Using the block as a stressed member

I thionk with that sideways thing you're kind stuck with having SOM<E mountings, those on the "side of the engine" onto the subframe or crossmember.

Those on the "ends" Might be nice on the "chassi rail".

But yea I've seen VW block with big hunks broken off when they nudged into thiongs like parking berms or curbs

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

john vanlandingham Wrote:
-------------------------------------------------------
> Dazed_Driver Wrote:
> --------------------------------------------------
> -----
> > So in a rally car, what is the point of
> this?
> > Wouldnt the strut bar and crossmember brace
> the
> > strut towers enough? Especially if you run
> your
> > cage to it... I dont see why you'd want to
> use the
> > block to strengthen.
> >
> > Feisty Peacock?
>
> The major point is this is so much stronger AND
> you can service crossmember and steering or DROP
> THE WHOLE CROSSMEMBER without screwing around
> supporting the engine because your motor is
> mounted ON the crossmember.
>
>
>
>
> John Vanlandingham
> Sleezattle, WA, USA
>
> Vive le Prole-le-ralliat
>
> www.jvab.f4.ca


To add to what John said, it provides an elegant solution in that one part serves two functions. Your motor provides power and serves as a structural member of your chassis. That engine bay is a big fawkin hole subject to flex and deflection. Tying your motor to the chassis so as to provide some sort of triangulation is akin to putting the cage in your car. Done properly, wouldn't it be neat to alleviate some of that flex?

---

It is useless for the sheep to pass resolutions in favour of vegetarianism, while the wolf remains of a different opinion.
William Ralph Inge

TANSTAAFL

Vorpal_Rally Wrote:
> Done properly, wouldn't it be neat to alleviate some of that
> flex?

No.

---

Grant Hughes

NoCoast Wrote:
-------------------------------------------------------
> Vorpal_Rally Wrote:
> > Done properly, wouldn't it be neat to
> alleviate some of that
> > flex?
>
> No.
>
>
>
> Grant Hughes
> www.nocoastmotorsports.net
> Denver, CO

Ok, please explain why not. My understanding is that flex is bad, and that you want your suspension to feed it's load into the chassis, while the chassis remains rigid. Is it block deformation that you're concerned about?

---

It is useless for the sheep to pass resolutions in favour of vegetarianism, while the wolf remains of a different opinion.
William Ralph Inge

TANSTAAFL

Vorpal_Rally Wrote:
-------------------------------------------------------
> NoCoast Wrote:
> --------------------------------------------------
> -----
> > Vorpal_Rally Wrote:
> > > Done properly, wouldn't it be neat to
> > alleviate some of that
> > > flex?
> >
> > No.
> >
> >
> >
> > Grant Hughes
> > www.nocoastmotorsports.net
> > Denver, CO
>
> Ok, please explain why not. My understanding is
> that flex is bad, and that you want your
> suspension to feed it's load into the chassis,
> while the chassis remains rigid. Is it block
> deformation that you're concerned about?

He's being a wise ass, I'll smack him upside the haid when he calls tonight.
>
>
> menja bé, caga fort i no tinguis por a la mort!

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

Vorpal_Rally Wrote:
-------------------------------------------------------
> Ok, please explain why not. My understanding is
> that flex is bad, and that you want your
> suspension to feed it's load into the chassis,
> while the chassis remains rigid. Is it block
> deformation that you're concerned about?

That makes sense. I meant it's not neat. The only point I'd see to do this is to make stuff more serviceable. Rigidity, blah, blah, is just a beneficial side effect.
There's enough much bigger things holding people back speed wise on the stage than rigidity. Like crappy suspension, lack of brakes, poopy gearboxes, diffs, and final drives, lack of testes, etc. I've seen the videos.

---

Grant Hughes

FWIW I've yet to need to replace an engine or trans crossmember during an event.

I've replaced them after events cuz it seemed prudent.

My engine's weight being on the engine crossmember has bent the crossmember where the mounts attach.

I can see doing what Kevin did for a four cylinder.

Methinks that I'll leave my six in there the way it is.

---

JohnLane

Overkill is consistently more fun

i'm with grant on this because, just like a normal engine mount, the mounts in Kevin's car have busings too.

bushings flex- no stiffness advantage. (as far as stiffening the engine bay, a questionable pursuit)

separate note, replace old engine mounts with new or better. your shifter won't bounce out of gear, you will feel better throttle response, and the inside of the car will be slightly louder.

cross members are big, and engines are big, but the earth is biggest. biggest wins, your shit will move, but it will take the rest of the car with it. I've had the skidplate, resting on the crossmember lift the car off the ground hitting potholes on tahola, but never bend dent or break. If you're off the road that fast and far, something else will break first.

---

"I put the hurt on dirt" - adam crane
http://CraneRallyCrew.com
corolla gt-s "Patches"
Op: S.S.

Adam, I have faith in you. You'll break the earth. You just have to hit it hard enough

---

Welcome to the cult of JVL drink the koolaid or be banned.

acrane Wrote:
-------------------------------------------------------
> i'm with grant on this because, just like a normal
> engine mount, the mounts in Kevin's car have
> busings too.
>
> bushings flex- no stiffness advantage. (as far as
> stiffening the engine bay, a questionable
> pursuit)

That depends on the bushing of course. A steel bushing is a bushing. If your subframe is properly fastened to the rest of the car, you already have a bottom chord running through the engine bay. On Kevin's car the stiffening is more of the strut towers which are definitely stiffer now. How much stiffer? Would have to do some massive modeling or put the chassis on one of those racks with hydraulic cylinders for loading the the suspension simulating running over rough terrain with some string running across the bay. I think it's an awesome job, if not symmetrical (hard to do with a slanted block).

> separate note, replace old engine mounts with new
> or better. your shifter won't bounce out of gear,
> you will feel better throttle response, and the
> inside of the car will be slightly louder.

No doubt.

> cross members are big, and engines are big, but
> the earth is biggest. biggest wins, your shit
> will move, but it will take the rest of the car
> with it. I've had the skidplate, resting on the
> crossmember lift the car off the ground hitting
> potholes on tahola, but never bend dent or break.
> If you're off the road that fast and far,
> something else will break first.

JVL has always said the big thing with this is so that you're decoupling the engine from the cross member (which has servicing advantages) and the engine mounts are less likely to fail. Which is awesome. You could also now make a redesigned cross member, since it's no longer being loaded by the engine.

Do you need to do it? Definitely not.

---

Andrew M
Onterrible
30ish

> >
> > bushings flex- no stiffness advantage. (as
> far as
> > stiffening the engine bay, a questionable
> > pursuit)
>
> That depends on the bushing of course. A steel
> bushing is a bushing. If your subframe is
> properly fastened to the rest of the car, you
> already have a bottom chord running through the
> engine bay. On Kevin's car the stiffening is more
> of the strut towers which are definitely stiffer
> now. How much stiffer? Would have to do some
> massive modeling or put the chassis on one of
> those racks with hydraulic cylinders for loading
> the the suspension simulating running over rough
> terrain with some string running across the bay. I
> think it's an awesome job, if not symmetrical
> (hard to do with a slanted block).
>
That is exactly what I was getting at. The way Kevin's car has the engine mounted to the strut towers does add rigidity to them. How much? like you said, some kind of torsional deflection rig or a 6 -7 post chassis rig would be able to quantify the result. Are we ever gonna do this at this level, probably not.

---

It is useless for the sheep to pass resolutions in favour of vegetarianism, while the wolf remains of a different opinion.
William Ralph Inge

TANSTAAFL

Vorpal_Rally Wrote:
-------------------------------------------------------
> That is exactly what I was getting at. The way
> Kevin's car has the engine mounted to the strut
> towers does add rigidity to them. How much? like
> you said, some kind of torsional deflection rig or
> a 6 -7 post chassis rig would be able to quantify
> the result. Are we ever gonna do this at this
> level, probably not.

If I were doing it for rigidity. I would mount the block plumb (you need a b20 oil pan and oil pump parts). This will allow you to make symmetrical mounts and hence be adding the same rigidity to both towers. I would also make the sheet metal mounts run as far up the strut towers as you could space allowing. Even if they are only an inch thick at the top.. it will help. Be sure to carry them down and into the subframe rail like the one on the left of the pictures (passenger side) JVL posted.

Something you need to do, definitely not.

I should note that the engine itself isn't doing anything positive and if anything it's a negative as it's putting weight on the strut towers. Quite sure it's a net positive though. For the engine to be an actually stressed member you'd have to run some kind of mount to the top of it.. and that's not very realistic.

---

Andrew M
Onterrible
30ish



Edited 1 time(s). Last edit at 03/20/2008 11:10PM by hudson.

Oi oi oi, everybody is an expert.
Such a simple suggestion of something that struck me the instant I saw it first 20 years ago, and so much discussion. Oi!

Too bad Toyota didn't have such well reasoned arguments cause it looks like they fell for the same mistaken logic that I did on their only serious RWD car they did:
http://www.mat.fi/n_index.php?nav=gallery_view&gallery=projecttoyotacelicaturbotc35.xml&g=13

See piccies no 4-5-6 and 23
Some of you 'pooter whizie boys could you put one of those photos here?

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

I can't seem to find any pictures if it online but while it is common practice to use a stressed block in formula cars they do it to blocks that were designed to handle the loads. I can also think of two examples where they went to great pains not to feed loads onto a stock engine block. Gigantic billet machined valve covers were created to send the chassis stresses through instead.

It would be very application specific to determine if you were going to put bad enough loading on the engine block to distort it and cause damage in operation. So, not that anyone here is going to try it but your best bet is to do a giant billet valve cover that can handle being attached to your chassis as a structural member.

A 7 post rig is also unnecessary for finding the torsional rigidity of your chassis. Just bolt the back suspension pickups to the floor sitting on some rigid mounting, support one front suspension point on a jackstand, apply a big lever to twist. The twist can be measures and converted into a lb/degree or other applicable measurement. Nobody is going to do that either so it doesn't really matter. Like Grant said fix all the other stuff first.

Tim



Edited 1 time(s). Last edit at 03/21/2008 12:06AM by Tim Taylor.

john vanlandingham Wrote:
-------------------------------------------------------
> Oi oi oi, everybody is an expert.
> Such a simple suggestion of something that struck
> me the instant I saw it first 20 years ago, and so
> much discussion. Oi!
>
> Too bad Toyota didn't have such well reasoned
> arguments cause it looks like they fell for the
> same mistaken logic that I did on their only
> serious RWD car they did:
>
>
> See piccies no 4-5-6 and 23
> Some of you 'pooter whizie boys could you put one
> of those photos here?

John, you're coming off as if that was an attack man. I know you don't mean to come off that way because I'm pretty sure I said it was a good idea and you did a good job on Kevin's car at least 4 times.

Lee/Vorpal was talking about using the engine as a stressed member. I was just pointing out that mounting the engine that way doesn't in and of it self particularly achieve that. The cross member should be doing most/all the work anyways. However the mounts could be used to strengthen the strut towers.

He's talking about making the car stiffer and I'm wasting time talking about how he could go about it.

---

Andrew M
Onterrible
30ish