How is the engine/gearbox assembly mounted to the tub?

[ak07]

I just don't get the thermal expansion "issue"

There are so many other assemblies on the car that are a lot closer to a lot higher temperatures and a lot more stress.

[marcush.]

the difference is carbonfibre is not expanding with temprise,and the engine is for sure one big component.
I agree that similar concerns have to be rised at the engine gearbox interface when a full cf gearbox is in use.

[xpensive]

marcush is correct, in the F1 world of attention to detail, I'd be aghast to learn people like Mike Gascoyne and Newey hadn't paid the interface between a 120 C Aluminium engine and a gasoline filled carbonfibre tub their full attention?

This is precisely where every wheel-force has to be transmitted from front to rear, a clearance or lack of stiffness there
and you can kiss everything else you've done goodbye. Pretty much so from where I'm standing anyway.

[marcush.]

or to put it in a different ways ...maybe some teams experience somewhat unexplainable mismatches of theory and on track performance why? maybe it is something to do with not having looked at the implications of their work enough in detail /ommiting/ignoring major effects of material pairings or not adhering to proven engineering methods.

[xpensive]

I know for certain the John Barnard paid a lot of attention to the torsional stiffness of the TAG V6, that Ferrari went for cast-iron for the V12s for a while, for the same reason. Would they leave the chassis/engine interface to diletants?

[marcush.]

Far from that ....I think it is people like Barnard who spread a lot of detail engineering into F1 ,why else would it be possible in the 70s to design and build a complete racecar with only one guy doing practically all the work with a handful of people doing some drawings..I´d think some areas sort of happened back then ...

[xpensive]

But you could be perfectly right there marcush, as a pre-digital engineer I know precisely how much hands-on knowledge was lost when engineers went from design-engineering to system-engineering in order to keep up with the latest ProE edition.

Hell, some of my designers with a BSc degree don't have a clue how to arrange the dwg display in a fathomable fashion?

Those poor guys in Zweibrucken...they are headed for a treat or two!

[747heavy]

@MArcus

Whats the situation with Carbon-Aluminium Honeycomb components and layed up Aluminium hardoints in said structures, when we consider curing temperatures
of ~120°c. Build in stress?

[marcush.]

747h ...I waited for this question to come really and it had to be asked by you really =D> and I do admit not to have the explanation. for sure the fact cannot be ignored that those two materials have
a spectacular different behaviour over temperature...
Back then Stewart Gp claimed that using aluminium bulkheads was causing their gearbox casings to crack and leak ..(but maybe they suffered more because of the poor bonding faces they were able to realise and maybe also less than perfect bonding process...

As for the aluminium honeycomb sandwiched by carbonfibre skins...the stress over thickness maybe not the big issue obviously but what abaut the behaviour of a 2m board when put in an oven and tempered to 120°C?

by design a flat board would not be able to distort as all forces should equal out but as the temp goes down the alumium should shrink and put the core under considerable tension ,right?
so it maybe it is that you do have to treat the honeycomb core as a cell by cell thing so it is not like a long beam going through the entire length of the 2000 mm composite board which would for sure lead to spectacular failure over a temperature delta of say 120°C?

@exp ...I really know what you are talking about ...working in such an environment with people who know everything about ProE ,Catia V5 R19 but get a set of big eyes when you raise concerns when they are introducing a four point fixation of a component... I also got the impression that most of them do not even have the slightest feel for dimensioning of components....in my view the CAD does not really lead to nicely engineered products...but to multiple compound curves and complicated transformations combined with undercuts that cannot released from the mold as well...not to speak of the simplest errors of dimensions being changed by accident or negligance..on the screen it always looks fine...Maybe i work with the wrong people but this is my experience ,be it at the OEM or the suppliers I worked for ...
They will love you expensive..as you will inevitably just look and pinpoint the key errors in one quick random glimpse at the screen..

[ringo]

Thinking about it, the pins can only be stressed in shear from thermal expansion.
They are set in the engine block and bulk head, restricted from deflecting, so there will be no bending or torsion; only shear in the plane at the boundary of engine block and bulkhead.

Tensile stress from heat is not an issue since the engine is hanging freely or cantilevered from the bulk head. Expansion in the longitudinal/axial direction is free.
It is radial expansion of the engine( x&y )that is the concern. This expansion in these 2 directions only acts on the bolt in the shear plane at the root.

Therefore the bolt/pin, has to be designed for to take that stress since deflection is not possible.

[autogyro]

Difference between a proper engineer (like x) and someone who can use a CAD program. Compounded by being only allowed to design to a tight set of regulations where almost everything has already been done for them.

It is interesting that this thread question is about an important primary issue, how to join the engine to the front of the car and yet no one has yet explained how to do it.

And before any one asks, dont ask me.

[riff_raff]

Whats the situation with Carbon-Aluminium Honeycomb components and layed up Aluminium hardoints in said structures, when we consider curing temperatures
of ~120°c. Build in stress?

747heavy,

That's an excellent point. I don't know about F1 composite tubs, but in aerospace composite structures, metal inserts are almost always titanium. Both for the better CTE match and for the galvanic compatibility. If the adhesive bond line is very long in the fiber direction, a solid insert material with a high CTE mismatch (like aluminum) can end up with high residual bond line shear strains after autoclaving. Most epoxy resins have shear strengths below about 10ksi, so if the bond line is more than a few inches long and the mating parts are stiff, the bond line can easily delaminate after cooling. Since the delamination is internal, and may only be partial, it would easily escape detection.

riff_raff

[marcush.]

riff, thanks for the input there .
do you have any information about thermal expansion of alumium honeycomp structures when they got CF skins?
So could it be a bad idea to combine alumium skinned composite panels with cf skinned ones as they show mainly the behaviour of the skin metal in expansion over temps?

[xpensive]

...
Therefore the bolt/pin, has to be designed for to take that stress since deflection is not possible.

The above is a good xample marcush, when I hear things like that from my PrE-designers, I politely ask them to quantify the load and stress introduced in the bolts in order to keep an engine-block from xpanding when going from 20 to 120C?

[marcush.]

well..something has to give in the end,I suppose.With F1 teams fighting loose wheelnuts all year now I´d rather be surprised to hear that all teams tret something as minor as a tub-engine interface with more than a bit of ovalized boltholes....and live with the constant pinging noises when the temps go down after shutdown.(How does a CF Moncoque sound ?)...I assume the guys doing leMans sportscars are more concerned about this sort of problem..