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Discussion Starter · #1 · (Edited)
It was mentioned that many times we don't know exactly what is meant by a certain term. This made me think that a "Terminology" thread would really be helpful. I think we all hear something that sometimes may not register. I'm going to throw some up here and hope that all of us can contribute. Please don't hesitate to ask and don't feel like any question is a dumb question. The only dumb question is the question unasked. Please, everyone and anyone. Chime in and add to or correct anything that may be incorrect. Correctness is what we want.

Straight axle:
In the early years many racers were running with stock suspensions. I don't have all of the explanations but many were that the tires of the day were not the best for traction. Some, not all, gasser class cars needed more traction so they modified their front ends to lift them to throw more weight transfer to the rear, therefore, gaining more traction with the same tires. Many stock suspensions either did not have the travel to get the front up enough, or became very unstable lifted up that far. Plus the front suspensions were very heavy. The racers found that the rules allowed for modified suspensions so they would take the old beam front axles off of the early Fords etc and graft them onto their cars, cutting the old heavy suspension completely off. Some inventive people would build a completely custom straight "tube" axle using the original spindles but using metal tubing for the axle. This allowed for custom widths, custom components, custom placement etc. Thus the term "straight axle" was born. Many use the term to describe front axles other than "straight" axles like the early dropped beam axle etc. There are also several iterations of suspension with "straight axles" as well. Dual parallel springs, an over the axle single spring like the old buggy spring, and coil over shock front springs are a few.

Drag Link: The drag link is the bar or "link" that goes from the steering box to front suspension item such as the spindle to steer the car.
(Note) I was always taught that the term "Drag Link" was only describing a link from a rear (behind the front axle) mounted steering box where the link went forward to a "same side" front spindle. But I think many use the term to describe any link between a steering box and the spindle. But I'm not absolutely sure of that as you may hear it used for more configurations. (I'll explain more in the cross steer explanation).

Tie rod: This is the bar that "ties" the spindles together from side to side so they work in unison.

Hairpins:
When a front straight or beam axle is installed with a single "buggy" spring or coil over shocks, the axle needs some kind of solid link to the frame to keep it in place. This Link generally runs from the outside end of the axle back to the frame. The spring will locate it side to side. The Hairpins locate it for and aft. When using coil over shocks, they will not accurately locate the axle side to side so you generally need a "lateral" or side to side link also. These are usually known as a Panhard bar. When using full dual parallel springs to locate and hold the axle, they are stiff enough to do all of the locating, for and aft as well as side to side.

Panhard Bar:
As mentioned above, this is a side to side locater bar used on suspensions to locate axles (both front and back) and hold them from moving side to side. Even late model cars use them and they work really well and are very simple. The only down side is the length of the bar and the amount of travel.
The bar is normally a straight length of tubing or stamped metal that pivots at it's mounting points on each end. One end is frame mounted (or to mounts to the frame) and the other is mounted to the rear housing or the front axle. The problem with this is, as the frame and axle moves opposed to each other, the ends of the bar has to pivot in opposite directions and the bar then moves in an arc, which effectively shortens the bar. This arc has to move one end or the other to affect that arc. The shorter the bar the more the affect. The axle (front or rear) then moves in a side to side motion as it moves through it's travel because of the that arc. The longer the bar, the less of an affect. The shorter the bar the more the affect. Or. The longer the travel for a given bar length, the more the effect. Generally the longer the bar that you can make/install, the better off you are. I hope that all makes sense.

Ackerman Affect:
This is the term for the front tires as they go thru their arcs in a turning situation. As the front end of a car/truck turns thru a curve, the outside and the inside tires/wheels roll in different arcs due to the distance of one tire to other tire. This is critical on any custom suspension as it creates a different roll path. The inside (of the turn) tire must cut a smaller arc than the outside tire for both tires to work together instead of fighting each other. If they do not have this differentiation, one tire will be forces to "scrub" or slide to make up the difference. If you see a custom built front suspension car turn a corner and you can hear the front tire or tires squeal, then chances are they do not have any or the wrong Ackerman setting.

Cross steer: This is a steering configuration where the steering box is located on one frame rail or side but the action is extended across the car to the opposite frame side. The cross steer link (or drag link) attaches to the steering box on one side of the car and then it connects to the spindle on the opposite side. Hence the "cross steer" term.
As the description in the "Panhard" section explains the arc travel of the bar, it is the same for a drag link or cross steer bar. The difference here is, the arc of steering link affects the reaction of the steering, causing the front to steer in accordance to the arc. This is called "bump steer". The cross steer link is generally much longer and has much less affect on bump steer.
(Note). The closer you can get the mounting point of the steering box and the end point (spindle or?) on the same plain, the less affect of bump steer will be produced.

OK, I think I've probably done more harm than good here. But it is a start. Please correct and or add any more terms to this thread.

Mark L
 

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Great post and great start Mark, and very informative!
I would add that the term "buggy spring" is referred to as a "transverse spring" or "cross spring".
Another often used term in straight axles is "king pin inclination". This refers to the angle the king pin tilts, and that angle is always back on thee top of the kingpin as you're looking at the car from the side. King pin angle can vary from a few degrees to as much as 22 degrees. (on rails) It is generally accepted that 5-7 degrees inclination is best for most straight axle vehicles.
Toe in is another often discussed term on all sorts of front suspensions, but for our purposes (straight axles) it's adjusted based on old manufacturer's specs. The factory specs are still viable, and used for most street/strip cars; which is 1/8"-1/4" toe in. Which basically means if you measure the distance between a specific point horizontally from front tire to front tire, both front and back, that measurement will be 1/8" to 1/4" narrower in front than it is in the rear of that tire.
And another term! "Pitman arm", which refers to the arm attached to the steering box, and the drag link attaches to it to steer the car. Most pitman arms are "indexed" which means they have a notch or keyway to ensure the arms go on in the same location as referenced to the steering box shaft. Some aftermarket pitman arms come without a notch to allow infinite indexing.
 

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Kind of hard to read, but this simple picture I took out of the speedway catalog helped immensely!

 

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Discussion Starter · #4 ·
Great additional info guys. Mark L
 
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