Copenhagen Wheel

There ought to be some sort of simple series/parallel motor that is driven in parallel but is switched to series to provide a higher voltage in generator mode, thereby back-charging the battery (i.e., regeneration). Or some other such mechanism. Too bad I'm not all that up on electronics....

The relatively light loads involved means that this should not be terribly expensive.

I would definitely recommend regen for a bicycle. Here we have so many hills, bike riding is very difficult. With regen, you charge all the way down a hill instead of braking, burning up expensive brake parts. Then you get some help on the next hill! It would make bike riding more attractive in a lot of places.

Also, consider a small electric bike for the pre-motorcycle crowd, the BMXers. Kids are a huge market, and have plenty of money and energy for the next new thing.

Good point. I would think that some simple control schemes could work for this, and have great marketability.

Hi ron,

Your link balked here's a working one

http://senseable.mit.edu/copenhagenwheel/urbanData.html

I looked at your blog & agree with your concerns. there is no real meat on the MIT page, just marketing, most on which centered around what a cool app it is for your "I" phone

Here's a discussion about a students working electric bike

http://cr4.globalspec.com/thread/42655#newcomments

Many of the battery issues are discussed in detail...

Unless I'm missing something, the MIT project doesn't have enough battery capacity to be anything more than [ballast]added weight

putting regenerative braking on a bike could make sense, especially due to the small amount of energy return needed to realize improvement.

It does strike me as odd that the unit is in the rear hub. Braking often reduces speed in a much shorter time than similar increases in speed. Bicycles, like motorcycles, when properly operated, utilize the front wheel for much more braking than the rear wheel.

If the regenerative braking system is in the back hub, it is either somewhat dangerous due to long distances for emergency braking, or inefficient due to being assisted by a non-regenerative brake on the front wheel.

I rarely see a tire spinning due to pedalling too forcefully. I have often seen bike rear wheels slip due to excess braking. I would prefer a regen system provide powerful rapid braking with return of that energy over a longer period than slow braking and wheelie stands.

Benbenben

Damn aren't you ever going to register?

Regen isn't going to provide all the braking, still gonna need to have regular brakes. I wonder how the system knows the difference between 'I'm Tired" & "Help, I don't want to die"

That's the catch. The system is smart as long as the user is smart. He changes gears through the Iphone on his handlebar and powers on the motor that way, if I'm looking at this correctly. This is not an automatic "effort sensing" system.

Sometime back, I started thinking really hard about how to make a bicycle smart, you know, make it realize when you're tired and then automatically shift gears through perhaps a CVT system. It was harder than I thought and some reader's comments were interesting. You may find it interesting http://cozybeehive.blogspot.com/2008/06/all-automatic-cvt-based-bicycle.html

Hi Ron,

Welcome to CR4

Good stuff on your blog.

I would encourage you to post some of those questions here[[new threads]

It would seem to be possible to have a few different profiles to simplify the problem.

Even so there are just a ton of variables...

Oh definitely. I love the forum so far. Its simple and lots of insightful discussions going on here. Hope to stay and become a "guru" someday

Actually, I registered a long time ago.

If i am logged on currenly, the system does not allow me to comment. I have received no useful assistance from the powers that be, and no reason for the limits placed on my screenname. I was at one point told not to make a new registration.

That was about a year ago. I continue in limbo, until such a time as I am told of my crime, or my sentence is commutted. I enjoy getting 'ga' reviews, but have no way to track these efficiently. I enjoy the blog more than i need ego support, so i choose to continue posting.

Benbenben (I have considered at one posters suggestion changing my moniker to 'Benbenbanned'

Hi benbenben,

My prototype three-wheeler uses regenerative braking, and in its current incarnation, only the rear wheel is powered. (In a production version, the two front wheels will be independently powered.) Powering only the rear wheel means that the rear wheel must carry a relatively large amount of the total weight for good traction. However, the greater the rear wheel weight, the greater the propensity toward oversteer -- which can be fun, but not particularly safe for a half-asleep commuter.

But for ordinary driving around, the current prototype works fine, and most of my braking is from regen at the rear wheel. After a drive, the friction brakes are usually completely cold. (The prototype has discs at all three wheels but only the fronts are used for stopping at rates greater than regen supports.) The batteries on my vehicle cannot accept a charge quickly enough to allow for panic braking. This would be more so the case with bicycles, so rear wheel regen braking (supplemented with front wheel braking for fast stops) would probably work OK for bicycles (depending upon how much power is supplied by the electric motor, battery pack size, etc)*.

But your point is correct: it would make more sense to brake with the front wheel. On the other hand, front wheel drive motorcycles are a little strange to drive, I've read, particularly when power is applied with the front wheel turned. Electric bicycles are available with front wheel drive, and in that application, the low power probably has a less pronounced effect on handling.

About the best that can be hoped for is a 10% range increase from implementing regenerative braking. There are many home-built electric motorcycles on which regen has been implemented and some of the production electric motor scooters from China also implement regen (in both cases through the rear drive wheel).

*Typically, electric bicycles are very low power as compared to electric motorcycles, and, as a result, accelerate slowly. Typically, deceleration via regen braking is limited to about half of the maximum acceleration rate, because the battery recharge rate is often limited to about half the discharge rate. This means the regen braking in an electric bicycle is very modest.

Blink,

Thank you for the real world insight. In one of my previous occupational incarnations I built custom bike frames, so I have a thorough understanding of real world mechanics of biking. My real world experience with regen-braking however, is limited.

In a regen-braking system designed to assist the cyclist, I would still contend that front wheel placement might offer the most assistance at a given weight or be the lightest for a given level of assistance. I can also see why rear placement makes more sense once the vehicle becomes fully electric, or substantially heavier.

I do know that most vehicles on the road; cars, trucks, motorcycles, and bicycles, typically do most braking with the front brakes. I would assume 70% would be average, but I have no data to back this.

Would it not be possible to store the excess charge (above which can be used to charge the batteries) temporarily in cheap electrolytic capacitors, to be used to charge the batteries at an appropriate rate? This is not my field of expertise, so there may be something am overlooking, but I believe I could put together a circuit that would accomplish this.....

Benbenben

There is something to be said for mounting the drive on the front wheel. Bicycles have a rear weight bias. Of course any unsprung weight is bad...

I would think there could be some other advantages to having the drives on different wheels.

Having 2wd on a mountain bike would be cool...

Having 2wd on a mountain bike would be cool...

Do you remember these? They are still being made.

Yeah, I used to ride with a guy who used his to herd cows

I was looking for the dirtbike 2wd kits & found this

And this

I would assume 70% would be average, but I have no data to back this.

I think you'd be very close. Of course the figure for any given vehicle can vary dramatically depending on circumstance. Racing motorcycles get almost no braking from the rear wheel, and most sport bikes can do "stoppies" in which 100% of the braking is from the front wheel and the rear wheel is off the ground. Heavily laden trucks stopping at normal rates are probably at the other extreme of the range (maybe 40% front 60% rear).

Would it not be possible to store the excess charge (above which can be used to charge the batteries) temporarily in cheap electrolytic capacitors, to be used to charge the batteries at an appropriate rate?

Definitely. That technique is used in some very large hybrid construction equipment, using banks of supercapacitors. It takes a lot of capacitance to yield a meaningful amount of energy storage. In my prototype I considered using super capacitors, but the cost could not be justified, particularly since the need (given that the battery bank is on the large size) is infrequent. However, on a bike with a very small battery, capacitors could prove beneficial, I'd think.

Batteries like these are about 100 Wh per kg, and can discharge continuously at about 500 W per kg, so a 1kg battery (of smaller cells in series for higher voltage) could make a meaningful contribution to getting you up "the big hill" on the way to work, I suppose (provided you used the brakes all the way down the big hill the night before).

In areas where bikes are routinely for commuting, simple transportation, deliveries and by couriers (unlike where I live, where they are used almost entirely for sport and recreation) I suppose such a system could make sense. (Recreationally, I suppose it could be used as an equalizer for married couples in which one rider has to wait at the top of hills for the other.)

Blink,

Thanks again, I enjoy reading your posts (would give a GA...but i'm an outcast and unable...)

The idea of using cheap electrolytic caps not as primary storage (they offer a lot of capacity in a light cheap form, but do leak charge over time) but just as very short period storage and then using that to charge the battery at the rate the battery can handle, might provide a lot of flexibility on the cheap.

I don't think it would be picked up in the sport and recreation area, but it could make a more usable commuter bike that could get riders to work at further distances,faster speeds and without sweating all over your desk when you arrive.... dreaming really. But perhaps it would make commuting newly possible for some...

Benbenben

I had what was in effect a human assist scooter.

A 50cc moped, that had pedals & a lock up for starting.

The timing was fixed so I had advanced it as far as possible for maximum top end, along with "opening up the baffle" on the exhaust. Top speed was just under 40mph.

The timing being advanced, made it positively glacial from a dead stop, So I would pedal real hard when the lights would turn green.

The reason I had it was a glitch in the law allowing me to ride it even though, my license was suspended I did get pulled over a couple of times,since my max speed was supposed to be 25 & it was probably a little loud.

I was living in new orleans & 40 was fast enough to use the major secondary roads, though I was limited to taking the ferry across the mississippi, since the bridges were limited access... I could use a lane fully & not be in fear of my life like I was when using a bicycle on the same streets.

I would think something similar could be worked out as an electric version. The electric version would have decent range, if only used to maintain Rather than gain speed

I don't suppose it was an NSU Quickly? I had one of these, and had fun with it. I remember removing the baffle from the muffler and also removing the muffler entirely, and then recording the sound of it going out our driveway winding up through its two gears (with a portable 1/4 tape machine with 3" reels). It was probably slower without the muffler, but sounded fast.

Slightly later (probably in about 1964) I wanted to buy an NSU Prinz 4 that was sitting in an old broken down garage. I think I thought it could be had for cheap, but I realize now that it was probably only 2 or 3 years old. I suppose I thought that it was so small that it couldn't cost much.

Similar a Puch

only one speed, oil bath centrifical clutch.

it ran better with the baffle having some holes drilled in it.

I mounted a holder for a small plastic bottle that held the amount of 2stroke oil for one tank & always kept a dollar tucked in my wallet

I paid $200 bucks for a used one & put 30'000 miles on it. Even after I got my license back & bought a car, I used it to commute to work. I put a bunch of back tires, a few pistons, some brakeshoes & 3 chains on it

It finally got stolen, the security consisted of a kill switch

I had moved to a new 2nd floor apartment that didn't have a pole to cable it to.

But how good is regen for a lightweight bicycle, when it makes more sense for something more massive like a four wheeler or an F1 car?

Not very.

If I wanted a bike that captured "information about your personal riding habits how much effort you are putting in, calories you are burning etc as well as information about your surroundings, including carbon monoxide, NOx, noise, ambient temperature and relative humidity"... then perhaps I would also want a regen system to add weight to my bike. If I wanted to tweet such info to one of my friends, or if I wanted to have my bike's function controlled by a cell phone... then perhaps I would want the Copenhagen Wheel. But what I want from my bike is light weight and simplicity, rather than gee-gaws and gizmos.

Your comparison to F1 cars is apropos. The F1 system provides 82 hp for 6.6 seconds per lap. That, in comparison to the hundreds of hp used for a minute or two per lap, is a very small amount of energy. If the bicycle system stores significant amounts of energy (enough to help you pedal up a hill) it will also have significant mass. I can't imagine that the unit is much less than 10 lbs, about the difference between a very light sophisticated bike and a cheap, very heavy one. Thus, the Copenhagen wheel effectively converts your $2,000 bike into a $150 bike.

Regen makes sense to extend the range of an electric vehicle (and to reduce wear on brakes) particularly when implementing it is virtually free. But making a bicycle harder to pedal all the time for a limited boost up an occasional hill makes little sense to me: The braking energy recovered is a very small portion of the energy needed to make it easy to pedal up a big hill.

Under certain contrived conditions (such as a bicyclist trying to maintain a constant speed while going both downhill and up, by braking on the downhills) the device could be vaguely useful. However, bicyclists are rarely forced to maintain constant speed. The most efficient way to traverse hills and valleys to to act like a pendulum: the last thing I want at the bottom of hill is low speed going in.

Around town, I mainly coast to a stop, with a little jab at the brakes at the very end. This would give me very little stored energy.

I'd have to see a lot of actual test results to be convinced that a Copenhagen Wheel-equipped bike is anything but less efficient than an ordinary bike.

Energy storage seems the biggest problem here.

Would it be feasible to have a fairly small battery and flywheel energy store?

Under braking, the flywheel would rapidly store considerable energy and on undulating ground generate power to help on the next hill.

It could also recharge the battery which could give some help when the bike has been stationary for long enough to lose most of the flywheel energy (eg in the car park while at work).

Of course the energy stored when the flywheel has slowed would be predominantly lost.

It would also be possible to connect to the mains at night, with a timer, to spin up the flywheel in time for a good start next morning.

Flywheel/generator systems can be made surprising efficient and can provide quite high density short term power storage.

The basic idea may well work with commuter cars also.

Maybe the toy makers are prophetic!

I haven't crunched the numbers on this one so that may well kill the idea.

I haven't crunched the numbers on this one so that may well kill the idea.

It is a perfectly reasonable idea (and has worked in buses and in Formula One), but if you crunched the numbers, particularly the dollar cost numbers, you would find the idea killed. A transmission alone, that can smoothly accelerate a vehicle by using energy from a device that is decelerating is itself not simple to produce in a light design suitable for a bicycle. Electrics (rather than the mechanical CVT used in Formula One) are a possibility, using electronics to change voltages as require. But the cost and complexity remain issues.