Vacuum assembly of engines.

[Jolle]

Just 3D print the whole thing...

[Zynerji]

Just 3D print the whole thing...

I'm literally working on that as we speak... 4 years of effort has me close to an aluminum electrospinning 3d printer at 2nm resolution. Printing engine components is exactly why I started designing and building it.

Actually, since my printer has to be inside a vacuum bell jar, that is where the whole idea of vacuum assembly came from!

[Zynerji]

Cylinder head bolts have a tensile strength of about 1500 MPa. So a 12mm bolt (WAG) has about 75mm^2 of usable section, that is, it exerts an axial force of about 1500E6*75E-6 N, about 10 tons, of which perhaps 20% is actual fluctuating load, so call it 2 tons - the rest is friction and preload. 2 tons of vacuum would need an area of 1/5 of a square metre, ie a dowel 500 mm across. To replace one bolt.

Would 200 Tons of vacuum make the dowel 5mm across? The vacuum I use is 10^-8 mbar. I dont know how to calc the force from it. I could see a spherical dimple in the end of the stud if increasing surface area for the vacuum to act upon has any positive clamping effect, as well as the dowel seat having a spherical bottom. I guess that if you machined it correctly, as the 2 pieces are put together, it would leave a perfectly spherical chamber in the dowel hole that would contain a deep Torr vacuum.

Also, the concerns over machining the lapped faces shouldn't be a hindrance, as hobby rc engines have lapped pistons that would be very similar to what I am picturing, and the wouldn't be moving, so longevity should not be a large factor.

[63l8qrrfy6]

don't design any engines pls

[Zynerji]

don't design any engines pls

Is there a reason that you say that? I don't see any correlating factors in this thread to support such a statement.

When working on my printer, the vacuum part surprised me a bit. It then led me to think about using it as a fastener. I posted to ask the mathmetizers on the forum of it was even a realistic possibility.

I'm sorry that you don't have any real answers, just backhanded insults.

[63l8qrrfy6]

F=PA where A is the projected area. Increasing the surface area by machining a concave feature has no effect as the projected area remains constant.
You kinda need to know these things to design engines. Or bolts for that matter.

[Zynerji]

F=PA where A is the projected area. Increasing the surface area by machining a concave feature has no effect as the projected area remains constant.
You kinda need to know these things to design engines. Or bolts for that matter.

From my reading and understanding, the pulling force of a vacuum has surface area interaction. There is a point that the vacuum will start pulling apart the surface (sublimation). That was the part that I thought might be the most difficult, as if you lowered the contained vacuum enough, the heat cycle of the engine might literally vaporize the material in the cavity.

[63l8qrrfy6]

yes it is possible if you use peperami for dowels

[Zynerji]

yes it is possible if you use peperami for dowels

[xxChrisxx]

Would 200 Tons of vacuum make the dowel 5mm across? The vacuum I use is 10^-8 mbar.

What do you think you mean by '200 tons of vacuum'?

What's the maximum possible pressure differential you can achieve by making a vacuum on earth?

[Rodak]

Zynerji, you're a hoot!!!! Just don't run that engine above sea level!!! Seriously, force from an absolute vacuum is the pressure of the atmosphere where the vacuum is pulled. If you took your engine into space there would be no vacuum force holding it together.

[Zynerji]

Zynerji, you're a hoot!!!! Just don't run that engine above sea level!!! Seriously, force from an absolute vacuum is the pressure of the atmosphere where the vacuum is pulled. If you took your engine into space there would be no vacuum force holding it together.

Why would I take it into space?

[xxChrisxx]

Zynerji, you're a hoot!!!! Just don't run that engine above sea level!!! Seriously, force from an absolute vacuum is the pressure of the atmosphere where the vacuum is pulled. If you took your engine into space there would be no vacuum force holding it together.

Why would I take it into space?

I'm afraid that it wasn't meant to be taken literally. It was clearly posed ironically to highlight the fundamental flaw in your thinking that a vacuum sucks things together.

Quite clever really.

[roon]

Which is why I posted what I did. If you want an adhesive force of sufficient tenacity, employ local gravity wells. Not entirely feasible mind you.

Magnetism is another option, but limited by weight and size, as with the vacuum-dowel proposal. Velcro likely not strong enough...

Adhesives could be an option. If there's enough surface area at the head/block interface to provide a suitable bond, you might be able to have your cake and eat it too, in terms of machining access and gasket-less assembly. Welding is likely stronger though.

I image within the 100+ years of the modern reciprocating internal combustion engine, someone's welded a block and head together.

[roon]

The original point, that of not having head bolts etc is still valid though isn't it?

How come, with modern techniques, F1 engines still have a separate head?
Is it due to the access to the valve area, and setting up clearance, or is there a good reason for having a lid that comes off?

The depth of the cylinder of a F1 engine is small, so I doubt it would be due to not having tooling or access angles to make the valve seats etc, so other than maybe casting in cooling passageways, is there a good reason other than tradition?

One of the latter, unused NA engines from BMW had the heads and block cast as one. They did get around the machining limitations. But head gaskets and bolts don't seem problematic for F1, so it's likely not worth the extra attention.

In machining and quality-control, mounting tools upon extensions will cost you precision. An analogy would be writing your signature with a pen, and writing your signature with the same pen mounted on the end of a ruler. The artfulness of your signature may suffer.