I just went from a 6 turn to an 8 turn Mac

[dogman]

Safe to say a few are glad I don't do a lot of graphs.

Absolutely right, whatever winding your running, the key thing is not stalling it, one way or another. But you can stall a motor too much even on flat ground. The key thing to me is running whatever winding you are running fast enough for that winding. If you prefer to ride slower, as I tend to on trails, then the slow winding suits my riding style.

I'ts not a best motor thing so much as a best motor for your riding style thing.

Because John runs a small wheel, his motors will act different than they would in a larger wheel. Less likely to stall the small wheel.

[mrdavies]

I own both the 6T and the 8T. Im running the 6t on a 29er(700c tire) on 12s lipo, and the 8t on a 26" wheel with 15s lipo. The 8t 26" setup has a 1.6" continental smooth sport contact on it.
First of all I love both setups and Im quite happy with the Mac motor and the great support from Paul (cellman), he's ben a great contributor to our passion! Im don't have a lot of miles on steep hills as most of my miles are sprinting on the streets on New York City. I ride and switch off between bikes all the time. The 6t has an overall faster top speed, with pedaling it tops about around 39 mph. The 8t has faster pickup and tops out around 34 mph. The 6t is much quieter,as the 8t on 15s has quite a whorl of a sound, much more noticeable then my 6t. Running a 29er with the 6t has been fantastic! The large wheel really helps soak up the bumps of the road. Having the 3 speed switch is great depending on the conditions and the traffic. Im usually on the middle switch, and going to high when I need the extra push passing taxis or making the light.

[veloman]

Thanks for the input Mrdavies.

I agree, I like both motors and Paul provides great support. These motors have completely changed the ebike game for me. Tonight I flew up a hill at 21mph which I would always fall to 12mph on with my crank drive I built 2 years ago. The efficiency and hence power of the Mac at even 50% no load speed seems incredible - I can't imagine it being much less than 80% eff.

The 8T has accomplished the two main goals of why I wanted to switch.
#1 Allow me to ride a proper 2" wide tire without pumping a ton of amps into it.
#2 Not burn up(possibly) my controller when it gets 100 degrees outside.

Low speed efficiency may also be improved, the jury is still out on that. I do think I'm 1-2mph faster on hills with it though. Top speed is something I should test, but will also be higher once I go to a123 battery next week hopefully.

[John in CR]

Low speed efficiency may also be improved, the jury is still out on that. I do think I'm 1-2mph faster on hills with it though. Top speed is something I should test, but will also be higher once I go to a123 battery next week hopefully.

Efficiency during acceleration will definitely be improved with the slower wind.

Being faster going up the hills is the perfect evidence that the gearing is wrong on the 6T motor, so why don't they just put different gears in there? The question I tried to ask before is, are they already at some practical limit of the gearing reduction of these motors?

[veloman]

Low speed efficiency may also be improved, the jury is still out on that. I do think I'm 1-2mph faster on hills with it though. Top speed is something I should test, but will also be higher once I go to a123 battery next week hopefully.

Efficiency during acceleration will definitely be improved with the slower wind.

Being faster going up the hills is the perfect evidence that the gearing is wrong on the 6T motor, so why don't they just put different gears in there? The question I tried to ask before is, are they already at some practical limit of the gearing reduction of these motors?

I would guess that using a different gearing in the motor would significantly increase costs. I think the goal with the different windings is to offer different top speeds, assuming the same voltage. Most people are getting the 10 or 12 turn if they are building a trail/off road hill climbing ebike.

When I first heard about the 6 turn, and it going 30mph on 36v, I thought "why not just get a DD then?"

My very first ebike I built was a brushed currie motor with no reduction, just a straight 1:6 chain drive ratio to the rear wheel (700c). That thing got hot very easily and had no balls on the hills/starts. No load speed was 46mph and I ran it at around 750watts on SLA. I didn't want to go 40mph on it, it was clear I would of been better off with gearing that let it top out at 30mph.

That's my situation now, I don't want to go 50mph, more like 40mph is acceptable (with 120% setting), though 95% of my riding is at 18-27mph.

So your thought is that you want the lowest turn count motor possible, and alter the gearing to match it best to your riding speeds? Is that the idea behind rc outrunners that spin 10k rpm?

I think working backward, basing your design on your top speed at your planned voltage is the way to go. For you, you want and need a low turn because you want 60mph and will feed it that power. 5kw on a low turn still will launch off the line and eat hills in most cases. But for me, I want to keep my wattage limited to 1200 or 1500w so I can keep reasonable range at ~22wh/mile. This statement may be flawed. I think some of you guys are suggesting to set it to high power like 2kw, and just use the speed switch to limit speed. (the one downside to this other than a slight decrease in efficiency is the extra wear on the Mac gears at 2kw.) I will be riding a123 very soon, so I will be able to put it at 40amps or 2kw.... (how long will 30amp andersons last at 40amps?) The thing is most of the time, I really only need about 800w to accelerate or 1000w to climb happily.

A current based throttle would fix that. Imagine driving a car with a speed throttle. 100% engine output at the slightest touch.....

[nonlineartom]

my everyday commuter is a 10T mac running on 44V with a 35A limit on the CA in a 26" wheel with 2.5" tires. It cruises along top speed of 24mph and it will quickly reach it's unloaded speed even on a fairly steep incline. It powers up steep hills no problem. Launches off the line like a champ

I also have an 8T mac in a 20" wheel and it's performance is almost identical to the 10T in a 26" rim in terms of acceleration and top speed.

I'd really recommend the 10T if you don't want to go over 25mph as it is fantastically efficient as it quickly reaches it's unloaded speed and then you are looking at 800W to cruise at WOT on slick tires, never gets warm either, even pulling 1600W on a sustain long hill climb.

That said. Putting 1.6-2.0kw through these motors does destroy the clutch pretty quickly. I've got 1000 miles on mine and the clutch bearing is buggered.

[dogman]

Wouldn't lower gearing require a larger diameter motor? (or smaller wheel)

I always assumed one of the benefits of the larger Mac, over the smaller diameter bafang types was the ability to run a larger diameter gear, essentially a longer lever.

I have thought for years, that an even bigger diameter gearmotor designed for 2000w, including built in torque controll mechanisims would kick some ass. Something like a gearmotor as robust as a 5304. Laced to moped rim of course.

10t would be my choice for trail riding 26" wheel. 8t sounds good for street at 12s. I really think 6t would be best in smaller rims.

[nonlineartom]

Personally I wouldn't take a mac trail riding, I'd want a direct drive for proper off road, I've heard of macs getting trashed because if the wheel is air born and the throttle is applied, the wheel touching down and meeting sudden massive resistance will trash the plastic teeth on the gears. It will probably also destroy the clutch very quickly with those high impact loads on the bearing. Mid drive mac would be ok for off road though. I really must get the hall fixed in my 6T so I can have the full family of motors. The stator / gearbox and axle all come out as one unit very easily so you can replace a rim and hub case with different turn motor units in a few minutes.

[dogman]

Perhaps I should rephrase that. If I was to choose a Mac for trail riding, it would be the 10t.

So freaking hot here where I live, my trail bike runs a crazy slow winding 9c 2812. But as long as you aren't hucking, I hear people have a ball trail riding Macs and Bmc motors in normal climates. One of the reasons I'd be choosing the slowish motor would be to avoid going airborne on the bike. In particuar, the one where I go for a nice flight and the bike doesn't.

I keep saying, 25 mph is my speed limit for going over the bars.

[kfong]

I ride my BMC all the time in single track and jump when I see an opportunity. It's held up well so far, even picked up a second one incase I have an eventual break down. Still running on the original after 3 seasons. Love the torque and low hum of the motor. It's fairly quite and usually goes unoticed. Can't imagine a better setup at 48 volts. Going to do a middrive with this motor on my DH frame.

[The Mighty Volt]

Great discussion! Liking what I hear about these MAC motors more and more all the time. If I had the bread, I would go with the MAC over a HT/HS series, just for the hell of it. Less weight, more finesse.

Direct Drive and over-volt if you don't want to pedal. The more I look at these motors and tinker with them, the more I like the geared set up, but its just too damn capricious for any sort of abuse.

If you do pedal, a higher-wind geared in a 20" with a granny-gear hooked up to an over-sized crank and fed by 20A-25A and a 12Fet sounds like the best for a decent blend of acceptable speed, and the utmost reliability.

24" is the biggest wheel I think I could tolerate at this stage. I don't care for high-end any more, 30MPH does me fine, but I want to keep that motor in her sweet-spot, and the smaller the wheel the better.

I was playing with a Cute/Ananda from cell_man, I have her in a 20" wheel, and at 15Amps and 36v, you would do well to hold that sucker back under full acceleration.

[gogo]

The ebike.ca simulator only lets me adjust parameters a few times on the single graph before I have to do a page reload. The double graph only gives me one real result between page reloads. Psycholist's "never" overheat result was an error from the simulator.

These graphs with the BMC speed and torque winds may be more representative of the difference between the 6 and 8 turn than the first graph I posted. Notice that at the same load from a 20% grade they both overheat in about the same amount of time if fed too much electricity. The efficiency difference ranges from about 5% to about 7.5%.

I confess that I'm biased toward using a high speed/low-turn count motor even though it's slightly less efficient at low speeds. The benefit to me is assist at high speeds to take advantage of tailwinds.

If your 750W high-turn motor tops out at 26 MPH and you have a 26 MPH tailwind, all you get is 26 MPH (no pedaling). With the low-turn motor a 26 MPH tail wind gets you 45 MPH (no pedaling). Its windy in Iowa and I'll be damned if some pedaler with a tailwind is going to pass me.

100% throttle, 11.9 KPH stall speed for low-turn motor

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100% throttle, 15.4 KPH stall speed for high-turn motor

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[psycholist]

I find it interesting that on the last 2 graphs, even though the throttle on the speed motor is reduced to 70%, the results are identical for the same motor at 100% throttle (as presented in the first 2 graphs).

[nonlineartom]

I can't remember who on the forum said it, but "one test is worth one thousand simulations" whilst the eBike simulator is a great tool, nothing beats getting out there and running a motor to within an inch of it's life and finding out, in the real world what it's limits are, and you don't have to break it to find those limits.

Perhaps it's just the way I assimilate information but I find I learn a lot more by doing than looking at simulation graphs. There are just too many variables like tyre type and size, road surface type, e.t.c outside of the parameters of that simulator that have a big effect on the overall experience, I see a lot of people taking these simulations as hard fact rather than an educated hypothesis of how the technology will perform

Then again, that's what makes me a "bodger" not an engineer I guess.

[motomech]

Where in the heck is there a 20 % grade in Iowa?
That would be the place for a fast wind I would think.

[gogo]

Where in the heck is there a 20 % grade in Iowa?
That would be the place for a fast wind I would think.

The 20% grade was just to illustrate an overload situation. I've done the bike ride across Iowa and you'd be surprised how many hills there are.

I can't remember who on the forum said it, but "one test is worth one thousand simulations"

The quote is: "One test is worth a thousand opinions", and a simulation is a form of test (in my opinion ).

psycholist, the early parts of those graphs are where battery current limiting are in effect. When the controller is in this mode its doing the same thing that turning back the throttle does. Point being is that if you turn back the throttle on a low-turn/high speed motor it will have performance characteristics very similar to the high-turn/low speed motor, but will be 5%-7.5% less efficient.

[psycholist]

Thanks for the explanation gogo. So, to resume throttle effectiveness, you would need to reduce the throttle below the current limiting threshold of the controller? I haven't even ridden an e-bike yet, (still in the building stage). Just started playing with the sim, trying to get a feel for motor system behaviour in various situations.

[veloman]

26mph tailwind does NOT mean you will go 45mph on 26mph normal power. Are you crazy?

When I was on the FL I had an insane tailwind, about 20-25mph sustained. I sprinted full out on my road racing bike (no electric) and still only got 45mph, and that's on 1300watts of power in spandex on an 18lb bike. I normally could hit 38 with no wind.

I would also never recommend an ebike to have a top speed of 26mph.

[gogo]

26mph tailwind does NOT mean you will go 45mph on 26mph normal power.

According to http://www.kreuzotter.de/english/espeed.htm it does. I'm not advocating 26 MPH ebikes, just trying to illustrate the advantages of a low turn motor. You are right though, that 5%-7% better efficiency is significant if you are never going to use the higher speeds.

750W = 26 MPH on high turn motor

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750W+26 MPH tailwind = 45 MPH on low turn motor

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[veloman]

Well, as we have been saying, simulations are only helpful to a point.

Even with going to a slower wind motor, I still can approach upper 30mph range. I could even add more volts too. I think going from 36 or 48v to 60-72v is easier to do than adding amps. You can simply series in a lipo brick or similar. That's what I've been doing for a a few months.

From preliminary tests on an 8% grade hill, my 8T looks to be 73% total system efficiency at full load (1150watts) dropping to 17.5mph zero pedal. I pedaled easily and went 20.5mph at the lowest. Does 73% efficiency at 44% no load speed sound right?


If I was building a recumbent low racer for non-hilly or city riding, I would use my 6 turn. I may be doing this, but don't have super lowracer -friendly roads around here. Being able to get into the mid 40mph range would be valuable on a low racer. Doing that on an upright would be too wasteful or expensive IMO.

[John in CR]

Point being is that if you turn back the throttle on a low-turn/high speed motor it will have performance characteristics very similar to the high-turn/low speed motor, but will be 5%-7.5% less efficient.

About the only thing true here is that turning back the throttle on a speed wind motor will make it slower and lower power like a high turn count motor.

[flathill]

Which wind has the most copper? The other reason the sim may not match the real world is the halls are often misaligned combined with a trapezoidal controller and your harmonic copper losses may be much higher than you expect at low throttle.

a trap (almost square wave clipped sin) controller will give motor more burst power but sinu more continous power (less harmonic losses)

[stripedtuna]

Hi everyone..

I use my 8T for a fairly flat commute to work, and love it.. Most people have talked about how good these motors go when you want to accelerate fast and get high speeds (and i agree totally) , but i just wanted to also state how happy i was with its smooth operation at low speeds.

Some parts of my ride involve bike track sections that are also shared by people walking, with blind bends that have overgrown trees making the track narrow. I only like to go at very low speed (like walking speed) through some of these spots. Also when i get to the carpark at work, I also only go at very low speed through the carpark to the bike rack. The 8T mac does this really well in my opinion. Its take off (im using a 12 fet controller) for low speed is smooth and doesn't jerk between no throttle and then too much at all. In fact the throttle for me is very gradual, thus allowing me to crawl on low throttle with ease. This surprised me. it is my first e-bike so I cant compare to anything else. Are most e-bike setups good at going low speed smoothly with nice gradual throtlle increments?

Ed.

[kfong]

This is one of the advantages of a geared motor. It allows the motor to spin at a faster rate so very slow starts have some degree of linearity. One of the reasons I like the BMC for trail riding, the throttle response is very good for single track. I've used a 9C 9x7 and felt it lacking in low end torque and response was poor for trail use. I still haven't tried my 6x10 yet to compare.

[Toango]

For my first install i have an ebikekit geared reared motor on 52v with 25 amp 6 fet controller on a 20" folding bike and i like how much torque it produces. Enough to pop a wheelie and take off fast on red lights. I also have a 7 turn mac motor that i briefly tested and it does produce noticeably less torque than the smaller ebikekit motor but the speed is faster from 20mph to 27 mph.

Anybody know how many turns the ebikekit motor is? Runs well on my setup for a small little motor.