Why Does one DD hub Motor cog so much more than others??!?!!

[LI-ghtcycle]

Hello!

I'm really curious why this is, if I understand correctly, the cogging that is felt while riding a DD E-Bke, is caused by permanent magnets inside that are generating resistance because the magnets' are N to S polarity and magnetic attraction is making the stationary side and the spinning side try and hold the wheel still while not under power.

Now, what would be different with one DD vs another that would make one have significantly more cogging than another?

I have tried a few different DD's out there, and I have not tried a X-light 530X monster hub motor, or one of the other DD motors I hear people talk about with such terrible cogging that they are practically impossible to ride when not under motor power.

I have used Aotema and 9C DD's the most, but I have casually demo'd in a parking lot a few others, and I haven't ever experienced this excessive cogging, and granted I pedal a lot, so I'm not as adverse to pedaling, but since I have been riding almost exclusively un-powered pedal bikes for the last month to 2 months, you would also think I would be extra sensitive to when I WOULD have a DD motor cogging.

The only time I have ever experienced this is when I am assembling a kit and try to rotate a hub motor and the leads from the motor are loose and touching each other, so I wonder if this means it's a controller issue more than the type of magnets used?

The other reason I ask, is because earlier generations of DD hub motors seem to have lighter gauge windings, less weight, and I'm wondering if they might also have less cogging, I don't really know because I haven't been able to do any long term testing on a newer generation of say a 9 X 7 9C motor but I'd like to know what you all have experienced.

Thanks!

 

[John in CR]

It's not the controller. When the phase leads touch making the wheel hard to turn, that is like regen braking or plug braking.

The stator slots on the Xlyte motors are angled, not straight across, and I understand that reduces cogging to some extent. My motors are from small emoto's with no pedals, so cogging wasn't a design issue and they cog pretty good. There was some discussion about cogging in the e-bike technical section, but most of that was over my 2 cent electronics pay grade.

John

 

[dogman dan]

I have an x5 that cogs like mad. I thought it was just the big heavy magnets compared with an aotema. Though it sould have had some more cogging due to the wider magnets, I realize now that it may have also had a tiny short in the used motor that made it cog a lot more.

 

[neptronix]

Golden motors DD hubs seem to cog like crazy. I rode on two different ones that were larger in size ( one of them had a swirl pattern to it ).

Rode a bionx 250watt kit.... no cogging whatsoever. hm.

 

[chroot]

bionx has 250 watt and weak motor hub. The 9c and X5300 series both are madly cog pretty much cause they have
powerful magnet than bionx motor hub.

I have 2nd ebike izip with bafang geared hub motor 250 watt and doesn't feel any cog at all.

 

[LI-ghtcycle]

Hmmm, now this REALLY has me thinking ... I wish I had someone local that I could visit and test ride their 9C motor from a company other than Amped Bikes and see if that is the difference, or if I am right and it's more of a controller issue, than maybe that is the real answer.

Maybe some controllers do things differently and cause cogging to be much worse, because I'm very serious, I'm exaggerating at all, this "9C" 9 X 7 wound motor has NO cogging at all.

I actually rode this bike, hauling a trailer of 100lbs of tools and supplies for the bike camp I am volunteering for, and NEVER used the motor except a couple brief spurts to demo it to people, and the bike is 75lbs, and it wasn't hard to do!

I really think that in the past when I had it on my father's first bike, it was not the motor cogging, but a brake dragging or just the crap bearings in the wheels and/or cranks that made us feel like it was cogging.

 

[Gregory]

I have 2nd ebike izip with bafang geared hub motor 250 watt and doesn't feel any cog at all.

Thats because the bafang has a freewheel built into it so it isn't turning the windings - it should spin relatively free.

my x5305 isn't too bad, but then I don't expect it to be perfectly smooth.

 

[dogman dan]

Justin once wrote that there was some variation in the cogging of clyte motors.

For sure, if a planetary gear motor cogs, it's because the freewheel is locked.

Of my other motors, Aotema brushed hubs had lots of cogging, They also had a small number of big magnets. Aotema brushless motors cogged less, and have about twice as many of smaller magnets.

My aotema motor seemed to have very little cogging, but I could feel it. About the same with all three of my 9c motors. It's there, but not very noticable. What's noticable if I ride without power is mainly the extra 30 pounds of hub and battery. Not the cogging per se.

Motors that cog a lot are said to cog less if you unplug the phase wires, so maybe there is some kind of effect from the controller. But with controllers I have had, Aotema, and ebikekit, I never could feel any difference.