Relationship between watts and torque?

[K PierreR]

So going back to the original question, if you are riding an Ultra or BBSHD equipped bike that has been capped at 750 watts, and you know this because at wide open throttle the motor is only pulling 750 watts as indicated on your display, there is a LOT of power being left on the table. That motor will NEVER climb as well as one that's getting 1500+ watts (or more)....

My question would be can this power that's left on the table be tapped - and the answer is it depends! All of the BBSxx and Ultra's built to date are able to be hacked pretty easily with an inexpensive cable and some shareware loaded on a laptop and taken up to the rated capacity (1600w). The hitch is, my understanding is this is changing as we sit here. The new Ultra motors are being shipped with CAN bus - which is a fancy way of saying our existing cables and shareware are NOT going to work on them. These CAN bus motors are going to be dealer only changes - and that's assuming you can find a willing dealer, AND they have the CAN bus software and know how to use it.....

Where the big confusion come in is how the regulations are actually written. That 750 watts max in the regs is motor output, not battery output. The display reads in battery output. Even under good cadence and higher speeds, a Bafang motor normally needs at least 1000 battery watts to produce 750 motor output watts. At slow motor speeds you could have a full 1500 watts battery draw and be well under 750 watts motor output. The difference is motor efficiencies at low rpm's You would be building up lots of heat but but you don't usually climb at max for very long. Phase runner controllers are good at providing power where needed while staying under the legal limit of motor output.

You have to actually be pretty good at building to actually get a bike that will easily bust the regs on a practical basis and not just a few peaks hear and there. You normally have to look at 60 volts and higher and 20+ pound batteries. When your done with your build, It will look just like a real dirt bike or it will not hold up long to the punishment. It's not even easy to build a bike that will hold up to cruising practically in the upper end of the legal limits (600-750 watts continuous motor output over 30+ miles). It's easier to accomplish that task with a hub motor on pavement than a BBSHD or M620 mid drive. (end of answer)
My conclusions:
There really is no such thing as a stealth bike that will bust the regs on a practical basis. My bike will put out 500-650 watts on a continuous multi hour basis and 750 watts for up to a half hour at reasonable reliability and it looks like a bicycle but it sure as hell isn't stealth. I am quickly realizing that anything above 25 mph and you are much better off to start looking outside of bicycle components and into electric motorcycle components. It's easier to get the damned license and insurance and forget the bike paths. It's a hell of a lot easier, cheaper and practical.

Keep in mind that my answers are very much on the pragmatic end of this discussion and not on the theoretical end at all. It's easy to build a dragster bike that will bust the regs for a couple of miles that holds up as well as a dragster. It's quite another thing to build a powerful reliable very versatile long range electric bicycle. I do not have all the answers to my own questions yet, but I am about put what I have to the real world test where BS kills.

 

[Ebiker33]

The ultra motor via the unlocked display can be moved to 1500W from 750W from the Ebike company who set it there to stay legal.
There is a video of it being done on you tube. I had a conversation with Sondors in the past month and they told me you can do that with their Ebikes with their new mid-drives.
Any ultra with the DPC18 display can do this. I would caution those with throttles, changing it has caused chains to break on full throttle in the wrong gear.
And the problem is not watts or torque. I keep saying this in thread after thread, Ebikes locked to 20 mpg with 3000 watts power are not an issue, but a 750W Ebike going 35mph is the issue, speed is the singular issue getting people in trouble. Who really cares if I am throttling up a 15% grade hill and 20 mph, nobody, maybe just the analog bikes getting passed like they are standing still.
They need to change these archaic laws for mixed trail and road use, give me unlimited watts with a 20mpg speed restriction including throttle, and everything will be good.

 

[AHicks]

Where the big confusion come in is how the regulations are actually written. That 750 watts max in the regs is motor output, not battery output. The display reads in battery output. Even under good cadence and higher speeds, a Bafang motor normally needs at least 1000 battery watts to produce 750 motor output watts. At slow motor speeds you could have a full 1500 watts battery draw and be well under 750 watts motor output. The difference is motor efficiencies at low rpm's You would be building up lots of heat but but you don't usually climb at max for very long. Phase runner controllers are good at providing power where needed while staying under the legal limit of motor output.

You have to actually be pretty good at building to actually get a bike that will easily bust the regs on a practical basis and not just a few peaks hear and there. You normally have to look at 60 volts and higher and 20+ pound batteries. When your done with your build, It will look just like a real dirt bike or it will not hold up long to the punishment. It's not even easy to build a bike that will hold up to cruising practically in the upper end of the legal limits (600-750 watts continuous motor output over 30+ miles). It's easier to accomplish that task with a hub motor on pavement than a BBSHD or M620 mid drive. (end of answer)
My conclusions:
There really is no such thing as a stealth bike that will bust the regs on a practical basis. My bike will put out 500-650 watts on a continuous multi hour basis and 750 watts for up to a half hour at reasonable reliability and it looks like a bicycle but it sure as hell isn't stealth. I am quickly realizing that anything above 25 mph and you are much better off to start looking outside of bicycle components and into electric motorcycle components. It's easier to get the damned license and insurance and forget the bike paths. It's a hell of a lot easier, cheaper and practical.

Keep in mind that my answers are very much on the pragmatic end of this discussion and not on the theoretical end at all. It's easy to build a dragster bike that will bust the regs for a couple of miles that holds up as well as a dragster. It's quite another thing to build a powerful reliable very versatile long range electric bicycle. I do not have all the answers to my own questions yet, but I am about put what I have to the real world test where BS kills.

For most of us (custom direct drive bikes with huge batteries aside), the controller is the determining factor in how much power is available to the motor. Many, including the Bafang in question, are easily adjustable in that regard. If that controller is set to limit the power to 750 watts, that's all the motor is going to get, period!

And I agree that to make a bike legal you can cap the available wattage, OR you can cap the max speed. OR, you can cap both! You can even remove the throttle if you like!

 

[PedalUma]

I am finding that one of the best ways to fly is to throw out weight. One of the bikes I am currently working on will be about 31-pounds when completed. I will confirm this within 24-hours with photos of the scale. It will outperform a 91-pound overclocked Ultra. Less is so much more. As soon as you start making things lighter, everything can be lighter. Brakes, tires, spokes, batteries, motors, rims... And the handling is then vastly improved. With each weight reduction making the bike more fun. It is like running barefoot on the beach instead of running with lumberjack boots. Even wire gauges can be reduced when you are not pushing a barge in the Suez. It is not about power consumption rates, it is about fast fun.

 

[EMGX]

I am finding that one of the best ways to fly is to throw out weight. One of the bikes I am currently working on will be about 31-pounds when completed. I will confirm this within 24-hours with photos of the scale. It will outperform a 91-pound overclocked Ultra. Less is so much more. As soon as you start making things lighter, everything can be lighter. Brakes, tires, spokes, batteries, motors, rims... And the handling is then vastly improved. With each weight reduction making the bike more fun. It is like running barefoot on the beach instead of running with lumberjack boots. Even wire gauges can be reduced when you are not pushing a barge in the Suez. It is not about power consumption rates, it is about fast fun.

That is an incredibly low weight. What bike are you starting with? The TSDZ2 motor is 8 pounds, subtract maybe 2-3 pounds, depending, for the crank assembly it is replacing. Plus battery wt of 5-7 lbs (?) means you must have started with a 20 pound bike? What capacity and weight battery do you use?

I agree about weight being a significant factor, tires too. Personally I have no interest in trying to make up for heavy weight and inefficient tires with higher power or using assist when it wouldn't be necessary with a lighter bike.

 

[PedalUma]

That is an incredibly low weight. What bike are you starting with? The TSDZ2 motor is 8 pounds, subtract maybe 2-3 pounds, depending, for the crank assembly it is replacing. Plus battery wt of 5-7 lbs (?) means you must have started with a 20 pound bike? What capacity and weight battery do you use?

I agree about weight being a significant factor, tires too. Personally I have no interest in trying to make up for heavy weight and inefficient tires with higher power or using assist when it wouldn't be necessary with a lighter bike.

Okay, we will venture off topic for a moment. Forgive me. Do not read this if you want to stay on topic.

Firstly, right now I am fixing a flat: 1) Remove fender 2) Remove Inter-8 clicker 3) Remove brakes 4) Loosen axle nuts 5) Remove kickstand 6) Remove worm gear box.. Who designed this? F!
The lighter bike is an older Marin Highway 1 road bike that is Frankenstein's 1/2 carbon monster. The owner is very small. Count the front spokes by using the fingers of both hands. These are blade spokes. I converted her MTB in December. Her good bike is all carbon and I can't convert that, so we are doing the old Franken-bike. 3.05 lbs. bat. I don't like to show stuff that is not finished but here it is in progress.