How To Fly A Short-Course Truck 175 FeetPosted in Features on December 19, 2013 Comment (0)
Frequent flier Rob Mac on one of his many flights across
a LOORRS short-course track.
Author: Craig Perronne Photos: Bink Designs
Sailing a 4,000 lb., 900 horsepower truck close to 200 feet is no simple task and definitely not one for the timid. To find out what exactly happens out on the racetrack and inside the cockpit when flying off one of these monsters, we turned to one of the sport’s most talented drivers, Rob MacCachren, to give us an idea of what it is like. Remember kids, do not try this at home! Rob Mac is a trained professional and unless you want to blow apart your truck along with your spine, we suggest you leave the major airtime to the pros.
Dirt Sports: How high and how far can you actually fly a short-course truck?
Rob MacCachren: The jump that we probably fly the farthest on in either series is at Bark River, and we fly anywhere from 175 to 200 feet there. It’s a rolling hill that was already in existence and they have tuned it over the years to make a nice ramp. As you come toward it, you come through a little chicane but you are able to go through that at a fairly high rate of speed. I would say it is probably in the 80 mph range that we are approaching it and it is a blind jump that you can’t see over. At Bark River at the end of the first day of practice we used to have a jump contest. In the late ’90s I won one of the jump contests and I flew 185 feet. I know we are flying from 175 to 200 feet because I witnessed people flying farther than I did. DS: What can you do to affect the truck while it is in the air?
RM: When you are approaching a jump, depending on how abrupt it is or how much of a ramp there is, we can manipulate the takeoff. If you are at wide open throttle when you leave the lip of the jump, typically that will make the nose of the truck fly higher because the rear wheels are driving and lifting the truck. We can manipulate it by slightly lifting right before you leave the ramp to make the nose fly lower. You have to be cautious on how much you do that or you could land bumper first. Also, once the truck is in the air you can set the nose down by using the brakes like they do in Supercross. They tap the rear brakes and the nose comes down and we can do the same thing. Some of these jumps make you fly nose high so you either roll out of it when you leave the lip or push the brake pedal to drop the nose. It is an amazing thing because you would think these trucks are too heavy to do it but it does work. At every Lucas track there is at least one jump I am hitting the brakes mid-air on. It also enables you to take a jump at full throttle so you don’t have to lift.
DS: How does it feel as a driver when you land from one of these big jumps? Is it a big impact?
RM: We really don’t like flat landings as they hurt more than a ramp landing. Landing on the rear tires first hurts too. When you land on the rear tires and then slap the nose down, that hurts twice. When it is really bad, you land on the rear bumper and then slap the front of the truck down. That doesn’t feel good at all either. Flat landings are just terrible. You want to land like a soft landing in an airplane. The greater the speed and the less angle you have when you hit the ground, the better it is. For me personally, I like the front tires hitting the ground first by a short amount. That is the best feel, and you are in control of the truck quicker. You can turn the truck or hit the brakes or whatever it may be. I like nose-down, front tires first, but not too much of an angle because if the ass end gets too high you can endo and catch the front of the bumper. Every jump is different at every track. Lake Elsinore is probably the most extreme jumps we have, and the ones I dislike the most. The one coming out of Turn 2 is the worst one. The landing is not quite flat but almost. DS: For a track with really big jumps do you set up the truck differently?
RM: You can two do things and either add compression or spring to help the truck. More of what we are doing with spring rate is to keep the truck from g-loading from the weight of the truck being forced down as it goes up the ramp of the jump, which bottoms the truck out. You have seen pictures where the truck is actually scooping the dirt from between the front of the A-arms. We visually see it more in a desert vehicle when a truck shoots a ton of dirt out in front of it, but it does happen in short-course. We really don’t like that either, so you do work with your spring rate and valving. Lake Elsinore is one of those places we do that to take care of not only the landing, but the takeoff. DS: Does a Pro 4 jump any differently than a Pro 2 or is it all the same?
RM: My Pro 4 jumps and lands better mainly just because it is set up differently. The Pro 4 doesn’t fly as nose-high as the Pro 2 because all four wheels are driving. Like I was saying before, in a Pro 2 when you take off a ramp full throttle, it is trying to do a wheelie. In the Pro 4 it isn’t doing that because all the wheels are pulling. The Pro 2 has more reaction to the jumps than the Pro 4. DS: What can you do to avoid hitting people in mid-air?
RM: Vegas is one of those tracks where you come out of Turn One and you are still sliding as you are coming to face the ramp of that big tabletop. You hope nobody touches each other or you and that you get the truck straight. The first thing that is bad is when you touch going up the face of the ramp and the truck is not going the proper direction when it leaves the ground. The next worse thing is when two trucks touch in the air. When you are around people, you are always trying to stay clear and go off ramps straight and make sure you don’t hit anybody or anybody hits you. Once the direction of the truck changes, it is usually not good. You hope the guys next to you have respect for you and that you have respect for them and the heat of the moment doesn’t get to anybody. Typically it does though. The higher you are in the air, the longer you are going to fly and the more time the truck has to change angle. If you are lower to the ground, it is not that bad.
DS: Are there bigger jumps in the desert in short-course racing?
RM: Definitely short-course. Desert is more of an endurance race and because the race is hours long instead of minutes it is not that important to hit a jump hard. Typically in a desert race we are being a lot more conservative and trying to save the car and not hurt it. In short-course racing you always want to take that jump one foot farther than the guy next to you. That is when all hell breaks lose. If he hits it at 100 mph, I want to hit at 102! In desert racing that doesn’t happen.