New CAT on the block – Schumacher CAT SX
The remainder of the front suspension set-up is quite conventional. Next to the cross-webbed arms you can find the reversed C-hub steering arms, first seen on the LOSI XX-4, that offer a huge steering angle together with more ground clearance of the wishbones compared to the conventional C-hub design. Drive to the wheels is provided by beefy but still light weight spring steel universals that attach to Schumacher’s own Rev-Lite zero off-set wheels. These wheels are a bit different from the usual Associated/JConcepts/LOSI design because of the pin type drive instead of commonly used hex type design the aforementioned use. Thankfully Schumacher supplied a small batch that contains alloy hexes and the needed fixings to convert the front end from pin to hex drive so all of you guys that turn their back on their current rides can use the existing stock of rims. Nice one, Schumacher!
Also found on the front end is a very nice (read: smooth) ball-type differential that is loCATed in two very nice eccentric fixings to adjust the tension of the 3.5mm wide drive belt. Between the belt the twin bellcrank steering set-up finds his home. The steering arms are nicely machined alloy items with dual ball bearings and are connected by a link made out of a small tie-rod and two ball cups. This allows for an adjustable Ackermann effect although the link is not the easiest one to reach.
Middle
The most noticeable changes to the current breed of electric off-road buggies are loCATed in the middle of the chassis. First of all: the CAT SX is a belt driven car. That’s a bit of a sensation since most of the other current cars use a shaft drive. Also a bit of a surprise it the fact that the new Schumacher buggy features three drive belts. That’s not much of a problem since the modern 4,000mAh+ batteries and high-end brushless motors offer more than enough run time and speed to overcome the slight lack of efficiency compared to the very low friction shaft driven cars. The drivetrain of the CAT SX is in fact so well made that even when built from new it spins surprisingly free.
The reason for Schumacher to choose a three belt set-up might be seen in the wish to develop a car that is ‘LiPo ready’ out of the box. When the SX was constructed nearly 100 percent of the commercially available LiPo batteries where of a stick pack layout making it necessary for Schumacher to develop a chassis that allows the use of a 140mm long battery pack. To avoid a very wide chassis the middle drive belt is now mounted in quite a high position with the battery pack underneath it. The result is a reasonably narrow chassis plate with a unique belt set-up above it.
As unique as the drivetrain set-up is, you may find the way the motor is mounted to the chassis equally interesting. It’s a real testament to Schumacher’s implacable will to produce uncompromising race cars. Different from other designs the motor is clamped in a P-shaped alloy part secured by a single 4mm screw. This P-shaped part is then attached to the two bulkhead plates via 3mm screws and another 4mm screw. The motor mount then is sandwiched in some soft of rail by the 2.5mm thick upper and lower chassis plates. This may sound complex and in fact it is but built with accuracy and the help of some quality threadlock we have yet to experience any issue with it.
A little bit further to the rear of the chassis another feature of the CAT SX can be found: the second layshaft. Huh? Second layshaft? Why is that? Before the drive of the motor is transferred via the slipper clutch to the belts its direction is altered. You may notice this because of the ‘wrong’ way the motor is mounted in the chassis. Normally with diagonally mounted motors the motor shaft points to the right side of the chassis. Not so with the SX. The motor is turned 180° and as a result the spur gear is turned the wrong way. It actually rotates in the wrong direction. But why the hack? It basically has something to do with the way rotating masses affect the way things behave. When it comes to off-road buggies, and off-road vehicles that jump in general, the rotating mass of the wheels and the rotating rotors of electric motors affect the way the buggy flies. Experienced off-road drivers know that you can adjust the angle of the car in the air by stepping on the gas (raise the front of the car) or brake (ramming the nose of the buggy into the ground). ‘Old school’ belt driven buggies had the problem that the motors turns in the opposite direction to the wheels resulting in something like a confrontation of the two rotating masses (wheels and rotor). With the set-up the CAT SX sports both wheels and rotor rotating in the same direction resulting in a better controllable car while jumping. This is the theory. Will it stand the test?
