``` The Gearing Advantage ```

[safe]

This is all a bit simplistic. Why don't you report back when you've got some real data.

I've got my own bike that has validated everything I've written about so far. My shift points, power behavior have all been very close to the theoretical models. So what I've been presenting is more of the "post data analysis" than anything else. This is the way things work in practice... in the "real world". (or at least as close as a model can be made to mimick the "real world")

I collected the data first... then created (and adjusted) the models second... which is the best way to do it.

But as far as the NuVinci hub I have no data because I don't own one. Given what I see of the calculations I'll save my money becuase a 6% difference isn't worth it. That's where the theoretical models can instruct my future behavior becuase I can see that the advantage is "real" but likely small compared to a regular 8-Speed gear setup.

[Miles]

Do you have any figures for the efficiency of the different gears of the S.A. hub gear?

Do you have any figures for the efficiency of the Nu Vinci across its range?

[safe]

Do you have any figures for the efficiency of the different gears of the S.A. hub gear?

Do you have any figures for the efficiency of the Nu Vinci across its range?

I've included all that into the theoretical models. I'm assuming that the efficiency of the NuVinci is roughly equal to the 8-Speed. Gears introduce about a 5% loss compared to not having them. All models are approximations... they are to give you a basic framework to make decisions. Upon this framework we see that while the move to gears is a big step... a big advantage... the secondary move to a CVT is only a small improvement on top of that. Philosophically I don't see the big advantage to taking that last step.

At some point I see throwing all this into the garbage and starting over with the Tesla style Induction motor. Those motors can achieve 94% efficiency and PREFER to be under load. For "sport" riders load is everything and "steady state" is not very important.

The law in America is 750 Watts, Canada is 500 Watts and Europe is 250 Watts. The best way to utilize those legal limits is with an Induction motor. (if you want "sport" performance)

Full power all the time... now that's the future....

(because the law is very restrictive)

Motorcycles and mopeds are allowed much higher limits, so for them they can avoid a lot of the performance "tweeks" we need to pay attention to in order to retain our bicycle classification.

The easy way is always to produce illegal (over the limit) power...

And looking at the chart again it's obvious that this motor is ILLEGAL as I'm presenting because it's waaaaaay over the power limit. I'd be better off with a 250 watt motor and getting 750 watts out of it. (this chart shows over 1000 watts most of the time, despite the fact that it's a legal 750 watt rated motor)

[Miles]

Do you have any figures for the efficiency of the different gears of the S.A. hub gear?

Do you have any figures for the efficiency of the Nu Vinci across its range?

[color=olive][i][b]I've included all that into the theoretical models. I'm assuming that the efficiency of the NuVinci is roughly equal to the 8-Speed. Gears introduce about a 5% loss compared to not having them. All models are approximations... they are to give you a basic framework to make decisions.

So, rather a lot of guessing. The efficiency of hub gears varies a lot, from gear to gear and the efficiency of the Nu Vinci remains unknown.

[safe]

So, rather a lot of guessing. The efficiency of hub gears varies a lot, from gear to gear and the efficiency of the Nu Vinci remains unknown.

My point is that no matter where you peg the efficiency (from 5% to 10%) the NuVinci is NOT going to be a significant advantage over an 8-Speed geared transmission. That's the point here... there's not enough "room" left in the performance envelope to gain much more.

You can't "magically" get performance out of nowhere. All the gearing really does is correct for the permanent magnets of the DC motor that have the annoying quality that they prefer certain rpms over others. All gears do is correct for the motors inherent deficiencies.

I'll say again...

The REAL solution is the Tesla Induction motor because it loads up really well. The permanent magnet based motors only work at their best in a narrow rpm range and suffer everywhere else both in terms of heat and efficiency. (one in the same thing) The Inductance motor creates it's own magnetism so it's "perfect" all the way through the rpms. The "ultimate" destination is the computer controller SR/VR Switched Reluctance / Variable Reluctance motor that has nothing but a hunk of iron as the rotor... no brushes, no sensors, everything is induced/controlled from the outside.

The NuVinci is a nice hub and if it performs equally or better than an 8-Speed transmission (hub or traditional) then it could show some modest advantages. But I don't see it as part of a cost effectiveness solution... what you gain over the 8-Speed might not be worth the cost.

We can say that no gearing solution will be worse than 10%... that's simply too extreme. The typical clean and well lubricated chain runs at a 98% efficiency... so a loss of only about 2%. If your losses are more then 10% you have a bicycle maintenance problem going on...

[TylerDurden]

Do you want "sport" performance?

or

Do you want "steady state" performance?

A false distinction, these styles are not mutually exclusive to most riders as they are for you. With a high power hubmotor, I get my "sport", and I get my "touring".

Sport Performance = riding till your motor gets too hot.

Steady State Performance = Riding as long as you like.

[safe]

Sport Performance = riding till your motor gets too hot.

Well you're essentially correct.

A dragster needs to be able to finish it's quarter mile and not overheat.

An Indy Car needs to be at full speed in order to get enough air cooling through their radiators or they will overheat. This is why when the Indy Cars run on the road courses they will make modifications to their radiators in order to get better cooling at low speeds.

The electric bike "sport style" (like mine) has a typical range of about 30-45 minutes at full speed. In that time the motor gradually heats up and when I'm done the motor is just getting to it's hottest point. After 2-3 hours of charging the battery is rejuvenated and the motor is cooled and you can go out again and go full speed. It's possible to do this four times in one day.

So "yes" most definitely... the "sport rider" needs to practice "heat management" and know the limits of power, heat and time and not let it get away from you...

MCL should help a lot because it makes it impossible to make a mistake. The BCL suffers from the fact that a poor gearing choice can increase heating. MCL heating is a constant.

That was the lesson of this chart:

[TylerDurden]

So... just how long can a 36V Unite MY1020 run @ 48V, 50A?

[safe]

So... just how long can a 36V Unite MY1020 run @ 48V, 50A?

With forced air cooling and MCL it might run the desired time limit of 30-45 minutes. If not, then I could lower the boost down to 40 amps. I have a feeling (just by looking at the charts) that I might be able to get away with 60 amps if I'm using forced air cooling, MCL, and only run for 30-45 minutes. That sort of thing is determined by the forced air cooling and the sheer mass of the motor... the larger the mass the slower the heat build up. Once the ride is finished you get 2-3 hours of cool down... so it works out fine.

Fechter has claimed to roughly double his heat dissipation rate when he added forced air cooling.

[Miles]

We can say that no gearing solution will be worse than 10%... that's simply too extreme. The typical clean and well lubricated chain runs at a 98% efficiency... so a loss of only about 2%. If your losses are more then 10% you have a bicycle maintenance problem going on...

No, "we" cannot.

Losses on some ratios of hub gears can approach or exceed 10%

The % efficiency will vary with the torque that you are putting through the drive-train, of course. So, for your case, you're probably right.

[xyster]

Sport Performance = riding till your motor gets too hot.

Steady State Performance = Riding as long as you like.

If Safe rode my bike instead of his, he'd enjoy much better performance (except perhaps handling), and the motor would never get hot, and in his state my bicycle would be just as much of a bicycle as his is in the eyes of the law. So how does "sport performance" equate to "riding till your motor gets too hot"?

[safe]

Staying Within The Law

Assume you aren't a home enthusiast with a modified machine that produces horsepower that is better suited for a small motorcycle or moped. Assume you are a manufacturer that needs to pass the basic set of rules that define the American, Canadian or European electric bike. No matter what the limit (750 watt, 500 watt or 250 watt) while you are operating within that limit it says nothing about how wide the powerband might be within the limit. The limits are "peak" limits... it's sometimes expressed in terms of "rated load" for a motor. The "rated load" is really a heat related term because it's the load that the motor could run 24 hours a day and never overheat. This makes things more complicated because you can exceed the "rated load" for short periods and simply take the heat "hit" to your motor. If you allow the motor to cool off afterwards you are okay, but if you keep going hard it will burn up the motor.

One way or another a "true" accepted limit is understood by the law and the manufacturer.

At this point it comes down to how that power is delivered to the road. If you use the classic fixed geared powerband the power at low rpms is not that great compared to a geared solution. Even with the benefit of the "current multiplication" the power of a reduced gear and a high rpm to the rear wheel beats the non-geared machine easily. So the simple answer is to use a standard motor and then just gear it so that the power from 0 mph all the way to top speed is very close to the legal limit. You could use a derailler, a multispeed hub, or a NuVinci hub for gearing to make that happen.

But the "next generation" of motors could use the Tesla style inductance technique and eliminate the need for gears altogether. With peak efficiencies in the 94% range under full load ACROSS ALL RPMS this type of motor is unbeatable. However, at this point in time the control systems are complex enough that the costs are too high.

Having gearing gets you very, very close to the induction motor ideal. The NuVinci approach is virtually equal to the induction motor and the only remaining question is the efficiency comparision of inductance motor verses permanent magnet motor plus NuVinci... I suspect it's only on that last analysis that the NuVinci option has to surrender to it's logical successor.. the inductance motor.

[ott]

34% increase in power. Yeah I'd take it. Also with the Nuvinci you can run a #35, #40, etc. chain. You could put the powerband in the middle and use the higher gears when you are outrunning law enforcement.
Yes the weight...It corresponds to the power capability of the hub- easily handling 5hp+. If you are running a powerful motor 8 pounds ain't that bad is it? (You have to take off .3 pounds of chain and rear derailleur weight ;)

Anyway it seems like a bulletproof quality piece of work that hub. It is at least $500 for a fully built, double sprocket freewheel wheel though. It sure would be fun on a scooter!

[Miles]

Yes the weight...It corresponds to the power capability of the hub- easily handling 5hp+. If you are running a powerful motor 8 pounds ain't that bad is it?

Have you got a reference for that? I seem to remember a limit of something like 150 Nm for the bicycle version....

[Miles]

Maximum torque for the NuVinci is 130 Nm

Ref: http://www.atcnuvinci.com/docs/ATC_Bike_Datasheet.pdf

[safe]

Maximum torque for the NuVinci is 130 Nm

Considering that the maximum hub torque you are likely to encounter is about 65 Nm I don't think you have much to worry about.

Assuming you use a small motor like a 750 watt...

[Miles]

Maximum torque for the NuVinci is 130 Nm

Considering that the maximum hub torque you are likely to encounter is about 65 Nm I don't think you have much to worry about.

This was addressing a claim that the NuVinci could easily handle 5HP+ motors.......

I guess you are assuming no human input, safe

[safe]

...I was addressing a claim that the NuVinci could easily handle 5HP+ motors.......

I guess you are assuming no human input, safe

5 horsepower would be too much.

Why use a NuVinci when you have 5 horsepower?... on a bicycle of all things.
Unless you do as I've done and build a custom frame to handle that kind of speed and power all that horsepower ends up just tempting someone to use it and hurt themselves.

Look at Xyster... he has lot's of power but can't even test the top speed without fear of the bike either breaking to pieces or throwing him to the ground. By the time you get up to 5 horsepower you need to be serious about making sure that the machine can handle it and is safe at high speed. (60 mph) Either that or develop an extremely cautious and timid riding style. (cruising and not sport)

As for human input... yes... that's a real problem. The motor power is a constant and is pretty predictable, but the human power can spike to several times normal when you really accelerate hard. You almost need a pedal motion cutoff switch that cuts the motor power whenever there is a large surge in pedal power.

When I build a pedal powered electric bike I'm going to use a really small motor (like a 250 watt) and then trick it out so that it just barely gets up to 750 watts. That should keep things below the breakage point...

[Lowell]

5 horsepower is half of a good start My bike at 7500W is almost as much fun as bouncing an 07 Gixxer off the rev limiter. Girlfriend was test riding a new bike... only a 600 tho... gutless with barely 100hp on the back wheel.

[xyster]

Look at Xyster... he has lot's of power but can't even test the top speed without fear of the bike either breaking to pieces or throwing him to the ground. By the time you get up to 5 horsepower you need to be serious about making sure that the machine can handle it and is safe at high speed. (60 mph) Either that or develop an extremely cautious and timid riding style. (cruising and not sport)

Hardly. I'm just not a speed freak like you are. And I recognize dangers that can take down a bicycle at high speeds -- like that squirrel I hit a few days ago, and all the motor vehicles, glass bottles, rocks, pine cones, tree branches, dogs, cats, kids, potholes, and grates that regularly materialize just in front of my bike. Unlike you Safe, I don't ride around inside the same, quiet, insular unfinished housing development day after day. I ride around in the real world, and try to explore new areas I've never been before. The bicycle handles great at 30-40mph, and probably much faster -- but it's still a bicycle being ridden through new and often windy, rainy, dangerous areas.

[Miles]

As for human input... yes... that's a real problem. The motor power is a constant and is pretty predictable, but the human power can spike to several times normal when you really accelerate hard. You almost need a pedal motion cutoff switch that cuts the motor power whenever there is a large surge in pedal power.

When I build a pedal powered electric bike I'm going to use a really small motor (like a 250 watt) and then trick it out so that it just barely gets up to 750 watts. That should keep things below the breakage point...

According to Rohloff, an extreme pedal input, might be around 250 Nm at the cranks - say, up to 100 Nm at the rear hub.

[safe]

The bicycle handles great at 30-40mph, and probably much faster.

Well that's a different story than you used to tell. You used to say that you didn't like going faster than 20-25 mph or so and by the time you hit 35-40 mph you had to slow down for fear of things getting unstable. I'm not suggesting that people ride at breakneck speeds all the time, but obviously it's possible to design stability into a motor vehicle and motorcycles are our best examples of how to do it. (they can go 100+ mph and still handle great)

I'm convinced that the number one problem that people face with bicycle geometry is the wheelbase. The average bicycle wheelbase is around 42", but the typical motorcycle is 52" or beyond. (a Harley can be really long, like 60" or more)

My essential point is that in my case my bike is:

1. Underpowered
2. Designed for high speed stability

...but in contrast your bike design has:

1. Excessive power
2. Not stable at higher speeds

So who is really taking the larger risk? I can run full throttle all day long and be lucky to max out at 42 mph on a straightaway (most of the time it's more like 30 mph) and with the bikes long wheelbase the speeds feel very comfortable and I've been in many situations where I had to suddenly react to circumstances and the bike responded very well.

On an overpowered, hub motor rear wheeled, short wheelbase bike (of which there are many examples) you have a large temptation to get yourself into scary situations.

It reminds me of a "Muscle Car" I once owned... I could get up to all kinds of speed, but the moment I had to take a turn or use the brakes it got really, really scary. In contrast I've owned lightweight sports cars like the Honda Civic Si that handled really well and inspired confidence all the time... it actually handled better the faster I went with it.

Handling should come before power... (in my "not so humble" opinion)

[safe]

According to Rohloff, an extreme pedal input, might be around 250 Nm at the cranks - say, up to 100 Nm at the rear hub.

That's why the combined effect of the steady motor torque combined with the oscillating pedal torque can be so scary. Taken in isolation they are okay, but together you need to be careful.

The trick is to not allow the pedal gearing to be too low. Force the pedal gear ratio up really high and that lowers the pedal torque enough to eliminate the problem.

I've got this integrated into one of my spreadsheets and can calculate (and locate) potential "hot spots".

[xyster]

The bicycle handles great at 30-40mph, and probably much faster.

Well that's a different story than you used to tell. You used to say that you didn't like going faster than 20-25 mph or so and by the time you hit 35-40 mph you had to slow down for fear of things getting unstable.

That's because I moved most of the battery weight off the back rack, remember? That single change completely fixed the instability problem.

...but in contrast your bike design has:

1. Excessive power
2. Not stable at higher speeds

So who is really taking the larger risk? I can run full throttle all day long and be lucky to max out at 42 mph on a straightaway (most of the time it's more like 30 mph) and with the bikes long wheelbase the speeds feel very comfortable and I've been in many situations where I had to suddenly react to circumstances and the bike responded very well.

[/quote]

I'm probably taking the bigger risk by far. Not because of any inferior handling characteristics, but because I ride around cars, people, animals, blowing debris, and in rainy, windy, icy stormy weather and in novel areas I haven't been before. Whereas you stick to a known, desolate track, and pack it in each winter. It's these conditions which preclude me from riding as fast as you do. Plus, like I said, I'm not a speed freak. I'm a freedom freak.
My bike doesn't have excessive power. It's underpowered for some of the places and conditions I'd like to take it. And 2800 watts is not nearly enough to buck me off the back if I accidentally tweak the throttle -- that would be excessive power.

[TylerDurden]

I can run full throttle all day long and be lucky to max out at 42 mph on a straightaway ...

You mean you can run full throttle for thirty minutes and then shut down before your motor smokes.