Cummins built a M11 powered off road truck called the wild thing:
The story goes like this - The semi from hell.(off-road racing vehicle developed by Cummins/Navistar)
Author/s: Rick Sieman
Issue: April, 1995
Many Motorsports magazines have a lot of fun with their April issues by fabricating stories about mythical machines. Spoofs are fun and we all like them. But rest assured that what you read here is not a spoof. Last month, we mentioned the fact that Cummins had actually entered a semi in the Baja 1000. Since a huge amount of interest was generated in this outrageous vehicle, we felt it was certainly worthwhile to follow it up and find out more about it.
THE MAN BEHIND THE SEMI
Bill Savage, owner of T-Mag in Vista, California, is a fabricator who absolutely knows the ropes. Since he's the technical inspector for SCORE, and has been for many years, it's safe to say that Bill has literally seen it all.
But we have to wonder if even Bill could have imagined being given the job of turning a Cummins semi into an off-road racer. The idea was the brainchild of a joint effort between Cummins and Navistar. Cummins wanted to promote the reliability of their new M-11 engine, and Navistar is a moving force behind the growing Global Positioning technology.
ABOUT THAT MOTOR
What's the fuss about a diesel engine? Well, hang on to your spec sheets and check out these numbers: The single turbocharged, intercooled diesel powerplant puts out 370 horsepower ... at 2200 rpm!
But here's the real stunner. It twists out a whopping 1350 lb-ft of torque at a mere 1200 rpm! You got it, sport. At a point of about 400 rpm higher than most engines idle, the Cummins M-11 puts out 1350 lb-ft of stump-pulling torque. Compression ratio is right at 27:1.
This is not a small motor, by any means. When put on the incredibly accurate T-Mag scales, the engine/transmission package weighed in at a whopping 3000 pounds! It was right then and there that Bill Savage decided not to try for a super-lightweight racing rig.
RUNNING GEAR
The stout powerplant is hooked up to an Allison six-speed automatic transmission. Stall speed on the torque converter? A mere 800 rpm! Another amazing fact is that the trans/torque converter in the racing Cummins is totally 100% stock. They chose to run it that way to demonstrate the reliability of the unit.
Instead of the regular cooler for a trans, the Allison uses a true heat exchanger. Shifting is done electrically, and this setup is also Allison-based technology.
Just in case you wondered, they had no trouble at all with the stock trans.
A Dana/Spicer diff is used at the rear, running a 3.80 ratio. It's from the Diamond Series, which is a normal five-ton item regularly found in larger box vans. if you want one, the part number is S-1 50-5.
BIG BUCKS, LONG HOURS, LOTTSA WORK
Bill chose not to use the stock frame as a base, but because of SCORE rules and regulations, he would have to conform the racer to a 9200 Cummins body style and stick to the 152-inch wheelbase, plus or minus a few inches.
A tubular frame was hand made from chrome-moly steel tubing (1 3/4-inch OD by .120-inch wall thickness), and complete construction of the frame and running gear took six solid months of work.
Up front, Bill made a twin-beam-concept front end similar to a Ford. At the rear, a standard four-bar link was used.
Since the Cummins was huge to start with, Bill could have literally built in as much travel as he wanted, but instead chose to keep it conservative. You can find 22 inches of travel up front and 28 inches at the rear.
At first, it was feared that the finished package would be too tall and too top heavy, leading to flop-overs in rough off-road racing conditions. Since the Cummins taped in at 9 1/2 feet tall, they had a right to be concerned. But once out in the field, they found that flop-over was a non-issue and that the semi was amazingly stable.
SO YOU WANT TO KNOW MORE?
And who wouldn't? Bill gave us all the inside scoop about the Semi from Hell:
The Cummins carried 160 gallons of regular old pump diesel fuel in two separate 80-gallon fuel cells. It was estimated during testing that they would get six to seven miles per gallon under normal race conditions, meaning they could run the entire Baja event without refueling.
* Coil-over air shocks were used at the front and regular hydraulic shocks used at the rear. Two shocks per wheel seemed to be right during testing, but on race day, it was not quite enough. More on that later.
* Hefty heim joints were used at all pivots; most of them were 7/8-inch bore aircraft-quality stuff.
* Wheels are aluminum slugs from Alcoa: they're 22.5items. The Goodyear tires are 42 inches tall and are labeled 385/65/x22.5 Super Single 8 plies. Each tire weighed 180 pounds and a complete tire/wheel assembly hit the scales at a whopping 260 pounds! Tire pressure was run at 40 psi, which must have been a savvy guess, since they had no flats or wheel problems in the race.
This was good, since a tire change would have been equivalent to any Olympic-level workout. A jack was built into each side of the semi, just in case.
* Modine radiators (brass, not aluminum) were used. The front ran an electric EFE 24-inch fan for cooling and the rear used an EFE hydraulic drive fan that ran off a remote power steering-type pump.
* Steering chores on the big rig were handled by a Saginaw box from Lee Mfg. of Sun Valley, California. Custom tie-rods and pitman arms were fabricated from hefty chrome-moly tubing.
* To keep dirt out of the powerful engine, Cummins used a heavy-duty element filter from Fleet-guard. Bill Savage reported that not only did the filter do an excellent job keeping the dirt out, it was unaffected by rain and splashing water. He said would not hesitate to use this type of filter on a regular race vehicle.
* That slick-looking cab is fiberglass; molds were taken off the stock steel parts. All that trick work was done by Vec-Pro, a custom 'glass shop in Anaheim, California. The paint job was applied by Bill Bushling, who can be reached through T-Mag.
* Important details: Seats by Mastercraft, lights by PIAA, belts from Simpson, gauges by Auto Meter. That whopping big skidplate up front was fabricated from T-6 aluminum alloy by Bill Savage, as was the wraparound front bumper. The engine electrics are stock Cummins stuff and they worked just fine.
* The all-up, ready-to-race weight of the Cummins race semi was a touch over 9000 pounds. Since a stock Cummins cab weighs 11,500 pounds, it's obvious that Savage managed to save a bunch of weight.
HOW DID IT WORK?
Rather than string you out, we'll tell you up front that the Cummins racing semi retired from the event at the 300-mile mark. They had shock problems due to incorrect valving, which led to harsh forces on the shock mounts and some mount breakage. Shocks were replaced, but the spares were valved wrong, too. After they ran out of shocks, the semi was driven back under its own power to a it and ut on the trailer.
But when it ran, it ran great. Bill, who spent some time behind the wheel during testing, said it was surprisingly quick. Top speed, measured on a dry lake bed, was over 110 miles per hour.
Bill noted that there was so much torque, they never needed to use the bottom two gears. Acceleration, he said, was faster than a good Class 7S truck.
Mike Lund, a long-time veteran driver, was chosen to pilot the big rig, and the plan was to drive quick but not hard. Savage mentioned that the Navistar Global Positioning equipment was astonishing.
All three chase trucks were equipped with GPS, and at any time they could check the following things on the race truck, by glancing at the readouts: miles-per-hour, engine rpm, all engine temperatures, turbo boost pressure, shock temps, rear-end temps, and tranny temperatures.
Bill and the drivers said that the driving position let them see "forever," sitting that high up in the air. The only drawback was that tree branches kept filling up the cab. Oddly enough, a low hanging tree branch wasted the front fan and the engine ran hot for a short while until the fan was replaced. Everyone connected with the project mentioned that the huge truck handled extremely well, and the long travel suspension really handled the bumps.
WAS IT WORTH IT?
Sure. It cost a cool half-million dollars to complete the Cummins racing semi, but Cummins/Navistar are happy with the positive publicity. Even better, they feel that the new M-11 engine is more than capable of handling anything that can be thrown at it.
What's next for the big rig?
Plans are to race it in selected events during 1995. You can bet the crowds will be looking for El Burro Grande, or as the locals called it in Baja, The Big Mule.
COPYRIGHT 1995 McMullen Argus Publishing, Inc