The only place where it would be legal to use would be on private land to which the public do not have open access (hence why you can drive at higher than legal speeds at motor racing circuits, for example: because the public have to pay for access).

> I'd also like to see the wording clarified. At present it's not at all clear what constitutes pedal assist or whether the 250 legal limit for bicycles is peak or average power, electrical or mechanical, shaft or wheel, whether electronic limiting is acceptable

AIUI the regulation specifically defines the power limit as being the maximum rated continuous output power of the electric motor itself (see the link above).

I believe that "pedal assistance" is defined as meaning that the motor cannot provide assistance if the pedals aren't turning.  I don't think it says anything about whether any actual effort should be being exerted through the pedals.  My eMTB provides different settings which adjust the amount of assistance according to the torque exerted through the pedals; the "turbo" mode seems to provide maximum assistance at very low pedal pressure, and is almost uncontrollable on nadgery climbs - it's really only any use for dispatching tedious ascents on boring, straight fire roads.  (The regulations also allow for a small amount of assistance when not being pedalled; I'm pretty sure that this is speed limited to about a moderate walking speed, and only provides assistance when the wheels are turning - the aim is to provide assistance with propelling the bike when you're on foot e.g. pushing it up a hill that you don't fancy trying to ride up even with a motor to help.)

As for the means by which the assistance is limited according to speed, from what I've seen the regulations don't specify this, they simply say that the electric motor should not be able to propel the e-bike at higher than 25kmph.  How that's achieved is up to the designer/builder of the machine.  On my e-bike there's a speed sensor on the rear wheel which seems to both cut the power to the motor and mechanically disengage the drive at 25kmph*.  That means that you don't have to pedal against the motor if you want to go faster.  I quite often glance down at the controller on my handlebars to see that I am happily pedalling along at more than 25kmph without realising it.  Some e-bike owners I know do speak of hitting a "wall" at 25kmph, presumably because their e-bike's system leaves the motor connected in to the drive train so they do have to pedal against the unpowered motor, as well as everything else that takes effort on an unpowered bike, when the limiter cuts in.

* And yes, one of the common ways to de-restrict retail EAPCs used to be to interfere with the speed sensor so that the control system basically thinks that the bike is going slower than it really is.  I think most current EAPC controllers have mechanisms to defeat this rather crude approach to hacking the system.

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wintertree 20 Jan 2020
In reply to Martin W:

> * And yes, one of the common ways to de-restrict retail EAPCs used to be to interfere with the speed sensor so that the control system basically thinks that the bike is going slower than it really is.  I think most current EAPC controllers have mechanisms to defeat this rather crude approach to hacking the system.

Bigger wheels!  EAPF - electrically assisted Penny Farthing

Post edited at 12:25
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L NERD 20 Jan 2020
In reply to The Wild Scallion:

> I've yet to see anyone riding a ebike recklessly personally.

> I've seen a fair few out on the hills and around the city centre so I'm not concerned as I don't plan on racing around and drawing attention to myself .

> I needed a project to build to distract me from family issues at the moment.

I had an LCD on mine and I could set the speed with a few button clicks. On road I'd set the speed to 25kph then when I got to the trails I'd turn it up to 50kph. I never switched modes from 1000w to 250w (although it's pretty easy to do) because you still have to set the speed anyway. 

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jkarran 20 Jan 2020
In reply to Martin W:

Pedals turning does seem to be an accepted norm but it isn't quite the same as pedal assist. It's all very poorly worded (and overly restrictive IMO).

> AIUI the regulation specifically defines the power limit as being the maximum rated continuous output power of the electric motor itself (see the link above).

This is my gripe, a motor conservatively rated at 250W continuous could potentially handle multi kW overloads. In reality all modern systems will be power, torque and speed limited by a combination of their batteries and electronic controllers yet the law talks about the motor as if it's the key component.

jk

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L mondite 20 Jan 2020
In reply to jkarran:

> Personally I'd like to see a rise in the pedal assist unlicensed e-bike speed limit to 20-22mph, impose a vehicle weight and probably age limit, add a requirement for a cycle type helmet and full time lighting.

The primary issue with speed would be any shared paths. Its okay on the road (might actually be a good thing since if they are common drivers might get used to the idea that bicycles can actually move) but on a mixed path you would have a hefty speed mismatch as standard.

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LastBoyScout 20 Jan 2020
In reply to Martin W:

> I think that at the moment it's not clear that e-bike was legal (as in, it met the EAPC rules).  The rider is being prosecuted for causing death by dangerous driving, which AIUI would only be possible if the e-bike was actually classed as a motor vehicle:

> etc

The report I saw said there was no suggestion it was not a legal one.

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LastBoyScout 20 Jan 2020
In reply to Martin W:

> your post

> * And yes, one of the common ways to de-restrict retail EAPCs used to be to interfere with the speed sensor so that the control system basically thinks that the bike is going slower than it really is.  I think most current EAPC controllers have mechanisms to defeat this rather crude approach to hacking the system.

One of the tricks used to be as simple as moving the speed sensor magnet or fitting a second one.

I happened to be in a bike shop at the weekend and chatting with my mechanic friend. We got on to the subject of e-bikes and he was telling me that all of the motors now coming in from the likes of Bosch and so on now include pretty robust software to detect any attempt to de-restrict/fool the motor into producing more power/speed, using things like current speed and output, and shutting off if it's too high. He said one of them allows 3 strikes and then burns out the motor.

So far, he's not aware of anyone managing to hack one, but it's probably only a matter of time.

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LastBoyScout 20 Jan 2020
In reply to jkarran:

> Most I see are ridden sensibly by commuters and older folk, most clearly not pedalling yet keeping up with traffic. Personally I don't have a problem with that, good for them and the city, but they're clearly not legal. One old boy has a full size electric moped he rides around, mostly on the pavements. Not so impressed by him!

I saw a report a recently that said the current highest injury demographic in Netherlands is now older/retired cyclists on e-bikes!

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Howard J 21 Jan 2020
In reply to The Wild Scallion:

The effect of the speed restriction is so that e-bikes can be legally considered to be bicycles rather than motor vehicles, which allows them to be ridden anywhere an ordinary bike can legally go.  That means a road-legal e-bike can be ridden on a bridleway or cycle path.  Since CRoW access doesn't permit cycling, and other other forms of public rights of way are legally roads, it's difficult to think of places you might legally ride a non-compliant e-bike, except maybe on private land to which the public doesn't have access, with the landowner's permission.  

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The Wild Scallion 10 Feb 2020
In reply to The Wild Scallion:

Finally finished the ebike this weekend , after much messing about getting a battery for it.

Took it for a spin on Saturday .  

Wow it's brilliant fun. Very impressed . I've built it all for £525 total cost.

It can be my contribution towards reducing my carbon footprint .

;-D

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