Driver Training Skid Truck
In this project for Fleet Safety International, we added
rear wheel steering to a pickup truck to create a vehicle
that can simulate slippery road conditions.
This project is really a series of vehicles that we converted for FSI (Fleet Safety International that was formerly Alberta Collision Avoidance), a driver training school. The idea was brought to us by Joan and Randy Flemmer. They wanted a vehicle that could simulate a rear wheel slide. There were other vehicles that could actually skid but they were mainly for racing schools and worked at high speed. The Flemmer's wanted a car that was safe for the average driver; meaning that it had to work at low speed and be controllable by the instructor, not the driver.
Their concept was to make the rear wheels steer, causing the back end traverse sideways while the vehicle is moveing forward. The Dodge Colt, pictured above, is the first vehicle we converted for them in 1990. It is a front wheel drive, so adding steering to the solid rear axle was relatively simple. The steering actuation was done hydraulically with electric solenoid controls. The instructor in the passenger seat controls the switch that steers the rear wheels left and right. When the wheels are turned, the back end drifts out like a skid and the driver must counter-steer to keep the car "crabbing" forward. When the student reacts, the instructor steers the other way forcing the driver to countersteer the other way. The car basically fish-tales as it goes down the road.
The momentum generated by the side swinging is quite hard on the vehicle. These vehicle are down right dangerous if the speeds get too high. We custom designed a speed govenor to keep speeds below 20 km/hr. The wear and tear on tires and even the chassis is quite high even at the reduced speeds. In fact, the first Colt was worn out after a number of years. The Flemmer's managed to find an identical car and we transferred the system over. The second car is still in operation but it is getting quite worn out.
The Skid Car was a success. It was a niche product that gave FSI a competive advantage that none of their competition could offer. They decided to build a second vehicle which is the pick up truck shown to the left. We knew from the wear and tear on the Colt that a stronger more durable vehicle would be desirable. The pickup was a natural fit as most of their customers for the skid training were driving fleet pickup trucks for their companies who were paying for the courses.
The pickup trucks worked out a bit nicer: there was more room to work; it turned out to be more durable; and the longer wheel base made it feel more like a real skid. Because the truck was rear wheel drive the conversion was complicated somewhat as a steering differential was required. The instructor in the passenger seat still controlled the rear steering in a similar manner as the car.
We redesigned the governor as we were not really happy with the reliability of the one used in the car. After a bit of head scratching, we decided to modify the factory, electronic, cruise control module. We opened up the module to find an 8-bit Intel processor reading various sensors like brake pedal switches etc. and driving a stepper motor to control the pull on the throttle. All of the mechanisms and most of the sensors we needed were already there; we just need new logic.
The factory printed circuit board and processor, which had it's program hard coded into ROM, we discarded. A board custom designed by Zanthic Technologies that had a Motorola chip and flash (reprogrammable) memory was put in it's place. We installed an electronic foot pedal (a gas pedal with a sensor) to signal our control, basically creating a drive-by-wire setup.
The program, or firmware, was develped and tested at Qsine. By having software control of the gas pedal, we can do things like limit the throttle opening while the vehicle is moving to prevent over-shooting the 20 km/hr limit all while letting the throttle open a lot when the speed is very low so the engine can produce enough torque to get up the trailer ramps.
The first pickup performed admirably. Since that time we have converted two more GM puckups; both 4x4's. Even though we could have made the trucks front wheel drive by locking in the transfer case, we decided to use a steering differential anyway. The Flemmer's like the feel of rear wheel drive during training and 4 wheel drive was handy for loading the trucks on to trailers in the winter. Which brings up a good point: these vehicles are not street legal.
A few more interesting photos: