The Rudge ‘Revulator’

One of the great things about old motorcycles, their history and the people involved, is there’s always something new to learn. Many Rudge enthusiasts will know all about this topic, but although I have a Rudge in sprint trim, I didn’t.

With his Christmas card, lifetime Rudge enthusiast Dave McMahon (REC President and VMCC Vice-President) enclosed a couple of gems – replica printed dials for the Rudge ‘Revulator.’ Like many, I’m familiar with the Triumph speedometer with

‘rev indicator’ and one is fitted to Rusty, the 1948 Triumph 3T lurking in the workshop, but the Revulator was new to me.

Along with the Regulator replica dial faces, Dave enclosed a photocopy of its instructions, which read:

“The Rudge Revulator or revolution counter is a simple instrument which provides most of the advantages of a revolution counter, without the added complication or expense. It is in effect a static revolution counter.

“The instrument consists of a graduated dial swept by a cursor. The dial has five graduated scales, the inner being in miles per hour, or kilometres per hour for Continental machines. The outer scales give revolutions per minute of the engine for the various gear ratios throughout the speed range. The first, second and third gear scales end at the safe figure rpm appropriate to those gears.

“To operate, the rider rotates the cursor to coincide with the number of miles per hour (or kph) and then obtains a direct reading of the number of revolutions per minute the engine is making according to the gear he is employing.”

Setting up examples, we will discover that if one sets the cursor at 20mph, the Rudge engine would rev at 3800rpm in first gear, 2100rpm in second, 1600rpm in third and 1300rpm in top. Doubling the speed to 40mph, the Revulator informs first gear shouldn’t be used and the engine would rev at 4150rpm in second, 3150rpm in third and 2600rpm in top. And at 80mph, the engine will be spinning at 5100rpm in top gear.

In appearance, the complete Revulator comprised a period style speedometer or rev counter shell with the mentioned dial and cursor within. A spindle with external knob protruded through the glass to permit the rider to operate it. Dave informs the Rudge Revulator was introduced in 1935, but was never offered for the 250cc models, and as H G (Henry George) Tyrell-Smith (19071982, TT winner, ex Rudge and later Excelsior works rider and Triumph employee after the Second World War, until circa 1952) confirmed, Smiths, on Triumph’s behalf, in effect copied the Rudge Revulator basic concept when creating the dial for the Triumph speedometer with rev indicator.