jdawginsc Good guess on the Japanese cotterless crank but it's a very early Takagi brand not a SR Sakae Ringyo.
Here's the tell: Your crank has a double headed eagle and 2 flutes in the arm. The "BS" caught my eye too and can either stand for Bull S**t or Bridgestone???
SR (Sakae Ringyo) cranks from that era had a single headed eagle and single flute.
Takagi (3 Arrows) was a Japanese crank manufacturer that made steel cottered cranks and single piece Astabula style cranks. In the early 70's they were part of the JBM Marketing Group and were later swallowed up by Shimano. They continued to market 2nd tier cranks under the Takagi brand and catered to the BMX and MTB market up into the late 1980's.
From the 1974 JBM Group Catalog.
Your cranks were some of the first Japanese made aluminum cotterless cranks from around 1972-73. The Japanese euphemistically called the process "Melt Forged" as cast into the SR crank arm... They were injection molded/pressure cast parts with no where near the strength of a forging.
The steel chainrings were swagged onto the cast aluminum crank arm.
The reason why I mention this is that these early cranks from Takagi, SR Sakae Ringyo, Sugino and Shimano all had a tendency to fail at the swagged attachment.
These cranks were made for the export market and used the same size swage as steel cottered cranks. Western riders were 25 to 50+% heavier than the average Japanese person and easily exceeded the strength of the swage which caused the rings to spin on the crank arm.
First generation Sugino Maxi crank with the small swagged area. In 1973 Gitane started using these cranks on their Interclub entry level racing model. Over half of those cranks failed and we had to pull cranks off of new bikes to use as replacements. It took Gitane over 6 months to get us updated replacement cranks!
By 1974-75 the Japanese manufacturers started using larger swage cross sections which mostly cured the problem.
noglider the Campy crank is the the 3320/A Sport model which was part of the Gran Sport gruppo.
They first appeared in the 1974 Campy catalog and were replaced by the 5 arm Grand Sport cranks with 144mm BCD rings in 1977.
I have a set of Sport alloy cranks on my 1973 Holdsworth Competetizone. The 116mm BCD chain rings came as either a riveted together set or bolted together like the OP's. They were listed as available in 49/42, 50/42, 51/42, 52/42 and 53/42 teeth but most were 52-42T
jdawginsc The chain rings on your cranks are mounted wrong. They're on the back side of the spider.
Before the alloy Sport cranks came out in 1974 Campy made an elegant steel cotterless model, the 3320 Sport introduced in 1971. They used the same 116mm BCD chainrings.
Good luck on your project...
BTW, the Polish Coat of Arms has a single headed eagle so there is no connection to Poland...
verktyg
