Introduction: DIY Electric Mountainboard
DISCLAIMER: This project is not a beginner project, nor is it cheap. The total material cost was ~$1600 USD (prices vary), and requires prior knowledge or experience, not just dabbling, in fields such as soldering, battery care, electrical safety, and longboarding skill/knowledge (preferably with electric longboards as well). Although it may seem like it, this is not a plug-and-play project. 99% of the time there are modifications needed in order to make components fit or work together. This project is also fairly dangerous with a high voltage-high discharge rate battery that can easily cause a fire if handled or treated incorrectly. Riding this board could very easily cause injuries, or in very severe (and very rare) cases death. Always wear protective gear while riding and building a board. I am not liable for any injuries or mishaps caused by this project.
My Name is Zachary Quimson, and this is my DIY Electric Mountainboard that I built as part of Ms. Berbawy's Principles of Engineering class. The goal of this project was to make an electric board that had enough torque to ride on grass, dirt, gravel, and eventually trails when I am comfortable with it. I also wanted this board to be decently fast, somewhere around 25mph top speed, and have at least a 20 mi range while on the paved roads, which would give me around 10 mi range off-road. In this Instructable I will not explain how to exactly build my board since your specs and parts will likely be different than mine, but I will do my best to explain how to build an electric mountainboard, or even electric skateboard in general with some examples from my own build process.
The inspiration for this build came from my first group ride in San Francisco on my Boosted Mini X. I was riding with BAEsk8 around November 2019, and I noticed my board was easily the slowest and smallest board there and it also had the shortest range. I struggled to keep up with the pack and only made it about halfway through the ride even with a charging stop. I still had loads of fun, but I wanted more in both range and speed. I'm not saying that I don't like my Boosted Mini X, it is a great commuting board that is light (relative to an esk8), and has taken me hundreds of miles to school, friends' houses, and brought me lots of fun, but it is small and there are definitely larger boards out there. Other people on the group ride had boards that were more suited than mine for group rides, such as Lacroix boards, Kaly boards, Evolve boards, and of course the DIY boards, among others that I cannot remember at the moment. This lead me to research more about different esk8 boards, and I found that most production boards of that size and caliber cost at least $2000 USD, often times more. That was when I started to consider a DIY board.
After putting the thought aside for a while, then picking up some more research, I realized that what I wanted was not just a board capable of those group rides, but I wanted a mountainboard. I wanted something that could go through both street and dirt and manage them well. That was around the time that I found Lee Wright on Youtube and his amazing content, specifically his Building an Electric Mountainboard series. I did not follow his steps directly, but his videos were a huge help in teaching me about an electric mountainboard and how each component worked and was put together. By this point I was also a part of the Facebook group Electric Mountainboard Makers, the Subreddit r/ElectricSkateboarding, and the Electric Skateboard Builders Forum which has now transferred to ESK8 News Forum. All of these groups were great resources for general information about the topic and were eager to answer any questions I had during this project.
All of my tools and materials were my chosen parts that fit my needs and budget. You may choose different parts for a different build or different needs, but even with the exact same parts the build will likely be a slightly different process. You may also need more or less tools depending on how much you need to modify your components.
- Soldering Iron
- Heat Shrink
- 3D Printer
- PLA or PETG Filament
- Specialized 3D Printer - Markforged Mk2
- Onyx filament
- Fiberglass reinforcement
- Drill Driver
- 1/2" Step bit
- Arbor Press
- 3mm square broach
- Coping Saw (optional)
- Deck, Trucks, and Wheels - MBS Comp 95 - includes all parts of an acoustic (not electric) mountainboard
- Motors - 2x Maytech BLDC 6374 170KV sensored motors with a 10mm shaft
- Motor Mounts - Custom 3D printed MBS Matrix II Mounts
- Pulleys and Belts
- Motor Pulleys -5M 16t 10mm bore motor pulley (2 piece set)
- Wheel Pulleys -5M 72t Rockstar II wheel pulley
- Belts - at least 2x 500-5M-15 HTD belts - belt size depends on motor pulley and wheel pulley size as well as motor mounts
- Batteries -85x Samsung 25R 2500mAh 18650 Li-ion cells(10s8p = 80 cells + 5 spare) - Molicel P42a 21700 Li-ion cells are a more premium alternative - another alternative is a Li-Po battery
- Adjust accordingly to the battery and cell size as well as voltage, capacity, and discharge current if your'e using different batteries
- 18650 insulation pads (optional but safer and recommended)
- Adjust accordingly to the battery and cell size as well as voltage, capacity, and discharge current if your'e using different batteries
- Battery Management System - 10s Smart BMS (optional but very highly recommended)
- Charger - 42v 2a charger - The charger volts and current depends on your battery size and cells
- Electric Speed Controller - Vedder-based ESC Focbox Unity (now out of business) - BKB Xenith is a great replacement, or a Lacroix Stormcore for a more premium option
- Electronics Boxes
- Battery Box - Nanuk 905 waterproof hard case
- ESC Box - Pelican 1040 water resistant micro case
- Securing + Protection
- Waterproofing - PG7 Wire Glands (optional)
- Various Hardware - thread pitch does not matter so long as the screws and nuts match pitch except for the motor screws which are most likely M4
- 4x M8 x 30mm socket head
- 2x M8 x 45mm pan head
- 8x M5 x 25mm socket head
- 8x M4 x 12mm socket head
- 1/4" - 20 x 24" all thread (optional but stronger)
- 6x M8 nylon lock nut or other locking nut
- 8x M5 nylon lock nut
- 4x 1/4 - 20 standard nut (optional - needed if using all-thread)
- 4x 1/4 - 20 nylon lock nut or other locking nut (optional - needed if using all-thread)
- Anti-spark XT90-S (optional but safer)
- XT60 - an XT60 is not specifically needed but a charge port rated for 42v and at most 10a (rarely actually 10a) is needed
- In-line 10a fuse (optional but safer)
- 12AWG wire - overestimate 6' single wire - I could be wrong always have more wire than you need
- 6 sets of 4mm Bullet connectors (6 male and 6 female connectors)
- 13x 5mm ID ring terminal (optional but highly recommended if using N.E.S.E. Modules)
Step 1: Plan Your Build
Arguably the most important part of your electric board, and potentially the longest step, is the planning. If you plan out your parts properly, you should run into minimal problems, and overall have a much smoother building and riding experience. I recommend keeping all your parts in a spreadsheet with prices and part names to keep everything organized and easy to follow. I have a sample one here that you can copy and modify to your needs.
Before planning the build, it is best to understand how an electric board works. The way I like to think of an electric board is that it has 3 main components: the battery, the speed controller, and the motors/drivetrain. These are like the heart, brain, and muscle of your board respectively. The battery provides the power to the speed controller, much like the heart provides blood to the rest of the body. The speed controller receives the power from the battery and then gives both power and directions to the motors, just like the brain receiving blood and sending signals. The motors then receive the power and directions to ultimately move the board, just like your muscles. See the wiring diagram above (sourced from vesc-project) to see how these components connect.
After knowing how the board works, you need to know what you want from the board. The desired speed, torque, range, projected terrain, and ride style are all factors that will determine your components. A battery with higher voltage, typically 36 - 43.1 nominal volts, will yield a higher top speed, and a battery with a higher Ah value will increase range. A motor's KV (not kilovolts, but rpm/v. A higher KV motor has a higher top speed but requires more current to produce stronger torque. A lower KV motor would have a lower top speed but requires less current to produce stronger torque), gear ratio, and wheel size will also change the speed and torque output of your board. All of these factors can be used in an Esk8 calculator from Francesco Canessa or a more detailed Esk8 calculator from 3D Servisas to help determine what components you want to use. Just remember that as your speed increases, your torque generally decreases, and your breaking distance greatly increases as a result of them both. It is important to make sure that your battery is not too large either, that your BMS is the right size, that your motors and ESC are rated for the power output from your battery, and that everything will physically fit on the board in a nice manner. If this is not the case, the board will likely break, throw you off, and possibly catch on fire.
For electric skateboards, many people either use Li-ion or Li-Po batteries because they are some of the more energy dense batteries that are easily available. Either battery chemistry works, but I wanted to be able to fly with my battery if needed. That meant, for my country at least (the United States), that each individual battery had to be under 100 Wh (Ah * V) when fully charged. In other words, I needed to be able to take my battery apart into multiple smaller batteries. This is much easier to do with Li-ion batteries so that is what I chose to build my battery. You can also buy a pre-built battery if you are uncomfortable making your own, but pre-built batteries are almost always more expensive.
Certain electric speed controllers (ESC) have been developed more recently and optimized for electric skateboarding, being based off of Vedder-electric speed controllers (VESC) developed by Benjamin Vedder. As for the motors, BLDC motors are compatible with all VESCs and generally 6374 motors ranging from 140KV to 200KV are a good size for an EMTB. For street specific boards, smaller motors are also fine since street boards do not require as much torque. Sensored motors, typically with hall sensors, are also more efficient since they can give the angular displacement of the motor and give you a smoother motor startup. Companies such as Maytech, Flipsky, and Alien Power Systems all make pretty good motors, but look around some esk8 groups and you'll find other great motors. Those three companies may not be the best, but they're the three companies that I remember most.
Your drivetrain is also very important to the build. I chose to have an open belt drive so that I could change my gear ratio later on to fit different sized wheels if I desired. An open belt drive is much more vulnerable to debris, but it is also the easiest drivetrain for maintenance. Closed belt drives are belt drives that are encased in some form of an enclosure to be less vulnerable, but they are harder for maintenance than open belt drives. Direct gear drives, or spur gear drives, have the most efficient torque transfer between the motor and the wheel, but they are the hardest to setup, the hardest to maintain, and their gear ratios are very hard to change if that is even possible for that type of gear drive.
The deck and base of the build are also very important to the board. I knew that I wanted an electric mountainboard since I wanted to go off-road, so I chose an MBS Mountainboard as my base. Many people prefer street carvers, but still use mountainboard decks and trucks, some use drop-through decks, but it all depends on your preferred riding style and what you want from this build. The deck does greatly influence the electronics enclosure, but so does the enclosure influence the deck. The enclosure needs to securely fit onto the deck, and it protects the electronics from damage. Some people's enclosures some people separate their electronics enclosures while others use one large enclosure to encase all the electronics. I knew I needed bottom clearance on my build, so I top mounted my battery (inspired by Trampa boards) but I separated my esc into a smaller enclosure.
Aside from components and power output, it is important to plan additional modifications or components you want on your board. I personally wanted my board to waterproof, so I planned on using wire glands and minimizing the amount of holes in my enclosures that I would need to waterproof. I also planned on 3D printing custom motor mounts so I needed to start designing that. You can also plan accessories such as carrying handles, light mounts, and really anything you want, but I did not include those in my build.
To sum it all up, plan out your build so that everything fits and is compatible with the other components. Make sure your components are sized properly, and know what you want from your board. You can look at various esk8 groups for inspiration on your build as well.
Step 2: Build the Battery
The information provided in this step primarily applies if you are building your own Li-Ion battery. Regardless of battery type or construction, always be careful to never short the battery or otherwise damage it. I am using 10 x N.E.S.E. 8p modules to build my battery. If you prefer to spot-weld with nickel strips, check out Lee Wright's videos about making batteries since I have never spot-welded and it was not involved in this project. His BMS video is also really good, and he probably explains how to wire them better than I do.
For my battery, I 3D printed the main modules on a Prusa Mini and bought the N.E.S.E. hardware to make a custom sized battery. At this point, your battery size, voltage, discharge rate, and Ah should be planned and known, so now you just need to build it in the right configuration.
First, you want to check the voltage of each cell you are working with and make sure they are all within 10 mV of each other. If a cell's off by more than 10 mV then charge it or discharge it accordingly until it is close enough to the rest of the cells. Next, add insulation pads on the positive end of the cells. The pads are optional, but they decrease the chances of shorting a cell. After the pads are stuck, add a compression tab and a regular tab into the N.E.S.E. module and press fit the cells in accordingly. Make sure to keep all the cells in the same orientation in each module since these tabs connect the cells in parallel. Each module should have an indented symbol marking which end is supposed to be positive and negative. The positive terminal of each cell usually has a smaller terminal or sometimes a button head on it.
After all the modules are full, add the square nuts into the rectangular holes. Make sure the rounded edge of the nut is facing towards the cells. Then place the lids and gently screw them closed but be sure not to overtighten them. Fold the ends of the tabs that are sticking out of the modules to align them with the hole on the end. Make sure not to touch more than one tab at once. Check each module with a multimeter, and it should read the same voltage as when you measured the individual cells.
Before connecting the modules in series, prepare the balance leads from the BMS, but keep the JST disconnected from the BMS to help prevent any shorts that may happen. I chose to use ring terminals soldered to the balance leads so I can secure them with the screws on the ends of the modules, but you can also solder the balance leads to the series bars themselves (not the screws). I'd also recommend shortening the balance leads where needed to reduce the excess wires near the battery. The balance leads should connect to the positive terminal of each module, but some BMS's come with an extra balance lead (which should be black) to connect to the first module's negative terminal. I numbered my modules from negative to positive, so the module that has my main B- connection is module 1, and the module that is connected to my main B+ is module 10. Be careful, because it is easier to short the balance leads than it is the cells themselves. If you choose to solder the balance leads, make sure you have them ordered correctly and the correct length. If they are ordered incorrectly on the series connections, then they can break your BMS when you connect the JST to the BMS.
Once the balance leads are prepared, carefully add the series bars with the balance leads and secure them with the supplied screws. Connect module1+ to 2-, then 2+ to 3-, 3+ to 4-, etc. until you reach the last module in your battery. This is when the battery becomes more dangerous, because the voltage is now increasing so it's current can flow through higher resistances. When the whole battery is connected, check with a multimeter once again, from B- (1-) to each module's positive terminal. The voltage should be the individual cell voltage multiplied by the module number (nth module * V reading at the start). Again, this is the stage where the battery can easily be shorted, especially now that it has a higher voltage and the balance leads are easier to short so be careful. Once you confirmed that the series connections are correct, organize the balance leads. I used zip ties, but if you're not using an N.E.S.E. kit, you may do it differently.
Next is the main B+ and B- wires as well was the charge and discharge ports. I included a diagram above to help simplify this explanation but it does not include the balance leads. I chose to bypass my BMS on discharge for two main reasons a) high discharge BMS's are expensive and quite bulky b) I would rather run my batteries a little bit below their comfortable voltage than have my power cut out in the middle of a ride. To wire a BMS in charge-only you need to have the discharge port connected directly to the battery. That means the discharge port does not have any direct connections to the BMS. The charge port negative (C-) connects to the C- on the BMS, and the B- on the BMS is connected in parallel with the B- terminal from the battery. The C+ from the charge port connects in parallel to the B+ terminal from the battery. I recommend having an XT90-S as your discharge port since it is a great anti-spark, and an XT90 is better suited for discharge than an XT60 for a mountainboard. The charge port can by whichever port you choose, a barrel connector, anderson connector, whatever DC connector is rated for enough voltage of your battery and greater than 10a. I chose an XT60 just so that nobody could accidentally plug my charger into other devices since we do not have XT60 devices laying around the house.
After everything was wired and connected properly, I wrapped the ends of my battery that seemed the most flexible to help keep them more stable. I also used tape to secure the temperature sensors and any additional wires on my battery.
Chargers and Final Tips
Make sure your charger has the same charge port as your battery, and make sure that the charger charges at the same voltage as your maximum charge on your battery (4.2 * # of series connections). If the ports are different, it's a simple matter of soldering two wires and a little bit of heat shrink to your desired connector. Make sure you connected positive and negative wires to their proper connectors. Most chargers work just fine around 1a - 4a but you can charge faster with a higher current charger. Just be careful since a higher current or faster charger decreases battery life, but it is convenient at times. Keep in mind that almost all BMS's only balance cells at the top end of the battery. While it may not be great to store a battery at 100% charge, you do need to charge your battery all the way at least once in a while in order to keep the cells fully balanced. If you are using Li-Po batteries, I believe it is much more viable to use a balance charger and not have a BMS at all, but I could be wrong. I am not super experienced with Li-Po batteries so definitely research a bit more on them if you want to use them.
Step 3: Modify Your Electronics
This step is usually very short, or not needed entirely, but I chose to modify my electronics in order to handle a bit more current. They likely did not need these upgrades, but it adds some more security to the build and eliminates a point of failure. Sometimes your components will just have different sized connectors, so you do need to solder new connectors depending on which components you have.
ESC + Motors
My ESC came with 3.5mm bullet connectors, 14AWG wire, and an XT60 connector. I wanted to upgrade them all to 4mm bullet connectors, 12AWG wire, and an XT90 connector. This was all fairly simple, it just took some time to solder all of the components. I also needed to solder an additional wire (blue in the picture) to the positive end of the XT90 to connect to my remote receiver so it could read the voltage of my battery and give that info to my remote.
ESC + Battery
You need to make sure that your battery and ESC have the same discharge and power ports respectively. If not, you need a good way to interface them. I have a transfer cable, since my ESC and battery are in separate enclosures, to link my ESC and battery across the board. The transfer cable has an XT90 on each end so I can swap out my ESC or battery if I want to later on. This also serves as another layer of safety where I can disconnect my battery and ESC, rather than having them soldered directly to each other, if anything goes wrong.
I also had to shorten my motor sensor wires since they were very long. The JST for the sensor would not fit into the wire gland either, so I needed to cut and insert the wires from the other end of the wire gland anyway, but keep in mind any wires or cables that need to be shortened. This does add a risk of having soldered wires rather than solid wires.
This step is fairly simple, and I feel like it does not require a lot of explanation. It is mainly up to your discretion how you modify your electronics, and even then it's mostly just soldering which does not take a lot of explanation. Just be careful to not damage your electronics if you modify them.
Step 4: Prepare Your Electronics Enclosures
This step ensures that all your electronics and enclosures are ready to mount to the rest of the board, and that any external ports or buttons have holes in the enclosure and are secure. For me, that included making my enclosures waterproof. For you, it may just be checking that everything fits inside the enclosure and adding some padding. It all depends on what you wanted from your enclosure.
My ESC enclosure is a Pelican 1040 micro case, which fits my ESC with some room to spare. In order to keep my enclosures as waterproof as possible, I decided to use wire glands wherever a wire was entering the enclosure. 12 AWG wire fits into the smallest wire gland, PG7, but is the smallest wire that wire glands can consistently form a seal with. I drilled a 1/2" hole with a step bit, then just inserted the wire gland through the hole and tightened the nylon nut on the other end. I had the rubber washer on the outside of the enclosure which seems the best, but having them on the inside of the enclosure might work as well. Then, just repeat these steps for however many wire glands you need. Mine are not quite straight, but when the enclosure is attached to the board and moving it does not matter. I used the same step bit to drill a hole for my power switch, and it just fit and tightened the same as the wire glands. I also had to cut parts of my enclosure using a coping saw, then sand them down in order to add some wire glands.
After the wire glands were put in, I had to cut the rubber lining of my ESC enclosure to allow the wires to enter the enclosure, but I did not mess with the part of the lining that formed the water-tight seal. I also added two wire glands into my battery enclosure, a Nanuk 905 hard case, for the transfer cable mentioned in the previous step. I had to insert the cable before soldering the XT90 to it because the XT90 would not fit through a wire gland and form a waterproof seal at the same time.
I planned on mounting my enclosures with 3M dual-lock velcro, and a ratchet strap for my battery. This minimizes the amount of holes in my enclosures, so less areas for waterproofing to fail. I did, however, need to sand the bottom of my enclosures to make them more or less flat for the dual-lock velcro to stick well.
This step is probably the one that varies the most between people's builds. Just make sure that your ESC and battery fit into their respective enclosures, or joint enclosure if they're together. Make sure that your mounting method won't interfere with any other components, and that your enclosures can be mounted in the way you intend.
Step 5: Assemble Your Drivetrain
In this step, you assemble your drivetrain and align your motor pulleys with your wheel pulleys. If you're using spur drives this step is more complicated, so go check out Lee Wright's video since he has a lot more experience with them and explains their setup process very well. Not all spur drives are the same, but he has a video for Moon Drives and Etoxx Drives and they both have general rules you should follow when assembling spur drives. Hub and direct drive motors do not require this step since they are already attached to the wheels. This process is also easier if you either detach your truck from your deck, or have the back end of your board suspended so that you have room to work below it.
Initial Motor Mount
Properly aligning your pulleys is very important, but you must first attach your motor mounts and pulleys to their respective components. This should be an easy process, but every motor mount is different. I 3D printed custom motor mounts on a Markforged Mk2 printer using Onyx and Fiberglass, but you can usually find motor mounts that fit your trucks, or even universal motor mounts that fit a general shape/size of truck. To fit the motor mounts, you will always need to first take the wheel off the truck, then slide the mount over the axle. Some mounts use a large grub screw to attach to the truck, some use an additional clamp part, and some have built in clamps, but all are a similar process. Lightly tighten the mount so that the mount can move it side-to-side, but is still fairly snug to the truck. If the clamp is separate from the rest of the mount, you may need to tighten the clamp a bit more in order for the hole pattern to line up with the main body of the mount. Lightly tighten the mount body to the mount clamp in the same manner you tightened the clamp to the truck. Some motor mounts have adjustable angles (with respect to the ground) so adjust them according to your needs. A steeper angle will allow for greater bottom clearance but too steep of an angle could interfere with the deck while turning, so it's important to find the sweet spot in the middle.
Next the motors should be added to the motor mounts, then the pulleys to the motor shafts. The motors should have a square hole pattern, and the mounts will likely have a slotted hole pattern for belt tensioning. Simply position the motor wires towards the esc enclosure, align the motor holes with the mount holes, and add the needed screws, likely M4. The position of the motor in the slotted holes does not matter at the moment, just don't fully tighten the screws since this is not the final position of the motors.
This is the point where you need to make a decision of where to position the motor pulley on the motor shaft. I prefer to have the pulley as close to the motor mount (usually a paper's width apart) so that there is less strain on the shaft from the tension of the belt, but you could position the motor pulley so that it is more easily aligned with the wheel pulley, or if you have an idler that you need to align the pulleys with, like I did. After deciding a motor pulley position, add the motor key if you're using one (I definitely recommend a motor key to ensure your pulley will not slip under high torque loads), and if you're using circlips to secure the motor pulley, add the first circlip as well. Then slide the motor pulley over the motor shaft and be sure to align the keyways of the motor shaft and the pulley with the motor key. Add the second circlip if you're using circlips, but if not tighten the grub screws in your pulley using Loctite, I recommend temporary Loctite since some people like to change their drive setup later on with their build. I used permanent Loctite for the keyway since I will never remove the motor key.
This is where I used an arbor press to add keyways into my motor pulleys since they did not have them initially. This was accomplished with a 3mm wide high speed steel bore. After one pass, I added a shim to increase the height of the keyway until it reached slightly over 2mm, which was my desired height.
Once the motor pulley is in position and tightened, you can attach the wheel pulley to the wheel if you haven't already. This is very simple, as some pulleys press fit into the cores of wheels, and others just tighten with a few screws. Try to keep the pulleys as straight as possible since an off-center pulley will wear the belts unevenly and lower efficiency. If you're attaching the wheel pulley using screws, make sure to tighten the screws evenly, and not in a circular pattern. For example, with 5 screws, move in a star pattern, for 6 screws use a hexagon pattern, but try move in an opposite or diagonal pattern, never circular. Refer to the images above where I have the screws numbered in the order that I tightened them for my wheels.
Final Motor Mount
Now put the wheel back on the truck axle, and adjust the motor mount left or right so that the pulleys line up. You can usually eyeball the alignment, especially since most pulleys have an extra 1mm of tolerance for belt adjustment. Just to be sure, I recommend you get a straightedge and test the alignment of the pulleys. Once you get the alignment correct, you can tighten the motor mounts, whether it be the clamps or grub screws that secures them to the truck. If your motor mount consists of separate clamp and body parts, tighten the body to the clamp as well once the pulleys are aligned.
Belts and Tensioning
Once that is done, you can add your belt to the drivetrain. First, you need to loosen your motor screws so that your motors can move within their slotted holes in the mounts. Next, take off your wheel from the axle and add your belt onto the motor pulley, and under your idler if you're using one. Now put your wheel halfway onto the axle, and partially place the belt onto the top of the wheel pulley. Now spin the wheel away from the motor while gently but firmly pressing the wheel into the axle. This allows the belt to easily wrap around the whole wheel pulley without too much effort or struggle. Once the belt is fully on the wheel and the motor, you can tighten the axle nut to keep the wheel on the axle. I usually fully tighten my axle nut, then loosen it a quarter turn to allow space between the nut and the bearings.
To tighten the belts, you can place your hand between your motor and your wheel, and gently apply pressure on your motor away from the wheel. While maintaining pressure, tighten a single motor screw, whichever one is easiest to access. Test the belt tension by pressing onto the belt between the pulleys. There should be about 2-3 mm of movement if you're using a 5M (5mm pitch) belt, and no more than 1mm of movement if you're using a 3M (3mm pitch) belt. Belt tension is something that varies constantly depending on your riding style and riding conditions. You can always test and experiment with belt tension, but a both too much and too little tension can cause performance issues.
Now, repeat these steps for however many motors you are using on your board. After that, your drivetrain should be fully assembled.
Step 6: Mount the Enclosures and Electronics to the Board
This is another step that will vary greatly between different builds depending on what you want with your board. Most builds have a joint enclosure below the deck, but for a mountainboard I wanted bottom clearance so I decided to top mounting everything. In this step you will also install and connect your electronics.
Basics of Mounting
Regardless of the mounting system and position, it's always a good idea to have some sort of shock absorption between the enclosure and the deck. This reduces the vibrations experienced by your components inside your enclosures, and decreases the chances of any error. It also reduces the noise of your board and overall comfort while riding. The most common mounting system I have seen is with screws throughout the enclosure, for both top and bottom mounted enclosures.
Top and Bottom Mounted Enclosures
In large top-mounted batteries and enclosures, I have seen a lot of people use barrel skateboard bushings with screws through their center as shock-absorption. This works well, and definitely secures the enclosure so long as you use properly sized screws, nuts, washers, sized around M8. I personally used dual lock velcro with a ratchet strap so I could reduce the amount of holes in my enclosure, but also more easily adjust my enclosure if needed. If I feel the need, I could always drill and add holes later, but the velcro and strap have held up just fine so far.
For bottom mounted enclosures, some people use smaller screws that thread into the enclosure and deck from the bottom, but not through the deck. Other people use countersunk screws through the top under their griptape, and nuts/washers on the bottom of their enclosures. If you are using through-screws, for top or bottom mount, I recommend either using nylon nuts or loctite since these screws will experience a lot of vibration during use.
I cannot say a lot about mounting enclosures since each one is usually different from another, but be sure to secure your enclosure properly or else it will fall off while you're riding. As for the electronics, it's a good idea to have some sort of padding on the inside of your enclosure as an electrical insulator and vibration absorber. Your battery often times sits in the enclosure with padding since it is very hard to secure the battery to the enclosure in a proper way. You can try to use traditional velcro straps, but depending on your battery shape and size this can become very difficult. Both my battery and ESC were not secured to their enclosures because they fit the inside of their enclosures well enough, or there was enough padding, that I was confident they would not excessively move while riding.
While you're putting your electronics inside your enclosures, make sure your wires and cables are in their correct positions, and will not be pinched or otherwise damaged during the installment process. This will most likely be their final position, at least until you adjust it again, so make sure everything is installed properly. Make sure your battery wires can connect to your ESC, and that your motor wires can connect to your ESC. Some people do this through a channel in their deck, other's just have their wires "stuck" in a way to their deck, but sort of loose. I chose to have my wires, previously mentioned as a transfer cable, run through my toe binding to keep it secure, but free and adjustable.
Before completely closing your enclosures, make sure that your motors, battery, and ESC are all connected properly. I suggest connecting your battery to your ESC last, preferably with the anti-spark as the last connection. This is also where you should attach your power switch to your enclosure if you have not already. Most, if not all ESCs come with compatible power switches. This is a matter of drilling or cutting the proper hole, and installing the switch with either a screw or sometimes hot glue. It should connect with a JST on your ESC labeled "switch." You should also connect your receiver for your remote into either PPM or UART depending on which method your electronics are compatible with. I chose PPM because it is simpler and the advantages of UART are not needed for me, and do not outweigh some of the difficulties of setup in my opinion. Most receivers also connect to the positive end of your battery so they can relay your battery percentage to your remote. Next connect your motors to your ESC, most likely with an MR60 or bullet connectors, and your sensors if you're using sensors in your motors. They should have a JST located next to the motor phase wires. Some ESCs require motor phase wires in a certain order, and they are often color coded if this is the case. Most VESCs, however, can run auto-detection and can have their motor phases plugged in any order.
Step 7: Program the ESC
This step is required if you have a VESC, but is not if you have a pre-programmed ESC. This is also the step where I have the least amount of knowledge, but this is also one of the easiest steps, made easy by Benjamin Vedder's VESC tool. This tool and its firmware are constantly updating, so keep yourself informed about updates and when to implement them. He has many tutorials here, about the tool, specifically for more advanced components, but I will provide some of my own insight here. Some of my own settings at the time of this project are posted above for a reference. Values will vary between boards, and especially between people because each person has a different ride style.
First, you want to make sure your ESC is properly connected to your batteries and motor, then power it on. Connect it via usb to your computer. An android app exists for the VESC tool, but I have no experience with it so I cannot advise for it. Once the tool is launched, click auto connect in the "Welcome & Wizards" tab. Then make sure you're on the most recent firmware from the VESC tool. At the time of my build, that firmware is 5.2 from VESC tool version 3.0.0.
Next, go back to the wizards tab, and click on setup motors FOC. This is the easiest and safest way to setup your motors. Just follow the instructions in the tool, and enter the proper information such as battery type, battery voltage, battery size, and approximate motor size (a 6374 motor will be the "medium out runner ~750g"). If you have sensors in your motors, they are most likely hall sensors.
Once your motors are setup, you can navigate to the "Setup Input" button in the wizards tab. This lets you calibrate your remote's throttle to your ESC, and set tolerance for the idle position since some remotes still send some signals while idle. You can also customize your throttle curve in this step. It may not be part of the wizard, but you can navigate to the PPM or UART tab (whichever you used to connect your remote), and then the graph tab. This is probably the part of the tool that you will adjust most often, and don't be afraid to experiment with different curves.
You can additionally run HFI (High Frequency Inductance) on your motors instead of sensors. I have not used HFI a lot, so I am not sure about its comparison to hall sensors, but it is an alternative. I also do now know a lot about its setup, but there is more information from Benjamin Vedder's tutorials. You can modify some values if you believe they might be better, such as maximum battery or motor current, but I would leave them almost all values at the default values from the setup wizards.
Step 8: Test and Adjust
This is the final, and most fun step in the process. Here, everything should be setup already, so you can take the board for a light test run.
I recommend not riding at maximum speed, and definitely be careful because you do not know what the acceleration of this new board feels like yet. I recommend riding slowly and watching your components, especially your motors and mounts to see how they are aligned and if they move in any unintentional ways.
After the ride definitely check all your screws to see if they loosened due to vibration. This should be a regular practice after every ride, but especially after your initial test ride. You should be able to feel if acceleration or braking is too strong, or if anything is vibrating too much. In these cases, open up the VESC tool and adjust your acceleration curve, or anything else that might have gone wrong. Try to locate a source of vibration if there is too much, and add some soft material to dampen them. You should also be able to feel if your trucks/bushings are too tight, and you can adjust those accordingly. All these adjustments take some time to fine tune, and can be changed throughout the life of the board. Don't be afraid to experiment with some settings since you can always reverse them, just be careful to not damage anything physically or electronically. Also be careful not to crash or hurt yourself during tests and adjustments.
After this, your board is all done! At least, the base of your board is. You can always add accessories and adjustments to your board, so keep modifying it. I'd recommend to add lights and maybe a carrying strap to your board if you need them. Just remember to wear safety gear like a helmet and pads, and learn how to fall, because you will crash or at least fall at some point. This is not a question of if, but when, no matter your skill or experience level. Stay safe riding, and have fun with your new board. Definitely try to find some people in your area that ride because riding in groups (If it is safe especially with COVID-19 currently around) is more fun than alone. If you have any questions feel free to email me here and I'll do my best to respond and help out any way I can.