I have a 1961 Vette feb. build. I need to know if leaf springs are a judged item. If they are what would be an exceptable stamping date and where can i find them.810-790-0479 Jeff
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Re: 61 Leaf Springs
Jeffrey, Judged,yes. The date code is located on the shortest spring (one on the bottom). The code and spring numbers are often obscured by the spring/shock absorber retaining plate. Regards -
Re: 61 Leaf Springs
The springs should be of the four leaf pursuasion, banded in three places with stainless banding, resting in a rubber gasket showing slashed tooling marks. The band clamp at the top should resenble the letter "H" with a circular dimple debossed in the canter. The three bottom leaves should be painted semi-gloss black over a suitable self etching primer such as DP-90. The top leaf should be painted silver over a self etching primer such as DP-40. The liners have metal clips at each end and are made of moisture impervious composition board wrapped in fabric. Thin strips of composition board are stapled into the liners over the seams of the fabric and fit into the grooves of the springs. The entire liner assembly was wax impregnated.
These springs got a heavy dose of eggshell blackout paint during the CHASSIS blackout process just before the body drop at St. Louis. They were on the chassis so you should see everything painted on the top and both sides but not on the bottom. This blackout turned the top leaf into black except at the eyelet ends as a rule but not always. The coverage, amount of paint, and technique depended on who was on the paint guns at the time and how the painter "felt". Monday and Friday cars were slightly deviant as were those made just before holidays.
Hope this helps. All the above is what can be seen in judging. If the springs are installed correctly, part of the part number sticks out from the top side of the shock mount but the date code cannot be read since the shock plate obscures it!
Good luck, Dale PearmanComment
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Re: 61 Leaf Springs
I'm gonna spring an afterthought on springs. Everybody thinks that they have to rearch them. Half the time that isn't necesary. Stretch a string taut from the center of one eyelet to the other. Measure the drop in the center to the top leaf. GM says 5 1/2 inches. I do mine at 5 3/4 inches. 5 1/4 isn't enough.
Rearching is only a third of the story. These springs should be disassembled and re-anealed. The re-anealing process restores the molecular integrity of the steel and the finished spring will hold it's shape MUCH longer than those not benifiting from such treatment.
Re-anealing requires a furnace to heat the leaves to cherry red and they are immediately quinched in an oil bath. When cool, the top leaf is cold bent for a 5 3/4 inch drop and the other leaves are cold bent to conform to the top leaf. Thats all there is to it. Specialty spring shops that service tractor-trailer springs usually have the means to re-aneal individual leaves.
I've been through this a time or two! By the way, the number one criterion in buying or judging springs is to determine the absence of rust pits. These can be filled in with JB Weld or whatever but pitted leaves mean weak leaves and these puppies were not that strong to begin with. The grooves weakened the whole assembly.
Adios,
Varoooooooooooooooooooooooooooooooooooooooooom!Comment
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Annealing vs. heat treating
My materials science is a little rusty, Dale, but heating them to cherry red and quenching is actually a heat treatment than increases the yield and tensile strength of a medium carbon steel. If heat treated steel is heated to cherry red and then allowed to cool slowly this would anneal the material and reduce yield and tensile strengh to pre heat treated or "annealed" state. This would be required prior to re-arching. Trying to re-arch a spring without first annealing it could break the spring. After re-arching, the spring would then be re-heat treated by heating and quenching. This same process is used for anti-roll bars, which are also made from medium carbon (about 0.4 percent) "spring steel". Sometimes medium carbon alloy steels such as chrome-moly (4130) or nickel-chrome-moly (4340) is used when section thickness goes above about an inch. Alloy steels aren't any stonger in the annealed or heat treated state, but the heat treatment will penetrate deeper on an alloy steel section than a plain carbon steel section, which yields a part with more uniform strength properties through the entire cross section.
DukeComment
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Re: Annealing vs. heat treating
Gosh darn if you ain't right Duke! I done used the wrong word again. Rest assured I'll always say, "HEAT TREAT" instead of "ANEAL" from now on. This spring shop where I go always heat treats the work before bending. That's OK because very little bending is ever required, and the risk of cracking the metal is almost non-existant. With a fresh piece of flat steel I can see that anealing would be a requirement before bending. Heat treating would then follow. Thanks for catching my misuse of terms. That's whatcha get with cheap redneck help!
Varooom!
P.S. My spring shop hasen't cracked a spring in the 20 years I've been going there.Comment
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Re: Annealing vs. heat treating
Original leaf springs were manufactured by Chevrolet's selected supplier. The following is a BRIEF description of their method of manufacturing:
1. Material was ordered to the correct SAE spring section and chemistry (the majority of GM leaf springs were made from 5160 high alloy spring steel), as defined by the spring design and drawing.
2. Material was sheared to the proper blank length.
3. Leaves were processed according to print specifications. Main leaf had up turned eyes located on each end, mid-year main leaf was pierced and trimmed on each end, secondary supporting leaves were either cut to proper finished length, tapered ends or pierced for retaining clip locations (clinch or bolt type).
4. Main leaf and all secondary leaves were heated (high heat furnace) and formed. The most common forming equipment was a "GOGAN" carousel, which formed each leaf individually in fixtured forming dies until the correct contour and proper flat center section was achieved. After all leaves were formed the carousel continued it's circular cycle and ejected each leaf immediately in quench oil. The angle at which the leaf entered the oil was critical to the fatigue life of the finished spring. After all the leaves completed the quench cycle, they were immediately processed through the draw furnace to print specified brinell hardness. This entire cycle was a continuous in-line production process.
5. All leaves were shot peened on the tension side to reduce spring sag. The shot peening specification was a print requirement and determined by the "almen" (Chevrolet preferred the "A" scale) reading. Shot peening coverage on General Motors leaf springs was a minimum of 95% of the surface area.
6. Finished leaves were then assembled with a fine thread fillister (round) head bolt with a standard heavy nut. The excess bolt was then trimmed off with a shear.
Dale, in my early career I often used the metallurgical term "annealing" in place of heat treating and was "PROMPTLY" corrected by the chief engineer. Annealing simply transforms the materials structure suitable for subsequent cold forming or machining operations.
Note: Corvette stabilizer bars were manufactured from steel ranging from 1050 to 1090 and were formed with a similar process. The bending method utilized was referred to as a "forming board" with multiple hydraulic cylinders in bend areas in various plains.
Note: Mechanical "re-arching" to achieve proper load height (without the complete forming cycle, heat treat and more importantly shot peening), will not provide the desired long term results. The key to spring life and sag resistance is a combination of heat treating and shot peening. Those two factors are the science of spring design. The SAE (Society of Automotive Engineers) publishes a Handbook titled "Application Of Leaf Springs-SAE Publication number J788" my copy is supplement 7 from the 60's. This publication, in addition to the General Motors engineering standards book, was the design guide that defined leaf spring design for the Corporation.
Duke, as always enjoyed reading your response. Hope my attempt for a brief explanation on spring design is useful.
Best Wishes, Franz EComment
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Re: Annealing vs. heat treating
Franz, I enjoyed your expert description. Did you work at Chev Spring and Bumper, Livonia Mi? I helped make many a 71 Corvette front bumper!Comment
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Re: Annealing vs. heat treating
Hey, Franz E:
OUTSTANDING contribution re spring manufacture. I've learned a lot! Thank you.
Dale PearmanComment
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