I built the board based on the Boardup for air travel. However, I mostly just end up using the board for extra discretion–that is, when I need to ride a board to my destination but I also need the board to be as small as possible when I get there (i.e. public transport alone or driving is not an option). This may include any of the following:
- my employer’s vendor’s office in the CBD
- really small and cramped stores
- medical facilities
- some restaurants, cafes, and pubs
- cinemas
All that said, the v3 served me well. However, it was getting long in the tooth and after having taking it to actual trips involving planes, I’ve noted some scenarios that needed addressing. While I was able to resolve these issues, compromises have been made as well. I believe, however, it was a net good in the end and these compromises were worth it for me. These would be apparent in the following paragraphs.
Introduction
I’ve been actually been dropping hints of this new build in the Pictures and Nothing Else! thread but didn’t write the build thread as I felt it wasn’t ready yet.
Now I feel that it is.
Key Specifications:
- 10S1P Molicel P45B (22.5A per side though some people say I could get away with 25A. I haven’t seen myself reach that current draw)
- Maker-X DV4S. The usual VESC programming apply.
- Spintend Uni1 remote (I got it from Maker-X though as Spintend charges shipping and it wasn’t more expensive at the time).
- e-Lofty direct drive from @frame (tl;dr – I couldn’t fit a belt/gear drive and I’ve had it with hub drives). I actually already used this in v3.
- Boosted 105 clones from Tynee
NB: I’m aware that the Linky v2 exists. However, aside from being expensive AND still in the crowdfunding stage as of this writing, it’s FWD and I think it would be challenging when something breaks. Plus I made some design decisions that this doesn’t have. Building my own folding board would still give me the board that would best suit my needs…hence a fourth version.
Physical Form
I previously heat-formed ABS enclosures but found that flanges tend to crack eventually. I also wanted to try my hand at making fiberglass enclosures.
Also note that I got a brand new deck; the original deck already went through three different versions. I’ve drilled too many holes already and I can only patch them so many number of times.
I played around with how I can fit the components on the deck. I used a lot of tape, cardboard, and clay.
I also decided to use threaded inserts for this version. I want to make it relatively easier to remove the battery enclosure. That will not be discussed here however; inserts have already been discussed at length in other threads. Bolt-through was just troublesome and not to mention, requires two tools instead of one.
However, the precision needed for something this compact when folded and me, not having some tools for full, proper fiberglass enclosure creation, I decided to do a layup over 3D printed inner shells. Here’s the work-in-progress enclosures for an initial fit test after making the enclosures. It didn’t look too shabby after painting. Why orange? I just need to use my orange filament and the insides of the enclosures won’t be visible on the board anyway.
I also installed a strip of steel on the tail; standing a board on its tail tends to chew up the wood.
I stuck with the blue/black color scheme (I think it’s subtle enough and wouldn’t stand out too much for something built to be discreet).
For an extra special touch, here are some glyphs; bonus points for people who could translate this.
I also continued to use soft-touch grip tape. I chose this brand as its readily available in stores and I wouldn’t have to trawl the internet or import it for eventual replacements. Conventional grip tape is too abrasive and tends to eventually ruin clothes, something I wouldn’t want to happen even while the board is folded when being carried. I would also be friendlier to backpacks in which I would put this board. Yes, this board fits large backpacks when folded.
Battery and Range
Previous versions used 18650 cells which made the battery enclosure bulky for their available discharge (e.g. 25R cells). I wanted to use 21700 cells so I can get away with more current draw with fewer cells.
Granted, the cells are bigger but I came up with an unorthodox way to get range while making it as slim as possible: Use four packs of 5S1P each.
Why this configuration?
- Each pack would be 81Wh which is below the 99Wh limit I can bring into a plane as carry-on without being asked questions.
- I can put two packs in the board for 10S1P. I’ve noticed that I rarely need to go faster and 10S is plenty fast enough in exploring a new city. I also couldn’t work out how to fit 12S in the space that I have. The Boardup is really difficult to fit things into.
- I also noticed I rarely used 200 Wh per ride. If I’m riding in a new city, I’ll probably be making plenty of stops anyway. I can either stop to charge (while in a cafe or restaurant perhaps) or swap out the spent packs with the other two.
Initial cell and BMS layout exploration within the battery enclosure:
The specifications, as far as the battery is concerned, are:
- Molicel P45B (P50B weren’t readily available to me in Australia at the time).
- Daly BMS (36V Li-ion, 15A). It’s 1P so I shouldn’t go beyond 13.5A anyway. Moever, I only intend to charge at 4A max. This is one of the smallest BMS’s I could get without spending so much.
- Barrel port for charging. I figured it’s easier to find a barrel port or plug in case something happens while I’m away from home. The charging port is fused, of course.
What it looks inside the battery enclosure–the packs are held in place with foam spacers and some nylon straps with heavy duty velcro to somewhat hold the weight onto the deck instead of just relying on the M5 bolts.
More on the extra circuitry later.
I also added a plate just to keep wires in place when affixing the enclosure; this is meant to be opened anywhere to install batteries after a flight or replacing them with fresh packs after using them up.
The wiring harness for the BMS to the battery packs:
I used an XT90-S for the final connection of the combined battery assembly to the ESC. I noticed that connecting a battery to the DV4S would always pop. An anti-spark would prevent that.
I also created a 3D printed enclosure for the spare packs so I can charge them by themselves without using a separate balance charger. I can also use it as power bank.
I used a JBD smart BMS (because why not) and this 36V input capable USB output module. It has both USB A and USB C-PD; however, it’s only 65W as I couldn’t find a 100W module at the time.
After swapping out the packs and I’m not somewhere with an AC outlet, I can also charge the spare packs using a 100W power bank (which I already have) with an adapter I previously built.
(That BKB Voyager remote is not used on this project.)
Here’s the said adapter (in a new enclosure) connected to the spare pack. I probably wouldn’t charge the board this way though as it’s only rated 65W (and we all know that’s only the theoretical max). The adapter is configured for 2A; any lower and charging takes too long.
I was spray painting the enclosure but ran out of paint mid way. I wasn’t willing to buy a new can and just decided to draw some art using a paint pen.
Terrain Capability
Because previous versions used hub drives, I could only use 90mm wheels max and therefore designed the geometry and layout accordingly for those versions.
However, after having taking the board to various cities, of which I’m unfamiliar with, 90mm was simply too small and thus lead to too jarring a ride on bad terrain. I would encounter all sorts of cracks, bumps, rough pavement, and cobblestones. The rattling just got too much and the vibrations would probably have been detrimental to the board anyway (like it did on this cycling path in Brisbane). Being in an unfamiliar city and playing tourist would likely mean having to go through rough surfaces and I simply needed to use bigger wheels even if the board was heavier. Spoiler alert, this build ended up weighing 9 kg with the bigger wheels and direct drive even if there were fewer cells. It doesn’t feel too heavy anyway as it’s quite carriable folded.
I first tried playing with the placement with 97mm:
I still used a custom wedge riser to push the front trucks slightly forward.
However, the boardup has two sets of holes for the rear trucks. I was actually using rear-most holes all this time. But since I would have redesigned the enclosures anyway (and hence changing the layout), I used the inner holes instead to fit bigger wheels. I could now use > 100 mm wheels, the biggest I think I can get away for a relatively small board for shit surfaces, not to mention the famed Boosted 105 (or its clones) for extra shock absorption. Note that these are actually 102 mm; the Madwheelz v2 are true 105 mm (I have both and I measured them). 102 mm are already a tight fit; 105 would be more challenging and heavier too.
Yes, I painted the wheels to match my chosen color scheme.
Lighting
Now, some people insist that on-body lights are enough but I already have those (including an accelerometer equipped brake light). I still want on board lights for me to be seen. I think they’re also called positional lights.
Also, I hated that I have to pack and charge extra things when travelling.
I was previously using some standalone lights (e.g. Shredlights) but I find it tedious to turn them on or off individually. Also, I actually had a rear light fall off while I was visiting a different city.
Since I’m already using on-body lights, I don’t need the on-board lights to be very bright. I just need them to be bright enough so I chose to use some 5V COB LED strips: I installed them on the enclosure instead of on deck to avoid convoluted wiring from the enclosures to the lights.
I eventually covered them with clear coat/lacquer for extra protection.
I used a buck converter to bring down the battery voltage to 5V using this Pololu buck converter. Check your current draws accordingly if you want to do this.
The buck converter only turns on when the ESC powers up, using an unused 5V line (e.g. CAN) on the ESC. I also used some MOSFET modules to turn on the lights and horn from the remote’s receiver. The Spintend Uni1 remote actually has lines to control these. I just soldered some diodes to prevent frying the modules due to potential inductive loads (FYI, I used 1N5408 diodes. They’re readily available to me when I first found out about inductive loads the hard way when I was installing a similar circuitry on a different board).
In retrospect, I could have just designed my own PCB but those would have to come from anywhere but Australia and I no longer looked into finding such a local service. I already came up with this circuitry and I knew it works.
This is the extra circuitry in the battery enclosure I mentioned earlier.
And an extra…a horn
I used a piezo buzzer with a 3D printed amplifier and enclosure. This is cheaper, simpler, and doesn’t need extra electronics. This is actually mounted behind the front riser, outside the enclosure so that the sound is not muffled. It’s not as loud as the two I used for my other board but I have a bell with me anyway so I’m not too concerned. I’ll probably change this later on but I don’t feel a pressing need to do so yet. I used some metal contacts on the deck and on the enclosure that will press against each other when the enclosure is installed which completes the circuit to it. A signal from the remote can then activate it.
Note though that this is controlled by the remote receiver/ESC which is in the other enclosure.
Here’s a clip during testing of this subsystem. Note that the wires between the battery and ESC enclosures include 36V power, 5V power, control lines for the buck converter, and MOSFETs.
First charging test:
If this thread were a video, these would be the B-roll. As usual, some issues may arise during use and they will be addressed when they do.
Thanks and may I see you on the streets if I visit your city.