"peak power" - Trek 4300 20" Magic Pie build.

[toolman2]

I don't know how much torque the pie makes, but both the ebikes.ca simulator an my own simulation using SWBlutos predicts that I'm making 350 N-m / 258 ft-lbs of torque at 0 rpm at 125V 100A into the motor with a 20.2" wheel. It jumps to about 480 N-m at 125V /355 ft lbs at 200A (why I'm trying to get a longer swing arm).

the std pie makes about 1.3NM per phase amp, and in delta its .75NM per phase amp.
-thats up to around 100NM where saturation begins, in fact to make 100NM the winding temp went from 40degc to 160degc in 20 seconds, and resulted in 2890w of heat to dissipate.

so without drilling, the pie can constantly dissipate a max of 290w, so to my way of thinking 100NM is only ok for 10% duty cycle?? (290w being a tenth of 2890w?).
480NM sounds a bit keen, if you mean 200a and 125v into the controller at 0 rpm, then you have around 25000w to dissipate, this may be troublesome..
-maby do it inside with a fire extinguisher handy, cos that would heat an entire large house in winter. :lol:

 

[neptronix]

scorpion: that's a 7.4% mean grade as shown in the picture. It's basically a 1/3rd scale version of what i'll be climbing.

zombiess: that sucks that you are the only Vegas guy. I'm in that situation in Colorado Springs ( cept one dude who doesn't have a build together yet ). But i may be moving to the Salt Lake City area so i'll be closer. That's the best i can do ( maybe ) :lol:

A super tall geared motor would be the stuff of dreams, but i don't think it will happen in our lifetimes. Seems like the double wide MAC motor isn't happening soon enough for the hill climb either. Bummer, cuz i'd love to represent MAC.

toolman2: 290w of heat dissipation undrilled is pretty good. Seriously gonna look into a zappy style cooling mod.

 

[auraslip]

Oil cooling will be significantly easier and perform much better. Look at some of the numbers people that have oil cooled their motors are getting. It. Is. Incredible.

 

[o00scorpion00o]

Zombiess,

I don't think you would be happy with the slow speed of the pie in a 20" wheel. It sure has massive low speed torque at 80 amps that I like for the really steep grades in the woods, but they are short. The pie wouldn't take that for too long on those slow steep trails if they were very long. It gets up them so fast though that it has not been a problem for me yet !

I'm thinking for a 20" wheel maybe the cromotor is the best way to go, but a very expensive way if speed on less volts is what you want. As I said before the pie is perfect for most people who want to do 40 mph and are not going to be climbing 16% grades for long. The Pie eats most hills for me.

Neptronix

I agree with auraslip that oil cooling might be a better way to go before you start drilling covers, and it might also appeal to 2nd hand buyers more if it isn't drilled ? I'd try that first.

I would install a temp sensor, without doubt and measure your temps before and after you oil cool it for educational purposes!

But the pie would laugh at a 7% grade especially in a 20" rim !

We can also forget about any kind of pie geared hub, GM are only interested in the normal E-biker, I would settle for a water cooled pie!

 

[auraslip]

If I can't afford a cro-motor for my next build, I might go with a pie rewired to be in delta. Unlimited speed....
And the potential for oil cooling would be tremendous since the covers are so much larger. If my air cooled 9c can handle 3kw continuous, an oil cooled pie could probably do 4kw or 5kw.

 

[neptronix]

A delta 'pie would be fantastic actually, the 20" wheel is just too slow of a wind... i mean, you just can't get enough volts into it in a 20" wheel to go fast at all. 42mph on 30S is pathetic

Oil cooling is an interesting idea, but i don't like the idea of my motor leaking all over the place. I don't know how to properly seal it, so i know that will happen. I will sit out on that idea until someone comes up with a way to keep the pie sealed proper.

 

[auraslip]

hey, did you ever get something worked out with that GM dealer that wanted to part with their pies? I'm looking for one. Maybe even your 20" pie to run in delta.

I just wonder how it effects efficiency and torque to run in delta?

 

[auraslip]

I'm running over budget on a project so now I'm desperate for a inexpensive hub motor.
luckily this oil cooling thing showed up in time!

it looks like geared motors can be ran at 3kw now! so I might go with a mac.

 

[gensem]

I'm running over budget on a project so now I'm desperate for a inexpensive hub motor.
luckily this oil cooling thing showed up in time!

it looks like geared motors can be ran at 3kw now! so I might go with a mac.

You mean that a 500w-1000w geared motor can be runned cotinuosly at 3kw just because it was filled with oil and its using steel gears?

 

[auraslip]

That was the speculation. People are pushing the HT cyltes at 4kw liquid cooled and only getting up to 70c inside.

 

[gensem]

That was the speculation. People are pushing the HT cyltes at 4kw liquid cooled and only getting up to 70c inside.

I see.. how much power do they run on a HT without oil 2.0kw-2.5kw? Wouldn't holes be enough for 4kw on a Hx?

 

[auraslip]

Probably. The question is how hot will it get? 70c is about as hot as you want a motor to get. Beyond that efficiency and power bogs down..... although the relationship between temperature and performance is linear.

 

[gensem]

Probably. The question is how hot will it get? 70c is about as hot as you want a motor to get. Beyond that efficiency and power bogs down..... although the relationship between temperature and performance is linear.

I think the magnets can take a little more, over 80c, but after that you have yourself a major performance hit way before burning the cooper poles. We have 4kw running at 70c now, so lets pretend we have a 15c delta to work with. If Burtie can use 6kw for 10min without going over 85c on the magnets that a sizable improvement over the 4kw that you can do with holes.
Lets wait and see.

 

[neptronix]

I'm running over budget on a project so now I'm desperate for a inexpensive hub motor.
luckily this oil cooling thing showed up in time!

it looks like geared motors can be ran at 3kw now! so I might go with a mac.

3kW peak.. not continuous!
More like 1.5kW continuous.. unless it's a hot day

My MAC handles more power than my MXUS/9C sized motor could, and the bogging down at high temp wasn't very noticeable either on that motor. But the pie really usurps it.

You may get your wish on the pie motors. More on that later.

 

[auraslip]

My MAC handles more power than my MXUS/9C sized motor could, and the bogging down at high temp wasn't very noticeable either on that motor.

Nep, this is pure wishful thinking on your part. I reguralary put 4kw + into my mxus motor for 10 miles straight. Lets see you even get to 4kw with a mac.

 

[neptronix]

Already did 4kW on the MAC, but it was short lived as i didn't want to blow the motor.
My MXUS heated up way quicker on the same power.
( this is all going off external case temps though. )

And you were always complaining about it bogging down. I could run the MAC at 35-38mph power constantly for hours, and never really noticed a drop in power. ( maybe there was one, but it wasn't pronounced enough for me to take notice. )

Don't you have, or had a drilled motor? Not too fair to compare that to a MAC with no cooling mods.
I'm not trying to brag about the MAC, just sayin' that we may not be making a fair comparison.

 

[auraslip]

It's simple math. The mxus weighs twice as much as a mac. The mac isn't all that more efficient than the mxus. All things being equal, the same speed will require the same amount of power from both motors.

The mac doesn't have some magic pixie dust that makes going a certain speed require less power, nor does it run much more efficiently (according to the simulator) on the flats than a mxus.

I know it's performance off the line isn't very impressive, but it is a stronger motor for long, straight stretches. It simply has more copper and thermal mass.

 

[Philistine]

Already did 4kW on the MAC, but it was short lived as i didn't want to blow the motor.
My MXUS heated up way quicker on the same power.
( this is all going off external case temps though. )

And you were always complaining about it bogging down. I could run the MAC at 35-38mph power constantly for hours, and never really noticed a drop in power. ( maybe there was one, but it wasn't pronounced enough for me to take notice. )

Don't you have, or had a drilled motor? Not too fair to compare that to a MAC with no cooling mods.
I'm not trying to brag about the MAC, just sayin' that we may not be making a fair comparison.

Neptronix you can't seriously argue that a Mac/BMC can take more watts continously than a 9c/Mxus. That is just not sustainable as an argument. Loads of people on ES have shredded gears and melted phase wires on BMC/Macs on as little as 48v/50amps (in my opinion that is the maximum you can run them on reliably). Although I have never destroyed my BMC, I have seen many on here do it on the 2-3kw continous level. And I have melted a 9C, and that was from running 20S/40amps into it for half an hour continously WOT towing two toddlers in a trailer and my 95kg ass on a 35c Aussie summer day. I have never heard of anyone melting a 9C at 2-3kw, they will run that day in and day out laughing, but I would never chuck that into my BMC. I would argue that the inability to take high wattage is pretty much the only downside/weakness of the Mac/BMC, but on that score I don't think anyone could argue with the proposition that a BMC/MAC is literally the weakest/most fragile (as in unable to take high current) of all hubmotors (sparrows and other "friend of dorothy" motors aside).

Don't get me wrong, I am a huge fan of BMC/Macs for what they do (ie, great hill climbing and speed on lower volts/current, coupled with extreme lightness), but current handling ablitiy is their achiles heel.

 

[o00scorpion00o]

I was running the mac 8T at 16S LiPo, 60v 57 amps (3500 watts) battery and about 100 phase, Brilliant acceleration!

I never had any problems with heat what so ever. It got hot once climbing a steep hill for about 5 miles on a 50v Ping. Sagged like a old woman, but flew up way faster than the pie on the same voltage and current. The pie could do it no problem, it just needed more voltage, and more watts.

The mac spins faster up hills than the DD motor, the pie was hardly warm and the mac was hot.

Cruising at about 35-40 mph was pulling around 2100-2500 watts. After 10-12 miles full throttle a few slight hills never more than warm.

I killed the clutch, eventually, the keyway wasn't too healthy and kept popping out at the end. Gears are perfect.

My friend Pat who has the mac has never had a problem and runs it at the power it was set to when he got it. He's running my old 50v ping 20ah, he's pulling about 2100 watts max. Still powerful enough and reaches 31 mph max.

I can't wait to have the mac back. I'm waiting on a new clutch and other goodies cell-man is working on, it could be a while yet!

The mac is going to get better!

 

[neptronix]

You're forgetting the 5:1 gear ratio.
Electric motors love high RPMs and efficiency per size climbs massively the faster the motor spins.
Why do you think the little 1-3lb turnigy motors have performance on par with hubs?
When you add the transmission/gear reduction, you lose a lot of the efficiency, but you still have a drastically higher amount of continuous & peak power from a much smaller motor after all things are said and done.

Geared motors are quite a bit more efficient at the lower RPMS ( like when accelerating or hill climbing ), but definitely have lower efficiency when cruising / are closer to the 80% unloaded speed figure. If you live in a hilly area or do lots of stop and go, a geared motor can be far better than a DD in most situations.

p.s. i'd love it if the MXUS weighed twice as much as the MAC motor. I'd have a 7lb MAC motor then . Actually the MAC is 10lbs.

More copper and thermal mass, yes. But i could get the MXUS smoking hot going up a 3% grade on 36v, whereas the MAC would basically just be lukewarm and would have gone up the same hill 15-25% faster, given an equivalent winding, and same controller with same power level... How is that?

Most of my tests are on hilly grounds, nowhere i have lived has been flat since i started this eBike madness. My test results are thusly going to be skewed since the DDs start making crazy heat and get boggy real quick in my environment.

In other words, apples and oranges.

 

[neptronix]

I don't know what to say, mine has been rock solid other than the freewheel cover issue, and when i melted the original white gears after a curb drop, 2 days after i ran 4kW thru it..

35-38mph power on mildly hilly rolling terrain with the occasional whopper of a hill, no prob.

Fragile? sure. All geared motors are. They're designed for the lowest weight possible. DDs just aren't.

Maybe i am lucky, but i never had any of the clutch/hall sensor problems mentioned on the forum. And i totally beat the hell out of my clutch, sometimes intentionally at a 2.6kW burst when i was testing various controllers.

If you need to go more than 40mph constant, the MAC is not for you. Then again, that's quite fast on a bike anyway.

It's nowhere near as fun as the pie. But the pie is heavy, it cogs like crazy, and you need super high volts to run it. While i like high power, i am also a pedalist and the high power per weight & freewheeling of the MAC are what keeps the MAC employed

Neptronix you can't seriously argue that a Mac/BMC can take more watts continously than a 9c/Mxus. That is just not sustainable as an argument. Loads of people on ES have shredded gears and melted phase wires on BMC/Macs on as little as 48v/50amps (in my opinion that is the maximum you can run them on reliably). Although I have never destroyed my BMC, I have seen many on here do it on the 2-3kw continous level. And I have melted a 9C, and that was from running 20S/40amps into it for half an hour continously WOT towing two toddlers in a trailer and my 95kg ass on a 35c Aussie summer day. I have never heard of anyone melting a 9C at 2-3kw, they will run that day in and day out laughing, but I would never chuck that into my BMC. I would argue that the inability to take high wattage is pretty much the only downside/weakness of the Mac/BMC, but on that score I don't think anyone could argue with the proposition that a BMC/MAC is literally the weakest/most fragile (as in unable to take high current) of all hubmotors (sparrows and other "friend of dorothy" motors aside).

Don't get me wrong, I am a huge fan of BMC/Macs for what they do (ie, great hill climbing and speed on lower volts/current, coupled with extreme lightness), but current handling ablitiy is their achiles heel.

 

[auraslip]

except that the only time a geared motor is more efficient is when climbing a hill. Look at the simulator.

 

[o00scorpion00o]

except that the only time a geared motor is more efficient is when climbing a hill. Look at the simulator.

Compared to the pie the mac was more,efficient climbing the same hill as the mac, for the same power. a faster wind dd might have done it as good, I can't say, I can only go by what I've tested.

The pie is a super climber though when fed enough amps, and it's astonishing the grades it will pull me up in the woods.

 

[neptronix]

No disagreement there, guys.

I just remember the 9C/MXUS heating up faster, but doing particularly horrible on hills.


I got back from Utah trikes. Wow! the salesman was a douchebag from the second we walked in. I came all the way from Colorado and part of the trip could have included me taking a trike home, but not from these guys! no greeting at the door, condescending tone, not helpful etc.. the owner seemed cool, but he should definitely not have sales folks like that representing him.

Did however ride various KMXes, a terratrike, and a catrike. Wow, these trikes are very flexy, twitchy, and have the potential to throw you off. I now know why they are not very popular. The catrike was really nice, and had the best road manners, but at $2,500, i'll pass on that offer. The KMX was the worst - had the tires rubbing up against my hands, and the steering was rubbish.

Fun as hell to ride, but they don't feel stable or durable. Back to mountain bikes it is.

 

[auraslip]

That sucks. It's a rare bike store that isn't filed with douche bags.
Although, I can't imagine your GF would be happy with a trike in your living room.