Electric Two-Wheeler Seat Design with Under-Seat Storage

The problem

Scooter buyers judge a vehicle by seat comfort and whether a helmet fits under the seat, but on an EV the same space competes with the battery and controller. A seat that is too high, too wide at the front or that fouls the storage bin when opened is a common design failure. The project teaches packaging, surfacing and plastic-part design together.

Objectives

• Set seat height, length and width from example rider data and the vehicle layout.
• Model a seat base, foam and storage bin, with a hinge and a latch.
• Size the storage volume to fit an example helmet envelope while clearing the battery.
• Check base stiffness for an example two-up load and produce drawings.

What you need

Key concepts

Seat height and flat-foot reach

Seat height, seat width at the front and floorboard height together decide whether a short rider can put both feet on the ground at a stop.

Hinge arc

The seat swings around the hinge axis; every point on the seat traces an arc that must clear the body, grab rail and rider-side panels.

Packaging envelope

A simple solid representing the space a component needs, such as the helmet or battery, used to check fit before detailed parts exist.

Foam density and thickness

Comfort depends on foam thickness, density and shape; too thin and the rider feels the base, too thick and seat height rises.

Step-by-step guide

1. 1

   Collect requirements and rider data

   Write the seat requirements: an example seat height of 760–790 mm, seating length for two riders, storage that fits an example open-face helmet, and clearance to a battery box under the floor or bin. From a published Indian anthropometric table, list hip breadth and inside-leg length for an example 5th-percentile female and 95th-percentile male. Draw a side-view layout sketch with the ground line, floorboard, seat H-point region and battery envelope.

   Checkpoint: A requirements table with sources for every rider dimension and a layout sketch with named global variables for seat height and length.

2. 2

   Build packaging envelopes

   Model the helmet as a simple solid from your measurements with a 10 mm allowance all round, and model the battery and controller envelopes as boxes from the layout. Insert them into a packaging assembly with the frame rails. Position the helmet envelope where the bin will sit and confirm there is a path to lift it out when the seat is open. Colour envelopes in a translucent appearance so overlaps are visible.

   Checkpoint: Interference Detection between the helmet envelope, battery envelope and frame shows either no overlap or a list of conflicts you then resolve.

3. 3

   Surface the seat top

   Sketch the seat outline in plan view and the top profile in side view, then add two or three cross-section sketches. Use Boundary Surface between the sections with the side-view curve as a guide, keeping tangency at the edges. Make the front narrow enough for flat-foot reach and the rear wider for comfort. Check the surface with Zebra Stripes and Curvature display to remove dents before thickening.

   Checkpoint: Zebra Stripes run smoothly across the seat top with no kinks, and the front width at the knee point matches the requirement.

4. 4

   Create foam, base and cover

   Use Offset Surface downwards from the seat top by an example foam thickness of 60 mm at the rider zone and less at the pillion zone, then Thicken or Fill to make the foam body. Create the seat base as a 3 mm moulded shell below the foam with a stapling flange around the edge. Add ribs on the underside, a hinge boss at the front and a latch striker at the rear.

   Checkpoint: Foam and base are separate bodies with no gaps, the base wall is uniform and ribs meet the wall at less than full thickness.

5. 5

   Model the storage bin

   Design the bin as a separate moulded part that hangs from the frame, with a drain hole, a light pocket and draft on all walls. Build a filler body inside the bin cavity with Intersect or by offsetting the inner faces, then use Mass Properties on that body to measure the usable volume. Confirm the helmet envelope fits and that the bin floor clears the battery envelope by your stated margin.

   Checkpoint: Measured bin volume meets the target, the helmet envelope fits without interference and the floor clears the battery envelope.

6. 6

   Add the hinge and latch

   Model a simple hinge with a pin and two brackets, and a latch with a striker on the seat and a hook on the frame. Mate the seat with a concentric hinge mate and an angle mate with limits from closed to an example open angle of 75 degrees. Add a stay or gas-strut envelope. Create Closed and Open configurations so drawings and clearance checks can use both positions.

   Checkpoint: The seat opens to the full angle without hitting the grab rail or body panels, confirmed by Interference Detection in the Open configuration.

7. 7

   Check rider fit

   Build a simple 2D rider sketch from your anthropometric data and place it on the seat for the small and large rider. Measure the foot-to-ground distance at a stop for the small rider with the seat compressed by an assumed foam squash, and the knee clearance to the front panel for the large rider. Change the seat front width or height if either check fails, and record the change.

   Checkpoint: Both example riders meet the flat-foot and knee-clearance targets, or a documented trade-off explains why one does not.

8. 8

   Check base stiffness

   Run a linear static study on the seat base with polypropylene or a glass-filled grade from the material library, fixed at the hinge and latch points. Apply an example distributed load of 150 kg over the two seating zones using split lines, multiplied by a dynamic factor you state. Use a mesh fine enough for two elements through the wall. Report maximum deflection and stress, remembering plastics creep and need margin.

   Checkpoint: Peak deflection is under your limit, for example 3 mm, and the factor of safety on yield is above 2 for the stated load.

9. 9

   Drawings, renders and report

   Produce drawings of the base and bin with section views, draft notes, wall thickness and ISO 2768-m general tolerances, plus an assembly drawing with a BOM. Render the seat with a leather-look cover in SOLIDWORKS Visualize. Write a report with the requirements, rider data, volume and clearance results, stiffness check and a list of assumptions, such as foam squash and dynamic factor, that need physical testing.

   Checkpoint: A report with drawings, measured storage volume, rider-fit evidence and the stiffness results with stated assumptions.

Testing & validation

• Storage volume measured from a filler body meets the target and fits the helmet envelope.
• Seat opens fully with no interference.
• Flat-foot and knee-clearance checks pass for the example riders.
• Base deflection and stress stay within the stated limits.

Expected results

A seat, base and storage bin assembly with measured storage volume, hinge clearance checks, rider-fit sketches, a base stiffness check and production-style drawings.

Take it further

• Make a seat-height design table for low and standard seat variants.
• Model foam as a hyperelastic material in a nonlinear study to estimate contact pressure.
• Add a USB charger and light in the bin with a cable route.

Viva and review questions

Learn it at DIYguru

These DIYguru courses and programmes teach what this project needs.