Depends on design. Many military vehicles have powerpacks - modules containing usually engine, transmission and cooling - that can be easily replaced even in the field within couple of hours. Probably not practical for civilian use, but it can be done.
Castings are made from (not surprisingly) cast iron. (sometimes cast aluminum, even rarer, magnesium alloys, which would help with the weight though not the cost)
Cast iron has different properties from steel. Mainly, when subjected to force, it doesn’t deform until it shatters or breaks (i.e. you can’t bend cast). Steel bends.
Pretty sure that plays an important role.
One could say the same thing about steam engines in the 1600s (Hero having invented them in ancient times). Or the computer prior to the 1940s (Babbage’s difference engine, a mechanical computer, having been designed in the 1800s), or any other of a number of inventions. Just because nobody’s doing it, doesn’t mean it’s impractical (doesn’t mean it is practical, either, of course).
Good question.
Ever been to a modern car plant? Very little welding is done by humans. Robots pick up the sheetmetal, clamp it together and then another robot comes along and welds it, and the whole process takes a couple of seconds. All the robots are isolated so that nobody can wander into the area as no human could react fast enough to get out of the way of the robot’s motion.
Somewhat true. All those intricate nooks and crannies call for sophisticated machining techniques like Extrude Hone, and nobody’s found a way to rapidly cool down a huge hunk of molten metal (which engine blocks are) in a short period of time.
I recall that the old VW Bug engine could be pulled out and replaced in a few hours. In fact, a Quincy (MA) garage (kertzmann’s VW) wond a prize by replacing a VW engine in less than 45 minutes.
Early in the 1920’s Chevrolet tried to make an air-cooled engine-it was of cast iron bonded to copper (for heat transfer). The engine self-destructed, due to galvanic corrosion.
Say what? Surely you’re not claiming that steel castings don’t exist, are you?
And in one’s one driveway using basic tools. I knew a guy who pulled the engine out of his VW Bus without benefit of an engine hoist. IIRC, he just reached in, grabbed it, heaved it out and onto a skateboard to roll it into the garage so he could work on rebuilding it.
I see your point, but the reason I said it that way is because unlike your examples, we’re already experts at sheet metal fabrication, and already experts at casting, and already experts at gasoline internal combustion engines, and presumably we’re not looking for a new invention or even fabrication process, but only doing what we already do, to build what we already make, in a different manner.
Sheet metal tolerances are sloppy loose on all modern car bodies, at least when you compare them to engine tolerances. I’m talking in the neighborhood of ±0.5 mm being about the best case for repeatability in most subassembly marriage operations. This is all designed into the car, so you get good leaking sheet metal alignment (except for all but the most recent Saturns – yuck!) despite these tolerances. In any case, the robot has nothing at all to do with dimensional control (unless its position is grossly, grossly off); it’s all controlled through a series of different types of locater points, which can be holes, slots, edges, and so on. Every buildup of subassemblies up to the marriage points as a body-in-white depends on locaters interfacing with the locater points, i.e., some external fixture (which could be a robot end effector on a non-welding robot). In some cases vision systems are used for roofs, since locater holes present an obvious problem there.
Engine blocks then have the added problem of weld integrity. I left the body shop and built steel fuel tanks for about four years, and with all of the best technology and large budget, there was no way to ensure that every single fuel tank that was welded would be acceptable; as a consequence, they were subject to 100% inspection and rather high scrap rates compared to most stamped assemblies. Even something simple like a resistance spot weld – when you weld 2,000,000 welds per shift – leads to rework and scrap, and spot welding is an easy, simple, proven, ancient process (in relative terms, of course)!
Could we invest the money to guarantee absolute sheet metal precision for a stamped engine block? Maybe… (I don’t think so, but am willing to accept the possibility)… but would it be worth it? The only thing that can go wrong with castings is bad dies, bad material, voids. It’s dirt cheap, proven, reliable.
In the end, yeah, you could build a sheet metal engine block, but you couldn’t currently make it work economically.
(Reminds me – the American Welding Society Semi-Annual Sheet Metal Welding Conference is next week in Plymouth; feel free to drop in! It’s full of welding people, sheet metal people, materials people, stamping people, and I’ll ask if there are any engine people.)
Well, I have to think that we’d wind up coming up with some new fabrication processes. Not quite the dramatic change from a single individual building a car to the assembly line, but we’d have to make some changes.
I presume you’re talking about domestic car makers. I’ve made a number of different parts for the Japanese, and I’ve never had that kind of broad tolerances in making parts for them, even when it was a “cosmetic” feature. Right now, the parts I’m making for Honda and Toyota have what we consider to be a “broad” tolerance in one area and that’s +/-.2 MM, all the other tolerances are in the +/-.005MM range. Now, admittedly, that’s not a sheet metal part, but I have to think that if +/-.5MM is tolerance given for sheet metal, it’s a “good enough” tolerance and not the limit of our technical ability. I imagine that a laser cutter or a water jet cutter would be able to hold pretty tight tolerances, and presumably, final shaping (say curves and the like) being done by a stamp.
Yeah, I don’t think I’d trust friction welding to do a good job. How were the inspections carried out? I know that X-rays are some times used to check welds and, at least as far as medical X-rays go, there’s been studies showing that machines can analyze X-ray images faster and more accurately than humans can. Not saying that a machine could do the same for an engine block, but it might be possible.
Of course, if we’d have stayed with what was “dirt cheap, proven, reliable” we’d have never bothered to come down out of the trees and walk upright! 
Cost, could be a real bugaboo, I’ll admit. After all, if (ignoring things like R&D and start up costs) you wound up will a block that cost more than your typical Mercedes car, there’s really not much point in doing it.
I don’t know.
Love to go, but no way I can make it.
Yeah, I’d consider tubing as “sheet metal” for this case. I know that parts of the air ride suspensions for big rig trucks are made using sections of aluminum tubing.
Sounds familiar, but I just can’t place my finger on who might have come up with such an idea.
Not claiming that at all. In fact you can cast most all metals, and sheet steel is cast at an early part of the production process. (once it leaves the ladle)
Cast iron because of it’s carbon content has different properties from steel. One of which is that rather than deform like sheet, it breaks, and I believe that to be a critical factor in the design for certain applications.
And yes, I’m aware of the different grades of high carbon steel
A couple of asides: the Crosley engines mentioned in the OP weren´t exactly welded, they were ¨furnace brazed¨, meaning the parts were assembled with what you might call copper gaskets in between, then put into an oven hot enough to melt the copper and supposedly stick everything together. Didn´t work very well; they leaked a lot.
Also on VW engines: the shop foreman where I worked fortysomething years ago would yell at me if I couldn´t get the engine out in twenty minutes (with a helper to hold the transmission bolts that you couldn´t get at from both sides at once) as long as the things weren´t too rusty or crudded up. And at various ¨"Bug-in" VW gatherings they have engine pull contests: drive up to a line, unhook everything, pull the engine, put it back in again, hook everything back up and fire it up. Two people working; the record is under two minutes.
Under EPA rules, an engine has to be able to meet pollution standards for 50,000 miles. However, on hybrid cars, maybe a quick-change engine would be more plausible.
The following may be quite erroneous, and I welcome corrections.
In most cast engine blocks, there are solid metal bridges (lands?) between the cylinders. This adds strength, but it’s heavy, too. There have been a few engines with “assembled” blocks. That is, the cylinder tubes are bolted into the cast water jacket box, and corralled at the top by the cylinder head. There’s no need for welding to the cylinders. I may be remembering wrong, but I think the ill-fated Chevrolet Vega engine was made this way. The cylinder is completely in contact with the coolant. Could the water jacket box be made of sheet metal? It would save weight if it could.
I am among those who believe the Vega engine would have been successful if it hadn’t used the aluminum/silicon sleeves.
Most modern engine don´t have connected cylinders. The Chevy 400 cid smallblock that was produced up to 1980 did (siamesed cylinders is the term, I think) and was notorious for overheating because coolant didn´t completely surround the cylinders. A lot of racing engines in the past had completely separate cylinders, for example the Alfa 1500 straight eights that won a number of world championships in the early fifties had iron cylinders, threaded on the bottom, that screwed into bosses in the aluminum block so the cylinders could be replaced individually. And welded sheetmetal water jackets go back at least to the 60 hp Mercedes racers of 1910, which says a lot for German craftmanship considering the primitive welding techniques of the time.