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For this tear-down assignment, I chose to investigate an inexpensive flashlight. For $1.99, I acquired the marvel of modern engineering otherwise known as the Trisonic Torchlight TS-97B-11T.

Here’s the last time it was seen safely in one piece:

The first step in disassembly involved unscrewing the front-most black piece, easily done with the handy finger grips in its rubbery plastic surface. This functions as both the gateway to the battery compartment and the joining mechanism for the ‘lens’ components.

Once unscrewed, the front piece freed the three hard plastic pieces above:

• lens – clear plastic, used to protect the bulb
• reflector – grey plastic painted chrome, used to diffuse the bulb’s light
• ring – red plastic, this ring sits between the front and rest of the battery chassis where they screw together. Its purpose is unclear, but perhaps functions as a washer to avoid stripping/excessive friction in the join. Or it may just be decorative.

Nestled within the reflector was the bulb, which was glued together and impossible to dissect further without shattering the thin plastic exterior.

Clipping onto the base of of the reflector is this plastic disk, which holds the bulb in place and is presumably the diameter of the chassis interior in order to maintain stability of all pieces within the chassis.

Beneath the disk is a black plastic cap that screws onto the bottom of the reflector. At the bottom of this cap is a small metal piece that would serve as a conductor between the bottom of the bulb and the batteries below.

At this point, there is no further disassembly to be done with bare hands:

Tug as I might with pliers, the metal coil and conductor refused to budge. So it was time to resort to the small hand-saw, part of my multi-tool. Things got much hairier very quickly.

The main body of the the flashlight actually consists of an inner and outer layer:

• chassis – the inner layer and the flashlight’s rigid plastic skeleton, the chassis houses the batteries and electrical components and screws into the lens and bulb apparatus. (It was more fragile than I anticipated, and snapped along the seam when I sawed down to the button.)
• grip – the ‘skin’ of the body, this more malleable, rubbery plastic makes for a satisfying grip and enables the soft click of the on-off button. (It also clips to the string wristband, which I did not bother cutting off for this exercise.)

Partially damaged by my sawing was the hero of the show, the switch:

The white plastic switch sits in a crevice between the cup and shaft of the chassis (the weak spot where the chassis snapped), between the chassis and grip. The long metal conductor strip extending from its bottom runs along the exterior of the chassis and folds into the chassis’s interior, clipping around the base of the coil (which is what the batteries sit on at the bottom of the chassis).

Here’s a look at the disassembled switch, which consists of:

• button – a white plastic cylinder, solid on top and hollow on bottom. The four small nodes extending from its base are perpendicular, and match up with corresponding grooves in the…
• top – a rounded rectangle plastic case which an elongated aperture at top that snugly houses the button. It clips neatly onto the base, which has the same profile.
• base – the backing and foundation for the switch, it features pegs that clip into the top, through holes on the conductor strips to hold them in place. it also has a central peg that supports the…
• spring – the component that provides the persistent resistance that keeps us coming back for more! Atop it sits the…
• conductor-disk  – this sombrero-shaped metal piece is what connects (or does not connect) the conductor strips when the flashlight is switched on (or off).
• conductor strip (small) – the smaller of the two strips, this one runs up from the top of the switch, back into the chassis, and interfaces with the top of the battery and bottom of the bulb.

 

Learnings

I’m still mystified by a few steps in the production process, but I have confidently concluded the following:

• All plastic pieces were created using molds.
  • Longer circular pieces (reflector, chassis, grip) have bisecting seams, suggesting they were created as two separate pieces and then joined.
  • Shorter circular pieces (front, lens, ring, cap, disk) have no seams, and were likely single-mold productions.
• My inferred assembly order is as follows:
  • bulb (a unique part created at a separate time, possibly by a third party)
  • switch internal components
  • coil is dropped to the bottom of the chassis
  • switch and conductor strips are placed on outside of chassis; conductor strips are run into the corresponding crevices to the chassis interior
  • grip is folded onto chassis (possibly when its two halves are joined)
  • cap and conductor are joined; bulb is slipped into back of reflector
  • disk is clipped onto back of bulb + reflector
  • cap is screwed onto bottom of reflector, joining the bulb to reflector
  • ring is slipped around neck of chassis; lens is clipped into front
  • front is screwed onto chassis, flashlight is complete

Impressions

I was amazed by the elegant simplicity inside such an inexpensive device. Two general features stood out to me in particular:

texture – The repeating square pyramids along the grip’s handle had just the right about of tack to keep the light firmly in hand, even when held in a variety of positions. Any larger or smaller and they might have become invasive or pointless, but they were the perfect size. Additionally, the decision to comprise the reflector’s convex interior of many flat-faced hexagons, rather than just one smooth surface, was an interesting one. This must help diffuse light in more directions, as a smooth surface would likely have been easier to manufacture.

durability – Cheap things typically break easily, but this flashlight seemed very resilient—even if it couldn’t withstand my saw. Its exterior surface was the perfect mixture of hard and soft to cushion and withstand a sizable drop, and its key component—the switch—was in a well-protected spot, very difficult to remove. It seems $2 still goes a long way, some times