[HN Gopher] A DIY E-bike Conversion on the Cheap
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A DIY E-bike Conversion on the Cheap
Author : PikelEmi
Score : 79 points
Date : 2021-08-22 20:55 UTC (2 hours ago)
(HTM) web link (spectrum.ieee.org)
(TXT) w3m dump (spectrum.ieee.org)
| soared wrote:
| I like nerds but man is it out of touch/socially awkward to
| posture based on how often you use the front brake and link to a
| decades old blog post doing the same.
| isoskeles wrote:
| Why is it socially awkward to link to an old resource? As far
| as I can tell, Sheldon Brown's blog is a fairly well-known
| resource, and it is frequently linked on other biking forums.
| bserge wrote:
| Could use two of those to turn the wheel by the aluminum rim
| (same one used by the brakes). More power, more traction, less
| dirt.
| mongol wrote:
| Cool to share battery with a lawnmover. Seems clever to share
| parts between appliances.
| bserge wrote:
| 400 Euros is all it takes for a 500W battery, 500W+ direct drive
| motor E-Bike conversion.
|
| 200 Euros just for the battery pack. And we're not talking some
| shit 7Ah pack that will last half an hour. An hour at full power
| is the minimum, anything else is unacceptable.
|
| Whether used for constant speed, acceleration only or pedal
| assist, what's the point of an E-Bike that's deadweight after
| less than an hour?
|
| I actually have made a design using a 1KW brushed motor that
| replaces the pedals and uses the hub gear. It is cheaper, but
| harder to install (needs at least a custom frame for the motor)
| and is illegal on bike lanes as the pedals are removed. Could
| share it if anyone cares.
| IkmoIkmo wrote:
| > Whether used for constant speed, acceleration only or pedal
| assist, what's the point of an E-Bike that's deadweight after
| less than an hour?
|
| I'd like to see some data on power usage for different
| percentages of user-assist for people doing average biking
| speeds. e.g. 25% of total power being motorised/assisted, the
| other 75% being human-powered, on average.
|
| After all, using it at full power always isn't a bicycle, it's
| a motorcycle. The idea of e-bikes is to assist the user, on
| accelerating from a stoplight, on a hill, after a break, in a
| particularly strong gust of wind. At these short moments assist
| can be >90%, but when you're at speed it can be say <10%,
| averaging to perhaps 25%. The assist can be higher on warm days
| to prevent them becoming too sweaty days, but it'll still be to
| assist regular biking.
|
| But yeah less than an hour is not really acceptable, I agree.
| Unless there's some kind of ubiquitous and convenient charging
| infrastructure, but I don't see that happening anytime soon.
| bserge wrote:
| Well, yeah, but it's a quiet electric motorcycle. Once you
| get used to just a hand throttle and zero pedalling (keep
| that as a backup and for legality on bike lanes), you may not
| want to go back heh.
| bambax wrote:
| Exactly. TFA is disingenuous since the author repurposes a
| battery from their lawnmower. A basic standard ebike conversion
| kit, with battery and a central motor, starts at EUR400.
| milesvp wrote:
| A word of warning. I started looking a little into motor assist
| bike mods a few years ago, and very quickly you find that the
| biggest mistake people make in this area is not altering any of
| the other systems of the bike. That is, they'll put in the motor,
| and then just ride. Which works, but then you find that your
| brakes aren't quite good enough to stop quickly at the new higher
| speeds. Shocks are no longer good enough to prevent certain
| issues as well. Maybe the frame needs reinforcing... I don't
| quite remember the whole laundry list.
|
| I don't know how important some of these improvements are, I just
| remember reading this advice more than once, and safety is
| important. So be smart and do your research.
| bambax wrote:
| I made an ebike from a brand new Decathlon "rockrider" MTB 3
| years ago, and have ridden about 10k km on it since. I changed
| brake pads often, and tires a couple of times, etc. but the
| frame is fine.
|
| It's really life changing. I used to ride a motorcycle, and I
| still own one, but I seldom use it anymore; the ebike is
| absolutely perfect for short commutes (under 20 km each way).
|
| That said, complete ebikes are more available now, and at good
| prices, so conversion kits are becoming less relevant.
| treis wrote:
| I think ebike is a misnomer. These things are really
| e-(motor)cycles. This confusion is making it really hard for me
| to search for what I need. All I want is an assist to take the
| edge off of hills. Don't need to cruise at 30mph for an hour.
| bootlooped wrote:
| I think the phrase e-bike generally refers to a bicycle, with
| operable pedals, that also has an electric motor to assist
| when peddling, and possibly a throttle.
|
| When I think electric motorcycle, I think of something that
| does not have pedals at all.
| ZeroGravitas wrote:
| EPAC or Pedelec is a term used for bikes that meet the EU
| regulations, assist should cut off beyond 25kph (15.5mph) and
| you only get power when you cycle. I think there's a motor
| wattage maximum too so that might help your search.
| treis wrote:
| Those seem to be the magic words to find what I'm looking
| for, thanks!
| kylegordon wrote:
| yup, and 250W continuous
|
| And the great bit is that if you are ignorant of these laws
| and get caught on an electric bike doing higher speeds then
| you get a penalty as if you are riding a motorbike without
| insurance or a license - aka penalty points on your regular
| driving license, plus all the other court shenanigans.
| germinalphrase wrote:
| Search for a 750 watt motor. That is the upper limit in many
| countries for a standard commercial ebike. Bafang and
| Tongsheng both produce popular motors.
| treis wrote:
| Google says those cruise at ~30mph.
| 1-more wrote:
| You can get really nerdy and calculate this the way
| triathletes/time trialists do with a tool like this[0]. I
| plugged in what I think my numbers are for mass and my
| relaxed ride CdA and on my road bike and you're on the
| money.
|
| [0] http://www.aeroweenie.com/calc.html
| calvinmorrison wrote:
| #1 rule people forget is: how fast can you stop. You see it
| with young car guys vs old ones. Old dudes upgrade the brakes
| before the turbo and visa versa
| tyingq wrote:
| Some of that may be because brakes on old cars (drum brakes,
| undersized discs, etc) were often terrible. I think stock
| brakes have been quite good on most cars in the last 15 years
| or so.
|
| For example, a 2021 Chevy Surburban is a HUGE SUV, but does
| 70mph-0 in 166 feet. Better than a 1999 Camaro Z28 or Mustang
| GT, at 184 and 182 feet, respectively.
| mrfusion wrote:
| Are those numbers with threshold braking or engaging the
| ABS?
| asdff wrote:
| If you limit yourself to like 25mph thats a nonissue though,
| all bikes are built to handle that speed.
| IgorPartola wrote:
| Before you get on one of these, it's good to check your
| perspective on safety: https://youtu.be/wM8Xli2KTzI
|
| As a motorcyclist, electric bicycles make me very nervous.
| dharmab wrote:
| The same channel proposed using a similar kit with a donor
| motorcycle. You get the advantage of a stronger frame, better
| brakes and better tires:
| https://www.youtube.com/watch?v=O2zlYpy6QCM&t=300s
| corney91 wrote:
| This guy is wrong when he says the UK "has a culture of
| commuting on two wheels." We have a huge problem with cycle
| infrastructure, as evidenced by the stats he presents. Ok,
| London's probably decent but transport everywhere else in the
| country is built around cars.
| dharmab wrote:
| Compared to Canada (where Fortnine mostly films), anywhere in
| the UK is cycling heaven.
| corney91 wrote:
| Picking a country like the UK who have stats available
| would be fine then, but suggesting it's a better case
| scenario with that comment about culture is just trying to
| skew the conclusion. It doesn't help that the stats show a
| massive difference in injuries/deaths as well. By all
| means, everyone should choose your favoured transport, but
| the video really seems like FUD.
| 1-more wrote:
| It's kind of a thing for me as a cyclist. Like I had to get
| good at handling a bike every speed slowly because I didn't get
| faster overnight, I didn't just go walking to 40 overnight.
| IgorPartola wrote:
| It's not just about how fast you are going. When you drive a
| car, do you look out for pedestrians running at 40? Would you
| be surprised if one showed up in front of you? Now imagine
| the same thing with a bicycle.
| 1-more wrote:
| Wait you lost me. Is the cyclist the pedestrian or the
| motorist in this scenario?
| ohmaigad wrote:
| Somewhat irrelevant in places where motor assist is limited to
| 25kph (EU for example).
| NietTim wrote:
| If the builder of a DIY bike choses to adhere to that....
| ohmaigad wrote:
| But that is not an issue with e-bikes as a whole (it is
| also illegal and fineable in places where restrictions
| apply).
| nsxwolf wrote:
| I wouldn't want to go faster. 15 mph is probably faster than
| I've ever gone.
| wikidani wrote:
| I wouldn't worry too much, I have routinely done about
| 50-60 km/h on a motorized bike and had 0 issues. Always had
| the best disk brakes I could buy though.
| IgorPartola wrote:
| Anekdata doesn't prove much here. Some things you might
| not be considering:
|
| 1. At 60 km/h you are going the speed of a car but car
| drivers don't expect you to be going that fast and as a
| result aren't wired to look for you. Doesn't matter how
| fast you were going when a car going 60-90 km/h didn't
| see you and ran you over.
|
| 2. Brakes are only half the equation. If your tires start
| slipping your brakes will lock up and then you go splat.
|
| 3. If you do happen to get off at 60 km/h you will have
| road rash that will take off large chunks of skin even if
| you wear an armored jacket and armored gloves. In spandex
| you'll be looking like Deadpool pretty quickly.
|
| 4. Your tires will heat up pretty quickly at these
| speeds. That will affect how they handle quite a bit.
| [deleted]
| c6401 wrote:
| I kind of think that the difference between electric bike and
| motorcycle is that electric bike ideally should be used on bike
| lanes within speed limit. So if the intention behind making an
| e-bike is to use it like a motorcycle then yes, motorcycle will
| be safer. But if the intention is to use it as a bicycle, using
| bicycle infrastructure (which arguably is very limited in
| America unlike how things are in Europe) at bicycle speeds but
| just without coming to your job covered with sweat then
| bicycles are safe.
| 8jef wrote:
| That's a great hack. But I'm a big guy, bordering on 285lbs. That
| kind of low power traction doesn't seem enough to move me. I know
| European 250w motors are never enough for me.
|
| I've build my first ebike a few months ago. I went for a 1000w
| Bafang mid drive geared motor with a 48v 20a battery, on an old
| used Peugeot mountain bike. Adding some new/used bike parts
| (wheels, tires, chain and rear gear), total project cost arrived
| at C$1800, less than half the price of a new ebike with similar
| specs.
|
| Considering my weight, 20 to 23 kph is my speed of choice in
| pedal assist mode, which is quite safe. It does extends my range
| a lot compared to other use cases.
| shimonabi wrote:
| Very interesting. I would love to see a video where someone does
| it from start to finish.
|
| I would also like to make my own battery for the bike. I made a
| cheap DIY spot-welder from a microwave transformer and spot-
| welded my first 12V 20 Ah battery last week for a 3d printed
| robot lawn-mower project.
| _Microft wrote:
| Building the battery pack yourself would give flexibility
| regarding size and shape of the battery pack. Maybe you could
| put them inside the seat tube?
| thoughtpalette wrote:
| Cool project. Would love a list of part URLs + repos to get set
| up. Wouldn't mind tinkering with something like this as a getting
| started guide.
| axx wrote:
| It would be quite interesting to see how these "tire contact"
| motors will perform once it starts raining or your tires get
| really dirty.
|
| I think there is a reason, why crank or hub located motors are
| the norm now.
| 1024core wrote:
| > I was able to come up with an e-bike conversion that cost me
| less than US $200 and yet functions impressively.
|
| ... excluding the cost of the battery. The battery costs $150 in
| HomeDepot
| nynx wrote:
| Having the motor casing drive the edge of the wheel is clever
| since it provides the necessary mechanical advantage without
| gearing.
| Someone wrote:
| _"While it would have been nice to engineer some sort of
| spring-driven mechanism to control how forcefully the motor
| pushes against the tire, I kept things simple: I just deflated
| the tire somewhat, bolted the motor solidly in place, and
| reinflated the tire."_
|
| I think Solex (https://en.wikipedia.org/wiki/VeloSoleX) did
| that better.
|
| It uses the weight of the engine to press the powered wheel to
| the bicycle wheel, accounting for variation in wheel diameter
| due to tire pressure or tire wear. This could use the weight of
| the battery pack
| wikidani wrote:
| Interesting, but to be completely honest, I think a two stroke
| motorized bike is better and a lot more fun to build
| nynx wrote:
| A motorized "bike" is loud, smelly, expensive, much worse for
| the environment, and bad for your respiratory system.
| bserge wrote:
| Lol at the downvotes, but yeah, nothing beats that for energy
| density. Could even carry a 1L bottle of petrol with you or
| something.
|
| They're loud as hell and illegal in some places, though.
| eigenspace wrote:
| I'm actually a little curious about how great the practical
| energy density would be in this case with a 2-stroke engine
| compared to a modern lithium ion battery and motor. 2 stroke
| engines are pretty famously inefficient, expelling quite a
| bit of unburned fuel.
|
| That and I'd guess that the engine itself is pretty bulky
| compared to the electric motor, so the total bulk might even
| out compared to an electric setup for the same amount of
| energy, but I'd have to look at the actual numbers.
| eigenspace wrote:
| I live next to a bike lane, and there's a few assholes with
| two-stroke motorized bikes who use that bikelane regularly. I
| absolutely hate it, they make so much noise.
|
| I hope the police catch them and take their bikes away.
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