A stronger starting point
for your four-wheel robot.
Adjust the body around the wheels, battery and printer you actually have. Use replaceable modules and defined mounting interfaces so a new body shape does not mean redesigning the whole robot.
Editable body familiesFour wheel stationsReplaceable modulesMillimetres throughoutRecommended first build
Start with a ribbed tray or deep twin-rail chassis, keep the battery low, and use bolted wheel adapters. For scooter-style hub motors, use measured metal axle and torque-reaction plates connected into the frame. Printed body panels, trays and adapter carriers are useful; the complete assembly still needs fit and load testing before operation.
Inspect the assembled robot before editing a part.
Open the complete robot studio to see the chassis, four wheel carriers, shafts, wheels, top deck, housing and roof together. Select a component to inspect its parameters and its place in the assembly. The assembly workflow guide explains the shaft connection, shared dimensions and separate part projects. The original inventory remains in Part Studio.
Choose the load path before the appearance.
Your reference images show a tray floor, deep side members, removable upper panels and separate wheel locations. The useful idea is the depth of the frame and the separation of serviceable parts. A beautiful thin shell or a large solid infill percentage alone will not make the wheel attachments strong.
| Body family | Useful for | Tradeoff to check |
|---|---|---|
| Ribbed open tub | A protected battery/electronics volume with a continuous floor and deep walls. Closest starting point to your reference tray. | Largest continuous print footprint; check floor warping, drainage and access to mounting hardware. |
| Twin-rail ladder frame | An accessible skeleton for changing decks, battery trays and wheel modules. | The open center needs a separate tray or deck. Check twisting of the assembled frame. |
| H-frame with central spine | A central equipment beam with open space on both sides for tools or cable routes. | Side loads reach the spine through transverse beams; inspect their junctions and bending. |
| Chamfered utility deck | An exposed mounting platform with angled ends, edge rails and four wheel pads. | Electronics need their own enclosure. The low deck is not a weatherproof shell. |
| Capsule body with outriggers | A rounded central body with flat, accessible wheel attachment pads. | Check outrigger bending and tyre clearance around the curved body. |
| Split modular frame | A two-part body for a smaller printer and replaceable front/rear sections. | Print front and rear separately, plus two splice plates. The joint must be checked for bending, slip and fastener access. |
All six body presets begin at a 300 × 180 × 55 mm envelope with a 200 mm wheelbase; adjust them to your hardware. The default split sections are roughly 150 × 180 mm in plan, before slicer brim allowance. Read the model inspector for the exact exported bounds. A larger one-piece body will not fit every desktop printer.
The included shapes are engineering starting points. Shape names do not imply a payload rating, motor fit, suspension function or environmental sealing.
Make the body adjustable; keep the hardware measurable.
The robot family recalculates its built-in mounting positions from the body width, height, wheelbase and fixing pitch. Keep the same interface values in every mating part, including the mounting-pad depth used by the top holes (18 mm by default). Parametric adjustment changes the exported geometry; it does not make a finished printed chassis telescopic. Custom features that you add separately still use their own explicit coordinates and must be checked after resizing.
| Default interface | Coordinates / dimensions | Meaning |
|---|---|---|
| Body datum | X runs along the 300 mm body; Y across its 180 mm width; the underside is Z = 0. | Use this datum when matching a deck or making an adapter in another CAD tool. |
| Four wheel stations | X = ±100; outer side faces Y = ±90. | Two stations on each side; 200 mm front-to-rear spacing. |
| Side fixing pairs | At each station: X offsets ±14; Z = 27.5; holes Ø5.4 along Y. | 28 mm pitch. Global X values are −114, −86, +86 and +114 on both sides. Verify printed clearance for your chosen hardware. |
| Deck / crossmember pads | X = ±100, Y = ±81; holes along Z. | Four vertical fixing positions on the thick side pads. Match body width, wheelbase, fixing diameter and mounting-pad depth in the deck preset. |
| Central accessory grid | X = ±14, Y = ±14; holes along Z. | 28 × 28 mm square for the battery cradle or sensor mast foot. Check underside nut and washer clearance. |
| Wheel adapter, flat export | 64 × 76 mm face, 6 mm plate; 10 mm overall with ribs. Fixings at (±14,+18); round Ø12.4 aperture at (0,−18). | Both coordinate pairs are in the adapter's local XY plane. The 36 mm axle drop is generic, not a verified hub-motor fit. |
| Split-frame joint | Two underside splice plates; four holes each at X = −40, −20, +20, +40 along its centerline. | Use eight through-bolts to join the front and rear sections. Plate Y position follows its corresponding frame rail. |
Orient the wheel adapter: export and print it flat with its ribs upward. For assembly, stand it against the body's outside side face with the fixing pair above the shaft aperture. A +90° rotation about its local X axis maps local Y upward; the other side can then use a 180° rotation about world Z. Translate it to align the fixing pair and keep the ribs outward. The complete robot studio places these carriers at the four wheel stations automatically. This inventory page describes their local print coordinates and original 36 mm axle-drop preset. The complete assembly uses a 40 mm axle drop initially; the assembly guide describes its installed positions and current part exports. The software does not validate structural strength.
At the default settings the axle datum lies at Z = 27.5 − 36 = −8.5 mm relative to the body underside. For an ideal rigid wheel of radius R, the body's nominal underside clearance is R + 8.5 mm; bolt heads, splice plates, tyre deflection and other lower components reduce the actual minimum. Check the full assembled geometry rather than setting clearance from body height alone.
Starter parts list
One chosen body, four ribbed wheel adapters, and your four actual wheel/motor units. Add a top deck, battery cradle and mast foot as needed. A split frame requires front and rear exports plus two splice plates. Measure and provide metal axle plates, fasteners, washers and any compression sleeves separately. Other kit modules are available for custom frames; they are not all required in the same robot.
Measure before customizing
- Wheel outside diameter, tyre width and full rotating envelope.
- Motor axle diameter, flats, shoulder spacing, thread, available nut engagement and cable exit.
- Motor supplier's peak driving and braking torque; rated electrical power alone does not define the mount load.
- Battery dimensions, component masses, target wheelbase, track and ground clearance.
- Usable printer bed, including brim and clamp clearance.
Keep a clear force path
Wheel loads pass through the axle plate, spaced fasteners and reinforced side member into crossmembers and the body. Keep a short overhang between the wheel and its support. Tie left and right rails together near the wheel stations.
Use separate adapters to change motors. Keep the motor's exact shaft geometry in the metal adapter, so the body interface can remain reusable.
The hub-motor detail matters. The axle must resist reaction torque when the wheel drives or brakes. A round hole in a printed ear does not provide a keyed anti-rotation interface. Grin documents this failure mechanism and the purpose of torque arms. The suggested metal load path here applies that principle to this robot; it is not a claim that an e-bike torque arm fits your motor. [5]
Build an assembly you can inspect and repair.
| Element | Practical role | Assembly decision |
|---|---|---|
| Body / frame modules | Carry electronics and connect the four wheel stations. | Use rails and crossmembers rather than a wide unsupported floor. Keep seams away from concentrated wheel loads where possible. |
| Wheel adapter carrier | Locate a replaceable measured motor adapter. | Use through-bolts, broad washers or backing plates. A printed carrier does not replace the motor's metal anti-rotation interface. |
| Metal axle / torque plates | Capture axle flats or the manufacturer's intended torque interface. | Design for the actual motor, thickness, edge distances and load. These are fabrication requirements, not universal ready-to-fit components. |
| Deck, battery tray, cover | Organize components and keep servicing accessible. | Restrain the battery in every direction. Keep access to axle fasteners and cable bends. A cosmetic cover should not be counted as structural bracing without analysis. |
| Joints and fasteners | Transfer loads without crushing the plastic. | Use metal nuts/inserts, washers and, where needed, compression sleeves. Select bolt length after measuring the complete stack; do not copy steel-joint tightening torque into plastic. |
Stratasys recommends supporting bosses with ribs or gussets and using metal inserts, nuts and suitable washers rather than relying on threads formed directly in printed plastic. Those principles inform the assembly recommendations above. [4]
Stronger parts start with orientation and geometry.
Depth, ribs and supported holes
Keep wheel bolt groups on broad pads supported by rails or gussets. Use smooth transitions at load-bearing junctions; a rounded outside silhouette is not the same as a fillet at an internal stress concentration. Avoid cutting a wiring slot through a rib or the narrow ligament beside a wheel bolt.
When splitting a body, use overlapping splice plates and multiple spaced bolts. A glue-only butt joint is a poor default for a serviceable mobile robot.
Do not load a tall printed ear in peel
FDM strength depends on direction. Orient a removable bracket so its primary tension and bending load is carried mainly within the printed layers. Print one bracket first and inspect its toolpaths before committing to four. A flat body floor is usually a convenient starting orientation, but wheel loads can make its upright attachments the weak point. [1]
| Material | Where to start | Constraint that matters |
|---|---|---|
| PETG | Accessible first structural prototypes; good layer adhesion and relatively easy printing. | Check sustained deflection and the temperature near motors, drivers and sun-exposed surfaces. The finished joint still needs testing. [2] |
| ASA | Outdoor covers and body modules where UV exposure matters. | Manage warping with an appropriate enclosure/process and ventilation. Print settings depend on the filament and printer. [3] |
| PLA | Fast dimensional mockups for this project. | Do not infer outdoor service life or sustained-load suitability from a successful indoor fit test. |
| PA / PC / reinforced grades | Consider only with a validated material and printing process. | Use the exact grade's datasheet and conditioning requirements. A “carbon fibre” label is not an assembly strength certificate. |
Prusa specifically suggests increasing perimeters for more solid PETG parts rather than simply increasing infill. Neither 100% infill nor a visually closed mesh removes layer-direction weakness or validates a joint. [2] Print hole and mating-clearance coupons in the final material and orientation, and ream critical holes carefully when required.
A short, evidence-based build sequence.
- Choose the architecture. Start from the body family best suited to your packaging and printer. Save an editable project before changing anything.
- Set the four stations. Adjust body dimensions and wheelbase, then confirm every wheel mount remains in supported material. Check the full tyre envelope, fastener access and cable route.
- Print one interface. Fit one carrier, the real axle adapter and its fasteners. Measure holes, spacing and offsets; resolve fit before printing the remaining modules.
- Inspect the sliced body. Look for disconnected islands, unexpected thin walls, slot interruptions, unsupported regions and actual print-bed fit. Export each physical part separately in millimetres.
- Assemble and load without driving. Restrain the chassis. Add representative component masses and intended payload gradually, measuring permanent deflection, joint slip and bolt-seat crushing. Check uneven support as well as a flat floor.
- Test progressively at low speed. Check forward/reverse torque, braking and turning on the expected surface. Skid steering and a snagged wheel can load the mounts differently from straight rolling. Inspect for cracks, layer separation, loosened joints and wire chafing after each stage.
What remains unknown
The screenshots do not specify axle geometry, peak torque, payload distribution, impacts, material grade or printer quality. Therefore this package assigns no safe working load and makes no “unbreakable” claim. A valid mesh confirms geometry; a successful fit confirms dimensions; only analysis and representative physical tests can establish the working limits of your complete robot.
Why these choices were made.
Manufacturer guidance informs the design principles. The body geometries, suggested prototype workflow and illustrative print trials are specific recommendations for this package, not manufacturer-certified robot designs. References checked 13 October 2026.
- Prusa Research — Modeling with 3D printing in mind. Orientation, clearances, splitting parts and iterative fit checks.https://help.prusa3d.com/article/modeling-with-3d-printing-in-mind_164135
- Prusa Research — PETG. Material behavior and the value of perimeter walls.https://help.prusa3d.com/article/petg_2059
- Prusa Research — ASA. Outdoor use, UV resistance and process constraints.https://help.prusa3d.com/article/asa_1809
- Stratasys Direct — FDM Design Guide (2025). Bosses/ribs, stress concentrations and fastening hardware.https://www.stratasys.com/siteassets/sdm/content---website-storage/design-guides/dg_sdm_fdm_0725a.pdf
- Grin Technologies — Torque Arms. Hub-motor axle reaction torque and transfer into the frame.https://ebikes.ca/product-info/grin-products/torque-arms.html