New Mac Problems?

I just bought from EM3ev a Mac 8T w/cassette kit laced into a 20" wheel for my folding bike. I'd send these questions to them, but it is now the E-bikers (and RC'ers) favorite long-term holiday, Chinese New Year. So...

-I temporarily mounted it on the bike and plugged everything up and it all seems to work beautifully, except there is a faint squeal coming from the motor at very low RPM's, whether powered or just spinning it by hand without power, in either direction. It also doesn't freewheel very well. It almost seems like there may be a rubber seal in there somewhere that is rubbing against metal causing the squeal and resistance to freewheeling. Is this a problem, or is it just something that Macs do? None of the 4 other geared hub motors I've had experience with (3 Bafangs and an old brushed Heinzmann) have made a peep or had any resistance to freewheeling. This Mac spins up fine under power (without a load at least) and doesn't make any funny noises other than the squeal, but it doesn't seem right.
(Edit: Here's a video that I also posted later in the thread: https://youtu.be/WUXFtQd29mE )

-There is a threaded round spacer with 2 flats that is threaded onto the axle on the cassette side which sits mostly underneath the cassette body that was loose. I'm assuming that should be tight, right? It is ultimately the part that rests directly against the inside of the dropout. I tightened it up and it went in a few threads before seating, but still did stick out past the cassette body by a few mm which seems correct. That didn't affect the squeal at all so not related.

-Axle mounting width (OLD) with that spacer tight is still longer than 135mm... I don't have a tool that can measure that directly but I did measure my dropout width at 134.3mm with calipers and the dropouts have to spread at least a few extra mm to fit the motor (guessing 137-139mm). I thought this motor was supposed to fit 135mm dropouts? I feel like there should be washers between the axle shoulder/spacer and the dropouts but none will fit without spreading even a few mm beyond what they already are. Is this a problem?

-I thought the cassette was supposed to fit a 7 speed cluster, but there was an extra 4mm when I slipped on the Sunrace 11-34T 7 speed that I previously bought from Grin. It took a 4mm cassette spacer behind the cluster to allow the lock ring to tighten it up. This will work fine, but is this motor actually supposed to fit an 8 speed cassette or is this particular 7 speed narrower than the rest?

I can take pics and/or vid if needed but I'm hoping someone already knows of these things.
Any and all help will be greatly appreciated.

ALLVLTS said:

-Axle mounting width (OLD) with that spacer tight is still longer than 135mm... I don't have a tool that can measure that directly but I did measure my dropout width at 134.3mm with calipers and the dropouts have to spread at least a few extra mm to fit the motor (guessing 137-139mm)...

Click to expand...

I just measured the difference in axle width vs dropout width and it's an extra 3.7mm, so 134.3 + 3.7 = 138mm. I know a 3.7mm dropout spread isn't a big deal even for aluminum but it really seems like this axle should have washers between the shoulders and the dropouts, but if I used the 3mm tabbed washers that the motor comes with, that would need a 144mm dropout width!

Any thoughts on any of the above? I have been searching but haven't found anything about these particular questions.

I probably should have posted this in Technical but I can never tell because the two forums seem to be used interchangeably.

Well somehow I looked at the freewheel version on the drawing and skipped over the cassette version.
The freewheel version OLD is 135mm, but the cassette version is indeed 138mm. Still I feel that I need inside-the-dropout washers. The thinnest on McMaster are 2.3mm and if I used those the dropouts would need to be spread to 142.6mm. From the measured 134.3mm width of my bike, that would require an 8.3mm spread, or just over 4mm per side. I fear that this is too much for a 20" tire aluminum swingarm (it's a full-suspension folding bike). It's already quite the shove to get the 138mm axle in there. Hmm...

So after much measuring, pondering, and spec'ing hardware, I ordered from McMaster all the proper dimension SS nuts, washers, and round shims that I should need to allow everything to clear while adding inside washers on both sides and keeping the dropout width to <140mm. I do know that 140mm works because I actually used a Heinzmann brushed 500W motor with an OLD of 140mm on this bike for about 40 miles and it was fine. I feel that anything wider is really pushing it too far (I did want to go back to 135mm with the Mac but... oops).

So I'll call that problem licked (for now), but the other questions from my first post remain unanswered... Can anybody help???

Bueller? Bueller?
Anybody?

Would a mod kindly move this to E-Bike Technical?

I'll move it, and leave a ghost here, increasing its visibility.

Re the squeal, sometimes I have needed a spacer washer behind the freewheel, because it rubbed the motor cover. If that is the case it will be obvious when you try to spin the freewheel with it off the bike.

Does it do this both on and off the bike? The squeal and the drag?

Thanks!

The squeal isn't related to the cassette or the cassette freehub body, it does it independently from that. It squeals both with the motor mounted and without, in both directions. Same with the drag (although I'm obviously speaking of only the freewheeling direction for that one).

Just to reiterate/clarify: It's just a quiet/faint high-pitched squeal (nothing super alarming, just questionable), and it increases with RPM but goes away after some number of relatively low RPM (it probably gets above the audible range before it actually stops). The motor spins up to its full no-load RPM without a problem when everything is hooked up. There isn't a LOT of drag when it freewheels, but it's certainly not as free as the Bafang BPM, Bafang G060, and Heinzmann motors that I can compare it to. Those freewheel pretty much like a normal bicycle hub.

If the hub you received it semi disassembled, perhaps the cause of the problem could be from incorrect assembly (washer).
I opened a bafang, I had the wrong washer position when I assembled it, and did what he's doing to you.
I can't remember if the washer was inside the hub or at the freewheel.

After the Chinese New Year I'm buying the mac T8 20 rim, i hope that you solve your problem, so I'll be more relaxed.

I received the motor fully assembled. The only thing that was loose was that shoulder-nut thing that I mentioned, but it has no effect on the squealing.

Actually, let me try to upload a video to Youtube. A picture is worth a thousand words, a video is worth a thousand pictures, therefore a video is worth a million words.

Well that wasn't as hard as expected. I've never uploaded a video from my phone before. Cool. Maybe plenty of vids coming when I get Project Loose Cannon on the road. 8)

There are two irritating high-pitched noises in this video. Ignore one of them... That's my bird. :lol:

https://youtu.be/WUXFtQd29mE

Back to the dropout spacing (not to ignore the other). Here goes...

I got my hardware today. By replacing the 10.5mm thick shoulder-nut thing (which you can see in the video above poking out of the center of the cassette) with a regular thin nut that ended up being 5.7mm thick then adding both a 1mm and a 2mm shim (they're just extra thin, small O.D. washers), I get a 7.7mm stack which saves nearly 3mm. Then I added a 2.4mm thick full-size washer to that to rest against the inside of the dropout. That comes out to 10.1mm total which still allows the cassette/chain to easily clear the dropout/swingarm, yet gives me the inside washer. I could probably swap two of the .2mm shims in place of the 1mm with no ill effect, but I worry about their strength (I probably shouldn't... they'll just be sandwiched in compression between the 2mm shim and the full-size washer). So I can probably gain a little more still.

For the disk/cable side, I'm going to have to unshrink and de-pin the hall/temp sensor connector so I can swap the super-thick tabbed washer for another 2.4mm inside washer because it's all currently captive due to that connector (and the phase bullets). I'll just have to be sure to pin it back up the same way (and add more shrink).
That would also allow me to add a Grin torque arm to that side so I could have two (thinking better safe than sorry with an 8T on 40A in a cheap aluminum swingarm... I suspect this lightweight 20" folding bike will do epic wheelies).

So... with all that I can keep it just under 140mm, and fit two Grin torque arms as well. Should be okay that way, I hope. Any thoughts to the contrary?

Sounds like the gears to me. Maybe they put lube in there, but didn't properly apply it to the gear teeth. The sound is like a really old, hard run motor, where the lube got slung off the gears onto the motor shell.

Or it could be a gear defect, which will be apparent as the gears run higher speed, loudly, and then eventually wear in and run a bit quieter. I have seen that as well.

Been riding a MAC 12T for about 6 months now. That whirring noise is the motor spinning. The only time you might hear that once assembled is when pulling your bike backwards with no background noise. It's completely normal and nothing to worry about.

AHicks said:

Been riding a MAC 12T for about 6 months now. That whirring noise is the motor spinning. The only time you might hear that once assembled is when pulling your bike backwards with no background noise. It's completely normal and nothing to worry about.

Click to expand...

So yours makes the exact same noise?
How well does yours freewheel?

Yes, same exact noise when being pulled backward (which means the clutch is engaged). The only time I ever hear it is when there is no other noise around. Pushing the bike forward, there is no noise or noticable resistance

And it free wheels fine.

I am VERY happy with the MAC 12T. It's very quiet, and has plenty of power to handle any situation I've thrown at it. Noteworthy maybe, is the fact I'm 310 lbs and spend much of my time riding in a coastal area with plenty of fairly challenging hills. Hills challenging enough where this MAC replaced a 1500w direct drive rear hub that wasn't cutting it.

Put your bike together and go try it!

That sounds good.

The noise is actually slightly louder when mounted because somehow it gets amplified by the swingarm. :lol: It's not actually any worse though. It's noticeable both forward and backward, but slightly more forward. At any rate, if yours is similar and you've had no problems, I'm not going to worry about it. I just wanted confirmation that nothing is actually wrong.
Maybe the motor will loosen up and freewheel more freely after it gets some miles. It's not bad as is.
I just got a brand new Bafang 750W G060 to upgrade the factory 500W version in my fatbike and it spins dead silent in both directions and freewheels like no motor is there (just like the 500W it's about to replace). Obviously they're just a little different from the Mac.

AHicks said:

Put your bike together and go try it!

Click to expand...

Working on it! I just took a break to go test the new street tires on my fatbike. 18 miles went by quickly and silently and used less energy than ever. :thumb:
I've gotta figure out how to mount two torque arms onto Loose Cannon next. I think it's going to be a torquey little bastard with the EM3ev 3077 12-fet on 40A/52V.

I'll probably start a build thread before long now that I've got a name for it.

All said and done I got the axle OLD down to 134.8 by replacing the single 4mm cassette spacer with 2x cassette spacers at a total 3.5mm, then by replacing the stock 10.5mm shoulder-nut on the cassette side with a 5.7mm thick jam nut then 1.6mm total shims (to bring the surface *just* outside of the freehub body).

Then I added the 2.3mm full-size inside washers for a grand total of 139.4mm with those installed. I wish I had slightly thinner full-size inside washers but I haven't found any. (Edit: I just found full-size 1mm thick washers on Amazon. They'll be here on Saturday, so I'll be down to 136.8mm with inside washers. No problem whatsoever, then. )

Funny enough, the wheel was originally ever-so-slightly off center toward the disk side but now it's just about perfectly centered since I got rid of length only on the cassette side.