Doing the Math

[Kingfish]

Thanks Biff on the epoxies; we should check into thermal curing as I think that is the way of the industry.

Gosh Arlo, I would think 80 km/h (50 mph) is plenty fast for a bicycle and more-or-less my target for P1 as a 2WD – and I think I can get there with an over-volted Plan-D 3-Rotor/2-Stator build. That 198 km/h (123 mph) mark is impressive though. We need to find the fastest e-cycle record, and then build a special motor just for burying it. But hey – that’s a down the road a ways: We have lots of time to dream!

However - I would perish the thought of using Mercury for cooling. I don’t even want to touch the stuff, let alone breathe it: Not practical for a lot of reasons.

If you are serious about liquid metal, I’d review the Wikipedia topic. My suggestion is NaK because at least it won’t poison you. But then you wouldn’t want to expose it to air or water either.

Might I suggest a very safe alternative is Mineral Oil: Dielectric, non-compressible, lubricating, and has nice thermal-bearing characteristics exceeding 200° C.

Or, maybe there is a biodegradable equivalent out there; wouldn’t that be peachy! Stop for a burger and charge, top off with a little Canola and away you go.

What a wonderful spin of ideas; most fun!
Cheers, KF

[Arlo1]

Thanks Biff on the epoxies; we should check into thermal curing as I think that is the way of the industry.

Gosh Arlo, I would think 80 km/h (50 mph) is plenty fast for a bicycle and more-or-less my target for P1 as a 2WD – and I think I can get there with an over-volted Plan-D 3-Rotor/2-Stator build. That 198 km/h (123 mph) mark is impressive though. We need to find the fastest e-cycle record, and then build a special motor just for burying it. But hey – that’s a down the road a ways: We have lots of time to dream!

However - I would perish the thought of using Mercury for cooling. I don’t even want to touch the stuff, let alone breathe it: Not practical for a lot of reasons.

If you are serious about liquid metal, I’d review the Wikipedia topic. My suggestion is NaK because at least it won’t poison you. But then you wouldn’t want to expose it to air or water either.

Might I suggest a very safe alternative is Mineral Oil: Dielectric, non-compressible, lubricating, and has nice thermal-bearing characteristics exceeding 200° C.

Or, maybe there is a biodegradable equivalent out there; wouldn’t that be peachy! Stop for a burger and charge, top off with a little Canola and away you go.

What a wonderful spin of ideas; most fun!
Cheers, KF

At this point the liquid wonding is just a thought! Simplicity of the build its the most important! And as I think about it the better you build it the more effiecient it is and the less heat you need to get rid of!
And the Hyabusa toped out at 198 MPH (316km/h) for that year!

[Kingfish]

And the Hyabusa toped out at 198 MPH (316km/h) for that year!

Good gawd man! Did you wear a chute?

Well to get to 200 mph we'd need to consider some serious aero to reduce current. I say let's make a plan for Bonneville! <nods>

TEAM ES of World League. Yeah, I can noodle up some ideas for cooling on that scale.

BTW – I have to ask since it appears that the space inside the hub is going at a premium: I was planning on leaving this design as Star/Wye and not Delta because of the voltage issues. Certainly there should be enough starting torque for Delta, I just don’t think we need it. Point: My preset hub design for 2-Rotor/1-Stator would have ample room for switches. However if we start talking about multi-stator & cooling that would be the first feature I’d ditch: Gimme freedom to design.

Thoughts? KF

[Arlo1]

Certainly there should be enough starting torque for Delta,
Thoughts? KF

OK so.... The torque is the same for WYE and Delta
I guess the easiest way to explain it is to solve for torque you convert watts to HP then use the rpm to solve for torque (as long as you are still in the usable rpm of the motor)!
I have had to sit and watch luke explain this to 20 or more people! And Luke it so smart he forgets to dumb it down for them! You are a very smart guy so I am sure you will understand but I decided to find a simple way to explain it!
I have to educate a lot of people with my trade so I find easy ways to help them understand like when explaining the relationship between Torque and HP I just say they are the same except HP has time added to the equation!
Hope this helps,

I am interested in building this for the Drag bike I want to make as well!

[BrushlessinSeattle]

Hey KF,
I was wondering about your choice of bar magnets. It seems like there would be a lot of flux leakage from magnet to magnet near the ID where the magnets are almost touching. Nearer the OD you have large gaps between the magnets - torque and efficiency will be negatively impacted. I know you're not keen about wedge magnets because the pole count of off the shelf wedges is only 16 and that would result in a motor which runs too fast. This is where my understanding starts to get a bit fuzzy, but cant you just run the controller at a lower frequency? Would this affect efficiency?
-BiS

[Kingfish]

Brushless, controller frequency not the issue: It’s about gearing my friend.

Imagine you are trying to climb a hill; lower gearing makes it easier. It’s the same with magnetic poles – simplistically, the more pole-pairs that you add the less power it takes to rotate the wheel. The typical windmill magnets are pre-designed for a certain speed and that is a bit fast for us hub guys. Example: The 9C hubs actually have 46 magnets/23:1 gearing. The Plan-D option I am considering uses 32 magnets/16:1 which I believe is ½ speed of the windmill, but obviously faster than the stock 9C ...which is what I want.

Now, to do the calculation properly you need to presume you want the windmill size and that you can live with the lower-starting torque by providing a proportional amount more power. Don’t worry about the controller frequency. Just run through the calculations. Your windings will be larger, or perhaps you may opt to have more winding sets per phase.

Are you considering the ¼-inch or the ½-inch thick? Do you want me to do this calc with you so you can visualize the difference? I Personally think it would be a valid exercise, and fitting for the NHA AF section of this thread. If so then I need some specs from you:

• What is the desired target speed for your ebike that you require?
• What is the size of the target wheel?
• Do you know how much power you want to use at the target speed? Example: I set my model to use 2 hp @ 30 mph with a 26-inch diameter wheel.
• What is the target Battery Voltage or Current? (Pick one or the other)
• Can you send me a link the specific magnets that you have in mind so that I have the specifications please?

Happy to Help, your Eastside buddy KF

[BrushlessinSeattle]

Thanks for the explanation KF, I like the gearing analogy. I'm still confused though. I've been approaching the problem from a Lorentz equation point of view ie for a given amperage the torque achievable by a motor at low rpms is proportional to the length of wire and the density of the flux that the wire is immersed in. Now assuming, for the sake of argument, that the 16 and the 32 pole models have the same radius, magnet area, flux density etc, we could immerse just as much wire in the 16 pole version as the 32 pole version. There would be half the number of coils in the 16 poler each consisting of twice as many turns but since the magnets are wider the coils can be wider too, and our stator width/airgap stays the same. Am I visualizing this incorrectly?...entirely possible. With an ironless stator cogging would not be an issue. When it comes to length of coil end turns....you got me there, they would be longer with the 16 pole version.
Your insights would be much appreciated. Once I get my head around this I can move on to other considerations - target voltage, mph etc
-BiS

[Kingfish]

Brushless,

On the face of it – that sounds like a good direction for theorizing. A practical approach though would avoid the presumptions and start from scratch. You wish to design around what the magnets can do for you, yes?

Define the model: Walk through the calculations until you have a concrete answer. Change ONE parameter and recalculate. Compare and contrast. Repeat until you understand the limits of the model.

Avoiding the rotational frequency differences, I am not convinced that a NHA 16-pole windmill magnet will perform the same as a 32-pole with exactly the same physical features sans width/arc-length. With a NHA you also have to account for air gap between the same-plane magnets, and I think that decreasing the number of poles would affect field strength in a non-linear manner.

Consider: I started with 20 poles (Plan-A) thinking it would do, but then had to step back from that after three iterations because I was not satisfied with the resultants. If you want to see a detailed study using the windmill magnets I suggest reading up on Shane Colton’s work.

Best, KF

[BrushlessinSeattle]

KF,
Thanks for the Shane Colton link, that's some really relevant stuff. I was a bit disappointed when I saw the table on pg 45 which compares Kt for the 3 motors. It shows the axial coming in a distant 3rd, but I punched the tabulated numbers into the equation and got a much more impressive 0.71Nm/A for the axial. Hard to believe he would miscalculate that one .......maybe I did (although I did it twice)
-Bis

[Kingfish]

BiS, that’s why I also model with FEMM, and why you’ve seen me produce so many iterations. It’s all about doing the diligence of discovery, and it takes time. The happy part of the story is that you are spending that time learning as oppose to burning through money on less-optimum paths.

The path of your discovery will be different than mine. Where ours cross and perhaps run together is where we can collaborate. As the song says… “because two heads are better than one!” ♪ ♪

Now I’m Sleepless, KF

[Arlo1]

Brushless, controller frequency not the issue: It’s about gearing my friend.

Imagine you are trying to climb a hill; lower gearing makes it easier. It’s the same with magnetic poles – simplistically, the more pole-pairs that you add the less power it takes to rotate the wheel. The typical windmill magnets are pre-designed for a certain speed and that is a bit fast for us hub guys. Example: The 9C hubs actually have 46 magnets/23:1 gearing. The Plan-D option I am considering uses 32 magnets/16:1 which I believe is ½ speed of the windmill, but obviously faster than the stock 9C ...which is what I want.

Now, to do the calculation properly you need to presume you want the windmill size and that you can live with the lower-starting torque by providing a proportional amount more power. Don’t worry about the controller frequency. Just run through the calculations. Your windings will be larger, or perhaps you may opt to have more winding sets per phase.

Are you considering the ¼-inch or the ½-inch thick? Do you want me to do this calc with you so you can visualize the difference? I Personally think it would be a valid exercise, and fitting for the NHA AF section of this thread. If so then I need some specs from you:

• What is the desired target speed for your ebike that you require?
• What is the size of the target wheel?
• Do you know how much power you want to use at the target speed? Example: I set my model to use 2 hp @ 30 mph with a 26-inch diameter wheel.
• What is the target Battery Voltage or Current? (Pick one or the other)
• Can you send me a link the specific magnets that you have in mind so that I have the specifications please?

Happy to Help, your Eastside buddy KF

But the number of polls does not effect torque! It might effect efficiency but not torque. Now you must read the Wye Delta thread to see the tests. I belive it is because we are limited by the amps the batteries can produce!
To find torque you need to know total volts x total apms and rpm and efficiency! Nothing else number of polls might help efficiency and keep you further away from stator tooth saturation but thats it.

[Kingfish]

But the number of polls does not effect torque! It might effect efficiency but not torque. Now you must read the Wye Delta thread to see the tests. I belive it is because we are limited by the amps the batteries can produce!
To find torque you need to know total volts x total apms and rpm and efficiency! Nothing else number of polls might help efficiency and keep you further away from stator tooth saturation but thats it.

That's a very big IT in the final equation

Torque being the same, would you want a 2-pole, 12-pole, 22-pole, or 32-pole rotor? There's a valid reason why certain motors work with particular pole counts.

I ask you: What is the RPM of the 16-pole windmill-magnet motor in Shane's endeavor? Did he use external gearing? What was the tire size? For what they were making, even with the little skateboard motor - the relationship between the pole-count and rpm made sense. That's all I am saying.

It's Friday; let's play! For examining pole and stator relationships, here's a niftly little winding calculator to play with. The 9C-280X uses 51 Teeth and 46 poles. The scheme is complicated: I wonder if they are using phase groups? Anyone have the numbers for the Crystalyte 4- & 5XXX?

~KF

[Arlo1]

But the number of polls does not effect torque! It might effect efficiency but not torque. Now you must read the Wye Delta thread to see the tests. I belive it is because we are limited by the amps the batteries can produce!
To find torque you need to know total volts x total apms and rpm and efficiency! Nothing else number of polls might help efficiency and keep you further away from stator tooth saturation but thats it.

That's a very big IT in the final equation

Torque being the same, would you want a 2-pole, 12-pole, 22-pole, or 32-pole rotor? There's a valid reason why certain motors work with particular pole counts.

I ask you: What is the RPM of the 16-pole windmill-magnet motor in Shane's endeavor? Did he use external gearing? What was the tire size? For what they were making, even with the little skateboard motor - the relationship between the pole-count and rpm made sense. That's all I am saying.

It's Friday; let's play! For examining pole and stator relationships, here's a niftly little winding calculator to play with. The 9C-280X uses 51 Teeth and 46 poles. The scheme is complicated: I wonder if they are using phase groups? Anyone have the numbers for the Crystalyte 4- & 5XXX?

~KF

There is lots of valid reasons to use a certain number of stator teath and magnet polls. The big one is efficiency and tooth saturation magnet pull force ect. Luke Has the numbers memorized for the X5 hub motors. I have the x5304 which I think is 28 strands of 4 turns per stator tooth! I will have to go find where luke posted it.
I am not trying to be an ass Kingfish you are a very cool guy to lern from but luke pointed this out a while ago. And once I got a grasp on the concept then I realized that I need to think long and hard about the power and weight I need from the motor I build for the electric drag bike!

[Kingfish]

I am not trying to be an ass Kingfish you are a very cool guy to lern from but luke pointed this out a while ago.

Y-ya mean I’m not as cool as Luke? <sniffle>

...I need from the motor I build for the electric drag bike!

Well then, perhaps the windmill magnets are for you because the rpm is about 3000 which is twice what I need for my planz.

Let's do the Math:
From Page 1 of this thread…

24-inch tire = 2 foot diameter (d).
Circumference of 2-foot tire = π d -> π * 2 = 6.283 feet (per revolution)
If 1 mile = 5280 feet, 30 miles = 30 * 5280 = 158400 feet.
With 1 hour = 60 minutes, rpm = (158400 feet / 6.283 feet) / 60 = 420.2 or 7.003 rps using 2 hp.

• Current motorcycle land speed record = 376.363 mph / 605.697 kmh set on 25 September 2010 at Bonneville using a 2,600 cc (160 cu in) engine.
• BTW – the record for an electric motorcycle is about 176 mph; this is a fluid development and there is some contention; I don’t have all the details.
• To equal the motorcycle land speed record, the correction factor = 376.363 / 30 mph = 12.5455 (rounded up); my 24-inch tire would have to spin 87.86 rps or 5271.3 rpm using at least 25 hp / 18.71 kw (no losses).
• To equal the electric motorcycle land speed record, the correction factor is 176 / 30 = 5.87 -> 41.1 rps or 2465 rpm @ 11.73 hp / 8.75 kw.

Plan-D will not work for these applications, however – in the book Axial Flux Permanent Magnet Brushless Machines on Page 184 Example 5.1 provide a 5-page solution to a 3000 rpm coreless AF motor using 2 rotors at 6 poles each, 6 mm high, with an output of 5.6 kw at 75°C. The solution is not published online. This design is close to what you need and can be adapted to suit.

Or, you can adapt Shane Colton’s AF machine to work; it does 3,000 rpm on 16-pole/2-rotor ¼-inch tall windmill magnets, though the output is less. My honest suggestion is to use this design, throw in another rotor/stator, then make it a 2WD; split the load between the wheels to keep the heat down. I mean this is going to be water- or glycol-cooled anyway and the motorcycle axle is big enough to run pipe through it.

Bottom line:
Can we design a motor that can meet/exceed the electric motorcycle record? You betcha we can! If I win the Washington Lotto tomorrow we could get started right away Quit your day-job; let’s do it!

I think though that the motorcycle land speed record would be far more challenging. Might need to go to a different topology rather than a hub motor; find out what other people have been doing.

Scribblin' down my lotto numbers, KF

[Arlo1]

Sorry Im talking about a geared motor that will use a chain to the rear wheel all though a hub motor would be cool and I am talking ~750 kw! This is to build a 6 second drag bike. To compeat against the Nitro drag bikes! The one I work on a little bit and the boss is crew cheaif for won Canada this year and turned a 6.28 in vegas last weekend with the Front wheel in the air till 40' after the finish line! 2wd is not an option!
But there is lots of room for a big DIA multi layered AF motor to keep the heat down and it is likely I will just make it Air cooled to keep everything as light as possible! Its only ~10 seconds of run time per run 3 second burn out and 6-7 second run! Just has to be efficient to make it stay cool!
Bottom line Is with the right help and a bunch of money I will build a bike that can blow the doors off the Nitro guys!
As for how cool you are Kingfish well.... We havent met yet

[Kingfish]

Wow, drag bike – I get it now.

Too bad we couldn’t use sacrificial parts; swap out between runs for rehabilitation. What is your tire size and width, rim? I’d still like to consider a hub solution just for fun. What about shaft drive, or is that too heavy? Or Twin-shaft - one on each side: two multi-rotor AF motors turning CW/CCW to cancel out torque and throw the bike to the ground. Big fat meats on the rear. Yeah the picture is becoming clear. Are you thinking nanotech batteries? Can you send a picture/specs of a typical bike (maybe needs to be a new thread so we can track it separate). Very exciting!

Maybe I better buy more lotto tickets…

Vrooom, vrooom! KF
oh wait - that's "Mhahaha, Mhahaha!" <rub hands>

[Arlo1]

No shafts. The motor will have to turn the same direction as the wheel. Chains are the most efficient as of now so what ever we can do to keep the efficiency up then we need less power and less everything!
Hub motors are a cool concept and I am very interested!
Here is a link to the demo video from last year. http://www.youtube.com/watch?v=GpSObv5vhtU

[Kingfish]

Video: Monstrous!

How wide can you go on the frame; what’s the typical engine width?

These large windmill magnets might do the trick if you can get enough rotors to fit:

• 14-inch OD x 8-inch ID N45; Massive torque, tremendous inertia, not cheap.

We would still need to know the details: Rear Wheel size, target speed, expected hp.

~KF

[Biff]

[*]To equal the motorcycle land speed record, the correction factor = 376.363 / 30 mph = 12.5455 (rounded up); my 24-inch tire would have to spin 87.86 rps or 5271.3 rpm using at least 25 hp / 18.71 kw (no losses).
[*]To equal the electric motorcycle land speed record, the correction factor is 176 / 30 = 5.87 -> 41.1 rps or 2465 rpm @ 11.73 hp / 8.75 kw.

I don't mean to burst your bubble, but I can't see how you will get a bike going 300mph with only 25kW of power. Those land speed bikes something like 1000hp. The aerodynamic advantage and light weight of a bicycle won't be anywhere near enough to get you that fast.

with 19kW you could probably go about 110mph tops, and with 8.75, you would be good to push 90mph, unless you are in a streamlined / recumbant type bike.

I will admit, I could be wrong, and I would be very excited if you could show me how you plan on going that fast with such little power.

-ryan

[Arlo1]

Ok guys here is the link to my build thread! viewtopic.php?f=3&t=21449
The original Bike for the job is a 10 inch wide tire but One with a 15 inch wide tire might be coming up!
The Goal is 750 kw but this might be over shoot because I am just going by info from the Current nitro bike info of 900-1000 hp but the beauty of an electric motor is its torque and how it increases as rpm decreases (to an extent)!
But this is looking like its going to realy happen!

[Kingfish]

[*]To equal the motorcycle land speed record, the correction factor = 376.363 / 30 mph = 12.5455 (rounded up); my 24-inch tire would have to spin 87.86 rps or 5271.3 rpm using at least 25 hp / 18.71 kw (no losses).
[*]To equal the electric motorcycle land speed record, the correction factor is 176 / 30 = 5.87 -> 41.1 rps or 2465 rpm @ 11.73 hp / 8.75 kw.

I don't mean to burst your bubble, but I can't see how you will get a bike going 300mph with only 25kW of power. Those land speed bikes something like 1000hp. The aerodynamic advantage and light weight of a bicycle won't be anywhere near enough to get you that fast.

with 19kW you could probably go about 110mph tops, and with 8.75, you would be good to push 90mph, unless you are in a streamlined / recumbant type bike.

I will admit, I could be wrong, and I would be very excited if you could show me how you plan on going that fast with such little power.

-ryan

Biff, you took me literal friend
I have no way to tell what the losses will be without empirical measurement so this is all pie-in-the-sky. Can we go 300 mph on an electric motor? Who's to say; ain't been done before. No arguments. Can we do 176 mph? Yeah, I really think so - but I'm not going to do that with a bicycle; wouldn't make sense. Speed record bikes need to be custom from the ground up with ~ like you said... a heavy hand on aero

To dream, to aspire towards lofty goals, and then reach for them. Nothing wrong with that.
~KF

[Kingfish]

Ok guys here is the link to my build thread! viewtopic.php?f=3&t=21449
The original Bike for the job is a 10 inch wide tire but One with a 15 inch wide tire might be coming up!
The Goal is 750 kw but this might be over shoot because I am just going by info from the Current nitro bike info of 900-1000 hp but the beauty of an electric motor is its torque and how it increases as rpm decreases (to an extent)!
But this is looking like its going to realy happen!

Nice Arlo, real nice!
Got a few questions. Do you mind if I move our specific conversation about your endeavor over to the Brushless Drag Bike! thread friend?

I'd like to save this thread for exploring different AF configurations and such.

Jazzed, KF

[Arlo1]

Yup for sure!

[Biff]

Biff, you took me literal friend
I have no way to tell what the losses will be without empirical measurement so this is all pie-in-the-sky. Can we go 300 mph on an electric motor? Who's to say; ain't been done before. No arguments. Can we do 176 mph? Yeah, I really think so - but I'm not going to do that with a bicycle; wouldn't make sense. Speed record bikes need to be custom from the ground up with ~ like you said... a heavy hand on aero

To dream, to aspire towards lofty goals, and then reach for them. Nothing wrong with that.
~KF

Definatly nothing wrong with dreaming.

Here is a link to some articles about the current electric land speed record vehicle.

This first link is from 2007, but it is the only one I found with reference to the power the thing has
http://green.autoblog.com/2007/05/14/th ... record-ca/

That says it is 700hp, and it was going around 300mph

Here are some more articles
http://green.autoblog.com/2010/08/24/oh ... cord-with/
http://www.bangshift.com/blog/World-s-F ... t-Now.html
From what I gather, in 2009, the fuel cell powertrain went 300mph, and in 2010 the battery drivetrain went 291mph. They are hoping to go 360mph or faster in 2011 with their new car.

I think if you were to begin designing an electric motorcycle to have similar performance you would probably want to use that as an approximate model of the power and aerodynamics needed to get you to those speeds.

The fastest electric motorcycle (non streamlined) is the Lightning Motors, which did the 176mph. They have a motor out of an old EV1, which I think is 150kW (200hp), but I could be wrong. If you want to beat it, you either need to be much more aerodynamic, or have more power ... or both . I haven't read much about the top speeds of the fastest electric streamlined motorbike, the only one I can remeber is the KillaJoule, which used the same drivetrain as the killacycle, I don't think it did exceptionally well, the team has a lot to learn about stream-liners and such .. I think they will be back with an improved design. Here is an article about the KillaJoule, I know I saw some video of it on the salt but I can't remember where I found it. http://green.autoblog.com/2010/09/13/ki ... le-salt-f/

I guess the bottom line is .. If you want to use this axial flux coreless motor design to get a land speed record, you probably want to design it to do 250kW for at least a few seconds

[liveforphysics]

The lawless electric dragbike that just sh*t all over killacycle's face is trapping 177mph, and getting there from 0mph 7.469 seconds.