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.

A real misfit where clean electric non-polluting bikes are availble.

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.

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

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.

Future scooter owner here.

I've looked at the possibility of an electric bike, and the price/performance ratio wasn't good enough for me.

At least someone is looking into the biggest single complaint about bicycling: The sweat. Now if they could work on the funny pants part, we'd be set.

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.

Hmmnnn - navigating dense city traffic with 15 lbs extra weight in the front wheel..? No thanks!

It sounds to me like a dirty, loud lawn mower engine... 65 dB from 7.5 m is quite a lot. Standard cars sound off less than that from 1 m.

Too bad they wasted $1M on that project... :-(

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

I'm also concerned about the noise, like others have mentioned in the standard scientific method is to measure sound levels at 1 meter. In fact, the rider's head is probably not much more than 1 meter from the wheels anyway.

Noise levels generally drop in half for every doubling of distance, although this is where it gets confusing since the real sound level drops in half ever 3 db, even though human perceived levels are every 10db or so. Even if we take the more conservative 3db, 65db at 7.5 meters would be 74 db at 0.93 meters, which is very loud. At 10db doubling, it would be over 90db at 1 meter.

Agreed that a human/electric hybrid bicycle makes more sense both from noise and clean energy perspective.

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.

"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."

Most electric bikes out there fall into the category you describe. However over the last couple of years there's been some huge improvements in wieght loss speed and range. I've personally built lightweight bikes that go 30 miles at 20mph no pedalling.
There are lots of excellent kits out there for cargo see

http://cleverchimp.com/products/stokemonkey/

There's a little less available in the way of complete bikes but there are some great models out there.
Have a look at the ezee torque

http://store.nycewheels.com/ezee-torq-electric-bike.html

One of the great things about electric bikes is that you can expirement with some fantastic battery tech that will takes years to be adopted in cars. Some people are even starting to use a123 systems cells

Anyone looking for info on electric bikes should take a look at www.visforvoltage.com or the yahoo group power-assist Newbies are very much welcome!

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.

NickF: I'd like to see stokemonkey work with: http://www.linearrecumbent.com/ ( I have a folding model) :-)

fuel cell scooters
http://groups.yahoo.com/group/fcscooters/

electric scooters
http://groups.yahoo.com/group/escooters/

dirty search for electric scooters
http://groups.yahoo.com/search?query=electric+scooter&submit=Search

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.

Eric -

you're welcome. A recent long-term study conducted by the Austrian automobile club OeAMTC in collaboration with the Univ. Techn. Vienna shows that total HC emissions in 2005 (total 175,100 metric tons) were split as follows:

solvents - 44%
home furnaces, gas stoves etc. - 23.6%
industry* - 14.7%
agriculture - 4.1%
cars - 4.1%
two-wheelers - 3.7% <--- NOTE
off-road machinery - 2.7%
commercial vehicles & buses - 2.0%
power plants** - 0.6%
aircraft - 0.5%

* includes evaporation at during vehicle fill-ups

* Austria has extensive hydroelectric dams and just one coal-fired power station.

The important thing to note is that on-road two-wheelers produce almost as much HC as all of the cars. This is because of those small engines running on two-stroke gasoline (premixed with lubricant) that do not have three-way catalysts (too much back pressure).

John W -

I meant bmep rathen than nominal power. Due to the simple construction without valves, it is possible to rev a two-stroke higher to achieve the 2x nominal power you indicate. Doing that sharply reduces your engine' life expetancy, though, unless its one of these

http://www.pivotalengine.com

Final point: the biggest reciprocating engines in the world are two-stroke turbodiesels with crossheads and exhaust valves in the calinder head for straight scavenging. These 60,000-100,000 hp monsters are 15m tall and built by Hyundai under license from MAN. Cylinder bore is about 2m. Running at just 60 RPM, they allow the huge propellor of a contain ship to be fitted directly to the crankshaft.

Ergo: not all two-stroke designs are evil, just the ones that blow lots of unburnt HC out the exhaust.

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.

Erick, the Wheel can operate on E85, and on biodiesel (with appropriate changes to 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.

Bike like this should go for 500mpg, 200mpg is not enough.

Why go thru the trouble mounting a 2 stroke on a bicycle? Might as well get a motocycle! Which confirm have more then double the payload of a bike, high MPG, and more power.

Electrical bike, quiet, charge at home, clean, zero emmission and whats bother you so much just to excercise your legs a little?

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

Eric S. Johansson:

.
Wow thats a nice bike (I'm very jealous ! ) ). I'm not sure whether the stoke monkey would fit
Recumbents generally make an excellent platform for electric assist as they are already very efficient. You might want to look at the expensive but good quality mid drive kit
http://ecospeed.net/products.html

there is also the cyclone kit

http://www.cyclone-usa.com/

and a range of diy options some using similar silent induction motors like on the stokemonkey. If you look at the photo section on the power-assist i think there is somebody who's done a conversion on the same bike

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

People, Sorry but you are so far off on modern two stroke engines.

First of all the 50cc two strokes are euro 3 capable (not official yet because they have not finalised the intro date) and have catalytic converters. They make more power that the older not cat versions.

Ironicaly the 4 strokes have great dificulty in meeting legislated CO levels - go figure.

Then of course there are the direct injection technologies that provide very competitive engine out emissions.

Also 200mpg is pretty good for a small engine runing at that speed. The stratified charge engine should drop HC's by about 70%, CO by about 80% and reduce fuel consuption by about 25%.

As for noise. The europen limits for MOPEDs is 72dBA at, surprise surprise, 7.5 meters so 65 dBA is going to be real quiet. Sitting on top of a moped that gets the 72 dBA number whilst riding around on a normal day, you are are aware of the engine but it is subjectively lower that the tire noise of a passing SUV. I would say that at 20mph on this little guy you are not even going to hear the enginge above the general taffic noise.

Mike

PS. how do I know this you ask. This is my job!

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.

The concept is very much older than the 1987 mentioned above. In the 1950s we were selling and servicing the Dutch made Cyclemaster wheels. The first model was 25 cc two stroke within a rear wheel with a pressed steel hub drum painted black, but it was very underpowered. This was quickly replaced with a 32 cc version in grey paint to distinguish it. The petroil tanks were also within the wheel. Slightly later but still in the '50s, BSA took up the idea and produced their own version which they called the Winged Wheel. This was 50 cc and the cylinder and crankcase lay horizontally alongside the hub drum just below the bicycle left frame lower tube, all other parts and fuel tank inside the wheel. All the models netioned transmitted the drive to the hub by a chain. None of these were very long lived and by the early '60s had disappeared.

Unfortunately, it appears this thing will never be sold. It was supposed to be ready for sale in 2007 and it's now 2008 and no news. The site's main page says "join our email list for updates" but there is no link to do so. I envision the company will go belly up and the product will never make it to the street. Too bad they decided to get a nationwide dealer network set up instead of selling it directly themselves. That just complicated matters too much.

A statement was made that 2 stroke engines were dirty engine's and created high emission's, well some of them do have high emission's and then there are some that create
less emission's then a modern four(4) stroke automotive engine. ie: Mercury Marine's Opti-Max 2 stroke engine is legal on any body of water that allow's 4- stroke equipped watercraft and this include's the state of California whom is real tough on emission's. You need a better argument especially when gasoline will hit $4.50+ a gallon this summer.

Four strokes also use oil in the crankcase and yes all
motors burn oil!! The only reason a four stroke seems
to not burn oil is that it is replaced by condensation
and unburnt fuel leaking down and replaces the volumes
that get past the oil rings and past the valve guides.
If some oil didn't get into those areas it would wear
out way too fast. Also a 4 stroke that is tuned to be
a high output motor is working close to the design limit
and a look at MX bikes will show they need to be rebuilt
alot sooner then a 2 stroke and of course more parts to
be replaced which takes more resources(metal) fuel to
get the extra parts to distributors etc. more manufacturers to make the individual parts. more packaging etc etc etc. So what is the total footprint
of each type of motor when you figure in the total cost
of maintaining them, making and using?
There have been many improvements in 2 stroke design
and the high pressure fuel injection that marine engines
ar using is one of the most promising. A supercharger
and turbo to force air into the motor can do away with
the crankcase induction and allow it to use a sump oil
system like a 4 stroke and not have to burn and waste
the oil.

Such items are both wonderful and innovative. As far as the pollution issues are concerned the 2 strokes could be converted to use natural gas or propane. Such a device could even use the proper mix of alcohol and castor oil like small/model airplane engines/radial engines of WWI. But until lead acid battery technology improves (build them to last not for profit by incorporating desulfating tech) I wouldn't rule any of these out. Even the manufactures of 2 stroke oil could use alcohol to make their blends less harsh. Great article and comments.

re: revopower wheel - any comments on how the engine exhausts? As it spins around the front axel, the exhaust pipe also must move. Does it spray out backwards in the slipstream all over your pant legs?

If so, too bad it isn't made for the rear wheel: many successful "powered wheels" were made in the 1950s, but were heavy. Revopower does have the advantage of light weight. Is it for sale yet? They seem reluctant to return correspondence - I've sent a few with no response.

Two-strokes can be fairly "clean" if fitted with disc or reed valves, and if the engine is engineered well it can also use a higher fuel/oil ratio (some run on 50:1), thereby cleaning up the emissions. Some cheap Asian four stroke scooters on the market run like a bloody diesel despite claims of clean emissions and great fuel economy. With only 30+cc to play with, I don't think the RevoPower would be all that much of a threat.