Radial Engine Motorcycles – Redrup Radial

Redrup Radial 3 cylinder engine

Redrup Radial 3 cylinder engineThe Redrup Radial engine is new to me but it's actually quite old. After all of our coverage of radial engine motorcycles using the Australian Rotec 7 cylinder radial like the one built by Jesse James and the radial motorcycle built by JRL Cycles that they actually plan to produce, I received several pointers to the Megola radial engine used in a motorcycle many years ago where the engine was mounted in the front wheel. But no one mentioned the little Redrup.

The Redrup Radial was a 3 cylinder, 120 degree radial engine displacing 309cc. I ran across a short article in the October issue of The Classic Motorcycle that said it was built in the UK from 1919 to 1922 though actual numbers built are unclear and probably less than 150. The engine was designed by Charles Redrup, an aeronautical engineer and the "Redrup Radial" as the motorcycle was known, was assembled by a close friend of his, Monty Beaumont.

Digging around for photos of this motorcycle lead to an interesting outcome, three photos and each had the engine mounted on a different axis. The latest of these, the red motorcycle at right, was actually built later by Charles Redrup and his son after WWII. The engine was a smaller 250cc version with the crankshaft in a vertical position and mounted in a Royal Enfield frame.

Interesting stuff and another indication of neat ideas that have come before.

Photos sources:
Image above from October 2006 The Classic Motorcycle
Image of red Redrup: Stu Savory
Image below: CyberMotorcycle

Photo below:
Redrup Radial 3 cylinder engine


  1. says

    vertical crankshaft — interesting.

    Didn’t Moto Guzzi have a prototype where there was a 3rd cylinder in between the 90 degree cylinders?

  2. says

    What a co-incidence! My biography of Charles Benjamin Redrup has just been published (see website) and covers the full range of motorcycle engines which he designed, from 1901 to 1948. He built rotary, double-rotary, radial and axial engines.
    He also designed engines for 1st World War aircraft, for Avros in 1926-28, a boat in 1926, an axial engine for a Simmonds Spartan aircraft in 1929, and a series of axial engines for Bristol buses in the 1930s. He worked on Lancaster gun-turret hydraulics for Avro again during the 2nd World War and built radial and axial engines for mororcycles between 1946 and 1948. He designed axial aero engines of 1,000hp and 2,000hp in the 1950s. The red motorcycle is in the Sammy Miller museum.
    If anyone has any more information on Redrup I’d appreciate it, for the second edition of the book!