Being the victim of a side impact, which totaled my car, this issue is rather close to my heart.


Side Impact Strengthening 2

Would these extra rails help in a side impact or are they just extra weight?

I liked the idea of triangulating that large expanse below the seats, for extra twist stiffness, maybe it's not necessary though.

Any other ideas for strengthening the basic chassis against side impacts, short of a roll-cage?


[Edited on 8/4/06 by millenniumtree]

Are you building a car for a hamster?
IMHO, the proposed extra steel is too low to be of much use in a side impact.It would make the toprail fold over onto the occupants.

Yes they will help, but I have no idea how much.

In a 7, side-impact protection seems really hard... to impossible. The seating position pretty much screws you right from the start. No matter what's done to the car, roughly half your body is free to fly sideways, with potentially the head hitting the other car's bumper. Even if the head doesn't hit anything, the sudden sideways acceleration is sure to cause a whiplash type injury.

I'd think the best thing would be a true wraparound seat, one with side bolsters at head level.

Short of that, maybe build a box-like structure several inches thick in the side rails. It would provide a slower sideways acceleration.

Oh, and whatever rollbar anywhere near the driver's head Really needs SFI-approved rollbar padding, not that soft stuff that does nothing.

Give NSDEV a shout - he's usually on the button with this kinda thing.

I would tend to agree with Owelly, trying to strengthen there, might have 'adverse' effects and actually cause less protection where you want it :-(

You could always butcher a VOLVO and put SIPS airbags in - must be possible... hmm there's one down the breakers I saw today - might investigate myself

Or try to find some 3D physics modelling software and investigate the different options you talk about - see if you can get any positive increases.

Please keep us updated - this is deff a useful thread

[Edited on 8/4/06 by muzchap]

Ha! No cupholder, but it's got side impact airbags. No, I think I'll leave the explosives off the car.

I guess any high-speed side impact is gonna screw you over pretty bad anyway... Might be better off braking or accelerating out of the way enough to take the impact on a corner so you'd spin rather than get crushed... but then again who's to say your "attacker" wouldn't swerve the same way you tried to dodge... Being from the land of SUVs, we little car drivers have to be extra careful when pulling into an intersection.

I made the mistake of zooming off when the light turned green. The guy who hit me thankfully hit the passenger side (with no passenger), so I had the whole side of the car to take the impact for me. If he would have hit the driver's side, I might be dead, and more than likely I'd be very seriously injured. I had enough time to brace for impact though, and I remember holding my arms up to protect against glass shards (window was all the way down, but glass still went everywhere)

Hmm. Good thought about the wrap-around-seat for head protection! I'm sure they make some racing seats that might help hold the head in place or at least provide a slot you could push your head back into if you knew a crash was imminent.

Does triangulation help much against bending of the square as well as shearing?

And yes, I'm building a hamster car - 1/8th scale for my action man.

Look at the side impact protection on the Striker pictured below. I believe thats the going to be the most simple anf effective way of increasing your side impact protection.

You want the point of impact to be as far from you as possible which will allow some of the energy to be dissapated as the crash structure de forms. The triangle being a very strong will resist crushing and spread the impact energy away from you and into the chassis rails.

As mentioned above most of us tend to half hang out the side and drag our elbows on the ground in corners So again the wide bars give you arms and upper body more protection.


Image deleted by owner

[Edited on 8/4/06 by bimbleuk]

First if you are really worried about side impact protection do not drive a 7 style vehicle !

A seat with a wrap around head rest will probably help because in a side the head really goes side to side, a good neck brace may also help.

The other thing you require is space between you and the point of impact, so sit in the middle!

I think the best solution would be pontoons between the wheels, rarther like on go karts. These could be made of an energy absorbing material, honey comb or foam.

Do not even think about airbags. They are lethal in the wrong application.For example a passenger airbag inflates to a 120 litre baloon in around 20ms, that is not 2 tenths of a second but 2 tenths of a tenth of a second, there is some energy there.

Also the rate of deflation is important for an airbag, the occupant actually hits it as it is deflating, so the energy is absorbed. The rate of deflation varies for each vehicle, factors as the vehicle weight and crush structure and position effect this.

Finally the electronic sensors required to decide on a fire or no fire are required and the hard bit the software to fire them at the correct time. If it fires too early the occupant hits a bag that is already deflated, too late and they hit an inflating bag!

A good solid roll cage with good padding and a neck brace (Hans) is porbably your best bet.

As you have a real nice model of your chassis there play with hit, try pressing the side to see what happens, also try twisting it to chck the torsional rigidity. You can replicate pannelling by sticking on cardboard or formica.

John

PS I just happen to knowone of the best vehicle safety engineers in the country and it is something we have discussed!

[Edited on 8/4/06 by JB]

[Edited on 8/4/06 by JB]

Yeah and I said ....... Oh, you mean i'm not the best

(joking - esp as we've never met)

This something that worrys me after a crash 18 months ago where we "assisted in hedge remodelling" for a farmer.

I've come to the conclusion that i'm going to add in the upper two rails and pray the other car hits teh rear wheels! In a seven there isn't much more you can do before you end up with a full cage structure.

Looking at the chassis of a seven does lead to questions of side impact. I agree that the striker style ful cage with arm bars is probably the best solution.

However don't forget that you have the wheels sticking out of each side of the chassis when it's finished. The wheels, bones, driveshafts, shockers, springs etc will most likely be the bits to deform in a side impact. You'd be very unlucky if a car was to hit you square on between the wheels.

Unfortunatley this trend towards driving agricultural or even military vehicles on our roads is not helping safety.

IMHO

Mike

Once you've been involved in an accident in a seven, it's all too easy to get carried away and start trying to introduce protection measures just in case the same should happen again. Chances are, it probably won't.

When I go out for a drive in the seven, I know what chances I'm taking and understand the risks should I be involved in an accident (god forbid) The enjoyment I get from driving it, far outweighs all the risks involved (for me). If I want safety, I'll take the tintop.

AFAIK these extra bars are all on the MNR chassis.
couldnt hurt to add 'em, surely.

When you crash you need to absorb energy, ie slow down as slowly as possible, reduce the G forces.

One way of doing this is to have crush areas then a survival cell.

However to have crush areas you need space. One way is to make your structure solid and use the other vehicles crush area to absorb the energy. This is Ok if you hit another car and not a tree.

If you hit a tree in any car at speed not a lot will help except an ejector seat!


As has been said before if you are really bothered about safety do not drive a 7, drive the most modern biggest car you can!

John

This is my solution!


Panels on

I dunno what is the best option..

We even didn't notified that the car heidg of the average car today at the front.

Will touch with its numberplate our upper bar what i want to say is that this car isn't for safety..

Also the "KNEE" desing is very rigid but who says you want it that rigid?

I remember a accedent between a military TANK (leopard) and a train.

The train hits the tank also in his side.

The guy who was up on the tank just jumped of the tank and survived, the inner other 2 died! and the tank had nothing, and the trains front was messed up!!

the tank did whent 100Mtrs to the left..

Sow what i want to say, side impact is very very difficult.

Also during the accident we want that it takes as much time as we can let it take..

thats the reason we let everything bend and crush...
because then the total energie involved can be devided by more time, wich will result in less Wattage/Joules/BHP

(like you want to express it)

I Think that the seven is Best at his front!
then its back, and then its Side..

With other words, like any other car.

also i think that the KNEE desing won't pass SVA because imagine you hit a person with it....

Also there is on the Net or on this forum a pic of a side impacted dutch Donkervoort..

he hadd thebad luck hitting a Light post..

the chasis totally bended beond the light post..

will search the pic.

The orange desing is fine for side impact,

but i see danger in the front impact with susch suspension bars that far away
would they penetrate your legs, hip,middle if it would brake and penetrate the nose???

You should make them of Round tube material lets say 12mm, then the bolt won't give up, and it will only bend.

and never be able to penetrate,
it will still be very up to the job because of its high working angle.. get the trick???

Tks

thats the reason that in F1 every thing thing is on its limits in case something happens its like everything explodes and then you don't have the dangerous large bars...

[Edited on 8/4/06 by tks]

I agree about needing side crush structure, but the big problem is the 7 is simply too low for it to work! The other car's bumper will very likely come in above whatever's put there. Short of a real rollcage like on the Stalker, about the best we can do is a really good seat... and even then there's hardly any room. I vote for the seat side padding for the head, it's about simplist improvement with the most to gain, since most lethal injuries are head/neck related.

Agreed, the 7 type design is poo for active safety features. However, it is good at passive safety, ie you'll be unfortunate to crash, but in the poo when you do. A full wrap around seat with a hans systen for your helmet will help a lot with head injuries, but not a lot will stop the cars/4x4's bumper coming over the side rails. Best bet is to bugger off out the way sharpish and head for the hills/nearest field etc.

quote:

---

Originally posted by millenniumtree
Being the victim of a side impact, which totaled my car, this issue is rather close to my heart.


Side Impact Strengthening 2

Would these extra rails help in a side impact or are they just extra weight?

I liked the idea of triangulating that large expanse below the seats, for extra twist stiffness, maybe it's not necessary though.

Any other ideas for strengthening the basic chassis against side impacts, short of a roll-cage?


[Edited on 8/4/06 by millenniumtree]

---

Could someone measure the height of the top cockpit side rail from the road, and then measure the height of your tin-top bumper.

I suspect that in a side impact, the top side rail would take most of the impact force. I can't think of any way of making it any stronger, without replacing it with roll-cage tubing?

I've considered the option of building much of the chassis from roll-cage tubing, effectively giving a built-in cage (with twin roll hoops down to the floor, forward braced to the top and bottom side rails, and forward roll hoops at the scuttle or firewall). A bit OTT, but useful for a hillclimb/track day/club racer.

Triangulating the floor should help to make the driver compartment more rigid, which should help if you do have a prang. I'd opt for a V brace , with the point of the V on the trans tunnel. That should help to stop the driver compartment lozenging if you hit something rear corner first.

I am building a slightly larger LC7 using a Ford 392 V8 (500hp+-) so a bit more weight won't be quite as bad. What I'm considering is using 1/8" wall tubing for the entire upper rail, lower rail, outside tub section tubing with the other tubes being 16 gauge. Basicly frome the tub section with 1/8" tubing including a cage. Creating a cage with the windshield frame being the front hoop of the cage. I plan 16 gauge steel floor front firewall, trans tunnel, and rear firewall. Side skins will be 22 gauge steel and atleast the tub area wil be sprayed with a light coat of Linex (a polly based bedliner). This is still in a state of flux but since this will be primaraly a street car I want some level of protection from side intrusion.

[Edited on 10/4/06 by locostv8]

I think the simple answer has to be yes, the added tubes will reduce the chance of injury in a side impact.

Since we do not have access to the analysis tooks used by the big companies, we are usually best making the main structure stronger - if you design a part just inches from your body to crush, then your leg is liable to crush with it.

When considering side impacts, remember that you might slide into a fixed object like a lamp post. this would affect the top and bottom parts of the chassis.

Another way to strengthen the sides would be to use wider side tubes. The Tiger Super Six claims to use 1.5" tubes to improve side impact protection.

if you really want het rigid you need to make is this way:

What you should see is some triangle shaped sheet 3mm and an tube wich could be joined to the chasis on both sides...

when we now hit something, first the bart will deform and absorm allot of energie then the triangle sheet will bend and at least the main tubes of our chasis will take the rest of it.....

The only problem is that it isn't Beautifull, and you need to cover it with carbon fibre or sheet or something...
Rescued attachment SideImpact.JPG

The only viable way to help protect yourself in a side impact is some nerf bars at bumper height. Looks like the striker has that idea sorted out although w/o a helmet your head would come apart on the rollcage in a side impact.
A side impact is pretty much the worst possible and the locost is probably one of the worst performers. The bars under the seat are not a bad idea, but for a different reason. Imagine running over a sharp rock or something and landing with it under your seat with only 2 thin peices of aluminum between your strapped down arse and it .

If you want to increase the beaming (resistance to bending) of the A tubes
the attached pic works better.
This only helps if the impact is on the A tubes though, which are a little low.
When all hope seems lost, remember that the car is very light and will tend to be moved around rather than crushed in a crash with another vehicle. If they hit your rear axle the car will spin before the axle tubes crush. Add a good knee bar (good idea for a roll over as well) and then you basically need to be hit with the corner of a car in between the kneebar and the axle. Thats only a 2ft area to hit. Not very likely. A kneebar also gives you something solid to mount your steering column to.
Dont worry, the fear of crashing goes away after a while. I flattened the roof of my truck last summer and was driving pretty gently for a few weeks. Once I healed up I began driving like a dummy again .
Rescued attachment chassis-impact-strengthening-2.jpg

Here's a pic of what I'm doing (note still on my rough mockup proto chassis). I will have a full body to cover the side pods, which add vastly to the torsional stiffness.

If you were really serious, you could fill them with expanding foam

Cheers

Fred W B


[img][/img]

My idea was to turn the tub area into a bit of a cage and the knee bar is a good idea. Something I have been thinking, I know dangerious, was the use of 1.5 tube where I had stated 1/8 wall. Something that should greatly stiffen the sides would be to retain 1" or 1x1.5 for the top rail and sandwich the side skins with a second .5x 1.5 tube at least to the firewall area. In my case I will be using 245-45-17s & 315-35-17s so the side of the car is even further in from the tires. Part of the reason for a 663 is to allow a bit more room for the eng but also a bit more wiggle room in the cockpit. I'm 6'5" & 230 so my old bug eye while fun was almost painful.

quote:

---

Originally posted by JB
When you crash you need to absorb energy, ie slow down as slowly as possible, reduce the G forces.

One way of doing this is to have crush areas then a survival cell.

However to have crush areas you need space. One way is to make your structure solid and use the other vehicles crush area to absorb the energy. This is Ok if you hit another car and not a tree.

If you hit a tree in any car at speed not a lot will help except an ejector seat!


As has been said before if you are really bothered about safety do not drive a 7, drive the most modern biggest car you can!

John

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i personally donīt confirm the fact that

1) We are light sow lateral movement is easy==> because of the fact we are light and we have wide tires we are as sticky as possible!!!
2) We use the othercars crush zone, sow only problem for ''Tree'' crashes.. Iīm sure we will be better of with 2 crushzones who crus in each other...
also i don't see the fun of foam time crushzones...

Every crush zone has an effective working speed! foam would be helpfull bij 10Km/h but not by the more meaningful numbers.

Sow wee need to desing a crushzone wich collapses at 50Km/h..and wich collapses more difficult at 40km/h...

We need to win tenthīs of a second..not
thousands of it...

If we look at the front side of the hell fire car we see it was havily deformed i would call that the crush zone!

and in fact its desinged as rigid as possible.

Sow what i want to say is foam out Tube In.

Best bet is to drive with our six sense..

and be aware of the tipical problem areaīs.

wich are the areaīs where people think they are haveing preference but they donīt.

Regards,
Tks

The foam helps a suprising amount as under compression it progressively spreads the load into the surrounding structure.

As a "catch-all" solution that doesn't involve calcualtions etc it is quite effective......

still won't save you in a crash but might lessen the consequences.

Pipe insulation will not help in an impact as stated.

My test to see if padding is any good is if I can punch it with my fist. It should not hurt!

Foem blocks are used a lot in doors of production cars to reduce occupant injury values.

John

Something like this cage from Westfied would go a long way.

think the foam is more used to
dappen things like noise

and to give weight to the cars door...
maybe weight isnīt the right word,

i mean to say to have it full not empty..

Tks

you mean stop resonance?

Foam, of the right kind, is excellent at absorbing damange. Just think about polystyrene - very weak in lots of situations but great at absorbing impact.

Most modern plastic bumpers have a foam lining to absorb impacts, the plastic shell pretty much shatters when hit hard so does virtualy nothing for protection.

Sticky/wide tyres also have little bearing on the outcome, in an impact by far the main force will come from the intertia of the car rather than simple tyre friction. This is a double edged sword though, a light car will tend to start moving very early in the crash, potentialy helping the structure to protect the occupant. The downside is that the occupants will undergo a higher acceleration than they would in a heavier car, possibly adding to injuries.