MAC motor selection and MAC clutch issues.

[Bullfrog]

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]

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 .

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.

View attachment 1

 

[markz]

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.

 

[spinningmagnets]

Thanks for posting this, bullfrog.

 

[wineboyrider]

....

 

[dogman dan]

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]

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 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]

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 .

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]

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]

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

 

[Bullfrog]

Does anybody know where I can buy a 10T MAC Freewheel 135mm OLD Rear motor besides Alibaba?

EM3ev is no longer going to sell them and I can not get a response when I contact MAC directly.

I need the rear freewheel motor because I have four rims already lace to MAC freewheel hubs and I am constantly changing things around and doing all kinds of experiments :lol: . My 12T MAC is working great, I just want something with a little more speed. Tried an 8T but with a 26" or larger wheel, it ran too hot. I am using a hardtail steel frame and the I'd like to use a 26" or larger wheel because it rolls over bumps a little better.

Thanks

 

[amberwolf]

I need the rear freewheel motor because I have four rims already lace to MAC freewheel hubs and I am constantly changing things around and doing all kinds of experiments

The cassette version will operate the same way as long as you have the same sprocket sizes to match the gearing, and adjust the derailer when swapping between wheels if necessary to ensure it lines up for shifting.

So unless you have some specific reason I can't imagine, or one of the above is problematic, there's no reason to not get the cassette version if it's otherwise the right kind of MAC for your purpose.

 

[Bullfrog]

I need the rear freewheel motor because I have four rims already lace to MAC freewheel hubs and I am constantly changing things around and doing all kinds of experiments

The cassette version will operate the same way as long as you have the same sprocket sizes to match the gearing, and adjust the derailer when swapping between wheels if necessary to ensure it lines up for shifting.

So unless you have some specific reason I can't imagine, or one of the above is problematic, there's no reason to not get the cassette version if it's otherwise the right kind of MAC for your purpose.

"I have four rims already laced to MAC Freewheel hubs" and the Cassette hub will not interchange with he Freewheel hub. The axle in the Freewheel motor is 14mm and the Cassette motor has a 12mm axle.

 

[amberwolf]

Forgive me for not understanding the problem; I don't know your exact situation and may not have thought of all the ramifications. I'm just trying to see if there's a way you could use the MACs that *are* available to you.

These are the only issues I could think of that could prevent interchanging those:

--you have torque plate or arm hardware that cannot accept 14mm axle, only has 12mm holes.

--the bike dropouts/frame are insufficiently deep to allow for the extra millimeter of axle off-centeredness. A few things this might cause:

--dropouts not being deep enough to prevent axle spinout (though torque arm/plate would fix that and probably should be used anyway),

--disc brake caliper not being able to overlap the rotor as much (but it's only 1mm, so shouldn't make a significant difference especially on the rear brake),

--rim brakes having to be readjusted by 1mm axleward to make the same rim contact they would have with the 12mm axle, and/or not having sufficient adjustment range to reach.

 

[The Mighty Volt]

Hi I tried to post in the original thread for MAC Tear-Down but that was locked/disabled.

Despite my best efforts I managed to lose a few bits and pieces. It's a result of long periods between jobs.

Thanks for the Original TD thread-without it I'd never even have dared the repair.

Specifically I'd like to know- if anyone call tell me- what the specification is for the side-plate cover-bolts AND the spec for the bolts which hold down the internal aluminium cover plate that pins down/guides the phase/hall wires out and down the axle.

I reassembled mine last night and while it was an electrical success- the phases are wired correctly and the halls are undamaged- the motor runs- it's obvious that the loss of the little shim washer that sits on a clip atop of the metal drive sprocket is allowing the motor to slide over slightly and bring the retaining pins of ONE of the planetary gears into contact with the internal metal plate that separates the windings and the wiring from the clutch/geared side.

This is causing a sort of scraping as the gears rotate. It's obviously only one of them as the scratches on the plate are in exactly the same place.

Anyways it's a bit disappointing that such a relatively successful {and expensive} motor is held together by so very little on the inside.

Thanks for your time. :thumb:

 

[The Mighty Volt]

 

[Bullfrog]

Mighty Volt...will either one of the threads below help:

https://endless-sphere.com/forums/viewtopic.php?t=51310

https://endless-sphere.com/forums/viewtopic.php?t=54422

Or you can buy the 5T MAC I have for sale and take it apart :lol: .

If anybody else is interested in a 5T MAC new still in the box: https://endless-sphere.com/forums/viewtopic.php?f=31&t=107740

I had it custom wound by MAC to set a speed record...I'd highly recommend lacing it into a 20" wheel. The Grin Tech Motor Simulator says it will do about 35 mph in a 20" wheel. I was going to run it in a 29" wheel but only run it for a few minutes at a time. MAC estimates the Kv to be about 15.4.

 

[Triketech]

The presence of water (or any electrolytic fluid) will wreak havoc on bearings in a motor. They already endure a tough life living inside a constantly changing magnetic field that turns them into tiny ion pumps. On large AC motors the armature bearings can literally weld themselves to the armature if not properly insulated with inner & outer races connected to isolated slip rings to reduce current flow across the bearings.

I ran a MAC 12T for about 500 miles at 52V/40A on a trike before cutting back current to 30A. It's seen a full throttle 8AH discharge on a climb of 8% average (Mt. Lemmon) and it was pretty warm, enough that since the gear noise has increased from that ride. At about 1500 miles it went on my wife's trike at 36V @ 20 amps and now has about 5000 miles on it - still original.

My trike got a MAC 10T and with 52V/30A also has about 5000 miles. It gets pushed very hard, often on climbs with sustained 1200 watts. Getting ready to go through a teardown and inspection and have one spare clutch/gear set in case it needs it. (No it is not for sale). Also replacing a 5 year old LiFe battery that has weakened prematurely from hard use.

This is a link to the trike as it was in 2016; hasn't changed until a few weeks ago when I started to fabricate mounting pieces for the new battery.

http://www.triketech.com/Drivetrain/PowerAssist/HPV-MAC-V2.html

 

[Bullfrog]

About 1200 watts continuous is what the MAC can handle without overheating...unless you add some sort of auxiliary cooling.

For short periods of time, I have run 60A battery and 160A phase with not problems whatsoever.

I like Mobil SHC 100 for the planetary/ring gears....I put it on the ring gear about the depth of the teeth when I am assembling the motor. Never had any problems with any of the gears or the clutch at the power levels I mentioned above.

Temps...you can run 145C forever but I have not gone over 150C. Justin has run 145C on his dyno for extended periods of time as well. I set my Cycle Analyst to start rolling back the power if I hit 140C and to shut the motor down if I go over 150C.

Once you get above about 135C, it is a slippery slope so be careful .

 

[Bullfrog]

Triketech....that is a cool looking and well designed trike you have :thumb: .

 

[Bullfrog]

The presence of water (or any electrolytic fluid) will wreak havoc on bearings in a motor. They already endure a tough life living inside a constantly changing magnetic field that turns them into tiny ion pumps. On large AC motors the armature bearings can literally weld themselves to the armature if not properly insulated with inner & outer races connected to isolated slip rings to reduce current flow across the bearings.

I ran a MAC 12T for about 500 miles at 52V/40A on a trike before cutting back current to 30A. It's seen a full throttle 8AH discharge on a climb of 8% average (Mt. Lemmon) and it was pretty warm, enough that since the gear noise has increased from that ride. At about 1500 miles it went on my wife's trike at 36V @ 20 amps and now has about 5000 miles on it - still original.

My trike got a MAC 10T and with 52V/30A also has about 5000 miles. It gets pushed very hard, often on climbs with sustained 1200 watts. Getting ready to go through a teardown and inspection and have one spare clutch/gear set in case it needs it. (No it is not for sale). Also replacing a 5 year old LiFe battery that has weakened prematurely from hard use.

This is a link to the trike as it was in 2016; hasn't changed until a few weeks ago when I started to fabricate mounting pieces for the new battery.

http://www.triketech.com/Drivetrain/PowerAssist/HPV-MAC-V2.html

I agree...you don't want to get ANY water or contamination in your bearings. The bearings on a MAC are sealed but they can still get water in them if immersed. When I used distilled water and Motul MoCool as a coolant in my MAC, I ran about 4.5 ounces which is just enough to thermally connect the stator to the housing. In a static condition the fluid level was below the bearings. I ran the mixture for about six months and approximately 1,000 miles with no adverse effects to any parts of the motor.