Quote:

I am thinking I could put a bracket on the top of the axle and install the front part of the caltrac pionting up rather thab down. Now hidden, but won't put anything on until I understand why I am doing it. Thanks again



You absolutely could do this. The problem that you have, is that it puts the threads of the heim joint in tension instead of compression, which is much more likely to fail then the other way around. I thought about doing the same thing to help "hide them".

As for your question on caltracs creating more "pressure" on the tire. While there is no special geometry about them that makes more "pressure" on the tire from a static evaluation (links/torques/etc...) the part your missing is what happens in the DYNAMIC tire event.

When the car launches the pinion tries to climb the ring gear. One of three things happens.

1) The axle rotates up (car doesn't move).
2) The axle stays still and the tires spin without forward car movement.
3) The axle stays still and the car moves forward (traction).

In reality all three of these things can/do happen similtaniously. However during the initial "hit" the majority of the movement is #1 above. This is mainly because the force to rotate the pinion is less then any forces required to overcome the intertia of the body/tire.

What happens is that when the axle rotates up, there is a vertical force translated through the front spring segment to the front spring eye.

If you remember from high school science class, every action has an equal and opposite reaction. In this case, when the spring tries to pick up the body through the front spring eye, the opposite "Force" doing that is pressure on the tire. You can imagine this even in a static environment, if you put the jack under your tire, whatever force you apply to the tire, is translated to the front spring eye.

This all happens VERY quickly. Because shortly after the "hit" the torque of the tire start to overcome the inertia of the car to move it forward. So there is a very small window between "hit" and forward movement.

That all being said, what the caltrac does is allow the front segment to become very stiff almost immediately. If the front segment is soft, during the time period of tire "hit", all of the energy from the pinion rotation will simply be used to bend the spring (no additional force on the tire). However if the front spring segment is "stiff", then it allows the energy to transfer immediately to the front spring eye. When it tries to quickly accelerate the body upwards, the inertia from the car resists the movement. The result is that the sidewall of the tire "looses" the force battle, and the tire gets planted into the ground HARD.

Once you have the tire planted, it is less likely to spin because you now have more traction. More traction means that you can accelerate the car forward sooner/quicker.

Make sense?