Tail bike light
A clip-on rear light for Loop Cycles (sample): four models, 16 weeks.

The brief
A rear light that clips to any seatpost without tools and lasts a week of commuting on one charge.
Client
Loop Cycles, bike accessories (sample)
My part
Concept, prototypes, factory support
Models
4 in 16 weeks
Status
On sale (sample)
Tail bike light
A rear light that clips to any seatpost without tools and lasts a week of commuting on one charge.
Client
Loop Cycles, bike accessories (sample)
My part
Concept, prototypes, factory support
Models
4 in 16 weeks
Status
On sale (sample)
cm
M1 Foam
Size on the seatpost
Week 1
M2 Print
Clip fit, 25 to 32 mm posts
Week 3
M3 Rig
Light pattern and battery
Week 6
M4 Sample
Shipped
Week 16
Tail rear light for Loop Cycles (sample): four models in 16 weeks. All models drawn to the same scale, ruler in centimetres.
What each model changed
Model by model, in the order they were made. Test figures are samples.
M1
Foam blocks taped to six bikes showed the light had to be under 7 cm, or it hit saddle bags.
M2
Printed clips were tried on posts from 25 to 32 mm; a rubber shim covers the whole range.
M3
The rig ran for 41 hours on the flashing setting (sample test), enough for a week of commuting.
M4
The factory sample passed the rain test; the button moved 3 mm to work with winter gloves.
See the other projects
Every case study is drawn as its line-up, model by model.