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Crankcase Casting wall thickness

Crankcase Casting wall thickness

(OP)
Hello Everyone,

I am new to this forum and design field as well.

How to calculate the wall thickness of crankcase or cylinder head casting.

Even cylinder head or crankcase design related document/web link will be appreciated.

I have searched on internet but could not found anything.

Thank You.

RE: Crankcase Casting wall thickness

The website at sae.org sells a crapload of technical papers, handbooks, and enthusiast books.
Bring your wallet.

The information you seek may not be available, even there, since there are commercial incentives to reveal nothing, or even to reveal misleading information.

You could probably learn a lot by sectioning and reverse engineering an existing engine in which you are interested.
You will probably need a big power hacksaw.

Mike Halloran
Pembroke Pines, FL, USA

RE: Crankcase Casting wall thickness

Do you want to calculate the cast wall thickness required for a crankcase or cylinder head structure? Or do you want to know the minimum practical wall thickness that can be achieved with conventional crankcase or cylinder head casting techniques?

RE: Crankcase Casting wall thickness

(OP)
Yes,i want to calculate the cast wall thickness required for a crankcase or cylinder head structure.
Is there any design formulas?

RE: Crankcase Casting wall thickness

Stress analysis (FEM) - considering both stress and allowable deflection
Vibration analysis (the shape and thickness of the crankcase is a factor in how much noise the engine makes)
Thermal analysis - avoiding large changes in thickness which could be fracture sites
Manufacturability - and in the case of sand casting, allowing for core shifting
And a healthy dose of experience.

RE: Crankcase Casting wall thickness

It will depend on many things, application for one, and HP rating. And of course the material you plan to use as well.
FEA yeah, but in the old days it was also and still can be trial and error, using stress coat and strain gauges.
Its not just a use this thickness or that thickness, its also what weight limits do you have and there maybe ribbing to add strength etc. I don't think there are any said calculations to find the perfect crankcase cross section. Way too many variables.

RE: Crankcase Casting wall thickness

From what I've seen at secondhand, the castings are as thin as can be cast (if they are iron) and then webs are added as needed for all the various performance criteria. Aluminium blocks tend to be somewhat thicker than the minimum feasible casting thickness, which puzzles me.

However, I would point out that specifically with noise reduction, and I suspect torsional stiffness, some analysis shows that thin wall+webs is a worse solution than the same material spread out as a uniform plate.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

RE: Crankcase Casting wall thickness

2
Having cut up and inspected pretty much every cylinder head from Briggs and Strattons to very expensive F1 items for analysis I'd say make everything about 5mm thick, the deck faces 8mm on the heads, and 10mm on the blocks. The combustion chamber roof 8mm, but make sure you have ample coolant flow internally around the plug counterbore. This can be tricky in terms of making the coolant gallery core there so keep soluble ceramic inserts in mind and also cross drilling from the exhaust manifold side. Watch the areas where the valve guides will live as these will cool after the port roof walls and may cause hot tears - ideally your risers will sit ontop of these for directional solidification but may be impossible chop off once out of the sand. Make the bit where you bolt the sump pan to 25mm wide and 20mm high and dont spare the fillets - the pattern makers/CPS Layer'up'er guys will thank you in time. All of the above dimensions are pretty much the same for a 1L 50hp engine to a 950hp v10 F1 engine so I honestly think calculations are pointless at this point - I'm sure someone still does them, but pointless all the same - I think. As for coolant flow simulation, this is normally done with casting number one - sensors buried in near plugs and the engine ran - the headgasket coolant holes are then enlarged or decreased for more or less flow depending. Aluminium is a good conductor as is the coolant plus its going pretty fast so I don't think that's super science either from what Ive seen. If you dont have a head gasket for tuning the flow, then do what they do in F1 where they have very expensive flow and thermal sim packages - drill and drill again and fit flow restrictors where you need them.

As mentioned allow for core shift on the ports - the tighter you want the core prints, the more sand that will be scrubbed off when fitting cores - this will have to be flushed out into the risers or will cause you trouble. If you make them looser they will be easier fit, but may move or float until they contact core print registration.

If you are diecasting the blocks then you can go down to 4mm in most areas, but remember to use far less machining allowance since the strength of diecastings is mainly in the surface skin due to the chilling effect of the permanent steel mould. If you machine off too much of this chilled skin bad things will happen.

Brian,

(have put 200 heads + through a 40yr old power hacksaw and swore as many times more with mis-filled complex prototype CPS castings)



RE: Crankcase Casting wall thickness

"Aluminium blocks tend to be somewhat thicker than the minimum feasible casting thickness,"

Greg, I think if you went down to minimum feasible thickness, you would be denting the aluminium with any wayward blow from a hammer or even a spanner (wrench).

je suis charlie

RE: Crankcase Casting wall thickness

I would guess that Al blocks are stiffness limited, give that the modulus is 1/3 or a Fe based alloy.
Thin walls and ribs may get you the strength and rigidity that is needed, but in some designs the thin panels have vibrated in the range that can be heard, and when the engine gets to a speed to excite that the noise can be very bad.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

RE: Crankcase Casting wall thickness

I think even on a lawn mower engine .157 is fairly thin cross section. 4mm
My inaccurate check on a cast iron block Automotive gas engine. I'd say any minimum areas are maybe .25 thick that would be coolant jacket to outside. Case webs ? .375 or more in thin areas. Deck thickness over .5, Al head combustion chamber .4 to deck surface, Ports to outside wall about .22 . If manufactures released prints, a study of that would be helpful.
In the post above an F1 engine is going to be a trade off for weight and strength, and does not represent a very durable long lasting design, how many races did that particular engine have to last?

RE: Crankcase Casting wall thickness

(OP)
thank you.
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