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

[marcush.]

with system pressure restricted to 3.5bar we can assume water temperature is somewhere above 120°C also oil temperature should be above 130 ...Cylinder head temps are likely to exceed even this.I really can´t believe the tub or mounting face is seeing anything like this ,especially when clad with all the expensive gold foil.And more than likely the engine will be installed when cold or nearly cold so there is a difference .
As exp already pointed out for the head mounts you should provide tolerance to provide scope for expansion in the right direction this should do the trick without compromising torsional and bending rigiditiy.
I understand its not a huge difference but there is something in it and it will have more than likely an effect on the behaviour of the components or system..

[747heavy]

I agree Marcus, no doubt there is a difference due to the difference in CTE to be
accounted for. But as you are normally the precise and nitpicky one (no offence intended), I thought it would be worth to ask the question. As a delta T of 100-120 K seems a bit high to me.
It does not change the basic underlying question/problem, just it´s magnitude a bit.

This is said to be an F1 engine mount.
I believe the lower (central) one. (but I´m not 100% sure if this is a corect assessment).
As Xpensive has ask the question before, it may provides some more food for thought.

[xpensive]

Nice pic Jumbo, looks like casting-porn to me, although I fail to visualize its xact position between engine and tub?

As for thermal xpansion, Alu is 23 microns per K and meter, why a 400 mm distance will become 0.92 mm longer at 100 D-K.

The more I look at that old Cosworth installation, the more ingenious it strikes me. Imagine one fixed position at 0600 and two flexible blade mountings at 1030 and 1330 respectively. Said blades can individually flex at 45 degrees, but together with the fixed mount, the three of them make for a very stiff installation in every which direction.

Neat!

[747heavy]

I agree X, that the old Cosworth installation is a neat solution to the problem.
When we have a look at the Indycar photo posted, it looks like one stud/bolt at 6´o clock and the other at ~10 11 & 1 2 making it 5 fixings in total.
What crossed my mind, was the location of the oil tank shown on the new Coaworth F1 engine, and some other F1 engines as well.
To me it looks like, that the rear face of the monocoque has a large cut out in the centre for the oiltank.(opposed to the Indycar rear bulkhead which seems to be flat).

If this is the case (and I´m not 100% sure about it, just a thought), I was wondering if they use part of the possible flex in the "U-section" to account for some of the stress due to the expansion of the fixing points at the cylinder head
in lateral/diagonal direction.

While I agree with your calculation, I think it represents the worse case and a
lower delta T would lead to a lower general expansion.
On another note, I think the CTE of composites changes with fibre direction (can be tailordered), so there is maybe a small provision to get a slightly better ratio then the one used in the calculation.
But overall the problem still exists - no doubt about it.

[747heavy]

four stud/bolt mounting on this BMW-Sauber F1,
also note the U-section talked about before.

[ringo]

The temp diff wont be 100 degrees since there is a shared interface.
The pins will conduct heat from the engine and transfer the heat to the bulkhead. The gold foil seems to be more for radiative heat transfer than conductive. There will be a difference, but i don't think the thermal resistance of the pins are so high they will be much colder than the engine.
I don't think there is a drastic temperature difference that forcing the engine of bulkhead to be fixed would result in a part failure.

That BMW pic is amazing by the way, the pins are so thin. Must be steel alloy and not aluminum.

[xpensive]

@ Jumbo;
Interesting picture of the BMW, if the engine is bolted directly to those skinny-looking studs sticking out from the tub,
perhaps the length of the upper ones are intended to take up the thermal xpansion directly? If the bracket holes in the valve-covers give a clearance to the studs, while the nuts have a spherical seat?

I fail to identify the U-shaped thing however?

[747heavy]

imagine to look from above or below towards the chassis tub,
the two points where the studs are located are not connected
in a straight line.
the chassis has a space in which the oiltank goes.



compare the rear bulkhead of the Sauber with the IndyCar posted a few pages
before.
I like your spherical bolt face idea.
Maybe there is a spherical bearing in the cylinder head brackets.

[marcush.]

we see those loooong studs poking out of the rear face of the tub...

to me this is creating a means of being able to have enough degree of freedom to get the studs into the engine at all temps and as they are not all the same length you will be able to work one pair at a time ...unfortunatelly the longer ones are those on the top of the engine where you get most of the delta...which could lead to chafing on the lower ones at certain temps.
I wonder if a cicular svivelling of the long
studs at the tub face would be much helpful as the engine supplied mounting is a very long paralell bore ...so you will need a quite a bit of tolerance to be able to align it ,the circular movement not helping at all .It would never work the other ways round (having to start a bolt into a thread in the tub ..).Exp suggesting a dome shaped nut face ,as I understand it,could be on something here,but I have to admit the idea of taking up the expansion by a flexure type mount is a lot more pleasing my little world of thoughts.

The thermal conductivity is not the issue here as well because we are not talking about a possible thermal mismatch in the stud /bore interface but a difference in thermal expansion of the tub (which should be cool ,a lot cooler thank the engine)
and the engine or do i miss something important here? .The big question is will it ,apart from being not nicely engineered ,have an effect of the system behaviour in terms of stiffness over engine temps ?that one might be answered by Dave perhaps ,who might be one of the guys who does a lot of
rig work and I certainly know that some teams experience difficulty to translate Rig findings to the track or fail to reproduce stiffness issues of the chassis on the rig (are these tests done with the engine preheated up to running temps or is the thing tested as cols as it is? A Magnesium bellhousing would make me suspecious when doing rigtesting in cold condition)
-edited post to show more respect to other forum members reasonings - thanks for the little hint ..

[747heavy]

seeing that the oiltank sits inbetween the the mounting points in the tub, and keeping in mind, that the tub is Aluminium honeycomb, I think it is not unreasonable to assume that we have ~50-60°C in this area, which brings our delta T to about 60-70°C, leaving us with a mismatch of ~ 0.5 mm. not sure if this poses such a big problem for installation, which normally will not be done when the system is hot.

DaveW is the man to ask, but I have never seen or heard, that someone has tested in hot conditions on a 4/7-poster (it´s surely not the normal modus operandi).
But never say never, stranger things have been done.

[marcush.]

I come to the conclusion that this may be an interesting topic but it seems that people have somehow concluded there is not much in it and accept a little bit of strain in that area preferring not to look deeper into it.along the lines of never had a problem (better wording would be to say never had a problem we were able to trace back towards the delta t of those components.But as one of our forum members already mentioned for whatever reason sometimes the engine just slides in when on other occasions it is a dog to install...hm.

btw 747h -the part pictured in your post ...sure this is an engine mount? to me the thing looks like an upright sitting on the hub face...even more so when looking at the computer screen at the background of the CMM...

[xpensive]

Even with a thermal xpansion as small as 0.5 mm, something's gotta give without the combined mounting losing stiffness in any direction, the idea of somehow locking the engine-structure and take it as compression-stress instead is...err...

So if it came from ringo himself.

As for the BMW mounting, my money is on those long studs bending inside the valvecover brackets with the engine's xpansion, while pretension heads have spherical seats against said brackets. Guidance and lateral/vertical support could come from two keyways in a Y-arrangement, above the fixed position at 0600, so that vertical xpansion is perfectly matched by horizontal.

Did you manage to follow my reasoning marcush?

[marcush.]

I completely agree with your line of thoughts even if it took me a few steps ,mate.

[747heavy]

while looking for the Tyrell suspension pic, I found this one
Seems that Cosworth used these blade style flextures for quite a while, well
into the 80´s.



@ Marcus,

As for the picture, to tell the truth, I don´t know.
it says that in the discription: "engine mounting machined from titanium"
I agree it looks a bit odd for an engine mount, but cant really
picture it to be an upright either.

[747heavy]

to futher outer investigation into engine mounting systems a bit, here some more photos. I appears that 4 bolts are quite common.






interesting carbon structure connecting the valvecovers with the carbon strut
on this Renault engine.
IIRC Renault has hat some issues with there wide angle engines




On another note, I remember that back in 2000 Team Astromega was disqualified from a F3000 race or qualifying, because of an infringment with their engine mounting bolts/studs.
If I remember correctly, they where found, to have used slightly oversized bolts.
Which may gives some weigth to Riff_Raffs assessment, that a large part of the conections torsional stiffness, relies on clamping force/friction.

Even when at the back at Barcelona, he would not just trail around and give up but pushed hard all the time. In only his second race, at Silverstone, Alonso qualified sixth, only to be penalised and disqualified for a minor infringement regarding his Lola's engine mounting bolts.