I am not a fan of small 2 cycle engines. They make noise and pollution, the power output is almost an afterthought. The EPA standards are not very strict and the amount of pollution put out by a one HP engine may exceed a full size 100 plus Hp Prius.
Bikes this size are best served by an electric motor in terms of noise and pollution.
Perhaps someone could post the g/HP or g/mile emissions on these small engines.

Actually, bikes of this size are best served by the use of two human legs. If you're gonna use some sort of external power, agree, however, that electric would be better.

http://www.bajajusa.com/emissions.htm

is one source of emissions analysis. two-stroke engines persist because they are a huge win for small motor applications. for the same mass, you get twice the horsepower. and yes, because two strokes are terribly dirty, we are going to have to suck it up and convert to weaker motors made even weaker by low-energy density fuels like ethanol

http://brucelin.ca/scooters/ is an article on fuel cells and scooters.

As for electric bikes, they are toys. They can't carry any sizable amount of load. If you travel any distance i.e. 20 miles or so, it's effectively a one-way trip unless you have four to six hours to spend in between arrival and departure. for small vehicles like scooters and motorcycles, liquid fueled engines will be a win for the for the foreseeable future.

FWIW, when thinking about scooters, don't think about the 49 CC systems. Think about 150 to 500 CC. I'm buying a 250 CC (four stroke, liquid cooled) because it lets me get up to highway speeds without it overpowering my skill level.

This is a great design idea. The packing of it is very well thought out. And until 2 stroke, weed eater type, engines are totally outlawed, which they arent at the moment, I dont see a big problem here. Of course if everyone, and thats everyone, turned in their 6 mpg excursions and suburbans for 6 of these gas powered bikes, then the resulting pollution problems would need to be taken care of. Of course we would save alot of fuel in doing so.

For now, a nice toy to market, but will not make much of an impact. Who would pay an extra $400 on top of the price of the bike, for this system? Only ones who regularly now use a bicycle. This will not get us out of our 4 wheel vehicles.

Eric -

two-strokes do not get twice the power out of the same displacement, for several reasons:
- displacement is bore * stroke of the piston
- the bottom quarter of each stroke is reserved for gas exchange
- combustion products are retained in the chamber (10-30% EGR depending on scavenging method)
- fresh charge must be compressed to effect scavenging, in small engine typically in crankcase

Bottom line: typical power gain relative to four-stroke is more like 50%. The price is HC emissions as high as 30x those of a four-stroke engine of similar power. Note that it is possible to build four-strokes small and powerful enough for chainsaws, with substantially reduced HC emissions.

http://www.all4engineers.com/index.php;site=a4e/lng=en/do=show/alloc=3/id=2712

As for recharge times, with modern batteries it should be possible to bring those down to 15 min off a regular 110V 15A household circuit. Assuming a 50% efficient charger and 14V battery voltage, you'd need a 14.5Ah battery. Btw, some of the fancier electric bikes are rather expensive toys:

min.http://www.zapworld.com/cars/epod.asp

Rafael Seidl: thanks for the correction on power output. I'm looking forward to a pollution tax + buyback program on engines to drive 2strokes out of general use.

And yes, e-scooters are expensive toys. when they can match the range and speed of a 250-300 cc scooter, I'll think about them. ;-)

thanks again for the correction.

Nick F thanks for the links! They are helpful.

Two-strokes, historically anyways, have indeed produced roughly twice the ponies of equal sized four-strokes, because of double the powerstrokes, and simpler engine design with less power-sucking mechanisms like cams, rocker arms, related bearings and chains, etc, etc. Anyone who grew up with dirtbikes knew the two-strokes in their powerband were scary fast: a typical 250cc two-stroke would put out around 50-55 horse compared to roughly half that for a 250cc four-stroke equivalent, at least a decade or more ago. I'm not in the scene anymore so I'm not up on the current generations. Mind you, four-stroke dirtbikes have had a major renaissance lately, and have come a long way, so I can believe two-stokes are not as advantageous anymore, power-wise. However, I do doubt very much the power advantage has been cut in half.

That said, I'm not promoting two-strokes, because they do polute much more, though they have been cleaned up substantially in the last several years. Golden Eagle Bicle engines has a very good engine-assist set-up too: http://www.bikeengines.com/index.htm and though they don't have the slick in-wheel packaging of this setup here (it sits outside of the rear wheel usually), it does have this advantage: you can use any engine you desire, including clean four-strokes.

It would be interesting if something like this could be fueled by an ethanol/svo blend or some other biofuel/blend that works well in a 2 stroke. That way they could market a 'green' fuel for their otherwise dirty motor for those a bit more concerned about emissions and get more free press.

This would make an interesting addition to an electric bike, giving it a third source of power. Hills around here mean lots of opportunity to recover energy, so gas alone doesn't make enough sense.

I'm a bit of a redneck so bear with me. I have a hard time seeing how a bike would handle with front wheel drive. There has to be a nearly vertical learning curve on figuring how to not fall off this thing and burn your face on the engine.

Rafael:

Correction, the bore is about one meter, not two. Until recently, the largest MAN engine employed 98 cm bore. I believe the largest is now 108 cm.

The stroke, however, is more than two meters.

The strongest engines are mostly made for container ships that travel faster than oil tankers. For that reason, and physical limitations of propeller size in harbours, these engines run faster; around 100 rpm.

A note one CARB/EPA regs for small off-road engines: Read, lawn mowers, i.e. very lax regulation! I distinctly remember a study 10-15 years ago comparing emissions from a lawn mower with a SAAB 2.3 litre engine (particularly clean). Mowing an average sized lawn caused as much emission (mostly unburnt HC) as a 4500 km trip with the SAAB engine. That corresponds quite well with my subjective feeling (headache) after using a lawn mower.

sebastian wrote:
"actually the idea is pretty old,
http://www.sachs-bikes.de/de/datenundpreise.php?bike_id=17

already in 1987 they started to produce these bikes, i own one just for fun of 1988"

Actually, the Honda's first product was the same concept in 1947.
http://world.honda.com/history/limitlessdreams/atype/index.html

According to IMO Annex VI, of MARPOL 73/78, regulation 13, a two stroke heavy fuel slow speed diesel with the one meter bore and over two meter stroke can put out 17g NOx/kW-h.
Perhaps sopmeone could put that in context with a normal truck engine, but they are rated g/mile.

They burn fuel from .5 to 4.5 % sulfur with 2.5% being the average, so the SOx is very high.
They have no PM rules other than smoking in port limits.

They put out more pollution than any other engine type except off road two strokes and they at least do not have much SOx.
By changing the fuel to normal diesel low sulfur (500 PPM) like in a truck, and SCR with urea, the pollution goes down about 90%.
The fuel eff. goes down only slightly.

Other than

Say, isnt that engine going around with the wheel? Doesnt that cause fluid buildup in the head? If it is a typical piston port 2stroke, there's no way out for oil buildup, that cant be good.

Here on the left coast, we've seen tons of little 50cc 'gopeds' causing traffic hazards and noise pollution. This is not an elegant solution, but a marketing niche. Lazy americans who dont want to peddle. Where are the micro-hybrid moped/scooters? Is direct injection diesel the only future for motorcycles?

Innovation is what we need, not resurected design.