Big Four Tractor Restorations: A Global Endeavor

Minnesota machinist plays role in restoration of 11 Big Four tractors.

| March 2014

  • The differential assembly from the 1910 Big Four tractor.
    Photo courtesy Harriet Severson
  • This photo of a Big Four engine show the cylinders set in place and the water manifolds bolted on, confirming alignment and correct spacing between the cylinders.
    Photo courtesy Harriet Severson
  • In the midst of the cylinder machining process for the 1910 Big Four.
    Photo courtesy Harriet Severson
  • Aluminum piston castings for Big Four pistons in the background are flanked by finished pistons for another Big Four tractor, along with bearing caps and wrist pins.
    Photo courtesy Harriet Severson
  • No detail is too small in refurbishing the 1910 Big Four, including foundry-made lugs for the wheels.
    Photo courtesy Harriet Severson
  • When Al Severson needed to make the steering chain spring assembly for the Big Four, it required a lot of searching to find the correct spring to match the original. “I was able to obtain it from John Deere,” he says. “I told John Deere that at one time they marketed the Big Four, so they should have parts in stock.”
    Photo courtesy Harriet Severson
  • Like almost everything on the Big Four, this steering assembly is double-nutted.
    Photo courtesy Harriet Severson
  • Al made most of the parts for his Big Four, but he bought this Bennett carburetor, said to be a new old stock carburetor. “I have to believe that to be correct,” he says. “There are no signs of wear in any of the holes and all the detents look to be new. It is complete with the water injection.”
    Photo courtesy Harriet Severson
  • A pattern had to be made for the differential drive gear for the 1910 Big Four tractor, which was equipped with three speed options. Al chose a low speed to match the original differential gear. To make the pattern, he used medium-density fibreboard in 3/4-inch sheets. He cut the sheets into circles, glued and screwed them together to make a 5-inch part, then used a lathe to true the pattern. A rotary table was used to index the gear for the tooth cutting. This is the finished pattern ready for the foundry.
    Photo courtesy Harriet Severson
  • A restored Big Four on display at the Little Log House show, Hastings, Minn. A restored Big Four is a spectacle, Al says. “It looks like a
carnival coming to town,” he says. “It’s a very
 ornate tractor.
    Photo courtesy Harriet Severson
  • An original Big Four dealer sign from Al’s collection.
    Photo courtesy Harriet Severson
  • Al’s second Big Four, a 1908 model. “We set the backlash in the pinion gears and removed the rear wheels so it was at a good work height,” Al says. “We set the engine we had been working on for our tractor and the transmission that Bruce Flatmoe had built for this tractor on the frame. The backlash between the transmission and the differential were then set and we are working on crankshaft to transmission shaft.”
    Photo courtesy Harriet Severson
  • Al made a copy of an original wench for the threaded cover for the intake valve chest, shown here before drilling and threading the spark plug hole.
    Photo courtesy Harriet Severson
  • Not only do the parts for the engine and transmission have to be made, so do fixtures to make those items. This piece allows Al to mount connecting rods in either a vertical or horizontal position for machining.
    Photo courtesy Harriet Severson
  • One of the first purchases Morris Blomgren made, at considerable expense, for his Big Four tractor was master pinions. Here, Al remachines them for casting of new ones.
    Photo courtesy Harriet Severson
  • Recently poured connecting rods and caps for a Big Four engine.
    Photo courtesy Harriet Severson
  • A colorized photo of a Big Four threshing in an Indiana field.
    Illustration courtesy Bill Vossler
  • A colorized card showing a Big Four plowing in a field near Beach, N.D.
    Illustration courtesy Bill Vossler

Ever wondered how to define the phrase “mind boggling”? Just ask Al Severson. The Blooming Prairie, Minn., machinist is juggling the restoration of not one but 11 Big Four tractors.

Fortunately for Al’s mental health, only two Big Four tractors (both of which are his) are physically present in his shop. The rest are scattered across the globe, but the Internet has brought them close together. When Al documented the experience of restoring a Big Four and posted it online at Smokstak, owners of the rare prairie tractors started coming out of the woodwork … and they all needed parts and information.

In addition to his own pair, Al is involved with restoration of four Big Four tractors in the U.S., three in Australia and one each in South Africa and the Netherlands. “All I send to owners overseas is information,” he says, “typically sketches or prints of different parts of the tractor, because I don’t want to deal with customs and all that. It works both ways. I help them out; they help me out with information, too.”

The group of 11 enthusiasts on four continents is tight-knit; members freely share information and parts. “It has truly become a worldwide group,” Al says. “If one person has a part you need and we have a part they need, we work together and everybody is satisfied. We end up being the central point for most of the parts being made for the Big Fours in the U.S.” Some need only minor parts; others require complete engine and transmission rebuilds — but he is up to speed on all of them.



The Big Four, a member of the class known as prairie tractors, is a rare tractor; just 25 are known to exist. The Big Four was built by Gas Traction Co., Minneapolis, until 1912, when Emerson-Brantingham Co., Rockford, Ill., bought out Gas Traction. Emerson-Brantingham continued to build the Big Four for several years.