Posted by Matt Wilson on Monday, June 03, 2002 at 7:21PM :
In Reply to: More meat posted by David Sherman on Sunday, June 02, 2002 at 7:09PM :
Hey Norm,
Please don't take offense at the message below, but I thought I'd just make a point toward something I think is a common misconception with regard to heat-treated parts.
I'm not sure what you mean when you say you don't know if any light trucks use heat-treated steel, but virtually every metal part (steel or aluminum) in a car or truck is heat treated. Axle shafts, gears, bearings, crankshafts, countershafts, many pins, other shafts are all hardened to varying degrees to achieve the desired strength and wear properties, and then they are tempered or "drawn" to reduce their brittleness after being hardened. By the way, "tempering" does not mean "hardening." It means just the opposite. Tempering is done after a hardening operation to reduce hardness so that the components are not so brittle that they will break or chip when dropped on the factory floor or impacted during usage.
Other components like many stamped, forged, or coldworked components, including axle housings and probably frames and suspension components are also tempered (i.e., "drawn") to reduce their brittleness which would cause premature cracking of those components after such severe cold-working that some go through during fabrication.
Even power steering components are carefully heat-treated in varying manners to achieve the desired properties for long life and safety. Other steering and suspension components are highly tempered so that they will not break in a collision and thereby they will remain intact and allow at least amount of control to be retained by the driver.
I know about these things because I worked in various GM plants a few years ago and I have bachelor's and master's degrees in mechanical engineering (and no, I'm not one of the a-hole educated types that are mentioned in other postings on this forum).
I'm just making a point that there is a WHOLE lot more that goes into making a vehicle than a lot of us think.
I have to agree with you, though, you may have a point about the lighter structures of the vehicles built today. A sizable dent, gouge or careless welding may be enough to compromise the integrity of today's vehicles more than it would have many years ago, although I think even today's trucks would probably have to be worked fairly hard before this compromise would show up.
To illustrate, a buddy has a 3/4-ton Chevy (1989), and in a prior life it was used HARD in the oil fields, to the point where it has many cracks in many parts of the frame and has had them since he bought it. He bought the truck with 65,000 miles and has put on another 200,000 miles (with same engine, mind you) and the cracks have yet to cause any problems. Granted, most of the time he drives with only light loads or no loads in the bed, but it's just a point.
The same principle applies to aircraft (which I've been involved with for 6 years now), but they ARE much more sensitive to physical/mechanical damage. Many times it takes only a small amount of mechanical or corrosive damage to an aircraft component to cause it to crack and break due to fatigue, whereas a similar amount of damage on an automotive component would do nothing.
Anyway, I sometimes think our new ones may be better than we think, when I look at the underside of an F350 or Dodge 3500 and see huge leaf springs, steering joints, thick frames, etc. We can look at the axle shafts in our flatfender Power Wagons and say that they were underdesigned, and then we can point at a new vehicle that chucks driveshafts under heavy load and say it's underdesigned. I think old ones and new ones all have their weak and strong points. In my mind, it's hard to say which ones are stronger overall, but I still like to think the old ones will out-do the new ones!
Matt
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