Inside Serpent's new 4WD prototype, the SRX-4

0 Jan. 25, 2015, 7:09 a.m.

1/25/2015
By Aaron Waldron

LiveRC.com

While the Invitational class is certainly the main event of the Reedy Race of Champions, the undercard isn’t bad, either - the Open 2WD and 4WD classes feature the fastest up-and-coming racers in the world as well as those factory drivers who haven’t yet earned their invitation to the big show. This year was no exception, with notable drivers from all over taking the top eight spots guaranteed into both finals.

For many years, the Serpent brand of cars encompassed only nitro on-road racing, and for good reason - that’s all they made. Not only has the dutch brand been at the forefront of 1:8 nitro on-road since the company began developing cars in the late 1970s, but Serpent can be credited with helping to create the 1:10 235mm and 200mm nitro touring car divisions as well. Serpent first began testing the waters of the off-road segment in the mid-2000s with cars designed by Gerd Strenge, who eventually produced his creations under the Team Durango name. Later in the decade, 2003 2WD IFMAR World Champion Billy Easton joined Serpent as a designer and helped put into production Serpent’s first 1:8 nitro and electric off-road vehicles, then moved into 1:10 electric off-road with the SRX line that now includes rear- and mid-motor 2WD buggies, and a 2WD short course truck.

Amid rumors last year that the car was coming, Serpent recently announced the SRX-4 4WD buggy ahead of Easton making its international debut at the Reedy Race. Easton said that he finished the car’s design around July of last year and started receiving samples in October and November. He was able to begin testing in earnest just before the start of the year, and both Easton and Serpent America CEO Joaquin de Soto suggested the car could be released to the public as early as March.

First and foremost, Easton said his objectives were to create a car that is balanced and generates grip at both ends. Billy felt that today’s current cars often lack rear grip, which means that they must be set up to reduce steering accordingly, and that a car with more traction can be set up more aggressively. It was also a prime concern that the car be balanced, and that required laying out the car with near-perfect symmetry as it’s difficult to offset heavy components like the motor and batteries - even when using ballast to achieve left-right balance, that often throws off the front-rear balance and you end up with a car that is more weighted on opposite corners.

Achieving that symmetry was difficult, especially when trying to fit the motor into the center of the chassis. Easton found the answer by using a short belt to reach the gear differential and then building a transmission to offer the proper gear reduction to get the front drive ratio to match. Once Billy figured out that design, he said the rest was pretty easy - he wanted to use 3mm belts for a durable, low-maintenance drivetrain, and has been running the same belt for three months. Because of the gear ratios used to drive the front end, the front belt doesn’t have to spin as fast - and that means longer belt life.

When it came time to configure the suspension, Billy looked at other cars to see the direction of today’s current 4-wheelers. He designed a new front spindle design with a different offset to help the SRX-4 achieve the feel and stability of a 2WD, but still maintain the aggressive cornering behavior of a 4WD buggy. The balance of the chassis means that the car reacts similarly when turning in both directions, and it flies flat through the air as well. Knowing that the SRX-4 would be competing on both dirt tracks in the U.S. as well as carpet and astroturf tracks everywhere else, Easton said it was imperative that the car have the adjustability options to be able to cope with either condition. In particular, he needed to make sure the roll centers and diff heights were right. In addition to his running test car in the U.S., two of Serpent’s drivers in Europe have been running the car as well.

Billy will be the first to admit that he doesn’t get to practice and run as much as he’d like, so his performance in his return to the Reedy Race of Champions after over a decade doesn’t showcase what the car is truly capable of doing on the track. But the World Champ says he is happy with how the project has turned out, and is excited to see what the world thinks when it hits the track.