In early 2014, a few E-bike hot-rodders took a risk and bought a very large hubmotor direct from a Chinese company called MXUS, and the results were so good, this large hubmotor is now growing in popularity.
For many years, the MXUS company has manufactured hubmotors for other companies to put their names on the sideplates, but…a couple of years ago, they began selling them under their own name. I mention this because the “MXUS” name may be new to some E-bike builders, but…they are not new to hubmotors.
I first heard about the MXUS company a few years ago, when a popular E-bike kit company called em3ev.com began carrying a MXUS-branded direct drive hubmotor (with a 28mm wide stator and 7 gears). The customers seemed to be happy with them, but the motor that really got E-bike builders talking about MXUS, is when they began selling a model they called their 3000W hubmotor.
MXUS is located in Chang Zhou (just west of Shanghai), and they have been a long-time manufacturer of hubmotors for several branded retail companies that make electric bikes. Apparently, a few years ago they decided to also begin selling their products directly to the public under their own name.
Their large 3000W model has a spoke-hole flange diameter of 231mm / 9.1 inches (called the spoke Pitch Circle Diameter / PCD). This size has evolved to be a very popular direct drive hubmotor diameter for many companies, because…if you were to make a hubmotor larger in diameter, it would require either cast spokes, or a radial lacing of conventional spokes. Hubmotors that have a larger diameter than this have been tried by several manufacturers, and even though the larger diameter increases the leverage of the magnets acting on the wheel (which produces more torque per the same watts), very few customers have wanted cast spokes (between the motor and wheel rim) or a radial lacing pattern.
If a company decides to settle on making hubmotors of a specific diameter, they can manufacture several models that all use the same side-plates and stator laminations. They can then vary the models by making the stator wider to allow more amps, or…narrower to keep the weight lighter and the cost lower (plus a narrower motor allows more gear-sprockets to be mounted).
Let’s get to it!…whats inside?
Due to how wide the stator is, there is only enough room to add a single-speed freewheel. However, this wide stator creates a very wide set of electro-magnets to provide a LOT of power potential. The larger copper mass also allows this hubmotor to use a massive amount of amps without overheating.
Why the V2?
The picture below shows two almost identical stators from Crystalyte hubmotors. They are the same diameter and width, but the H4080 on the left has an old-style (less expensive) thin steel-plate stator support, while “The Crown” on the right has the thick aluminum spokes and aluminum base under the lamination-stack.
The pic is from our friend Jay (ES member “Hyena”), who has been racing electric hub-motored E-bikes for fun in S. E. Australia (at Hyena Electric Bikes). The brutal acceleration and high amps he uses on every turn of the track got the H4080 hubmotor too hot, and it was hot enough that the clear epoxy insulation on the copper wires of the coils broke down and shorted the motor (notice the dark discoloration). He upgraded to “The Crown/TC” with the aluminum stator support, and the motor no longer overheats at his power levels.
The near-identical Crown motor has a significant amount of added weight in aluminum used in the stator support spokes, and the aluminum rim just underneath the steel lamination-stack that forms the electro-magnets of the stator. This mass of aluminum in that location acts as a “heat sponge” to soak up temporary amp-spikes, and to then dissipate them over time.
There are many factors affecting how many peak amps you can use, and how frequently and how long you can use them. The main point of the aluminum in the stators central support is that…you can use more amps, and use them longer than the original 1st version (V1). The second version (V2) also has thinner laminations to make the motor more efficient (0.35mm vs 0.50mm), so less heat is produced in the first place, and…of course, the V2 also has the desirable “hot rod” aluminum stator center.
In the pic above, you can see the type of damage that can easily happen to the motor cables when an E-bike falls over. The old common method of having the motor cable exit the motor through a hollow axle-tip makes it more vulnerable in accidents. Not to mention that axles that are as hollow as shown here are somewhat weaker.
The trend for off-road E-bikes is to move the motor out of the rear wheel and onto the frame, to make the bike more nimble when crawling over obstacles and taking big jumps. However, hot rod street E-bikes don’t seem to mind the rear hub weight as much, and fat heavy hubs that can take massive amps for brutal acceleration have remained popular.
A problem from the past was that…if an E-bike with a heavy rear hub ever hit a pothole or landed a big jump, the axle might bend. Because of this, all the popular big rear hubs have gradually beefed up their axles. Damage to spokes and axles can also be eased if you use a full-suspension frame, rather than a hard-tail (an of course, fatter tires rather than skinny tires).
The MXUS 3000W V2 axle still uses 10mm wide flats, so it can fit in common bicycle drop-outs, but the other dimension is much thicker. This axle uses a M14 X 1.5mm nut, the same size as an automotive lugnut.
The three hall sensors allow the throttle to exert a very subtle control over the (three phase) motor at low speeds, when using a sensored controller. This motor can (of course) still be used with a sensorless controller if you want (sensorless controller is recommended for the more heat-sensitive V1). The extra wire seen on the left is a temperature sensor, which all hubmotors should eventually have from the factory. You don’t have to use it, but it is there if you ever want it.
The pic above shows the MXUS on the swingarm of a Qulbix Raptor 140, with the beefy clamping torque-arm integrated into the drop-out. If your bike frame has the common 135mm drop-out width, it is not recommended to try and squeeze-in any more gears there than a single-speed. If you have a steel swingarm, it is safe to spread it out a few millimeters, and you could install a White Industries “Dos” 2-speed freewheel, but most builders seem to want to eliminate the derailleur.
The MXUS factory was shipping the V1 with 13ga motor phase wires, and wires that size could get pretty warm if you frequently used 72V X 40A = 2880. The stock 13ga wires would easily survive at that power level, but thicker wires are pretty cheap, especially if installed in China right from the factory. Some builders want to use a lot more amps, and also want to make sure that the wires are not the amp-heat limit.
In the picture above, endless-sphere member madin88 (from Austria) used very flexible high strand-count copper wire with a thin and tough high-temp teflon insulation, and was able to squeeze-in thicker 11ga phase wires (12ga would be easier, but thinner), and..he had to use a black zip-tie (the red arrow) to keep the cable from getting rubbed by the part of the side-plate that spins, and he also added a fat washer with a channel filed into it (the blue arrow above, and also shown in the pic below) to help the bend in the cable. The stock 13ga wires are fine at the rated 3000W, but…some builders want to use 72V X 100 amps! (7200W)
Enough customers have expressed concern about the wire size and the fitment issues involved in upgrading to 11ga, the factory announced recently that they will incorporate several of these design changes in the V3 coming in the spring of 2016.
Torque arms are important for any hubmotor (even low-powered ones), but not for mid drives. However…high-powered hubmotors need extra-strong TA’s, and a useful feature is for them to clamp down on the axle. The clamping feature is especially important if you are using regenerative braking (“Regen”), which exerts a tremendous reverse rotational force onto the axle.
In the pic above, there is an example of a water-jetted steel torque-arm. It does not have the clamping feature, but I am seeing more examples of these that have been re-designed to add that feature. There are so many minor variations in bicycle frames, that it is impossible to to make one single design that works well for every ebike, but…they are vital, and worth the effort to find one that works for your particular frame.
I only know of two other hubmotors that are in the same power class as the MXUS 3000W, and that would be the Monster Cromotor from Zelena Vozila in Croatia (Europe), and also “The Crown” from Crystalyte, retailed through ebikes.ca in western Canada.
The MXUS 3000W V2 (catalog# XF40-45H) is currently available in four different windings. They all have the same amount of airspace around the stator teeth for copper wire, so you can use either many turns of thinner wire, or fewer turns of thicker wire. Although these have been run at voltages from 50V up to 120V, they are designed to perform well at around 72V. If the voltage stays the same, the low turn-count windings are faster, and the higher turn-count windings are slower (but typically use fewer amps to achieve their top speed). The turn-count versions are commonly referred to as 3T, 4T, 5T, and 6T.
The Kv of a motor is commonly used as an approximation of how many RPM’s a motor provides per each volt that is applied. For example, Kinaye Motorsports recommends the 5T motor mounted in a 17-inch moped rim and tire, using 72V. The 5T Kv of 7.1 means that 7.1-Kv X 72V = 511-RPMs when unloaded (tire spinning in the air). A 17-inch (I.D.) Moped tire has an outside diameter of 21.5-inches. Knock off about 15% of the RPMs when fully loaded with a rider and the added wind resistance at top speed, and such a combination would likely have a top-speed near 33-MPH (53 km/h)
If you wanted a higher top-speed than that, there are several options. You can specify a higher Kv (lower “T” number, like the 4T or 3T), you can use a higher voltage, or you can mount it to a larger diameter wheel. The 30-MPH top speed in the above example may not sound very fast, but this particular combination can provide brutal acceleration, and do it frequently without overheating, all the while using affordable DOT rated tires.
If this section of this article is the type of information you like, read our motor tech article, here)
Phase resistance = 0.072 Ohms
RPM at 50V = 597, 11.9 Kv
1.78A/89.4 Watts, No Load
Phase resistance = 0.110 Ohms
RPM at 50V = 448, 8.9 Kv
1.08A/54.2 Watts, No Load
Phase resistance = 0.163 Ohms
RPM at 50V = 359, 7.1 Kv
0.84A/42.2 Watts, No Load
Phase resistance = 0.225 Ohms
RPM at 50V = 299, 6.0 Kv
0.64A/32.1 Watts, No Load
All bare hub motors (no spokes or rim) weigh in at right around 9.14 Kg / 20.2-lbs
I also want to make sure to note that Kinaye Motorsports has special-ordered a group of these MXUS motors with an extra-wide axle to fit the 170mm width of fatbike rear drop-outs. Fatbike front drop-outs (on the fork) are commonly spaced at 135mm, so a normal rear hubmotor would usually fit onto a fat fork.
Moped rims and tires, a new trend
Here’s our article on this new trend, but just know this: If you are going to put up with the extra weight of one of these fat hot-rod hubmotors, and also give up the possibility of having the 7 gears you could get with a narrower hub, you will want to get your moneys worth…by feeding this beast a lot of volts and amps.
And…if you do that…I simply can’t recommend bicycle rims and tires (at least, on the rear), now that affordable and available moped tires and rims have been tried and proven to work well with the short spokes and the severe spoke angles that result from a large diameter hub in a smaller diameter rim.
Kinaye Motorsports is leading the way by having the option to order this fat hub already laced to a 17-inch or 19-inch moped rim, using thick 10ga spokes (common E-bike spokes are 14ga). The 17-inch moped tires and rims result in a wheel that is similar to a 20-inch bicycle wheel, but with a fatter and more robust rim and tire (17-inch X 2.25 moped tire = 21.5-inches OD). The 19-inch moped set is similar to a 24-inch bicycle set (O.D. of 23.5-inch).
Where to get one?
A man named Valentin (from the Russian retail web-store e4bike.ru) was the person who convinced MXUS to develop a wider stator from their existing model motor parts, and later he also was the person who convinced them to offer the upgraded V2.
endless-sphere member Allex (from Sweden) brought the V2 to the attention of the E-bike forums. Of course you can still buy a motor direct from MXUS, but make sure to specify that you want the V2, with the thinner .035mm laminations and the aluminum alloy stator-core, plus…ask for the factory-installed temperature sensor, and also ask for the fattest phase wires they can fit.
Valentin (ES member name “e4bike.ru”) from the web-store e4bike.ru is a retailer based in Russia. They will ship to anywhere in the world, but NOT the USA and Australia (due to regional distributor agreements listed below)
Sam Dekok (ES member SamD) from Ballarat E-bikes is the distributor for Australia
Allex is an ES member based in Sweden (for buyers in the European Union, who prefer to avoid ordering from MXUS or Russia), and you can contact him through endless-sphere.com, since he does not have a business website yet.
Barent Hoffman (ES member teslanv) from Kinaye Motorsports is located in Washington (N.W. USA), and he is the distributor for North America.
Here’s a quote from Barent:
“…My 60-MPH Run was done with a Lyen (Xie Chang) controller. 18FET IRFB4110. 80A Battery & 180A Phase on 100V of 6S 16AH Multistar LiPos, in 1P. Controller was programmed for “Speed”, set to 120%…I have to note, however, that running these motors at this high of battery & phase current is not enjoyable at anything other than straight ahead, and WOT [Wide Open Throttle]. Trying to ride around town with these settings is brutal. For fun cruising, I much prefer 50A Battery & 100A Phase for a very fast but more gentle ride…”
Written by Ron/spinningmagnets, May 2015