Miller Big 40 Engine Drive Welder

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Miller Big 40

A discussion of Engine Drive welders would not be complete without talking a bit about a classic engine drive welder, the Miller Big 40. This Model has been around for years, but what it stands for has changed. Ours is a 1979 model and far from the oldest 'Big 40' on the planet. Miller has long since gone to a 3 digit numbering system, but they have kept the Big 40 model on the market even though it overlaps newer monikers that they sell.

There has been a lot of evolution in the last 25 years to say the least. The Big 40 of 25 years ago was approximately a 300 amp continuous duty machine with a 4 cylinder water cooled Continental Gas engine. It would push 1/4" Carbon Arc rod and welded very nicely. As you can see however the control panel is very Spartan. There is an Amperage Range selector, a 100 Amp Fine amperage dial and that is it for the welder controls. For the engine you have a Choke, starter, and auto idle on switch, and yes there is a 20 amp 110 volt AC plug in and that is what you got---a basic DC welder with about 3,000 watts of AC power available.

To be Sure it is a good welder with a modest 1800 RPM engine speed. The only luxury on the machine is the gauge set. Not even an hour meter is present. The bottom left photo is a different welder than the top one. Ours is buried in a welding truck and that top part is all that sticks out. The bottom photo is a 'typical' Big 40. Note that it even lacks the gauge set.

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MILLER Big 40 (2005)

By contrast the Big 40 of 2005 is a luxo wagon. IN 2005 the Big 40 is a 400 AMP welder that will go to 450 amps at 60% duty cycle powered by a 3024C Caterpillar Diesel rated at 33hp. It sells for a premium price over the 33 HP Big Blue 400 of the day which offers a 33 HP Perkins Diesel. Never mind that Caterpillar owns Perkins. It is unclear to me if the engines are even different. The Big 40 and the Big Blue 400 come in the same case with the with the same weight and features except for one thing. The Big 40 offers an additional weld mode and what Miller calls a "Dig" mode which is similar to a standard feature found on Lincolns called there "Arc Force".

The Deluxe Model offers 12KW of 1 phase power and 15kw of 3 phase power. Having owned a Big 40 we carefully considered buying another one instead of the Lincoln Vantage 400 reviewed elsewhere on this site. What we found was that the Big 40 had a $2500 higher list price (in December of 2005) by the time you ordered the Deluxe model, and for the extra $2500 you got a 25 gallon Fuel tank instead of a 15 gallon tank, a machine that was 300 lbs heavier, one advertised to do AC TIG, (with the addition of a high frequency unit), and one that would produce 15kw 3 phase power compared to the Lincoln Vantage 400 that would produce 19KW.

For what it is worth we bought the Lincoln. IT seems that Lincoln had their head up their back side for a long time, and though historically they made a good welder, it was based on a DC generator and was heavy and expensive. Miller used a lighter Alternator and an inverter to produce DC power. If you look around for welders in the back of trucks until the last couple of years you saw nearly all Blue ones. Now You see some Red ones. Lincoln has met Miller on Miller's turf feature for feature on the low end air cooled gas drive welders, and on the high end (such as here) produced first the Lincoln Commander series and now the Vantage Series that simply have more performance and more features for less money than Miller. The Lincoln Vantage series is bound to seriously beat up Miller if Miller doesn't respond with a machine that is closely competitive to the Vantage. We looked very closely at both the Big 40 and the Big Blue 400 which are for the most part very similar welders (the Big Blue 400 doesn't offer the AC Tig Feature).

As I write this in January of 2006, Miller is making some web site changes, raising prices of some of the low end machines and it isn't yet clear what if anything there are doing with the high end machines but clearly they need to rethink their strategy if they are going to stay in the market on the high end.

Big Plasma Cutters are now something that every welder jockey wants but to make them work you need an air compressor, and a Lot of AC power---preferably 3 phase power. Now both Miller and Lincoln offer 'Air Pak' welders that have a 500 amp (or more) weldere combined with an air compressor, but those are priced in the $18,000 range and are aimed for big carbon arc gouging, not for driving a plasma cutter. The electrical Engineer who figures out how to integrate a plasma cutter into the basic engine drive welder (even if it takes an external air supply) will have a path beaten to his door if he an do it for a modest extra cost. Meanwhile, Miller needs to offer more than 15KW AC power on their 400 amp units.

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