Student Project | Skike motorization concept - building a prototype

Hey im Moritz and I am planning to build a more comfortable “electric-inlineskate”-thing. I know that there have been some concepts in the past (like “Thundrblade”) but are pretty high off the ground and use small rubber wheels without dampening for high speeds. My idea is based on a larger wheel diameter with rubber tires or air-filled tires and a lower center of gravity. Thats why I plan to base my prototype on 2-wheeled rollerblades called “Skikes” or “crossskates”. skike-teile

In the past I really wanted to build my own e-longboard and later an e-bike but never really got to it as I was always told that I had a functioning bike and two working legs :v For some time these plans were forgotten and now that I have to commute to my university this Idea came back. Now this semester I got the chance to “realize my own project” and this will be it! So its a project im planning for my university and I really want to realize a functioning prototype which can also reach speeds of an average biker. For the whole project I got nearly 70 days left :sweat_smile: and am in kind of new territory.

To get a feeling for how these Skikes feel and handle (also for measurements) I already got me some used off ebay and am now trying to get my electronics set for ordering (and mechanics, depending on the type of motor I use). That is time-critical I think because of the long ordering times I saw from browsing 100 chinese sellers websites for different motor-types… Because I only had to work a little bit with drones and occasionally with electronics/mechanics as a hobby, I would love to get some hints about what to choose for the drivetrain. The wheels are 6 inches outer diameter (150mm) and there could maybe fit 8 inch wheels (200mm) into the wheel mount.

One concept could drive the wheel from the top with a small hub motor pressing onto the wheel. It would be kind of compact and maybe slower+lossy than other methods, also might slip.

Another concept would be a typical brushless motor (with a low kv?) on a mount (i would have to machine) and it would drive the wheel over a gearbox (heavy+complicated) or some sort of belt/chain.

The last option I would take into consideration would be a hub motor directly replacing the 6" wheel. This last option would be the most compact and clean method (I think) so thats why i already searched many parts of the internet for hub motors that would have 6" diameter (~150mm). I know that there are 6" motors with through-axle for scooters but they often say that they are made for 12km/h and also advertise them with details like watts, voltage and max-rpm instead of KV or max-current. So far I have only found this with advertised 400watts (?) and although it says 6 inch it also says it is 170mm in diameter (which should be okay)

I wonder how these handle higher currents or voltages as I imagine the max-rpm is for the highest voltage of the ones they advertise (24/36/48V) how would that scale with higher voltages and how would that translate to the middle 36V for example (10s battery) Another great motor that I found was the

which is really expensive and I dont really know what the 6-Pins of the hal-plug are for (instead of 5-pin standard) and the general pinout is unclear because of lacking documentation about their “proprietary” motor-wheel. Then I found a clone of these wheels that is supposed to deliver similar power:

The last one has 36kv in its description which should be relatively slow (so is it high torque - low rpm?) A candidate with 8" diameter from amazon would be this listing: https://www.amazon.de/Electric-Scooter-24-V36-V48-Brushless-Electric/dp/B078S4268V/ref=pd_rhf_dp_s_pop_multi_lclrrecs_rbr_cn_1_sccl_8/261-4874303-2382661?pd_rd_w=cCGKN&pf_rd_p=9911ab34-8a76-4d9f-914b-338ea24ff951&pf_rd_r=5JJ92YHETTGTQ7GT1EBJ&pd_rd_r=7ff23fdf-a429-4c59-911b-b35ef1c671e1&pd_rd_wg=w2K6F&pd_rd_i=B078S143MR&th=1&psc=1 What confuses me about most of the listings (similar to the last amazon one) is, that they look very similar and state various output powers and max speeds. Are these just picked randomly and it reaches like 18km/h at best, so its claimed speed is reached with 0 load or are these claims about >30km/h realistic. I can imagine that they are again depentent on the voltage but it would be nice to have some sort of max speed on a fixed load :thinking: Well if any of you have a recommendation or experiences with these sort of motors please let me know! Maybe I will switch back to some other brushless motor and drivetrain if you convince me for one or the other ^^ Another thing for the motor decision would be that the wheel mount of the skike is quite narrow and could need modification to increase width. With a hub motor on top it might require minimal modification and with hub motor inside or belt-drive it would almost certainly need widening/welding. Exept if you know a method of driving a wheel in these narrow spaces (are there slim chains? or thin belts with thin belt-wheels. Or are these maybe too weak/unstable?) This is the top-down view of the stock backwheel:

Depending on the motor I will continue the project with the sourcing of fitting ESCs or VESCs (that many talk about as I have seen recently). Then I will continue my questions about wheter or not I can have two inputs per esc for something like tilt-control on the legs and hand-controller simultaneously (two input methods per foot and each foot as an independent system). Battery is planned to be a 3-D printed quick release 18650 ~10S pack on each foot.

Well I am just posting my project with most of my questions here and I hope that some of you can give me advice or hints on what I am overseeing or doing wrong :sweat_smile:

Thanks for reading my wall of text and links so far!

I also hope this topic is in the right cathegory. Otherwise should I split it into more focused pieces for each cathegory?

The topic is correct. However, making an actual esk8 is pretty interesting. I would love to see this project being done. But at most, I will answer what I can accordingly:

The concepts:

The third concept best fits if you’re planning on a clean build for these. And since you’re looking into hub motors for this build, there’s a few keys that might be different than your normal understanding.

Hub motors are not often measured in KV. If anything, they’re usually measured in watts and voltage. This is where watts would be the more focus on hubs unfortunately. Hubs are usually measured in between 60-90kv but aren’t a factor in most cases so do not look into that. Focus more on how many watts it takes and the voltage it can handle. The higher the voltage, the higher the RPM.

The higher the voltage, the more power you will gain, and the more speed you’ll notice due to higher RPM. 10s would be the middle and can be considered a sweet spot to many people. Not too weak and not too crazy.

6 pins just means they added a temperature reading. 5 pins just means they did not add a temperature reading sensor.

Don’t let this fool you. It means that it has torque. It’s not always accountable as “slow”. I thought the same way with my 60kv hubs. Boy was I wrong going 35mph.

Call it a catch 22. They’ll say what will get you to purchase from them. It’s not always black and white, which is why people may waste a lot of money trying to know if it is or isn’t.

Basically you have a good concept on what you’re planning for. As for the batteries, are you planning to put the esc and the receivers inside the skates and use a 10s1p battery?

Thanks for the detailed answer so far ^^

Yes im planning to use 10s1p batteries (maybe 12 cells if my motors +esc can handle that and it is too slow with 10). Each of the skate may work independently and both with the same components, each one esc and battery. Now I need to figure which motor I will use and what power it can handle so I can then think about which esc to get. Any recommendations for that as the motors differ strongly in power (and delivery time)? Should I get one of these “cheap” supposedly 1000w motors (instead the 1200w sxt ones) and a (“cheap”) scooter esc? Or are these hard to get vesc still the ones to go with?

I also think about the ways of how to control them and havent found much about multiple inputs per esc or if two or four remote controls could be used to control two esc. Thats why I am a little bit worried about interference between controllers and thought about some sort of “gas pedal” or pulley that activates a throttle (potentiometer of some sort) on the foot (by leaning forward while the foot stays horizontally).

Ideally the esc would be able to be configured in a way that handles two inputs that are from two different sources and i guess need a type of hierarchy so Im not so shure if that even is possible (or even necessary). But the idea would be to have control over the skates without hand controller and optionally with hand controller… maybe I should really see this as an “option” and think about this later when the drive system is working with normal handheld controllers :sweat_smile: And for that im thinking about interference between two identical remote control-esc combos working this closely next to another and if they are on channels and how I would set these (or is it automatic)?

Now I also remember that I had two identical cheap rc-helicopters and they could be bound to one controller by pressing bind buttons on both simultanously. Would that work with wireless controllers for the escs too? :grin: or would that result in problems even if it worked?

Since you’ll be using hubs, they probably won’t need so much power, but you can still have the ability to have an esc that can give you more if needed. So you can look into makerx SV6 esc. Great if you’re using single hubs per skates.

I would buy the 400w scooter wheels as a test and then replace them with better ones. I know about the L faster one. If you’re not too crazy, 1000w motors would be the sweet spot. 350-500w are still pretty good. I’ve seen scooters with those wheels do fine.

Buy yourself a remote that can use two receivers on the same remote. The mini remote is capable of doing this and a few others are able to as well. The mini trigger remote is just more known. As for controlling via movement of your foot and having a remote as back up. It might not be possible since you need to do a lot more set up entirely. And you will need a Bluetooth module and an vesctool app, so it adds more. This only works if you’re doing dual hubs, but I think you aren’t.

Not on single escs and not if you don’t have the app/switch to change ppm inputs and settings. Lots of work tbh.

Connecting the mini remote to two receivers is as simple as pairing them. You just need to set it up on the esc as well. Simple stuff.

Yup, same thing. Just note that there are only a few that can do this.

Not that I know of since the person that did it is well known here.

Okay I have looked into most of the sellers that offer these 6" 350-400w motors and all of them deliver from china. Now im thinking about a few things: They might not be able to deliver (i heard they have covid lockdown in china atm…) and that one 150€ 350w wheel on amazon which is 8" seems a bit weird with the very little information about the motors and their specs (especially with the 24/36/48V options all on 350w). The ~6" “1000w” from china is nearly the same price (but im unshure about shipping/import costs on these) they are 165mm in diameter and claim 800rpm which would lead to about 24km/h. Now the listing unsettles me a little bit by saying 48V in the title and everywhere else 36V so I assume the rpm might be a little bit lower but I would be happy with about 20km/h ^^

The motors have these multi pin connectors and show this picture on the listing:

The connector also has 8 Pins (very pixelated this might be near impossible to read properly) while the listing says 9-pin-plug in the comparison table :thinking: so it has 3 pins power and 5 or 6 pins for hal-stuff? (I really hope they send an hd version of this paper so I dont have to take this thing apart to figure stuff out :smiling_face_with_tear:)

If it turns out that these take more than a month to deliver, I may have go the even more expensive route and take the sxt wheels which are supposed to take about a week to get to me…)

On that another thing: do these hub motors support regenerative breaking? Or does that simply depend on the esc (and bms) used? These are listings for makerx sv6 escs if thats correct and they say that the esc supports regen braking (surprised how expensive these can get but they have great features and seem much more trustworthy than all the chinese escs I looked at so far… I guess I extend my budget then, because now I want these ,_,). Also I guess the bms would be able to protect the batteries from overcharging but I always wondered what happens when the braking power cannot be converted into battery charge. When the load (charging the battery) is no longer consuming the produced power, does the motor even brake anymore or does that heat up any other component in the system leading to failure of the esc/motor or bms?

Unfortunately yes, due to their lock down, it may be harder to receive these parts. And yes, these motors are usually run with a different esc. I believe these also run differently. However, the only thing you need would be the 3 main motor lines since i believe you’ll be kick pushing yourself to move instead of a stand still. The other motor you showed had a 5-6 pin. That is usually a skateboard wheel since they use these hall pins.

Looking at the schematics you sent, it doesnt look much different. The other pins might just be just a specific plug and play. But it seems they’re pretty much no different. They still have 5v/gnd/and the 3 halls, and the 3 motor wires. That’s pretty much all you need to know. It just seems theyre all connected accordingly to the connector itself.

See if you can buy one that has the 3 phase wires and the rest are the hall wires separately.

Esc and bms. If you bypass the bms to charge only, then you don’t need to worry about the bms part. The Esc does this part. And believe me when i tell you:

This is true. And yes, they are expensive because it’s not made cheaply. DIY is never cheap, especially in parts.

Yes and no. Yes the bms will protect you from overcharging, but if you do not brake with a full charge, you’ll be fine. Also, depending on your bms choice, it can be as dangerous as losing power due to your bms randomly breaking or stopping power due to overcurrent. So yes, it can and no, it can still be dangerous. I recommend bms bypassing so that you only use it as a charger and balancer.

A more focused point here:

Nothing. You literally just don’t have any brakes. I tested this by putting 0 amps in regen braking and you get no brakes at all. So if there’s no power in braking, you get none. This was my results. And I don’t use bms discharging.

Thank you again for your help! I have found these motors which are spareparts from the Ranger X2

They offer “old” and “new” versions of their motor and only say that they use a different “hall line sequence” (and slightly different kv rating) i guess I just have to take a gamble and order the newer ones as they are the same price and the whole package is slightly cheaper than the alibaba-1200w motors. They also say that the specific esc is needet to use the motors but I guess that only counts, if I try to use the hal-sensors and/or their intended esc from the board (as it is a replacement kit). I havent read much into the hal-pinout and function yet but you said that it is fine to run them just over the mr30 connector? And I guess the sv6 support these weird little motors :sweat_smile: Ooh im so nervous to order these parts and in the end they dont work together or i break them >< but i also really wanna get to the building process!

Now I also read online that this type of hub motor is often just limited by the esc for different reasons and that there should not be much worry about the motor not being able to handle much power. Someone wrote that its limited for battery range and kind of a high-current prevention if it would drive uphill with heavy persons for longer periods of time (and maybe price reasons as higher power esc might be more costly to produce and not really necessary as the “lower” power is sufficient)

(and for that bms bypass, that seems like a good idea and I will look into that and i guess someone already asked that somewhere so I just got to look for that ^^)

Also just read about “no spark switches” which are controlled with a small button instead of one of these connector-plug loops is there any difference or benefit exept ease of use and the looks (less janky)? Otherwise if this kind of switch is necessary I would try to 3D print a housing for these xt30 connectors. But if I make the battery removable and charge them outside of the system (just the packs with their bms) would any of these switches be necessary? Just plug in the battery to turn it on?

Lastly a thing I had in mind at the beginning of this project: would it be possible to use a mounted bms on the system and just exchange the 18650 cells? like in a razor or household electrical device with AA batteries? Or is that too dangerous even with bms (on the skate) because of potentially high voltage differences between the cells and being high discharge capable… Just not really doable? Or would that perhaps be possible with 18650 cells that have these tiny protection circuits that offer overcurrent protection? Just an Idea that would enable a different placement of the individual cells (although it could be kind of annoying to change these cells every like 4 kilometers… each :sweat_smile:) It was just something that I havent found anything really at this point and I guess there are reasons why noone has done these kind of battery-holders with individual cells yet (would save me spot-welding tho)

Not bad. It might be a good start if it fits.

Don’t let this trick you. I used a makerx retro esc on my hub motors that needed a specific esc and found out it only needed 40 A of power for it to function. Just use FOC mode in vesc tool. It’ll get it working.

Yup. Just change the connectors and it’ll work.

Yes. The motors will pull only what it needs to drive it. The esc is what does all the work.

Antispark switch and I do not recommend them since they can fail at anytime. I would recommend doing an XT90 antispark loop key instead. Much better and if something happens to the key, you can easily swap it out by making a new one, instead of wasting $60+ or more in your price on a switch.

That would be a bms switch. That’s only needed if you want to turn off the bms (definitely not necessary). Just make it a plug and play. And you can separate the bms wires from the bms and make it an external charger. You just need to connect the bms leads to the bms. But its better making a battery with the bms to save some space.

If you’re asking if its possible to do something called a battery swap, you have to use the same battery you’ve used to set it up. Different batteries and different amps can result to different things and ends up bad in the process. It is possible to do it by making your battery build swappable by mounting your XT60 connector (assuming you’ll use this) and let it plug in together. My recommendation would be to make a 10s1p pack with Molicells p42A for both power and amp. They’re great at 35A current and you’ll probably get more than you mention. But yes, most of us makes a 10s2p instead.

18650 cells don’t have protection as far as I know. The life04 batteries does, but they die quick. Just look at the boosted boards. They were 12s1p life04.

With the protected cells I was referring to something like this: What is the Difference Between "Protected" and "Unprotected" 18650 Batteries - Fenix They are pretty expensive in comparison to the 21700 cell you just showed though :melting_face: And I think these protected cells are not really intended for the use in multi-cell packs and more for the vape and maybe flashlight market.

So far I heard from someone to use a specific samsung 18650 cell but the molicell looks even better in every aspect (exept size but that is negligable in this 10s1p pack and its just a prototype… but I want to keep on using and change/iterate it maybe in the future ^^)

So what you said about the battery swap is still a bit unclear for me but I think I forget about that concept as it may just not be worth the extra-trouble and will simply go with battery packs that are made of 21700 cells and a bms so I could make multiple packs to quickly change them on-the-go like it is common in powertools. And charge them outside of the skate. Possibly have differently sized packs with the same voltage (like 10s1p and 10s2p). I guess its not possible to change the battery on-the-go when they have different voltages? I would imagine that I had to configure the esc to a specific voltage curve and if I change from 10s to 12s without going through the esc-configuration again it would come to some …unknown or bad outcome? Also if the exchange between 10s packs is okay, I would guess it would also be okay to switch 10s 21700 packs with 18650 packs while nothing needs to be reconfigured? (as long as the configured discharge current isnt exceeding the safe current of the 18650 cell?)

Ah. Interesting. I haven’t used these but that’s interesting to know.

Basically this. You have to do this if you are using different battery as a swap out, every time. That’s why its best to stick with one battery and just increase the p group if needed. I’m terrible at making some parts clear. This was right.

Correct, however, there’s maybe a few in the 18650 that could come close to the 21700 cells. If you’re going 18650, find one with a good discharge and capacity value.

So my shopping list is coming together :grinning:

Ranger x2 motors (hoping they dont fall under the 50% anti dumping tax from china)

(Link is already in the 8th post so it warned me about sending it double)

2x Go-FOC SV6 VESC6

20x Molicells for two 10s1p packs

2x bms because it seems to fit the specifications and a temperature probe

Now I guess I have to look for a remote (1 or 2) with compatible receivers (2) that are working with the sv6 esc.

Also need to plan the whole thing on paper diagram to have a safe overview and so that I can guess all the cables and plugs I still need for the circuitry :L

(I havent figured out how to quote links somehow it just quotes the text :sweat_smile:)

nkon offers a service to add solder tabs to the cells for 0,55€ each. As I dont know if the workshop where I will be doing most of this has a spot welder I might order them with these tabs and solder them together with a normal soldering iron. :thinking: Also thinking about whether or not I should get spares in case I fuck up one of the cells while working with them or one or two are faulty from the factory… Any data about the amount of dead on arrival singular cells that people ordered? Should I order 22 just in case?

Depends on where they’re brought from. So yes, I do recommend buying a few extras just in case.

I’m confused with the post thing. But its probably because your account is still fairly new. That’s probably it.

Any ppm/pwm receiver will work. But you want to look into something called a mini remote or remotes that can have two receivers functionality on it.

This one works as a two receiver, 1 remote:

As said, very few out here that can do this.

So if I get that mini remote I would need another receiver individually.

And now im starting to think again if it would even be beneficial to have one remote for both skates. Because when the esc doesnt get the rpm right for both skates because maybe I cant use the hal-pins from the motor with that sv6 esc. It would start to drive to one or the other direction if one of the motors or batteries behave slightly differently :thinking:

So either I get the esc to read the rpm of the motors and somehow set it up in a way that forces both receivers/esc/motors to go to a fixed target rpm with the current throttle level i am holding the remote at or I actually get two separate pairs of remote/receivers so I could maybe have somwhat like “tank-control” and steer slightly by pushing one throttle or the other in each hand more or less. That way of control might be a bit finnicky but maybe allows to counter any differences in speed between both skates.

This gets fix in vesc tool set up. You can adjust what isn’t turning right. And you are able to use the sensors, if its 5 pins, just skip the “temp” that’s on the sv6. My motors only has 5 pins and i made it work for the 6 pins on the esc:

The two receivers will usually be your DIY idea. If you brought two of the same motor and one may have a slightly higher value over the other, you can simply put them both on the same amp settings. This is all done on vesc tools.

It’s ultimately up to you. This is DIY after all. You usually have to take some risks to see the results.

Thanks again you are helping so much!

The problem I see with the pins of the motor is that I have no pinout of these Ranger x2 motors and im unshure how the esc understands the “different hal sequences” of the motor. Is there a way to determine the pinout? green black white yellow blue red is the pinout of these motors on the picture of the website. Do I need to measure some resistances or open them up to get the correct pinout if its nonstandart?

As for the receiver-remotes I think because I need two of each I will just buy two of these sets and try them out in parallel first. And if everything else works as expected maybe I switch to a single remote and bind it with both receivers. (If I go the weird route I may as well just clip both transmitters together and connect both triggers mechanically :sweat_smile:)

Yes. Red is 5v. Black is gnd. And if there is only 5 pin, the colors don’t actually matter. If its a 6, there is a temperature sensor, which is usually white. The SV6 will come with everything you need. All you need to do is either solder or change the pins and jst connector accordingly. It will tell you what pin is what. Just rememeber the red is 5v, and black is gnd and all will be simple.

Nope. It’s plug and play. I just took my pins and remembered the red and black :upside_down_face:

This is a good idea. Better to test and see instead of realizing that its not gonna work.

If anything goes wrong, and I don’t have the necessary info to fix it, I’ll send you to the other forum that is more active than this. They will definitely like to see this project work out as well.

If you want, I can pm you the other forum. No issues.

So I guess I will be trying the whole drivetrain with just the 3 pin power first and then “destroy” one esc and motor by just connecting the random wires between 5v and ground to the esc :face_with_peeking_eye:

And shure, another forum might be helpful as well and if anyone is just interested in this kind of weird project… thats great :smile:

Thanks again

Its kinda hard doing that when the esc is telling you where it goes:

Its also on the SV6 as well. You don’t need to really worry about it. Just wait until you have it. Then you’ll understand a lot of things. I was new to this as well. Everything has been simplified.

And I’ll send it. Glad i could help you out a bit.

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