Elite Sportster - Unity | TKP | 12S4P P42A | eboosted | 110s

Currently in progress. I have been acquiring parts for this build over the last few months and its finally coming together.

Components:

  • Bustin Sporster 35"
  • Unity with VESC FW 5 and METR unity module
  • @Eboosted MK3 enclosure
  • 12S4P Molicelli P42A
  • SR TKP’s with SR adjustable baseplates
  • @Boardnamics fixed axles (effective hanger length is 225mm - 24mm per side)
  • @Psychotiller quick plates and TKP clamps
  • Maytech 6365 170 or 190 kv, currently TB6355 190kv
  • @Boardnamics 40T kegel Pulleys, @Janux-esk8 15T motor pulleys (290 15mm belts)
  • @torqueboards TB110 74A
  • Hoyt Puck

I kick pushed this board around for a bit on the TKPs and the TB110s which honestly wasn’t bad. Absolutely love the deck and the SR TKPs really drop the wheels in the perfect spot in the deck.

I was considering making an enclosure to maximize the space I had for a decent size battery while staying single stack. Alan did such a nice job on the bustin enclosure that I decided to pick one up and save the work.
I ultimately decided to go with the MK3 version which has cable channels down to the baseplates. Heres where my first challenge occurred. So the MK3 tunnels go all the way to the back edge of an RKP baseplate that is mounted in the furthest holes from center.


Theres Alans build

The SR TKP bushing seat was already a problem with the MK3. The SR Adjustable TKP baseplates created even more interference because they are longer. The adjustable baseplates cover all 4 holes on the deck.
I picked up the adjustable baseplates for two reasons. One, they will raise the ride height which this low pig needed on the 110s and stock TKP baseplates. Philly streets are rough as is my riding style. Second was the ability to drop the rear hanger angle a bit. This will be my first board with TKPs so stability improvements in geometry should be helpful. Also had to file a smidge of the cutout to get the baseplate all the way into the channel so the bolts would line up. Currently have some Krank 95A barrels in there. You can see the baseplates are longer. This actually made a noticeable impact the the flex feeling of the board just because the baseplate mounting point moved inward slightly from the original baseplates that fall a hole shorter.


After a bit of trimming with the dremmel and a file we had a rough shape. I’ll be sealing the enclosure behind this so I’m not worried about it. Will use some rubber channel to clean up the edges around the baseplate. The only pic I have at this point was this one in progress check.
Anytime the enclosure isn’t flat and moves around the shape of the deck, its very important to have the gasket installed that you will be using. If you have to use a thicker gasket later, your holes may not line up. As the enclosure moves away the alignment of the holes is lost because they’re on an angle with the sides of the deck.

Returning from a week at the beach I went back to work. there, I discovered bulkbattery.com was carrying P42A cells at $4.80 ea delivered. Ordered up what I needed for this build and another. If you’re wondering, the order was shipped direct from 18650store who is an authorized Molicelli distributor. They were waiting for me at home.

Next up, I had picked up a unity heatsink from @3DServisas at the beginning of the pandemic for this build. While I dont expect to overheat the unity running on thane, ya gotta admit they look cool AF.
Im building all of this out of a 1BR apartment in Philly so my tooling is limited. To cut the hole as precise as possible, I 3D printed some jigs to use a flush cut router bit with.
First I marked the center and test fit the heat sink with the P groups. Space inside the pocket of the enclosure is very very limited. The heatsink had to be all the way against the back of the pocket and i had to sand the fillet a bit to get it sitting flat here. I picked my spot and drilled the heatsink mounting holes. Once I placed the heatsink onto the enclosure it was clear the center mark I made was not centered. This is a pain on a surface with nothing but round edges. I corrected my mistake and will fix the holes with some epoxy and FG.
inside the enclosure was very snug.

The 3D printed jig I made. One I mark everything and drill the mounting holes, I will bolt the jig in place on the inside and follow it with a router with a flush cut bit.


Marks laid out. Sorry @eboosted, damn thing landed right in the middle of the logo

One the holes were drilled I check center by bolting the heatsink to the outside of the enclosure and measuring and giving it a few looks from a distance. Then the heatsink came off, the jig for the bearing of the flush bit was placed on the inside and bolted through from the jig on the outside. The outer jig gives the router a nice flat surface to run across as I would have been running out of base to move the router on in some areas during the cut. The outer pieces also had easy to align center marks to make sure I didn’t twist it or get it out of square. Once the outer jig was aligned, I used the bolt holes to bolt it through the enclosure and through the inside jig. I hot glued the jigs to the enclosure as well to keep things in place.

Perfect! Literally snaps into place. Ill seal it once I fix the missed screw holes and fill the logo. Screw holes are easy to fix. A messed up hole would not be.

Good thing my main battery terminals wont be right next to this piece of aluminum


I had dropped the cells into the enclosure with the unity and used some modeling clay to get an idea how much space I had between the deck and the components. I pressed the deck down onto this setup and was left with something measurable.

The above photo was taken before the heatsink was installed. Prior to the heatsink going in, I had just 5mm between the unity and the deck at the narrowest point. Each of the cells groups had roughly 4mm of space. This was with no gasket on the enclosure.
Already Im thinking about how Im going to handle this. The 3DS heatsink for the Unity has raised it 4mm off the base of the enclosure so I now have 1mm of space left before the deck – with a gasket in place I’ll get some back. However, it wont be enough for the 10mm thick BMS that needs to fit in here above the unity. Ill come back to this in a bit

I got to work on the battery. P42As are rated to 40 amp burst with temperature control and have remained temperature controllable around 30 amps. I dont intend to run a urethane board at 100+ amps continuous. However, I’ll build the pack to support the amps its capable of.
First the P groups were glued up using high temp got glue. This stuff from gorilla glue doesnt peel off, it will tear the cell shrink wrap if you make a mistake.
Hot glue, fiberglass tape around the whole P group.


Added fishpaper rings to the positive terminals and applied adhesive fishpaper from 145PTags.

For nickel, I cut down some 50mm wide 0.2 strip into 74 mm x25 mm pieces and rounded the corners with the infamous corner chompers. Both those and a paper guillotine cutter made this go much faster than scissors. 0.2mm x7mm nickel is good at 13 amps oiptimal, acceptable at 20 and hot at 27. The strip is 10.5 times wider than that so those values scale. 130 amps optimal, 200 acceptable, 270 hot. More than sufficient for a battery I will likely set at 80 amps and rarely turn up to 100. After this I added adhesive fishpaper pieces that covered the terminals at both ends of the group and only left the bent over strip on top exposed.


In hindsight, I wish I had notched the nickel above the cells so that there was a gap through the center of the pack from end to end. This would allow the BMS wires to run up through there without resting on the nickel. But this will work out fine.

So at this point, im realizing that I screwed myself. The Unity heatsink has eliminated valuable height in the enclosure and I didnt check before putting the holes in the deck. Theres not enough room for even a D140 BMS in the enclosure without at least a 1/4" or taller gasket (and thats once compressed). And I have a bluetooth BMS from @thisguyhere that is 10mm thick I would prefer to use. Further more, the distance the enclosure has to move away from the board is creating some issues with my enclosure bolt hole alignment now.

For one, I used m4 insert and I did not drill all the way through the deck. I used the steel version which are only 5mm long. However, because they are shorter (the deck is 12mm), they grip less wood and I was feeling nervous about their longevity given the weight of the enclosure. Plus, now theyre not lining up well because I installed the enclosure with an 1/8" gasket and now I need a 1/2" one. I tried to remedy this with the through the deck inserts that eboosted provides, but was still having alignment issues. Also thinking that tall gaskets suck and look like poop and cutting a pocket in the deck is tough because the deck is already thin.
What I decided to do was go all out. I pulled my spare maple veneer fand bag from Roarockit out. I stripped the board, removed the inserts and made a plan.

I had a deck snap behind the front truck and toss me to the ground that was drop though. I prefer to reinforce these areas, especially on split tongue decks. ESK8 puts a lot more stress on these decks than the average kick pusher does.
My plan is simple, Lay up several layers of 1/16" veneer to the bottom of the deck and then rout a larger pocket from the center. This will add thickness to the deck allowing me to more safely create the pocket size I need to clear the BMS and internal components. I’ll reinforce this area with FG when its finished up. This will allow me to continue to use a thin enclosure and preserve external aesthetics.
Stripped. Will add 3-4 layers (4.5-6 mm) to the bottom and one (1.5mm) to the top (after installation of through the deck hardware which will then be hidden). I may skip that step if I skin it. Cutting the large battery pocket out will help to keep the board from getting too stiff from the extra thickness.


A small tongue and drop down reinforcement with fiberglass went down first and then the first layer of crossband veneer went over it. Crossband has the grain running perpendicular to the length of the board and will have virtually no impact on flex in the length. The first two layers are cross band. Into the vacuum bag the assembly went. I did need to add clamps to the outside to pull the veneer to the deck at the drop downs.

I used West Systems epoxy with 206 hardener and a bit of black dye so I could see it better after drying.This has the third piece in the bag right now. Im doing a lot of sanding and work in between. Tapering the edges beyond the enclosure to keep the deck appearing thin from next to it. Additionally, this third layer only covers the bottom of the deck and i will blend it in to the start of the drop down. The final layer will cover the whole bottom of the deck end to end. Basically the 1st and 2nd layers and well sanded towards the ends of the drop down and the 3rd layer doesnt even go there. This prevents me from over stiffening the tongue and drop down which contribute to the flex of the deck. Ill remember to take some photos tomorrow when im prepping this for the final layer.

Next up and the part of this project im both most excited about and most proud of. During the last few months, Ive been running a COVID medical equipment volunteer team making faceshields. During that time, I got a lot of exposure to Smooth On products as well as just general molding and casting with silicone and urethane resins.

Within the enclosure, I wanted to accomplish a few things. I needed to figure out how I wanted to secure the P groups in place. I also had the idea to coat the inside of the enclosure with something rubberized to reduce the hollow sounds it can make and amplify little stones and other things. If it kills me, this board will be rattle free and ride as nice as a urethane board can. Finally. a flexible pocket the P group could sit in would reduce vibrations and shock that the cells are constantly hit by - especially on a thane board in philly streets.
I looked around and found very very little about potting electronics with something like this. Sure, you can pot electronics with epoxy, silicone, urethanes etc. But I was also concerned about a permenant solution that eliminated my ability to service the battery if needed.
I considered some materials like MG 834fx a flame retardent, thermally conductive and dielectric flexible epoxy. It was a bit pricey, but I was concerned that given its epoxy base it would be firmer than what Im imagining. Its main advantage was that it was a thermal conductor - where as all urethanes and silicones are going to be thermal insulators.
I settled on a urethane rubber compound from smooth on called Vytaflex 50 - a 50A shore hardness urethane. I determined the volume required and ordered some up.
The full cure time is long at 16 hours, but you can demold after 8. I dont have a vacuum degasser so there are a few bubbles but it does clear well on its own in general.
I sketch up in CAD the 2S4P groups in each channel and 3D printed two plugs. They have a small 2mm protrusion on the bottom that sets them up off the base of the enclosure to provide some rubber under the groups as well. I had the extra overhead space since I was doing all this deck work anyways. I sanded it to 400 grit and coated them with universal mold release from smooth on. I clamped them into place in the enclosure and poured in the liquid urethane using some black dye to tint it. Heres where I’m at tonight. Theres a few P groups installed to show you how it works. I can flip the enclosure upside down and they stay put. If the centers are held down they cant fall out. They fit snugly and the rubber is nice and soft. You can see one of the plugs I printed sitting in the large front channel. The 5.5x2.1 mm charge port wiring is protruding from in front of it.


Really happy how this is coming along.

Thats enough for tonight. more updates tomorrow.

Also, still looking for inspiration in the form of a name/theme and skin idea for the top. Happy to hear ideas

still working

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hell yeah dude, very similar to a build I’m working on. That looks like it’s a lot of fun, is it still in progress or on the street yet?. How are the TKP’s above 20mph? Do they get squirrely at all on you? What angles on the baseplates are you running? Dope that you can fit 12s4p in there of the molicells

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I’ve had a set of SR TKP waiting for the right build…be interested to see how this works out on the sportster deck at speed.

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Very sexy and great choice of parts. Following!

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I wouldn’t be too worried since the anodizing makes it pretty much non-conductive.

Looking great so far! :+1:

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Well thats good to know, I wasnt aware of that. Regardless, theres fishpaper and urethane rubber to keep them from interacting.

@whaddys not on the street yet, @Adam0311 im waiting for the same. I built a battery for a local guy who runs a red ember top mounted on stock TKPs and routinely runs 35mph. I just pulled his SR setup for Kahua trucks and AVX gear drives but he never had a complaint about them. The adjustable baseplates gave me a much needed 1/2" of ride height and I can essentially copy the HEXL trucks that people swore by. I rode his TKP setup to 25 mph and had no issues, The turning radius and the carving is unreal on TKPs. Im not a super high speed fan so I think they will work out. Im anxious to see how twichy they are off center at speed

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sweet board!
Loving your use of old skool and technology
@b264 check out the cool use of 1/2 potting the battery!!

definitely following!

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Potting batteries is on my to-do list and getting close to the top. Very nice!

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Last pour of the night. One more section to do after I touch up the epoxy.

How’s this for a crazy thought. Would rubber like this have an impact on ride comfort if I routed a 3 mm deep pocket where your feet go, poured a flat pad of urethane and then laminated over it with a veneer? :man_shrugging:t2:

@b264 Definitely look at that MG chemicals 834fx. As a thermal conductor that’s pretty cool for cells- pun intended.
Serviceability was key here. If I did it again, I’d bury a retention strap or something under them that came out of the urethane on the sides. It’s not an easy compound to glue to or mess with after the pour. Creating a retention system for these will be tough now. Although compression against foam on the deck side isn’t out of the question and they’re nice and snug in those spots.

I’m also planning a few more items with this urethane. Maybe a riser pad, enclosure gasket or a rear phase wires connection plug/gasket etc.

Tbh, theres likely harder urethane resins that could be used to make entire enclosures. Sporting flexibility, strength and high abrasion resistance, especially compared to FG.

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I love to see this kind of work and dedication on the forum, you are truly an artist!

It’s coming along amazing, mad props to you, you will love this board to death

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We’ve had some discussions here in the past, but consider just running balance wires to a JST and a charge cable, keep the BMS outside the board, let the ESC handle the cutoffs and current control. Just hookup BMS as needed to balance and/or charge if you don’t have a CC/CV charger. Save weight, space, and a major point of potential failure and resistance losses by not pushing amperage through the BMS when the ESC is ultimately the component designed to handle current control. Just a thought. I know a lot of guys don’t feel safe without a BMS on board, but I don’t trust any of them for this application personally.

Awesome looking build, very sleek! You guys are making me want to build a slim street board!

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Fantastic write-up, very interesting! :smiley: I’m surprised you decided to go all out and add more thickness to the deck; if I were you I would have just tossed out a single p-group and used the board at 11s :laughing:

Also, what’s wrong with using regular foam to keep the batteries from rattling?

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Appreciate it. The BMS will be wired for charge only so I’m not running main current through it — if a BMS even exists that could do that at these amps and not be half the board in size.
I considered an external balancer but I’m not quite there yet. Not to mention I just bought a new BMS and an 8A charger.

There will be a GX16-2 plug at the tail of the board for my 8 amp charger and a 5.5x2.1 at the front to use up to 4 amps on. This lets me pick up nearly every one arounds charger and be able to connect.

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Regular foam works too. Getting the right foam is important for certain areas.

Honestly I got the idea while working with the silicone molds and just wanted to try it. The ebike world pots batteries more frequently. I loved the idea of a thermally conductive compound surrounding the battery. It would never be able to absorb enough thermal energy to keep them cool, but it would likely soften the temperature spikes during load.
However, now that this idea is finally a reality, it actually worked really well. The P groups are stuck in place and don’t require Velcro or anything to hold them in. This should greatly reduce shock and vibrations to the P groups and isolated them from rubbing on the enclosure and such. Foam in the enclosure keeps things from moving, but if they’re just laying on the bottom of the enclosure they’re vibrating with the whole board.

Not to mention, applying a rubber like this greatly reduces the sounds the fiberglass makes. It’s essentially a hollow shell on the board so rocks and items make more noise hitting them. It’s gonna do the same thing sound deadening spray would.

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so so interested where this takes you and your findings…

just thinking aloud about your science…
I’m wondering if you inverted the urethane pour so it only covered your wiring, the top of your cells and that was affixed to the underside of the deck, then the MG 834fx poured over the top, actually the bottom of the cells in the form of the enclosure, making the thermally conductive element act as the enclosure, but still allowing a bit of maintenance and replacement of a bad P-group… you’d probably lose the bad P-group in the process and have to replace that entire element.

I have no idea of the abrasion resistance of the MG 834fx, and it’s durability using it as the enclosure, nor do I have any idea of how the epoxy would would bond to the urethane…

Interesting and thought provoking science you’re providing us, I look forward to seeing how this all progresses long term…

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I did some research last night and epoxy and urethane’s are both thermal polymers that will absolutely bond to each other. Epoxy has shitty abrasion resistance and I dont think it would work well for the actual enclosure. Someone would have to do some testing ( i might pick some up in the future) and see what the thermal capabilities are really like. I do think that a urethane enclosure might have the potential to be very durable and you can custom color it or paint it. You could very easily have a firmer flexible urethane enclosure with a soft vibration dampening layer on the inside that holds the thermally conductive epoxy P groups etc etc.

Im planning some custom drop through riser pads with this stuff or I may do the right thing and get some 75A shore hardness for there. Ill keep running my riptide bushings - but if you had a vac canister for degassing you could very easily and cheaply start playing with custom bushings

Im not even finished but if I did it again I would consider integrate straps into the urethane for retaining the P groups.
In this layout, with essentially 8 cells wide in 2S4P per section, the only way to get the P groups out is to lift from the center. The overlap on the edges and the material rigidity is enough to hold them. Simply heat shrinking them together will make them very tough to remove unintentionally. Thats my plan here. Heat shrink and drop in. To remove cut the heat shrink and lift them apart from center.

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definitely interested!!!

I like where your thoughts are leading you!

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This sounds like a waterproofing disaster

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I have read, but not tried, that adding aluminum powder into the epoxy gives it nice abrasion resistance.

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wondering aloud how that affects the dielectric properties of the epoxy

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