New Engine Design thought process

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Mar 30, 2024
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Hi all,
I have never built an engine before. I've played with my 2 stroke motor in my 1/5th scale dessert buggy, and my 2 stroke weed eaters.
I work for a company that sells machinery, and know many of the features and benefits of what we sell, but knowing how to use them, and how to do what I know they can do, I'm a little lost.
So I thought I'd dig up an old idea and desire i had from years ago, and attempt to make my own motor to go into a scale car.
Or have it so it would fit into an aircraft, but I may look at making a raidal for that, as I really want to build a Corsair, and want it to scale and spec.
I guess what i'm trying to work out, is what materials can I use?
Thinking for ease of using 2 stroke gasoline, but later on, I wouldn't mind working out how to create a lubricating engine, but I don't want to make it too complex yet.
What things should I consider prior to starting to build?
I had been looking at the opposing piston engine that INN engine has come up with.
I wouldn't mind doing a 3D printed version of it for fun, and then see if I can go somewhere with that.
My 2nd problem being, i'm new to cad drawings, and so trying to draw some of these parts is not easy.
But assuming I can get drawings done, and see if simulations say it will run, then I guess it would be working out my materials.
Designing engines is somewhat of a round-robin affair for me.

I drew a few model engines in 2D CAD, but I really started learning when I got into 3D modeling, and 3D simulation.
I learned to run a simulation after each new part was added, to verify that the simulation would still work, and check things like part collision.
If the simulation locked up right after a new part was added, there was a problem that that particular part.

And then you have to get a feel for the size of things like crankshafts, etc.
Shafts that operate well in 3D modeling may flex in real-life use.

And there is a bit of an art to selecting alloys of metal, especially in a design that is going to produce a significant amount of power for a significant amount of time, such as a model airplane engine.
Tradeoffs between hardness, ductility, machinability, wear, thermal expansion, etc.
Power-to-weight ratio will be important for a model airplane engine.

I think steam engines are easier to design than IC engines, since they generally run at slow speeds, and thus are much more forgiving of design shortcomings.

IC engines are quite a bit more complex, with higher speed, ignition systems, timing, lubrication, dynamic balance, etc.

One of the methods I have used to learn modeling and foundry work is to read a lot, and avoid the mistakes that others make.
There is no sense re-inventing the wheel; take advantage of what others have learned through trial and error.

Its a great hobby for me, and it can be figured it out with some dilligence.

Good luck.
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Look at existing designs of model engines and also your RC engines and see what materials they use. Most will tend to be as follows.

Aluminium for crank cases, pistons and heads. 6081 or 6082. All cut from solid forget castings at this stage.

Conrods again aluminium but 2014 for strength

Cylinder most models will run a steel or cast iron liner, don't worry about fancy coatings for now

Viton piston rings or cast iron

Crank shaft in the US is likely to be "stressproof" steel

Cams drill rod

Valve stainless steel

And the rest are minor items.
Thanks guys,
I may try and do something relatively simple to start off, and copy/draw and then build something that has been done before.
Get an idea from that, after that I can try and make things a bit more complex.
I need to spend more time learning how to use a cad program. I use Fusion 360 and have learnt some things, but trying to translate what i can do in my head, and finding out how CAD does it are two very different things.
I start my designs on a spreadsheet, I've made one that estimates things like power output, valve sizes, stresses on bearings and conrods etc. Once the basics (bore and stroke, compression ratio, bearing sizes) are figured out I can start designing in CAD and put my parameters back into the spreadsheet to refine the concept.
Such a project should also be a success experience.
I would therefore suggest first building a proven and simply constructed engine from a commercially available set of castings.
Regardless of making your own design and your own CAD drawing,
there are enough problems when processing the components.
With such a set of cast engine parts you can first test and improve your metalworking skills.
An internal combustion engine does not forgive small construction errors as easily as a steam engine.
Thinking about a radial for a Corsair in your first project is quite brave.
I would start with a single cylinder engine first.
If you stumble from problem to problem on a large project, you can easily lose motivation.

Here I have two links to addresses in Germany where you can buy kits for internal combustion engines.
The first hompage (bengs-modellbau) is available in English.
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Personally, I would choose webster engine plan
- Free plan
- Built from bars
- No need to design yourself, no need to calculate....
- Simple for newbies
- If a part is machined incorrectly, Easy to make another one from the bars
- Get help easily
- ....
Or rely on the plan to design or change according to preferences

Webster Engine Plan :
********** Best choice for newbies *********
Personally, I would choose webster engine plan
- Free plan
- Built from bars
- No need to design yourself, no need to calculate....
- Simple for newbies
- If a part is machined incorrectly, Easy to make another one from the bars
- Get help easily
- ....
Or rely on the plan to design or change according to preferences

Webster Engine Plan :
********** Best choice for newbies *********

This is of course also a cost-effective alternative.
I had not known this plan since then.
But I seem to remember that a motor like this was recently shown in operation as a short video in the forum.
Thanks for this good suggestion.
This is of course also a cost-effective alternative.
It's not a matter of cost savings...
I think it's an exercise to practice skills, accumulate knowledge, experience.... for newbies, And for newbies : it's like a test: How far will you go?
I haven't done a webster engine yet
I just looked at webster engines that others had made and looking at the plan , I made a similar engine - my way...
It's just that with my little experience, if someone builds a successful webster engine, then designing and building their own engine is only a matter of time and how far they want to go.
All good advice above, but most of all, feel free to ask questions!
There is a wealth of experience among the members of this group and that should be your most useful resource as you build your first engines.
What do you have access to in the way of machine tools and measuring insruments?

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