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[NoiseBoy]

Motor torque is a meaningless metric without RPM.

How do you figure that when a motor makes peak torque at 0rpm?

Torque without movement is not producing any power. So you can have all the torque in the world, but if it is not moving something it is not doing any work and therefore is not producing any power. That is why you need rpm to go with your torque to generate power.

However, having a lot of torque throughout the motor's rpm range is a good thing, especially for street riding.  It means that you will have a broad spread of power throughout the rpm range of your motor and will not have to wait for the motor to rev up before being able to use that power to move something (like you) quickly.   

That still doesn't explain how Torque is a meaningless metric.  If i am building a new wardrobe and im tightening a screw, when it goes tight im still applying torque to the screwdriver even though it isn't moving. i.e. 0rpm.  So if you are half way up a steep slope and you come to a stop, power is irrelevant when you want to start moving again?

A friends 600 screamer makes twice as much power as my KTM but my KTM makes much more torque.   In a race from 20 to 60mph my KTM is significantly faster despite the 600 being high in the rev range and a gear lower.   Surely the same concept must apply to electric motors.

[Richard230]

I think that once you, or your wheel, starts to move then you have power.  So the power would be calculated by multiplying the torque by the rpm, even if it is only one revolution per minute.  The torque gets things moving, but power doesn't happen until you do.  At least that is the way I understand things. My last physics course was almost 50 years ago.   

[Biff]

When looking at a PM brushless electric drivetrain you want to know torque, peak torque maximum RPM, and Maximum RPM  I have attached a torque vs speed curve from a Remy motor.  as you can see, depending on your system voltage you get the same maximum torque, but up to a higher RPM , but at some point that torque starts to drop off (peak torque maximum rpm).  That point is where the BEMF of the motor reaches the System voltage (there is also inductance and resistance factored in there as well, but those are just details).

Once you have those numbers you can work out quite a bit.  Typically for a direct drive electric motorcycle you want to have your peak torque available up to your regular cruising speed, then go into the reduced torque (which is actually constant power) above that.  With a brushless PM controller you can typically get 30% more speed, past your peak torque maximum rpm. so if your torque starts dropping at around 65, you would have a top speed of something like 90 in that gear.

Since the peak torque on an electric drivetrain is available over a wide range of speed starting from 0, people always assume it is available for the entire RPM range, which is not always the case.

There will always be the debate as to what is important, torque or power, but typically what is more important is not peak torque or peak power, but the associated torque/ power vs RPM curves.   For a gas engine, a peak torque and power really is useless unless it is accompanied with a power / torque vs RPM graph.  An engine with a very peaky torque curve (only produces useful torque for a very small range of RPM) is pretty much useless, unless you have an application where the RPM doesn't change very much, otherwise you will be shifting gears all the time.  With today's gas Motorcycle and Car engines, the torque curves are pretty flat, so it is assumed that if you have a peak torque value, that there is a useful range where something near that torque will be available. 

I guess my point of view is that Torque and Power are both useless metrics, there is no answer to "what is better torque or power?" because the question doesn't make sense.  To actually be useful you need a graph of either Power or Torque vs speed (and it doesn't matter which one you get, because either one contains the same information).

-ryan

[protomech]

Torque and RPM alone are both insufficient to tell you how "fast" the motor is.

If for example the 600cc motor produces half the torque at the motor output shaft but is spinning twice as fast, then your two bikes should have identical wheel torque. If the bikes weigh the same, then the two of you should accelerate at identical rates.

If your bike is faster at low speeds - and I don't doubt that it is - then a few things could explain it:
* despite being a gear lower and higher in revs, he may still not have as much mechanical advantage as you do. Sportbikes are geared to ride very fast. And even "higher" in revs means he may still be stuck in a rev range where the sportbike engine produces very poor torque.
* 600cc sportbike may be heavier than your KTM
* he may have to shift an extra time

A windmill produces many hundreds or thousands lb-ft torque. Much better as a motor than say a wimpy electric motor that only produces 70 lb-ft no? It would be a very poor vehicle engine because it does so only at a few RPM; the maximum power output is very low.

As Biff says, ideally you want a graph showing the power curve or the torque curve with RPM markings. But if you have only one number to work with, peak power is more useful than peak torque.

[NoiseBoy]

Very interesting.  Now i just have to work out how to up the voltage on my 2012S!

[trikester]

Wow! This thread sure got a long way off from my original posting - the desirability of having all of the FX goodies on a lower suspension for us older dirt "cruisers". In other words, an FXU bike. The low power / torque and small wheel size of the XU doesn't cut it for me and the height of the FX suspension is unnecessary for me. I think there are other dirt riders who would like this combination also.

After I get my custom 2013 FXU from Harlan, I'll let you all know how it works out. Unless of course if I twist the throttle too fast and kill myself. Whee!

Trikester

[Tudor]

Have you decided to go for the FXU, or did you change your mind?

[trikester]

Have you decided to go for the FXU, or did you change your mind?

Glad you asked! After sitting on the stock FX at the Long Beach show I've decided to stay with the stock setup and see how that works for me. What I didn't realize, until then, was what a difference the narrower width of the FX would make in the distance for my feet to the ground. I may change my mind after riding but right now it seems like I could reach the ground easier than on my 2012 DS that I'm riding now.

Also Zero has told me that I will be able to move my low profile Corbin seat to the FX which will lower my seat height some more.

So now the changes that I know I will make as soon as I get the FX are:

Convert to chain drive (to be done by Harlan).

Rear rim to a 2.5" width and tire to K270 5.1 x 18 (to be done by me)

Front tire to K270 3.25 x 21 (by me).

Handlebar switch for Sport / Eco / brake light = momentary selection as I have done on my DS now.

Figure out where to mount a tool box (this has been different between my 2010 and 2012). This is something Zero should have addressed years ago.

That's all I can think of now. I will re-post to this thread if I make any more changes or decide not to do any of these I've listed.

Trikester

[Lipo423]

I have been reading mostly of the thread with a lot of interest...

Have any of you ridden the 2013 FX new model?

I did, and I can guarantee you (without getting into technical discussions)that this thing flies. You actually have to be careful with the throttle if you do not want to end up hitting the ground with your back!!! It accelerates like a rocket and reaches top speed very quickly.
In a way, it reminds me the Tesla Roadster, but with two wheels...

I did raise some questions about the 420A controller limitation also, but after riding it, quite frankly, I do not care  

Battery packs main features. FX model

- 102V
- LiPo Battery (Especific chemistry do not disclosed)
- High Quality cells (manufacturer name not disclosed)
- Higher energy density (this obviously goes along with the chosen chemistry) per Kg
- More expensive packs, but lighter ones
- Modular charging/de-charging
- Each pack is easily removable

[protomech]

Cycle News revealed the battery manufacturer as Farasis here.

Farasis claims their MnR (Manganese Rich) chemistry provides almost 40% higher energy density than "comparable LiFePO4". A123's pouch cells AMP20 are 130 Wh/kg, so Farasis is around 180 Wh/kg (EIG C020 is 175 Wh/kg). Farasis says they are working on a Gen 2 MnR chemistry which would double (presumably LiFePO4) energy density, or 260 Wh/kg.

I believe each ZF2.8 module in the 2013 bikes is 2.55 kWh nominal. The weight difference between the 2013 fixed-module S bikes is 32 pounds (3 module ZF8.5 350 pounds, 4 module ZF11.4 382 pounds) .. so ~177 Wh/kg at the module level, including per-battery instrumentation and control electronics, module packaging etc.

The ZF3 modules in 2012 are 2.63 kWh nominal. The weight difference between the fixed-module 2012 S bikes is 44 pounds (2 module ZF6 297 pounds, 3 module ZF9 341 pounds) .. so ~133 Wh/kg at the module level.

The 2013 modules appear to be 33% denser than the 2012 modules. Assuming this carries over to the cell level, this would mean 175 Wh/kg (EIG) * 1.33 = 232 Wh/kg. So maybe Zero is using the Farasis Gen II chemistry..

Farasis says their chemistry is "manganese rich". I don't know if this refers to a specific chemistry; Envia also describes their chemistry as manganese rich (Li2MnO3 / LiMO2 composite). Manganese is a pretty cheap metal, so it's possible that Farasis has a lower cost per kWh than EIG.

[Lipo423]

Mmmm...if the anode chemistry is Manganese + X  I'm afraid the person that told me about Lipo had no technical knowledge
If they really get to 260Wh/Kg that's a pretty good number (for the used chemistry, I mean)

Price should not be higher then...Let's see

[protomech]

Farasis refers to a Manganese-rich cathode.

[Lipo423]

Yes, I understand, which still means is a Manganese cathode with the good and the bad that implies (briefly):

- Less energy density than Lipo
- Safer
- Longer life than Lipo (charging cycles)
- Heavier
- Cheaper

I would be surprised if they have this "second" generation ready to sell (I mean properly field tested), but who knows, if they have had the funding, they may got there already...

There is a lot to do with Lithium and we are in the "infancy" development stage. When you look at all the different available chemistries (each one of them with good and bad things) it makes fairly complex to bet in what the winner will be.
One of the key factor is the anode chemistry storage limitation, and although there are solutions with Nano-technology still the required long life cycles are not there...will see...

[Tudor]

Since we already are (way) offtopic, again -

One really hopes Zero will be releasing new FX -13 compatible battery packs in the future. Same size, same weight but increased Wh/kg ratio.

[Lipo423]

Tudor,

Do not want to disappoint you, but that is unlikely to be happening...too many companies working in his "own thing" at the moment for Zero to be positioning themselves as "this is the future of our battery packs"

Not good news for us as users, but this is the price you pay for being an early adopter...