Today I learned: I’m a professional toilet cleaner
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Truly the backbone of society 
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Post processing on the metal parts is pretty much done. I’ve got front axle dropouts/brake mount and rear axle chain tensioner/brake mount assembled. The rear triangle and front fork can start assembly at this point
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In order to get the swingarm assembled, I stuck the rear dropouts onto the swingarm pieces with JB Weld and screws.
With the rear wheel bolted on to the swingarm, and the pivot forgings bolted onto the frame, I went around to each pivot forging and tacked it in place with epoxy, squaring up the rear wheel in both axes with straightedges, a level, a square, and a healthy dose of eyeballin’. It’s probably fine.
The beast has its tail 
The swingarm is just tacked together though, it still needs to have the shear bridge reinforced, the suspension mount installed, and those side triangle bits boxed out.
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This one’s the big kahuna. The large enchilada. The generously proportioned fajita. The most complicated geometry I’ll be trying to forge in this project, and the most massive at 400g for each of the 4 copies i need to make. The mold has 8 components, and the printed parts have 1.3kg of plastic and 36hrs print time in them, so hopefully they’ll survive the de-mold and i can reuse them for the -
Every print lies shattered in the dirt, as does my pride. The heap of twisted refuse stands as a monument to hubris. For when those of man, pretender to glory, are built without foundation, will not nature make her own? Beside, the lone and level sands stretch far away.
The part’s good tho 
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Part 3: Unsolicited Deck Pics
The deck starts as a balsa core for the center, plywood core for the rear drop section, and paper core for the flanges
A printed tube is embedded along the underside to carry the torsion rod
The fabric is vac bagged onto it in situ, so the flanges mesh perfectly onto the frame
The torsion rod is a sheet of +/- 45 degree carbon fiber rolled around an 8mm fiberglass tube, up to a diameter of 20mm
The footpad is built on a balsa core as usual
A carbon forging is made with double flatted hole to lock onto the torsion rod, and a bunch of M6 inserts to select the leverage ratio of the mechanism
That control horn is glued up to the front of the deck, and uses a thrust bearing to keep the whole assembly from shifting back under acceleration
The rear end gets radial needle bearings to support my weight, encased in what is totally a professional bearing housing and definitely not a bunch of epoxy putty that I smooshed into arch shapes
The footpad gets some printed blocks with teflon thrust bushings to keep the assembly from sliding forward under braking
The pushrods need to be springy, since the 4bar links don’t move left a right symmetrically, so the distance between them changes as you steer. Using compression preload will also give a centering force to the front wheel, so I made springy turnbuckles with rod ends, M6 inserts, and 1mm spring wire.
If you have enough JB weld and string, you can solve most problems.
Finished deck!
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Can I just say, damn boy!
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Part 4: It’ll Cure What Tails Ya
The tail frame starts off as wood core panels like the rest of the project
They all get an initial layer of flax
A bunch of laser cut parts are assembled into a set of chain tensioner mechanisms, which use captive screws to slide the rear axle back and forth
The tensioners are secured to the swingarm panels, and bolted to the wheel to ensure correct spacing
The bearing block forgings are glued onto the swingarm, in situ again to ensure correct alignment
And so the swingarm is tacked together
The empty spaces get boxed out and the entire thing goes in the vacuum bag, for 1 more layer of fabric over the arms and 4 more layers around the center bridge
Came out slightly wrinkly but whatever at this point, it was pretty hard to consolidate such a weird shape in the bag
The shock mount needs to be in a specific location relative to the pivot, so I jig it up with foamboard
The mount plates then get some big ass epoxy fillets and some carbon tow to transfer the load into the arm
And finally, the main frame gets a matching mounting lug for the shock, consisting of a couple plates of 3mm plywood for the little fork, 4 layers of flax fabric laid over the frame to spread the load, and a heap of epoxy/sawdust filler to join the two.
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After subdividing the mold into a completely reasonable 14 parts, suspension link #2 is done and most of the mold components survived 
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At this point I’ve made all the forgings for the steering system, 4 links, 2 caps, and a crown piece that will attach to the fork.
But the crown was chunky enough that my 8 hour epoxy kicked off and fused to large parts of the mold, which required a few hours of chiseling. Whoever designed this thing needs to be fired.
Everything cleaned up
There’s about $150USD of 6900 bearings in this picture, which isn’t far behind the raw material cost for the forgings. It sounds like people sometimes think all the carbon parts I do are for bling factor, but the primary motivation is actually strength to cost ratio. Add the cost of the shoulder screws + printed molds, and I think the carbon components are actually the cheaper part of the steering system, compared to the metal components.
The beast has its head 
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Relatable
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The ancient evil (carbon fiber dust) that has plagued this land (my apartment) has been sealed away with powerful magicks (spar urethane) as was foretold in the prophecy (me at Lowe’s)
The fork pieces fresh outta the bag. These are the last structural components 
I’m getting dangerously close to a rolling chassis
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PART 5: Fork You And The Horse You Rode In On
The fork pieces start as the standard balsa/ craft paper core
The fork arms are laid up with [bias ply][unidirectional ply][bias ply] of flax fabric
Aluminum splash plates are glued and screwed on there, to handle clamping loads for the axle and for brake caliper mounting
The steering linkages are based on 6900 flange bearings and 10mm shoulder bolts, and since the load path from the contact patch to the frame is pretty indirect, it’s super important to make sure there’s no slop in any of the pivots
I landed on using a 22mm steel bar as a mold for the bearing bores, which gave the most precise fit and was able to survive repeated de-molding
Same goes for using 10mm steel bar as a mold for the shoulder bolt bores
The suspension is crammed inside the 4 bar steering linkage, by using a short parallelogram linkage inside the follower arms. The top and bottom of the parallelogram are designed symmetrically, so that I have fewer molds to print
The final bar of the steering linkage has a huge boxy protrusion sticking out the front to provide a mounting surface for the fork arms. Wasn’t fun to mold, but I think it saved work overall, and it’s pretty strong
All the forgings are finished with spar urethane and get 10mm washers glued on to bear against the inner race of the flange bearings
The crown forging is united to the fork arms with my patended method of bolting the wheel on, slapping some levels and straightedges on there, and poking the parts around for about 90 minutes until the glue starts to harden and then you say “ehhhh good enough”
The beast has some fangs
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ROLLING CHASSIS, MUDDERCLUCKERS
Promises made, promises kept.
Flyboy 2024
“is this why you’ve been ignoring me for the past week, father?”
[phonk noises intensify]
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Holy shit dude, awesome work!
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DUUUUUDEEEE
This is what Batman is gonna ride in the next movie series
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Thanks everyone!
ROLLDOWN TEST
I took the bike to the top of the hill at my local park, and we can finally answer the question of whether all the changes made here actually fixed Orbital’s lackluster handling:
Notes:
- This is probably the hardest thing to push start, it needs full commitment to hopping on one leg at falling-on-your-face speeds before you can jump on the board. Very-low-speed controllability is worse than version 1
- Steering response is way better than version 1, I didn’t have the speed or the space to carve hard today, but it’s clear that I only need to tip it a little bit to get it turning. I could also feel tire feedback pushing against the lean during gentle carves, which is a real nice improvement. The contributing factors for the responsiveness are probably some combination of: the improved 4 bar geometry, the 100% ball bearing pivots, the lack of centering spring, the wider tires, and the increased gyroscopic effect from the front wheel weighing fifteen fucking pounds.
- Below 5mph, it’s super easy to get into a wobble since the steering is so responsive. You can see this in the video, where it has a little wiggle below 10mph as I’m carving, but it gets worse at the bottom of the hill before I dismount. This means I have created the first ever skateboard to experience the opposite of speed wobbles. The people asked, and I delivered. You too can experience slow wobbles, for the low low price of…
- The final run down the bigger hill got up to 15-20mph (no video, sorry), and the gyro effect from the front is insane. I had to push down on the deck to get it to change direction because it wants to stay upright so badly. Version 1 felt like balancing on stilts at any speed, which wasn’t very confidence inspiring. The feeling of being so stable on a platform so far off the ground was crazy. I can’t wait to have power on this thing so I can really throw it around.
- The rear foot steering system was less effective than I hoped. I designed the linkage to help self center the board, as in, if the board starts to leans out from under me and I keep my rear foot level, the steering pressure the linkage creates should level the board back out. That part works, stepping onto the footpad creates a noticeable reduction in the workload required to keep the board upright. That workload reduction is actually one of the biggest improvements over version 1. But the foot linkage can’t steer the front very hard, it only has a slight effect. I may need to remake the pushrods to be more rigid, or maybe I’ll end up locking out the rear footpad and letting the front steer freely, since I might want both feet pushing on the deck for high speed maneuvers. But that’s a problem for later.
And that’s the build like 80% complete! I have big plans to install my 75mph power system, a legstick throttle, hydraulic brakes, Tomiboi toe hooks, headlights, auto-blinking tail lights, and to try and make a wireless wrist-mounted Davega, but that won’t start for a couple weeks at least. I’m going on vacation with friends this week, and I have a work trip right after that, so I’m gonna stop trying to fit this build into my schedule and decompress.
But don’t worry, the plan is still to have this machine running under its own power in time for Electrify Expo NY and NYC Carve! It’s gonna be sick.
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