40 replies to this topic

[johnny yuma]

Since the 1980s most sedan cars have front and rear screens bonded
to their aperatures,where they form part of the overall stiffness of the
body. Is it feasible to adapt this to older monocoque mass production
sedans,with a bit of fake rubber around to look right,thereby picking
up a bit of chassis stiffness ? Or would cracked glass be the result ?
Naturally I am talking a modern tough glass not the pre-seat belt stuff.

[SteveCanyon]

One thing I sometimes get to do that makes me giggle is to take an old car, one that has the old style windscreen mounted in rubber type thing, and drive over a rough road with my right hand out the window and a finger or two on the windscreen rubber. Quite often you can feel it moving around a good millimetre or so.
So I suspect it's not a good idea to try to use the windscreen as a structural brace on some older cars.

[johnny yuma]

Yes ,years ago I was in an argument with a VW Beetle owning mate saying his beetle was more rigid than my 1953 Holden.
We agreed on a similar trial,where you drove with drivers window down and stuck your finger in the gap between door
and frame to see which car squeezed your finger the most.Both gave a similar nip,but not enough to be scary. We then drove
a 1964 EH Holden as a comparison, (basically over dish drains, on a diagonal ,in each case)-- and the EH barely moved.

Must repeat with some new cars .....

[jatwarks]

I've driven an early Ford Focus since 1999, and such cars are clearly designed and built to a cost, when compared with older cars.

In my 11 years of ownership the bonded windscreen has had to be replaced 3 times; none due to impacts.

On the last occasion I saw and heard it go as I cornered, at a not unrealistic speed. The chassis flexed enough to produce a large crack at the lower left hand side of the screen.

Contrast this with the experience of a colleague 20-odd years ago when he managed to put a Morris 1800 landcrab onto its side (!). When righted, not only was all the glass intact, but all the the doors opened and closed as smoothly as ever, and there was no visible evidence at all that the event had happened.

[Terry Walker]

Using the glass to help stiffening allows lighter metal elsewhere, or so I was led to believe back in the days when bonded glass came in. Whether it's true or not I can't say from experience. But - back in the late 60s I rolled my VW Beetle (gosh! must have been the only VW beetle to roll!) and after the roll it was pushed on its wheels, all the glass was still there, the windows went up and down, and I drove it home. A few years later, I raced a 105E Anglia, couldn't afford laminated glass, but used the perspex allowed in the regs of the time. Would whip out the glass, pop the perspex into the same rubber, race, then put the glass back, and drive home (in theory).

Does that help muddy the issue?

Edited by Terry Walker, 07 July 2010 - 12:43.

[MatsNorway]

Yes ,years ago I was in an argument with a VW Beetle owning mate saying his beetle was more rigid than my 1953 Holden.
We agreed on a similar trial,where you drove with drivers window down and stuck your finger in the gap between door
and frame to see which car squeezed your finger the most.Both gave a similar nip,but not enough to be scary. We then drove
a 1964 EH Holden as a comparison, (basically over dish drains, on a diagonal ,in each case)-- and the EH barely moved.

Must repeat with some new cars .....

Im guessing the reason the Holden did not squese the finger so much was because the frame and the body were separated units.

Im also guessing that old windows were thicker than what's used today. Someone should measure on their cars.

[johnny yuma]

Im guessing the reason the Holden did not squese the finger so much was because the frame and the body were separated units.

Im also guessing that old windows were thicker than what's used today. Someone should measure on their cars.

The 1953 Holden and 1964 Holden both monocoque--in fact Holden were monocoque from the first one in 1948. The vw beetle
was a semi-monocoque having a pressed floorpan thingy with the top bolted to it AFAIK.

[Bloggsworth]

I've driven an early Ford Focus since 1999, and such cars are clearly designed and built to a cost, when compared with older cars.

In my 11 years of ownership the bonded windscreen has had to be replaced 3 times; none due to impacts.

On the last occasion I saw and heard it go as I cornered, at a not unrealistic speed. The chassis flexed enough to produce a large crack at the lower left hand side of the screen.

Contrast this with the experience of a colleague 20-odd years ago when he managed to put a Morris 1800 landcrab onto its side (!). When righted, not only was all the glass intact, but all the the doors opened and closed as smoothly as ever, and there was no visible evidence at all that the event had happened.

The Land Crab had the stiffest production monocoque in the world, probably still is - A figure of 12,000 pounds/feet or foot/pounds (I can never remember which way round) was mentioned. It did remarkably well on the London/Sydney Rally.

[MatsNorway]

The 1953 Holden and 1964 Holden both monocoque--in fact Holden were monocoque from the first one in 1948. The vw beetle
was a semi-monocoque having a pressed floorpan thingy with the top bolted to it AFAIK.

Simply well made then.

[OfficeLinebacker]

The Land Crab had the stiffest production monocoque in the world, probably still is - A figure of 12,000 pounds/feet or foot/pounds (I can never remember which way round) was mentioned. It did remarkably well on the London/Sydney Rally.

What? How did they do that? Was it super heavy?

[Bloggsworth]

What? How did they do that? Was it super heavy?

I don't know, don't even know if they deliberately designed it that strong, or it just turned out that way; the weak point was the lower A arm mountings, which rusted away and gave the car a distinct limp. It was big, took 8 people to my dad's funeral - Not responsive, about 5 or 6 turns lock to lock, but built like a brick....... outhouse.

From Wikipedia:The 1800 was voted European Car of the Year for 1965. It proved a strong competitor in endurance rallying finishing second in the 1968 London-Sydney Marathon and achieved three of the top 20 positions competing the 1970 London to Mexico World Cup Rally*.

The bodyshell was exceptionally stiff with a torsional rigidity of 18032 Nm/degree, this was greater structural rigidity than many modern cars up to the end of the century.

I remember Bob Curl telling me, when he was doing some work on the BMW run in the European Touring Car Championship by Bob Sparshott, that even running the stiff suspension they did, with the windscreen out, the car was torsionally so weak, you could jack one corner up really high and 3 wheels would still remain on the floor.




*And that wouldn't have been because of the "B"Series engine!

Edited by Bloggsworth, 07 July 2010 - 19:30.

[OfficeLinebacker]

Yeah Blogg I immediately read the wikipedia entry also, what an interesting car. I want one. LOL

[Bloggsworth]

Yeah Blogg I immediately read the wikipedia entry also, what an interesting car. I want one. LOL

Oh no you don't - believe me.

[Lee Nicolle]

A lot of Aussie and US cars had the screens bonded in from about 71 on. And I have never seen one of those cars crack a screen through flexing. Though HQ-WB Holdens had the screens come loose regularly as the bonding failed.
These days most screens are fitted with sikaflex which generally does not come loose if everything is clean and dry when fitted.The stuff does flex a little which generally stops the screens from flex cracking. I doubt that method or the old rubber style really makes a great deal of difference for torsional rigidity.
As a matter of interest old style safety glass screens are a LOT stronger than any laminated glass..
And modern car glass is all getting thinner, inc replacement screens for some older models. A good fitter can make a real difference when fitting thinner glass too an old car. Other wise the appearance is lousy as their is big gaps between glass and trim.

[Greg Locock]

Firstly 12000 ft lb/deg is not very stiff these days, however it is stiff enough for practical purposes, the gains above 8000 are mostly in bragging rights, and are useful for fine tuning shake, not handling.

Secondly, I have seen a lot of cracked windscreens on prototype cars. This could be due to poor proto windscreens, poor aperture design, or something else. So i'm not exactly 100% sure that you can just bond a screen into an old car and call it done. My gut feeling is that because the car isn't designed to react loads via the roof the screen might see more load than usual. If it were for a circuit car where you have run into a brick wall with shock tuning it might be worth the risk.

[gruntguru]

One thing I sometimes get to do that makes me giggle is to take an old car, one that has the old style windscreen mounted in rubber type thing, and drive over a rough road with my right hand out the window and a finger or two on the windscreen rubber. Quite often you can feel it moving around a good millimetre or so.
So I suspect it's not a good idea to try to use the windscreen as a structural brace on some older cars.

If there isn't any movement, bonding the screen is not going to stiffen the structure. Bonding with Sikaflex is probably still going to allow movement in perhaps the 0.1mm range and of course the screen itself is not totally rigid.

Edited by gruntguru, 08 July 2010 - 01:23.

[DaveW]

I recall Greg L stating that the glasswork contributes a large percentage to the torsional stiffness of a modern road vehicle. I think he suggested around 30%. FWIW I can usually measure the difference in torsional stiffness doors open & doors closed although it's difficult to be confident about absolute numbers, largely because many road vehicles seem not to have true structural bulkheads.

However, in my experience, that is not the case for racing tin tops (with a couple of not-so-honourable exceptions). This is because the mandated roll-over cage is usually used to transmit torsional loads between the suspension hard points. It is normal to find that the highly scientific "finger across the door shut line" test can detect no relative movement when such a vehicle is warped on its suspension.

[mariner]

One reason the BMC austin 1800 " land crab" had a high torsional stiffness for it's day is the design of the front bulkhead and the rear suspension. The front suspension was mounted into a large ( and I think very strong) cross tube. This in turn was mounted right up into the dash bulkhead structure and fed the loads into the A pillars and straight down into the sills. So there was less distance between the spring loading points and the A pillar than most modern strut designs. Aslo remember that the springing/damping was hydroelastic so those loads went in to the big cross tube.

Similarly at the back the trailing arms and springs were all reacted into the front of the trailng arm ( like the Mini) so the torsional load path started forward of the rear wheel and right at the back of the side sills. With no hatch the rear end was strong too. So basically the distance one would measure torsional stiffness started by being a lot shorter than the wheelbase or what it is on most modern cars. I think this helped.

On the windscreen bonding one of the key things is that the screen has to be well bonded as it acts as the reaction point for the airbag when it goes off, espeically with modern raked screens. So if it is poorly installed it could pop out when the bag deploys , not good news.

The good news on modern cars is that the lack of corrosion means that the original chassis stiffness should stay the same ( roughly). Some tests on 1970's cars showed the loss of stiffness and crash strength after 6-7 years of rust was quite scary.

[pugfan]

The good news on modern cars is that the lack of corrosion means that the original chassis stiffness should stay the same ( roughly). Some tests on 1970's cars showed the loss of stiffness and crash strength after 6-7 years of rust was quite scary.

Might be a mixed bag there, when I cut a chunk of the engine rail out of a peugeot 504 ute I thought I'd be clever and jack up that corner when putting a new section in. The idea was to open the gap, put the piece in, close the gap to clamp and then get everything in alignment again before welding. Imagine my surprise when jacking the whole vehicle on that corner resulted in no change in the gap at all. This was an english car so not lacking in the rust department.

[gruntguru]

Might be a mixed bag there, when I cut a chunk of the engine rail out of a peugeot 504 ute I thought I'd be clever and jack up that corner when putting a new section in. The idea was to open the gap, put the piece in, close the gap to clamp and then get everything in alignment again before welding. Imagine my surprise when jacking the whole vehicle on that corner resulted in no change in the gap at all. This was an english car so not lacking in the rust department.

Got Pajero rods in that puppy?

[SteveCanyon]

Got Pajero rods in that puppy?

Shush you, it's a secret!

[pugfan]

Got Pajero rods in that puppy?

Special peugero ones this bloke was selling, said they were ex motorsport ones. Got 'em for a real good price, he seemed keen to get rid of them.

[johnny yuma]

In 2004 I did the guided tour of the Holden Commodore plant in Elizabeth,SA.The bulkhead/dashboard assembly is one huge unit made offsite.
It gets lowered in fairly late,there is one bolt put in from each side at the moment the assembly is bonded all around to its apeture,to locate it
precisely.A bit later the screens are bonded in .Our "tour guide" said before the dash unit and screens are bonded in there is not a lot of
stiffness in "the box" because the ends of the box are not complete. I THINK the glue-in of bulkheads there started with the VN Commodore in 1998,
could be wrong.

[Tony Matthews]

Special peugero ones this bloke was selling, said they were ex motorsport ones. Got 'em for a real good price, he seemed keen to get rid of them.

Were half of them bent, by any chance?

[gruntguru]

Were half of them bent, by any chance?

Pugfan's no fool - he bought the straight ones from the left bank - only needed four for the old 504. Had to pay a bit more for them of course. (Don't tell him he can get brand new ones from the Mitsubishi dealer for 1/10 th price.)

Edited by gruntguru, 11 July 2010 - 09:41.

[Tony Matthews]

Pugfan's no fool - he bought the straight ones from the left bank -

Paris? Well, why not?

(Don't tell him he can get brand new ones from the Mitsubishi dealer for 1/10 th price.)

That secret is safe with me!

[pugfan]

Pugfan's no fool - he bought the straight ones from the left bank - only needed four for the old 504. Had to pay a bit more for them of course. (Don't tell him he can get brand new ones from the Mitsubishi dealer for 1/10 th price.)

Damnit! I knew there was something suspicious about the beret, onions and stripy shirt he was wearing.

[Tony Matthews]

Damnit! I knew there was something suspicious about the beret, onions and stripy shirt he was wearing.

Perhaps his rods were a bit of a con.

[SteveCanyon]

Since we're being silly ...
This is my next Le Mans Prototype challenger. It's in the little-used 4WD road-based class.



That's the Pooj up at Cape York a few years ago.
I call it "The Squid", because when it takes off it leaves a big black cloud behind it.


Okay more seriously ....
How do the diesel-powered cars in the endurance races keep the oil clean for the length of the race? I know from The Squid the oil gets visibly dirty quite quickly.
Apologies for the thread drift.

[gruntguru]

How do the diesel-powered cars in the endurance races keep the oil clean for the length of the race? I know from The Squid the oil gets visibly dirty quite quickly.
Apologies for the thread drift.

Nobody cares what colour the oil is (unless its all over the track).

Actually I'm sure those things make a lot of smoke - they race with big particulate filters on the exhaust (unlike the truck racers and tractor pullers). A lot of smoke means a lot of soot in the oil so they would need either frequent oil changes or micro-filters, spinners or some such.

[pugfan]

How do the diesel-powered cars in the endurance races keep the oil clean for the length of the race? I know from The Squid the oil gets visibly dirty quite quickly.

I think it was the last works Peugeot or it could have been the customer car but when it was retired there was a nice jet black trail of oil that it left. The commentary was to the effect that it was re-assuring to see that even in the top diesel motorsport category they couldn't keep the oil from going black.

Edited by pugfan, 12 July 2010 - 00:27.

[Greg Locock]

The bulkhead/dashboard assembly is one huge unit made offsite.

The European Omega/carlton has been doing that since the mid 80s or earlier. The idea is that you can build the IP up and debug it off the vehicle, rather than having to tear the car apart at the end of the line to fix a loose wire. Great idea. It also allows you to use a robot to install the unit, reducing back injuries.

We tried replacing the channel fixed with goo with lots of bolts to see if it improved the stiffness- it didn't.

However, fixing the cross car beam in with one bolt at each end is structurally inefficient, they'd be better to use three bolts.

[OfficeLinebacker]

Okay more seriously ....
How do the diesel-powered cars in the endurance races keep the oil clean for the length of the race? I know from The Squid the oil gets visibly dirty quite quickly.
Apologies for the thread drift.

They change the oil at the pit stops

[Catalina Park]

Cummins came up with a system to increase the distance between oil changes in long distance trucks. When the oil reached a certain critical limit the motor would automatically drain some oil out of the sump into a tank and add some fresh oil to the motor. The oil that was drained out of the sump was then metered in with with the diesel and burned.

[gruntguru]

Cummins came up with a system to increase the distance between oil changes in long distance trucks. When the oil reached a certain critical limit the motor would automatically drain some oil out of the sump into a tank and add some fresh oil to the motor. The oil that was drained out of the sump was then metered in with with the diesel and burned.

Most locomotive engines worldwide use a similar system. Fresh oil is used to replenish any oil that is burned or leaks from the engine. When the engine is due for a rebuild, it gets an oil change as well.

[Bloggsworth]

Most locomotive engines worldwide use a similar system. Fresh oil is used to replenish any oil that is burned or leaks from the engine. When the engine is due for a rebuild, it gets an oil change as well.

I am at a loss to understand exactly how much more torsional stiffness is imparted by an oil change....

[gruntguru]

I am at a loss to understand exactly how much more torsional stiffness is imparted by an oil change....

Yes. Its beyond my analysis capabilities. The main thing to bear in mind is the oil change should be performed before the point where torsonal stiffness is effected. BTW, when you go past this point on a Diesel, the oil change will normally reduce the torsional stiffness not increase it.

Edited by gruntguru, 13 July 2010 - 22:55.

[Bloggsworth]

Yes. Its beyond my analysis capabilities. The main thing to bear in mind is the oil change should be performed before the point where torsonal stiffness is effected. BTW, when you go past this point on a Diesel, the oil change will normally reduce the torsional stiffness not increase it.

"Doh!" says he, slapping his forehead with the heel of his hand, "It's bleedin' obvious now that you have explained it".

Edited by Bloggsworth, 14 July 2010 - 21:27.

[OfficeLinebacker]

LMAO @ this thread.

[gruntguru]

LMAO @ this thread.

Whats so *&%ing funny?

[Bloggsworth]

Whats so *&%ing funny?

Your spelling....