Dudes, we literally just got a collage course in motors and ebikes. There's so much here I have to watch it several more times. Thanks so much Justin and GRIN! Looking forward to a future Regenerative Braking seminar!!!
* college course. A collage course is for kindergarten and shouldn't last for 2.5H. ;) I didn't watch the presentation yet, but I already know it's gold.
Excellent video. As a mechanical engineer, I've always felt a bit uneducated when it comes to electric motors. Now I feel I have a basic understanding of the design parameters important to at least one type of electric motor. Thanks.
Old as dirt. Same profession. Same e-tech intimidation. Same flow of understanding from Justin. Same emotion. After 2yrs research, last year I bought an e-bike to exercise/ commute. Hardly ever had anything mechanical I didn't take apart and repair just for kicks, I was forced to learn electronics or suffer a 'genetic pre-dispositions to tinker' crisis. I quickly found the master I trust and determined to catch the whipper-snapper in next couple years, I began absorbing his free educational publications. Chipping at a rock, or taming nuclear isotopes, while materials and tech change, we Engineers design and build stuff. Something's changed ???
There is a boat load of very good information presented...especially starting at 2:16:15 when discussing the Kv rating of a motor and torque per amp. Everyone interested in ebikes needs to understand this concept IMO :).
Thank you so much Justin for this presentation! IMHO this is exactly the way how people should work together on our nice planet, sharing is caring at it's best. For sure you will get tons of positive feedback back to you, which also helps you and your business. I'm also totally looking forward to the Regenerative bracking video. Cheers & take care, Martin
WOW ! One key to Justin's success is plain talk with science metric validation (the "Motor Simulator" is awesome). Another's a love of knowledge and a will to share it. A rare bird, a Professor in the e-bike world, reading posts at endless sphere's forums you learn to respect him quick. The more you come to know hands-on, the more he's validated. The Man's a Giant
I think its a great idea to have more seminars like this one. I found the things you were able to break down super useful and in this format I think will save me hours and hours of gleaning it from forums and disparate resources. Thank you guys again for being one of the technical go to's for our industry. PLEASE DO MORE! YOUR KNOWLEDGE IS POWERFUL! THANK YOU FOR SHARING!!!
You have the heart of a true science educator. You have my heart too. If only everyone understood what you do. Thankyous seem pathetic. Whatever you have to say about regeneration will demand my best attention.
Practically every question I had about how motors and motor controllers work was answered here. That was a LOT of work done in the interest of public education. Thank you.
I’m with you! There are applications and riders for whom a mid drive may be preferential, but if I had to choose one forevermore, I’d take a hub motor without a second thought - direct drive or geared… nylon gears and all.
this is absolutely wonderful. THANK YOU JUSTIN. i have an 800watt front hub motor ebike and a 1500watt rear hub motor ebike both direct drive chinese voilamart. both with home built batteries the 1500watt has 208 (yes 208) 18650s. the internal controller on the 1500 watt fried after 60km so im running an external controller now and its great. your video has answered every question i have about these motors thank you! no seriously THANK YOU! ps i saw some video of you on that solar ebike thing to china with you (and your nearly wife) doing the rowing thing and the pedal thing. great stuff best wishes from Manchester UK.
I like hub motors but one caused me to break my hip. This was due to carving while using the regen. I hit some dirt on a potholed road on a bike with no suspension and a very heavy smart bion x. Always turn off regen when you don;t need it or if the roads are wet and you are cranking. It's like pulling the rear brake when you down want to. I was flying down a very steep hill to go pick my son up from school. I started to slide down the road and the bike went much further. Either the top of the femur snapped off as i initially fell or it was possible i hit a pothole with my feet as i was trying to slide onto my feet. Now i have 3 huge screws and a big risk that the bone will die as the artery inside the bone that feeds blood to the end is quite likely to be damaged. This could well mean a trip back to a hospital for a hip replacement which i really don;t want. Lets hope the artery is ok and i can perhaps have the screws removed if i'm lucky.
I’ve been experimenting with pure silver stator windings. Copper windings when they heat up experience what’s called the “corona effect”. Resulting in loss of power linear to the amount of heat produced. Electricity travels through fields not the wire itself. The heat interferes with the fields. Seems I’m getting about 15% more efficiency at full power. Silver is expensive and I don’t think it would be commercial viable except in very high end applications.
Very informative. Cleared up some basic misconceptions. Looking forward to you getting deeper into some of the topics you didn't have time to cover today.
A fun fact that your readers might already know - in the EE motor calculations, actually there is only one figure for the 'motor constant' that links speed to voltage, and torque to current. It is only the departure from the pure SI units, to things like RPM or kph, that makes the two constants look different. Not wishing to stir anything up, but that's why design/analysis engineers love SI units - metres, seconds, Newtons etc - all those awkward conversion constants disappear! You can do all the sums easily, then convert the final answers to our real-world units.
This is way beyond my level. I have a ways to go before I can fully understand this video. But, I'm very impressed. I'll be buying my parts and kits from Grin. I understand enough of this to see that they know their stuff.
ebikes.ca/learn/why-hub-motors-are-awesome.html In our experience most people into serious commuting, serious reliability, or serious distance trips opt for hub motors, but many people have differing opinions which is perfectly fine.
@@GrinTechnologies And you see no disadvantage to unsprung weight? Maybe the 20K miles I have on mid-drives isn't serious. Love to get "serious" with ya sometime. 25 Jul 20 - Mowich Lake www.relive.cc/view/v8qkd2LGdKv photos.app.goo.gl/hRSTYZ8UjzdpuQ7n8 26 Jul 20 - Rain Forest trail www.relive.cc/view/vQvyDGe2W4q - prnt.sc/tsxt5p photos.app.goo.gl/WcoVAreB4TUdAiPF7 ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-WwwdaVg4Y5M.html
Thank you so much for this valuable lesson and for your hard work and..Ive been riding ebikes since 2008... Just knew the industry would explode one day. I've been involved in electro mechanical work in Large printing systems over 30 years so I got alot out of your lesson. Was especially impressed with your work using small wind tunnels to measure stresses on motors and using vent holes. Wanted to mention thought I don't know how I feel about the thru axel motors you mentioned. They sound good but in my experience anytime I've had to slide out an axel on any gear in use more than a few years it inevitably sticks and I have to fight with it.
Have you thought about a chat with Monro and Associates to look at long term manufacturing solutions? It seems like you have more understanding of the full market than most.
A major focus of my experimentation is finding ways to tailor the voltage & current output to an optimal needs of the specific motor being used on a given build. I have had some success using boost converters and even an MPPT charge controller with DC/DC capabilities, but from one motor/controller combination to another the net results can vary greatly. What advice can you give for finding the sweet spot for a specific motor and conditioning the battery output to match the optimal needs of the motor. I typically try to employ 36-48v motors, coupled with a beefy controller capable of tolerating 60v or modifying the controller to support the higher voltage, then running 2 battery packs where possible, at a college that generally supply 12v more than the voltage rating of the components. I have also had some success back charging the battery packs using a DC/DC boost charge controller. All things optimal, this approach has at times been incredibly effective but I'm done setups it has failed to produce results. I generally use fairly cheap, but high capacity Chinese battery packs or custom built packs as my power source cheddar I've found it more advantageous to have 2 or 4 cheap batteries than just one at the same cost. I have designed a DC/DC boost converter that I hope will expand the possibilities for disking up an optimal voltage but I am very interested in hearing your thoughts. Overvolting a 48v system with 60v seems to bring the best results.
56:14 More current coming out than going in? That's a new one on me. I feel like some subtle electronic details have been glossed over for us simpletons.
Yes, I'd love to do a more detailed explanation of motor phase and battery currents, but the trick to understanding this detail is just to understand how a DC-DC buck converter works. en.wikipedia.org/wiki/Buck_converter
Love it. Thanks In a dual motor configuration in an ebike, being one in the front and 1 rear hub motors, if the ebike is solely used for single motor only being the rear, does this prematurely speeds up the wear and tear of the front motor? TIA
Short answer is no. Just having the hub spin without being powered does not cause wear and tear on anything other than the ball bearings. That said, you should only be doing this (running one motor and not both of them) if the front motor is a geared motor that freewheels. If it's a non freewheeling motor, then you should still be using it too for maximum system efficiency.
New at this, a little overwhelming. Listen, emotor genius - (you are) - hope you'll still take a few minutes to help a beginner, not for sport, but for a quality of life issue. We're stuck in eastern europe without a car because of the pandemic. Groceries and especially drinking water are heavy. So we got bikes, racks, bags and backpacks. Borrowed a welder and made a wagon out of a handtruck which is towed as a trailer. Getting older. 2 much pedaling. Bike store has hub motor kits. Got 2, one for my wife. My bike is doing its best imitation of a cargo bike. The kit is a generic 1200W hub motor (biggest avail.) with a 48V battery having 11.6 amp/hrs run through a 22 amp controller. This was the best I could do from available stock. The supply chain is down they tell me and we had to make kits from in stock items - as the option to order things is like, not really. So kept things as simple as possible and we don't run pedal assist or motor cut-off brakes. Having this power helps greatly but I need more oomph because this bike pulls loads, for us it's a pickup truck. From doing some research before buying anything I was hoping for a 1500W motor, minimum 30-35 amps on the controller, and at least 17 amp/hrs on the battery, but was disapointed with the specs that had to be settled for. Also saw things others say will boost power. What's the truth? Is there any benefit to running a thicker main power wire to the motor? And if the supply chain opens up: What component changes would be most beneficial in the torque department for this motor? Going to a 52 or 72 V battery? Or a controller with a higher output? Or both in what combination? Or something else I dont know about? Also seriously considering front hub kit to make 2WD. Some in stock. Call it a matter of situation and availability that for us this may be the only way to get more grunt out of our main mule right now. Front motor kit would be a completely separate/isolated system from the rear with its own battery, controller and thumb throttle on the left. What I don't know is if it's important that the 2 motors front and rear have the same wattage? If the biggest front kit available is 750 watts/48V is that a problem? I'm thinking torque is torque, and more is more, and anything contributed by the second axle would be cumulative and increase overall torque. So that even adding only a 500W / 36V system on the front would be beneficial to overall torque. Am I thinking right? What's your best advice for getting more power from what I have, and what do you think of the whole 2WD thing? Thank you in advance.
Most specific, where do you get your battery build supplies, zinc strips, flux, soldering wire. Which is best D.C. spot weld, or soldering gun, if gun minimum wattage so as not to cook battery
Hehe... Lord Justin... Lock here from Toronto... yeah, still alive... hehe... Rolling today on direct drive gearless hubbie... plus am rebuilding a bike w/a 10yr. old front Crystalye - ex-proto "police electric motorcycle" mod'ed first for US Virginia highway patrol... ;) Success to you and yours and team at ebikes.ca... and all speed ahead...
@@lockhughes I just got back from Loblaws wearing an orange rain shell with reflective stripes, but I'm fat, thus "pumpkin". What I was really getting at is that people (READ: drivers) barely give cyclists any regard, and the bike, none at all. I make myself as huge as I can approaching intersections, and ready my bell and "HEEEEEY!" as well (though I should really get a horn). Cheers from Ottawa.
Could a motor casing remain closed for protective purposes but have strips of copper welded to it with curved/frayed ends to dissipate heat? This might add drag and cause some wind noise, but the extra heat taken away by the air might allow for significantly more watts. Yes?
@@GrinTechnologies I’m not sure what a stator is. But would ferro fluid solve this? Also, I wrote that comment before I discovered the heat sink, which is almost exactly what I “invented” in my mind.
Hi Rob, yeah the target here was people who at least had a foundation in electronics and basic technical knowledge, but were maybe puzzled or misinformed in how all the pieces fit together. We'd love to do some separate videos that explain the practical ramifications of these findings without the technical details, so at some point that will be on the books. Thanks for your interest.
Great presentation, if possible can you give me your thoughts on the advertised motor setup for the soon to be released Monday Motorbike Gateway Booster. This is what I have been able to get from the co. Bafang internal gear Motor brushless Rear Hub 48v 1200w controlled w/ pedal assist / Rotating speed = 245 RPM . Have not been able to get any more specs or seen reviews on this motor, I do not know if it is a custom motor made for that co. or if it is a commercial model motor. Any thoughts or other info on this model motor would be very appreciated. Thanks!!
I realy love your vid and preseate your shering your knolege, can you do vid of controller and weekinig feild( difrent betwean basrunner, phaserunner , stok controller)? TNX Alot
Yeah, I'll put this on our list of future video topics since its one that isn't very well explained elsewhere at the moment. But before we do that we will want to get a lot of measured data to present which backs up the theory so maybe not until later on in the summer.
very good...a single speed bike is good if you run in a 5 to 10kmph band of speed ....i hear you say a mid drive motor is the same as a geared motor...well yeah to the cranks but beyond that there is a diferance of 300 to 400% in gearing.if you want a sweet spot on eficiancy or power or below over heat change gear.between the human and the motor is an agreed narow band of rpm between these 2 and the road there is a lot of negotiation.
One of the large misunderstandings people have about electric motors is this idea of a "sweet spot". There is no such thing as some narrow sweet spot for electric motors, they produce torque equally well over all speed ranges. The human legs are very different though, and really do operate best in a pretty narrow band of pedal RPM's which is why bikes require such wide gear range with so many steps.
@@GrinTechnologies very good you responded on the topic of power from a motor but left out the topic of eficiancy and the heat generated/lost energy when out side of best eficiancy that you showed us on your chart.this topic is a large portion of your fantastic talk here. it seems to me that if you want to avoid energy loss as heat then keeping a motor in this best eficiency "sweet spot" then a range of gearing will do this...now remember you said a geared hub motor is the same as a mid mount motor...im not convinced that is true.not when there are gears avalable.im going to watch your talk again and pay close attention to power/tork.maybe i will learn some thing.
Justin. Have you ever seen delamination on DD hubs? My only concern with a front DD hub is that the magnet's glue deteriorates over time and could lead to catastrophic failure with the front wheel locking up.
On direct drive motors if the magnets do come loose (as we showed in the photo of the Crystalyte Crown hub) they stay attached to the rotor, they won't jump onto the stator and they don't cause the wheel to lock up or any catastrophic failure like that. Just a very substantial reduction in motor torque ;-) This is an extremely rare problem from manufacturing defects of incorrect adhesive application, normally the shear strength of the magnet glue is way way more than the force on the magnets from the current flow in the stator.
@@GrinTechnologies ok thank you. I have been running your rear hubs now for a few years but would like to try the front hub system for spoke longevity (equal tension both sides) and then run a Rolhoff on the rear. Thanks again for your response
Ha ha, just a small souvenir from the most memorable visit to the sagrada familia a few years ago! Though I like this one even more: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-B8Uh4onqTAU.html
Justin, one question, imagine we have a hill 15%, and torque required to climb it is 100 N.m. Now let's assume we have 2 identical e-bikes, same battery, same controller, same settings, but one motor is 3t and another is 6t. So we turn throttle to 100% and start climbing. Motor provide same Phase amps, enough to ride uphill on 6t and 3t. 6t motor accelerate 2 times faster to some speed X km/h, can we have a situation when motor with 3t will not even reach the X speed with same Phase Amps ? I think when we say that 3t can climb as well as 6t motor we forget that crossection of the phase wire for the motor is the same, and doubling the phase currecn on 3t ebike will cause 4 times more heat losses on a phase wires. Is it correct? Thank you for answer!
If you have half the turns you have double the area and half the length. So you have 1/4th the resistance and can handle double the current for the same resistive loss. 2x area = 1/2 resistance. 1/2 length = 1/2 resistance. 1/2 * 1/2 = 1/4. You wouldn't use the same battery and controller for different motors. You can use a battery that is half the voltage for the lower turn motor and you can use lower voltage power electronics which can handle more current.
Hi there, yes you are totally correct it would mean 2x the phase amps which would mean 4x more heating in the phase wires. However, in a 3T motor that does 100 Nm of torque, you would expect the motor to be produced with a heavier gauge wire to accommodate it. We used 4mm^2 wire on the GMAC and 3.3mm^2 on the Grin All Axle and with that kind of gauge this is not usually a limiting factor. Normally the limit is in the motor controller. But it is true that other motors often have thin (1.5-2mm^2) phase wires and there that can be the practical bottleneck to faster motor winds. To the first question though, if the motor controller is phase amps limited (not battery amps limited), then yes for sure there is a very big performance difference in your scenario, and the 3T motor might not be able to climb a hill at all if the phase current limit of the controller results in less than 100 Nm. It's not just that it wouldn't reach the same speed, it wouldn't even move at all. But just remember that's the fault of the controller, not the motor ;-) The motor would be happy to do more torque and climb, but your controller is not allowing it.
Hi very informative video! Love it! I have a question i hope to be awnserd. I have a Mac motor 10T and a 52V battery. Is it safe to put 60A (86A pahse) without it breaking down too fast?
An afterthought: Justin, after watching you manipulate the simulation to show us that the fast winding didn't really change performance (by any metric?) up until the slower wound motor couldn't keep up, where the fast winding had an advantage, why wouldn't you just ALWAYS WANT a fast-wound motor? Is there less magnetic interaction at slow speeds, and thus lower torque and lower power?
Because a) not everyone wants the ability to go fast (this is true for LOTS of people) and b) In many systems, there are bottlenecks in the connectors, the phase cable wire gauge, and the controller mosfets that limit the ability to run at the higher phase amps that are required by a faster motor winding. In these cases you often will get better performance with a lower motor winding.
@@GrinTechnologies I still dont understand that.. when you need more phase amps on faster motor, copper in the engine wont get hotter because of more amps flowing through the motor?
Yesterday i rode home from a friend's place who lives about 1,000 feet above me near Lake Superior. On the brakes most of the way and was wishing i had regenerative braking. In a hilly city this would seem to be an ideal system. But i need torque and power for climbing too. When i look at the motor systems on the Grin website i am at a bit of a loss on what to choose. Pretty sure i could use only a front brake along with a rear motor hub with regenerative braking. My current bike uses a BBS02 with a 20ah battery, 42t Lekkie ring. It has good range and climbs really well. I would like similar performance with a regenerative rear hub set up for my next build. I have a 20 year old Trek hard tail for a donor bike.
Hey there, any of the more powerful hub motor options would be fine. RH212, GMAC, Grin All Axle, Crysatlyte 'H' series etc. If you want to keep your mid-drive on there and just add a 2nd hub motor for regen, then it makes sense to go with the lightest which is the Grin All Axle hub on the front.
Considering the GMAC, with reverse drive function, would there be a possibility of inducing brakeforce modulation like ABS, instead of regen braking? What could be the possible implications one could face, if a program is generated for carrying out such function.
If you want to make your own circuit to modulate the braking intensity it's quite simple as it's just an analog signal. We haven't seen any need to do that or to experiment with that, and smooth steady regenerative braking seems to be what most people want.
Another query I wanted to add, since the Covid-19 has affected the supply chain across the World, are there any magnetless motors based on the Induction Motor or the Switched Reluctance Machines for hub motor application for ebikes, coming to the market or you would be bringing in your portfolio?
One where the controller is no longer the bottleneck for performance. If you find that the controller overheats or goes into thermal rollback well before the motor, then it would be a sign that you should get a larger controller. If the motor gets really hot before the controller does, then you could probably get away with a smaller controller.
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were is the part of re-gen ? is it in the motor already? how do i know if i have re-gen ? or do i need to add something ? i got a direct drive motor 2000w
hi justin , is it correct that every bldc motor with a given Kv has a fixed nm/A rating? i think not . you can not compare an outrunner with an inrunner or an axial magnet motor like the ME1304 motor
It is correct and your presumption is wrong. If you know the Kv, you now the Nm/A, and you can 100% compare outrunners with inrunners with axial flux motors this way.
Yes, this would be a great topic too and could go over how to create those values for doing a custom motor with our simulator. All you need for this is the ability to run the motor at two different voltages, and the ability to measure both the RPM and the current draw at each voltage. So it's actually within the reach of what a lot of people already have in their toolkit.
why nylon gears you would think aluminum would be better thats what i would machine they even use nylon in lathe gears from a machinist point light metal would be better for gearing.
How reliable is the Bionics motor ? I am thinking of doing a swap my Honda 250 for a Mercedes smart electric E bike. I know it is a pretty old design but the build quality looks good. I would appreciate your opinion before I make the trade .
It's a fine motor if it's working well, but it's a proprietary system and BionX is no more. See ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-Wc8OJtFRUng.html
Even without the added effect of internal pressure you get leakage. Oil is just by nature very leaky. The solution is to have a hub specially built with 'O' ring seals or similar around all areas of contact with oil that could lead to egress from the hub.
Justin meant "elastic" deformation for the steel fork as opposed to plastic. Elastic deformation the fork will return to where it started and plastic deformation means it is permanently deformed and will not return to its original shape. Just trying to help :).
You didn't cover acceleration in your video. Would be interesting to compare an acceleration chart with various motors and parameters. I have a question about a homemade e-bike unlike anything you've covered. I have a 36v lithium battery pack going thru a 500-watt controller to a 12v 500 watt brushed motor that lists 2,750rpm with a gear thru chain to rear wheel on a 26-inch bicycle so that top speed is about 30mph with a 120 Lb rider. I have not ridden it enough to figure out what is going to fail. What simulation can you run to help me figure it out? I have a spare 36-volt motor to replace when the 12 motor fails, but the 12-volt motor is faster.
Acceleration is just the net thrust divided by the vehicle mass, so it's quite easy to compute and is shown directly on our motor simulator in the bottom right. There is nothing at all about modeling the motor's power output with the simulator tool that will tell you want component will fail in your DIY ebike drive system. That's a purely mechanical question.
Thanks for the response. My failure question concerns whether my 12-volt motor will hold up with a 36-volt battery applied. The only way I can explain acceleration in a graph form is for you to look up a device called Dragy that Hot Roders use to tune their cars.
We don't have any firsthand familiarly with them so for that reason can't really have an opinion. Most direct drive hub motors have roughly similar performance metrics.
@@GrinTechnologies It's this: www.neodrives.com/en/drive-system/z20/z20-rear-motor/ The problem with my 250W direct drive motor on my handcycle is that it overheats and turns off after I go over 50 kmh for a prolonged period of time. I can cook my motor like this eventually?
Yes you can find jackshafts on ebikes. However given the simplicity and low cost of hub motors it might be better to with around the limitations of a hub motor rather than adapt with a jackshaft.
The ferrofluid oil adds about 6-8 grams ( 1/4 oz) of weight and causes zero extra drag: ebikes.ca/product-info/grin-products/statorade.html Conventional oil cooling like ATF needs more like 60 grams (2 oz). The weight is not something anyone would notice.
You don't sell an ebike with a 250 watt power limit. Bosch bikes do about 800 watts of power. That's what you need to get usable hill climbing oomph. Regulations generally refer to "rated motor power" or some such, I've not heard of any that stipulate the actual electrical input power to be limited. If you limit the output power, then 250 watts is exactly the same thing regardless of whether it is coming from a DD hub motor, a geared hub motor, or a middrive motor. 250 watts simply means the wheel torque in Nm scales with your wheel speed by the equation: Nm Torque = 250 *2*Pi / rpm.
@@GrinTechnologies Thank you very much for your answer. I'm looking into this because of velomobile I'm building. Mechanical transmission is full of compromises... And I have seen the serial hybrid pedal-electric pedelec called Frikar. They use two motors... one is driven solely by battery, other is driven solely by pedal electric generator. They are suggesting to circumvent the European road traffic act by this... and it looks plausible. But when I tried to apply these limitations and set them to your engine simulator, then when I turned current high enough to overcome hills(there are hills up to about 12% here around), it leads to motor burn out in short time... It looks like I would need to have at least 750W engine(internally geared) to be able to overload it over 1500W at which I would have torque high enough... and motor would last at such torque at least 5-7 minutes. Well then there is an compromise- to have both mechanical and electric drive. But the complexity of system goes up, and serial hybrid pedal-electric transmission is no longer good option. And yes, I know that pedal electric transmission would have up to 80% efficiency at best(unless expensive solutions would be used).
