Design Review #1

Bill, Fred, Mark...
You guys have given me further incentive to work on this project, the design of a light-weight passenger car for the C&TS RR. It is just amazing that I've now got help from professional people in Alcoa, Boeing, and BNSF. Although I'm basically a "loner", I'm also a fairly good listener. So, your inputs are greatly appreciated.
I'll try to comment on some of the points you've brought up in this latest thread. I spent a long session at the fine Multnomah County Library here in Portland, Oregon, today, looking at what they have on structural engineering. It isn't much, but it's a start. One reference had a complete section on aluminum structures. (The copy machine gives me 11 x 17" copies for 10c each, so I now have the whole section.)
From the start of this project, one of my greatest concerns has been the fact that steel and aluminum would have to be joined somewhere in the railcar. I can't imagine couplers or wheel tires being anything except steel. And then, the truck and draft gear springs would almost certainly be steel. So, intuitively, I relegate the trucks and draft gear to steel. Now, one is tempted to opt for steel center sills. My notion is that you should not. We are dealing here with short trains, at most thirty cars. We do not have large loads to pull. I honestly think that we could run a string of 56 WP&Y trucks (28 cars worth) on a 1" diameter aluminum rod, and not even approach its practical load limit. So, what I want to do is to minimize the AREA of contact between steel and aluminum. My notion is to do this by joining the steel draft gear assemblies to the aluminum center sills at carefully engineered joints at the ends of the cars, and the cast steel truck pivot bearings to the aluminum body bolsters by similarly carefully designed joints. I assume that these connections would be done with stainless steel bolts and some kind of layer to prevent galvanic corrosion.
Now, it is quite clear that welding is not quite a simple option as it is in steel structures. However, in parts of the railcars that are not highly stressed, it would certainly be the best way to go. Examples would be the side and end trusses, which would be welded in fixtures. Although both would contribute to the mechanical integrity of the car, they would never be severely stressed. (Except in the case of a wreck with cars overturned. This "worst case" must be considered.) I think of everything above the floor as being basically just a shelter from sun, rain, and cold; a "tent" in which the passengers ride. It need only be sturdy enough to not collapse if the car rolls over.
There are some facts about aluminum that are very useful in contemplating this notion of building C&TS RR cars out of the material. The most interesting, to me, now that I have really started the necessary research for this project, is that aluminum is the most abundant metal on earth, comprising some 8% of the crust, in various oxides. Pure aluminum is a soft, malleable material with low tensile strength. However, when small amounts of alloying metal are added, the physical characteristics of the metal change dramatically. The primary alloy is magnesium. In the most advanced alloys, the strength of aluminum can approach that of steel. Not equal it, but approach it. (The reason that alloys change the physical characteristics of a metal is that they invade the crystal structure, create disruptions, and essentially cause the host metal to become a completely different thing.)
In my next post on this subject, I'll attempt to deal with the financial aspects of this proposal. That is, to build new, light-weight, passenger cars for the C&TS RR. And, as another aside, I want to mention that I've sent six photos from my visit to the Hamilton Construction shops north of Seattle to Jay Wimer at The Goat, and I assume he will post them some time early next week.
Bob Keller
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