Is this idea legal?

[Jeremy]

Despite the obviously poor direct efficiency of a series hybrid electric bike, I keep being drawn back to the general idea.

I've mentioned this idea before, I think. What I've been thinking of is building a tadpole trike, but without any direct mechanical transmission. This means no gears or chain, just a powerful hub motor in the rear wheel.

The pedals would be connected to a high efficiency generator. This would both partially run the hub motor and charge the battery. Although the losses in such a transmission are much higher than in a chain drive, there are some compensating factors.

We are much better at delivering power at a steady rate than we are at dealing with the peaks and troughs of power needed for going up and down hills. A pedal generator would allow a constant power output to be delivered by the rider, irrespective of the terrain. It would also allow battery charging when stationary.

To comply with what I believe to be the letter of the law, having read the electrically assisted pedal cycle bit several times, I believe that all that I need to do is show that the pedals can propel the bike without the battery being connected (this should be possible, I think), that the average electric assist power (not total power to the wheel) doesn't exceed the legal limit and that the battery assist power ceases above the 15mph cut off speed, leaving just the direct electric transmission.

Has anyone any thoughts on my somewhat liberal interpretation of the law?

I doubt that it would ever be challenged, if I were to build such a thing, but I'm in a position where breaking the law isn't something I can risk, even if it is a minor technicality.

Jeremy

 

[Miles]

I think that should be ok...

Carry on

 

[flecc]

It also seems ok to me Jeremy, if you can show the legal maximum power and speed compliances that you've indicated.

I'd go as far as to say the generator might be irrelevant legally if it's charging the battery from your input, as well as you powering the bike.

My reasoning is that the generator is no different in effect from a regeneration system like the BionX. Your generator is recovering energy from your pedalling directly, the BionX recovering the pedalling energy stored kinetically from previous pedalling used to achieve altitude, in both cases storing to the battery.

In both cases you are using the battery and your own pedal power, just the sequence of use and combinations being different.
.

 

[jha07]

Well, In Canada, BC, having a gas generator is not legal. I came across this awhile ago.
Power assisted bicycle electric bicycle ebike laws in British Columbia Canada
I guess it totally depends on where you live.

 

[flecc]

Yes, our laws are very different jha07, and not so specific as that about so many details. I notice that Canadian law specifies brakes on every wheel, but odd though it seems, ours specifies two brakes on bicycles or tricycles and both brakes can be on one wheel in either case, since the law doesn't say otherwise.

I know you have different laws in different areas, that being BC, and I remember Ottawa legalising e-bikes not long ago. Do the laws vary widely between legislatures, and if so, how does that affect cross border riding?

Apologies for this aside Jeremy.
.

 

[Miles]

It says:

"4 A motor assisted cycle must not be equipped with a generator, alternator or similar device powered by a combustion engine."


So, only IC driven generators are disallowed in Canada.

 

[Ian]

I really see no problem with a human powered generator, it just being an alternative form of transmission. As long as the controller limited the continuos power from the battery to 250W (However you interpret that) and the other pedelec conditions were adhered to I don't see how it could not be legal.

 

[john]

Jeremy,

I think it is an excellent idea and you should go for it!

You should be able to keep the losses quite low, the motor being like a normal ebike (obviously geared would be best for starting etc) and the generator could run at max efficiency. Controllers lose very little as you will know.

As for the legality, I'm not sure it would even be classed as an e-bike (although I've not checked the regs. recently). It could perhaps be argued that it is just a different type of transmission. The battery is only storing your own energy as you might do by adding a flywheel (or even heavier tyres).

The majority of e-bikes don't strictly adhere to the 15 mph limit anyway as far as I can tell.

 

[kraeuterbutter]

no idea about the law...

for the idea: sounds to be a great experiment...
at least: without battery this bike would not be fun to drive in my opinion..

on a normal bike you can get eff. of 95%
when hitting a hill you shift down and still have an efficience in the 95% region

but on your concept:
1.) generatoreff. (90%)
2.) controller eff. (98%)
3.) motoreff. (85% at its best)
--> only 75% efficients at its best..

but when hitting a hill and the hub-motor drops to 35% efficience
only 30% of your energie goes to the wheel wereas 95% on a good normal bike will go to the wheel

that sound not very funny too me: hitting a hill, pedaling with 300Watt, only 100Watt hitting the road and 200watt are lost in heat


so a battery would realy be nesseccary..

for having fun pedaling: i think a flywheel is nesseccary
think about the cheap ergometers without flywheel -> when you stop pedaling it stops and you have a hard time to re-start pedaling
thats very disturbing

 

[wheelz]

Hello, my first post...

A more suitable platform for testing electric transmissions like this
is a boat rather than a bicycle - no hills & weight less of an issue.

Start with a modified rowing machine of the flywheel type as the
biomechanical input with the transmission driving a small propeller.
The flywheel gives you some smoothing and storage in place of a
battery and could be formed from the generator iron.

I have always thought it a major design flaw of rowing boats that
has you facing backwards to the direction of motion - electric
transmission solves this as well as all the inconvenience of oars
(clashing, 'catching crabs' or dropping them in the water).

Hmm, this is no longer an Electric Bicycles thread. Move to technical?

 

[Jeremy]

Thanks for the positive responses, much appreciated.

It would certainly be simpler to fit such a system to a boat, but one of the real advantages of this system is it's ability to deal with large variations in power demand, thanks to the battery. A boat would need a near-constant power, so only the higher transmission losses would be experienced

The core principle is for the rider to pedal at maximum comfortable continuous power all the time. This is more power than is needed when on the flat with a tail wind, or going downhill, but the excess can be stored in the battery for later use. When more power than the rider can comfortably deliver is required, such as when going up hill, or battling a head wind, then the battery adds the additional power needed.

In many ways, the principle is similar to my hybrid car. My car uses battery power at low speeds, or to provide additional torque for acceleration and hill climbing. At cruise speeds on the level, the small petrol engine works at an efficient power level to maintain speed. The primary advantage of a hybrid system is when the power demands fluctuate; at a steady power demand there is no efficiency advantage at all.

Jeremy