Concepts for eBike Propulsion

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The Six Planet design has twice as many planets as the three planet one.

Having twice the strength means you can miniaturize the scale of this Gear Bearing Reducer so as to minimize weight.

On the input side the external ring could be built into the motors external shell assuming you have an inrunner motor. (inrunner means the iron is on the outside and the magnets spin on the inside)

On the output side the outer ring could directly mate with a sprocket. (just one option)

The motor shaft could actually hold the inner gear teeth and bearing surface so that the motor and reducer are blended together.

...we are talking about pounds and pounds of weight loss.

Keep in mind we are achieving 50-to-1 gear reduction in this small package !!!
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http://www.google.com/patents/US20090097794?cl=en

I don't know the story on this, but it looks like Darrell Grayson Higgins studied the work of John Vranish and did the logical next step which is to taper the edges of the gear bearings.

However it actually happened... we now have the ability to shape gear bearings so that they resist side to side loads.

It all just flows towards a collective design I guess. More options.
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John Vranish generated many patent ideas.

He even patented a type of Sprag Clutch Motor and also a three dimensional Sprag Clutch design.

Magnetostrictive magnetically controlled sprag locking motor:

https://www.google.com/patents/US6410999?dq=ininventor:%22John+M.+Vranish%22&hl=en&sa=X&ei=WYi8U-ziONKRyATXo4DgCw&ved=0CCcQ6AEwAjgU

Magnetostrictive roller drive motor:
https://www.google.com/patents/US5079460?dq=ininventor:%22John+M.+Vranish%22&hl=en&sa=X&ei=fPO_U9_fC4eWyATM2ILgDw&ved=0CD8Q6AEwBQ

Three-dimensional roller locking sprags:

https://www.google.com/patents/WO1996003592A1?cl=en&dq=ininventor:%22John+M.+Vranish%22&hl=en&sa=X&ei=I_S_U4KUKsydyASugYKACA&ved...

...other patents go into capacitors and the use of exotic materials like:

http://etrema-usa.com/products/terfenol/

Overall it's an impressive career. John Vranish seems to have devoted a significant amount of time on the topic of low speed, high torque, propulsion systems for NASA. They seem relevant to ebikes since those are our concerns as well.

Gear Bearing Reducers seem the best idea that can be transferred based on compactness and maximum gear reduction.

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I've found the math associated with the Gear Bearing Reducer.

There is one more relationship which is tooth count of the Sun to the Planet to the Ring. To find that you use:

Ring = 2 * Planet + Sun

Plug some sample data into a spreadsheet and you get:

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...and charting looks like:

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So there are many possible configurations that will give a ratio in the neighborhood of 50:1.

Going above 50:1 is easy too, so the thought of a 100:1 gear reduction should not be considered difficult, in fact, the relationships actually tend to encourage high reduction.

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Some more data.

As the planets are increased in tooth count the overall ratio increases.

An increase in planet tooth count causes an increase in ring tooth count.

There will be some "optimal" configuration where torque is maximized, but I'm not sure what goes into that calculation.
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The mobile generator does away with batteries

https://www.youtube.com/watch?v=KI3ZAFwXSYs&list=UUXRMNuXCCjkeQgmcXvz9j-Q&index=1

Seems cool

I used to get 100 mpg on an MB5 (50cc two stroke motorcycle) back in the 1980's.

This only gets 133 mpg and it's not exactly a fun ride.

It would have to be 250 mpg before I'd consider it "cool".

Plus it's still a stinky machine burning gasoline.

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http://pedelec-elektro-fahrrad.de/news/mit-binova-flow-fahrraeder-45-minuten-zu-e-bikes-umwandeln/

I like this product.

500 watt front mid-drive without gears.

A while back I proposed this idea:

...and even went through some calculations about the efficiency.

They have added considerable weight in order to get the efficiency up to reasonable levels. Other than the added weight (over small motors with big gear reduction) it's a great idea and from a reliability standpoint would never wear out.

Weight 6 kg (13 lbs)

A small motor with a gear bearing would weigh about 5 lbs.

I still believe John Vranish will prove to be the guy with the best solution. (Gear Bearing)

Anyone ready to try it?

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A closeup view of the John Vranish Gear Bearing Drive.

This one integrates an Outrunner motor inside the Gear Bearing Reduction unit. The gear ratio depends on the Primary and Secondary gear tooth counts and 50-to-1 gear reduction is a breeze.

Imagine a motor running at 5000 rpm. It's output becomes 100 rpm.

This is better than harmonic drives because there is no flexing belt and it's better than the elliptical drives because there is no vibration.

Also, I believe this is under a patent that lends itself to use more easily than privately held patents. It was created through NASA and was made as a public patent. They seem to want it to become publically used.

Might have to pay some small royalty to John Vranish.

(Note: I don't know the guy, so I have no idea)

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The theory about how you get massive gear reduction without multiple (inefficient) reduction stages is much the same as harmonic and elliptical drives. With each revolution of the motor the gear sets only advance a single tooth. This happens because the Primary and Secondary gears are just one tooth difference, so a revolution of the motor outputs just the difference in the gears.

I like the fact it's high efficiency and if built correctly very durable.

Check the patent for more detail:

http://www.google.com/patents/US8016893

...it was only patented officially in 2011. (exactly 3 years tomorrow)
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http://ridebionx.com/technology/motor-technology/

Our latest proof of technology is the new BionX D-Series motor.

The new distinctive design has enabled our engineering team to think outside of the box and come up with great technical solutions that further promote the BionX DNA of noise and vibration free motors with generate/regenerative braking mode and our proven strain gauge technology. The D-series motor is extremely sporty, lightweight and powerful – sticking to our principle, where an ebike has to ride and feel like a bicycle.

Nominal power: 200W (AU & UK), 250W (EU), 500W (NA)
Torque: 25/50 Nm (18.4/36.9lb-ft)
Weight: 4.0kg (8.8 lb)
Brushless, gearless
Generate mode for energy recuperation
Integrated torque sensor

Increased Tangential Speed By increasing the diameter of the motor, the magnetic components are placed on a larger circumference thus move at higher tangential speed. ITS is a major contribution to the 250% increase in power output in steady state.

Magnetic Component Reduction By increasing the diameter of our motor we need less electrical force to produce torque. This enables us to build a lighter motor. MCR is a major contribution to the 250% increase in power output in steady state.

Spoke To Center Longer spokes enable the wheel to flex more. This means more comfort, more grip and more traction on the trail.

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This actually makes a lot of sense. By increasing the diameter of the motor you get a leverage advantage. Longer spokes will likely break less often. The cassette hub allows for modern gearsets. And the weight isn't as bad at 8.8 lbs. My guess is that the efficiency is pretty good.

It's still not going to have the potential of a Gear Bearing Reduction Mid Drive (5 lbs), but it's a big improvement on the old hub motor. (20 lbs) Being able to lift your hub motor based ebike like this was impossible in the old days.
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http://endless-sphere.com/forums/viewtopic.php?f=30&t=57371

Over on Endless-Sphere they seem to be working on a similiar project, but they place the disc outside the spokes and take up some precious gearset space from the cassette.

At the beginning of the thread they even publish this picture of the BionX D-Series:
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...seems to me the high efficiency solution was already being done by BionX.

Geez, I'm actually getting ridiculed there... still:

'really lucas, you're lapsing into 'safe-mode' not referencing your sources, taking implied credit by ommision. "lukes idea" which received a HUGE YAWN from the E*S blu-rues when posted here nearly six months ago. how are those royalty checks coming?'

Funny they use me (Safe) as an insult against LiveForPhysics my arch nemesis. ;)

The term "Deathbike" was coined shortly after I wrote a cruel obituary of Lukes death by ebike.

(still might happen, the guy is getting above 120 mph on "Deathbike 7.0"... not safe for kids)

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Placing the disc in the middle seems the better choice. By hey, if they want to compete and do it in a way they think is even better I'm not going to argue. Either way is better than the default hub motor.

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Note: It appears someone made a mistake at the beginning of that thread on Endless-Sphere and assumed the weight was 15-16 lbs. That was probably the old design. The D-Series is 4 kg or 8.8 lbs. They need to reassess things I think because they might be operating under a false information base.
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My guess is that the DIY community (like Endless-Sphere) is getting a little shell shocked. The stuff coming out of Germany and elsewhere is just soooooooo much better than the products a few years ago that people who are into the hobby are searching for what to do next.

Between the rise of the Mid-Drive and the BionX D-Series hub motor the technical level is making the old DIY creations look like a homeless camp. (seriously, they have some guys that should be on the tv show "Hoarders")

I love the new high tech ebike world. :)

As for carrying batteries onto public transit... my understanding is that if an ebike is "legal" it's treated in most cases as an ordinary bicycle. But if there is a nasty lithium fire I'd worry they might be banned.
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Don't forget about the Gear Bearing High Reduction concept. That's the next step in Mid-Drive design because you get a 50-to-1 gear reduction with an efficiency cost equal to a single stage reduction. That's a game changer. At that point a 500 watt Mid-Drive could be brought down under 5 lbs.

The ebike is definitely not dying.
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This is a repost from some time ago:

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Carbon Fiber Switched Reluctance Rim Motor
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This is an idea I've been toying with for about five years but until now there was a technical problem that I couldn't seem to get past.

The idea is to "insert" thin pieces of iron into a carbon fiber rim so that you create alternating regions of either high magnetic potential or low. What had made me "stuck" in the past is that the technical problem of building it was beyond anything I could accomplish.

I had thought of the idea of using some kind of specially woven carbon fiber cloth that alternated with carbon and iron. Seems too tricky.

Another idea was to insert iron plates, but how might you assemble that so that the rim didn't fall apart under stress? Again, too unworkable.

Finally I came up with a new idea...
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When two magnets are placed outside a contained area iron filings will accumulate in the areas of highest magnetic field strength:
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So the idea would be to MIX iron filings into the RESIN as you build up a carbon fiber rim and then before the resin can set up you apply powerful magnets which draw the iron filings into alignment. Once the resin sets these iron filings create alternating regions of high and low magnetic flux potential.

This solves the problem because you can build a solid carbon fiber rim very quickly. This is the sort of technique that could be done in mass production at a low cost. The iron filings can be electrical silicon steel or some of these more high tech materials being used in transformer cores.

One thing to consider is an alternating current in those magnets because that should "shake" the iron filings and improve migration through the cloth. Ideally you want all the iron filings to accumulate in the desired regions.

Finally, you now have the basis for a switched reluctance motor because the rim will have alternating regions of high and low magnetic flux potential.

This will give torque that is roughly three times a disc motor.

Torque = Force * Radius

Reposted: Still a good idea.

Very tricky to do however. (requires a big investment in equipment)

The iron filings should act as structural elements making the rim stronger.
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Power = Torque x Speed

Torque = Radius x Force

Volume (Weight) = π x Radius x Radius x Height

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These are the high level equations that define how one generates power.

If one chooses a smaller Radius and higher Speed (rpm) motor then you develop more Power with less Volume and typically that means less Weight. This solution would call for higher gear reduction. (John Vranish 50-to-1 Gear Bearing Reducer is the ideal)

Alternatively if one chooses a larger Radius you can generate greater Torque and more Power at lower Speed (rpm) but with the negative that you might add a lot of Weight.

These are the two ends of the "solution spectrum".

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Which is better?

Well, you have to ask yourself what it will be used for. If you are seeking to build a "Deathbike" that will produce 10-20 hp you aren't going to be using an ordinary bicycle chain in a mid drive configuration. If that's your ambition then a bigger motor is better along with a heavy direct drive chain.

For the law abiding ordinary citizen who just wants his 200W-750W Power to be delivered at a low Weight, then a mid drive is your best bet right now. The ability to use the multispeed gearing that already exists on the bicycle means that despite some gear reduction losses (5%) the overall performance is good even when you are climbing steep hills. For mountain biking this is perfect. Weight is now down to as low as 5 lbs for a mid drive solution. (amazing)

At some point we might see a carbon fiber switched reluctance wheel get built (a very complex process that will require some development to get right) and we might then see things swing the other way.

The equations simply point out the tradeoffs.
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Using the equations from above:

Power = Torque x Speed

Torque = Radius x Force

Volume (Weight) = π x Radius x Radius x Height

And we combine them together by holding:

Power = 1

Force = 1

Height = 1

Then:

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...notice that if you increase the Radius the Weight goes up faster than the Speed goes down assuming the other factors don't change. (Weight goes up with the square of Radius)

Smaller motors have more problems with cooling, but otherwise the extra Speed just means more Power. In a more in depth discussion you run into hysteresis losses as the Speed gets above a certain point, so there are limits to this idea. A John Vranish 50-to-1 Gear Bearing Reduction Drive allows a very small motor to spin at high speeds with minimal losses:

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A bigger motor needs to slim down significantly if it is going to remain light. The BionX rear hub motor was an example of doing such a thing.
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Not 100% a John Vranish Gear Bearing Reducer (it's using the older technique) but it's pretty close.

At least it gives a feel for what high reduction looks like.

The Yellow shaft spins very fast and the Brown shell spins very slow. (and backwards)
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The Halbach Cylinder uses magnets in a circular pattern to create a single powerful field into the center.
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http://en.m.wikipedia.org/wiki/Halbach_array

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A John Vranish Gear Bearing Reducer uses planetary gears that differ by just one tooth so that there is a fractional difference in output that is a small percentage of input speed. 50-to-1 reduction is easy.

This is also an ironless design, so there is no hysteresis to worry about. This means that the motor frequency can become rather high without losses, so high rpm matches high gear reduction.
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It's a Halbach / Vranish Hybrid design.
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In one incarnation of the Halbach / Vranish Hybrid the magnetic field remains constant while the magnets (gears and bearings too) spin around in circles.

This would be a type of Homopolar Motor if it didn't violate the Faraday Paradox which it might:
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http://en.m.wikipedia.org/wiki/Homopolar_motor

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What is attractive about a Homopolar motor is there is no need for switching of the current or any need for sensors. However, I'm going to guess that the Faraday Paradox somehow makes this not work because it seems "too good to be true".

In FEMM this does generate a torque about the center when a current is applied to copper coils, so at least as far as a superficial analysis it does appear to work.
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The second incarnation of the Halbach / Vranish Hybrid would allow the field to spin 360 degrees about the center. This would allow Three Phase controllers to be used along with sensors.

In order to get whatever field rotation you want you would need to gear the magnet / gear / bearings so that they spun about an inner planetary gear or an outer shell gear.

There are many variations for this.

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A Halbach Array can be rotated so that every other magnet spins in the opposite direction.

This creates a field that alternates from one side to the other.

What is interesting (and not anticipated) is that for 360 degrees of rotation you actually get two separate peaks on each side. These are used in particle physics for guiding beams so the fact you can adjust the strength on just one side makes it useful.

Not sure if this helps build a motor however.

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If we spin all the magnets in the same direction the field stays on just one side all the time.

What is interesting is that for 360 degrees of rotation you get one complete cycle of the magnetic flux switching. You in effect create a magnetic flux wave.

This is useful because it means the relative difference between the rotation of the magnets and the possible mechanical or electromagnetic interaction it has with the rest of the motor is open to manipulation.

A standing wave creates a Homopolar Motor. (assuming that can work)

A moving wave can be controlled with a Three Phase controller.

So for building a motor we want the magnets spinning together.

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The next step is to figure out how the math of a Halbach Array interacts with the math of a John Vranish Gear Bearing Reducer. It's likely that only certain combinations work effectively.

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http://www.google.com/patents/US6376959

It's always nice to find an existing (but expired) patent on the general idea.

In this example I'm using:

Ground Planet : 10
Output Planet : 9
Ground : 40
Output : 38
Ratio : 57-to-1

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Getting back to a front chainring design we adapt the Halbach Cylinder and the John Vranish Gear Bearing Reducer and we get:
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What is interesting is that the high reduction (50-to-1) can mean that the magnetic field is rotating very rapidly around the spindle. If the spindle is given the correct material properties it will behave like an Induction Motor with "slip". In this way you "recycle" the energy that would be lost as hysteresis and use it to create forward motion with the cranks. This will likely only be 10-20 watts of energy, so the pedals will seem like they want to spin when the motor runs, but not be enough to make the rider nervous. (so we hope) But if you do pedal those 10-20 watts of hysteresis induced "slip" will add to your pedal assistance.

Since the magnets spin very rapidly compared to the crank and chainring it's possible to make this very narrow and lightweight. Remember that:

Power = Torque * Speed

...so the faster the magnets spin the more power you get out of them per unit weight. Ideally this should fit neatly as a replacement for the standard chainring / spindle combination and as most new mid-drives be a simple install.

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http://eazy-ride.com/eazy-ride-kits/flowride/

3200 watts maximum power

Inrunner maintenance-free electric motor (brushless)

Planetary gear high torque at gradients (reduction of engine speed)

Motor weight: 2.5 kg (5.5 lbs)

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My guess is that they are using high gear reduction equal to the John Vranish Gear Bearing Reducer (50-to-1) and a high rpm Inrunner motor to achieve the 3200 watts at only 5.5 lbs.

This seems to be close to the ideal I have been looking into. (not 100% sure)

Also, they introduce the idea of quick release technology, so you can simply remove the motor and battery and then ride the bike without it. This is the first I've seen to do this. The quick release might add weight compared to a fixed mounting however. (one pound extra?)

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This is a great idea.

Place a very long motor inside a shaft drive system. Completely eliminate the chain.

Efficiency is 92% which is very good.

You can't get more practical than this because the motor, controller and shaft are all bundled tightly into a space normally used as a chainstay in the frame. For the person seeking a commuter ebike this sort of simplification is what is desired.

I was actually thinking about the downtube or frametube installed motors recently but this eliminates the friction associated with the bottom bracket.

The motor runs at 3000 rpm and the whole thing weighs about 10 lbs.

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This is a very incremental upgrade from existing products.

The best location for the motor and battery is in the main tube connecting the headset and the bottom bracket. This is because a bicycle wants to pivot based on an axis that roughly passes through the same area. By locating the added weight there it minimizes the rider noticing it.

Other products have tried using the seat post or have loaded the main tube from the bottom, but a "Front Loading" mid-drive would be a good idea. In order to service the battery and motor you would need to remove the forks. It must be assumed that reliability is high enough that removal is a rare event. You would include the controller in this area too.

A small plastic cap would cover the opening on the head tube. This cap might hold the recharging plug or it might be hidden to maximize stealth. If the system is a pedelec then you have no throttle at all and no external wires. A Bluetooth connection could give information as well as turn it on and off. (Smart Phones make good devices for this)

One can still use a John Vranish Gear Bearing Reducer (50-to-1) with the motor which reduces friction compared to multi-stage geardowns and saves space too.
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There are over 300 posts on this thread.

If you go back through the thread you will see most every idea that has ever been imagined as it relates to ebike propulsion.

Actually the idea about pedal / generator / motor is very old... and yes, the problem is that you are just increasing your copper losses (where most losses come from) by doubling them.

The mid-drive satisfies the combining of pedal power with motor power in a very elegant way and with the advantage of multispeed gearing through the derailler it's hard to beat.

A patent from 1898:
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My advice would be to create an image with some paint program that describes your idea in general ways and upload it here. You can then link your image to a post and describe it.

As the saying goes:

"A Picture is Worth a Thousand Words."

...let's see what you have.

There's a 99% probability it's an old idea that has a dozen patents already. (so don't worry)
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