This type of discussion makes me less insecure about my 120lb weight lol. Being as thin a telephone pole has aero benefits, rolling resistance, etc. I can also leg press over 600lbs, so I am not super weak or anythint. My first ebike was only 250w and it could get me up the steepest road hills in my escarpment town. Upgraded though cause I didnt like mid drive so much and switched to hubs. It is awesome! So quiet and smooth, no gear changing necessary...she just rips. And absolutely no issues with anything, just attached tk the bike and start riding. It just works. I was able to build my hub motor wheels all by myself with no prior experience, right down to measuring the hubs and ordering the correct length spokes first shot, and it was all just from Grin Tech discussion and tutorials. I had little confidence, but it went so well now I feel like a pro lol. Will be building all my own bike wheels now! I even managed to true my first wheel in only a few minutes with no stand or anything, just a spare bike fork. Honestly, Grin Tech is the reason I felt able to convert my 2010 Trek 3700 into an ebike way better than any of the cheap ones that are still far more expensive. My whole setup wasnt much more than $500, including the bike. Constant compliments and people offering to buy it for far more than I paid. I was run over by a car years ago and havent been fully able to bike like I used to and ebikes gave me a new lease on the hobby I love so much.
Thank you. This is the sort of quantitative evidence based analysis that should inform ebike restrictions globally rather than the current arbitrary limits thought of by some bureaucrat who probably doesn't even ride a bike.
Actually is even worse, most of the original power and speed based regulations were lobbied from within the pro cycling community, who felt that an ebike should be modeled after a human power bike, with all the flaws that entails. Like going super slow up hills, and super fast downhills, limited in cargo capacity, and being at the merci of winds. None of that makes cycling safer on the roads, or more practical and appealing.
13:15 1698 watts “absorbing power” due to wind drag during 60 KPH downhill: as much as I love bombing down a nice, long hill, I set my regenerative braking to limit downhill speeds to 30 KPH when touring in order to minimize these losses and maximize my regen
Hey Justin, on the next part, Please Mention the effects of drafting (slipstreaming) behind large and small vehicles. I'm curious to know what performance gains are associated with these advantages.
That's a much trickier thing to be analytic about and model, but basically it's the same thing as having a small or modest tailwind. The degree depends on how big the leading vehicle is and how closely you follow. The next part is all about motor power, so no more mention of air flow except as it pertains to convective motor cooling.
@@GrinTechnologies Thanks Justin. This is truly valuable content you're putting out there. I, for one, found the section on the hills particularly interesting. This is because I live in Rwanda(aka The Land of a Thousand hills) and i'm designing a mid-drive ebike with the perfect specs to tackle this challenging terrain. If you'd like to know more about my progress, I'd be more than happy to share them with you.
Excellent. You have articulated so very well, that which I know and understand but cannot come close to your educational abilities. I have enjoyed your website and the simulations for some years. Many thanks from Scotland. Looking forward to your next two videos in the series. I’m on my 3rd pedal assist mid drive electric bike. Currently a 2015 Moustache full suspension MTB with many upgrades. Original Bosch CX motor. Works great for an out of puff pensioner like me. Assist opens up new vistas for my age and health!
Folks, was the Ligo 10X abandoned? I had this idea of using specific power cells for a similar purpose, would love to discuss it with y'all if the project is still underway. If it was abandoned, can I use a similar idea non-commercially or have you folks patented the format/application?
Thank you for this video! I recently made a video saying that to calculate an ebikes top speed with ok accuracy, you have to go both ways on a relatively flat runway to negate some of the gravity and wind forces acting on the ebike. Sharing!
That's not exactly calculating your top speed, that's called measuring your top speed! But yeah an easy way to partially negate some environmental factors. You should also do it both sitting upright and in a crouched tuck position.
I had to double take on the formula. Yes, POWER, v cubed, force, v squared. This always makes me squint. Then I think of velomobiles and am still blown (pun intended) away by their efficiency.
In the motor power I’m looking forward to you going through the serial and individual component efficiency of the system from battery through controller to motor and how the graph of that varies with current drawn, rpm etc. I’ve tried having this discussion with Bosch mid drive motor tech guys because their app seems to display power taken from the battery not the actual power added for assistance, which is all very misleading. In fact the app which shows assist vs ride split is pretty meaningless although their human input power is pretty good.
ua-cam.com/users/livedxJe_gygRGU?si=PFwBySpMw-CR2L2V The next video will be purely about power capabilities of motors in isolation, not really the other parts of the system. See the video above if you want an in depth treatment of motor and system efficiency.
Nice job Justin. This video would be great information for policy makers in creating the new regulation standards.? What regulations make sense to you for watt limits?
Limiting watts in e-bike makes no sense as we've seen in this video. Im my opinion the laws and limits for e-bikes should only apply to maximum speeds and where we're allowed to ride. For example, in my small town some of the bike paths have high grade inclines where even a 2000W motor would struggle to drive a rider uphill. If we want a cleaner and more fun future, we have to take fully loaded cargo bikes into account, because for a cargo bike going uphill, 500W or 750W is not even half of the energy needed. Edit: motor gearing will, of course, change the torque power of the bike. I can't wait for the next videos.
That'll be the subject of part 3. But fundamentally yes, power should not enter the regulatory framework at all. Speed and mass are the only things that affect relative road safety, and acceleration limits (to like 0.1 or 0.2g) can very easily and effectively address any concerns about systems being unsafe for inexperienced riders to handle, without any compromise in the ability to climb hills.
The biggest concern I've have had with hub motors is hills and stressing & wearing out the motor. Also dealing with big drops in speed so learning to pick the right hub motor with enough power is very important if you have to deal with lots of hills.
If your are worried about stress and wear on the bike climbing hills, then the suitably torquey hub motor is usually what you want. Stress and wear happens to your drivetrain and brakes which is exacerbated by a mid-motor, and greatly reduced with a hub drive. But as you say, you need to get a hub motor that is sized to your needs (weight and grade hill) and then you can fly up the hills. An undersized hub is underwhelming.
A slightly tweaked version of this: ebikes.ca/tools/simulator.html Just set your throttle to like 5% so that it doesn't entre the equation and hide the motor related curves via the radio buttons on the top of the graph.
@@GrinTechnologies thx a lot ...if you excuse me I would like to ask you a favour ..I am a senior student from Palestine I am building an e-bike with the regenerative braking system as a senior project for the university , and I have watched a lot of your videos that show your huge understanding to this field and exquisite explanations for this topic and I know the thing is too big to be explained on a UA-cam comment..but I wanna your help , in giving me notes website, tutorials, published paper and anything you believe it could help us and give us insights to do things in a better way .. I know it is a lot to ask .. But thanks any way for your help
That will be part of it, geared or DD, just understanding the full map of power output vs rpm vs time for different motor models and what determines those things, and how dumb it is to try and characterize that with a single "rated watts" number.
Great video! Although I'm missing something fundamental (but maybe it was planned for the follow up videos). So all the stuff about maintaining speed (cruising) is very well explained, e.g. that vehicle weight has no effect on "air drag, which is the main force of power needed when you're talking about riding a bike on flat ground". But what I'm missing here is how much power you need to *accelerate* up to your cruising speed, and that you need more power if you want to 1) accelerate faster and 2) accelerate more weight. Anyways, can't wait the follow up video that will convince us all why regen makes so much sense, especially on slower vehicles.
Super good question. I deliberately left out the acceleration power since it has no bearing on the net energy consumption and didn't want to further complicate the equations with transients. Power for acceleration is simply p = m v a. So take your speed (in m/s), the vehicle mass (in kg), and your acceleration (m/s/s), multiply them all together and that is how many watts of power is going into changing your kinetic energy
Strainuous, hard and slow could also explain the age of the rider and the equipment being used. Then when you throw a hill in front of it, might be somewhere off the charts.
Lance Armstrong could not sustain 500 watts for even 30 minutes in his most doped up state. The average power output of leading riders on the tour-de-france is in the realm of 250-300 watts. The word "sustain" is subjective but was intended to mean for a duration of at least 10's of minutes. The power output a human can do in a very short sprint is different (and impressive!)
@@GrinTechnologies All agreed - and certain road, track and BMX cyclists are reported to have exceeded 2000 watts for a few seconds! And even I can get above 1500W for a few seconds - the time is heat limited - using my CYC Photon mid-drive eBike motor on a 48V battery.
I guess your not going to discuss gear multiplication & the effect on energy consumption. I'm sure tons of people would want to know what's roughly ideal for given uphill scenarios, yes weight too. Tire diameter, etc.
As far I know your schema is wrong, frontal air drag caused by high pressure is different air drag flowing along your body. It's not cubic. It's between square and cubic. What about rotational mass and drivetrain efficiency?
Rotational mass has no effect at all on the steady state power needed to move a bike at a given speed, and is a weird and misguided obsession by people who talk about bicycle power. And yes the cubic relation between air drag and power is an approximation for turbulent flow, but is pretty darn close. Errors from this are much less than uncertainty in the CdA approximation so it's rather splitting hairs to do a higher order model of that. The same goes for rolling drag, it's not exactly constant (some speed dependancy exists), but accounting for that in a complicated model would change anything about the result.
You'll notice we are careful to say 8 times the power, not 8 times the force. Power is force times speed, so if force to air drag increases at the square of your speed, then power increases at the cube.
you say at 2.39 "air resistance has a property that it increases with the cube of your bicycle speed" that is very interesting as i thaught it was mass times velocity squared that determined force. looks like i may not fully understand why drag creates a cube ...i guess with drag the force is in front and behind the object creating a force on the object higher than the frontal drag force alone. I need to up my considerations of drag..thanks for the education.
@@russellwilson5246 The drag force increases with the square of speed, hence the drag power increases with the cube of speed. In a similar way, rolling friction force is independent of speed, while the power to overcome rolling drag increases linearly with speed. In this video everything is in the context of power (ie watts), so when I mention rolling and air friction quantitatively it's about the power needed to overcome them and not the force needed to overcome them.
Finally, someone who understands electricity! It's amazing the number of people who don't understand Watts.
Thanks Justin. Beautifully explained and illustrated.
This type of discussion makes me less insecure about my 120lb weight lol. Being as thin a telephone pole has aero benefits, rolling resistance, etc. I can also leg press over 600lbs, so I am not super weak or anythint. My first ebike was only 250w and it could get me up the steepest road hills in my escarpment town. Upgraded though cause I didnt like mid drive so much and switched to hubs. It is awesome! So quiet and smooth, no gear changing necessary...she just rips. And absolutely no issues with anything, just attached tk the bike and start riding. It just works. I was able to build my hub motor wheels all by myself with no prior experience, right down to measuring the hubs and ordering the correct length spokes first shot, and it was all just from Grin Tech discussion and tutorials. I had little confidence, but it went so well now I feel like a pro lol. Will be building all my own bike wheels now! I even managed to true my first wheel in only a few minutes with no stand or anything, just a spare bike fork. Honestly, Grin Tech is the reason I felt able to convert my 2010 Trek 3700 into an ebike way better than any of the cheap ones that are still far more expensive. My whole setup wasnt much more than $500, including the bike. Constant compliments and people offering to buy it for far more than I paid. I was run over by a car years ago and havent been fully able to bike like I used to and ebikes gave me a new lease on the hobby I love so much.
Is hub better because it is more direct?
❤
leg press over 600 pounds?! Wow. I guess you never skip leg day.
Thank you. This is the sort of quantitative evidence based analysis that should inform ebike restrictions globally rather than the current arbitrary limits thought of by some bureaucrat who probably doesn't even ride a bike.
Actually is even worse, most of the original power and speed based regulations were lobbied from within the pro cycling community, who felt that an ebike should be modeled after a human power bike, with all the flaws that entails. Like going super slow up hills, and super fast downhills, limited in cargo capacity, and being at the merci of winds. None of that makes cycling safer on the roads, or more practical and appealing.
Thanks Justin! Looking forward to pt 2.
So much needed theory for bike world, clearly and simply explained. Thank you Justin and GRIN Tech team!
Looking forward to Part 2. Thanks.
Great start, now where are PARTS 2 & 3 ???
Another excellent video. Thank you for continuing to produce high-quality educational content like this.
13:15 1698 watts “absorbing power” due to wind drag during 60 KPH downhill: as much as I love bombing down a nice, long hill, I set my regenerative braking to limit downhill speeds to 30 KPH when touring in order to minimize these losses and maximize my regen
Thank you Justin! I forget how powerful the grin motor calculator is. It's fun to play with!
Thanks very much for this very informative video. Looking forward to next...
What a great job presenting! Looking forward to next.
Hey Justin, on the next part, Please
Mention the effects of drafting (slipstreaming) behind large and small vehicles.
I'm curious to know what performance gains are associated with these advantages.
That's a much trickier thing to be analytic about and model, but basically it's the same thing as having a small or modest tailwind. The degree depends on how big the leading vehicle is and how closely you follow.
The next part is all about motor power, so no more mention of air flow except as it pertains to convective motor cooling.
@@GrinTechnologies Thanks Justin. This is truly valuable content you're putting out there. I, for one, found the section on the hills particularly interesting.
This is because I live in Rwanda(aka The Land of a Thousand hills) and i'm designing a mid-drive ebike with the perfect specs to tackle this challenging terrain.
If you'd like to know more about my progress, I'd be more than happy to share them with you.
Excellent. You have articulated so very well, that which I know and understand but cannot come close to your educational abilities. I have enjoyed your website and the simulations for some years. Many thanks from Scotland. Looking forward to your next two videos in the series.
I’m on my 3rd pedal assist mid drive electric bike. Currently a 2015 Moustache full suspension MTB with many upgrades. Original Bosch CX motor. Works great for an out of puff pensioner like me. Assist opens up new vistas for my age and health!
That was just so informative, even my simple brain was able to follow along. Thank you!
So thankful for this, guys!
Folks, was the Ligo 10X abandoned? I had this idea of using specific power cells for a similar purpose, would love to discuss it with y'all if the project is still underway. If it was abandoned, can I use a similar idea non-commercially or have you folks patented the format/application?
Thank you for this video! I recently made a video saying that to calculate an ebikes top speed with ok accuracy, you have to go both ways on a relatively flat runway to negate some of the gravity and wind forces acting on the ebike. Sharing!
That's not exactly calculating your top speed, that's called measuring your top speed! But yeah an easy way to partially negate some environmental factors.
You should also do it both sitting upright and in a crouched tuck position.
@GrinTechnologies oh yeah that's true!
I am a molecular biologist, but also like physics. Great teaching!
Thanks for watching!
I had to double take on the formula. Yes, POWER, v cubed, force, v squared. This always makes me squint. Then I think of velomobiles and am still blown (pun intended) away by their efficiency.
In the motor power I’m looking forward to you going through the serial and individual component efficiency of the system from battery through controller to motor and how the graph of that varies with current drawn, rpm etc. I’ve tried having this discussion with Bosch mid drive motor tech guys because their app seems to display power taken from the battery not the actual power added for assistance, which is all very misleading. In fact the app which shows assist vs ride split is pretty meaningless although their human input power is pretty good.
ua-cam.com/users/livedxJe_gygRGU?si=PFwBySpMw-CR2L2V
The next video will be purely about power capabilities of motors in isolation, not really the other parts of the system. See the video above if you want an in depth treatment of motor and system efficiency.
Wonderful explanation, thanks! Greetings from Czech Republic ;)
Nice job Justin. This video would be great information for policy makers in creating the new regulation standards.? What regulations make sense to you for watt limits?
Limiting watts in e-bike makes no sense as we've seen in this video. Im my opinion the laws and limits for e-bikes should only apply to maximum speeds and where we're allowed to ride. For example, in my small town some of the bike paths have high grade inclines where even a 2000W motor would struggle to drive a rider uphill. If we want a cleaner and more fun future, we have to take fully loaded cargo bikes into account, because for a cargo bike going uphill, 500W or 750W is not even half of the energy needed.
Edit: motor gearing will, of course, change the torque power of the bike. I can't wait for the next videos.
@@yvan2563 Exactly. The only thing necessary is speed limits on paths where children or other vulnerable bike users are present.
That'll be the subject of part 3. But fundamentally yes, power should not enter the regulatory framework at all. Speed and mass are the only things that affect relative road safety, and acceleration limits (to like 0.1 or 0.2g) can very easily and effectively address any concerns about systems being unsafe for inexperienced riders to handle, without any compromise in the ability to climb hills.
Excellent video thank you!
Awesome vid, clearly presented, thanks!
Fantástico your Chanel, very usefull, saludos from Spain!
Gracias por mirar!
The biggest concern I've have had with hub motors is hills and stressing & wearing out the motor. Also dealing with big drops in speed so learning to pick the right hub motor with enough power is very important if you have to deal with lots of hills.
If your are worried about stress and wear on the bike climbing hills, then the suitably torquey hub motor is usually what you want. Stress and wear happens to your drivetrain and brakes which is exacerbated by a mid-motor, and greatly reduced with a hub drive.
But as you say, you need to get a hub motor that is sized to your needs (weight and grade hill) and then you can fly up the hills. An undersized hub is underwhelming.
great presentation , i would like to know what is the program which you are using in the simulation to get the result and the curves ?
A slightly tweaked version of this:
ebikes.ca/tools/simulator.html
Just set your throttle to like 5% so that it doesn't entre the equation and hide the motor related curves via the radio buttons on the top of the graph.
@@GrinTechnologies thx a lot ...if you excuse me I would like to ask you a favour ..I am a senior student from Palestine I am building an e-bike with the regenerative braking system as a senior project for the university , and I have watched a lot of your videos that show your huge understanding to this field and exquisite explanations for this topic and I know the thing is too big to be explained on a UA-cam comment..but I wanna your help , in giving me notes website, tutorials, published paper and anything you believe it could help us and give us insights to do things in a better way .. I know it is a lot to ask ..
But thanks any way for your help
Very nice. Is part 2 going to talk about how long it takes to burn out geared hub motors under various conditions?
That will be part of it, geared or DD, just understanding the full map of power output vs rpm vs time for different motor models and what determines those things, and how dumb it is to try and characterize that with a single "rated watts" number.
very informative, can’t wait for the next episode
Thanks for this very educational video 🙏
Great video! Although I'm missing something fundamental (but maybe it was planned for the follow up videos). So all the stuff about maintaining speed (cruising) is very well explained, e.g. that vehicle weight has no effect on "air drag, which is the main force of power needed when you're talking about riding a bike on flat ground".
But what I'm missing here is how much power you need to *accelerate* up to your cruising speed, and that you need more power if you want to 1) accelerate faster and 2) accelerate more weight.
Anyways, can't wait the follow up video that will convince us all why regen makes so much sense, especially on slower vehicles.
Super good question. I deliberately left out the acceleration power since it has no bearing on the net energy consumption and didn't want to further complicate the equations with transients. Power for acceleration is simply p = m v a.
So take your speed (in m/s), the vehicle mass (in kg), and your acceleration (m/s/s), multiply them all together and that is how many watts of power is going into changing your kinetic energy
With regen, the acceleration term is negative and so you get negative watts, the power of your kinetic energy returning to the battery system.
EXCELLENT!!!
Awesome Video!
I haven't even watched yet and I agree.
I watched the video in full, it was very informing. Thank you sir.
wath is the calculator used?
That's all done using our motor simulator web app
ebikes.ca/tools/simulator.html
Strainuous, hard and slow could also explain the age of the rider and the equipment being used. Then when you throw a hill in front of it, might be somewhere off the charts.
How do I find part 2❔🤞
Not yet filmed :-(, but still in the plans for upcoming video projects
Part 2 please!
That's why I love physics, and explains how my BionX feels like riding with a tailwind!
I used to say it felt like the hand of God was pushing me along, but a tailwind is just as apt!
This was just Whatt we needed.
Great presentation, useful data, thanks.
Justin: "1250W is way more than any human can sustain".
Tour de France winner: "Hold my beer ... "
Lance Armstrong could not sustain 500 watts for even 30 minutes in his most doped up state. The average power output of leading riders on the tour-de-france is in the realm of 250-300 watts. The word "sustain" is subjective but was intended to mean for a duration of at least 10's of minutes. The power output a human can do in a very short sprint is different (and impressive!)
@@GrinTechnologies All agreed - and certain road, track and BMX cyclists are reported to have exceeded 2000 watts for a few seconds! And even I can get above 1500W for a few seconds - the time is heat limited - using my CYC Photon mid-drive eBike motor on a 48V battery.
I guess your not going to discuss gear multiplication & the effect on energy consumption. I'm sure tons of people would want to know what's roughly ideal for given uphill scenarios, yes weight too. Tire diameter, etc.
As far I know your schema is wrong, frontal air drag caused by high pressure is different air drag flowing along your body.
It's not cubic. It's between square and cubic.
What about rotational mass and drivetrain efficiency?
Rotational mass has no effect at all on the steady state power needed to move a bike at a given speed, and is a weird and misguided obsession by people who talk about bicycle power.
And yes the cubic relation between air drag and power is an approximation for turbulent flow, but is pretty darn close. Errors from this are much less than uncertainty in the CdA approximation so it's rather splitting hairs to do a higher order model of that. The same goes for rolling drag, it's not exactly constant (some speed dependancy exists), but accounting for that in a complicated model would change anything about the result.
are you sure dobbling the wind resistance caused 8 times the force?...i thaught it was 4 times.
You'll notice we are careful to say 8 times the power, not 8 times the force. Power is force times speed, so if force to air drag increases at the square of your speed, then power increases at the cube.
you say at 2.39 "air resistance has a property that it increases with the cube of your bicycle speed" that is very interesting as i thaught it was mass times velocity squared that determined force. looks like i may not fully understand why drag creates a cube ...i guess with drag the force is in front and behind the object creating a force on the object higher than the frontal drag force alone. I need to up my considerations of drag..thanks for the education.
@@russellwilson5246 The drag force increases with the square of speed, hence the drag power increases with the cube of speed. In a similar way, rolling friction force is independent of speed, while the power to overcome rolling drag increases linearly with speed. In this video everything is in the context of power (ie watts), so when I mention rolling and air friction quantitatively it's about the power needed to overcome them and not the force needed to overcome them.
Best example to be an engineer: Justin!
GRIN... Ebike aliens from a future better universe. So much knowledge 😮
I would never ride my bike through Watts! 😳