What you do is you take maybe a dozen combines, great big steel machines with giant tires and teeth, weigh maybe 20,000 pounds or so, 20 feet long, 15 feet high, come equipped with big horizontal screws that gobble up crops like pigs at a trough, and you put them out on a mud track and you get the local boys driving them to smash, bash, gouge and rip each other's combine until only one can move. He's the winner.

What you got there is a Kombine Demolition Derby.

"A what? A combine what? Good God, you're kidding," said Brian Olm, spokesman for Deere & Company of Moline, Ill., makers of the fine emerald-green John Deere combines that are the pride of many a farm.

No sirree, Brian.

Thursday evening at the 1985 Indiana State Fair. The afternoon derby is over and everybody's standing around in the rain and the muck wondering if the evening derby -- not to mention four classes of tractor and truck pulls -- is going to be called off, or what.

Don Morgan Jr., winner of the afternoon derby, is telling his girlfriend how he and his big orange 1976 Case combine knocked the daylight out of four other crop-gathering behemoths.

"There was two at one end and two at the other and one in the middle and the guy said go, and so we did," said Morgan. "The two John Deeres went out fast. Both of 'em got it in the rear axle and couldn't steer; all they could do is sort of go backward and forward. So, that left three.

"Then the Gleaner got it. Got his head knocked clean off. That left me and the 303 International Harvester. Well, I tried to back up on him and smack him in the drive belt but he clipped my rear right wheel off so I couldn't steer so hot after that. But I could steer a little using the right and left brake pedals.

"I got the International in front of me and I come up on his drive belt side and hit him good. Then I backed up and hit him again. That knocked his whole drive belt off. Then I did it again. Then another time. I hit him five more times before they made me stop."

Morgan is 19 years old and the son of a farmer. His father, Don Morgan Sr., and he farm a couple of hundred acres in Hazelwood, Ind. Morgan Sr. bought the used combines and rounded up the volunteer drivers -- his son and a bunch of other farmers and farmers' sons -- for tonight's derby.

Morgan Jr. spent maybe two weeks getting ready for tonight, working on his machine, welding steel braces to its weak points and plotting strategy (like turning the big front tires around so their valves were protected from a swiping blow.)

Finding the time was no problem. "Since we lost most of the farm -- up to last year we had a thousand acres but the big farmers knocked us out -- I've got plenty of spare time."

Combine demolition derbys are the latest and some say strangest in a long line of spectator events pitting farm machines against each other or against impossible tasks.

They come at a bad time for farmers, a time when an estimated 10 percent of the country's 2.6 million farmers are facing serious immediate financial trouble and at least 4 percent are expected to fail by year's end. The gloomy farm economy has helped make combine derby's possible and popular -- possible because only promises are cheaper right now than a used combine (new they can cost up to $130,000, six or seven years old they might fetch a couple of thousand) and popular because they seem to offer a bit of revenge at the high-priced machinery that drove so many farmers into debt in the first place.

"I'll tell you," Morgan Sr. said, "there's been some times I wouldn't mind seeing my own out there."

Back in 1929, when the first organized tractor pulls were held in Bowling Green, Mo., and Vaughnsville, Ohio, they were pretty simple affairs. You took some tractors, you hitched them up to some sleds with big weights on them, and you saw which tractor could pull which weight farther. The basic concept hasn't changed -- the centerpiece of a tractor pull is still tractors pulling weights. But the machines sure have. Higher, many of them, than an elephant's eye and painted in fluorescent hues of orange, blue, red and gold, they command more than respect. Hugely powerful, weighing thousands of pounds and developing massive horsepower from overtorqued engines, they are, in fact, scary. Tractors from the mind of Stephen King. Killer tractors! Tractors from hell!

Near the track Thursday night, a silently awed crowd stands in front of one of the superstar machines, Wild Bill Stomper, a pickup truck towering on specially designed Goodyear tires 6 feet tall and 4 feet wide with 5-inch high treads as thick as a farmer's forearm.

"Man, wouldn't you hate to see that pull up next to you at the traffic light," said a fan.

The Stomper has a 482-cubic-inch engine that develops 1,250 horsepower. It uses that power and those wheels to roll over parked cars, crushing them in a cacophony of metal and glass that never fails to get the crowd going.

And getting the crowd going is what this is all about. Tractor pulls have become big business. They are slickly packaged by any one of a dozen promoters and the major events are sponsored by the Red Man Chewing Tobacco people. They draw huge crowds at $8 or more a ticket. A major pull, seen by promoters as "the World Series of Truck and Tractor Pulls," scheduled this weekend in Bowling Green, Ohio, is expected to draw 60,000 people to watch the country's top pullers compete for a $103,000 purse.

The National Tractor Pullers Association sanctions 20 "grand national" Red Man-NTPA events like that one every year, with 16 classes of competition ranging from super-stock farm tractors down to midget garden tractors, with two- and four-wheel drive trucks thrown in.

The monster machines and the "machines destroying each other" shows are all part of the effort to keep the folks and the dollars rolling in, said John Kenney, editor of the NTPA Newspaper.

"All of this is designed to attract more people, especially people from urban areas, to the pulls," Kenney said. "It is part of an effort to show people that tractor pulling has come a long way from its agricultural roots. Too many people think of tractor pulling as Farmer Joe versus Farmer Ed, but that's not the case anymore. Many of the drivers are actually full-time professional pullers."

This is the Indiana State Fair's second Kombine Demolition Derby, both of them courtesy of Ed Hart, a big man in the world of tractor pulling.

Hart stops for a moment from his main job right now, which is testing the mud in the track to see if it really is, as it appears to be, deep enough to swallow a combine whole.

"The idea was invented about a year ago, I believe," Hart said. "Some fellow out west at a small county fair, is my understanding. Being in the business of promoting truck and tractor pulls, I naturally figured that this would be a real good way to get a crowd."

Hart, whose TNT Inc. puts on 60 big-time truck and tractor pulls every year, each one drawing anywhere from 20,000 to 60,000 fans of outside farm machinery, has staged five Kombine Demolition Derbies so far in Georgia, New York, Kentucky and Indiana.

(They are called Kombine to differentiate Hart's shows from those of Ernie Brookings, a rival promoter from North Carolina. Of Brookings, Hart said, with the respect of one professional for another, "Ernie's the man who really put the whole combine demo Derby thing together."

Here's how Ed Hart puts on a Kombine Demo Derby.

First, he finds a local man who knows his way around farm machines to buy a dozen or so used combines (11 started out in Indianapolis, but the show at the Erie County Fair in New York last month had a field of 20).

The gas tanks are removed from their usual location at the machine's right rear end and welded 20 feet above the ground in the combine's hopper. The head, which is the part of the combine that actually strips the stalks clean of their wheat or soybeans, is bracketed with steel braces and welded so it remains stationary, 23 inches off the ground. The head's take-up reel, full of whirling knives and a mite dangerous in Derby action, is removed.

All the glass is knocked out of the windows of the driver's cab 16 feet above the mud. Shoulder safety belts are installed. The local organizer passes the word around to the locals. Anybody who wants to enter a Kombine Demo Derby is free to do so. No previous experience necessary.

Then, the promoter gets all the machines and the drivers down to the mud in front of the grandstand at the appropriate time and someone hollers go. Rules are limited: No getting out of your cab during the contest. Drivers must wear their safety belts and crash helmets. You must hit at least one other combine, at least once every 30 seconds. You're out if your head falls off.

The winner get precisely nothing, at least, in cash. There are, however, rewards.

"It's like when you have an old car that you really hate and just to kill it you go out and smash it up," said Ron Meyers, 45, of Hazelwood, Ind. "I guess what I like is the power in destroying something and having fun doing it."

As Meyers said that, standing ankle deep in mud with Morgan Jr., trying to figure out if they hooked up the Case's right rear axle with a chain to the cab, could they maybe run it one more time on three wheels, the announcement came over the PA system and echoed off the deserted grandstand.

"Tonight's pull has been canceled. Tonight's pull is officially canceled. Will pullers please leave the track." There was no one in the stands to hear; the crowd had long since gone home in the light drizzle, leaving the field and the night to the boys from Hazelwood and the five junked up, battered combines.

"Maybe, we fix these up, we can sell 'em for something," said Morgan Jr.'s friend and fellow driver, Ron Allen.