Question from the part of the article where the piston is introduced: We know what constrains the up and down positions of the piston; What constrains the direction of rotation of the crank?
Internal Combustion Engine
371–380 of 415 posts
Re: Internal Combustion Engine
#372Can we have better titles please?
Re: Internal Combustion Engine
#373That was awesome.
I'd love to see another with the Wankel engine!
Re: Internal Combustion Engine
#374I’m a lowly mechanical engineering lecturer. I use Jupyter notebooks to teach fluid mechanics[0]. I make videos of fluid flows with Blender and embed them with the notes along with some basic Python code examples so that students are aware of how basic code can make an Engineer’s life easier (even if Matlab is the standard platform). I also embed simple 3D models with pyGEL3D[1]. It’s fine but very limited. I’m alway…
I'm on mobile so linking is a bit of a schlep.
1. MDN is a good starting point to learn Javascript.
2.Then the three.js library for 3D in the browser.
3. Maybe P5.js as well for 2D.
Re: Internal Combustion Engine
#375Earlier quoted context omitted.
Rotaries are a funny case. Look good on paper. Thermal efficiency issues. Smog. Seals. Noise control difficulties. Weird patches like bridge ports. For modern passenger cars, it's kind of like overcoming the difficulties of two-stroke. In anti-defense of 4-stroke ICE, it seems to me like we are hitting peak wacky complexity of those. Variable timing cams, turn off the cylinders, direct port injection, turbos, variabl…
The problem with ICE industry is that nearly nothing improves much in absolute terms. If you take a look at list of ICE records, nearly all of them were made decades, and decades ago. Biggest piston engines - early 20th century Most powerful piston engines - fourties Most efficient piston engine - Jumo 204 held the record until nineties Most power to weight - eighties Uncounted billions put into engine RnD were mostl…
> Jumo 204 held the record until nineties
And what has happened since then? Google is showing me several engines with breakthrough efficiency in the last 10 years.
When I was a kid in the 90s, SUVs commonly got 12 MPG. The new models are 25 sometimes 30 MPG. Emissions have gotten considerably better in the last 30 years.
I’m looking and can’t find any info to back up the claim that this 1920s engine was more efficient than engines designed in the 80s and 90s. I am curious about it, not just is it true, but specifically what kind of efficiency you mean and what design features made it efficient. Do you have any sources or reading? Wikipedia talks about how the arrangement of the valves increased the efficiency, but only says this made it approach four stroke efficiency (at the time), not that it exceeded other designs. The 204 was a two stroke, and it seems to be common knowledge that even today, four strokes are more efficient. https://en.wikipedia.org/wiki/Junkers_Jumo_204
Re: Internal Combustion Engine
#376Isn’t it risky for the timing to rely on a rubber belt? Does it never slip? Even a mm of slippage seems like it would make the valve timing stop matching the pistons?
Yeah it’s one of those things that you just have to replace every X miles just to be safe. I got one replaced a couple of days ago because the service history was missing and I couldn’t tell whether it had ever been done. If your timing belt goes you’re in all sorts of trouble.
When I started driving German cars (may be coincidental) I noticed my mechanics would write the date and miles of the service directly on the parts.
My Toyota actually had a small decal on the timing belt cover itself specifically for the purpose of tracking that service.
Re: Internal Combustion Engine
#377When I was a boy, my dad decided that our '66 Mustang with a straight 4-cylinder engine needed new piston rings. I helped a bit but mostly watched as he tore down the engine to the barest elements, only the engine mounts keeping the block held up in the compartment. The crankshaft, connecting rods, tappers valves, piston heads, piston rods, all laid out neatly on the garage floor along with all the nuts, bolts, washe…
I think the design of a wiring harness is actually a good analogy for a well-created API, in that it provides a handful of endpoints, each of which fulfills a "contract". On modern wiring harnesses, it's pretty hard to connect the wrong thing, because the connectors are physically "typed", in that the male and female sides are uniquely shaped so only they will mate up, rather than having a generic connector that plug…
If you're doing minimally invasive wrenching on stuff that is in good condition electronics are fine until you have to do serious work to them.
Grafting two engine harnesses together because you can't buy the one you need (because nobody sells that stuff for 20+yo vehicles) will make you want a carburetor.
Re: Internal Combustion Engine
#378Earlier quoted context omitted.
I love this idea. The best way to get academics to buy in would be to have some clear outcome such as a publication or funding opportunity. There are a lot of clunky engineering tools that would benefit greatly from professional software development. Computational Fluid Dynamics software in particular is just plain awful in terms of usability for beginners.
What are the names of some of this software that are a good example of in-use but are clunky/have awful usability? I ask because it sounds like an interesting area, and I would like to see for myself what you're working with.
On one hand there is Ansys. It’s a Frankenstein’s monster of a software suite for numerical simulation comprising several tools that have been acquired over the years. It’s frightfully expensive and there’s no incentive to make it more usable as there’s limited competition.
Then there’s OpenFOAM which is a fantastic open source alternative. It’s entirely command line based but there are UI derivatives and cloud based versions (SimScale). However it’s a nightmare of disjointed code, difficult to build and heavy on dependencies. You spend all your time dealing with endless problems related to defining simple geometries in the basic BlockMesh tool and then dealing with and compiling various solvers. It’s a research grade tool and not a polished piece of software. I won’t go into the various versions with incompatible differences.
Getting the most basic stuff working is tedious and frustrating in both.
After a few years of this masochism you just get on with it. However, when you are trying to guide students through the software for their final year project they spend about two thirds of their time just figuring out how to get something simple running and then never want to touch CFD ever again.
Then there’s Blender where I can install it in seconds and set up a simple flow simulation with a straightforward workflow. Sure the result is not remotely accurate but that’s just the solver, there is no reason for the complexity of the workflow in Ansys or OpenFOAM other than it was designed by (Mechanical) Engineers who know nothing about good software design.
Re: Internal Combustion Engine
#379Really nice work! Reminds me of some of Bret Victor's stuff.
The graph saying that the velocity curve of the piston is asymmetric left-right is wrong. It should be top-bottom asymmetric instead. They got the text right though. Edit: oops, I'm wrong... the position curve would be left-right symmetric while being up-down asymmetric, but then if you take the derivative you get what they are showing.
Re: Internal Combustion Engine
#380Question from the part of the article where the piston is introduced: We know what constrains the up and down positions of the piston; What constrains the direction of rotation of the crank?
The crank's angular momentum, which is originally derived from the turning of the starter motor.