Onshape

Engineering a subterranean automotive portal Designing an underground garage requires more than just digging a hole; it necessitates a mechanism capable of bridging the 3.4-meter gap between a residential surface and a hidden workshop. Colin Furze faced this exact challenge when seeking a way to lower his DeLorean into his latest underground project. The solution involves a complex four-post lift system that integrates a turntable and an inspection ramp. This guide breaks down the fabrication of the primary lift legs—the structural backbone of a mechanism designed to move massive loads with precision. To begin this project, you need high-grade structural steel. Furze utilized heavy-duty box sections provided by Barrett Steel, specifically choosing 10mm and 15mm plate thicknesses to handle the immense stresses. The build also requires specialized hardware: heavy-duty bearings, Nylon sliding pads for low-friction movement, and custom hydraulic cylinders with a 2.4-meter stroke. For the design phase, Onshape software is essential for simulating clearances and ensuring the CAD model aligns with real-world dimensions. Fabricating precision telescopic legs The core of the lift consists of two box sections sliding over one another. However, off-the-shelf box section is rarely perfectly square, which can lead to binding or rattling. To solve this, the inner leg should not be wrapped in full-length Nylon pads. Instead, borrow the design logic of a telehandler: place shorter pads only at the ends where the pressure is most concentrated. Welding plates to the base of the leg allows these pads to slide into position, secured by countersunk bolts. To achieve a perfect fit, introduce adjustment shims and grub screws. These screws allow you to apply slight pressure to the Nylon pads, effectively removing any "wiggle" room and ensuring the leg ascends smoothly without metallic jarring. This mechanical tuning is the difference between a clunky industrial elevator and a precision car lift. Managing hydraulic access and internal slots A major hurdle in telescopic leg design is maintenance. If a hydraulic ram is sealed inside a 460-kilogram steel leg, repairing a leak becomes a logistical nightmare. To address this, Furze innovated a vertical access slot in the inner box section. By cutting a 1.6-meter longitudinal opening using a grinder and a custom fence for straightness, you create a window to remove the cylinder without disassembling the entire lift. Cutting such a significant portion of the steel naturally compromises structural integrity. To counteract this, weld small gusset plates every 300mm across the slot. These maintain the box section's shape while still allowing enough clearance for the hydraulic lines. When selecting rams, a single-acting bespoke cylinder is preferred over daisy-chained units to minimize the complexity of the hose routing inside these tight tolerances. Strengthening the guide rail system The lift cannot simply float; it must be tethered to the garage walls via a guide rail system. While sliding pads are an option, triple-bearing assemblies offer superior accessibility and lower resistance. The bearing bracket should be constructed from 15mm steel plate to prevent "bananaing" under load. To ensure the lift remains perfectly level, replace standard slotted holes with eccentric cams for the bearing shafts. By drilling offset holes in the shafts using a custom lathe jig, you can rotate the shaft to move the bearing closer to or further from the RSJ column. This provides micro-adjustments that lock the assembly into a true vertical path. Testing this setup with a 770kg sandbag—and intentionally pushing it to failure—revealed that curved edges on the plate cutouts distribute stress more effectively than square corners, which are prone to cracking. Troubleshooting and final synchronization When dealing with four independent hydraulic posts, synchronization is the final boss. If one corner rises faster than the others, the platform will tilt and potentially jam. Furze suggests a mechanical daisy-chain using a cable system. This ensures that if one leg moves ahead, the cable tension physically pulls the others into alignment. Additionally, safety is paramount in a residential setting. Each leg must be equipped with a safety brake—a clamp capable of holding seven tons. These brakes are triggered by a cable system that engages if the lift descends at an unsafe velocity, instantly locking onto a secondary safety rail. The result of this meticulous fabrication is a system that can lift upwards of 12 tons, comfortably handling a DeLorean and any future automotive additions to the secret vault.