Manufacturing after-market parts and other car hobby pasttimes

So I own an old Mercedes 300D that I drive just a few miles a day to work and back. I love this old thing because it comes from those heydays before car computers where the components were simpler and could be understood by anyone willing to take them apart and explore.

I have a daydream about refurbishing the vehicle piece by piece. I do metalworking at home as a hobby and I wonder how I would find out what kinds of metals to make the various parts out of. I have a small metal casting foundry and I am building a CNC mill that will be accurate down to .001" as well as a huge hydraulic sheet metal press that I will be able to make molds for with the CNC out of solid steel. I would love to just manufacture and replace each part of the engine, transmission, starter, etc etc etc one by one. What do you think?

Another thought; I wonder what a good way to reduce the weight of the car would be? I want to remove the back seats, but are they necessary to the superstructure of the vehicle? If so I could replace them with just a simple bracing bar machined to match the bolt holes. What about replacing the steel body panels with aluminum? What parts of the car would be safe to replace with lighter versions without hurting the strength of the structure?

A final question for someone who knows more about electronics than me: when you connect batteries in parallel, more amps can be drawn, but would a motor (say, a starter motor in a car) only draw the current it needs and wouldn’t notice a second battery in parallel, or would the batteries push more current into the system and cause problems? I don’t understand whether the motor determines the amps drawn or if the batteries push the amps through the motor…

Thanks for your opinions!

The engine and transmission are made up of extremely intricate sand castings, I can’t imagine being able to duplicate them.

With enough hard work and practice you can do anything. I don’t need it to be easy :slight_smile: Besides, doing something super difficult and eventually succeeding seems more fun than just doing easy stuff.

It’d be better left as a daydream. Sheetmetal parts can be duplicated by someone who understands how metal behaves and has the proper equipment, but that takes training and experience.

Cast parts are a different issue. Many of the cast parts sre made using specialized processes such as reverse-gravity lost-wax casting. I’ve seen this process in action producing car parts. It requires sophisticated control of the metallurgy, the processes, and the environment, as well as large vats of alloy with well controlled temperatures and homogeneity. The lower center of the vat feeds via gravity the bottom of the mold. The slag foats on top and heavy impurities sink to the bottom. Feeding the mold from the lower center of the vat enables the mold to fill without bringing in the slag and impurities. Feeding into the bottom of the mold allows air and impurites to go out the top of the mold. This makes a far better (freeer of inclusions and exclusions) molding capable of meeting modern design requirements. The mold with alloy then goes through a very controlled gradual step cooling.

Can yuo do this?

And, by the way, an accuracy of +/-.001 won’t “cut it”. You’ll need to go out another decimal or two to make many of the parts. And you’ll need a metrology system (or service).

Metallurgy, that can be gotten around if you can get original design requirements. Shops will do chemical and physical analysis for you as a service.

The hydraulic sheetmetal press would be great…except that many of the original stampings are multiple-step stampings with multiple molds costing many thousands of dollars each. It isn;t uncommon for these to be modified as the eccentricities of the metal behavior are uncovered in the design validation process.

I admire your grit. And I respect that you apparently have metalworking expertise. But to do what you’re suggesting would be massive.

You sound like this fresh-out I hired a year ago who wasn’t satisfied with Windows or Linux so he said he was going to write his own PC operating system…Needless to say it was way way way beyond his ability or even time if he had the ability.

What you’re proposing is only a pipe dream…Not going to happen.

That’s what I told Linus Torvalds years ago. I still have to buy him a drink on the anniversary. :wink:

I would personally go for aftermarket parts instead of trying to recreate them. Any one remember symantec desk top? It was a cool attempt. I was happy writing menus in dos, programs in basica and fortran, Littlemouse, I underestimated your computer prowess, but think I am sitting on the sideline wondering when and how you met the dark side.

Set your sights on something more realistic, like getting this car to start.

Linus had a starting point. He just created a Unix operating system to run on the x86 platform. So he didn’t actually start from scratch…Although a great achievement for a 19yo.

TB - keeping an old MB running is a major job by itself - get hooked into the MB forums and figure out how to get all the systems back to 100%. Then upgrade the parts like suspension, tires, etc. THEN start working on fabrication.

p.s. - Walmart batteries are about the same as others, I’ve used them for years with great success. Something else is wrong.

As an analogy I’d use the old saying about a room full of monkeys with typewriters being able to pound out the complete works of Shakespeare given enough time.

The starter motor will draw the amps it needs and that will vary based on engine wear, oil weight, temperatures, and so on. One battery or two, it makes no difference other than with two you have a bit of electrical insurance so to speak.

For what it’s worth, we have a local machine shop that has been around forever. On their wall they have a near full page newspaper story about the original owner of this shop. The story is dated 1948 and provides a series of pictures where he built a metal lathe from scratch as a spare time hobby and by using the machine shop equipment he already had. It took years and years.

You have an interesting idea but it’s really not practical at all.

Ouch that is rough. Goldwing, I got that fixed. It’s not that bad a car really. It’s been relatively well taken care of by it’s previous owners.

Not to be defensive, but why all the negativity? I want to do this for fun, not to “get rich quick” or something. Obviously I’m not suggesting going on the road tomorrow with unsafe, untested parts made from junk metal. This is something that will be a source of learning, experience and practice working with metals. I’ve already started; I’m pouring a tiny aluminum cast of the little broken plastic hood release handle tonight. It’s not complicated, but it is a starting place.

Maybe you could share your knowledge with me? For example, does anyone have a reference that would show how accurate a CNC mill/lathe (mine is going to start with 2 axis and work my way up to 5. I have the designs all drawn up and detailed) would have to be to make the most dimensionally critical components? The stepper motors of a CNC machine can be micro-stepped to increase it’s resolution dramatically and as long as the motors you are using have enough output you can then control it’s position with a laser distance feedback to the controller computer. Anyone have a diagram or book that details the casting process described by mountainbike? (Very informative and interesting post by the way, thanks!) What book do you know of that would be the most instructive about the necessary metallurgical facts and processes? ok4450, thank you very much for educating me about batteries; a lot of electronics is still a mystery to me still, one that I intend to crack. I like that story about the machine shop; I too am building my first metal lathe whenever I have the time between work and family. I have it designed and built in 3D (based on the wonderful books written by Dave Gingery) and am saving up for the more expensive hand tools I need to complete the project.

I’m thinking that taking small samples of each cast and putting it through ASTM standard testing to see if it is acceptable or not. Then I can test the parts made of ferrous metals with Magnetic Particle Testing to find cracks or other internal/external defects. Even high tech, professional factories have a casting failure rate of almost %20, so I have no illusions about trying to get it right the fist time. It’s all about patience.

I think before I made and critical parts that would go in the actual car, I would build replicas of, say, the engine and the transmission that would be stand-alone models that could be tested to see if my manufacturing processes are high enough quality. I would like to start small, like making a small one cylinder model diesel engine (like a desktop toy) that actually runs to see how I would need to do it.

The basic idea is that nothing is impossible. Those big machine shops and factories were made by regular people. All those parts and machines were designed and built by regular people. Why not me? Especially if I have the drive to learn and work hard on it.

TB - how will you be able to cast a part with intricate internal passages? They can’t be machined, only cast.

well, there are a variety of casting methods, but the most common two are either sand casting or lost-wax casting. Lost-wax: , sand-casting:

I know that, the question is how will you do it? Major equipement needed for that. I’m not trying to discourage you, but the thought of an individual casting an engine block for a diesel in their home workshop has me, well, amazed is too small a word…

well, first I would measure the original part and rebuild it in a virtual 3D space. Then, to make internal passages, I would carve sections of the part out of wax with the CNC. The wax parts are easily affixed to each other with a dab of melted wax. The wax positive would then be measured to ensure that it matches the 3D model. The wax model would have whatever gate, vent, sprue etc systems attached to it that it needed. The whole thing would be invested in a casting medium, baked in an oven to harden and to remove the wax, then the prepared molten metal is poured. Depending on the metal, it would then cool either at room temperature or in an oven to slow the cooling process to reduce stress fractures from thermal contraction and control the molecular structure of the material (the speed of cooling steel changes how the crystalline structure forms, for example. Faster cooling can result in stiffer but more brittle parts, hence the process of quench hardening).

I think you’re being too naive into thinking this is going to be easy…it’s NOT…In fact since you don’t seem to have much experience at casting engines (who does??)…then this is going to be the biggest failing. If casting engine blocks was easy don’t you think there would already a slew of companies out there doing it??? But good luck…

Uh, there ARE a slew of companies. How many car manufacturers do you think there are in the world? I’m not thinking it’s going to be easy! I already said that! I’m not doing it because it’s easy, but because it’s an opportunity to learn and gain experience. Of course I don’t have experience casting engines. Where else would I get that experience besides actually doing it?

Take a look at the size/scope of equipment needed to cast an engine block. You have that available???

Uh, there ARE a slew of companies.

Besides auto manufacturer companies…the list goes down drastically. And those the people that do it have been doing it a while. It’s NOT just the casting part…but the getting the right metal…the cooling process. If it were easy…many many companies would be doing it.

How are you actually going to MELT the metal (at least without killing yourself)??? I’ve been in a foundry…it’s one dangerous place.