MAC motor selection and MAC clutch issues.

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Bullfrog   100 W

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MAC motor selection and MAC clutch issues.

Post by Bullfrog » Jan 13 2020 6:26pm

Just passing along some of my personal experience, hope nobody needs it :lol: .

A couple years ago I purchased a 12T MAC and a 12FET/40A controller. At the time EM3ev advised me NOT to pair the two together because the torque produced by the 12T motor with the 40A controller would be hard on the MAC clutch. I blew them off, didn't listen, and did it anyway.

Now my clutch doesn't work...imagine that. It started out by not freewheeling and I was actually pleased because I was getting some regen. Then a couple weeks later, it started slipping under high torque conditions like starting from a stop and applying full throttle. It still works acceptably and will accelerate me and the bike but I can tell the bike does not accelerate like it once did.

A few solutions...
A. If you go with a 12FET/40A controller, use a 10T or 8T motor. They don't produce as much torque per amp and are a little easier on the clutch. That should help but won't fix the problem once it occurs.
B. Buy a GMAC motor from Grin Tech...it doesn't have a clutch and also has regen along with several additional improvements.
C. When your clutch starts having problems, drill through it and bolt it together or weld it together so it is a direct drive at all times....that is my plan once I get my motor apart :) .

Changing subjects a little bit and just passing along my opinion based on some research I have done on the MAC motor using the Grin Tech Motor Simulator. The below info is based on a total weight of 264 lbs bike and rider, it assumes you don't pedal at all, and please read the caveats at the very bottom:

If you are using a battery that is 52v or lower voltage battery...which I recommend with a MAC, the following motor winds would be my choice depending on how fast you want to go and how hilly it is where you ride:

10T with a 639 mm OD tire (Maxxis Hookworm 24x2.5)…steady state temp is 102C and speed is 25.9 mph.

12T with a 689 mm OD tire (Maxxis Hookworm 26x2.5) or a 686 mm OD tire Schwalbe Super Moto-X (26x2.4)...steady state temp is 102C and speed is 24.2 mph.

A conservative way to handle temps is to run a Cycle Analyst and program it so your power starts to roll back at 110C and shuts the motor down at 130C. Temps below 150C shouldn't do any damage to your motor...in theory.

Caveats:
A. Speeds are at 0% incline and with a 52v battery.
B. Temps were obtained using a 1.4% incline and matches the temps I got while riding.

My recommendation it to go with a BBSHD if you are going to ride off road at speeds below 20 mph and a Direct Drive motor might work better if you want faster speeds and/or don't have many hills.

Bullfrog   100 W

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Re: MAC motor selection and MAC clutch issues.

Post by Bullfrog » Jan 14 2020 11:06am

Update on the clutch issue...turns out the failure mode was the bearings in the planet gears and the clutch is fine. I was running a mixture of distilled water and Motul brand MoCool to keep my motor cool (about 4.5 ounces total). The water mixture probably washed the lubricant out of the bearings and contributed to their demise.

I previously tried cooling my MAC with 4.5 ounces of low viscosity automatic transmission fluid...and it worked great for cooling but a tiny amount leaked and got on my rear brake rotor which made the brakes useless...not good.

If you follow my guidelines above, you shouldn't need auxiliary cooling and can avoid the pitfalls I encountered from trying to liquid cool a MAC :D .

EDIT...

I should have kept my mouth shut until I had everything apart. I may have damaged the aluminum rivets that hold the bearings in the planetary gears during disassembly...turns out the bearings are fine and the looseness I felt was from the way the planet bearings are held in place.

The cause of the clutch malfunction was the little springs that push on the rollers inside the ramped roller clutch...I'll post pics and more explanation as soon as I can get everything together.

More EDITS and pics of the clutch internals...

I previously mentioned I was having some issues with my MAC clutch. During the disassembly of the motor/clutch, I believe I damaged the thin plates that retain the planet gear bearings and I incorrectly believed that the bearings had failed because they felt sloppy inside the planet gears. Turns out the bearings are fine and the problem is that two of the three springs inside the clutch that push on the rollers were deformed and most likely causing the erratic behavior of the clutch…sometimes it would not release and sometimes it would slip.
Below are pics of the internals of my MAC clutch. In the top picture, the springs fit in the slot that is in between the roller and the spring in the picture…and each roller has its own spring…I used the only “good” spring for the picture. The bottom picture shows the clutch plate flipped over, the rollers, and the three springs with obviously two of the three deformed/damaged.
I was running a 40A Infineon controller and I don’t want to hypothesize about whether or not the higher amperage contributed to the springs being deformed…my guess is that a MAC clutch has a limited lifespan and anything you do to abuse the clutch will shorten the lifespan.
MAC A.jpg
MAC A.jpg (41.56 KiB) Viewed 780 times
Attachments
MAC B.jpg
MAC B.jpg (31.93 KiB) Viewed 780 times
Last edited by Bullfrog on Jan 15 2020 7:15am, edited 2 times in total.

markz   100 GW

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Re: MAC motor selection and MAC clutch issues.

Post by markz » Jan 14 2020 4:38pm

That is the problem with installing coolant into the motor.
That FerroFluid might have been better if your loaded with extra cash.
If you have to cool the motor down, why not get a larger motor with more mass like the MXUS 3kw, or the QS equivalent and while your busy spending money drop some cash on FerroFluid.
Or just keep riding your MAC, but maybe buy some FerroFluid, or not.

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spinningmagnets   100 GW

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Re: MAC motor selection and MAC clutch issues.

Post by spinningmagnets » Jan 15 2020 10:21am

Thanks for posting this, bullfrog.

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wineboyrider   100 MW

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Re: MAC motor selection and MAC clutch issues.

Post by wineboyrider » Jan 15 2020 8:58pm

....
ES IS SAVED! THANK YOU JUSTIN.

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dogman dan   100 GW

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Re: MAC motor selection and MAC clutch issues.

Post by dogman dan » Jan 17 2020 6:01am

Interesting that the cooling fluid kept it from melting long enough to have mechanical damage.

I just keep wishing somebody would make a truly big geared motor. Not a 5000w one, but maybe one able to do 2000w, such as what you gave yours.

It would be bigger, heavier, with more copper and magnets so it would not struggle on the steeper hills and heavier loads. It would have better torque, because of more copper in the winding. The gearing would be lower, with larger planetary gears, so 26" wheel would not be such a handicap. You'd have the bigger magnets and more copper of a 500w DD motor, or more, plus the freewheeling.

The application would be pedicabs and large vending trikes.

qwerkus   1 kW

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Re: MAC motor selection and MAC clutch issues.

Post by qwerkus » Jan 17 2020 6:31am

dogman dan wrote:
Jan 17 2020 6:01am
Interesting that the cooling fluid kept it from melting long enough to have mechanical damage.

I just keep wishing somebody would make a truly big geared motor. Not a 5000w one, but maybe one able to do 2000w, such as what you gave yours.

It would be bigger, heavier, with more copper and magnets so it would not struggle on the steeper hills and heavier loads. It would have better torque, because of more copper in the winding. The gearing would be lower, with larger planetary gears, so 26" wheel would not be such a handicap. You'd have the bigger magnets and more copper of a 500w DD motor, or more, plus the freewheeling.

The application would be pedicabs and large vending trikes.
Amen to that. To bad all the money is getting poured into yet-another-hipster-middrive.
Thanks for sharing bullfrog; I read your thread about motor cooling. There were some concerns about using water. Turns out they were right :D Not sure ferrofluid would make a difference though on a geared hub. You'd need 2 layers: one in the motor and one between the motor cover and the outer casing.

BTW: mac also sells motors with locked clutched - not just the pricey gmac. I have a geared mxus with locked clutch. Still not tested though ...

Bullfrog   100 W

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Re: MAC motor selection and MAC clutch issues.

Post by Bullfrog » Jan 17 2020 8:23am

At this point I can't say if the water/Mocool mixture would cause a problem or not...I had it in my motor for about four months and I drain/changed it once. None of my issues were directly related to the cooling fluid BUT four months isn't long enough to make me feel comfortable recommending it. The only thing I saw was that the copper windings had a dull appearance as opposed to a shiny appearance...but everything worked fine. One option I considered but never carried out was to drill and tap a hole in the case and install a pipe plug so I could drain/change the cooling fluid. But draining/changing the fluid would be more labor intensive than I was willing to do. I really like the low viscosity ATF...IF I could keep it from leaking :D .

I apologize if I misled or confused anybody with my preliminary statement about the planet gear bearings...looking back, I think I distorted the thin metal plates that hold them in place when I was disassembling the motor by placing a piece of angle iron under the planet gears to support the clutch while I was hammering on things to get the clutch off of the shaft.

A little more info/data...

With 4.5 ounces of just about any cooling fluid, the MAC runs about 40 degrees C cooler than without it. The big challenges are leakage and not negatively affecting the motor with the fluid you choose. Much more than 4.5 ounces and you'll get more leakage because the static height will be above the brake rotor bolt holes, the axle seals, and the path where the wires go from the motor to the outside via the hole in the center of the axle. I replaced my clutch with another OEM unit just because I had an extra one. I am currently running a 24" Maxxis Hookworm rear tire (635mm OD) and a 13s battery...my bike with the 12T MAC has a top speed of about 22 mph on flat ground...measured via GPS.

Two things attract me to the MAC motor...

A. Lightweight...weighed my bike after getting everything back together and even with the steel frame from Walmart, my bike weighs 58 lbs.

B. The high torque output...I actually went through every single motor in the Grin Tech Motor Simulator and the 12T MAC puts out more torque per amp than any geared hub motor or direct drive hub motor except the Bafang G60. The G60 is even more fragile than the MAC as far as the amperage it can handle plus it only comes in a 170mm OLD so it isn't even an option for my bike: https://www.ebikes.ca/documents/MG60.pdf

qwerkus   1 kW

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Re: MAC motor selection and MAC clutch issues.

Post by qwerkus » Jan 17 2020 2:50pm

Yeah the extra high pole number combined with a slow wind (12T) are difficult to beat when it comes to torque. The problem to me is the price point. In europe, with all the extra sales going on, 750w bbs02v2 complete kits (no battery) are actually cheaper than a mac, especially now that pswpower & co are stocking them, so more more import taxes. No hassle to install and works very smoothly. Geared adequately, you can haul up any cargo uphill and still fly on flats. And you get IGHs! I'm not a super duper fan of mid drives, but you have to admit its an easy choice for most people looking for a quick conversion.

What I don't follow is why nearly all new ebikes developped as such come with mid drives. I mean if you have the freedom to design whatever frame you want, dd and geared hubs on small wheel are just awesome. 20x3" just rocks! I got this bike in summer, and the small hengtai geared hub it features nearly matches my bbs02! Next step is upgrading with a 9c 212...
I think a fast MAC would do wonders in such a bike.

markz   100 GW

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Re: MAC motor selection and MAC clutch issues.

Post by markz » Jan 17 2020 6:30pm

Yeah I noticed that too, about most of the store ebikes are mid motor, the hubs I do see in the stores are always 8Fun rears

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