Compound Confidential

This is where Pulling facts and rumors end up being aired on the Internet. Mostly the sources will be treated as confidential, but if the development is well under way and the Puller(s) is/are happy to let everyone know what they are up to, then it will be attributed. In case you're puzzled as to why I've referred to Compound, it's because at most events the Pullers are housed in a fenced-off section sometimes also known as the Pits.

The last of these pages covered Andy Stevens and 'Big Girl', his International 1040 powered by a V8 2-stroke 8½ litre Detroit Diesel which runs with a supercharger... To say these engines are LOUD is probably something of an understatement. 'Big Girl' was narrowly beaten by 'Noise Pollution' in a public vote for the title 'The Loudest Puller' at the Great Dorset Steam Fair last year. Andy's other Puller, the V6 Detroit 'Twiki' is almost as noisy but on the other hand we have the mystery Andrew Thomas with the 'Batmobile'.

Andrew's Puller is powered by a V6 2-stroke Detroit (same as 'Twiki') and is also supercharged but is fitted with a Caterpillar D6 turbocharger. Result; a (relatively) quiet engine... Why? As far as I can work out it has to do with the velocity of the exhaust gasses.

The as you all realise the exhaust gasses pass through one half of the turbo driving an impeller which is connected via a shaft to the much larger input impeller. Just to make things a little clearer I've included a illustration of how a turbo works...

As I said earlier, because of the design of the Detroit, the exhaust gasses seem to come out at a very high velocity producing that very distinctive 'bark' (once heard never forgotten). It looks as if the turbo impeller act as a 'silencer' by effectively dissipating the 'bang' on the blades therefore muffling the 'bark'. Once you've heard one of these two-strokes going flat out you'll understand why drivers called them 'Screaming Jimmy's', the 'Jimmy' coming from the fact that GM (General Motors) used to produce the Detroit engines. Have a look at this video showing a Euclid TC12 Bulldozer (powered by two Detroit straight-6 engines in parallel) at work. Although there are other machines which you can here working you'll soon be able to pick out the sound of the two 'Screming Jimmy's'...

Dave Williams with 'Wandering Deere' Here we have another Detroit powered Puller, 'Wandering Deere' which has a Turbocharger and is possitively quiet compared to 'Big Girl'.

Here's another little snippet passed on to me by Dave Williams... Most Detroit engines are modular! No matter what the unit, the capacity of the cylinder is always 71 cubic inches (1163.48 cc)! This makes the 'Wandering Deere' (which is fitted with a 8V71T) 9.3 litres. I'm not at all sure why 'Big Girl' has an 8.5 litre V8. I must remember to ask Andy at Welland!