Torque

Bike_On

Well-Known Member
The force that accelerates the bike and enables a bike and rider to overcome gravity. It can come from the motor or your legs.

What is torque mathematically? Simply the force at the end of a lever times the distance of the lever.
ex. A typical bike crank is 7 inches. A 200 lb man standing up will create 7 x 200=1400 inch-pounds, or 1400/12 = 116.7 ft-lbs.

Many torque specs are in Newton-meters (Nm). 50 Nm = 36 ft-lbs. So the 200lb man asserts 116.7/36*50 = 162 Nm.

What about ebike motors? Many give a nominal spec and a max spec. A motor will produce a higher torque at SLOWER rmps of the motor. As a motor reaches a max speed, it's torque goes to zero. See the simulator on the ebikes.ca website.

How about comparing ebikes?
The Bosch mid drive specs it's motor at 60 Nm. The Impulse II system is 70 Nm. Neither give an rpm. The Optibike boast a 2.5x a Bosch system, so that is 150 Nm. A Bionx dd hub D-series specs 25/50 Nm, and the Falco dd hub is 40 Nm max. As you can see, the mid drives can put out a higher torque, which is usually attributed to the gearing, while the dd hubs are limited to "one" gear. In order to accommodate speeds at 20 mph+, a balance is struck for torque. More torque, less speed. More speed, less torque.

I am use to power, not torque. What gives? Well, power is directly proportional to torque which is proportional to battery current, FYI. More current> more torque > more power in general. Power is actually torque * rpm (of rotating source). Thus, when you shift down on a bike and spin faster with the same force, your power goes up, and so does your speed. For a motor, very low rotational speeds can be deadly for a motor. Torque may be high, but the wheel needs to spin to produce power. A high torque output at a low speed mean current is high in the motor and things are getting hot. A little leg power is needed to help the motor, or shift down in a mid drive system.

Optibike is doing a blog on torque on their web site, if you want more.
 
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Mike leroy

Active Member
Do you happen to know the lithium-ion chemistry Optibike battery uses?

From their website, I could not determine if it is NMC or another.

Please send the link to the battery chemistry .
 

Racingkyle

Member
The force that accelerates the bike and enables a bike and rider to overcome gravity. It can come from the motor or your legs.

What is torque mathematically? Simply the force at the end of a lever times the distance of the lever.
ex. A typical bike crank is 7 inches. A 200 lb man standing up will create 7 x 200=1400 inch-pounds, or 1400/12 = 116.7 ft-lbs.

Many torque specs are in Newton-meters (Nm). 50 Nm = 36 ft-lbs. So the 200lb man asserts 116.7/36*50 = 162 Nm.

What about ebike motors? Many give a nominal spec and a max spec. A motor will produce a higher torque at SLOWER rmps of the motor. As a motor reaches a max speed, it's torque goes to zero. See the simulator on the ebikes.ca website.

How about comparing ebikes?
The Bosch mid drive specs it's motor at 60 Nm. The Impulse II system is 70 Nm. Neither give an rpm. The Optibike boast a 2.5x a Bosch system, so that is 150 Nm. A Bionx dd hub D-series specs 25/50 Nm, and the Falco dd hub is 40 Nm max. As you can see, the mid drives can put out a higher torque, which is usually attributed to the gearing, while the dd hubs are limited to "one" gear. In order to accommodate speeds at 20 mph+, a balance is struck for torque. More torque, less speed. More speed, less torque.

I am use to power, not torque. What gives? Well, power is directly proportional to torque which is proportional to battery current, FYI. More current> more torque > more power in general. Power is actually torque * rpm (of rotating source). Thus, when you shift down on a bike and spin faster with the same force, your power goes up, and so does your speed. For a motor, very low rotational speeds can be deadly for a motor. Torque may be high, but the wheel needs to spin to produce power. A high torque output at a low speed mean current is high in the motor and things are getting hot. A little leg power is needed to help the motor, or shift down in a mid drive system.

Optibike is doing a blog on torque on their web site, if you want more.
Hi! May I ask you to help me with a little math? I want to figure out if the stealth fighter has enough power to propel me up roughly a 12% grade. I weight 120 pounds. How could I figure that out?
 

Mike leroy

Active Member
Hi! May I ask you to help me with a little math? I want to figure out if the stealth fighter has enough power to propel me up roughly a 12% grade. I weight 120 pounds. How could I figure that out?
I do not find the torque anywhere. I use 5Nm per percent grade as a rule of thumb for 40 pound bikes and 180 pounds, or 220 pounds. Total weight on a SF is about the same, 195. So, you need approximately 60Nm.

My guess is the bike will struggle. Ask around or contact them. The M1 Spitzing is torquey. I just added a paragraph about One.15 torque curve flattening out at 1300W. One.15 and SF have similiar electrical designs in this regard. Torque = Watts / RPM. Adding more Watts reaches the point of diminishing returns pretty fast, because RPMs do not increase very much. The torquey motors are designed to run at low RPMs.

My guess is the bike will bog down over 10% grade. You need to know exactly the grade percentage. You have a slim margin or error above 10% grade.
 

Racingkyle

Member
I do not find the torque anywhere. I use 5Nm per percent grade as a rule of thumb for 40 pound bikes and 180 pounds, or 220 pounds. Total weight on a SF is about the same, 195. So, you need approximately 60Nm.

My guess is the bike will struggle. Ask around or contact them. The M1 Spitzing is torquey. I just added a paragraph about One.15 torque curve flattening out at 1300W. One.15 and SF have similiar electrical designs in this regard. Torque = Watts / RPM. Adding more Watts reaches the point of diminishing returns pretty fast, because RPMs do not increase very much. The torquey motors are designed to run at low RPMs.

My guess is the bike will bog down over 10% grade. You need to know exactly the grade percentage. You have a slim margin or error above 10% grade.
About the M1. If you started in the lowest possible gear, the torque sensor might allow the bike to get a bit of an acceleration. Also, another way to get that much torque and speed would be through a transmition. not sure if it has one or just the sprockets
 

Mike leroy

Active Member
About the M1. If you started in the lowest possible gear, the torque sensor might allow the bike to get a bit of an acceleration. Also, another way to get that much torque and speed would be through a transmition. not sure if it has one or just the sprockets
Kyle,
When it starts getting steep, M1 Spitzing or Focus Thorn Speed is better for you.
 

Racingkyle

Member
Kyle,
When it starts getting steep, M1 Spitzing or Focus Thorn Speed is better for you.
I am going to contact both stealth and Spritzing about heir bikes. I'm quite unimpressed since I've sent focus an email a little over a week ago asking if they use a throttle or pedelec, still no reply.
 

Mike leroy

Active Member
I am going to contact both stealth and Spritzing about heir bikes. I'm quite unimpressed since I've sent focus an email a little over a week ago asking if they use a throttle or pedelec, still no reply.
Focus takes forever to respond. They are big in Europe, but tiny in the USA. I was underwhelmed by their very slow response, too. I have difficulty to take them seriously. Spitzing responded almost immediately.
 

Racingkyle

Member
Focus takes forever to respond. They are big in Europe, but tiny in the USA. I was underwhelmed by their very slow response, too. I have difficulty to take them seriously. Spitzing responded almost immediately.
Should I try contacting them again? If it's this difficult to contact a company customer service in the us must be aweful. same with haibike.
 

Bike_On

Well-Known Member
I do not find the torque anywhere. I use 5Nm per percent grade as a rule of thumb for 40 pound bikes and 180 pounds, or 220 pounds. Total weight on a SF is about the same, 195. So, you need approximately 60Nm.

My guess is the bike will struggle. Ask around or contact them. The M1 Spitzing is torquey. I just added a paragraph about One.15 torque curve flattening out at 1300W. One.15 and SF have similiar electrical designs in this regard. Torque = Watts / RPM. Adding more Watts reaches the point of diminishing returns pretty fast, because RPMs do not increase very much. The torquey motors are designed to run at low RPMs.

My guess is the bike will bog down over 10% grade. You need to know exactly the grade percentage. You have a slim margin or error above 10% grade.
Once the Stealth Fighter gets moving, it will do just fine at 2500W. The other part of the torque equation is how it relates to power: Power=Torque x rotational speed (w).

Starting at 0 mph, the power is zero, even if at max current and peak torque. The power is lost as heat in the motor.
As the wheel rotates, w increases, torque decreases at the same power, but you are gaining speed.etc.

Stealth use to use the Crystalyte 5303 hub. Here is a simulation up to 2100W. It will maintain a speed of 21.7mph on a 12% grade.

upload_2015-4-13_22-27-20.png
 

Attachments

Mike leroy

Active Member
Once the Stealth Fighter gets moving, it will do just fine at 2500W. The other part of the torque equation is how it relates to power: Power=Torque x rotational speed (w).

Starting at 0 mph, the power is zero, even if at max current and peak torque. The power is lost as heat in the motor.
As the wheel rotates, w increases, torque decreases at the same power, but you are gaining speed.etc.

Stealth use to use the Crystalyte 5303 hub. Here is a simulation up to 2100W. It will maintain a speed of 21.7mph on a 12% grade.

View attachment 2723
Very informative! How would it perform on an 18% grade? My hill is 18%. I did not realize it has 24" wheels. How would it perform with 29 inch wheels?
 

Mike leroy

Active Member
Once the Stealth Fighter gets moving, it will do just fine at 2500W. The other part of the torque equation is how it relates to power: Power=Torque x rotational speed (w).

Starting at 0 mph, the power is zero, even if at max current and peak torque. The power is lost as heat in the motor.
As the wheel rotates, w increases, torque decreases at the same power, but you are gaining speed.etc.

Stealth use to use the Crystalyte 5303 hub. Here is a simulation up to 2100W. It will maintain a speed of 21.7mph on a 12% grade.

View attachment 2723
If the bike generates such high torque, why do they not emphasize it on their web site? Torque is very important to us people who live on steep hills? I get so frustrated when torque is hidden. Does it drain the battery too fast?
 

Bike_On

Well-Known Member
I recommend you log into ebikes.ca and play with the simulator yourself. You will learn some good stuff there.
 

Mike leroy

Active Member
I recommend you log into ebikes.ca and play with the simulator yourself. You will learn some good stuff there.
How accurate is the simulator? Does it generate similar torque curves when the bike is put on a dyno? I read an article where people challenged the results. I really have no idea where the truth lies.
 

Bike_On

Well-Known Member
If the bike generates such high torque, why do they not emphasize it on their web site? Torque is very important to us people who live on steep hills? I get so frustrated when torque is hidden. Does it drain the battery too fast?
If you really need torque because of hills, stay away from ddhubs, and go with a mid drive.

IMO, mid drive are a must for super hilly areas and any off road stuff. A ddhub can do hill, but it helps to have momentum and leg assist for the steepest grades.
 

Bike_On

Well-Known Member
that said..... it is easier to talk about power and calculate power. Wind resistance and gravity effects at a given speed will be calculated in power - watts.

Yes, torque is important, only in the sense that you need enough to maintain a speed or accelerate.

Again, nothing, nothing, nothing beats a mid drive, with gears, for overall, across the band torque. Chain issues, transmission, noise, etc, yes a factor, but the motor uses the gears to run at peak power of the motor and max power transfer to the wheel. If you live in Florida flats, go hub, stay silent, and cruise it. I haven't seen a bike to do it all.
 
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