Rayburn Pull Rod vs. Fifth Coil

[catgo22]

Understand how a fifth coil works on a Shaw, Rocket, etc... But don't understand why all Rayburns have a pull rod. Anybody understand why he builds 'em this way. How does it work better in CJ's mind?

Go Blaney

[coletrickle]

its just another tuning tool. Changing angle and rearend location side to side and front to back which all make massive handling changes. Usualy a pull bar will add a little more anti squat which = forward bite.

[billetbirdcage]

It largely has to due with the suspension CJ has chosen for his car, Swing arms/z-link.

A pull bar not only pulls but pushes the rear end forward. If a pull bar was level when it pinioned up and pulled it would also try to shove the rear end straight forward. Since the Rear links make this not happen the force is transfered thru those links to the frame. Since they have angle in them they try to lift the chassis. This is why a rayburn can hike as much or more then a 4-bar car when it has much less bar angle.

You have the force of the rear end trying to excellerater and the car (mass) resisting on all cars (same on rayburn or 4-bar). The car with a pull bar is increasing the force on the LR links and this makes it able to lift the car with less overall bar angle on the LR.

Just say that there is 1000# of force against the bars from excelleration, now both cars have this 1000#. The car with the most LR bar angle will climb the bars easier, faster, and farther then the car with less bar angle.

Lets assume the pull bar is applying another 1000# against the LR bars (a torque arm is lifting on the chassis-no real force pushing rear end forward) the car with the pull bar now has 1000# + 1000# = 2000# against the LR bar so it can can climb the bars with much less angle.

If you removes the pull bar and uses a toque arm on a rayburn they likely won't get up with out mechanically jacking them up or adding bar angle to the LR. Those two items work hand in hand. If you are using a pull-bar with a 4-link LR you will likely be using less bar angle then a 4-link car with a torque arm.

Those are all ficticious numbers just for simplicity. Hope that makes sense.

[racer68]

Using those same force numbers how do the different spring rates for the pull bars affect the drive force ratio? I also assume that the pull bar angle also works like the 4 bar angles driving the force with more leverage into the chassis. Is that correct?

[catgo22]

Thanks Cole & Billet. That really helps. Just bought a used Rayburn... Been eyeballin it for weeks tryin to figure it out. Was about ready to start cuttin on it. Maybe I'll leave it alone. Been driving a 4 bar - liked the roll over and rear steer... Not sure how this swingarm thing will steer, looks like it will push like crazy but we'll give it a go.

[billetbirdcage]

You'll be fine, they just drive differently. You will probably need a little time to get used to the lack of sidebite as compared to a bar car (generally). You may need to us a j-bar instead of the long panhard bar if you can't get the sidebite or lean towards a stiffer RR spring until you get used to it.

These cars on rough or fast momentum tracks are extremely good, you will be fine there but on some smaller stop and go tracks that are slick you will probably need some time to sort it out. You will likely need to learn to trail brake on these type of tracks to help tighten entry.

Good luck.

[coletrickle]

Thanks Cole & Billet. That really helps. Just bought a used Rayburn... Been eyeballin it for weeks tryin to figure it out. Was about ready to start cuttin on it. Maybe I'll leave it alone. Been driving a 4 bar - liked the roll over and rear steer... Not sure how this swingarm thing will steer, looks like it will push like crazy but we'll give it a go.


Are you using this for a crate or a super motor?

[catgo22]

:shock: UMP stuff... SB2. A little over 800. Has the Rayburn Konis on it. Have not driven it yet. Thanks.