Plans for a water cooled gas 3.5cc (per cyl) DOHC I4

[Kosiba]

I know that the title sounds a little absurd but here's the backstory! During the pandemic I found myself cooped up inside, (as I'm a type 1 diabetic and therefore high risk) and saw this channel JohnnyQ90, and spun down the rabbit hole that is model engines! the first engine I got my hands on was a GP 43 from my grandfathers nitro plane, which he passed down. I had my fun with that motor and the guys at the airfield were ecstatic to have a young guy interested in flying planes, so I now have a garage full of old nitro planes that all need work, but this post isn't about that. Anyways last year I got a small internship that I got some money from an bought myself my first gas engine, as I am not that biggest fan of nitro engines, that fuel is SUPER expensive for some one like me! The first engine I got was the Toyan L200 and I got the gas conversion kit for it. The thing only worked 3 times and I have been in a battle with customer support to get a new ignition system, so eventually I was like, well to hell with it, I'll design my own engine and it'll be better then theirs'. So around Christmas I started design this engine and only yesterday did I get my first look a what a final version might look like! And I've been having fun scrolling through some older post here and figured I might as well show what some of these post have helped with without them realizing. Mind everyone that sees this, it's not finished and needs a bunch of stuff like, and oil pump, scavenge tank (it's a dry sump oil system), a water pump and some timing gears (I didn't want to use a chain) and a bunch of other stuff, but here you go!

Here's the block and everything

Internal mechanisms
And yes, those are some really long spark plugs!

Top down view of the head, without the cover

Bottom view of head
There is a complicated oiling system in the block and head and head cover and I don't quite know how best to show them so I might revisit this post with better pictures or videos later, but onto the pistons!

Simple piston to use 2 piston rings

Said ring

Crankshaft, it's the typical flat-plane, and has no oil passages as I have no clue how I would implement those into this design currently without having to rework it completely and the block and current crank bearings, which are next!

Current 2 part bearing design, is it the best, no, but it is what I think might work.

Bottom of block, the slots cut out with a hole in the middle of them (bottom left of each cylinder cavity) is for oil squirters, I know that these are more typical on life size engines, but from my understanding it helps keep the pistons cool and con rod lubricated so I thought no harm in designing them!

The oil squirter, this really only redirects the oil to be pointed at the bottom of the piston.

This is where the oil squirter would sit and redirect the oil.

Top of oil pan if any of you are curious.

Any way that's it for now! If anyone has any suggestions or questions I be waiting!

Vincent Piechocki

Yes I'm using onshape, it's free

 

[GreenTwin]

Vincent-

That is a pretty cool engine design.
I looked up OnShape, and it looks like a nice program, especially if it is free.

I must admit that I am not a fan of some of the ready-to-run or ready-to-assemble kit manufacturers, since they really seem to be flooding the market.
They have some fantastic engines for sure, but for me, having someone else do the design and machining takes all the fun out of the build.

For someone without machine tools, ready-built engines are one way to get into the hobby sort of; at least one would be familiar with the small parts, and how they fit together.

I like your design.
I don't know enough to comment on how to improve it.
I am very much into old-school engines, generally from pre-1900, both steam and internal combustion.
And I like one-cylinder engines, and so all my motorcycles are one-cylinder, generally in the 500cc range.

I did build a two-cylinder steam engine.

You plan on making this engine, ie: casting/machining/CNC, or whatever ?
Building and running the engine would reveal how solid the design is.

.

 

[Kosiba]

Vincent-

That is a pretty cool engine design.
I looked up OnShape, and it looks like a nice program, especially if it is free.

I must admit that I am not a fan of some of the ready-to-run or ready-to-assemble kit manufacturers, since they really seem to be flooding the market.
They have some fantastic engines for sure, but for me, having someone else do the design and machining takes all the fun out of the build.

For someone without machine tools, ready-built engines are one way to get into the hobby sort of; at least one would be familiar with the small parts, and how they fit together.

I like your design.
I don't know enough to comment on how to improve it.
I am very much into old-school engines, generally from pre-1900, both steam and internal combustion.
And I like one-cylinder engines, and so all my motorcycles are one-cylinder, generally in the 500cc range.

I did build a two-cylinder steam engine.

You plan on making this engine, ie: casting/machining/CNC, or whatever ?
Building and running the engine would reveal how solid the design is.

.

I have no way of currently machining this engine as I'm still in high school and have no money to externally manufacture the parts, but I do plan on making it a reality in the near future. And yeah for the price ready to run kits are not the way to go, and I say this from experience. Customer service is ok, but all the parts are made in mass and defects are really common. I got the engine in August and ran it 3 times, not it just sit in my garage.

 

[GreenTwin]

Does OnShape allow motion studies ?
I have found those to be extremely useful in Solidworks, since if you assemble the engine in 3D, and run a motion study, the engine will not run if there are any conflicts.
That one option (motion study) is worth its weight in gold in Solidworks.
.

 

[Jasonb]

From a practical point of view what I would say if you intend to make it is can it be done. In those crank case halves I see a lot of very small internal radii that are proportionally very deep. This will be very hard to machine due to needing small long cutters, even if you had 5-axis CNC it would be difficult and also costly due to run times as the smaller cutters can't remove as much or be fed as fast. larger radii wil make machining easier but then you nee dto consider the reduced crank and big end clearance these larger radii create

Likewise the end bearing housings will be difficult to bore with the reduced diameters on the external faces