Question...

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minh-thanh

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Question...
I'm probably the one asking the most questions on this forum
I seem to have read somewhere that there is a relationship between the sizes as shown in the picture
Can anyone help me understand more ?
Thank you !
And how should I rename this topic to match its meaning? that will make it easier for others to find if they are in need of information..

GreenTwin

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HMEM Supporting Member
The total travel of the crosshead equals 2xW.

The piston rod needs to be long enough for the rod end to clear the gland on the bottom cylinder head.

I think the shorter H is in length, the larger the angle between W and H.

As H becomes infinitely long, I think the rod angle approaches zero.

A large rod angle makes for a rougher running engine ?

These are my guesses.
The folks who know engine design will have to check me on all of this.

Edit:
That is a really nice looking engine !
.

Nikhil Bhale

Well-Known Member
Hi,

W is crank throw; one half of stroke,
H is Con rod length,
L is the piston rod length. it is stroke + piston length + TDC clearance +BDC clearance + clearance between rod and gland.
I am assuming this engine is similar to modern 2 stroke marine engine

Regards

Nikhil

minh-thanh

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@Nikhil Bhale
I know that
What I'm looking for is: for example, what should be the minimum con rod length compared to half the stroke? if it's too short, the pressure on the crosshead is huge
@GreenTwin
Edit:
That is a really nice looking engine !
.
Yes, it's a really nice engine and also one of the engines I'm designing

Andrew Stroud

Member
I have seen the suggestion that the connecting rod is 2.25 - 2.5 x the stroke (2W on your drawing) for a slow speed crosshead engine. L is determined by 2W + the needed clearances as mentioned previously so no need to include in any relationship between conrod and stroke.

minh-thanh

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I have seen the suggestion that the connecting rod is 2.25 - 2.5 x the stroke (2W on your drawing) for a slow speed crosshead engine. L is determined by 2W + the needed clearances as mentioned previously so no need to include in any relationship between conrod and stroke.
Thank you !

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