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

[riff_raff]

ak07,

Deflections in the cylinder head and block structures with a stressed engine chassis are a big concern. Misalignment of block main bearing bores, cylinder bores going out-of-round, and misalignment of cam journals in the heads are all problems with an engine subjected to high chassis loads.

The problem also gets worse with longer engines. Many years ago when Ferrari first ran their N/A 3.5L V12, they made the blocks from thin wall cast iron to increase their stiffness.

riff_raff

[ak07]

Yes, I agree Riff_Raff. My point was that the torsional forces concerning the way the tub and motor are mounted together is less of a concern than the motor iself, as well as the gearbox/tub.

[xpensive]

Looking at those rather thin plate-like mountings of the old Cosworth V8 above, it seems a perfect mounting of the engine to take the half millimeter or so of thermal xpoansion, picture this;

The mounting at the lower end of the engine is totally solid, which incidentally cares for most of the tension loads,
while those 45 degree plates have an easy time to cope, or am I again wrong with my feel for a statical analysis?

[marcush.]

Having 6!mounting points is going to NEED some attachment with tolerance ,right?
so for sure only 3 of those can be close tolerance unless you want your mechanics
swearing at the racetrack or at the workshop for the components never fitting slotting in without issues ...
You say the top mounts are simply so weak in yz plane that any thermal mismatch is just soaked up easily But still you got no issues with a remarked step in torsional and bending stiffness in the mounting interface ?
In my view ,if the parts are in itself not designed to allow for the misalignment ,you will for sure get a change in installation stiffness over temperature ,don´t you think so?

[xpensive]

Was fur ein gutes morgen marcush, starting the day with a technical riddle.

If I had no knowledge of the application whatsoever, which is pretty close to the truth actually, I'd gone this way;

-I would have decided on a single position of reference begin with, in this case it would have been the very lowest position of the inteface between engine and tub.

- I should probably had figured out that for obvious reasons, I need two more positions for stability in the Y-Z plane.

- I would probably have used the latter two to care for thermal xpansion.

Now, having boiled this down far enough, would the engineer accomplish that?

[marcush.]

exactly my line of thought that is .
For sure it would be the next step to map the dimensions of the engine from the lowest storage temperature up to maximum operating temp ,preferably actually running the component ,as the thermal map of the engine will in no ways show a constant heat distribution at the front face...

Of course it would as well be quite interesting to as well look at excitation of the mounting points over revs and temps as well just to know what to expect in terms of influence from the engine to the system aswell..

From these findings it should be possible to exactly define how much grow in which direction you need to supply in your upper mounts...and maybe have second thought of how to erase the vibs that might cut your engine mounts or whatever in two halves..

[xpensive]

Genau.

If you imagine the static position at six a'clock, wouldn't two, both outwardly flexible positions, at ten and two a'clock make for xcellent torsional rigidiry?

[marcush.]

Genau.

If you imagine the static position at six a'clock, wouldn't two, both outwardly flexible positions, at ten and two a'clock make for xcellent torsional rigidiry?

To me that would be the solution ,why not build in property to have misalignment in bolt orientation this would really make for a nice installation?
Would this be a flexure like we see it in suspension mounts or something like a bushed axle to which you bold the engine ?

[xpensive]

Flextures, or simply double-bending plate-looking things, at ten and two a'clock, like on the Cosworth seems like a start.

A spherical-face bolt, some 50 mm long, should have no problems accommodating 0.5 mm of movement, 0.6 degrrees only?

[ak07]

I can't speak for F1, but I can speak for the Dallara/Honda used in the IndyCar Series. I worked on an IndyCar team for nearly two years, before deciding that I wanted to get my engineering degree....Anyways...

....It is often fairly difficult to mount-up the engine. There is a lot of swearing most of the time. It isn't extremely bad, but sometimes can seem like there is no way to get it aligned. Then again, other times...you laugh because she'll slide right on. Anyways, there's really no other way at least as far as the IndyCar is concerned. The entire rear bulkhead comes off, the studs are just around the outside of a hollow space for the fuel cell.

[riff_raff]

Transferring shear loads thru pins can be problematic if there are more than 2 pins. In order to transfer shear loads, a pin must have a zero clearance fit in its bore. Getting 6 pins to fit perfectly in 6 bores, with interchangeable parts, is almost impossible. If pins are used, they're likely for location only and not for taking shear loads.

Transferring shear loads at the engine/tub interface by clamped friction might be possible though. If one assumes the clamping preload per stud is something like 12,000lbf, the interface friction coeff. is around 0.30 (dry metal on dry metal), and there are 6 studs, then the normal shear capability of the joint is 21,600lbf. And if the studs are located on a pitch circle roughly equivalent to 18 inch diameter, then the torsional moment capability of the joint would be 16,200 ft-lb.

Would that be good enough for an F1 chassis?

riff_raff

[ringo]

Hello posters,
Please accompany your thoughts with some sketches. I would like to see what you are talking about.
Is it possible that the pins have pilots on the tips?

Also another question related to the topic,how are these pins/studs staked into the tub?
Is there a metalic frame embeded into the carbon tub, similar to the aluminum frame we usually see for the front suspension?

[xpensive]

In situations where thermal xpansion is an issue, as I would think this topic is all about, you would typically settle for one fixed position, while leaving one or more to care for the flexing, depending on the number of dimensions involved?

[747heavy]

Also another question related to the topic,how are these pins/studs staked into the tub?
Is there a metalic frame embeded into the carbon tub, similar to the aluminum frame we usually see for the front suspension?

aluminium insert/hardpoint inserted into the tub during layup
similar to inserts/hardpoints to mount suspension parts



what would be/is the temperature difference between the engine/frontface and the area of the tub where the engine is mounted to?

[ringo]

It should not be much different, maybe about equal at the interface.
What i think though, is that since the engines are water cooled, water jackets being on the outside of the cylinders, it's likely the external parts of the engine wont run much hotter than the water.