Part 8: More Testing & Fine Tuning

More Testing & Fine Tuning

On one of my early test rides I stopped to adjust the seat and noticed a problem. One of the spring-plunger knobs was gone. The prototypes used aluminum plungers with a small, two-piece knob: about 5/8" in diameter and roughly 3/16" thick. The cap was threaded at the top of the plunger. During the ride it had unthreaded and fallen out.

Spring plungers Upgraded: Increased the knob size to 1" in diameter and 1/4" thick, and changed the material to 304 stainless steel for strength and corrosion resistance.

I brought the seats back to the bench and decided to fix the hardware, not the symptom.

What I changed

• I increased the knob size to 1" in diameter and 1/4" thick so it is easier to find and pull, even with gloves.
• I moved the threads into the knob and increased thread engagement to roughly double the previous design.
• I changed the material to 304 stainless steel for strength and corrosion resistance.
• I added thread locker at the threaded connection.

This added cost to the seat, but it was the right call. The new plungers are easier to grab, the threads are much stronger than aluminum, and they look great on the seat!

We received the new stainless plungers, installed them on the prototypes, and put in several hundred more miles of riding. No loosening. No parts lost. The knobs pull smoothly, the slide feels consistent, and the lock is positive.

Takeaway
Small hardware changes make a big difference in day-to-day use. The stainless plungers with larger knobs solved the loosening issue and made on-ride adjustments easier and more reliable.