In the last episode, you saw us build the first version of our custom independent suspension for the tiny house trailer. Seeing it in real life made us realise there were a few weak spots and a lot of faff built into that design, so this week is all about version 2.
We’re still going for a single-sided swing arm with airbags instead of springs, so we can control the ride height of the trailer, but the structure around it has had a proper rethink. The original design used scaffolding tube as a key structural part of the arm, which turned out to be inconsistent, hard to machine, and generally not the best idea for something that needs to be accurate and repeatable. Lesson learned.
If you’d rather watch all of this unfold, the full episode is below. Let us know in the comments if you’d like a deeper dive into the suspension maths, or if you’re more interested in the workshop setup and tooling side of things.
The big change is moving from that scaffold tube to a shorter, box-section arm with the clever bits built into the shape rather than tacked on afterwards. We’ve kept the sheet steel, tab-and-slot approach that worked so well before, but the new arm is stubbier, lighter, and much stiffer where it needs to be, with the bushing lugs forming part of the internal “ribs” that run right through the arm.
On screen, we walk through the differences between version 1 and version 2:
We also took a second look at how the suspension bolts to the trailer chassis. In the first design, some of the plates and bushings ended up hanging outside the chassis rails, which would clash with the storage boxes and anything else we want to hang off the side of the frame later on.
Version 2 tucks everything inside the rails. There’s a new, smaller bushing plate with multiple mounting holes so we can still adjust the whole suspension up or down in 24mm steps, but now all the moving bits are protected and out of the way. That plate ties back into uprights and crossmembers, so the arm pivot stays square to the trailer and we’re not relying on one chunky plate doing all the work.
We couldn’t really do this in the way we are without a few key tools. XTool have sponsored a few of these episodes by providing the MetalFab: a 1200W laser that can cut, weld and even clean metal. For us, the cutting side is huge. It lets us design quite complex shapes in CAD and have them appear on the bench in minutes instead of sending files away and waiting for parts to arrive.
For welding, we’ve added a new JASIC 250A MIG to the workshop. The suspension arms and brackets all have deep V-grooves where plates meet, and while the laser welder is brilliant for low-distortion fillets, it doesn’t fill those big gaps in the same way. The MIG lets us really load the joints with weld where we want strength, then we can still use the laser on smaller seams where we’re trying to control warpage.
To make the suspension work the way we want, we need custom polyurethane bushings with metal sleeves, pressed into outer tubes that weld into the swing arm and chassis plates.
It sounds simple written down. In reality, polyurethane is soft, likes to flap about when you spin it, and has a habit of peeling in big curly layers instead of cutting cleanly when you get to the edge. Pete spent a good while just figuring out how to hold it, how much to take off at once, and how to stop wasting expensive material every time we clamp a new piece in the chuck.
We end up with a better process:
By the end of the day, the bushings look closer to the CAD model than to the first lumpy attempt, but it definitely took more hours than we expected and created a lot of silly-string swarf in the process.
Inside each pivot point you’ve got:
The bolt clamps to the chassis, the polyurethane allows rotation, and the arm moves around that inner tube as the wheel goes up and down. It’s basically a big, serviceable hinge that spreads the loads over more area than a simple metal-on-metal pivot could handle.
Away from the trailer itself, there’s an important workshop milestone: we now have full three-phase power, which opens up the option to run heavier machinery like a decent pillar drill and proper extraction systems.
That last bit matters, because we’re staring down a whole lot of fibreglass, sanding, dust and fumes in the coming months. At the moment we spend far too long sweeping up, and neither of us wants to be breathing in resin dust every day, so a big extraction and filtration system is next on the list. It’s not a glamorous purchase, but it’s one of those investments that makes the rest of the project more sustainable.
By the end of the episode, we’re finally able to stand back and see the trailer’s shape properly. We settle on a 2.3m wide main body with about 420mm of side storage between the chassis rail and the outer wall, then cut and weld the crossmembers to match that footprint.
It’s still early days – the neck and some of the top suspension mounts aren’t there yet – but tying both chassis rails together and seeing the frame square on the floor makes it feel very real. Standing inside the outline, it’s easier to imagine where the walls, slide-outs and windows will go, and how this bare frame will eventually turn into an actual home.
