VW engine modellling

[jediali]

I play about with solidworks a lot and was wondering what you thought about my approach to the VW W12 and whether you lot have tried this. I was playing about with the stroke to bore ratio and found that pistons interfiered in the 15 degree vee angle banks once it got towards square.

AS you probably know this idea by VW saves space but makes cooling difficult. The conrods have to be thin as well. The actual W12 crankshaft has splayed cranpins but i balanced my crank this way and achieved 78% reciprocating balance at 5800rpm.

[henk4]

the original W12 engine as used in the VW prototype has a borexstroke of 84x90, are you looking at a shorter stroke and wider bore?

[jediali]

i have a stroke of 90mm as you said (this changed little as it went from phaeton-A8-bentley) and a 72 mm bore. any more and the pistons colided in my model.

[henk4]

Originally Posted by jediali

i have a stroke of 90mm as you said (this changed little as it went from phaeton-A8-bentley) and a 72 mm bore. any more and the pistons colided in my model.

ah, but you said in your first post that pistons collided when the engine went almost square=equal bore and stroke...
Generally the stroke is the critical measurement as it defines the revs (piston speed) so I do not really understand why you reduce the engine volume by reducing the bore.

[jediali]

Well the balancing is of less importance to me. I first ignored the specifications and made the cranshaft to fit the stroke and left it like that because the crankshaft is complicated to redesign. I then gave it the largest bore i could to make it work. The capacity is irelevant at this point. The bore is easir to vary as the piston is easier to modify.

I agree that reducing the stroke reduces the piston velocity hence enhancing revability. Also if you reduce the stroke the pistons get closer and closer to the crankshaft thus causing piston collision in the narrow combined cylinder bank - the further the pistons stroke volume is from crank centre the more clearance each cylinder has.

[henk4]

I agree mostly with what you are saying, but I can't help wondering what you are aiming at? Do you want to improve the engine efficiency without change the engine volume? Or are you looking at the optimal configuration for a W12 engine and if so, what is the direction you are thinking?
(I am an economist an not an engineer )

[jediali]

Its good to have someone thinking on my lines hnek4!

My ultimate aim was to use solidworks CosmosMotion (TM) to evalaute balance in the end. My thesis was on F1 crankshaft balancing. Also i want to determine crankshaft stresses.ie optmise material and its distribution. I do this through finite element analysis on my PC. I thought this might be too deep and left it out of my introduction. However i hoped my work could inspire others here visually, particuly thoses who do not understand VW's narrowangle vee engines.

p.s. i just said that balancing is less imporatnt to me in a previous post but that isnt true

[NSXType-R]

Cool stuff.

What happens if you made an engine like this?

Imagine if you stacked a couple of airplane rotary engines.

Or, in a simpler way, you put two or more W engines at the crankshaft together.

Imagine the possibilities!

[henk4]

Originally Posted by jediali

However i hoped my work could inspire others here visually, particuly thoses who do not understand VW's narrowangle vee engines.

When I was a student we had the Lancia V4 engines with a 13 degree angle

[jediali]

In relation to my last post an image of a V10 crank stress test i have done. This cranshaft has stroke of 39.89mm as the F1 one i based it on.

[Cyco]

Have you considered the possibilities of not needing to have any of the pistons in the same plane allows by the introduction of solenoid valves and the subsequent removal of cam shafts?

Would the packaging possibilities outweigh the difficulty in balance, or could some "wild" configurations be made to work quite well?

[jediali]

Your idea of camshaft-less engine is innovative but engine balance also has its implications. For exampe the w12 relies on the fact that a VR6 (half a W12) replicates a straight 6 and is balanced, therefore the W12 inherits the natural balance of V12 - a smooth engine requiring no external balance at all. If you introduce new planes you would have to balance each and every plene individually, that would be a complication and a half!

[jediali]

Originally Posted by NSXType-R

Cool stuff.

What happens if you made an engine like this?

Imagine if you stacked a couple of airplane rotary engines.

Or, in a simpler way, you put two or more W engines at the crankshaft together.

Imagine the possibilities!

Nice to see some imagination! i think we should appraoch engine design standng as far back as possible so not to be influenced ny current accepted trends. In answering your questions:

1)airplane rotary engines have done what your taking about but jet engines become more efficient in that era.
2) There are only so many conrods that can connect to a given length of crankshaft. See veyron W16 as an example of lots of conrods powering a short crankshaft. so a WW24 (think about it) engine would be pretty crowded.

The possibilities are certainly there though!

[henk4]

Originally Posted by jediali

1)airplane rotary engines (wankels i presume) are very flexible and you could just have one big long line of rotors probably if you want extra capacity without creating to much problems.

No, airplane "star" engines are normal piston engines...

[jediali]

Originally Posted by henk4

No, airplane "star" engines are normal piston engines...

i just realised and edited it, thks