Comment by drcross | Hacker News Reader

Comment by drcross | Hacker News Reader

I have been experimenting with e-bikes over the past few months and converted a standard BMX to an e-bike over the last weekend. They are unbelievably good. You have to try one to understand how much fun they are.

E-bikes have the potential to revolutionize urban transportation, particularly in European cities but we are being stopped here by heavy regulation.

To be road legal in most European cities an e-bike needs to 1. Be less than 250 watts, and: 2. Only work when you are actively pedaling, otherwise it should come to a halt and, 3. Stop powering the user once it reaches 25kmph.

If you break any of those rules you need to have a motorbike license and have the e-bike licensed (which is practically impossible). These restrictions are unnecessary and heavy handed. There should be some flexibility in the law allowing someone to use a low to medium power e-bike without being forced to pedal and being let drive at a reasonable speed. Every bike used is a car off the road. I've written to my local transportation minister who replied to say that they have no intention of changing the law anytime soon which is a real shame.

As a regular rider of a non-ebike, I like the restrictions. It's unnerving to be passed by a silent 25mph (40kph) unlit e-bike on a trail at night. 25kph sounds more reasonable, about the same speed a typical human can bike on a flat road.

Easing the restrictions too much results in near-motorbike performance in trails and bike lanes shared with human powered riders.

> unlit e-bike

Well there we got a easy-to-fix problem. I never turn of the light, and its not like a led bike light is going to A), decrease travel time, B) ruin the environment.

Is there a good reason why the light isn't always on when the ignition (ie key) is turned?

IMO this is evidence of the problem with bikes and ebikes in general. They're not an integrated, complete solution where (like cars) you just turn them on and go. At the moment ebikes are preassembled kits with a standard bike, electric battery and motor, and (if you're lucky) lights added, but most people will have to add their own lights powered by separate batteries, locks, and other accessories.

For the market to really take off there should be a maintenance free, complete solution. One of the many things would be that the lights are integrated to the rest of the electrics.

Also one could imagine removing most of the moving parts of a bike: No chain or gears (use a dynamo and a motor). Steering wheel is probably not needed if you have some kind of electronic self-balancing mechanism (like the Segway). You could arrange the wheels side by side instead of front and back to make the whole machine much smaller. Integrate the bike lock into the bike so you don't have to carry a separate lock, with lock/unlock controlled by your cellphone. Integrate the lights into the chassis and make them work automatically. Fewer moving parts => less maintenance => cheaper to buy and operate.

If you still want it to be reasonably human powered, replacing the chain with a generator+motor is a bad idea. A chain has less than 2% loss, while a motor-generator set will have 10 times or greater losses. Even a few watts of loss from a generator hub is noticable... losing 10 - 20% of power would make the bike nearly unrideable for any significant distance.

I'm not sure how you'd remove the handlebars and still allow steering, one key piece of bicycle steering is counter steering -- you actually steer left to tilt the bike over so you can go to the right. (for gentler turns you can shift your body weight, but if you need to make a sudden turn to avoid an obstacle, you use countersteering)

Likewise, I don't see how you'd have 2 side by side wheels on a "bike" that's designed to go 30mph+, how would you stop quickly without cartwheeling?

I should say I'm envisaging an electric-assist bike so (some) losses would be fine since they are made up by the battery. Of course if it's 10x the loss of a regular bike that could be a problem - I've no idea if your figures are correct or represent the state of the art.

> Likewise, I don't see how you'd have 2 side by side wheels on a "bike" that's designed to go 30mph+, how would you stop quickly without cartwheeling?

I guess you'd stop the motor and the electronic self-balancing would do the rest (in a very hand-waving way, but Segways are an existence proof that something like this is possible, although perhaps not at 30mph).

Here's a chart of a typical electric bike motor efficiency -- peak efficiency is about 85% at 30mph. At 15mph, efficiency is closer to 50%. (that doesn't mean you get greatest range at 30mph since wind resistance increases with the cube of the rider's speed, so is 8 times greater at 30mph than at 15mph)

https://endless-sphere.com/w/index.php/EBike_Efficiency#Dete...

And that's just for the motor, ignoring losses in the generator.

Electric bikes don't need perfect efficiency, the Specialized Turbo S has a 700W-hour battery and gives 30 - 60 miles of range (2 - 4 hours at 15mph). A human pedaling at 15mph puts out around 100W, so even if the motor is only 50% efficient, the bike can still travel for 50 miles at that rate on one charge.

With a Segway, you stand well over the wheels and can shift your butt (and center of gravity) as far to the rear as possible to make an emergency stop. I don't see how you'd do that with anything resembling a seated bicycle.

The light is even automatic on human-powered bike share bikes. This seems like an obvious oversight or lack of necessary regulation.

At some point, it's a motorcycle. California sets that point at 28mph.[1] There's a continuous range of electric two-wheeled vehicles from 5mph kiddie bike to track-ready electric motorcycle. So there have to be arbitrary cutoffs.

This is a perfectly good lightweight electric motorcycle claiming to be an "e-bike".[2] It doesn't belong on a sidewalk or bike path. That's a motor vehicle.

[1] https://www.electricbike.com/california-ebike-laws/ [2] https://www.youtube.com/watch?v=lsoznIpK05s

Oregon has a nice graphic that shows all of the requirements that are less than a full blown motorcycle.

http://www.odot.state.or.us/forms/dmv/6619.pdf

I agree about the top speed, 25mph on a trail is dangerous for everybody involved.

I want more than 750w of power, not to go faster, but to get up to speed faster after a stop sign/etc. If we could more quickly accelerate up to the limit, we won't be impeding traffic as badly, and it's less of a burden to actually come to a complete stop.

I bike every day, and I generally always make it through the intersection before any of the cars at the light. You've got much more torque on a bike, starting up in a low gear shouldn't be an issue.

That may be but it's also considered poor practice (and poor fuel efficiency) in a car to just step in the gas and peel out from a light.

Yes, I wouldn't mind the police just going ahead and pulling PIT maneuvers on the speeding delivery salmon in NYC... except that would require them to drive their cars on the sidewalk. Joking, mostly: the police have no problem driving their cars on the sidewalk already.

But the real fix for that is bidirectional bike lanes on as many streets as possible, even if they're single-direction for cars.

Paging 2nd Avenue between 30th and 59th. It's an absolute bike deathtrap, so the 1st Avenue protected lane should clearly be bidirectional.

Yeah 40kmh is dangerous in "bike" settings. You'll ride along unprotected people going a lot slower, if not just walking randomly.

I wouldn't use a bike to speed but mostly to even efforts so I don't sweat too much uphill, and can enjoy 25kmh at 80% the usual efforts.

The Specialized models activate the LED headlamp and rear lights when the electronics are engaged, period. There is no separate off switch, day or night.

Not to mention the slight differences between UK law and European law which the UK government has consistently refused to clarify or fix. At least in theory (although not in practice) many e-bikes imported from Europe are illegal in the UK.

Mind sharing more about the bike itself and what parts you used? Thanks.

Its a Felt BMX and the motor is a 20 inch hub kit with 36 volt battery and 18 amp controller that I bought of aliexpress. Let me know if you want to know something more specific.

Any links? I want to build one but dont have $1000+ for a lunar ruckus. Any help is appreciated. My budget would be < $500. I can buy an used bike.

I have no affiliation but I bought the hub, battery and controller from here https://www.aliexpress.com/store/1413140?spm=2114.10010108.0... (it a full kit but I didnt realise it doesn't include a PAS sensor so I have one on order). The bike cost 150 second hand and it fits together easily.

Thanks this is great. :)

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