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

[Richard]

I keep looking for shots of the studs. Here's one:

(the owner has disabled downloading of their photos)

http://www.flickr.com/photos/wenny_wu/2 ... 1/sizes/l/

humble sabot - If you use Firefox ...

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Click on "View page info"
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Click "Save As"

[ringo]

@ringo: what do you mean by 'staked'? the wall thickness can't be too great in that area as the portion enclosing the fuel bladder is supposed to be deformable.

The studs have to be rooted some how. I don't think bonding a flange inbetween the layers is secure enough. I have highlighted what i meant on this shot. The studs lie deep within the side walls of the tub. There might be additional layers at these anchor points.

[747heavy]

anchor points/hard points will vary in size and design from chassis to chassis, but here an example.
note the small holes for good resign penetration/bonding.

[humble sabot]

Make me look bad why don't you!
hahaha

good spotting on the Renault ringo, it was late when i found that and there's so little contrast on the file as is. looks like a nice solution.

[Brian.G]

The groove adjacent to the threaded part, what's the purpose of it?
Is there a collar on the cylinder head that slots over the groove, keeping the engine on the bolt in the event of a thread/nut failure?

I agree about the mismatch not producing much stress transversely.
Vertically, i don't think there will be a big issue. The temperature differences may be too small to create much strain. A cup of tea, may be about 80 degrees C?
The engine face, may be at water or oil temperature?

The composite layup is interesting, i know little about it. Maybe it's better to have the engine as the less stiffer part. The metal is more forgiving in that sense.

Waisting(narrowing) of the shank is commly used on high stressed bolted applications.
The weakest portion of the stud is the minor diameter of the threaded portion. When the bolt is torqued up, all the stress will be concentrated locally to this area, while the rest of the stud will remain not so stressed. By waisting the body of the stud slightly less than the thread minor diameter then the stress can be shared more evenly throughtout its full length. The non-waisted sections you see are for location purposes.
Doing it this way takes maxium advantage of the tensile properties of said stud steel. While at the same time achieving maximum resistance to fatigue.

The groove near the threaded section is also for stress relief. It is of similar principal to an undercut fillet radius on a crank journal. The important factor concerning this groove which cannot be seen n the picture is where it lies once the nut is on and tight. It should always extend to below the first thread on the nut.

If you want to design a stud, and incorporate this groove then the measurements for groove are as follows.

Width of groove = .5 the maximum thread diameter.
Radius of groove = .2 the maximum thread diameter.
Depth below root = .4 of the thread pitch.

I hope this explains the 'mystery' behind the stud in question, its nothing to do with weight reduction.

Brian Garvey.

[ringo]

What you are saying is true. The bolt is designed for greater impact strength.

You mentioned stress concentration at the narrowest section, which is where the groove is, that was a good reminder.
I haven't touched on these things in a while, and i had to get a refresher in one of my books. (Goes to show a book should be read whole! )

To add to what you said already i'll list out the points.

1. Miminize stress concentration by using a thread with a smooth, generous fillet at the root.

2. Leave a short length of full diameter shank under the bolt head to serve to centre the bolt.

3. Design for uniform stress throughout the bolt by reducing the diameter in the lesser stressed portion of the shank.

I think these are the main guidelines. This should guide the shape of the bolt. Honestly i've never payed much mind to bolts.

The highest stress is at the thread, as mentioned. Rule 1 is applied there. The fillet is required on both pilot surface and thread root.

Apply #2, to make the stress nearly equal to the stress at the thread root. #2 and 3 are straight forward.

The goal is to increase the impact energy capacity of the bolt; which is a function of the volume.

Brian, you're right on the money.

I was slacking off in some of these posts, i gotta sharpen up.

[Brian.G]

Gee thanks!

As for reminding yourself from a book, you should have never forgotten such a vital thing

Brian!

[humble sabot]

here's an interesting thing that came up...

I was checking out the new Renault and the engine seems to have an asymetric and high mounting scheme; viddy:

(courtesy everybody's favorite Scarbs)



there doesn't appear to be a lower mount, and there are two on the righthand valve cover, and only one on the left! Unless i'm missing something.

[RickRick]

Whats to stop the teams heating the engine before installing it, they have the equipmeant to pre heat before they run it. they must be able to take away half of the expansion, by building the mounts to suit the block at say 60c rather than 20c

[seventhsin]

The left hand valve cover looks to have 2 mounting points, the same as the left. One looks to be used to temporarily? attach some electronics.

Also, people have been discussing the ~1mm expansion of the engine, using aluminium in the formula.
However the many parts of the engine are held together with steel/titanium fasteners, which again would have a different expansion rate to the aluminium components.

Wouldn't that mean that although the approximate dimensions of the engine would expand by ~1mm at running temperatures, the stress is being divided and contained over hundreds of fastening points within the engine itself, possibly leaving only the slightest expansion to be absorbed at the bulkhead?

[langwadt]

Whats to stop the teams heating the engine before installing it, they have the equipmeant to pre heat before they run it. they must be able to take away half of the expansion, by building the mounts to suit the block at say 60c rather than 20c

I'm almost certain I've heard Nicolas Kiesa say that engine is heated before it is bolted on

[flynfrog]

Not sure Id buy the heating the engine before install. You would have to keep the spare engine on a heater to change out after Friday practice. You would also have to remove the old before it cooled off or leave in on the engine warmer. Not saying its impossible but seems like a huge pain even for F1.

[flyboy2160]

i just noticed this thread.

ringo, i can't see how the cf sandwich bulkhead can restrain the thermal driven dimension changes in the aluminum engine. if the engine bolt hole distance increases by, say 1mm, the sandwich panel would have to generate the equivalent of the force required to compress that engine face by 1mm. that ain't gonna happen in any kind of normal sandwich panel.

since everybody else has guesssed, mine is that at least 2, perhaps all, of the 4 long skinny bolts are used in a way similar to those clever cosworth flexures. that is, as somebody already surmised on this thread, the bolts are long and skinny to accommodate bending. i wouldn't be surprised to see a conical washer set under the nut.

[abw]

The groove adjacent to the threaded part, what's the purpose of it?
....

Waisting(narrowing) of the shank is commly used on high stressed bolted applications.
The weakest portion of the stud is the minor diameter of the threaded portion. When the bolt is torqued up, all the stress will be concentrated locally to this area, while the rest of the stud will remain not so stressed. By waisting the body of the stud slightly less than the thread minor diameter then the stress can be shared more evenly throughtout its full length.

....

Brian Garvey.

Good stuff. It renders the bolt/stud's high stress concentrations at the thread roots irrelevant by introducing a smooth stress concentration outside the threads. It essentially turns the stud into a dogbone tensile-test (or LCF/HCF-test) specimen. Predictable crack-growth is better than the alternatives.

As to the adjacent discussion about whether the engine is preheated before mounting... I don't know. But I do know that "bolting people" can be willing to endure a lot of hassle in service of their craft. The machines I work on (power-generating steam turbines) are held together by bolts that we preheat well above operating temperature before tightening, so when they cool/shorten, they are extra tight. Assembly/disassembly is a pain, but there is really no better way to do it. We deal.

First-ever post at this amazing website. A lurker emerges from behind his rock.

[Brian.G]

The groove adjacent to the threaded part, what's the purpose of it?
....

Waisting(narrowing) of the shank is commly used on high stressed bolted applications.
The weakest portion of the stud is the minor diameter of the threaded portion. When the bolt is torqued up, all the stress will be concentrated locally to this area, while the rest of the stud will remain not so stressed. By waisting the body of the stud slightly less than the thread minor diameter then the stress can be shared more evenly throughtout its full length.

....

Brian Garvey.

Good stuff. It renders the bolt/stud's high stress concentrations at the thread roots irrelevant by introducing a smooth stress concentration outside the threads. It essentially turns the stud into a dogbone tensile-test (or LCF/HCF-test) specimen. Predictable crack-growth is better than the alternatives.

As to the adjacent discussion about whether the engine is preheated before mounting... I don't know. But I do know that "bolting people" can be willing to endure a lot of hassle in service of their craft. The machines I work on (power-generating steam turbines) are held together by bolts that we preheat well above operating temperature before tightening, so when they cool/shorten, they are extra tight. Assembly/disassembly is a pain, but there is really no better way to do it. We deal.

First-ever post at this amazing website. A lurker emerges from behind his rock.

Kinda like the principal behind hot rivets, but easier open

Greetings to the site too by the way from Ireland,

Brian,