I am putting a 9" in a Model A with a 32 frame, I am running a 40 Ford front transverse speing in the rear setup. I have a set of ladder bars that angle towards the tailshaft and pivot relativily close to the front driveshaft u-joint. Do I need a panhard bar and if so how long?
Can you provide a pic? Depends on how acute the angle on the ladder bars are, if you do put in a panhard bar the longer the better. Doc.
I don't think the angle of the ladder bars has as much to do with needing a panhard bar as does the length of the shackles attaching the spring to the axle. That is where rear end side movement will occur. Actually, you have little to lose and possibly something to gain by using a panhard bar if you have the space for one. As for length, DocWatson is correct that it should be as long as possible to minimize the 'arc' it subscribes and therefore to minimize side movement. The better choice than panhard bars is a Watts Link which keeps an axle (or anything using it) from any lateral movement. However, the Watts Link generally takes up more space. Ray
As Hnstray says, a Watts linkage is superior to a Panhard bar. Alfa Romeo used them on their De Dion rear end in the 1970s through 1990s....
With that style spring your rarely need a panhard, if ever. As mentioned, if you are not running overly long shackles the spring itself acts as a movement limiter. I've never run one and have no side to side movement to speak of. Don
What will make the difference between needing a panhard or not on that setup is the shackle angle, or preload on the rear spring. If the shackles are at least a 45* angle with proper preload, you won't have a thing to worry about. If they're hanging down closer to vertical, it's gonna sway around a bit.
1909-1941 Ford springs mounted correctly under tension as the factory designed them do not need Panhard bars.
That's an unusual elaboration of the Watts linkage principle: are the arms geared together? It's almost half-way towards a Mumford link. Here's what an Alfa Romeo Watts linkage looks like:
Over the past 30 years we have built 100s of buggy rears using a 40 style spring with ladder bars and have yet to use a panard!
Originally Posted by pasadenahotrod 1909-1941 Ford springs mounted correctly under tension as the factory designed them do not need Panhard bars. X3
Might as well go X4! As long as you pay attention to what Thunderbirdesqe was talking about above with the shackles at 45 degrees.
You don't need one......for all the reasons listed above. The car will drive fine without it and you will rack up many happy miles. Me personally,I wouldn't build one without it. Something about using springs to locate something doesn't seem real positive to me. You got one in the front?
I have a similar setup under my '41 pickup. Started with no panhard, and had some lateral motion that rubbed the tire against the bed. Panhard bar immediately solved the problem. No noticeable change in ride or handling. Had (still have) pretty big tires on the back, which of course contributes to the problem. Your results may vary.
Where trouble can come in is with spring sag, which effectively lengthens the span of the spring. If that goes too far shackles will be at close to vertical at rest and car can sway. Rearching or replacing spring seems easier than adding a component. Also, look at a '46-8 Ford...they went to longer nearly vertical shackles, eliminating that tension, and added anti sway bars at both ends for control. Those would provide some parts and design suggestions if your spring is saggy and you choose the panhard route. (edit...one problem on a car that is being built is that you probably cannot fully predict how spring and shackles are going to hang til the car ereaches full weight and is on its wheels)
Hers one that was done 50 years ago and its wrong no need for it its binds the spring and the mounting brackets for spring are limiting the spring travel. I am going to fix it over the winter
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