aka the worst thing that I’ve ever built, perhaps the worst thing on this forum, and I love it.
Doesn’t look too bad, right? The curse is in the details…
I never would’ve done this if I had any idea how much work it would take. This was supposed to be a fun, 2-week max, throw parts together kind of project. It ended up taking me months and probably 60+ hours of work to build.
Why? The story
I wanted to race and attend The 2025 Mini PEV Games in Toronto. It’s a super tight, short track.
My Tynee Explorer;
would be perfect for this race, but esk8’s are required to be less the 34" in length, and the Tynee Explorer is significantly longer then that.
None of my boards fit the max length requirement, so I’d have to purpose build one for the event.
notably the kind folks of erideracing DID offer me boards that I could race, but any excuse to build a weird esk8 is a good one
Backing up a bit- The start
I love my tynee explorer, it’s my go-to for everyday short distance travel and moving stuff to/from my car. For $1000 new, it’s a deal.
(writeup about that board over here)
However, after 3000 miles (I think, IDK, I’ve fried like 6 esc’s at this point so don’t have odometry), the battery struggled to take me further then 8 miles on a charge (It was able to do 20+ when I got it new). It battery needed a battery replacement.
A replacement 12s4p battery from Tynee is $700… basically the cost of a whole new board! Not worth it. So I found someone selling there new-er Tynee on Facebook marketplace for less then the cost of a new battery. Swapped the new-er battery onto my board, significantly improving it’s battery life. And now I’ve got all these spare parts too. Score!
Donor board(Bottom), Mine(top)
Figuring out the deck
Around the time I was considering building a board for the Mini PEV games, I had the full drivetrain from the donor board sitting on a shelf. I threw them on a shortboard deck that I had;
But I wasn’t feeling it. TOO short and narrow.
Then I remembered- I’ve had to replace my original tynee deck twice because they cracked in the same spot, in the same way.
I turned one of them into a cat shelf,
but the other one was just sitting, unused. This is when the intrustive thoughts started.
What if I just made the Tynee explorer… fit the 34" requirement?
It begins
After some quick brainstorming,
I drilled some holes.
And it actually felt pretty damn good.
the deck was sliced apart with a jigsaw later to cut off the delaminated bits and add some wheel clearance,
Added holes for drop-through mounting, hoping to lower the standing platform and make this half-decent to race.
Notably i forgot about the now curved front when I sized the holes, so the truck doesn’t sit flat on top. Cursed.
With some encouraging words from my peers,
I fully committed to the meme project by christened the board with a sharpie.
The joys of SR125 Scope Creep
I really wanted an excuse to try out Radium’s SR125 wheels. They’re basically Madwheelz but made from rubber. They should be pretty good on the polished concrete surface that the Mini PEV games takes place on, so I bough a set!
They… wouldn’t just fit on the board. That’d be too easy.
Amongst other issues, the 35mm long axles on the Tynee trucks are too short for the bearing spacing in the Radium Core. Not enough space for the second bearing, forget about the nut.
Not radium’s fault- It’s on me for having this weird ass use case
@Ac53n came to the rescue and pointed out these xcell axle sleeves, which thread over an 8mm axle, turning it into a longer 12mm one.
Put em on with some red locktite
They work perfectly! Also did a second round of deck cutting to give clearance for the new wheels.
The front wheels are attached! The rear is another story.
The rear trucks have a additional 10mm step, intended to allow the wheel pully to have a bearing to alleviate stress.
The xcell adaptors know about this, and have a rear variant that includes this 10mm step(middle)
However, this would push the Radium core out, making the belt pullys no longer aligned. I can’t move the motor mounts because they’re welded to the truck.
So I opted to just use the 10mm section.
I couldn’t be bothered to make a CAD model to show what I mean, so here’s a crappy MSPaint cross section
TLDR;
This board has three different bearing sizes (8mm/10mm/12mm ID x 28mm OD).
12mm axle nut in the front, 8mm in the back.
Cursed and glorious
ESC Mounting
With the plan to reuse the stock ESC, I started making a CAD model to 3D print a mount. The ESC has some complex geometry like angles, curves, offset screw mounts, etc.
Then I looked over at my old Tynee battery enclosure, and realized I could just copy that esc segment, exactly.
After fiddling with calipers for a few seconds, I realized there was an even simpler solution
Amazing
In the process of manhandling the ESC, I damaged some sensor wires
So I cut off the connector and re-crimped a new one onto both motors.
Now for the battery (aka the hard part)
With the board now having a shorter wheelbase and trucks mounted where the battery used to go, the stock battery wouldn’t work. Additionally, because I’ll be flying out to Toronto for the Mini-PEV games, the battery would need to be flight-safe/approved.
I’d need to come up with a custom solution.
The original plan
I was thinking I could cut apart and turn my old explorer pack into a travel pack, but got some sage advice and decided against it.
In hindsight, this might’ve been easier. 
Introducing, my Kaly. This basically-DIY board I bought used when I was first getting into racing, before I was a chronic esk8.news forum user, and is what I learned all my track fundamentals on.
It had a 1 7/8" trailer hitch on the back (a dumb project that got lost in the wind. Maybe I’ll come back to it at some point)
It had a weird-ass battery setup. 12s6p brick pack on top, paralleled with a 12s4p pack on the bottom.
For the reasons below, I was never going to ride this board again.
quote from Nothing Fancy’s thread;
All of it’s parts have been repurposed into other projects, except for the bottom 12s4p battery.
So, the game plan is to convert this pack into a compatible form factor, making it flight-safe in the process! Separate each p-group by cutting apart the PCB, making 12x 1s4p modules that I could then wire in series.
The enclosure that this came out of is basically toast, being held entirely together with tape and zip ties(so I don’t feel bad doing what I’m about to do).
Editor’s note: Part of this reason of repurposing another pack was to gain experience building a flight safe, modular battery pack without having to spend (much) money. Currently considering building a “proper” liion flight-race-pack for racing Ankle Wreacher, so this was great experience before going try-hard on the design for that pack
The conversion begins
Thanks John for lending me your garage and cooking amazing food during this 6 hour process.
This section really gets into battery building weeds, so don’t feel bad if you jump past it.
Immediately I identified two issues with my plan:
(not including “why tf are you doing this”)
Issue A) Instead of folding the nickel individually, Whoever assembled the pack saved time by welding the tabs of some series cells on top of eachother. When I cut the PCB apart to separate these two groups, they won’t come apart cleanly because they’d still be attached with the nickel, so I’ll need to cut the nickel then re-spot weld it to the PCB after the fact.
Issue B) Don’t forget that this is a battery, so I’m working with live voltage! Part of the PCB is balance traces that connect each P-group to the BMS (seen in the picture above to the left of the nickel). I couldn’t cut across those without running the risk of shorting between them. I thought I’d be able solve this by cutting the traces where the connected to pad with the nickel(“de-energizing” them), but nope! Whoever designed the pcb put these traces on the top AND bottom layers.
Battery design critique
I don’t know much, but I was shocked when I saw this in the PCB. If the battery cells vibrated against the PCB and wore through the cell wrap and PCB insulation, there’d direct shorts inside the battery. Especially considering that the cells were only attached to the PCB via the nickel (no hot glue/silicone)
Maybe PCB solder mask is fine to trust like this? idk, would love to hear what battery builder’s opinion about this.
I solved issue B by being very methodical with my order of operations. By starting from the side furthest from the BMS connector, I could cut the end, severing the centermost trace.
Then, I could cut the pack lengthwise, severing the connection between one side of cells and the BMS traces
Then, by cutting the groups apart one at a time from the side furthest from the BMS connector, there’d only be one BMS trace that’d be energized at a time, eliminating the risk of a short.
Many, many hours of precise work later
Now that they were all separated, I went back through and cut off excess PCB and sanded the edges to be smooth.
Ex. Before and after
Now that I had the SR125’s mounted, I did a 3rd and final round of cutting sections out of the deck while I was making a mess of John’s garage.
I guess the name of the board is now ,NEE Curse.
Caternmission
Building the battery back together
Another pack construction deficiency I noticed was that the cells didn’t have fish paper on the positive cell terminals. I had a bunch of 21700 4p rings left over from the build of Nothing Fancy’s battery,
so I spent the time to cut slots and insert them below the welded nickel.
Oh, also, this pack uses NCR20700B cells. There are an uncommon 20mm diameter (instead of the more common 21mm), so the fish paper rings were actually to far spaced apart to be put under all as one. I had to cut each one out and insert individually
Cursed solution, but definitely better then nothing 
Also added hot glue to directly attach the cells to the PCB to hopefully avoid vibration stressing the nickel
With the 12 modules in hand, I started to mess around with where/how to actually mount them to the deck, making sure that this plan would actually work
Mentioned above as Issue A, I had to cut the nickel in a bunch of places. I cut some nickel strip and spot welded new connections.
Spot welder tanget
I bought a kWeld from @BenjaminF, this was my first time using it! Worked great, except I had a lot of trouble getting the fancy 60A power supply to work.
Only needed to do a couple welds, so I ended up just using my chinesium adjustable power supply.
Felt…wrong.
Ain’t pretty, but it’ll work
Soldering on XT60 leads
Printed up some nice professional-looking labels, added protection for wires that wrap around the PCB, and secured them with kapton tape.
Clear heat shrink
x12
Modules done!
Wiring Harness
Aaaand this is where the project sat for like 10 days because this is the part that was going to suck.
Started to prototype the 3D printed enclosure, and I have very little room for the interconnects.
So I distracted myself by putting adhesive foam onto the packs to increase the friction between them and try and protect them, at least a little bit.
Finally got around to building the harness.
It needs to have 12x battery connectors (XT60s), BMS connector, charge port(XT60), and ESC connector(XT60). No way to do it neatly.
Some of the XT60s were pretty complicated, like the negative-most battery connector. It got BMS wires(2x 22awg), charger negative(16awg), and the main current path wire (2x 12 awg)
Basically done, just missing the charger port and esc connector
Louie was an instrumental part of motivation
After multiple printed prototypes, I printed the final enclosure out of PC. It’s a two piece print. I attached together with epoxy (I was feeling too fancy for hot glue)
Yuck
Some misc foam to fill the voids, and 2" Kapton to hold it all together.
yuck
Plug it in…
No fire! 
Standing on the TKP trucks from the donor board, I wasn’t confident that It’d be able to make it around the tight corners of the course.
Tynee sells DKP baseplate for $50, so I bought a set to replace the TKP geometry.
Upgraded the bushings with whatever I had in my misc bushing box, and it feels fantastic. Blows my socks off.
don’t ask what they are, I’ve got no idea lol.
Waiting on new belts to arrive tonight, so haven’t gotten a chance to ride her yet. I leave for Toronto in two weeks, so hopefully that’s enough time to get her race-ready!
Enclosure buttoned up, Look how clean, perfect and innocent she looks.
Almost looks like a normal build.
