41 springs shackle bushing

[Chuck41]

New springs today!

Are these things supposed to rotate in the eye so that the spring steel is the wearing surface? I can press them in there but they won't be rotating. I would have to slightly ream out the eye.

[aussie merc]

NO the outer is not supose to rotate but you do need to get the orientation of the square section correct for the shackle plate when its sitting on the ground

[Kube]

Originally Posted by Chuck41

New springs today!

Are these things supposed to rotate in the eye so that the spring steel is the wearing surface? I can press them in there but they won't be rotating. I would have to slightly ream out the eye.

It seems too many folks, lacking the necessary knowledge, grind the shells of these down to make the installation easier. The issue with that? It defeats the purpose of replacing them.
These are designed to be a press fit. In other words, the outer diameter of this pin is larger than the inside diameter of the perch.
If the pins are fit loosely, they will not force the spring to rebound as was engineered / designed.

[Chuck41]

So it's the inner part that rotates as the spring moves? It does seem to have just a little give. Any tips on how to properly orient the square section when I press the pin into the eye?

[Kube]

Originally Posted by Chuck41

So it's the inner part that rotates as the spring moves? It does seem to have just a little give. Any tips on how to properly orient the square section when I press the pin into the eye?

The inner part "gives" but should not rotate. These pins, when installed properly, offer an engineered amount of torsional twist. That is, they "give" a little when the spring flexes but rebound to return the spring back in to it's designed placement.
If they no longer offer that torsional twist (IE: worn out) then the spring will simply "bounce". Perhaps a decent example of this would be worn out shock absorbers.

I would not be overly concerned with getting the squared end of these perfectly aligned when installing. As you'd noted, the center "gives" a bit and as such, once you have the spring spread out far enough to engage the shackle bar, you can place a wrench on the opposite side of the pin and rotate it a bit to engage the bar. Once one bar is installed, the pin can't rotate and as such, the opposite bar can then easily be installed.

[Kube]

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Chuck, just thought I'd add... the authentic pins were a nominal .003" oversize. I have seen poor quality repops at .006" oversize. If you have over .003", you may want to chuck the pin(s) in a lathe and sand down the shell just a bit.
I'd keep them at .752" - .753".

[40larry]

Originally Posted by Kube

Chuck, just thought I'd add... the authentic pins were a nominal .003" oversize. I have seen poor quality repops at .006" oversize. If you have over .003", you may want to chuck the pin(s) in a lathe and sand down the shell just a bit.
I'd keep them at .752" - .753".

Mike
I would add that reducing the interference down to .001 or .002 and using locktite has worked well for me without any special KRW TOOLS. Be sure that the casting holes are not damaged from prior shackles allowed to turn and wear into the hole.
40larry

[Chuck41]

Interesting design - the torsional resistance acts in concert with the lever shocks for the shock absorption. I'll measure and sand the shell if needed to get the right interference. That bit of knowledge should save me a lot of headache!

[drolston]

I will dare to take slight exception to Kube's point regarding "torsional twist". As the spring flexes with wheel reaction to road conditions, the angle of the shackle to the spring, and to the spring perch changes by maybe as much as 15 degrees, which the rubber part resists and then gives back. That force is negligible compared to the resistance forces of the spring, and contributes little if anything to the riding quality. Most of the damping force (anti-bouncing) is contributed by the shock absorbers, with a little contributed by friction between the spring layers.

The whole point of having rotational flexing within the spring shackles was to avoid having that rotation occur between wearing surfaces that are totally exposed to dirt and dust. It would have been a risk of rapid wear with the great danger of the spring eye wearing thin on neglected cars (most of them).

I hope you got a picture of your old spring shackles with weight on the car. That would show you the proper orientation of the square part of the shackle to the spring eye, or close enough. The picture attached is the front spring eye on the stock spring I took out of my '41 when I put in reversed eye springs. If you put yours in at that angle, you should have little trouble getting the square holes in the shackles to line up. It helps to file a little bevel on the edges of the holes in the shackles. That way if you are close, a little tap with a hammer will pop the shackle onto the square peg.

[Chuck41]

I wonder if the torsion helps with sway at all. The old springs are still on the car so I'll document with photos.

I measured the new pin diameter and it is indeed 0.756", so I'll need to sand a bit.

[drolston]

Originally Posted by Chuck41

I wonder if the torsion helps with sway at all. The old springs are still on the car so I'll document with photos.

I measured the new pin diameter and it is indeed 0.756", so I'll need to sand a bit.

The torsion of the rubber in the bushing is very small in comparison to the other forces at work, and would therefore have little effect.

The front sway bar is the big contributor to reduce sway.