Not Greeves but......

[John Wakefield]

This article appears in OBM this month featuring a Villiers V twin based on the 2T engine. It had previously been mentioned in OBM as a 'Greeves 4' which of course its not

[Colin Sparrow]

Sounds like one of my April Fools. What date was the article..?

[John Wakefield]

Sounds like one of my April Fools. What date was the article..?

Its no April fool joke, the bike exists in the Sammy Miller Museum, article in the May OBM received today.

[Brian Catt]

Oh yes it's real enough! The only question is....did the designer realise it would not have any primary compression when he designed it?

[Colin Sparrow]

It must have two cylinders firing together, fed by a common crankcase. In other words both right hand cylinders fire, followed, 180 degrees later, by both left hand cylinders.

I saw a flat-twin two-stroke once that operated in the same way - it must have had a crankshaft with two crankpins, because both cylinders fired at once. Or so the owner assured me...

[John Wakefield]

Oh yes it's real enough! The only question is....did the designer realise it would not have any primary compression when he designed it?

Yes he did Brian, if you read the article you will see it has a supercharger fitted!!

[Brian Catt]

Yes........but did he realise that before he fitted the charger, or was that a OOps need more primary compression moment?
Colin the big-ends are on 2 common crankpins, so, for example, the 2 right cylinders fire at 90 degrees to each other. They share a common primary compression, which while some would be present, would be woefully lacking to feed both pots.

[John Wakefield]

Yes........but did he realise that before he fitted the charger, or was that a OOps need more primary compression moment?

I am sure he did, this is the work of a skilled engineer, not some back street bodger, the crankcases were specially cast. The blower method of maintaining primary compression would have been well known from the Commer & Foden two stroke diesel engines.

[Colin Sparrow]

Yes........but did he realise that before he fitted the charger, or was that a OOps need more primary compression moment?
Colin the big-ends are on 2 common crankpins, so, for example, the 2 right cylinders fire at 90 degrees to each other. They share a common primary compression, which while some would be present, would be woefully lacking to feed both pots.

Of course, I was writing nonsense. The blower is the key isn't it? Guess I'd better read the article..!

[Brian Catt]

View of the timing side showing a nice big carb and the drive to the blower. Note the tacho drive from the blower shaft.