The Smell of Molten Projects in the Morning

Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.

Another Fractured Seat Strut Screw

Having replaced both screws back in March, I wasn’t expecting this:

Fractured screw surfaces
Fractured screw surfaces

Of course, it broke at the first pedal stroke while pushing off across an intersection, which is why I never try to ace out oncoming cars.

This was, mercifully, on the left side of the bike, so I could replace it without removing the rear wheel. Being that sort of bear, I now carry spare screws and we were back on the road in about ten minutes.

A closer look at the head end of the screw shows some interesting details:

Fractured screw - head
Fractured screw – head

The tail end has matching cracks:

Fractured screw - tail
Fractured screw – tail

Notice how the cracks are all oriented in the same direction. The screw fractured at the edge of the brazed-on frame fitting, so I suspect the seat stay clamp must be moving just enough to flex the screw across that plane.

I mooched a pair of hardened socket head cap screws from Eks, ground down the head of the right-side screw for better chain clearance around the sprockets, buttered ’em up with Never-Seez, and we’ll see how long Real Steel lasts.

Right-side screw with ground-down head
Right-side screw with ground-down head

I really should conjure up a clamp that mounts to the frame tubing, rather than depend on that puny brazed-on fitting, shouldn’t I?

It appears that new Tour Easy ‘bents come with more brazed-on fittings and a more secure seat stay mounting bracket. A photo was there when I looked.

Comments

2 responses to “Another Fractured Seat Strut Screw”

  1. Tour Easy: New Rear Brake « The Smell of Molten Projects in the Morning Avatar

    […] The Smell of Molten Projects in the Morning « Another Fractured Seat Strut Screw […]

  2. Kuba Ober Avatar
    Kuba Ober

    Looks like classical layered growing of a fatigue crack.