Conclusive proof gearboxes are awesome.

[motomoto]

Ok, these are the three categories:

1. For most under powered wimpy assed airplane motor powered misappropriated misconceptions,
the lightweight 9-speed might be appropriate for the cause.

2. If the motor has enough power for the situation, but doesn't have the breadth of powerband appropriate, then a 2 speed
perhaps might be deemed appropriate.

3. If the funding warrants designing the power and breadth into a motor that needs no gear changes, that could be considered
the ultimate choice.

P.S. I think both sides are right. It all depends on how much time, thought, resources, deniro, etc. are available to devote to a
project, as to which choice is best.

 

[John in CR]

What I think e motorbikes will dominate on the race track with a single speed for sure
Now at an electric 24 hour le mans with a heavier car a multispeed speed will win
The only way to end the back and forth arguing is on the track

I don't think even on the track you cant stop the arguing. I think this question is to complex to give it a clear respons. In every case it's different. Like you sad in a car on the 24h of Le Mans a multispeed would win and in a race motorbikes direct drive would dominate. I think you can not give it a general decision for every vehicle. It depends on the case it's self. It depends on to many variables.

You guys have gotta stop making things up to support your illusion. In an endurance race like Le Mans the advantages of the single speed would make the case against gearboxes even stronger. A more simple system means less chance of failure. Greater efficiency means less risk of heat failure and fewer battery stops.

Let go of the idea that multiple gears makes the system run at greater efficiency, because even ignoring the transmission losses it isn't true, not compared to a properly sized motor with a single gear ratio. Take Gwhy's CVT as an example. On average he runs the motor closer to peak power throughout the operating range than a single speed would run. That's not a good thing though, because without pretty extreme current limiting, the range around peak power is poor efficiency. The properly sized motor will quickly pass through its peak power point and spend most of the time operating much closer to peak efficiency. The less taxed motor runs at greater efficiency, period. Don't confuse the fact that the variable gearing helps the under powered motor do the job better than it could do without the variable gearing. The comparison is to a properly sized motor for a single speed drive.

Also let go of the idea that extremely heavy motors are needed to run as single speed. The power requirements and max rpm you're willing to accept determine the motor size required. That analysis includes launch torque and max speed required and must consider in your load.

 

[Hillhater]

...compared to a properly sized motor with a single gear ratio.

This phrase and others similar keep getting thrown in the debate.
We need to be clear that these are specific "type" of motor ( AC ?, BLDC ? DC ?, ?? ?)
I believe you should also add "optimized controller" to that also.
..But Then we must ask if these "ideal" components are available or even exist for the various EV's we might consider ?
IE.. Legal ebikes ( low power)
"illegal" Ebikes, ( 1-5 kW ?)
Various sized scooters and small motor bikes,..
Larger "superbike" type rides
Motox / Enduro bikes,..
Cars of various sizes, Trucks, , 4x4's , etc etc

Meanwhile, back in the real world today, we have to utilize what is available, and make the best compromise until the "ideal motor / controller package's to suit each of our individual needs , are developed

 

[Miles]

The less taxed motor runs at greater efficiency, period.

Not necessarily. Motor sizing is to a greater or lesser extent a compromise.

A greater powered motor will have greater parasitic losses (please don't bring up induction motors again). Where the torque requirements are particularly disparate, the lower end of the torque scale could easily become dominated by parasitic losses. In this case, a 2-speed gearbox makes sense.

 

[flathill]

I have no illusions. only the track will end all arguments

obviously with a zero loss transmission with zero shift time
the multispeed Always wins
always

it is how close to the illusion
we distort reality

 

[Miles]

I have no illusions. only the track will end all arguments

Only the track will end all arguments, for the track....

 

[bearing]

I had the hope that this thread would get interesting to read. But it's not. No one is adding new information. Everyone is just pointlessly arguing for their preconceived conceptions. Endless words going around in spheres.

I think it's very simple. Most electric motor systems will have a power/torque curve which looks similar to this:


You then ask two questions:
Is acceleration in constant torque region enough for (every use of) the vehicle?
Is constant power region and max rpm enough to give an adequate top speed?

If answer to both questions are yes, then a 1 gear transmission is enough. Otherwise, the vehicle can benefit from gears. Then you get the choice whether to get a gearbox or to change the electrical system. And if you are going to discuss that choice, then you need to put numbers in the post, otherwise it will just be words adding to the circumnavigation. Everyone who you are writing to understands the basic principles.

 

[drewjet]

Here is some food for thought. The following is hard data from my electrathon. I did 2 different acceleration runs, one using the Etek Direct drive and the other using a Nuvinci.

The controller is a Kelly brushed controller rated for 200 amps, but in reality only hits about 110 from the battery side. Batteries are 2 yellow top Optimas.

Acceleration is about the same, top speed is about the same, however I could easily reprogram the Nuvinci for a much higher top speed, at the sacrifice of higher amp draw. If I had access to a dyno I am sure I could tune the Nuvinci even better. In the end I used direct drive as I am after ultimate efficiency

Draw your own conclusions.

 

[John in CR]

The less taxed motor runs at greater efficiency, period.

Not necessarily. Motor sizing is to a greater or lesser extent a compromise.

A greater powered motor will have greater parasitic losses (please don't bring up induction motors again). Where the torque requirements are particularly disparate, the lower end of the torque scale could easily become dominated by parasitic losses. In this case, a 2-speed gearbox makes sense.

I don't understand what you're getting at. A larger motor can have more copper (lower copper loss) and lower rpm (lower iron loss), or am I missing something? Are you talking about a motor so large that it operates beyond peak efficiency, since the load is too light.

For comparative purposes I see 2 motors of the same quality, ie same efficiency. One isn't big enough for the job, so to achieve the low end torque and top speed required, someone puts a gearbox on it. The other motor is large enough to do the job as a single speed. Even before considering any gearbox losses the smaller motor operates at lower efficiency in high gear, because it's load is greater relative to its size.

 

[besi]

The less taxed motor runs at greater efficiency, period.

Not necessarily. Motor sizing is to a greater or lesser extent a compromise.

A greater powered motor will have greater parasitic losses (please don't bring up induction motors again). Where the torque requirements are particularly disparate, the lower end of the torque scale could easily become dominated by parasitic losses. In this case, a 2-speed gearbox makes sense.

I don't understand what you're getting at. A larger motor can have more copper (lower copper loss) and lower rpm (lower iron loss), or am I missing something? Are you talking about a motor so large that it operates beyond peak efficiency, since the load is too light.

For comparative purposes I see 2 motors of the same quality, ie same efficiency. One isn't big enough for the job, so to achieve the low end torque and top speed required, someone puts a gearbox on it. The other motor is large enough to do the job as a single speed. Even before considering any gearbox losses the smaller motor operates at lower efficiency in high gear, because it's load is greater relative to its size.

This is a possibility to see it but you can see it the other way around too. With the same motor which you are using for the direct drive you could gear it end get even more out of it. And make it always run in it's peak efficiency.

 

[Miles]

I don't understand what you're getting at. A larger motor can have more copper (lower copper loss) and lower rpm (lower iron loss), or am I missing something?

If you have a larger motor just to run it slower, it's no more powerful..........

If it has more copper it has more iron ( assuming equal optimisation). If it has more iron it has greater iron losses....

Are you talking about a motor so large that it operates beyond peak efficiency, since the load is too light.

Yes.

 

[Toorbough ULL-Zeveigh]

(please don't bring up induction motors again).

 

[John in CR]

Here is some food for thought. The following is hard data from my electrathon. I did 2 different acceleration runs, one using the Etek Direct drive and the other using a Nuvinci.

The controller is a Kelly brushed controller rated for 200 amps, but in reality only hits about 110 from the battery side. Batteries are 2 yellow top Optimas.

Acceleration is about the same, top speed is about the same, however I could easily reprogram the Nuvinci for a much higher top speed, at the sacrifice of higher amp draw. If I had access to a dyno I am sure I could tune the Nuvinci even better. In the end I used direct drive as I am after ultimate efficiency

Draw your own conclusions.

View attachment 1

Thanks for sharing that drewjet. It makes perfect sense to me. Once you have enough motor for the job, the gearbox adds nothing. I think what is leading most guys astray is that their only experience is with motors inadequate for the job, in which case a gearbox does help improve performance. They'll be hard pressed to find a realistic application where a larger motor isn't a better answer than a gearbox. That's because it takes less motor than they think to exceed both the torque and speed requirements using a single gear ratio.

 

[bobb]

Mr Motomoto

I think you've won.

FWIW - I started with 9-speed derailleur but the problem I had was keeping chains on the darn thing. I got the Nuvinci for $150 (I'm the cheapskate remember) and thought that would be slick. My farmer engineering mentality convinced me that pushing that thing through upshifts HAD to be an efficiency pig. That is when I started playing with the microcontroller throttle/shifter.

If I ever lunch the Nuvinci I'm going right back to a derailluer. Maybe a 5 or 6 speed. Space the cogs a wee bit further apart and use the heavier chain that they use on the stunt bikes. I would make the derailleur servo actuated. I'm certain I could blip the throttle with the microcontroller just enough to keep the chain on it.

I vote to change the name of this thread to "Conclusive proof that gearboxes are awesome to me"

Had I simply hose-clamped that first mislabeled Currie 1000W (I got for $30 from Allelectronics oh so many years ago) to the swingarm and wrapped a chain around it, I would have given up. Instead I built an 80:1 two stage chainring drive and started my journey. Along the way I have demonstrated to hundreds of people that electric vehicles can be fun, reliable, and cheap. To any e-vehicle commercial interests out there - your welcome.

To anyone viewing this who is new to e-bikes, and now thinks that you need a mega dollar holy roman empire sized motor to build a neat fast ride, PLEASE believe me, you don't. GEAR IT.

I don't participate much in forums. I have a problem. They tend to consume my brain. This one has. The heat's on in the shop and I've GOT to go. Maybe I'll equalize my Headway's. I know - their crap too.

PS - I ride my bike all the time at speeds way beyond what the power I have can actually attain. And I don't even call it an over unity machine. I call it the downhill leg.

 

[zombiess]

I skimmed over this thread, can someone please point me to the conclusive proof?

I can see the advantage of 2, maybe even 3 speed gear box "IF" you have a smallish motor capable of producing an extreme excess of power (maybe something like a colossus? in a Velomobile) but is gear limited on top speed and you are after a higher top speed vs acceleration. Then again, you can always add more volts if you can stay with then RPM operating range of the motors.

I'm SWAG'ing it but from what I've seen others do DD wins the majority of the time.

I have learned one thing from some experimenting and reading, when thinking of electrical drive systems, forget almost everything you think you know about ICE systems.

 

[Arlo1]

(please don't bring up induction motors again)

Why not??? Most of this argument started from the Tesla/Viper drag race the Tesla uses an induction motor. I think it is very wise to consider it as some of us are starting down that road! As well the induction motor has the UBER wide efficiency range that will win the argument against a transmission for most uses!

From this efficiency curve please tell me how you can add efficiency with a transmission or Gear Box??? Anyone???

 

[nicobie]

I have learned one thing from some experimenting and reading, when thinking of electrical drive systems, forget almost everything you think you know about ICE systems.

Good advice. I came from a ICE racing background and it took me awhile to get my head around doing things different.

 

[Miles]

Why not??? Most of this argument started from the Tesla/Viper drag race the Tesla uses an induction motor. I think it is very wise to consider it as some of us are starting down that road! As well the induction motor has the UBER wide efficiency range that will win the argument against a transmission for most uses!

Because they're xxxxxxx useless at the scale I'm interested in. I couldn't care less about dick waving acceleration either.

 

[flathill]

(please don't bring up induction motors again)

Why not??? Most of this argument started from the Tesla/Viper drag race the Tesla uses an induction motor. I think it is very wise to consider it as some of us are starting down that road! As well the induction motor has the UBER wide efficiency range that will win the argument against a transmission for most uses!

From this efficiency curve please tell me how you can add efficiency with a transmission or Gear Box??? Anyone???

Try and change the gear ratio and the dyno curves will change. It is all about load matching.

Remeber the GM EV1 was based off the work of the GE/FORD/DOE collaboration on the ETX

The ETX-1 single speed and later a 2 speed with an induction motor. After extensive testing it was determined a 2-speed would increase the range. Maybe they could have increased the motor size who knows. The ETX-2 got a 2 speed and a bldc. GM obviously didnt think 3-5% more range was worth the complexity/cost. Multispeed Only worth it in a racecar on a big track

GM also owned magnequench who owns neo patents but still didnt think to use them due to cost/complexity/minimal gains.

For a motorbike bldc makes sense. Seen many induction motor ebicycles. Bldc motors have less advantsge as motor size goes up. So for cars induction motors make more sense.

I can make a fairly broad generalization
A bldc motor can more often use a multispeed than a induction motor
This is simply because of the power ratio
Rated speed : maximum speed
Induction maybe 1:5
Bldc maybe 1:2
Roughly

Normal mode, or the constant torque region, the motor exerts constant torque (rated torque) over the entire speed range until the rated speed is reached. Once past the rated speed of the motor, the torque will decrease propor- tionally with speed, resulting in a constant power (rated power) output. The constant power region eventually degrades at high speeds, in which the torque decreases proportionally with the square of the speed.

An induction motor will alway have a much wider ratio unless the bldc has field weakening

 

[John in CR]

If induction motors are better as traction motors, why can't they just be scaled down? Is it the electronics that are the problem, not the motor itself?

 

[Arlo1]

If induction motors are better as traction motors, why can't they just be scaled down? Is it the electronics that are the problem, not the motor itself?

I think its just an availability thing. I don't know why miles worded his message that way but I would love to use a induction motor for a bicycle. They have 0 drag when not in use which is the number one reason I never run dead then peddle home. Controllers are more available for these motors because they have higher inductance.
Bigmoose just sent me a file showing part of how to increase the continuous hp to 10x in an industrial induction motor!

 

[Miles]

If induction motors are better as traction motors, why can't they just be scaled down?

Good question. I think they'd be more expensive, and become even less efficient and heavier than the equivalent PMSM motor as you scale down.

 

[bearing]

I like induction motors too, since they don't use any rear earth elements.

 

[flathill]

If induction motors are better as traction motors, why can't they just be scaled down? Is it the electronics that are the problem, not the motor itself?

A small bicycle induction motor would likely be much less efficent that a similar sized bldc. A large induction motor can approach the efficency of a similar sized bldc.

Here is a good read


http://www.teslamotors.com/blog/induction-versus-dc-brushless-motors

With DC brushless, as machine size grows, the magnetic losses increase proportionately and part load efficiency drops. With induction, as machine size grows, losses do not necessarily grow

 

[Miles]

I think that, on a small scale, increasing the air gap to weaken the field of a PMSM might be a worthwhile technique to develop.... With an axial motor, you could this. It doesn't make so much sense reducing the area, as with the radial motor in that video.