Ground Up E-Freeboard | Custom Control Algorithm: Dual VESC | Dual, HUB 2200W 150KV Motors | Work In Progress |

No idea. I’ve just heard that its a common way people reduce the kV of their motors for DIY hub motors.

I believe @The_Dude did it for his motors so he might know what’s up.

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Thanks!

So, @The_Dude It would seem that between finding rugs that pull the room together and watching steve buscemi die on the sidewalk, you solder motors to change their Kv? I’m curious as to whether the Kv drops due to a change in motor characteristics, resulting in an increase in torque, or whether the motor is just less efficient? I would love some input :smile:

You got it :sunglasses: When you convert the motor winding from Delta to Wye the motor kV is reduced by a factor of 1.7. Additionally the torque increases/is shifted to the lower rpm range. The is a very thorough description from @Duffman in the german forum available http://www.elektro-skateboard.de/forum/eigenbauten-95/mbs-pro-90-4x-vesc-ntm5060-12s-4349-2.php. Currently I’m working on a dyno to record the characteristic curves of bldc motors. Doing so, you will know exactly at which rpm the maximum efficiency of you motor is and design your gearing according to that.

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Update 3:

Unfortunately, I spent most of my weekend digging holes and patching sprinkler systems (-_-) so i didn’t make quite as much progress recently as i would have liked. However, that doesn’t mean i made no progress!

I spent most of my weekend looking at decks. Due to the nature of the conductive slip rings, I need a deck that insulates current, eliminating aluminum and Carbon Fiber. This does leave the classic wood look wide open. I was thinking of doing a 4-5 ply out of either hardened maple or african Mahogany. In any case, I definitely want to do something with racing stripes :sunglasses:

I’ll probably change my mind back and forth several times before i even begin cutting the deck, but I’m thinking either a red heart or purple heart inlay to make the stripes.

Found both of these pics on pinterest btw. They’re not mine. The first is called purple haze, and the second has no notable annotations. Sorry OPs.

Anyway, I’m going to be using the Freebord “Da Blues” wheels, so I’m looking for something that pairs well with their colors. I figure, If it’s worth doing, It’s worth making it pretty too.

I also did some battery work, Looks like i should be able to package a 8s4p if i use VTC6s. So I cadded for that. In actuality, I’ll probably make two different 8s2p packs and just wire them in parallel. Rather than shrinkwrap the pack together, I’ll probably just 3D print an enclosure :smile:

Here’s what they will look like without their master enclosure mounted on the board. I lined them up opposite eachother so that i can use two ESCs on top of them and run the wires down the according edges, keeping flush to the case.

I also began the process of wire routing, in theory. Due to the fact that the slip rings are actually sunk into the board for stability, I will need to wire leads to them from the top, channeling through the board at an angle, finally connecting to the power electronics at the bottom. This should keep the top pristine and pretty. It may also add some BA circuit board looks :smile:

Grey Lines indicate Wire Routing.

I’ve been looking at off the shelf parts to drive the motors, And I’m leaning toward writing my own PWM just to prove that i can, then using a pair of VESCs that are Canned together in the final iteration, but that is months off.

Tomorrow, I will be flushing out the rest of the production cycle in terms of dates and deliverables. Yknow, Setting goals and whatnot. I find that having deadlines pushes me to do better work.

Yours,

A very tired, sunburnt VillainousJ

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Awesome! Just out of curiosity, where do you plan on buying your slip rings from? I might be making an electric freebord my self on of these days so it would be nice to know :slight_smile:.

I was going to combine them with the lazy Susan’s. Current travels through the top ring, into the balls, then onto the bottom pod part, hence the 3 phases. So I’ll just lathe them myself. I’ll post my final CAD, and then you can cut yours too. Or you can bring the files to a machine shop and they can do it too.

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Awesome, looking forward to seeing it completed!

Awesome work. Really nice to see your work on this Buddy.

Running a Leiftech for about 4Weeks now, had to replace most of the parts to get it working good : Outer Wheels Center Wheels Driveshafts Pulleys Batteries Controller

Actually i was able to fix all bugs by myself. What i’m affraid for is that the Sliprings fails… so i really really looking forward to your ideas about that.

Continiue the great work

Hang Loose Jenso

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Really Nice. I want to get another e-Freeboard choice. The one that I have only from Leiftech. Really want to try something else.

Update 4:

How do you do, fellow kids?

I’ve put a lot of work into the electric freeboard over the last few weeks, so let’s jump right in.

First, I designed a battery box, which includes mounting for the battery pods, as well as mounting for two VESCs, and routing for the battery bus and wires. Furthermore, it comes in a version that uses heat syncs, and an active cooled version with mounting for 2x 40mm fans.

and Vented Version

This brings us to my next development. The choosing of a battery and thermodynamics of heat dissipation.

I think I’ll be going with a 6s5p pack of VTC5As for their middle of the road capacity and relatively low run temp at 20 Amps/cell.

I also ran some basic differential EQs to calculate the amount of heat i would need to keep the cells at 50* C on an extremely hot summer day (40*C).

I used the data collected by the gentleperson-scholar Mooch over at the E-cigarette forums on various 18650s. https://www.e-cigarette-forum.com/forum/blog-entry/list-of-battery-tests.7436/

After compiling the data for several different cells, I compared their performance versus heat and weighed several different metrics including safety, capacity, and maximum amperage.

https://drive.google.com/open?id=0B0zQsjKfE5R7THFzSHlkOVpuZ2s

The VTC5A runs relatively cool at 20A, (73* C) and has a capacity of a little over 2 Ah. 6s5p should give us a pack that can push 100 amps continuously, at about 12 Ah. Which is massive. Still working on procuring a spot-welder.

BUT, 73* C is still a bit too toasty for lithium. We certainly don’t want another hoverboard situation on our hands. So, I set out to determine how to dissipate some of that heat.

Despite my ridiculous spec, i do have several things going for me. The first being that when the batteries are outputting max amperage, the board is moving at max speed, leading to a higher coefficient of ambient convection. Beyond that, I have ample space to fit heatsincs and can always switch to an active cooling system.

I won’t bore you with the maths (DM me if you’re interested), but all in all, I determined that i could keep the batteries at 50* C with a heatsink surface area of 0.07 m^2.

https://drive.google.com/open?id=0B0zQsjKfE5R7UXE5bkwtUk82cnc

This may sound insane, but it won’t actually look too bad.

I should be able to cut it out of aluminum with a plasma cutter and a diamond edged saw on a table saw. It’ll heat up like nobodies business during the process, but should turn out fine.

I also cut the majority of the sliprings, but broke a millbit, so have not been able to finish their features. Preliminary tests look good, as i’ve been able to run an LED phase to phase, spin the slipring and maintain consistent current through the LED. I plan to validate the design by getting a current sensor on the leads and testing the ripple.

I love it when a plan comes together.

Next up is the board itself.

I’ve procured some 1/8" Purpleheart, and baltic birtch plywood, and am planning to cut the blanks this week. I have .STEP files of the board blanks themselves, as well as .DXFs of the individual wire routing.

In other news, my G3R hanger arrived, and i managed to prototype a mounting system out of wood, soon to be cut out of metal (The Freebord guys actually suggested this on the phone. Thanks Freebord guys). I also ordered the rest of the hardware for the board.

Motors arrived too, and VESCs are on the way. The only thing left to buy is a radio-receiver, batteries, and some 3D printing filament.

On the coding side of things, I managed to get a motor spinning using basic delays and hall effect sensors, but have not been able to implement PWM, as i burned 2 of my FETs, and am waiting on more.

Turns out the Hall effect sensors are actually super easy to work with.

The Orange, White, and Green wires are all 3-phase signal outputs that switch to high as the magnet passes over the sensor. Furthermore, the red wire is power, and the black is ground (standard convention).

Here’s my Code: https://drive.google.com/open?id=0B0zQsjKfE5R7R1hBdENoNXVhM2c

All in all, this design should be able to push a 300lb rider 25mph up a 10 degree grade in 115* F weather. Which is absolutely insane.

I think that’s it for now.

This week, i hope to have most of the parts cut, with the exception of the power electronics, and a chassis assembled.

Cordially yours,

VillainousJ

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Super nice Mate. Straight forward, thanks for the update. Got the G3 Hangers here by myself, really interrested in your Baseplate solution !

Cheers from Germany Jenso

Hi @Nowind,

I was thinking of doing something like this:

The thought is that you cut three pieces out of aluminum, and use the same two side pieces for the different middle pieces. This will allow the adjustment of rock, and easy modifications as to mounting geometry.

For example, if you wanted X inches of rock (i don’t know specific numbers as i haven’t nailed down other critical dimensions), then you would use a 1/2" lift center. Or if you wanted X+1 inches, you would use a 1+1/2". Pictures attached for reference.

The side plates use a common mounting pattern to most longboard trucks, so you should be able to use them on most premade longboard decks. They mount to the center piece via bolts in the XY plane.

You can prototype too if you like. the only dimension you really need is the angle between face that holds the kingpin bolt, and the pivot cup, which is 150 Degrees.

P.S. I have more parts in the mail from freebord, so i should be able to assemble this mounting concept soon.

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73°C for the batteries would be at constant 20A discharge. You already said that would equate to 100A continous. You will never reach those levels - there is no reason for that complicated heatsink design.

is also wrong - the top speed is only set by your voltage. You can go full speed with almost zero current if losses are low enough. You will draw current mainly during acceleration - and you won’t be just doing stop and go all the time.

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So very Cool !!! I can’t wait to see the end results.

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My thinking is that each of my motors will take 50A a piece (Max spec is 60, but I’ll limit that in code), resulting in 100A total. You are correct, that you can go full speed, at almost zero current if you have no load. But the amperage does directly affect torque, and since we live in a real-loaded world, we’ll be needing more torque as speed increases, due to the fact that road load increases as well.

After preliminary calculations, and benchmarking commercial products, It looks like my spec will require about a little over 2000 watts per motor.

My math can be found here: https://drive.google.com/open?id=0B0zQsjKfE5R7dG9ldjhaSnBHSmc

I get that it’s counter intuitive to need this much amperage, and if i were designing the board to a lower spec, then i wouldn’t need anywhere near that. But, I’m accounting for a high-level of road load including potential grade, wind resistance, and rolling resistance. The spec i was given was insane, basically the purpose of the exercise is to design for a worst case scenario of a 300lb rider, up a 5* Grade, at 25 mph, in 115 degree heat, while maintaining the longevity of the batteries in an optimal temperature range. This means limiting the battery temp to 50 C, which is the the upper end of the happy range of lithium. While they can be run hotter, this decreased battery life fairly significantly.

I do hope that i made a mistake somewhere as the heatsink will be heavy, and a pain to fabricate, but I’ve had several other people check my math, and perform the calculations independently, and they all came to the same conclusion.

I realize that my duty cycle is unrealistic, as are my test cases, but these are the specs i was given.

Oops,

Old Math.

This is the updated document: https://drive.google.com/open?id=0B0zQsjKfE5R7dG9ldjhaSnBHSmc

the shared experiences on this forum show that you need around 10-20Wh per km on average. Please calculate how much current you’ll be drawing on average from this.

Your motor CAN do 60A - but you will rarely do that (or 50A for that matter). At speed the limiting factor is voltage - not current.

It is good practice to overspec the battery so that it can handle the abuse - but to manufacture cooling solutions on the assumption that you will ride at a constant 2000W is unnecessary.

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Update 5:

Things are happening!

I’ve frozen design, and started production. Since my last post, some minor design changes occurred.

The most significant is probably the electronics move. In previous design iterations, the electronics were on bottom of the battery box. However, this pretty significantly reduced ground clearance, and left the VESCs vulnerable to impact. So, I moved them to the top of the board, and actually sank them into the deck a bit. They are also covered by a 3D printed enclosure, for safety.

This poses several problems, The primary being 3D printing the Top Shell. Since the 3D printer I’m using doesn’t have support structure, there’s a high probability that the shell will sag. So, I elected to add support Gussets, for construction.

Then, we will 3D print the shell upside down, and cut the gussets off with a razor later. Also notice the mounting shelves on the northern and southernmost faces. This is where i will glue magnets, resulting in a fastener free method of holding the shell to the board.

The next design change is to the battery box.

The box now features removable doors, allowing access to the batteries for diagnostic and repair. Furthermore, it includes mounting points for the VESCs that will protrude through the top of the board. Other than that, It’s essentially the same.

The other major change is to the wheel pods.

I moved away from hub mounted wheels to a more standard, chain drive. I have extensive experience using chain, and prefer it due to it’s lower space profile over that of belts.

The axle will be 1/2" steel hex shaft, utilizing hex hubs to mount the motor and a 16t hex gear to drive the motor. The other gear will mount to the shell of the motor, and spin with the outrunner.

Now, Let’s move on to some physical developments!

First, I cut and validated the Lazy Susan Slip Ring. Everything worked surprisingly well!. There is some skipping between the phases, but i hope to remedy this with a diaphragm and polished race tracks.

Next, I cut the board!

I’m actually manufacturing two decks, one without inlay, and one with. The board without inlay is cut in it’s entirety, and the board with inlay still needs the purpleheart additions, and the holes cut. I used a ShopBot to fabricate, Essentially a CNC router. I started by setting zero, and cutting the top features. Then, flipping the board with the same zero, and cutting the bottom features.

Cutting Decks has never been so easy!

I also started powder-coating parts. The black looks nice.

Up next are the battery packs. My pack will be a 6s5p pack comprising VTC5a 18650s supported by 3D printed runners.

I will be custom cutting bus bars out of 1/8" copper, and fastening it using silver-conductive epoxy.

All in all, things are coming together!

Yours,

VillainousJ

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So sick! How much ground clearance will you have under the motors? That seemed to be kind of an issue that @Nowind pointed out in his Leiftech abuse thread. Build looks great so far. :+1:

Should have about 0.75" of ground clearance on the motors… I hadn’t heard about that abuse. Something to look into!