Leafbike has been producing a direct drive hubmotor that has earned a spot of respect with electrical bike lovers, and I made a decision it’s time to elucidate why it retains beating the competitors on this measurement vary. So, lets have a look…
The factor that makes this mannequin particular is the extra-thin 0.35mm laminations within the stator-core, and I’ll get to that in only a bit. However first…I’d like to speak somewhat concerning the recognition of direct drive hubmotors on this measurement vary. Essentially the most reasonably priced ebike kits are the so-called 1000W direct drive hubmotors. They sometimes have a stator utilizing the frequent 205mm diameter laminations, after which then hubmotor producers stack them to make the motor wider if you would like extra energy. There are frequent hubmotors marketed as 1000W, 1500W, and 3000W which all share the identical laminations. This commonality of components makes these laminations extra reasonably priced as a consequence of mass manufacturing.
As soon as the width of the lamination stack is assembled, the producer wraps copper wires round every lamination stack “tooth” to make the electromagnets which are turned on and off to spin the motor. The recognition of the 1500W measurement is as a result of reality it’s the widest hubmotor that also permits a standard bike body with 135mm vast dropouts to make use of a standard and reasonably priced 7-speed freewheel.
This additionally signifies that the 1500W measurement appears to be like nearly equivalent to the frequent 1000W measurement externally. The actually fats monster QS 205/50H solely leaves sufficient room for a single-speed sprocket, which makes it’s highly effective width much more conspicuous.
Years in the past, when somebody who was new to ebikes purchased an affordable 1,000W direct drive (DD) hubmotor, they typically fell in love with it, however…they wished extra energy. Merely including a extra highly effective controller and battery normally ended up with a fried motor. So…they went again to the web and acquired a bigger Crystalyte H35. The “35” within the title is as a result of the rotor magnets have a “Top” of 35mm, and consequently, the matching lamination stack can be 35mm vast. The 1000W hubmotors sometimes solely had a 28mm vast stator.
These 35mm vast stator-motors carried out simply nice while you restricted them to the nominal 1500W, however…their efficiency was excellent in the event you doubled that for just a few seconds for a burst of acceleration utilizing 3,000W.
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Skinny Laminations
The actual magic is within the skinny laminations. It sounds odd {that a} barely thinner lamination may have a giant impact, nevertheless it does. What’s even stranger is that it prices lower than $10 per motor to modify from the frequent 0.50mm laminations to the thinner 0.35mm ones, and but…they don’t seem to be as frequent as you may think.
This impacts a phenomenon known as “eddy currents”. When a magnet passes over a ferrous materials (just like the iron within the metal laminations), among the electrons within the iron molecules are pulled and shoved round by the magnetic discipline of the magnets. After the electromagnets are tuned off and the everlasting magnets have handed over, these unfastened electrons return to any close by imbalanced iron molecules. The longer a distance that they journey backwards and forwards, the extra warmth they generate. Utilizing thinner laminations limits how far the eddy currents can journey.
Due to this, the Leafbike hubmotors are listed as having a 90.5% effectivity, which is healthier than common. Years in the past, I although just a few extra share factors of effectivity meant {that a} given motor would possibly present somewhat extra vary from the identical battery, so…I didn’t actually care about that. Then, I came upon that these few share factors of effectivity meant that the much less environment friendly motor was changing extra battery watts into waste-heat. In consequence, fewer of your battery watts had been transformed into work. The Leafbike 1500W hubmotor with the ability to take excessive energy whereas producing much less waste-heat is the place the magic is.
So, how a lot energy can the Leafbike 1500W actually take? Electrical bike kits from China are incessantly discovered to have wildly inaccurate energy rankings. Some are down-rated to make a robust element appear authorized, and others are over-rated to impress consumers with how highly effective they’re. Based mostly on a number of years of ebike hot-rodders utilizing this hubmotor, I can confidently say that 50V X 30A is it’s fixed score, that means that…in the event you load it down sufficient to repeatedly draw 1500W, it won’t fritter away.
If you happen to’ve learn lots of the articles we’ve written prior to now, you’ll know {that a} hubmotor’s non permanent peak score is normally twice the continual energy degree. This implies I’m score this motor as being able to 3,000W for fairly a little bit of time earlier than it’s important to let off the facility and let it quiet down some. That’s fairly nuts for a hubmotor that’s not very massive or heavy. It will get even crazier in the event you learn the subsequent part beneath on warmth shedding mods…
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Getting Rid of the Warmth
Someplace round 3,000W @ 60A, this motor reaches saturation. Because of this in the event you add extra amps above that, you’ll get somewhat extra energy, however no the place as a lot as when you’re utilizing a decrease energy degree. The quantity of copper mass in a 35mm vast stator can take 30A all day, however someplace round 60A the warmth actually begins to extend quite a bit per further amp. If you happen to sometimes hit this motor with 60A, you won’t need to do this for very lengthy. It’ll drain your battery quick, and it’ll “warmth soak” the stator windings, since you are additionally exceeding this motors means to shed warmth.
A couple of years in the past there have been numerous experiments about tips on how to assist these hubmotors shed extra warmth. The simplest and apparent technique was to chop massive holes within the side-plates. If you happen to added a temp sensor to the stator (extremely really useful for all hot-rodded hubmotors), That may inform you while you had been approaching a hazard zone the place the warmth would possibly harm the stator. This type of modification allowed you to make use of 60A extra incessantly, and for longer quantities of time for every time that you just hit it.
Nevertheless, slicing massive holes within the side-plates permits filth to get into the within of the motor, which might harm the axle bearings, amongst different issues. Doing this nonetheless works for a short-term race, nevertheless it’s not an answer I like to recommend for long-term commuting. If you wish to preserve the hubmotor shell sealed-up, the remaining choices are…including ATF, upgrading to a solid aluminum stator core, or including ferro-fluid (FF).
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ATF, Solid Aluminum Core, or Ferro-Fluid?
Though the sideplates of a DD hubmotor are aluminum (which is understood to soak up and shed warmth effectively), there may be an air-gap between the recent electromagnets within the stationary stator and the spinning permanent-magnet rotor. If you happen to add a couple of small coffee-cups price of artificial Computerized Transmission Fluid (ATF) to the within of the hubmotor, this fluid spreads out as quickly because the motor begins spinning, and it fills that air-gap. This supplies a path to hurry up the warmth within the stator reaching the aluminum side-plates, so the warmth might be shed to the surface air.
That is good for high-amp efficiency, nevertheless it comes at a worth. Irrespective of how effectively you attempt to seal up the side-plates, the ATF will sometimes leak out and drip, or worse will probably be flung onto the rear brakes. Testing has even verified that when the core of the motor is heating up and cooling off it causes the motor to “breathe” by means of tiny air-gaps within the copper wire strands within the motor section wires, so…you should additionally add a small vent to a side-plate to forestall strain variations. Including ATF is just like the ventilation-holes we talked about earlier than…good for a race, however not price it for a long-term street-fighter.
And this brings us to the choice of utilizing a solid aluminum stator core as an alternative of a skinny metal stamped plate. After all the cores of the person stator electromagnets are nonetheless stacks of this laminated metal sheets, however between the axle and the electromagnets there must be some help construction. I purchased a hubmotor as soon as with a solid aluminum core, and it labored as marketed. The thick aluminum mass absorbed heat-spikes from non permanent excessive amps, after which shed that warmth over time after I was cruising alongside at my prime velocity. Exhausting acceleration attracts excessive amps, however sustaining velocity really attracts only a few amps by comparability.
So, why isn’t that what I’m recommending? It really works and there’s nothing flawed with it. The solid aluminum core was first seen on the massive bike hubmotors, just like the QS 205/50H. Because of in style demand, even the mid-sized hubmotors have had this feature added to their catalog. The MXUS 3000W might be bought both method, with a core of stamped metal or solid aluminum. The underside line is that the solid aluminum stator core is dearer, and heavier.
When an electrical bike is utilizing 8,000W or extra, just a few additional kilos or kilos of weight within the motor isn’t that noticeable, however…the Leafbike 1500W actually shines when its utilized in a reasonably mild downhill bicycle body as a consequence of its affordable weight, and distinctive energy.
And this brings us to the ultimate possibility, which is the one I like to recommend. Including Ferro-Fluid (FF) means that you’ve got dramatically improved this motors heat-shedding means, and which means you need to use 3,000W or 60A very incessantly, and for surprisingly lengthy stretches.
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Ferro-Fluid and the Leafbike hubmotor
FF was developed to assist the magnets in high-performance music audio system to shed warmth, which allowed smaller audio system to be pushed to a louder sound degree. It doesn’t run out by means of tiny gaps in hubmotors as a result of it sticks to magnets, just like the everlasting magnets within the rotor of an ebike hubmotor.
We wrote about FF in 2017 (to see that article, click here), and after a number of years of hot-rodders utilizing it, no downsides have been found. These things works. It was so in style, we additionally wrote an set up information in 2018 (to see that article, click here). Utilizing FF means you’ll be able to have the lighter model of a hubmotor, whereas nonetheless having the excessive peak energy potential.
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Why not 72V?
Operating the Leafbike motor at 72V might be executed (20 cells in Sequence / 20S), and that does present extra energy with no further warmth. Nevertheless I’m a giant fan of 48V or 52V for ebikes. It is a a lot safer voltage vary to work with, the batteries are cheaper, and there’s a higher collection of batteries.
On a side-note, in the event you ever have an influence outage, the inverters which are labeled as 48V-input will settle for each 13S and 14S battery packs for the enter (48V and 52V). Because of this these massive electrical bike batteries can energy an inverter to supply 120V AC in an emergency.
If you happen to learn our article on understanding motor phrases (to read that article, click here), this measurement of motor can have the choice of a number of totally different windings, known as a motors “Kv”. This impacts what number of RPM’s you’ll get per volt that you just apply to the motor.
Since all these totally different Kv choices use the identical stators, all of them have the identical quantity of airspace round every stator-tooth. Because of this the coils might be produced from many wraps of thinner wire, or fewer wraps of thicker wire. Because the sooner Kv motors (decrease turn-count) use fatter wire, they’ve much less resistance, even in the event you solely use half of their larger velocity potential. Listed beneath are the turn-counts accessible from Leafbike. I like to recommend the 4-Flip, even in the event you don’t really journey at that prime of a top-speed. The highest road-speeds listed beneath are for a 26-inch wheel and a 2-inch tire.
4T / 13.1 Kv = 631rpm @ 48V = 39mph
5T /10.1 Kv = 485rpm @ 48V = 30mph
6T / 7.0 Kv = 336rpm @ 48V = 21mph
Leafbike calls the 4T mannequin their “45 MPH” Kv winding, however that velocity is with the motor unloaded and spinning within the air.
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A Cargobike Proposal
I sometimes get requested what about what kind of system is essentially the most dependable. My favourite ebike is a mid-drive, however I’ve to confess that the simplicity of a DD hubmotor is difficult to beat. And yet one more method that you could possibly make it climb hills higher with much less warmth is to lace it to a smaller rim, like a powerful 20-inch BMX rim. This lowers the top-speed, and will increase the wheel torque, with out another modifications.
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What Controller?
In case you are a longtime hot-rodder, you don’t want any recommendation from me about controllers. Nevertheless, in case you are pretty new to the ebike sport, I’d undoubtedly suggest that you just follow the manufacturing unit controller and throttle in your first time round (also, get a spare throttle for troubleshooting, they are cheap). This ensures that the parts are all plug and play. A sine-wave controller would value barely extra, however would run almost silent. The reasonably priced inventory controllers use a “trapezoidal wave” which is usually known as a square-wave, and so they have a slight buzzing noise when accelerating.
I’ve discovered the Leafbike web site to be a bit awkward to navigate, however the usual controller for the Leafbike 1500W equipment is a 40A unit utilizing 12-FETs, however…they do inventory an 18-FET controller that’s rated for 55A. If you would like the bigger controller, seek for:
“48V / 52V 2000W fat snow bike motor controller“
Within the pic beneath, we will see the Leafbike makes use of the frequent measurement and form of lamination with 51 stator tooth. It’s 3-phase, so 17 electromagnets per section. The rotor has 46 neodymium permanent-magnets, so when programming a customized controller you’ll enter 23 “pole pairs” (they alternate the north and south dealing with the stator). A radial outrunner with three Corridor sensors so the controller is aware of the place of the rotor because it spins. A beefy thick axle.
The black plate within the heart is the skinny stamped-steel stator help. The section wires are a thick 3mm-squared in cross-section space. It really “appears to be like like” dozens of different hubmotor fashions, however this pic doesn’t present that the laminations are 0.35mm thick, as an alternative of the frequent thicker 0.50mm. That’s the place the effectivity and low warmth come from.
For a link to just the bare motor, click here.
For a link to the full Leafbike 1500W kit, click here
So far as the battery, in the event you don’t have a choice, I like to recommend the 52V Luna Cycles Wolf pack. If you happen to like this feature, specify the facility model that may put out 50A.
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Written by Ron/spinningmagnets, March 2022