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

Changing the operating point does change things. Clearly the motor can be overheated by going too slow, and totally destroyed by applying too much power. So in between there must be a speed which minimizes net heating. Finding that speed is the difficulty, and then you need enough voltage and current to achieve that speed. Even at this optimal speed the motor may or may not melt before reaching the top.

It would be interesting if we could equip the bike with enough instrumentation to immediately read out the power input to the motor (easy) and the power output (not easy). Then we could immediately tell if this is sustainable (providing we already had some data for dissipation). Measuring motor temperature is an easier way to tell, but the data rate is very low so it might take many runs to determine the optimal speed. Essentially if the motor temperature is rising above some level then it is probably not sustainable for a long climb.
 
What we need is water cooled motors, but I think that will be a long time.....if ever!

Even water cooling looses efficiency because of the pumping of coolant, it would save the motor for sure but wouldn't that still mean inefficiency, because heat means inefficiency, so water cooling only transfers the heat to the coolant? meaning transferring the inefficiency from the motor to the coolant ?

I got sooooo much to learn about motors!
 
Operating the motor at lower temperatures improves efficiency by reducing copper losses.

Let's say the motor is 75% efficient and is doing 1500W of work climbing the hill, so we are putting in 2000W and it is dissipating 500W. If this is a gearmotor that can only dissipate 400W it will heat up and melt.

If we put in liquid cooling and bring that 500W of heat out of the motor into a radiator we can avoid melting the motor.

So cooling helps efficiency and allows survival.

I guess we don't want to put holes in a gearmotor for cooling, but holes in a DD motor can help. Perhaps even misting in some cooling water would be worthwhile. They hand out water on the way up Pike's Peak during the race, wonder if they would mind if you wanted a couple extra bottles. Then you wouldn't have to carry all that water from the bottom. :D
 
Alan B said:
It would be interesting if we could equip the bike with enough instrumentation to immediately read out the power input to the motor (easy) and the power output (not easy). Then we could immediately tell if this sustainable (providing we already had some data for dissipation). Measuring motor temperature is an easier way to tell, but the data rate is very low so it might take many runs to determine the optimal speed. Essentially if the motor temperature is rising above some level then it is probably not sustainable for a long climb.
Click to expand...

I was just thinking about that today on my walk. I need a temp sensor, for sure.
BBQ thermometer with an extended wire up to the handlebars

Or can someone suggest a more elegant solution?

Also, it is highly likely that the covers will be drilled.
A misting system is a good idea. I could hide the tank in the rear topeak rack. Only have to fit 25AH/12S into the rear.. i could fit a few computer duster sized cans of something in there.
 
What size are your phase wires Nep? Did you upgrade them? The ones on my older Mac look really thin, maybe 16ga. Do you know what battery current is the limit for those? (I think phase currents will vary depending on winding and hub speed too though).
 
veloman said:
What size are your phase wires Nep? Did you upgrade them? The ones on my older Mac look really thin, maybe 16ga. Do you know what battery current is the limit for those? (I think phase currents will vary depending on winding and hub speed too though).
Click to expand...

Yup, they're upgraded on the pie. 12 gauge, and half the stock length. However, it's graded after the axle, not inside.

The stockers were definitely 16ga.
On my MAC, they were more like 14-15ga. and upgrading them to dual 14ga. didn't help too much.

Not sure about your other q..
 
GOT GOOD NEWS...

Battery: 20S/5AH charged to 81v.
Hill: 0.32 mile, 8.6% grade average, ~12% peak grade.
Conditions: 37 deg F. & no wind

Speed at the start of the hill ( ~3% grade ): 28mph.
Lowest speed at 12%: 25mph

Cruising speed: 30mph, at 120%, 33mph.

So yeah, i dropped an entire 3mph at the worst part of the hill. The motor was cold to the touch even after ripping around the street a few times in utter childlike glee at the 120% setting.

This motor is the real deal, boys.... I may actually have to dial down the amps because it has this nasty habit of wanting to throw you off. I doubt it is using the max 56 amps at all as the 5AH of year old turnigy 20C would have gotten hot at anything over ~33A for very long.

I do not have a cycle analyst to measure the amps/watts/etc just yet. I have one currently en-route from methods.
More later, including video once it stops snowing.
 
Here is a pic of it so far.

peakpower.jpg


( no, my window is not busted out. That's just window wrap since we live in a drafty ol' house.. :lol: )

Needs the following things:

1) Shorter suspension fork, OR a 20in. wheel in front to improve the angle of the bike for better aero.
2) Thinking about an aero fairing. A couple mph would help here.
3) Enable regen.. i have no back brake right now. Waiting on cable from cell_man.
4) Another 12S / 25AH array on top of my
5) Rear rack for the addl. ~16lbs of 12S/25AH ( 10 packs ).
6) External controller mounting to make room in the falconEV bag.
7) Depending on how the next tests go, vented hub covers, internal temp sensor and a cooling system i've been dreaming up for a while..
8) Dial the amps down from about 56A to maybe 50A. We'll see what the cycle analyst reports. Hopefully they can be dialed down a little to prevent a LiveForPhysics-hands-the-bike-to-a-newb type of situation.
9) shorter crank arms as these 165mm ones have about 3 in. of clearance from the ground.

Lastly, thank you all for cheering me on. I had no effing clue that a DD hub motor could have performance like this at all. I am still shocked at how little mph it dropped on the hill. And i am ebike grinning from ear to ear still :mrgreen:
 
Alan B said:
Good job.

You might set the phase amps lower while keeping the battery amps up, that would not affect top speed but would reduce the kick from zero and the heating that it causes.

If you lower the front are you going to be able to pedal?
Click to expand...

Thanks for the phase amp tip.. i will experiment with it once i get the programming cable in from cell_man.

I updated the list.. added 9) ..
Yeah, i've got 3 inches of clearance with the pedals O_O.. I will check my local bike shops to see if i can get something smaller than my 165mm pedals.

Will hit up the used bike store on monday.
 
neptronix said:
GOT GOOD NEWS...

Battery: 20S/5AH charged to 81v.
Hill: 0.32 mile, 8.6% grade average, ~12% peak grade.
Conditions: 37 deg F. & no wind

Speed at the start of the hill ( ~3% grade ): 28mph.
Lowest speed at 12%: 25mph

Cruising speed: 30mph, at 120%, 33mph.

So yeah, i dropped an entire 3mph at the worst part of the hill. The motor was cold to the touch even after ripping around the street a few times in utter childlike glee at the 120% setting.

This motor is the real deal, boys.... I may actually have to dial down the amps because it has this nasty habit of wanting to throw you off. I doubt it is using the max 56 amps at all as the 5AH of year old turnigy 20C would have gotten hot at anything over ~33A for very long.

I do not have a cycle analyst to measure the amps/watts/etc just yet. I have one currently en-route from methods.
More later, including video once it stops snowing.
Click to expand...


Brilliant, See I told you the Pie was a monster hill eater didn't I ? :mrgreen:

So going from 26" to 20" really makes a major difference to the load on the motor, that's really cool!

It would be interesting to see how hot it would be on a longer climb, so it did 25 on 12% so it should do 20 on the 16% I went up, but the main thing is it shouldn't get too hot!

33 mph is not too shabby, but on 80 volts it's a lot of battery to carry around, but that was just with 5ah right? I was getting 33-35 mph max on 60 volts in a 26" wheel with 120% setting.

You would need about 100 volts to get to about 40 mph, but shit that would be scary with so much torque, on the + side though you could reduce the current even further if you wanted. 100 volts 10ah would be 1000 w/hrs for about 15 ish miles at 35-40 mph, not bad at about 55 ish whr/mi. That's the same wh/mi as a 50 volt 20ah pack for the same range, or more considering you would be going slower! I think you are into electric shock territory there ? maybe nothing serious just a little bite ?

It would have been better if GM had to make a faster wind for the smaller diameter wheels, I think the pie is too slow a wind, it has so much torque to start with it didn't need such a slow wind, but since they designed it to work with smaller batteries they wanted to maximise the amount of torque for the batteries and controllers they sell. They are not interested in making fast bicycle motors!

I would like to see how the HS3540 performs in a 20" wheel at the same 80 volts. According to the ebikes.ca simulator the HS3540 will go up a 12% grade at 24.9 mph, 50 amp controller, overheat after 5.8 mins. 115 lbs of torque. Strangely enough in a 16" wheel it says it will go up at 26 mph with 140 lbs of torque. That would nearly pull the bike apart!!!

So why does it say it will go up slightly faster in a 16", is it because of the extra torque ?

The new Volkswagen Golf 1.2tsi turbo petrol manual 122hp has 144 lb/ft and the HS3540 has 140 lbs in a 16" wheel, holy shit that would out accelerate it something crazy, to about 20 mph lol still, that's some power!



Dave I say to hell and go 100 volts, if you can afford to spend more on a new controller that is, I don't think the 4110's would take that?

2 x 20" wheels and you will be a lot lower, less wind resistance and it would be a lot steadier. Now if you only had a full suspension bike!
 
Re: crank length, you can get 150mm ones (BMX) - might give you some more ground clearance.
 
scorpion; you are the one who helped this build happen majorly. Nobody else spoke so highly of the magic pie even though Luke kept recommending it etc.. I would have forgone this motor if it wasn't for your tests.

Your pie wind is definitely a faster one than mine. Like i said, i hit about 30mph on 5ah of 20S, but that's at a full charge, it goes 27mph on the nominal voltage ( 3.85v ), so that's what i have to plan around..

22S will get me a mph or two, that's it.. Mind you, 22S is 92.4V fully charged, that's about as close to 100V as i want to get since the limit of the components in my 12FET is 100v - cutting it close there..

By the way, comparing car torque to bike wheel torque is a bit complicated because of the gearing & final drive of a car. Even an electric car is going to have a final drive / gear reduction, so the torque will be more or less what the motor is outputting.

But yes, this thing feels like a V8 or V12 taking off. I really want to dyno it.
 
Note: i finally got the Cycle Analyst in the mail today so i'm ready to collect some data :)..

But life has came between me and my build lately. I've been revamping a decade-old SQL design at work and it's been giving me fits all week so i've not had as much time to focus on the important things in life ( ebikes ).

I noticed that gearing for the pedaling is going to be a severe problem on the 20in. wheel. I need to be pedaling around 25mph to keep the speed up & battery draw / motor heat low on the really nasty sections of the hill. The motor wants a 6 speed freewheel, as a 7 speed would rub on the frame.

The lowest gear available on a 6 speed freewheel is about 14T, and that's a major, major problem..

I hope that i can find a 56-60T front chainring somewhere O_O..

I may have the axle machined.. or insert some spacers on the freewheel side and bend the frame a tad.. not sure which way to go yet.

Heath: i will check that out. 150mm would probably be perfect.
 
I'm looking to replace my brushed 20" hub motor with a brushless , on 48 volt . quick and efficient to 25 mph.

Is the magic pie the best choice ?
 
jmygann said:
I'm looking to replace my brushed 20" hub motor with a brushless , on 48 volt . quick and efficient to 25 mph.

Is the magic pie the best choice ?
Click to expand...

Quick, yes.
Efficient, probably not.

It will need about 66V nominal to do 25mph.

If you want quick AND efficient.. i'd point you in the direction of a MAC/BMC motor in a 20" wheel.. on the MAC side, an 8T would be really quick on 48V as long as you feed it the amps it needs on that motor / wheel size ( ~30A )

PM me if you have more questions about your own build though, i'd lke to keep this thread un-cluttered and on topic as much as possible :)
 
Another option for a compact 11 tooth freewheel 5 speed (11T 6 speed may be an option too) is make one like Dr Bass did with epoxy.....this is really slick....


http://endless-sphere.com/forums/viewtopic.php?f=2&t=27108&hilit=freewheel
 
My 9x7 9C motor gives me 37-42mph (20s LiPo) on flat road. I assume your magic pie is high torque type motor similar 9C 6x10 or HT35 motor?

Is it because Luke recommend you get this Magic Pie due larger stator therefore more cooling due heat soak into larger stator? Mac 8T is very nice as long as you keep maintain 1500 watts. You will be fine long endurance run without tear up the gear box. ilia brouk (BMC guy in SF), He abused his BMC geared motors hardly break the gearbox and I have see his action. His wheel spin like MAD! :lol:

I was gonna get MAC 8T for my Genesis V2100 with extended swing arm and I realized MAC geared hub motor is limited at 1500 watt for longevity last long without break the gearbox. I am in middle of the fence between RC motor setup using recumpence's V4 motor kit or Dual cyclone 1200 watts or stick with Direct Drive motor. arggh hard make a decision. :lol:

Please make more vids action and I would love see how the magic pie handle the hilly (10% grade avg). Does your MAC 8T broke down yet? I mean are you not happy with the MAC motor?

neptronix said:
Your pie wind is definitely a faster one than mine. Like i said, i hit about 30mph on 5ah of 20S, but that's at a full charge, it goes 27mph on the nominal voltage ( 3.85v ), so that's what i have to plan around..
Click to expand...
 
o00scorpion00o said:
neptronix said:
GOT GOOD NEWS...

Battery: 20S/5AH charged to 81v.
Hill: 0.32 mile, 8.6% grade average, ~12% peak grade.
Conditions: 37 deg F. & no wind

Speed at the start of the hill ( ~3% grade ): 28mph.
Lowest speed at 12%: 25mph

Cruising speed: 30mph, at 120%, 33mph.

So yeah, i dropped an entire 3mph at the worst part of the hill. The motor was cold to the touch even after ripping around the street a few times in utter childlike glee at the 120% setting.

This motor is the real deal, boys.... I may actually have to dial down the amps because it has this nasty habit of wanting to throw you off. I doubt it is using the max 56 amps at all as the 5AH of year old turnigy 20C would have gotten hot at anything over ~33A for very long.

I do not have a cycle analyst to measure the amps/watts/etc just yet. I have one currently en-route from methods.
More later, including video once it stops snowing.
Click to expand...


Brilliant, See I told you the Pie was a monster hill eater didn't I ? :mrgreen:

So going from 26" to 20" really makes a major difference to the load on the motor, that's really cool!

It would be interesting to see how hot it would be on a longer climb, so it did 25 on 12% so it should do 20 on the 16% I went up, but the main thing is it shouldn't get too hot!

33 mph is not too shabby, but on 80 volts it's a lot of battery to carry around, but that was just with 5ah right? I was getting 33-35 mph max on 60 volts in a 26" wheel with 120% setting.

You would need about 100 volts to get to about 40 mph, but shit that would be scary with so much torque, on the + side though you could reduce the current even further if you wanted. 100 volts 10ah would be 1000 w/hrs for about 15 ish miles at 35-40 mph, not bad at about 55 ish whr/mi. That's the same wh/mi as a 50 volt 20ah pack for the same range, or more considering you would be going slower! I think you are into electric shock territory there ? maybe nothing serious just a little bite ?

It would have been better if GM had to make a faster wind for the smaller diameter wheels, I think the pie is too slow a wind, it has so much torque to start with it didn't need such a slow wind, but since they designed it to work with smaller batteries they wanted to maximise the amount of torque for the batteries and controllers they sell. They are not interested in making fast bicycle motors!

I would like to see how the HS3540 performs in a 20" wheel at the same 80 volts. According to the ebikes.ca simulator the HS3540 will go up a 12% grade at 24.9 mph, 50 amp controller, overheat after 5.8 mins. 115 lbs of torque. Strangely enough in a 16" wheel it says it will go up at 26 mph with 140 lbs of torque. That would nearly pull the bike apart!!!

So why does it say it will go up slightly faster in a 16", is it because of the extra torque ?

The new Volkswagen Golf 1.2tsi turbo petrol manual 122hp has 144 lb/ft and the HS3540 has 140 lbs in a 16" wheel, holy shit that would out accelerate it something crazy, to about 20 mph lol still, that's some power!



Dave I say to hell and go 100 volts, if you can afford to spend more on a new controller that is, I don't think the 4110's would take that?

2 x 20" wheels and you will be a lot lower, less wind resistance and it would be a lot steadier. Now if you only had a full suspension bike!
Click to expand...

That's my plan. :mrgreen:
http://www.endless-sphere.com/forums/viewtopic.php?f=6&t=34672
Though this thread has me considering 20" Pie on 30s2p lipo. :twisted:
I've got the room :wink:

keep up the good work Nep.

Let's get a moto/moped tire on there.
 
OK, i just got done riding it around. Nearly flipped myself on my back at a stoplight when i first hit the throttle, luckily i kinda fell over to the side.. made a total ass of myself next to the people behind / to the side of me LOL..

It's really hard to control this bike from a stop. Below 1/2 it's top speed, you have to lean on the front end and tense up otherwise you get thrown off. I am 230lbs so i can just imagine what would happen to a lighter rider.

I finally got my 10AH pack (rather than 5AH ) set up; i must be getting notably lower voltage sag since my top speed at full charge went from 30mph to 32mph :)... and 120% is now hitting 35mph.
I may gain a MPH or two when i have my full 22S/30AH.

I'm sure the speed at nominal voltage ( ~3.85v/cell ) ( ~27mph ) on 100% has gone up to about ~28mph.

I proceeded to do about 5 mi. of 3%-5% hill climbing at 120%.. the motor was just barely warm after this to my amazement.
Beat some motorcycles on some city streets, which ended up with equal amounts of hostility and 'woah what the hell is that'? kind of questions..

I promise i will get some data later on, just waiting for some help from methods to get the CA calibrated. I also need to make a pre-charge resistor since 72V will produce a hell of a spark.
 
chroot: i would assume it is more like a 9x10, yes indeed, very high torque, low speed wind.

Yes, i bought this on luke's recommendation after some relenting. Then oooscorpionooo told me that his motor survived a 16% hill climb.

I have not installed a temp sensor yet - just going off the cover temps.. but this thing cools off very fast, and where my MXUS/9C style 9x7 in a 26" wheel on 57v would be struggling and getting hot enough to cook an egg on, this thing gets just barely warm and cools off in short time.

I think the secret sauce is the giant aluminum rim bolted to the hub - it's a gigantic heatsink.

A MAC 8T in a 20" wheel would probably be pretty damn fast, i found mine in a 26" to be quick enough for my needs on ~2300w - fast enough to beat most cars from a stoplight, climb up steep hills, etc. You might not want to rule it out as an option. Mine had a long life at 2300w average use until i dumped 4kW into it and hit some curbs which killed the original white gears.
My MAC is still dead, i am only waiting on grease for the new gray gears, that is all. It's a great commuter motor with a great power to weight ratio, and i will be riding it as my main bike when it is back together.


Brentis: I cannot even imagine what 30S is like on this motor. I agree that a better tire is needed. A 20" tire just happens to baloon outwards towards the v-brake mounting points here, so 2.3" wide is the limit unless i grind those off.. but i'm thinking extended BMX frame would be the way to go.
 
Damn 9x10?! That's better than 9x7. Should I order Magic Pie III without internal controller instead using my Lyen controller and What should I expect the speed if I am running 20s4p (20Ah)? I am building my Genesis bike with farfie's extended swing arm and I read the link you referred to Luke's recommendation and I see that Luke mentioned about the RC setup isn't great for climb uphills unless wanting zip around the town (I assume meaning flat road).

I thought you bought MAC 8T from Cell_Man was using the gray gearbox and You mentioned white gearbox (Kinda confused). Dang that sucks for your MAC destroyed your white gearbox. What's big difference between BMC green gearbox and gray gearbox. Are they strongest component similars?

Lastly question, What about the CroMotor and Have you thought try it out use'em? I still waiting for the videos review on CroMotor.

Thanks for the answers. I appreciated it

neptronix said:
chroot: i would assume it is more like a 9x10, yes indeed, very high torque, low speed wind.
Click to expand...
 
The 9x10 is not better, it's just a different wind.. keep that in mind :)
The Magic pie III isn't being sold as an external unit.. you have to get the magic pie 2 for now.

I ordered my MAC about a year ago and it came with the old white gears before the motor got various upgrades. I was told that they were good for about 2000w, i pushed them to about 2300w for many months and it took >4000w to kill them, so they definitely exceeded my expectations :)

There is a definite lack of info and real life tests on the cro motor.. shipped to the USA though, it's been said that it cost about $700, whereas this pie was about $180. I only need to go 1-5mph average faster than optibike and the pie will do it, so i wasn't too interested in going overboard. Besides, my heart is in the geared motors and i'm holding out my cash for the BIG MAC dual stator motor that cell_man has been teasing us with.


Anyway i just spent $622 on 30AH of 12S lipos and my wallet is hurtin.. let's not talk about money for a while.. :lol:
 
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