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

[ConsFW]

Hi guys, I'm wondering how the F1 engine/gearbox assembly is mounted to the tub. I know it is bolted on somehow but how is it aligned? Pins? How do you get a strong, repeatable mounting system?
Anyone have pictures of the arrangement? I'm designing something that could use some inspiration from this interface.

Thanks!

[riff_raff]

ConsFW,

The mounts are ring dowels (sometimes) and studs at the extreme corner points of the engine. These are usually the cam covers and oil sump. The composite tub side uses ti bushings.

In this picture you can see two points (bores) on the cam cover and one down to the right of the pump drive. These are the mounts to the chassis. The mounts to the trans are similar.



Here you can get an idea of just how tiny the current F1 engines really are:



riff_raff

[ConsFW]

riff_raff,

Thanks for the info and pictures. If I'm understanding this correctly, the tub has threaded studs that go into the holes on the cam cover and oil sump. In the picture I can't see a space cutout for a nut to be threaded onto the threaded stud. If there is a cutout for the nut, wouldn't this be less than ideal since the engine/gearbox would essentially be attached to the engine by tabs? Or are the threaded studs somehow screwed in on the tub-side and the engine/gearbox side holes are threaded to accept this?

Also do the dowel pins handle the shear loads or do the threaded studs do that?

[ak07]

If they are similar to the Dallara IndyCar(which they look to be mounted in the same way)then the studs are on the tub side.

In this picture you can see the studs on the rear bulkhead of the tub, as well as the studs on the gearbox/bell-housing of the motor.

[marcush.]

but ...how is the difference in expansion of the tub and Engine catered for?

The engine has reasonably a delta t of some 120/130°C so it surely grows considerably in height and width over temps .whereas Carbonfibre is notat all..
So either you accept some movement and strain or you have to introduce some clever pin fit geometry to alow the bits to expand and shrink providing full installation stiffness when hot.
I´d guess ..the sump fixation is not really the big issue but on the cylinderheads you need a bit of ingeNEWEYity ?

[xpensive]

Inereting issue there marcush, if we assume your delta T of 120K, the distance between studs about 400 mm and an alfa of aluminum alloy of some 20 micron per K and meter, there's one millimeter there to care for, isn't it?

[marcush.]

Inereting issue there marcush, if we assume your delta T of 120K, the distance between studs about 400 mm and an alfa of aluminum alloy of some 20 micron per K and meter, there's one millimeter there to care for, isn't it?

thats my line of thought .It´s not that much if you are a carpenter but we are not carpenters ,are we? the bolts will of course not only move horizontally but also vertically..so there will be difinitelly some knacking sounds when things cool down..

[ringo]

It doesn't have to expand. That change in length with temperature can be converted to a stress value. This would be the added compressive stress if the metal in not to expand outwardly but forced to bulge.

Anyone recall Poisson effect?

just a little intro:

http://en.wikipedia.org/wiki/Poisson%27s_ratio

If the engine is held at the studs, if the studs are stationary, the mounting flanges will be forced to take the stress and expand in the directions it is free to.
I guess this would be very minimal movement.

[riff_raff]

Cons,

I don't think there's much shear load at the engine/tub interface. In the old days they used to attach the upper engine to the tub with flexures to allow for thermal expansion mismatch between the two, and those thin flexures would not have been capable of taking shear loads. You can see an example of these blade mounts here:



riff_raff

[mx_tifoso]

Good thread from February;

F1 engine mountings and stiffness.

[xpensive]

I'm not sure where Poisson's comes into play here, but stretching or compressing Aluminium 1% of its length, would in theory introduce a stress of 700 MPa, far above the yield point, why something's got to give, like bending the mounting studs perhaps?

[marcush.]

I´m not happy with the explanations yet.
I cannot believe someone would just rely on bolts as interfaces between engine and tub but preferably you would interlock the two assemblies by some keys allowing the engine assembly to grow and just provide the clamping force with the bolts?
that ways you could have stiffness yet the small movement needed..

the cosworth camcover mountings show dowel sleeves recesses ...so maybe this alignment thing is incorporated in the tub?

[ak07]

Its not just clamping force. If it was a short bolt instead of a long stud, I could almost see your point.

The studs are fairly long and provide a few inches of shank. The tolerances are also fairly close. Even without the nuts, the engine would hang off the tub and the fact that the nuts aren't on or tight wouldn't be noticeable unless you were to look at the studs up close.

Anyways, talking about the heat thing again, an air gap works wonders in such a scenario, with large keyways or something, heat would be transferred much more easily. Not to mention the fact that there are 6 or more studs at the far edges of the engine, there's really no chance for flex. The stiffness of the actual tub itself and the motor block and gearbox housing make the real difference.

Think about it, how would any other way keep the motor/tub from flexing or having any sort of play/movement any less than with 6 + studs on the outside of the motor assembly?

[riff_raff]

I'm not sure where Poisson's comes into play here, but stretching or compressing Aluminium 1% of its length, would in theory introduce a stress of 700 MPa, far above the yield point, why something's got to give, like bending the mounting studs perhaps?

xpensive,

The aft face of the tub may not be very stiff in shear. If it is less stiff in shear than the engine front end, then the engine structure would not have to assume 100% of that thermal mismatch strain. The chassis needs to be stiff in bending and torsion, but I don't think having a super-stiff shear plane at mid-body would be necessary, would it?

riff_raff

[ak07]

I'm not sure where Poisson's comes into play here, but stretching or compressing Aluminium 1% of its length, would in theory introduce a stress of 700 MPa, far above the yield point, why something's got to give, like bending the mounting studs perhaps?

Well, I don't think you can think of it in such an isolated way. The forces are being introduced so far away (front wheel, rear wheels etc.) that there's plenty of bending and torsion forces absorbed by the rest of the car, if the forces could be an issue flexing,bending or twisting the tub or the motor with the commonly used studs, I think we would have internal engine issues as well!