I don't like hub motors - (crappy ones)

[Drunkskunk]

I can only speak to failures I have had, or seen personaly, But most of mine have involved the bearings. most sieze, but some come apart. The bearings that come apart cause the magnets to impact the stator, and the motor turns to shrapnal. I've burned out a couple of windings as well. the windings are generaly only big enough to handle the max load, with nothing extra to add weight. My biggest shafts are 5mm. I have sheared one off, and twisted 2 others with a 500 watt motor.

 

[swbluto]

I have sheared one off, and twisted 2 others with a 500 watt motor.

Are these Hobby-city quality motors that you're referring to? I've heard and experienced the hobby city's motor's bearings' crappiness, and I'm planning on upgrading the bearings. Do you think upgrading the bearings may significantly extend the motor's expected longevity or are these types of motor just natural "bearings killers" ? Also, it seems over-heating the windings can be prevented with the proper protection. Now, onto the shafts - How did that happen? So, the motor is spinning a propeller and the shaft just twists - is that correctable or was the shaft replaceable? And sheared as in forces of spinning the propeller just causes a part of the shaft to rip right off? Did that cause any other significant damage to the motor? I think liveforphysics replaced his shaft with some kind of hardened treated steel, so I'm curious if that kind of problem would be better prevented (In the case it causes other significant other damage to the motor) or corrected when it crops up.

You don't know how appreciated your insight is! "An ounce of prevention is worth a pound of cure." or so Benny said, and prevention can be more readily justified for a 200 dollar crappy-city motor than a $10-20 one that can just be re-ordered if it's destroyed.

 

[JS Tyro]

A very good point is that the e Bike regulations are rather vague as to how power is measured.
I take it that 500watt in Ontario means 500 watt measured on a dyno at the wheel and not the gross output of the motor.
I also read the regulations to mean that 500 watt is average over a reasonably long interval, say 10km of actual terrain.
Therefore, there is plenty of room for the output, so measured, to lawfully exceed 500 watt measured at the wheel!
Or, for the output to lawfully exceed 500 watt at the motor measured as gross output and not net output at the tire.

My understanding of the regulations is that it depends on how the motor manufacturer rates the motor and the standard for rating the motors is what the manufacturer is going to stand behind for one hour of continuous operation. So a 500W motor is one that can consume 500W of power for one hour without going poof (most of the time).

In another thread, someone suggested that motor makers tend to be very conservative in rating their motors (industrial motors, not e-bike specific motors) (presumably to avoid warranty issues and lawsuits). That's in our favour, since it means we can get legal motors that may end up being 600W usefully while 500W rated (and peak can be higher still).

For e-bike, there is the example I read about where some maker took a 350W motor and stuck a 500W label on it, bumped up the voltage and sold it. QC? Whazzat?

Lots of bureaucrats would like to go back to nice, easily quantifiable measures like c.c. displacement!

I think that the power limit is just some number that the politicians decided sounded like a good limit. They buy their cars that way, after all. The fact that it has little to do with real-world performance is a minor problem... for them.

 

[JS Tyro]

There's a maximum acceleration limit?

If you look at one of the Ontario gov web pages, they describe the definitions and limits on various vehicles. For mopeds and scooters, there's a limit on how they accelerate. It's specified in terms of "cannot exceed x speed in y distance from a standing start" or something like that. I guess that's their way of saying "max 50cc engine" and avoiding the problem of someone borrowing some Grand Prix engine tricks to make it a hyper-compression turbo-supercharged gazzillion HP monster in a teensy displacement engine.

 

[johnrobholmes]

50cc engines can really pull a lot of power when made right and tuned up. Here in Mo they cap them at 3hp.

 

[Drunkskunk]

Are these Hobby-city quality motors that you're referring to? I've heard and experienced the hobby city's motor's bearings' crappiness, and I'm planning on upgrading the bearings. Do you think upgrading the bearings may significantly extend the motor's expected longevity or are these types of motor just natural "bearings killers"

Some better, some worse. 1/3 of the motors I've used are Eflite. A good, higher end motor with Japanese bearings, though I also have AXI, Hacker, ATX, GWS, and other brands so my experiance is from quality to dirt cheap. I think the reason the bearings go is again, the design. make the motor as light as possable, so use the smallest, lightest bearing possable. Since a duty cycle is 10-15 minutes for an RC motor, its fine. I don't think upgrading them will extend the life by much, but if you could adapt the motor to run larger bearings, that should help.

The shaft problems were with a 5mm shaft. the one that sheared looked like a bolt after over tightening it. it came off in the air after throttling up and sheared between the can and the prop. that was probably took only 20 pounds of force or less. The ones that twisted were run reverse, with the can on one end, and the prop on the other end of the shaft. One twisted entirly on it's axsis and I only noticed it when tearing down the motor to clean it. the other twisted the same way, but caused the motor to run unbalanced. the shafts are a hard steel, but not a high carbon hardened steel. I've used the shank of a hardened steel drillbit for replacement with good success, although its harder to clamp the can and the prop onto them

 

[GTA1]

50cc engines can really pull a lot of power when made right and tuned up. Here in Mo they cap them at 3hp.

How is the 3hp measured?

Gross at the crankshaft?

Net at the wheel on a dyno?

 

[johnrobholmes]

They are measured by if you are pulling a wheelie or going over 30mh :lol: There is no agency that enforces it, other than the police on patrol.

 

[GTA1]

Suppose we put on a mask and a cape.... and have the turbine jet exhaust give a nice glow with afterburners....

We can angle the thrust to take off and not bother with them?

 

[swbluto]

Just thought I'd refresh on some figures. I was doing some simulations with a 2806 hub motor on a 20 inch wheel, 300 lbs total weight on a 9% hill and the efficiency at speed was a whopping 79%! That's about as good as the geared motors are.

Direct drive hub motors still have other disadvantages, but it appears they don't necessarily suck with the right tire size and power output when it comes to efficiency when going up a hill. However, I don't know if 2806 9C's are available in a rear configuration, which is just about the only place I'd trust a high torque motor on a bike. And even then, there's a limit before rounding off the rear dropouts, so it's probably not quite suitable for a 30+ mph hill-climbing bike.

 

[swbluto]

Just thought I'd refresh on this.

I hate, at the very least, crystalyte 40x hub motors.

According to http://www.ebikes.ca/troubleshooting.shtml , my first c'lyte failure was #7: The hub flange broke at the joint of a spoke. However, it was made of 36 spokes, so I thought it should work just fine with 35 spokes and it has.

But then, today, while coasting down a 2% hill, I started pedaling in "gear 3 front" and "gear 4 back"(Of 8 ) and the thing wouldn't pedal. I heard a "clunk clunk clunk", looked back at my freewheel and saw it spinning independently from the motor. Oh no, sheared threaded collar or failure #8 according to the above link. According to ebikes.ca,

This usually happens when they are standing pedalling in the easiest gear, putting a maximum amount of torque on the freewheel.

I was neither standing nor in the easiest gear, so this tells me the thing fatigued to the point where anything would've killed it. I supposed after 2 years, something like this would've built up to the point of failure, and that it has.

So, now I have an ebike that I can't even pedal. C'lyte 40x motors really REALLY suck!

Maybe I'll try getting another cover from ebikes.ca, if they have any.

 

[Ypedal]

I have a box full of those covers if you ebikes.ca is out of them.. lmk if you need one ( i have the type with 8 bolt holes btw. ( some are 6 or so.. )

 

[swbluto]

Thanks for the offer, it seems like they had some in stock so I've ordered it from them.

I also ordered a 9C 2805 20" rim that I plan to power with 72 volts or so. According to the simulations, that should get me to 33 mph-ish up a 7% hill. Now I just need to figure the other parts out (Mainly controller and battery - Start over with lipo or just add more a123? It seems a123 will be cheaper, though I don't know if cheap a123 sources have evaporated. It seems like they have.)