We spoke with Eric Harrell, a mechanical engineer with an obsession for internal combustion engines! Using a combination of CAD design, low-cost 3D printing, and a love for internal combustion engines, he has created working models of several engines, transmissions, and differentials. All with cutouts so you can see what’s going on. And, when we say they’re fully functional, you can change gears and switch from two to four wheel drive! Even if combustion engines are on their way out, this is a great teaching tool and fascinating to see. Here's a transcript of the interview we had:
Eric: There was nothing available to print for people to actually see how stuff works and see the complex mechanical assembly. So I shared the first engine that's down here and it got really popular and then I just kind of went with it and got carried away.
I'm a mechanical engineer by schooling and some work but what I have here is a 3D printed engine assembly and it allows you to see all the working innards of them. The transmission and an engine, all the moving cams and camshaft gears, everything. I designed it while I was rebuilding the actual engine because there was nothing available to print for people to actually see how stuff works and complex mechanical assembly is available. I shared the first engine that's down here and it got really popular and then I just kind of went with it and got carried away.
Josh: Is this a full-time endeavor or a part-time endeavor?
Eric: It just started being a full-time endeavor. I try and make all my files open-source so people can download them and print their own. I sell hardware kits, so that's what I'm trying to focus on. I'll produce more models and more hardware kits but still keep the idea open-source so people can learn about printing or about engines and mechanics.
The biggest learning curve was probably gearing on the transmission but that was so long ago that the learning curve was very steep. Once I get got that figured out, it's just pretty much smooth sailing from there. Also, having a way to visualize all the moving parts is tricky for putting cutaways in the right sections. Being able to see the moving parts because I want to maintain the visual look of the real thing, without making it cartoony or toy looking. So that's what the challenge is on all the engines.
Josh: Could you demonstrate this working?
Eric: So this is a 5-speed from a Toyota four-wheel drive pickup. That's neutral. So that's first gear and then that's second. That's third gear. And then fourth gear. And that's fifth and reverse. And so this is a four-wheel drive so it also has a transfer case. So that's it's a four-wheel drive right now. That's two-wheel. That's four. And then that's four-wheel drive low. And back in four-wheel drive high.
Josh: What has been your favorite part of doing this project?
Eric: I love the CAD part. Sitting down and designing it and being able to see it before I print it but being able to take the design and go to the printer and have something that's tangible in my hands within a day and seeing it work. After being designed, it's very cool.
Josh: I see the 3D printer over there. Is that the actual 3D printer you use?
Eric: I tried it on the cheapest printer I can find so that's a sub $200 printer. It's a kit you build it yourself. If my printer can print it, anybody's printer can print it as long as it's big enough. Everything here is printed on that machine and everything comes out as you see it here.
Josh: Do you have any recommendations for somebody that wants to get into this or wants to recreate it using your files?
Eric: Yeah, somebody wants to print one of my engines. The easiest one is probably the Toyota four-cylinder. It's just has the least amount of moving parts. And it's the smallest if you have a limited size on the printer. It's also the least amount of print time. So it's about 100 to 120 hours of print time total for all the pieces. Compared to the other ones, the V8s are about 200 hours of print time. The transmissions are probably about 200 also. So it's a good amount of commitment but, you know, it's a good learning experience.