Vacuum assembly of engines.

[Zynerji]

Just thinking here a bit. What are the thoughts on using lapped "studs" that are assembled in a vacuum instead of bolts? Just having a small (3mm) stud milled on the face of the head with a matching reamed seat milled into the block, and in a deep Torr vacuum, slid together (sealing the negative pressure in the pocket) and then letting the chamber repressurize to atmo.

No hardware = less weight
No rebuilds/sealed engines = no a field access needed
Can also be used to eliminate gaskets by using a tongue and groove approach instead of studs.

Vacuum is cheap. Does anyone have a thought on this?

[CBeck113]

Just thinking here a bit. What are the thoughts on using lapped "studs" that are assembled in a vacuum instead of bolts? Just having a small (3mm) stud milled on the face of the head with a matching reamed seat milled into the block, and in a deep Torr vacuum, slid together (sealing the negative pressure in the pocket) and then letting the chamber repressurize to atmo.

No hardware = less weight
No rebuilds/sealed engines = no a field access needed
Can also be used to eliminate gaskets by using a tongue and groove approach instead of studs.

Vacuum is cheap. Does anyone have a thought on this?

It would be nice, wouldn't it? The problem is that vacuum may be cheap, but manufacturing for a permanent vacuum is ungodly expensive - you need perfect fittings over the entire block and valve head faces, including the studs, or the more "practical" method would be to add a pump to maintain the vacuum, which is heavy and adds the costs you'd like to eliminate. Currently this is impossible for all sport and commercial uses...but who knows what the future will hold?

[roon]

The stud surface area would need to be very large to make this work. If vacuum in a 14psi environment were as strong as you suggest, there would be lighter than air vacuum balloons using known/traditional materials, for dirigibles, installed in airplanes, etc.

[Just_a_fan]

The vacuum studs would need to be large enough to counter the pressure in the cylinder which is "significant". The studs would be bigger than the block. Then there is the machining required for a perfect seal, dealing with differential thermal movement in block and head, dealing with suspension loads - the heads on the Mercedes are structural and doubtless others are too. Then you're going to need a very expensive environment to assemble it, and you can't work on it anywhere other than the factory.

Other than that, a grand plan!

[roon]

More realistically you would need small asymmetrical gravity wells, stacked nano black holes or filaments of neutron star, levitating within the joint voids you propose, to compress the block-head interface.

[Just_a_fan]

If you built the block from neutron star then its own gravity would hold it together! Of course, the engine would have such inertia that it would never be able to move itself...indeed, the track wouldn't be strong enough to support its weight, it would sink in to the ground for tens or even hundreds of metres!

A neutron star is so dense that one teaspoon (5 milliliters) of its material would have a mass over 5.5×10^12 kg (that is 1100 tonnes per 1 nanolitre), about 900 times the mass of the Great Pyramid of Giza.

https://en.wikipedia.org/wiki/Neutron_star

[Zynerji]

This used to be a place of constructive engineering discussion, and not a puke session of sarcasm.

No one has shown why it wouldn't work beside their "gut" feeling. It would be nice to hear the opinions of the real forum contributors.

[Rodak]

Okay, I'll give it a shot. A 1/2" bolt torqued to 60 lb-ft has a clamping force of approximately 7000 lbs. (Technical data, Spaenaur). A 1/2" stud has a surface area of about .196 in²; with air pressure of 14.7 lb/in² there is a clamping force of about 2.88 lb. Hmmmmm, would that work?

[Greg Locock]

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.

[Big Tea]

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?

[Rodak]

"The Hart 415T engine looked similar to the 420R, and they were both 4cylinder 16valve engines, but the 415T was another ground up development by Hart, a 1.5ltr purpose built turbo engine that was actually a monobloc, ie the head and block are cast as one piece- No head join = No head gasket to blow!"

From http://www.stavtech.co.uk/home/ayrton-s ... -hart-415t

[Just_a_fan]

This used to be a place of constructive engineering discussion, and not a puke session of sarcasm.

No one has shown why it wouldn't work beside their "gut" feeling. It would be nice to hear the opinions of the real forum contributors.

My first post lists a whole lot of issues why, from an engineering point of view, it wouldn't work.

Vacuum gives a maximum of 14.7psi pressure differential. Your studs and sockets would need to be huge (as I said, bigger than the block) to give sufficient clamping force to overcome the pressure in the cylinder during combustion. That's the obvious first issue with it. Then there are the details such as how to make a reliable seal. How to deal with suspension loads on top of the combustion forces. How to work on the engine at the track. Etc. Answer those issues with engineering answers and the discussion might continue further.

[Just_a_fan]

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?

Much of the work in improving the engine involves playing with the head and the top of the combustion chamber. Easier and cheaper to have separate castings in that case as you can leave the block alone and just cast new heads.

[dans79]

This used to be a place of constructive engineering discussion, and not a puke session of sarcasm.

No one has shown why it wouldn't work beside their "gut" feeling. It would be nice to hear the opinions of the real forum contributors.

That's because this only requires common physics & math knowledge to know it won't work.

A perfect vacuum only yields 14.7 psi of force. Multiply that by the cross sectional area of a stud in in^2 to get the clamping force of a single stud. Multiply that by the number of studs and you will have total force.

[dans79]

Much of the work in improving the engine involves playing with the head and the top of the combustion chamber. Easier and cheaper to have separate castings in that case as you can leave the block alone and just cast new heads.

Not to mention it would be next to impossible to machine the inside of a cylinder head using standard techniques.