Short Course for the Road Course
There are some definite advantages to living in Southern California; one of the biggies being the weather. Because it rarely ever changes from 70 degrees and sunny, there are times I like to get away from the hardcore, purpose built indoor tracks for a nice, relaxing day in the sun. My buddy Charlie runs a few parking lot races and one of the classes he offers is the gearbox class; basically any offroad vehicle with an enclosed transmission. To make things a little more exciting, skateboard jumps are set up around the track for a little airtime. Lately I’ve been noticing quite a few Short Course trucks appearing and tearing up the track. It looks like a lot of fun…enough that I had to build one of my own.
Chassis & Suspension
I started off my project with a spare Team Associated SC10 I had in my garage. The chassis, shock towers, transmission and drivetrain parts were all kept stock. Since I’d be jumping and landing on the unforgiving asphalt, I decided to swap out the suspension arms with a set of RPM units. These suspension arms use a unique way of capturing the hinge pin by using an inline screw. Say goodbye to those miniscule 2-56 capture screws! The rear hub carriers have been swapped out with a pair of Racer’s Edge 1 degree hubs. This added rear toe will help the SC10 dive into the corners a little bit while still keeping it stable on the straight. For the dampers, I added 9mm of limiters to the inside of the front shocks and 12mm in the back. This helps control any drastic chassis movements during acceleration or under hard braking. The front shocks were filled with 70wt oil and red springs; the rears with 60wt oil and green springs. Ride height was set with front arms level and rear arms slightly below level. If your track does not have jumps, you can lower the truck down a little more. Keep an eye out that the body does not come in contact with the tires under compression.
The gearbox class does not have any limitations on electronics; it’s a run-what-ya-brung type of deal. I chose to keep it somewhat ‘mild’ and installed LRP’s SXX ESC and Vector X-12 10.5 Brushless motor. A Reedy 40C 5000mAh LiPo pack delivers the juice through my custom red wiring. This silky-smooth combo provides some pretty knarly speeds that provided a few spectacular wheelies on more than one occasion! To keep it all under control (the best I could!), I chose Spektrum’s DX3R. This 2.4GHz system has a ton of controls right at your fingertips and one of the easiest menus to navigate.
Body, Wheels & Tires
Digging around in my garage, I found quite a few bodies to choose from. I opted to go with the Proline F-150 Raptor because of its sleek, aerodynamic design. For the rollers, I chose Proline’s Pro-Core Street Fighters. These tires do not require any inserts; the ‘insert’ is molded into the tire in the form of ribs. These are a revolutionary product in that there is no chance of unstable handing due to your insert deteriorating away. These long-wear kicks are wrapped around a set of Proline’s Split Six wheels with color-matched bead-lock ring. These are true bead-locks…no glue required! This combo seems a bit heavy (with the cored tires, metal bead-locks and pinch screws), but since there wasn’t a limit on power, I wasn’t too concerned about it.
I set the truck down and did a couple full-throttle romps to check the slipper clutch. Once adjusted, I set the body on and prepared for the run. For most people, there is always a little hesitation when running an offroad car on an onroad track. I took the first two corners a little slow to get the feeling for the truck, but wick’ed it up for the rest of the run! Acceleration was pretty amazing, lifting the front wheels just barely before the slipper kicked in. Steering was good, too, and you could hear the Pro-Core Street Fighters squeal a bit through the corners. While still evident, the think oil and shock limiters greatly reduced the body roll in the corners. The heavily-damped suspension also worked pretty well over the jumps but was a little bouncy on the landing. The only changes I would make to the setup include a one-step softer oil all around and perhaps anti-roll bars.
This was a fun project to do. The SC10 handled surprisingly well for a quick conversion but still needs a little tweaking to get it just right. Along with the other classes I normally run, I will be including this as my ‘fun-run-what-ya-brung’ vehicle.
SC10 RTR, #7031
XP DS1015 Servo, 29167
SC10 Front A-Arms, 70765
SC10 Rear A-Arms, 70745
Street Fighter Pro-Core Tires, 1167-00
Split Six Bead-Loc Front Wheels, 2716-04
Split Six Bead-Loc Rear Wheels, 2717-04
Ford F-150 SVT Raptor Body, 3344-00
SXX Competition Speed Control, LRP80900
Vector X-12 10.5 Turn Stock Spec Motor, LRP50832
LiPo 5000mAh 7.4v 40C+, 685
[as seen in: RC Driver Magazine]