Just kidding on the Engineers only thing. :lol:

Once again, your wisdom would be welcome.

My tiny little mind gets to wanderin' while wrenchin' away in the garage these days. I'm hooking up all this expensive and shiny new stuff and have realized that I have some questions about hardware.....to wit:

How come sometimes the General used a bolt-lock-washer-nut combination, and then other times used a bolt-flat-washer-nut combination, and then still other times used a bolt-crimp-nut, and then to confuse me even more, sometimes used a bolt-French-locks, etc.? :crazy: (Believe me, there's more).

For instance, the upper A-arms to frame are bolt-crimp nut while the gas tank straps are bolt-two-nuts (maybe three according to the kit I have) and the front shock lower mount is bolt-flat-washer.....however, the gas tank support to frame is bolt-flat-washer-lock-washer-nut.

What factors into determining the hardware choice at the design stage?


[Modified by 67HEAVEN, 7:07 PM 8/12/2002]

 

Econimcs and how much tension/stretch the bolt is under. Bolts with low tension/stretch (like the gas tank straps) need some form of positive locking nut to keep from vibrating off (lock nuts, double nuts, deformed thread nuts). Where possible this can be a cheap nut like a speed nut or similar. Bolts under medium tension can get by with the "extra resitance" provided by a lock nut, or someimes the vibration resitance of a star washer. Bolts pre-loaded to high tension/stretch (head bolts, main bolts, rod bolts) can usually do with just a plan nut (a flat washer is often used to make sure the nut load is distributed uniformly or to avoid surface cutting on softer materials).

-Greg (engineer ;) )

 

'67, the type of fastener and the material that was used, was a composition of the strength required for the particular part in question, what it's function was, the finish (cadium plating is more expensive than black phosphate) and the cost per unit. The amount of labor to install the fastener was also factored in, emblem speed nuts go on fast, head bolts have to be torqued in sequence. :D

 

The designer had his system reviewed by Chevrolet Fastener Engineering, who made recommendations for the type of fastener that would do the job for each application. A fastener engineer's primary consideration is clamping force; achieving it at assembly, and maintaining it over a long period of time. Lightly-stressed applications (like the fuel tank straps) require a completely different approach than a highly-stressed application like heads, rods, mains, and safety systems like suspension, steering and brakes. Fastener engineering is FAR more complex today than it was 35 years ago, and there is a much more broad spectrum of solutions available to the designer these days in order to deal with reliability, durability, safety, warranty, and zero-maintenance customers, all of which have to be balanced against piece cost factors and the investment required for VERY expensive torque (or torque-and-angle) control fastening systems in assembly plants.

Very few air tools are used these days in assembly plants, especially for safety systems - almost all of these applications now require computer-controlled DC electric nutrunners that sense both torque and angle, and feed back the result on every single fastener to the car's computer records. One single-spindle nutrunner like this costs about $11,000.00, plus another $2,000.00 for the computer interface box; I've bought thousands of them. Nothing is simple any more....

 

Interesting responses gentlemen. Thank you.

I still can't figure out why they sent three nuts per side on the gas tank strap (one with star washer and two regular nuts). :D

 

They sent you extra for the drop'sies... :D

 

Maybe they sent extra parts because it can go one way for one application, and another way for a different car / tank / setup..... ??? I think the vendors like to simplify things for them, not necessarily for you. :D