Many people on this forum will buy the cheapest parts they can find. This may be on ebay, or even known vendors who are on this forum.
Hub motors, being relatively new technology, is in high demand right now. They are simpler (less maintenance, which is almost none), can be just as efficient as belt drive setups (raptor 2 for example), and are stealthier (No belt and pulley system, and supports FOC better, since they run at a lower erpm, which means almost no noise).
There are cons to hubs also, such as the lack of gearing (which means for speed freaks like me, more wasted battery and heat, since we need higher kv hubs to reach the speeds we want) and less urethane on hub wheels.
For most people though, hubs have become a more appealing choice, especially for new builders. Theres one problem though: Almost all of the hub motors on the market today are simply too small.
The reasons are simple:
- Small motors have small stators. The stator can become over saturated by the magnetic field, and they suffer from what I like to call the nuclear effect. More on this in a second…
- Small motors have little copper in them. What this means is they heat up quicker.
- Small motors use thinner copper strands, because of space issues. What this means is for the same fill, you have more insulation. The insulation on a 24, 22, and 20 awg wire are all the same, and despite a 20 awg only having 40% more copper than a 24 awg, the 20 awg is rated at double the amps. The 18 awg is double the copper of a 24 awg wire, but is rated to 4 times the amps of the 24 awg. Why? Lower resistance and resistance is directly proportional to the amount of heat in the motor.
- Once over 130 F, your magnets strength drops quickly. Now you need more amps for the same power. More amps = more heat.
- Because of the combination of these three facts, the nuclear effect will drive the motor off the charts. This is why we see this difference in testings hummies hubs:
-old hubs: small stator, 15 turns of 24 awg, max temp of 260 F measured, will go higher if they didn’t almost catch fire at this point -new hubs: double stator length, 15 turns of 20 awg, max temp of 131 F.
Only 40% more copper and double the stator size, and we see all heat issues go away.
So what does this mean? Small motors are simply too small.
Now what do I mean by small hubs? I’m talking about jacobs hubs, maytechs hubs, koowheel hubs, and all of the direct from china hubs.
Now your asking yourself, why do so many people now make these inferior hubs? The answer is the same reason we have hover boards blowing up. Many manufacturers don’t care about the quality of their product, and the ones that show they do, don’t do adequate testing. For example, one manufacturer posted a video on youtube of their testing. Their test: 8 hours on a rack at full speed. The issue here, is that the current is very low without a load, fractions of an amp. With that low current, theres no way for the motors to get hot without a short in the motor. Compare that to the 20 amps you’ll pull with them to go up a hill.
There’s more to it than they don’t care also. The terrain, riders weight, riding speed, and riding style play a huge role in how many amps you’ll draw. On hummies small motors, I used to pull 4 amps on flat, and 10-15 on small hills. When you live in an area full of hills, you can see you’ll generate 3-4 times the heat than when in a flat area. This means 20-25% of the range you’d expect to get also.
Some riders do ok with these small hubs, as they weigh 130 lb or less, and ride at speeds under 10 mph, on flats.
However, if you plan to ride on hills, are more than 130 lb, and like to go over 10 mph, you’ll find these small hubs heat up quickly.
Some, like NVG, claim to have mastered the small motor, but why? Because they can do high heat, not because they have some magic way of cooling them. This is no solution, because once they got hot (which is quickly because of the little copper), you need more amps to get the same power from the copper. The magnets strength weakens, and now you need more amps to get the same magnetic field. And finally, the stator gets over saturated very quickly, which now means heat goes off the charts. Running a motor hot is not a solution to anything, because heat, creates more heat, which creates more heat. For programmers like me, this is the classic case of recursion with no base case. you end up with an exponential function of heat generation.
The solution? Simple… Bigger hubs. With hub motors, bigger, is simply better.
Now, why aren’t there more big hubs on the market?
- Those in china producing and seller straight from the manufacturer are trying to be first to the market. Even if that means they poorly engineer them, and do no real tests on them to see how they perform, only that they work on a bench.
- Bigger hubs need a custom truck. Why? Because the wheel base will be wider, you need to push them towards the center on the hanger more or your going to have a ridiculously wide wheel base.
- Designing a new truck, in addition to the longer or wider hub, takes time, and they don’t want to wait. They want to sell now. It also costs more, and looks less attractive to customers who don’t know any better about hubs.
Now what does this mean?
As builders who want to use hubs as this time, unless your a slow, light rider who rides short short distances on flat, you have 3 options for hub motors:
- R-Spec hubs (not sold separately, must buy raptor 2 complete)
- Hummies NEW double wide hub motors
- Carvon v3 or v4
If you feel like wasting your time and money, go ahead and buy small motors from vendors, on ebay, or straight from china, but I’m tired of seeing threads on here and get messaged by people who buy these small motors from china and are surprised that they failed. Now you know why they fail, so either you head this advice, or you risk wasting your time and money. The choice is yours…
