As you get closer to the Gozaisho Ropeway, one thing never fails to catch your eye – the “White Iron Tower”!
The “6th Supporting Tower”, as it is officially known, is a ropeway supporting tower that stands on Mt. Gozaisho at an altitude of approx. 940m (3,084ft). With a height of 61m (200ft), it is proud to be the tallest tower of its kind in Japan.
When the ropeway commenced operation in 1959 it was green, just like other towers. However, it was repainted white in November 1961.
This strikingly-white iron tower can even be recognized from the Chita Peninsula over 40km away and has become the symbol of the Gozaisho Ropeway. The base of the tower covers an area of approx. 140m2 (1507ft²).
Fixed using rivet joints like Tokyo Tower
All the metallic pieces of the tower were fixed using an advanced technique called riveted joints, not the more contemporary bolted joints. A rivet is a mechanical fastener. Most joints in steel structures had previously been riveted until high-strength bolts started to be commonly used.
A rivet, which consists of a steel bar cut to a certain length with a head on one end, was heated to glowing hot and placed into the hole that was to be riveted. Then the other end without a head was hit with a rivet hammer to shape the head and tighten the joint. The work of shaping the head, which was called “kashime”, required experts with advanced techniques.
On site, four to five men made up one team. The three who were in charge of riveting (catcher, holder & riveter) were stationed up the tower near the joints, while the remaining two were responsible for heating the rivets in a furnace on the ground. The holder received a heated rivet from the catcher, placed it into the hole to be riveted and held the round head of the rivet in place. The riveter then applied a rivet hammer to the unformed head to tighten the joint. On the ground the team leader heated rivets and the other man performed miscellaneous tasks such as carrying rivets and supplying coke. The leader prepared rivets of the size fitting each joint, taking into account the speed and order of riveting, and heated them by judging their temperature from their surface color. The appropriate temperature is 700 to 800°C (1,292 to 1,472ºF). If the temperature is below that range the rivets will become too hard, while if the temperature is above this range, they will melt and become too soft. In either of these cases, the rivets would become defective. The leader used tongs to remove rivets and threw them vertically upward sometimes to a height of 20m, and the catcher stationed above near the joints caught the rivet in a funneling-shaped device. As rivets could be thrown in a curve by mistake and the catcher could fail to catch them, this work was very dangerous. Throwing red-hot rivets up and catching them high in the air looked like a form of acrobatics.
The “6th Supporting Tower” under construction (It was the world’s highest at the time.)