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Single cylinder engine

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John Rudd:
I'm embarking on a single cylider engine designed to run off petrol...
So far my specs are:
Bore               1 inch
Stroke            1 inch
Piston length   1 inch

Compression ratio Yet to be determined, around 5:1 or as advised by the group.

Cylinder length ermm I think it needs to be around 2 inch Could someone verify this for me please?

Length of conrod...ermm again tbd..I'm guessing its a function of stroke..Could someone offer guidance on this too please?

So far, I have my piston blank machined to diameter, going with 2 ci rings, cast iron liner with an aluminium barrel/cylinder and aluminium cyl head.

Crank maybe overhung or I may go for a fully supported unit and a bolted big end cap.

Need to figure out lubrication too..  :-\

Any comments or offerings appreciated  ;)

David Jupp:
Con rod will have to be long enough that piston skirt doesn't foul the crank or balance weights at BDC.  The detail of your crank design will influence the minimum length quite a bit.  You can also cut an arc out of the piston skirt to clear crank parts.  Height of gudgeon pin in piston will have some influence.

Sounds like a job for paper/scissors, or parametric CAD.

Others can probably give more precise guidance - my comments are only based on having stripped a few car and lawnmower engines in my time.

John Rudd:

--- Quote from: David Jupp on March 17, 2012, 09:07:56 AM ---
Sounds like a job for paper/scissors, or parametric CAD.

--- End quote ---
Dave cheers for that..
Yeah I guess so...Dont have CAD or the time to learn it  :Doh: ( nor the inclination  :coffee: )

Spurry:
John

I'm pleased that you are not idling your time away. :thumbup:

I just did a quick sketch to see what was involved. This is a metric drawing, so bore is 25, stroke is 25. The blue piston is TDC, red in the middle at 3 o'clock and 9 o'clock and the black BDC. So that the crank clears the bottom of the liner a con rod length of about 43 should work.

I have never designed an engine, so would be inclined to crib the important data from a working version.

Pete

John Rudd:
Hi Pete,

Well the weather hasnt been too great here for any flying... :palm:

So I thought I'd make use of the time to do something constructive and nowt to do with aeroplanes :)

Although I've a couple of steam engines on the go, I thought I'd try something different to stop boredom setting in..

The sketch you provided is great and many thanks for it....I'll probably go for a con rod length of 45mm or whatever that is in Imperial just to keep things neat.. :dremel:

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