Gear Update - October 15, 2023

This post describes changes in my gear since I published Gear Update - June 26, 2023. Before describing those changes I need to summarize some history starting almost three years ago.

In December of 2020 I installed the Shimano Dura Ace SP-7400 seat post I had recently bought and then attached my rear rack to the seat tube. Unfortunately the seat post was not long enough to protect the seat tube from the force of clamping the rear rack, which resulted in the seat tube being dented. At the same time I noticed the beginning of a crack in the left seat stay (December 10, 2020 - Preparation for the trip December 11-13, 2020 and Gear Update: Saddle, seat post, and cassette).

Although I could ride my bike with its dented seat tube and the crack in its left seat stay, I posted a message in several bike forums describing the problems and asking for solutions. David Brorein, an expert machinist, wrote that he thought he could fix both problems. He inspected the damage and offered to make the repairs, which he did in July of 2021 (Gear Update - July 12, 2021).

Extension to Seat Post

After David repaired the seat tube I installed a cheap seat post long enough to protect the seat tube from the rear rack (Gear Update - September 22, 2021). But I thought it might be possible to create an extension for the Dura Ace SP-7400 seat post so that it would protect the seat tube when the rear rack was installed. I don't have the skills to do this, so I asked David whether he could do it, which he did by turning a piece of scrap aluminum on a lathe.

Below you can see the seat post and the extension. The extension itself measures 100 mm and for maximal strength was designed to extend as far as possible, about 87 mm, into the into the seat post.

Initially the extension had a small bore, leaving a lot of excess aluminum.

David increased the bore in order to reduce the weight.

Here's the view looking straight up the extension.

Here's the seat post with the extension installed. Isn't it beautiful?

The seat post weighs 9.45 ounces while the extension weighs 3.77 ounces, bringing the total to 14.22 ounces. The seat post has a length of 200 mm and the extension adds 100 mm, bringing the total to 300 mm, which makes it the longest Shimano Dura Ace SP-7400 seat post in existence.

The extension reaches about three inches below the bottom of the rack's clamp.

Repair of Cracks in Seat Stays

Although David's repair of the crack in the left seat stay by brazing with bronze initially seemed successful, eventually the crack reappeared through the bronze, and an additional crack appeared in the right seat stay.

In August of 2023 I noticed that the crack in the left seat stay had gotten much worse, as you can see in the video below.

The crack in the right seat stay had also developed. Eventually both cracks were complete. In order to continue riding I applied advanced redneck engineering. I consider it advanced redneck engineering because I used zip ties rather than duct tape.

I did not know how long the zip ties would continue to maintain the integrity of the frame, so David and I met in October of 2023 so he could repair the cracks. He did this by TIG welding the outer faces of the seat stays with Weld Mold 880 and and the inside surfaces of the seat stays with bronze.

The repair of the cracks in the seat stays and the installation of the seat post with its extension brings to an end the trouble that began almost three years ago. The integrity of my frame is restored and a beautiful Dura Ace seat post with its extension is protecting the seat tube from damage by the rear rack. David has said that he wants to smooth out the welds to make them look better, and then there is the matter of touching up the paint in order to protect the frame.

I'm grateful to David Brorein for his outstanding work. Thank you, David!

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