HST Truck Rebuild Kit: Hamboards Flow Kit Story | After 9 Years
A note from the inventor
Inventing is a journey of discovery. All it takes is a combination of curiosity, knowledge, and purpose — and a willingness to keep going long after the first prototype tells you it's wrong.
I'm an experimentalist by training — a Ph.D. engineer with thirteen US patents to my name in fields that have nothing to do with skateboards. The HST truck has been the longest journey of any of them.
I started this for my cousins. They're the Hamborg family — five tow haired, blue-eyed surfing lifeguards and local legends from Surf City USA. My cousin Peter had been making longboards in his garage for ten years under the name Hamboards, selling them to fellow Huntington Beach locals. The boards were beautiful. They wanted to ride them like surfboards. The trucks they had couldn't do it. That's where I came in.
We've spent the better part of a decade building, testing, breaking, and rebuilding the HST truck. We're now on the fourth generation of Wave Cams, the second generation of the truck system, and a Flow Kit that, for the first time, replaces every wear part in a single rebuild.
I think we've finally got it.
That's not a casual statement. The HST truck has always been a moving target — every time we solved one problem, riders pushed us toward the next. But sitting here in 2026, looking at what we ship today versus what we shipped in 2017, I'm comfortable saying it: the surf-style carving truck we set out to build is done. It's reliable. It's serviceable. It carves the way we always wanted it to. And when something does eventually wear out, the path back to a like-new ride is one Flow Kit away.
This post is the story of how we got here.
The Wave Cam came first
Before the HST truck, there was the Wave Cam.
The Wave Cam is the simple machine at the heart of every truck we've ever built. It translates the side-to-side force of carving into the up-and-down compression of a spring. No bushings, no rubber, no flex — just a cammed surface that loads a spring as the rider leans, and releases that energy back as the rider returns to center. It's the reason an HST-equipped board feels like a surfboard on water instead of like a skateboard.
Every invention stands on what came before. Original Skateboards built the first carving trucks around the Wave Cam. Their S8 truck introduced a generation of riders to what spring-loaded carving felt like. We rode them, we sold boards equipped with them, and when Original Skateboards went out of business, the technology was too good to disappear.
But there was a problem.
The emergency that started the HST truck
The first generation of Wave Cam trucks — the ones Original Skateboards built and we initially sold — had a structural vulnerability that became impossible to ignore as riders pushed them harder.
The pivot cup that held the wave cam had a locktab slot cut through its outer perimeter — a notch designed to receive the locking key that kept the wave cam aligned. That notch was also a stress concentrator.
When riders overtightened the kingpin (which was easy to do, because the kingpin threads ran nearly the full length of the bolt and there was no mechanical limit on how far the nut could be tightened), the wave cam would crack first. But that wasn't where it ended. In severe cases, the pivot cup itself would fracture at the locktab slot, and broken pieces could fall out of the truck mid-ride.
Notwithstanding Original Skateboards commitment to cover these as warrantee claims, our riders were at risk. I considered it an emergency. And then... Original declared they would no longer warrantee and then... eventually went out of business, so we had a real situation on our hands.
After a years worth of design and prototype testing, in August 2017 I filed a provisional patent applications on a redesigned baseplate. The reason I filed was to keep from getting sued for infringement... because an awarded US Patent is equal to a poor-man's freedom to operate. The full application was filed in August 2018, and US Patent 10,507,375 B2 — Skateboard Base Plate and Associated Systems — was granted on December 17, 2019. The patent has 20 claims and 16 drawing sheets, and Original S8 Carving Trucks are explicitly cited in the references as the prior art the patent improves on.
The core engineering idea is straightforward, and it's the design philosophy that has shaped every HST truck we've built since. Because we understood carving technology, we made several pivot axes. Please read more here in this blog.
Make the wave cam the engineered fail point. Protect the baseplate.
The wave cam is a cheap, replaceable plastic part. The baseplate is the expensive structural component, and a fractured baseplate is a catastrophic failure with safety implications. So we redesigned the baseplate to eliminate the locktab slot — the pivot cup now has an uninterrupted outer perimeter surface. The locking key channels were moved so they no longer pierce that surface. We also reduced the threaded length of the kingpin so the nut physically cannot be tightened beyond the safe range — operator error is removed from the assembly process by the geometry itself.
The result: even if the wave cam cracks under extreme load (which is now its job, by design), the baseplate stays intact, the wave cam fragments are contained inside the pivot cup, and the rider stays on the board. Failure becomes a maintenance event, not an emergency.
That's the patent that started the HST truck. Everything we've built since sits on that foundation.
The HST truck takes shape: 2017 to today
With the redesigned baseplate as the foundation, we kept improving every other component. The HST truck did things no other longboard truck could. Up to 30 degrees of lean. Up to 20 degrees of rotation in each direction. A snappy return-to-center that mimicked how a surfboard rebounds out of a bottom turn. Riders called it loose. We called it surfing on land.
But the baseplate patent only solved the catastrophic failure mode. The components inside the truck still had room to improve. Wave Cams wore out faster than we wanted. Springs sometimes lost their spring. Washers wore unevenly. Each part had a failure mode of its own — none of them dangerous anymore, but all of them annoying. Over the next nine years, we hunted them down one by one.
I'm the East Coast cousin. Not blond, not blue-eyed, not California chill. What I can do is listen to an athlete describe what something should feel like and translate that into geometry, materials, and tolerances. The longboards Peter was making in his garage were beautiful, but no truck on the market could carry them with the response a surfer wanted — the boards were big, and the trucks weren't built for that kind of load or that kind of feel. Fixing that was an engineering problem, and I stayed in the workshop because I knew that with enough time I could solve it. In time, the project became bigger than the family. It became about every rider who wanted the feeling of riding a wave on dry land.
What broke, and what we fixed
The springs. Early HST springs were inconsistent. We tested dozens of materials, dozens of geometries, before we landed on the silver and gold compression springs we ship today. The current springs last a lifetime. Riders almost never need to replace them. (If yours are more than five years old, we still recommend a refresh, but that's about it.)
The kingpins. Even with the patent's thread-length limit preventing dangerous overtightening, we kept refining the kingpin spec. The current 85 millimeter precision kingpins are threaded so the nut bottoms out at exactly the right preload — no guesswork, no feel-it-out tuning. The geometry does the work.
The washers. The original zinc-plated steel cut washers had two problems. They squeaked against the aluminum hangers — metal-on-metal contact you could hear from the deck — and we couldn't get consistent thickness from one production run to the next. We moved to molybdenum-impregnated nylon, which is self-lubricating against aluminum and virtually silent. The dual moly washer set in particular gave us exact, repeatable thickness every order. The squeak disappeared. Trucks felt the same, every kit, every time.
The hard stop at maximum lean. This was the big one. For years, riders asked for more connectedness through the deepest part of the carve — the place where conventional truck designs hit a wall. The space inside the HST baseplate made traditional bushing solutions impossible. So we engineered something new: a cast polyurethane cone-shaped compression bushing positioned concentrically inside the spring. As you lean deeper, the spring and the bushing compress in parallel, producing a force curve that becomes progressively stiffer with lean angle.
In materials science, when metal gets harder the more it deforms, that's called strain hardening — and it's permanent. What the bushing-and-spring system does is similar, but fully reversible: the deeper you lean, the more force the truck pushes back with, but the moment you unweight it, the system recovers completely. No hard stop, no permanent deformation, just a progressively cushioned transition at the extremes of the carve.
We filed the provisional patent application on July 28, 2023, and the non-provisional is currently pending. We call the system Progressive Compression Technology, and it's what the Flow Kit ships today.
The Wave Cams themselves. This was the longest battle. Three full generations of materials and geometries. Each one taught us something. The early Wave Cams cracked under load. The second generation, made of molybdenum-impregnated nylon, lasted longer — until we shipped the Progressive Compression bushing. The new bushing transferred more force through the Wave Cams than they'd ever seen, and the moly nylon started showing deformation around the hanger tabs. So in 2023 we moved to fiber-reinforced nylon — strong enough to take the new loads without flinching, but still introducing a subtle off-axis rotation that put uneven stress on the slot. The third generation was the strongest we'd ever made, but we still weren't satisfied.
The Wave Cam 4.0 breakthrough
The Wave Cam 4.0, our current and fourth generation, is the design that finally settled it.
Single-axis geometry. Two-piece all-nylon construction. The cam key is no longer a separate piece bolted into the lower half — it's molded integrally into the lower itself, eliminating the joint that had been a stress concentrator in every previous version.
We ran finite element analysis on the 4.0 against the 2.0. Peak slot stress dropped by a factor of 2.77. That number is the difference between a Wave Cam that wears predictably and a Wave Cam that fails unexpectedly. Off-axis rotation — the failure mode that haunted the second generation — is eliminated at the source by the single-axis geometry.
The Wave Cam 4.0 is the first one we've shipped where we don't have a list of things we'd change in the next version. We've been chasing this design for nine years.
The Flow Kit: how we keep your trucks alive
The HST 4.0 Flow Kit is the natural conclusion of all of this. One kit, every wear part, both trucks. Wave Cam 4.0 set, two precision kingpins, two moly-impregnated washers, two compression bushings, the hex tool, the Wave Cam lubricant, and your choice of springs (or no springs, if yours are still going strong). Shop owners rebuilding multiple sets at a time can use the Flow Shop Kit, which services five trucks per kit.
Springs last a lifetime. Wave Cams don't — they're the engine, and engines wear out. The Flow Kit is the rebuild that takes a tired HST truck and makes it ride like the day you bought it. Or, frankly, better than the day you bought it, because the components in the kit are all current-generation and 100% backwards compatible with every HST truck we've ever shipped.
If you're rebuilding a five-year-old HST 2.0, the Flow Kit upgrades it to 4.0 spec. If you're rebuilding a nine-year-old original HST, same thing. The truck doesn't care how old it is. The Flow Kit makes it new.
For Original Skateboards riders
If you ride an Original Skateboards longboard with S8 trucks, the Flow Kit is for you too.
Original went out of business years ago. The riders who loved those boards have been left without a parts source ever since. Some of you have been keeping your trucks alive with creativity and salvaged hardware. Some of you have given up and shelved boards that still had a lot of life in them.
You don't have to anymore. The Flow Kit fits Original Skateboards S8 carving trucks. It's the same Wave Cam foundation, just nine years of refinement bolted on top. Half of every Flow Kit we ship right now goes to an Original Skateboards owner. Your boards aren't dead. They were just waiting for the right rebuild kit to show up.
What "done" actually means
When I say the HST truck is done, I don't mean we've stopped innovating. We'll keep refining. There will probably be a Wave Cam 5.0 someday, and a Flow Kit 2 after that. We've been doing this for nine years and we're not about to stop.
What I mean is: the foundation is solid. The truck system works. The components don't fail in surprising ways anymore. The carve feels the way we always wanted it to feel — connected, progressive, surfboard-on-water from center all the way to the rail. The maintenance path is clear: ride it until the Wave Cams wear, install a Flow Kit, ride it for another few years.
That's what I set out to build in 2017. It took longer than I thought it would. But we got here.
And to the Hamborgs in Huntington Beach who started all this — the truck finally feels the way you wanted it to feel.
What started as a search for a better surf-style longboard truck has matured into a patented spring-loaded compression system with a track record. We built it for surfers, and that's still who rides it most. But the underlying engineering — progressive, reversible compression that recovers a meaningful fraction of energy through every lean cycle — applies to any vehicle that needs to lean and recover. We've had inquiries from organizations exploring uses we didn't originally imagine. If you're working on something in that space and the technology might fit, we're open to those conversations.
If you've been with us through the journey — through the early Wave Cams that cracked, the springs we replaced, the iterations and the apologies and the experiments — thank you. You're the reason the HST 4.0 exists. The riders who kept telling us what wasn't working were the riders who built this truck.
If you're new to HST, welcome. The truck you're riding is the one we spent nine years getting right.
— Don Sandusky
Founder, Hamboards. Inventor, Ph.D. Engineer - Entrepreneur in Training
Rebuild your trucks with the HST 4.0 Flow Kit →
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Frequently asked questions
What is the HST truck?
The HST (Hamboards Surf Training) truck is a patented spring-loaded longboard truck designed to simulate the feel of surfing on land. Instead of using rubber bushings like conventional skateboard trucks, the HST uses a Wave Cam mechanism that compresses a spring as the rider leans, producing a snappy return-to-center and the rail-to-rail carving feel of a surfboard.
What is a Wave Cam?
The Wave Cam is the simple machine at the heart of the HST truck. As the rider leans, the cammed surfaces convert side-to-side force into vertical compression of the spring. The spring releases that energy back as the rider returns to center. It's a wear part — Wave Cams need replacement periodically depending on how hard and how often the truck is ridden.
Why did Hamboards iterate the Wave Cam four times?
Each generation taught us something the previous generation couldn't. The first cracked under load. The second introduced off-axis rotation that wore the slot unevenly. The third was significantly stronger but still had a separate cam key. The fourth, current Wave Cam 4.0, integrates the cam key into the lower piece, uses single-axis geometry, and reduces peak slot stress by 2.77x compared to the 2.0 according to finite element analysis.
Will the HST 4.0 Flow Kit fit my older HST trucks?
Yes. The Flow Kit is fully backwards compatible with all Hamboards HST trucks (HST 2.0, HST 3.0, HST 4.0). Installing a Flow Kit on older trucks upgrades them to current 4.0 specification.
Will the Flow Kit fit Original Skateboards trucks?
Yes. The Flow Kit fits Original Skateboards S8 carving trucks. Original Skateboards is no longer in business, and the Flow Kit is the recommended rebuild kit for owners of Original Skateboards longboards.
How do I know if my trucks need a rebuild?
The most common sign is a "mushy" feel through the lean, reduced carve depth, or a wiggle at the trucks during normal riding. That's the Wave Cam wearing down. Springs almost never need replacement; the wear parts are the Wave Cams, bushings, washers, and kingpins, all of which are included in the Flow Kit.
How often do I need to rebuild?
There's no fixed interval. It depends on how often you ride, how aggressively you carve, the surfaces you ride, and the rider's weight. Most riders feel the difference well before the components actually fail. When the carve starts to feel less responsive than you remember, that's the signal.
Is the HST truck patented?
Yes, and there are two patents covering different aspects of the design. The HST baseplate is protected by US Patent 10,507,375 B2, Skateboard Base Plate and Associated Systems, filed in August 2018 and granted in December 2019. It covers the structural redesign that prevents catastrophic pivot cup failure, eliminates the locktab slot weak point present in earlier carving truck designs, and limits kingpin thread length to prevent overtightening. A second patent application covering Progressive Compression Technology — the cast polyurethane compression bushing positioned concentrically inside the spring — was filed as a provisional application on July 28, 2023, with the non-provisional currently pending. The Wave Cam 4.0 itself is not patented; the design improvements were judged to be straightforward extensions of well-understood mechanical principles, and Hamboards chose not to pursue protection on it.
Why is the HST truck baseplate designed differently from the original Wave Cam trucks?
First-generation Wave Cam trucks had a locktab slot cut through the outer perimeter of the pivot cup, which acted as a stress concentrator. Combined with kingpin threads that allowed unlimited tightening, the design could fail catastrophically when overtightened — the wave cam would crack first, but the pivot cup itself could fracture next, with broken parts falling out of the truck mid-ride. The HST baseplate eliminates the locktab slot, gives the pivot cup an uninterrupted outer perimeter surface, and limits kingpin thread length so the nut cannot be overtightened. The wave cam is now the engineered fail point — when it eventually wears, it does so safely and contained, and the baseplate stays structurally sound.