eZee vs MAC? Your thoughts?

[neptronix]

Okay, you're actually right, when it comes to most of the power band. Especially peak.

My knowledge was based on the 0.35mm version of the motor. If you're using the GMAC, then you're probably simulating the 0.27mm lam version. So, i was off when it comes to that factor too.

However, if we take an equivalent winding GMAC and Cromotor, you'll see that the big DD can make more torque in the mid-upper part of the powerband.. and this is totally expected, because a geared motor begins to lose power and efficiency to gearing and stator losses at that point..

Here's an equivalent winding ( kv adjusted, battery voltage drop & controller power isolated ) comparison..

https://www.ebikes.ca/tools/simulat..._tuck&axis=mph&blue=Lbs&wheel=26i&wheel_b=26i



..i'd still want a DD for heat reasons and efficiency under cruising.. only because i have high speeds to go, long distances to cover, and very steep hills to climb.... but a modern MAC is very compelling, i get it

 

[Bullfrog]

I don't buy that the MAC/GMAC is dropping off due to losses. Maybe if you were running it on 72v or higher voltage...but on 50-52v. the losses have not started to stack up yet. The power is dropping off because it is approaching the peak rpm. The old MAC had losses that became relevant starting around 400 rpms based on Cellman's experiments. The newer MAC/GMAC can exceed that with minimal losses based on the Grin Tech Trip Simulator.

When comparing a geared hub motor to a direct drive motor, it is more relevant to match the top speeds and compare the curves than it is to match the windings and compare...IMO. In your example the Cromo is putting out more power because it is further away from its peak rpm. All electric motors drop in torque as they approach their peak rpm and in your example the MAC is closer. If you run the 8T MAC against the Cromo they have the exact same top speed with your conditions and the Cromo still produces slightly more power once you exceed about 24 mph but the curves are much closer.

I readily admit and emphasize, the MAC does have limitations that you can not exceed or it will overheat. Namely...you can not continuously exceed about 1,000 watts of input power based on Justin's data: https://www.ebikes.ca/product-info/gmac.html and that roughly correlates to 30 mph for my weight and aero drag on level ground and that speed decreases as your weight and the grade increase.

If you want to go faster than about 30 mph or continuously climb a hill the MAC is a bad idea but if you want very good acceleration, light weight, and to run about 28 mph then the 10T MAC is my choice. You can also dump about 60A@60V into a MAC and it will accelerate like a scalded dog...but you can't do it for very long :lol: .

Neptronix...In the Big Picture...I think we are in violent agreement . We just have different opinions about what is best mainly because we have different applications and that is OK.

 

[neptronix]

In all simulations i've seen, the top end efficiency of a mac starts to get poor beyond 30mph.. and that's where most of my riding is..
The newer 0.27mm lam versions aren't so bad at this, but the gear friction starts to become a greater % of the efficiency loss, the faster you go.

This is very exaggerated in the 20 inch wheel semi recumbent setups i have. Super noticeable. The eZee i have drops to 60-70% efficiency on the flats.. up hill at slower speeds, and the efficiency is pretty good.. but at ~400 wheel rpm at low load, it's an atrocity. So i'm thinking in small wheel terms here.. indeed.

What i see is a difference in efficiency/power curve mostly. When you add gears to a motor, you change this natural curve.. change the pole count in a motor, and you get that too. ( the Magic pie is a lot like the MAC )

We are pretty much in agreement and splitting hairs.. ultimately the ebikes.ca simulator is the best judge for your application. :thumb:

 

[Triketech]

Just in case I haven't mentioned it, the MAC will produce more torque per amp than any motor currently available which means better acceleration than any motor available :wink: ...that is why I am a huge MAC fan.

Sure. torque per amp will be very high on any very slow winding motor. An equivalently wound DD will outdo the MAC handily though, as a newer MAC maxes out at something like 85% efficiency, whereas DDs designed for ebikes can hit 92% peak. More power inputted will = more power outputted, the more efficient the motor design is.

A fully saturated MAC isn't all that fast. I know, i ran 4kW into one back in 2011. A 35mm leafmotor at 4kW will absolutely dust it, and also not melt within 5 minutes - it'll throw the front wheel in the air instantly and wonder why you aren't beating on it harder, and that's on a super fast 4T winding :lol:

What a MAC does very well is create a lot of power per pound and is also still the most efficient geared motor on the market. However, it's very poor at shedding heat, so it can't output that lovely high torque for very long.

..of course, if you want ultimate power density ( usually at the expense of even more efficiency, sadly ), a mid drive is the way to go, for sure..

Ergo efficiency at the bottom of the curve where most eBike motors live is primarily influenced by the frequency of pole switching. The MAC has about 3* higher switching frequency than most 1000W DD's. Its not until about 150+ RPM that a DD will match a MAC or even the Bafang geared hub in efficiency. Peak efficiency of a 1000W rated DD isn't typically reached until 175+ RPM. That's why a MAC always has more power left in the battery after a ride up and down a hill than a DD does; despite the DD regen the lower efficiency of the DD doesn't return enough power to offset the lower efficiency. Now if the hill is climbed at speeds of 20 MPH, the DD would win win, but thats not often the speed of the climb, and you'll probably want more like 2000 watts for that speed of a decent climb.

Mac 10T on a trike o the flat with 50V supplied by a sagging 52V battery will top out at about 30 MPH motor only.

I've run a MAC 10T up Mt Lemmon on a 500 WH battery at over 1000W until the battery was drained. Average 6% grade with as steep as 10% extended grades. In 100° summer Tucson heat. Ascended 2600 feet over 8 miles averaging about 18 MPH @ about 60WH/mile. The Mac winding thermister peaked at about 170° about 3 miles up and stayed there, and the shell was hot but not so hot I couldn't leave a finger on it for 5 seconds an not be burned at the end of the ride up. I now have about 5000 miles on the motor, and the spare gears are still on the shelf.

Suffice it to say I'm mighty impressed with the MAC 10T. We have two FWIW. Here is what we ride:
http://www.triketech.com/Drivetrain/PowerAssist/HPV-MAC-V2.html

 

[Bullfrog]

10T MAC would be my choice too...now that I have bought a 12T initially and then an 8T :lol: .

Experience is a heck of a teacher...I should be very smart by the time I die .

FWIW, I'd recommend Mobil SHC 100 grease in a MAC if you have it apart. Not worth opening the motor to change the grease IMO. I got the SCH 100 recommendation from the engineers at Mobil. Same as Mobil 28 except it has a lithium soap thickener instead of a clay thickener that is in the Mobil 28.

 

[Triketech]

FWIW, I'd recommend Mobil SHC 100 grease in a MAC if you have it apart. Not worth opening the motor to change the grease IMO. I got the SCH 100 recommendation from the engineers at Mobil. Same as Mobil 28 except it has a lithium soap thickener instead of a clay thickener that is in the Mobil 28.

Timely tip. I'll be opening it up soon just for inspection and lube.

Also finally getting ready to replace the battery. We do some serious hill climbing and one of the cells is (16S 1P) down to about 5 Ah capacity. Replacement is a Luna Shark so I'm fabricating a dovetail slider with a formed metal belt since its hanging upside down under the boom.

 

[Bullfrog]

Triketech...I used two of these hose clamps when I hung my 14s4p battery on the bottom side of my down tube:

https://www.mcmaster.com/catalog/126/334/

I cut pieces of inner tube to put between the hose clamps and the battery and between the hose clamps and my frame to add a tiny amount of "cushion".

It worked great...just don't over tighten the hose clamps as you could crack your battery case if you crank them down too tight.

I used a cloth tape measure around my battery and my frame to size the hose clamps.

Grin Tech also offers a "Bottle Bob" if you don't have water bottle mounting points where you plan to mount your slider. Here is a link: https://www.ebikes.ca/shop/electric-bicycle-parts/battery-accessories.html They come in single, double, and triple "Bobs"...at the lower section of the page.

 

[Triketech]

Triketech...I used two of these hose clamps when I hung my 14s4p battery on the bottom side of my down tube:

https://www.mcmaster.com/catalog/126/334/

McMaster is my "Engineering Mall", I've had an account for many years now. Here's an early image of what I'm planning.

Not shown is the battery strap and locking dovetail. I'm not sure if I'll use 2 aluminum straps or a laser cut piece of SS sheet with open triangles. The latter looks pretty cool but takes some experimentation when bending to form in the press.

 

[Bullfrog]

Looks good....I like the straps because not only do they support the weight but they also cut down on any lateral movement which might fatigue the hard mounting points.

Seems like you have a very good handle on it .