Ic engine design help

[bullpeters]

Ok, planning on building an ic engine. I have a small amount experience and have made a compressed air engine.
And it worked.
I am planning on 25mm bore and stroke, cast iron cylinder with AL piston, head and crank.
Timing belt and cams up on top.

I have no firm plan other than bore and stroke. Figure I could make it up as I go along. I realize this is not optimal but it's what I want to do.
So
Is it going to work?
Piston rings?? Don't want to make them, can I buy them??
Size of the valves??
Any other helpful ideas would be very good
Michael

 

[bullpeters]

Oh, con rod length? What's optimal
I don't plan on running the engine long periods. Just to show it works

 

[cfellows]

Ok, planning on building an ic engine. I have a small amount experience and have made a compressed air engine.
And it worked.
I am planning on 25mm bore and stroke, cast iron cylinder with AL piston, head and crank.
Timing belt and cams up on top.

I have no firm plan other than bore and stroke. Figure I could make it up as I go along. I realize this is not optimal but it's what I want to do.
So
Is it going to work?
Piston rings?? Don't want to make them, can I buy them??
Size of the valves??
Any other helpful ideas would be very good
Michael

You can buy piston rings from several sources, but I've had pretty good luck using plain O-rings. Viton is recommended but I've used regular plumbing o-rings which are probably PVC. For a 25mm bore, I'd recommend valves with a 9mm OD although you might get by with smaller. Make sure the connecting rod is long enough that it doesn't collide with the sides of the cylinder at mid stroke. You might want to make a 2 dimensional model out of wood to try out different lengths or model it in CAD.

Chuck

Edit: Even if you want to use your own design, it wouldn't hurt to look at some other designs just to get ideas and to see things that might wind up being important. The Webster engine comes to mind as well as some of Jan Ridders' designs.

 

[stevehuckss396]

I am planning on 25mm bore and stroke, cast iron cylinder with AL piston, head and crank.

Piston rings?? Don't want to make them, can I buy them??

Size of the valves??

From reading this it appears that the head and crank will be cast iron. Head is fine but you might want to make the crank using 1144 stress proof steel.

Yes you can purchase rings. You might have to go to a 1 inch bore instead of the 25mm http://www.deboltmachine.com/id4.html

a 10mm valve would fit with no trouble with a 6mm or 1/4-32 spark plug

 

[bullpeters]

Thanks
Aluminium head and piston
I thought drill rod for valves and whatever I could find for con rod.
I have been looking at some engines to get a feel for the dimensions
Thanks for the help.
I will post some pics

 

[lohring]

I would seriously consider a two stroke engine for your first effort. It's hard enough making the basic engine parts without tackling a valve system the first time. Take a look at http://modelenginenews.org/ under engines - plans. The Hallum 9.5 cc engine is a good place to start since it has a piston port and requires only straightforward machining. I would consider modifying the design to glow ignition with standard model fuels and a one piece aluminum piston with rings. Making the piston and rings are enough of a challenge. You can buy needle valve assemblies and a separate fuel tank. On top of everything, the engine will have more power than a similarly sized four stroke. I, and the other members here can help with material selection and machining methods.

Lohring Miller
http://modelenginenews.org/plans/hallum95_bp.jpg

 

[kadora]

I have glued rough 3D paper model of my first engine to check if there is enough room for cam gears , valves , rocker arms , screws , wall thickness and so on. /in case you are not friend with CAD - like me/
On Hobby king web page you can buy liners , pistons , rings , carbs. for
reasonable prices. /RC engine spares/ highly recommended to use them.
For first time model go for minimum 10 ccm capacity air cooled single glow.
From my point of view is better for first engine design 4 stroke /more complicated but easier to bring to life/.
Keep us informed about your progress .
Kadora

 

[bullpeters]

Thank you all for the advice. I will stick with the four stroke. Its more a chance to expand my skills (minimal at present ), than anything else. I can do all the basic stuff but cams and valves would be a nice challenge. I have made a start and will post some pictures.
Thanks

 

[bullpeters]

I have found some 34mm of rings from lawn mower shop. My plan is to tun up a 34mm pisto, longer than I need it to be, then bore the cylinder to an "almost" fit, hone cylinder till it's a fight fit, then turn down the piston to the correct size. That way I won't have to measure the bore. I don't think I could measure the bore accurately.
I then hope to work out the stroke, based on 8:1 compresion, and then the con rod lengthy. That should keep me going for a while
Any suggestions greatly appreciated as I am to green to burn