Wow, I rode on the Encino velodrome for a few years and never used a front chainring that big. Most modern and vintage track bikes that I have and have seen have front chainrings smaller than 54T.
Crank arms are 7.5” overall and there is a B stamped on the inside.-----
what is the length?
for Brampton of this era one would expect 6 1/2"
what is the wedgebolt size?
for Brampton one would expect 3/8" / 9.5mm
a 9.0mm wedgebolt would suggest a continental origin
what is the chainwheel bolt thread?
are chainwheel teeth cut for 1/8" or for 3/32" chain?
this is a frankish producer of cycle fittings which was active in the 1930's and 1940's. do not have start/stop dates for them.
in addition to chainwheels, pedals, tools, and number plates were offered. found one report that they did a derailleur in cooperation with Freres Huret; it was product nr. 3716.
ALUVAC alloy pedals on a REXA machine of the 1930's -
Number plate -
Any idea what the B could mean? It’s on both arms.----
Trade convention for crank length measurement is center of spindle hole to center of pedal hole.
Appears they are 6 3/4" / ~170mm which is the continental standard for adult machines.
AFAIK the letter B does not necessarily make them Brampton.