# Building a petrol mini engine



## Danny91

Hey!

I'm a engineer at a hospital in Oslo/Norway that make custom parts for doctors, scientists and professors.

I pretty much have all kind of tools/machines available cept a CNC lathe and CNC 5axel milling machine.

Was thinking of building my own mini-engine similar to this 
[ame]http://www.youtube.com/watch?v=h9X5l-ux1pU[/ame]

I would think a V12 of that size would be kinda dumb to start on. So i was thinking of maybe start with an 5cylinder engine (similar to the Audi engine)

[ame]http://www.youtube.com/watch?v=9yP42Cf06ic[/ame]
That size would be nice, just as 5cylinder.

After 2days of constant googling i can't really find much drawings or anyone that has build a mini 5cylinder engine. I was wondering if anyone has build one and would like to share some insight with me. Or if i should make like a 4cylinder or V2 that might be easier to start with?

Daniel


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## arborpress

If you want to start on a multi-cylinder design, I think you should build an inline 4 engine because it is relatively easy to balance. On a 4 cylinder inline engine, the front and back piston go up as the middle two go down. This is because the front and back connecting rod bearing are in line, 180 degrees away from the middle two. This is called a flat plane crank, and makes it so that a cylinder fires every 90 degrees. All 4 cylinders will fire once in one full rotation of the crank. With a 5 cylinder engine, everything is split up differently. the time between cylinders firing is different and the angle between bearings on the crank is different too, and unless you know exactly how the engine will function and what you need to do to cancel vibrations, you won't know how to calculate those figures. 
Once you start building V engines, the angle of the V will also play a huge roll. That is why V6 engines are typically made in 60 or 120 degree V angles, and V8 engines are usually 90 or 180 degree


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## Swifty

Hi Daniel, just like to point out, that in the first video, the engine is run on compressed air. In the second it is a proper IC engine with ignition system etc.

 If you are just starting out, it may be best to make a few air operated engines first.

Paul.


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## e.picler

Hello Daniel!
I agree with Arborpress. A V configuration is a complex project to start with.
I have a project to recommend to you. It is a four in line spark plug ignition from Kelly Kubischta a very nice engine (very small) 3.5 in long.
I`m building it my thread is:
http://www.homemodelenginemachinist.com/f31/building-tiny-inline-4-brazil-17438/

You also may want to take a look on Kelly`s thread building his project.
http://www.homemodelenginemachinist.com/f31/tiny-inline-4-cylinder-ic-10240/

Good luck on selecting your project.

Edi


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## petertha

Some plans here of progressive difficulty. I ordered a set to have a look & seem quite good (cad developed). They are metric if that benefits you. I recall someone on the forum built the opposed 4-cyl I believe.

http://www.cad-jung-shop.de/epages/...729/Categories/Bauplane/Bauplane_Modellmotore


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## Longboy

....The insight you are in need of Daniel is to build a beginners engine from plans. Easy to get excited over these videos of aircraft and multi-cylinder gas engines. If you've never made an I/C before its best to start with a single cyl. engine. Less time and complexity will give you satifaction and trust in your abilitys. The pleasure is there in a single......the frustration is there in blending newbees & multi cyl. engines.


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## Aerofourcycle

Daniel, 

I would have to agree with Longboy. I dream of building multi cylinder radials. But I took advice from a lot of people and started with a single feeney four cycle aero engine. "Feeney wouldn't be the best starter engine". It took me a long time to learn how to make valves with multiple tries and the feeney still hisses when I turn it over. It's easy to go oops I turned the wrong dial. Best to do it on a single lobe cam instead of an eight lobe. Usually less money involved.
Or try making some parts you think will fit your engine. Valve cages, valve, cam, piston, connecting rod, even making trial parts can be rewarding. At least to the gear heads.


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## Danny91

Hey again!

Thanks for the replies.
I've had very little time to check out this thread after buying an Audi S2 project, and working on a homemade 3D printer.

Nice links guys. I'm going to use the day to read on them. My final goal will be to make a 5 cylinder engine. But it might be good like you guys are saying with starting off with a 1 and 4 cylinder.

I'm going to have to put the ideas of making an engine on ice to the summer. But i will use the time to read and get the ideas going.

Thanks for the help guys. I'll see ya to the summer

Daniel


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