Archer Bros Monoleaf Springs

[HOrnbrod]

Ben, how do you think these would play in a SOA configuration?

 

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[Pete M]

well, if they work like every other mono spring I've ever read about (factory and aftermarket), they would suck after a very short time.  :dunno:  

[neohic]

The fiberglass leafs were intended to have a non-progressive spring rate. They lowered the rear of the Comanche's about 2", but the Archers also used a 1" block and XJ shackles. As far as durability, I was told that these things are pretty tough. So... 2" drop, plus a SOA, equals 2.5" lift?  :dunno:

 

Then there's the real question, Don... WHY?  :hmm: 

[HOrnbrod]

SOA w/o the 5+ inches of lift. More like a nice pedestrian 3+" or so.

[neohic]

Not exactly an abundance of fiberglass leaf springs around though... that I know of, anyhow. If I were to want to go SOA without a mile of lift, I'd go with Waggy springs and then play around with removing/adding in other leafs to dial it in.

[HOrnbrod]

I'd forgotten that thread. Wonder what happened to comanche09. He had a nice rig.

[Eagle]

Fibreglass -- I don't trust it.

 

I've owned two fiberglass sailboats and a fiberglass canoe. I have the surviving half of a fiberglass extension ladder, and the top rung has partially pulled out and isn't safe to support any weight. There's no way I'd put fiberglass in place of steel springs.

[gogmorgo]

There's no comparison between the loose fiberglass chop mat used in the construction of boats, ladders, etc and the carefully laid fiberglass cloth used in the making of springs. Boats, ladders, etc are made by taking something very similar to that pink fiberglass insulation, pouring resin into it, and letting it cure. Springs are made with many many layers of finely woven glass-fiber cloth, carefully arranged, and let to cure in a vacuum bag, keeping the glass fibers pressed firmly together, with only enough resin to hold the glass together.

Glass is one of the most elastic substances commonly available (i.e. it perfectly returns to its shape after deforming, doesn't sag or creep no matter how long it's flexed) and the resin holds it together and overcomes the brittle nature of glass. It's a perfect material for springs. They also save quite a bit of weight over steel leaf springs. Corvettes have been running fiberglass rear leaf springs at least since the early 80's, if not the 70's, and I challenge you to find an example of one that sagged or otherwise wore out from use. The current Volvo XC90 also uses a fiberglass rear leaf. Some 90's GM W-bodies also used them, as did mid-90's Volvo S/V90. They're also very common in motorsports applications. In terms of wear life, GM testing showed equivalent steel springs to what they use in the Corvette fail spec after 200,000 complete cycles, but the fiberglass ones show no loss of performance after 2,000,000 cycles.

Fiberglass is a good material for springs. It just comes in many flavours. The stuff they use in canoes is cheap and yes, would be terrible for springs. But when done properly, fiberglass makes for a much better spring than steel does. They're just much more expensive than steel springs (much more labour involved in their manufacture) which is why they aren't common among production cars.

[HOrnbrod]

Good rundown.  :thumbsup:

[Eagle]

The fiberglass leafs were intended to have a non-progressive spring rate.

Any monoleaf spring is non-progressive. Leaf spring packs can be made progressive by using slightly different arches for the leaves, such that initially only one leaf carries the load, then as load is added the deflection starts to pick up additional leaves. The extreme example is the overload leaf in an MJ pack.

[cruiser54]

We were installing those on XJs for the Jeep Racing guys back in the late 80s. Worked great. 

I had a set for an MJ brand new and sold them to Cobramarty on Cherokee Forum.