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

[veloman]

Update, my thoughts are changing as I ride this 8T more, newer posts tell more of the story.
_______________

Okay, I am blown away at how well my bike performs on the 8T (with upgraded phase wires, from Cellman). My previous setup was the 6T on 48 volts 21amps, with a tiny 26x1.5" tire.

Now I just test rode for the first time, the 8T with a much bigger 26x2.05" tire (considerably bigger wheel) on 36v 21amps.

0-23mph acceleration is nearly identical. I dropped to just about the same speed on the hills. WTF! How is this possible? This tells me that I was throwing away 200watts of power into heat during every acceleration/hill on my old setup! Holy crap!

I did 4 miles tonight, a couple steep hills in my area (8% for 100meters) and bunch of accelerations and full throttle to 26-27mph. Motor didn't feel like it got any warmer, controller cold too (I did mount it for better airflow though).

6 turn = high speed wind = lowest torque (compared to 8T, 10T, 12T), wants to go so fast that you need to use a high power battery and have the desire to go fast. I would really not advise the 6 turn unless it's for a small wheel build, or you plan on pumping 30-50amps into it. Definitely not a good choice for a 26" wheel on an efficient low/moderate speed setup.

I wish I switched sooner! Now I can ride a much more appropriately wider tire! Oh boy it's going to be fun when I get the 52v battery on there, and see what 30-50amps does... Heck, I could simply ride my old low power 36v 21amp limited battery again. Last month I rode the big tire with the 6 turn on just this battery and the bike couldn't move itself, barely!

So lesson to the noobs is - don't overgear your motor!

[mud2005]

nice writeup, quick question. what is the default wind, 6T?

I have an older mac and it goes over 30 mph at 48V in a 26" wheel.

I was thinking of putting it on my bmx in a 20" wheel. according to your info this would be an improvement in efficiency, but have a lower top speed?

[veloman]

8 turn is the normal default wind.

my 6 turn on a 48v hot battery would have a no load speed of near 50mph

You definitely don't have a 6 turn, that's an 8 turn.

As for efficiency, it all depends on what you speed you want to go. If you don't want to go over 20mph, then the 8 turn in a 20" wheel would probably be best. But the 8 T in a 26 wheel is a nice setup, that's why it's the default. On 20amps, or 800watts peak, it moves most riders fairly well.

I haven't done any real efficiency testing, but based on the performance I just saw tonight, it looks like the the 8T is significantly more efficient on starts and hills than the 6T, given my power levels.

[dogman]

The scales fell from my eyes, when I began to ride different winding motors up steep hills with a CA telling me the watts.

At a certain point, if giving the motors "normal" voltage and amps, you see the fast motors start to really stumble. Most aren't that bad at 5%, at 7% you see some difference, and by 10% you see the slowest motors really start to shine. With the CA telling all, you really see how 10mph up a 10% grade is no problem for the slow motor, while the fast one is pegged on max amps.

There is an easy fix though, if the hill is shorter. Blast it with watts and ride up faster. But that works better legaly in some places than others. If your local law is not limiting you, just get a bigger motor, smaller wheels, and let er rip.

But if your hills are 5% grade or less, the fast windings work just fine, and get you faster top speeds the whole ride.

[Joseph C.]

Okay, I am blown away at how well my bike performs on the 8T (with upgraded phase wires, from Cellman). My previous setup was the 6T on 48 volts 21amps, with a tiny 26x1.5" tire.

Now I just test rode for the first time, the 8T with a much bigger 26x2.05" tire (considerably bigger wheel) on 36v 21amps.

0-23mph acceleration is nearly identical. I dropped to just about the same speed on the hills. WTF! How is this possible? This tells me that I was throwing away 200watts of power into heat during every acceleration/hill on my old setup! Holy crap!

I did 4 miles tonight, a couple steep hills in my area (8% for 100meters) and bunch of accelerations and full throttle to 26-27mph. Motor didn't feel like it got any warmer, controller cold too (I did mount it for better airflow though).

6 turn = high speed wind = lowest torque (compared to 8T, 10T, 12T), wants to go so fast that you need to use a high power battery and have the desire to go fast. I would really not advise the 6 turn unless it's for a small wheel build, or you plan on pumping 30-50amps into it. Definitely not a good choice for a 26" wheel on an efficient low/moderate speed setup.

I wish I switched sooner! Now I can ride a much more appropriately wider tire! Oh boy it's going to be fun when I get the 52v battery on there, and see what 30-50amps does... Heck, I could simply ride my old low power 36v 21amp limited battery again. Last month I rode the big tire with the 6 turn on just this battery and the bike couldn't move itself, barely!

So lesson to the noobs is - don't overgear your motor!

Welcome to the eight turn MAC club.

[neptronix]

I think a lot of the efficiency difference has to do with you running the 6T mac on inadequate amps. Definitely ran outside of it's efficiency band the majority of the time. I know you pedal a lot, but your electric efficiency was less than optimal.

high speed motors ( and 30mph on 36v / 26" wheel is quite a ridiculous ) require gobs and gobs of amps to move along. Hit a hill and that amp requirement climbs massively, and you find yourself needing a 12 or 18FET 3xxx or 4110 controller to supply all the amps it wants, lol. The truth is that you could have got the 6 turn to go fast, but you needed to feed it more amps than your battery could ever supply. Your phase amps would probably be really high too; requiring an upgrade of phase wires maybe.

Volt up, gear down! Can't wait till you one day experience what a slow winding on a tiny wheel on an ultra high voltage / amp setup is like. You're a little closer to that ideal now

[John in CR]

But the 6T in a 20" would eat the 8T in a 26" in every way. It's the gearing, not the winding that was the problem. To bad MAC doesn't get that and run at a greater gear reduction, unless they're already at some materials limit in terms of the gear durability that prevents increasing the ratio.

Veloman, do you want to get rid of that oh so terrible 6T, so I can show people how to run those motors at 4-5kw?

[neptronix]

But the 6T in a 20" would eat the 8T in a 26" in every way. It's the gearing, not the winding that was the problem. To bad MAC doesn't get that and run at a greater gear reduction, unless they're already at some materials limit in terms of the gear durability that prevents increasing the ratio.

Veloman, do you want to get rid of that oh so terrible 6T, so I can show people how to run those motors at 4-5kw?

Sorry to break this to you, but the gear reduction limit has to do with the extremely high electrical RPM that geared motors run at. Internally the motor is running at 5x the eRPM ( due to 5:1 reduction ) for starters.

cell_man has warned a few users against running their MAC motors in 26 and 20" wheels. The limit is the infineon controllers. I think they choke around 6000 electrical rpm ( wheel rpm x 5 x 3, i think is how you would calculate it? )

If you can come up on some controllers that can handle >10000 electrical rpm, you could have yourself a wicked motor.

Personally i am just waiting for the dual stator MAC to come out.. i will quickly lose my obsession with the magic pie and any other DD...

[veloman]

Let me clear some things up. The 6 turn is only slow because is has less torque at my low amp levels. Watt for watt, the 6 turn can't compete on hills or accelerations at normal 'low' power levels. Yes, it would haul ass if I gave it proper amps. The point I make is that on lower power it doesn't perform, which should be obvious.

Yes its not that 6 turn is a bad wind, it just belongs in a smaller wheel or ridden at high power. Riding a 50mph motor at 20mph is simple going to be less efficient than a 35mph motor in most cases.

if your goal often time is to ride at around 20mph for efficiency, then there's no question that a slower wind is the better choice. When I go back to my 48 or 52v battery and set speed3 to 120%, I should still be able to hit upper 30mph range. I very rarely rode the 6 turn above 35mph anyway.

I really think the minimum you should run the 6 turn on is 30amps when in a 26" wheel.

The best part is now my controller and motor should stay considerable cooler. And better range!

[REdiculous]

cell_man has warned a few users against running their MAC motors in 26 and 20" wheels. The limit is the infineon controllers. I think they choke around 6000 electrical rpm ( wheel rpm x 5 x 3, i think is how you would calculate it? )

If you can come up on some controllers that can handle >10000 electrical rpm, you could have yourself a wicked motor.

I wonder if you couldn't make a simple-ish device that uses multiple external controllers to control 1 motor...

Code: Select all

onHallTick(int whichHall) {
if (rev_cnt == odd) sendSignalsTo(controllerOne, whichHall);
else if (rev_cnt == even) sendSignalsTo(controllerTwo, whichHall);
else bark();
}

In english...
On odd-numbered revolutions controllerOne does the work. On even-numbered revolutions controllerTwo does it. After each revolution the rev_cnt is increased by 1 (not shown).

I just woke up so if that's not making sense..fine. :p

[veloman]

I think a lot of the efficiency difference has to do with you running the 6T mac on inadequate amps. Definitely ran outside of it's efficiency band the majority of the time. I know you pedal a lot, but your electric efficiency was less than optimal.

The 6 turn wouldn't be any more efficient at higher amps, at the 18-20mph range I climb hills at. It doesn't matter how much power you throw at the 6 turn, the fact remains that riding at 40% of it's no load speed is inefficient compared to 60% of it's no load speed of the 8T.


It's pretty simple. Pick a motor setup that just hits the top speed you want, nothing more. My 6 turn in the 26" wheel might be fine for a low racer recumbent in flat land, where I will want to go 40-45mph and accept that to have that, my low speed efficiency won't be as good as the 8 T.

[dogman]

You got it. The 6t winding is not a "bad winding" but its not often the best choice for 26 or 27" wheels. Put that winding in 20" wheel, and the difference in wheel size gets it back into the more efficient rpm when it's going up steeper hills.

Pick the wrong motor and just heave more watts at it is not the solution. The solution is pick the right motor, then if you so choose, you can heave more watts at it. But you aren't forced to do that. You can have a bike like vehicle at lower wattage if you like that. Where and how you ride introduces tons of variables that all need to be considered.

Way too many folks on this forum considering only one variable in the equation that includes wheel size, rider weight, motor winding, volts, amps, coefficeint of drag, etc. Mostly these people are relatively new.

The typical question, "what's the wattage limit for motor X?" Answer, it depends on......

[Polerkongen]

Hi

Interesting posts now that I´m waiting for a MAC 7T to arrive at my door.

I hope its not to much of a high speed wind as I´m only going to be feeding with 12s lipo. I was considering the 8T at first but I wanted to hit 30 mph on approx. 44v as the 2x6s lipo give me. So figured the mix between 6 and 8 was be just fine for me.. (and Paul didn´t have a 6T in stock when ordering )

Anyway, will post a litle review once up and running, cant seem to find anyone else with those turns on the MAC..

[gogo]

Watt for watt, the 6 turn can't compete

Doesn't LFP like to tell us that the motor only "sees" watts, regardless of which battery/controller is supplying them?

The graph below would seem to indicate that a low-turn/high-speed motor can still be very efficient when compared to a high-turn/low-speed motor. Isn't this what Methods has been saying?

Subject: Premium 9C hub motors in rare low KV windings - 8x8, 6x10
"electric vehicles … can be both a hot rod and ultra efficient with the *exact same setup*.

Yes, you can get a slight efficiency increase by limiting your system with a high turn count motor, but the increase is very small. Why not pay a little more for a high discharge rate battery and controller and then use a 3-position controller/throttle switch for easily controllable low speed operation while retaining high speed and power capability?

high and low turn count at same wattage

graph4.jpg (168.68 KiB) Viewed 699 times

[veloman]

You should see how much my controller heats up using the 6 turn and riding at slow speeds.

I have to admit that the 8T on 800 watts is actually not as powerful as the 6 turn on 1000w. Last night I did notice the lack of 'punch' I had on the 1000w setup. I really should do more precise testing with the watt meter. Today I might go back to running 48v 1000w, and see how the 8T handles it. Another thing to muddy the waters is that I'm running a larger tire now too.

The simple fact is that running at 40% no load speed is not as efficient as 60% no load speed. I don't know how you can argue against that. Why bother with a high speed motor if you will never use that top end speed due to power limits?

A 3 speed switch helps reduce the launch on takeoff, but these voltage based throttles will still suck full power if the terrain and speed request it. Goodbye efficiency IMO.

[John in CR]

Something most still miss is that given the same motor with the same voltage, and gearing to the same velocity, the lower turn count motor always wins in all categories. Of course you need a controller capable of the electrical rpm...Kelly offers them up to 100k. The lower turn count motor will be more powerful and typically more efficient as well as cool itself better. It's just a matter of the right gearing.

[dogman]

Which is fine if you are gearing to the same velocity. But if you aren't...

I just keep saying, in various poorly commuicating ways, that IF you are committed to larger wheels, then it makes sense to go to the lower speed motors. Then you stall the motor less, particulaly if you are also commited to wattage close to usa legal limits.

Were I in CR, I'm sure I'd be building very very different types of bikes than I do here in the USA.

What I really don't understand, is wanting the high speeds from hubmotors at 44v. Easy as pie to volt up for more speed.

[chroot]

@veloman-

Hi Your 6T MAC should have gone laced to 20" wheel instead 26". I was plan get 6T 1k watt motor and Paul warned me it would be best use 20" rim so 8T is best for 26" rim.

Anyways, Glad you learned something new between 6T and 8T motors.

[psycholist]

Can't figure out how to transfer (copy/paste) gogo's graph on previous page into my post.

I just did an experiment with this simulation. On "system B" I decreased throttle to ~46% and increased grade on both systems to 12%. According to the simulator "system B" (fast wind motor) takes twice as long to overheat! This seems to contradict dogman's real world evaluations. Dogman, Can you explain this discrepancy? Does the simulator need improvement?

[dogman]

Can't explain it. I just stupidly ride along watching wattmeters and thermometers seeing what happens.

All I know is stalling the motor is bad. So either use a motor that stalls slower, or like John, give it enough power to not stall and zip up the hill.

[spinningmagnets]

Can't explain it. I just stupidly ride along watching wattmeters and thermometers seeing what happens.

I'm getting so tired of you posting all these practical "real world" suggestions. I want to see some arguments, and also some graphs to support your so-called "actual results",...pie-graphs, bar-graphs, AND,... large fonts in multiple colors to emphasize when you disagree with a new poster.

You may start....NOW (*sips beer and taps foot*)

[Grinhill]

I think it would be "safe" to say not everyone would pick up on those references spinningmagnets...

[psycholist]

Well, as much as I appreciate all the work that has gone into the sim (Thank You Justin!), it just shows that you can't rely on it 100% (yet)! It's the real world evaluations such as dogman's that help find these discrepancies and eventually result in an accurate sim.

[kfong]

Simulations are just what it implies. Even Justin had to look at real world results and modify his formulas to match results taken from actual measurments. Graphs and charts have little meaning without a good understanding of all the dynamics involved.

[John in CR]

Can't figure out how to transfer (copy/paste) gogo's graph on previous page into my post.

I just did an experiment with this simulation. On "system B" I decreased throttle to ~46% and increased grade on both systems to 12%. According to the simulator "system B" (fast wind motor) takes twice as long to overheat! This seems to contradict dogman's real world evaluations. Dogman, Can you explain this discrepancy? Does the simulator need improvement?

Partial throttle can be hard to modulate on hills, and pulses kill you. OTOH, the partial throttle is done thru (PWM) Pulse Width Modulation) by the controller as is the current limiting function. The approach the manufacturer uses with my main high speed wind motors is to control max speed by limiting current. I've posted graphs of what happens with high speed wind motors when you restrict their current, and the result is a very broad and flat efficiency curve. I suspect that's what you're seeing as an end result in your sims, the high speed wind motor being more efficient.

Here's a 5302 limited to 25A. Look how broad and flat the efficiency curve is above 70%.

5302 simulation 66V 25A.JPG

(41.14 KiB) Downloaded 2 times

The compromise is that you give up starting torque, but personally I don't like twitchiness in throttle response. Give me that smooth continuous electric acceleration of a high speed wind motor every time. I have to think that the guys who like to pedal would want smoother assist too, so they feel like Superman. You do also need to gain an understanding of your motor's limits, so you understand the minimum speed you need to maintain on hills to avoid meltdowns.

I preach this stuff all the time. Consider this though, I've never melted a motor while riding and at 250lbs plus 125lb bike I have a heavier load and tackle mountains, not hills.

John