The car we use the most is the Xray M18. In the past we've also used the HPI Micro RS4. These are 1:18th scale on-road cars. We use these cars because they are small enough to race on our intricate indoor track, yet they have most of the technology and drivability of larger RC cars.
The cars have accurate proportional steering, proportional electronic speed controls, independent suspension, front and rear differentials, adjustable alignments (toe and caster), adjustable suspension, and high end radio systems. All that technology is packed into cars that are only 4 inches wide!
The performance of the cars depends on the types of batteries and motors that are used. They can be made to go up to 60mph or more. However, our interest in the cars is more to do with their ability to drive on our tight, curvy, low-traction road course, and in "bringing realistic racing action to small-scale RC." With the batteries and motors that we use, they have a scale top speed of over 200 mph - similar to the actual speed of full-scale race cars. The cars can cover Harnois Race Park's 25-foot straight in less than 2 seconds. On our super tight track with 12 turns, they can do a lap in 12-seconds! One nice benefit of the batteries and motors that we use is a runtime of well over one hour!
The Xray M18 is designed to use sports car type bodies that cover the wheels. We wanted to create open-wheel cars using the very high quality Xray M18 chassis. The reason for going with an open-wheel configuration is because, just as with full-scale open-wheel cars, the wheels get caught up on each other causing the cars to flip and fly in fun and realistic looking crashes. The impact bahavior is a lot more realistic and interesting than sports car bodies. Also, drivers are encouraged to drive with more control since impacts with walls and other cars have more potential to knock them out of the race. The cars are also effectively smaller which is helpful on our tight track. Plus with all the replica vehicles out there, it was fun to create our own unique style of race car.
In this 2nd generation of open-wheel Formula Harnois cars, we used the JConcepts Mini BJ4 Illuzion Body over the Xray M18 Chassis. This body is actually designed for 1/18th scale off-road vehicles.
The new cars also utilize CNC machined carbon fiber leaf springs in place of the stock coil springs and shock assemblies. We designed these springs ourselves. They practically eliminate all of the friction in the suspension and steering. Less steering friction means the car tracks straighter on the straightaway. Less suspension friction means the car "floats" along the floor with super smooth handling. It's suspension that actually "suspends" the car like it should, so the suspension can constantly adjust with no stiction so all 4 tires maintain consistent pressure against the racing surface.
We also fabricated motor mounts from aluminum. They attached to the rear gear box rather that to the chassis. These allow us to mount the motor over the center, without having the mount in the way of the battery placement. The gear mesh can be adjusted by sound with a screw while the motor is turning, for perfectly smooth adjustment.
When we first came up with the idea of using 1/18th scale off-road bodies to create an open-wheel car, we used the Parma 1/18th X-Citer body. We adapted both the Xray M18 and HPI Micro RS4 to accommodate this body. This required considerable modifications to the chassis, and fitting all the electronics and mechanical parts under the body was challenging.
Use the links below to access the photo album of these cars.