Hyper Racing's brand new Jacob's Jacker ® (patent pending) is a system that allows the remote adjustment of the Jacob Ladder's roll center while you are in the cock pit on the race track.
This unique adjuster moves the rod end that the Jacob's ladder bolts to up 1/2" or down 3/4" from center. That is 1-1/4" of adjustment!
We have tested this unit on the track and adjustments can be made very easily under yellow at anytime, or under green while racing down the straight.
The system is designed to use a CSI shock cable, but other companies cables may be used by using an adapter pin.
A 7/16" shaft rod end with a 3/8" bolt hole. Our part number is 71-PMX6-7. The larger shaft will add extra strength to help keep the rod end from bending in an accident.
Fits Z-link style rear configuration. Pace, Ten-J, PMP, D1, CS9, XXX, Farrell Chassis, and many other manufactures use this design.
Features dual mounting position 4 1/2", 5" and 5-1/2" spread. The 5-1/2" spread is 2-3/4" from center of rear axle, up and down. This is pretty standard in the industry.
Being able to adjust the roll center while on the race track will help solve the biggest problem of dirt track racing, the ever changing track conditions. The rear roll center height controls how much weight is transferred to the right rear during a corner. It doesn't change how much total weight is transferred, just where it transfers to. By lowering the rear roll center, more weight will transfer to the right front (from the left front) and less to the right rear (off the left rear). This keeps more weight on the left rear resulting in more equally loaded rear tires creating more rear traction. If this explanation of how to achieve more rear traction sounds strange to you, please read Mike's Rethink Dirt Paper.
We recommend the bearings be greased before the first use with Champion Grease 74-332, or 77-805 Daylube Nanoceramic racing grease.
What changes do moving the upper and lower mounting points on the bearing carrier have? Glad you asked:
On a Z-link car, it is actually pretty complicated and not real straight forward on what those different mounting points do to the car handling. But here are some general concepts.
When you lower the top link on the bearing carrier and leave the point on the car the same, the chassis will have more anti-squat. More Anti-squat will generate more weight transfer from the front to back under acceleration because the chassis center of gravity height will be higher as the anti-squat geometry will resist the rear squat of the car.
The lower hole when you move it up will make the rear torsion arm angle less which will generally make the effective spring rate less which usually make the car tighter if done on the right, and looser if done on the left.
So those are fairly easy and straight forward, the harder part to figure out is the rear steer effects of these changes. Rear steer is how the axle moves forward and back as the rear axle moves up and down. As the right side of the axle is steered forward the car will get tighter as it will point the front of the car toward the outside wall! Changing the mounting points on the bearing carrier will change when and how much the rear of the car is steered. And you have to consider the left and the right side and how it is steering car at any particular roll angle. This is hard to figure out when and how much the car is rolling especially with the wing on. The car will roll left on entry then roll right on exit. How much and exactly when depends on the size, shape and conditions of the track. Also the ride heights you are running (how high you block the car) will change these transition points as well. Take the stops off you bars with the car on stands and move the rear axle up and down and you will see exactly what I am talking about.
When you lower the top link on the right rear, the right rear rear will move back more as the car rolls right making the car looser when rolled right. Moving the bottom arm closer to the center of the axle (up) will make the right rear steer forward more making the car tighter. The affects are the exact opposite on the left rear as far as tight and loose go.