Ethan Rich-UsherMechanical engineer

Work

Adjustable channel drain concepts

Two concepts that set a channel drain to the required fall without the wobble of four-point levelling. Presented to EVERHARD’s CEO and department heads after a three-day design task.

For
EVERHARD Industries
Context
Final-round interview design task, three days
My role
Concept designer
Year
2026
Tools
SolidWorks, Sheet metal design, Injection moulding design
CAD render of a channel drain section with a stackable wedge spacer under the grate frame

Problem

EVERHARD set this as the final-round task for an engineering role, with about three days to develop and present a solution.

Requirements

Channel drains must be laid with a fall, at least 1 in 100 under the National Construction Code, while the grate on top sits level with the finished surface. EVERHARD asked for an adjustable rail system for its Class B to D channels with about 40 mm of adjustment, an internal water seal, a strong anchoring system, full backwards compatibility and potential to extend into the commercial range.

Slide summarising the brief beside a render of an existing channel drain

Design

Most adjustable designs level the grate with bolts or set screws at four corners. Like a four-legged table on an uneven floor, that is almost impossible to set without a wobble. This is a known problem in mathematics, often called the wobbly table theorem, and recognising it shaped the brief: both concepts avoid four-point adjustment entirely.

Slide titled the wobbly table theorem with a sketch of a table on an uneven floor

Concept 1: preset-slot legs

Laser-cut 2 mm stainless legs attach to the existing channel and set its tilt through preset slots, giving about 50 mm of adjustment with no wobble. The legs lock in place for fast installation, double as supports, and can be engraved with the grade at each step. It meets every point of the brief, but adds parts and cost.

Render of concept 1, stainless legs supporting the channel
Concept 1: preset-slot legs.
Close-up renders of the slotted leg design
The slots set the fall without bolts.

Concept 2: stackable wedge spacers

Instead of adjusting the channel, adjust the grate. A two-part kit of a stackable wedge spacer and a flat spacer sits under the existing grate frame. It needs no changes to current channels, keeps their certified strength, interlocks with each other for any run length, and can be injection moulded on equipment EVERHARD already runs. An overlapping lip and a draft angle keep water out and let the part eject cleanly from the mould. The trade-off is that it is less novel and is not adjustable across the full 40 mm.

Render of concept 2, wedge spacers stacked under a grate frame
Concept 2: stackable wedge and flat spacers.
Section views showing the overlapping lip that sheds water
The overlapping lip sheds water and the draft angle helps moulding.

Demonstrator

To show the executive team how the system works, a 1:5 scale section of channel and a set of the stacking spacers were 3D printed and brought to the presentation.

Outcome

Both concepts were presented to EVERHARD’s new CEO and the heads of product, engineering and HR. The panel preferred concept 2, the stackable wedge spacers, as the simpler solution and the better fit for the business.

Next steps

Concept 2 is the one to develop further. It keeps manufacturing in-house on EVERHARD’s existing injection moulding machines and needs no change to the certified channels.