12T MAC motor and high current

[drbenjamin]

Appreciate the thread - I have a 12T Mac kit coming from em3ev (30A 9 FET controller) that I'll be putting in a 700C wheel. A little concerned about heating, so here are a couple of questions

1) "steep" is a bit subjective in describing hills. I live on top of a 400' hill, the road up is ~0.4 mi of 10% grade followed by 1 mi of 3-5%. I can pedal to the top of this hill, it takes a while but I do it, so I'll estimate that I can put 200W into the effort. Me + the bike + groceries will weigh ~300lbs. ebikes Motor simulator thinks I'll be OK, do people here who have used the Mac 12T agree?

2) I will probably also post this question into the oil cooling thread, but has anyone here tried it and stuck with it? I don't mind the setup and a little extra maintenance if it works long term.

Thanks for the help, I know that in the end I'll try this kit and if it can't handle the load I'll go to a BBSHD.

 

[kevinscargobike]

I live on a 180 ft hill that averages 9% but has one 15%+ section at the end. I have a Mac 8t in a 20” wheel on a 100lb cargo bike, the only time I haven’t made it up the hill was with an adult passenger, making for about a 450lb total weight, and a battery that was only 50% charged. I think I was running at 40A 52v at the time, lately I’ve been letting it try to get 50A from my battery.

I’ve hit 90-100C once or twice on hot days, but never until I’ve crested the hill and slowed down.

I’d really like to try a higher torque motor and just use FOC to get speed, I’d wanted to make it to the 25mph-ish range, but with the Phaserunner I’ve hit 34 mph which is way faster than I need the bike to go. I bet a 12t would be perfect.

 

[Krohnk]

I have a 10T with a 40 amp controller and a 52v battery , peaking 50 amps and 2.5KW, 700c wheel and it moves. Never had eny issues with it. Kinda got so used to it i want more^^ i have ride it for 1182km til now. Eny one know how much the motor can take? Is like 3KW possible?

 

[amberwolf]

Probably not.

The gears and clutch can only take so much torque.

Another issue is the motor design doesn't allow good cooling of the core, so heat builds up much more easily than in a DD hubmotor, and it's harder to get out. Statorade or oil cooling might help, but probably not enough for what you're asking of it.

If you like, you can go to the http://ebikes.ca/simulator and read the whole page, then setup your system (as close as you can get) in the simulator as A, and the proposed system as B, and compare them for overheat/etc information. (I don't think it simulates when the clutch breaks, though).


However...what exactly do you want "more" of?

Speed?
Torque?
Accleration from 0 to present max speed?
???


If all you want is more torque, add a second motor in the other wheel. You'll get at least double the acceleration time, for instance.

If you want more speed, you need higher voltage to cause faster RPM, and probably also more power to overcome the wind resistance at the higher speed. But geared motors are hard to drive at high RPMs; its' an ERPM thing (a search on ERPM should show you what I mean).


The simulator will help you see the relationships between different things, to help you figure out what you'd need to change to get what you're after.

 

[Bullfrog]

My experience...running a 12T MAC, 14s5p battery, 40A Infineon 12 FET 3077 controller in a 29" wheel with a Maxxis Hookworm tire. Most hills are not a problem and the top speed is about 25 mph. I weigh 200 lbs and the bike weighs 65 lbs for a total of 265 lbs. You can go to a smaller wheel/tire and the MAC will climb mountains but the top speed will decrease proportional to the tire diameter decrease.

The 12T MAC will have more torque than a lot of direct drive motors running 72v and higher amperage. If you are concerned, run your parameters through the Grin Tech Motor Simulator: https://www.ebikes.ca/tools/simulator.html and select "thrust" at the bottom to compare to other motors/wheels. Torque is constant regardless of wheel diameter and can be misleading IMO.

I routinely run my MAC at 130C and don't roll the power back until 135C. I have it set to shut down at 145C since Grin Tech has done testing to show that the MAC did not sustain any permanent damage after running it at 145C on the dyno.

The same is true for the GMAC since it is the same motor just no clutch.

I run a 40A 12 FET (3077) controller and it never even gets warm.

Tried 55A for a little while and no problems whatsoever with the clutch or the gears. Warning...I would not recommend the MAC for off road riding where you will be pounding rocks/roots. The little springs in the clutch can get knocked out of place and the clutch will not operate properly. Mine just locked up and wouldn't freewheel so I could still ride and get regen but it might be an issue for some. Never had a clutch problem as long as I don't beat the crap out of the rear wheel...my bike is a hardtail.

Obviously I am a little prejudice towards the MAC but it has been a great motor for me and the 5:1 reduction gives you extra torque.

As some have mentioned, it does have the limitation of not shedding heat very well due to the air gap between the stator and the housing but running the temp probe that comes in all MAC motors from EM3ev and programming your Cycle Analyst can ensure you don't damage anything .

 

[AHicks]

I'm running a MAC 12t with 26x2" tires in a hilly coastal area on the Gulf Coast side of Florida. My weight with the bikes is 380 lbs. I'm running a 35a 12 fet KT based system purposely limited to 1100 watts or so that is very rarely used.

I don't think you'll have any trouble at all with conservative power settings. It should have no trouble climbing your hill at maybe 5-700 watts with a speed in the mid to high teens.

Very happy with mine. My only disappointment is that it's not a GMAC w/Phaserunner setup to allow the variable regen. Speed left unchecked, coming down some of these bigger hills can result in.... well, I wish I had regen!

 

[john61ct]

IMO gotta have regen for safety,

regardless of whether you use the power produced or not

with a heavy load and steep hill country

Mechanical braking is much more difficult to make reliable.

 

[qwerkus]

Back to the Original topic. 12t mac will work, but if you want to run 40 amps, get a direct drive motor of any kind. Sheds the heat better.

But because of weight, a way smaller wattage would be a bad idea too.

Macs or other motors of that type have a good track record of standing 30 amps of 48v. Also, all the shit you read is not talking about heavy weights up steep hills. 400 pounds total weight, and 1000w up a steep hill will melt a mac, if the hill is long. So a mac may limit the mountains you can go up.

A low rpm DD motor would be better for you, especially in 26" wheel.


To mlv. that would be fun, for about 5 -10 miles, then it would melt. 10 miles of that will also melt a 500w size DD. As I found out at the races. Do go ahead and do it though, melting motors is great fun.

This. We should sticky a thread about asking for motor selection advice. Without knowing the size of the wheel and the expected system weight, it's difficult to formulate any clear advice. Knowing from experience swiss mountains and given the additional weight of velomobiles, I'd say a hub motor is only an option if he uses a 20" rear wheel or choose to motorize the 2x front wheels. In any other case, I'd go for a mid drive solution. Cleanest I know about for tadpole trikes is the cyclone implementation by veloks.

 

[Bullfrog]

IMO gotta have regen for safety,

regardless of whether you use the power produced or not

with a heavy load and steep hill country

Mechanical braking is much more difficult to make reliable.

The GMAC offered by Grin Tech is a MAC with regen and a few additional improvements. IF I was buying a new motor, I would give it serious consideration .

 

[john61ct]

IMO gotta have regen for safety,

regardless of whether you use the power produced or not

with a heavy load and steep hill country

Mechanical braking is much more difficult to make reliable.

The GMAC offered by Grin Tech is a MAC with regen and a few additional improvements. IF I was buying a new motor, I would give it serious consideration .

Can it be used in front?

 

[AHicks]

IMO gotta have regen for safety,

regardless of whether you use the power produced or not

with a heavy load and steep hill country

Mechanical braking is much more difficult to make reliable.

The GMAC offered by Grin Tech is a MAC with regen and a few additional improvements. IF I was buying a new motor, I would give it serious consideration .

Can it be used in front?

The GMAC has some pretty serious braking capability. Not something I would want in front.

 

[Bullfrog]

Grin Tech doesn't currently show a "Front" version of the GMAC: https://www.ebikes.ca/shop/electric-bicycle-kits/gmac/gmac-rear-kit-basic-throttle.html

You can send Grin Tech "sales" an email and ask them about the possibility. They have been very responsive and helpful for me in the past..."sales@ebikes.ca".

You can take a MAC "front" motor and weld the freewheel clutch so it doesn't freewheel anymore and create your own front GMAC motor...not worth it IMO but I am lazy :lol: .

The amount of braking/regen is adjustable so you can decrease it...but if you decrease the braking you will also decrease the regen so it might not be worth all the effort. All up to the individual user .

 

[AHicks]

Grin Tech doesn't currently show a "Front" version of the GMAC: https://www.ebikes.ca/shop/electric-bicycle-kits/gmac/gmac-rear-kit-basic-throttle.html

You can send Grin Tech "sales" an email and ask them about the possibility. They have been very responsive and helpful for me in the past..."sales@ebikes.ca".

You can take a MAC "front" motor and weld the freewheel clutch so it doesn't freewheel anymore and create your own front GMAC motor...not worth it IMO but I am lazy :lol: .

The amount of braking/regen is adjustable so you can decrease it...but if you decrease the braking you will also decrease the regen so it might not be worth all the effort. All up to the individual user .

For the GMAC to work as designed, you're going to need a controller that will allow variable regen. A simple on/off switch isn't going to cut it like it will on a direct drive. WAY too much braking available for that to work. Grin has the Phaserunner controller set up to do this nicely. Throttle turns into a variable brake when the bakes are applied (wide open throttle = full brake). Bonus is this controller can feed a very small amount of power while coasting as well. This to eliminate the small amount of braking that's normal with direct drives, let's you coast like a clutched gear drive.

 

[john61ct]

The GMAC has some pretty serious braking capability. Not something I would want in front.

I understand the issues, let's set that aside for now.

My question is, can that motor physically be made to work in front?

 

[Bullfrog]

It is probably 135mm between dropouts so unless you can get a fork that is that wide, it will not work.

 

[john61ct]

Y'all think that would that be the only obstacle?

 

[Bullfrog]

My first recommendation is check with Grin Tech to make sure everything I am saying below is correct :wink: .

I believe it would work but I have never done it hence my recommendation above. Most fat bike forks are 135mm or 150mm OLD (over locknut dimension) i.e. between dropouts. As long as your frame will accept the fork you select and the fork is 135 OLD AND will accept a 9mm, 3/8", or Quick Release axle...it "should" work.

Some of the higher end fat bike suspension forks like the Bluto have a thru axle...they would not work with the MAC/GMAC. Well I guess it is possible but it would require a LOT of work :lol: .

The rigid fork that came on my Mongoose Hitch is 135mm OLD and I have seen a few strong dual crown rigid forks on ebay that are fairly inexpensive that should work. Luna sells a fat bike suspension fork that is 135 mm OLD.

Nothing wrong with getting info from Grin Tech even if you don't end up buying the GMAC motor. They may have an option for you that we haven't considered if you give them all your parameters and tell them what you are trying to accomplish.

I personally would not go with a "front" motor just because forks are not designed to be pulled and pushed on...you have a force out there on the end of a long lever arm and in the long run it may create a problem. But that doesn't mean it won't work...just my preference for a "rear" motor.

Just FYI, Grin Tech provides the "Endless Sphere" forum for us .

 

[john61ct]

Great info thanks.

Wil wait til closer to actually trying before bothering Justin.

 

[Bullfrog]

Need help finding a 10T MAC Rear Freewheel 135mm motor...EM3ev is no longer selling the MAC. Tried to contact MAC directly but I have not gotten a response.

Anybody have a suggestion on where to buy a 10T Rear Freewheel MAC besides Alibaba? I need the freewheel as opposed to the cassette version because I have several rims laced to MAC Freewheel hubs and I'd like to continue using them. If I have to change to the cassette version, I'll just go with the 10T GMAC.

Thanks