Front reinforcement/Impact bar third party fabrication technical information

[rider]

This thread won't read as a flowing conversation because the comments were all replies to a thread started by another member on the titled subject. That thread was 'tidied' up at the request of the OP which meant the technical content discussed was in danger of being lost which some of us felt would have removed, forever, information that is useful for anyone attempting to fabricate front crash bars either for their own use or as a commercial operation. 

Is it really that simple to fabricate a crash bar?

I would have though they have to be crash tested to a deformation specification under a given load so that they absorb  the force of the impact preventing frame damage below a specified force of impact or reducing the damage above the specified force of impact. Otherwise just about any RSJ would suffice.

[rider]

A quick read around the subject it seems beyond the actual physical design the composition of the 'aluminium metal matrix composite' (sounds complex)  is critical in car crash boxes to give it the deformation properties over say buckling, cracking or tearing in a crash situation. So it is critical to use the correct grade metal, aluminium comes in so many guises from alloys to varying silicon levels.

[rider]

People should get some legal advice to look into the ramification of commercially supplying untested safety equipment. Probably adding a disclaimer along the lines of 'not for road use, for show purposes only' would cover you against any possible litigious action. 

[Frank Bullitt]

rider is right. In today’s age of compo culture ("where there's blame, there's a claim") it is routinely and improperly sought without being based on the application of legal principles such as duty of care, negligence or causation.

It’s an ethos which believes that all misfortunes, short of an Act of God are someone else's fault. “Suffering” is relieved by the receipt of a sum of money.

[rider]

Crash bars are important safety equipment, for the car occupants, the car structure and also what is hit. They are formed from a specific alloy that is selected for its strength and corrosion resistance (used primarily in aviation and motor industries), it's not your average sheet off the shelf.

People don't have a clue about the potential implications of untested safety equipment in cars. The industry deformation test has 100kg impacted at 16kmph. Now that isn't difficult to work out that its assessing a human impact and the damage a crash bar will do to a human body or legs. So, if your fabricated crash bar ends up taking out someone's legs because it is too stiff, or cracks and cuts away under the force of the impact you can imagine where that may end up. I'm sure no one would want to see that.

[The Raven]

Then  are not every after market part libel to a claim? 

May as well shut the classified ads down. 

For what its worth the OEM bar is paper thin id doubt it does anything but protect your rads in event of a slow speed impact. 

[Tyson]

On 7/25/2021 at 6:49 AM, rider said:

Crash bars are important safety equipment, for the car occupants, the car structure and also what is hit. They are formed from a specific alloy that is selected for its strength and corrosion resistance (used primarily in aviation and motor industries), it's not your average sheet off the shelf.

People don't have a clue about the potential implications of untested safety equipment in cars. The industry deformation test has 100kg impacted at 16kmph. Now that isn't difficult to work out that its assessing a human impact and the damage a crash bar will do to a human body or legs. So, if your fabricated crash bar ends up taking out someone's legs because it is too stiff, or cracks and cuts away under the force of the impact you can imagine where that may end up. I'm sure no one would want to see that.

That's todays standards though not those of the early 90's, if this is an OEM replacement I would assume it would only need to conform to the period tests? Cars today are made in a way that they protect pedestrians in the event of a low speed impact, this is the reason why most modern cars that are in such an impact, have to replace parts that are designed to crumple and absorb impact. I can assure you that isn't the case for the supra, some muppet in a car park reversed into my car and his brand new Corsa's bumper crumpled and was scrap whilst the Supra's bumper had not even a scratch to speak of. Given some of impacts I have seen, the Supra is built like a tank and fairs pretty well in some scary accidents. Another reason why most car designs today are boring compared to historic cars who could pretty much design what they wanted! Pedestrian safety, what's that? I always think of the Aston Martin Lagonda 4 door when this topic comes up, imagine being hit by the below at any speed.

I am not disagreeing that given the nature of the item in question, that either some testing is required or as many have said that this designated as for show/off road use only and that is not designed to be used on the road to protect against legal proceedings. 

[jim_supra]

On 7/25/2021 at 11:22 AM, Tyson said:

That's todays standards though not those of the early 90's, if this is an OEM replacement I would assume it would only need to conform to the period tests? Cars today are made in a way that they protect pedestrians in the event of a low speed impact, this is the reason why most modern cars that are in such an impact, have to replace parts that are designed to crumple and absorb impact. I can assure you that isn't the case for the supra, some muppet in a car park reversed into my car and his brand new Corsa's bumper crumpled and was scrap whilst the Supra's bumper had not even a scratch to speak of. Given some of impacts I have seen, the Supra is built like a tank and fairs pretty well in some scary accidents. Another reason why most car designs today are boring compared to historic cars who could pretty much design what they wanted! Pedestrian safety, what's that? I always think of the Aston Martin Lagonda 4 door when this topic comes up, imagine being hit by the below at any speed.

I am not disagreeing that given the nature of the item in question, that either some testing is required or as many have said that this designated as for show/off road use only and that is not designed to be used on the road to protect Keron against legal proceedings. 

Was just typing something along these lines, Barry is seemingly applying modern safety standards to a 30 year old design. That's not to say safety isn't and shouldn't be a consideration when putting non standard parts on our cars, but in Barry's example of the bar potentially causing additional injury then surely things like fitting a front mount or metal radiator cooling plates would as much or more of a concern to pedestrian safety, for which I doubt has ever been mentioned.

For peace of mind then I'd agree, some sort of disclaimer to protect themselves would be worthwhile.

[Annabella]

On 7/25/2021 at 11:36 AM, jim_supra said:

Was just typing something along these lines, Barry is seemingly applying modern safety standards to a 30 year old design. That's not to say safety isn't and shouldn't be a consideration when putting non standard parts on our cars, but in Barry's example of the bar potentially causing additional injury then surely things like fitting a front mount or metal radiator cooling plates would as much or more of a concern to pedestrian safety, for which I doubt has ever been mentioned.

For peace of mind then I'd agree, some sort of disclaimer to protect themselves would be worthwhile.

That's exactly it, and I think what Rider means, the above comments all tilt at protecting that person.

[Frank Bullitt]

 

The Toyota crash bars use EN AW-7003 aluminium alloy, a zinc containing alloy

Its the top alloy specifically formulated for its corrosion protection and strength (rated 4 out of 4 for both). The 7xxx alloys are apparently stronger than some steel alloys and resist cracking/tearing. Essentially they are ductile and not brittle unlike some decorative aluminium alloys that you can shatter with a hammer blow.

https://www.makeitfrom.com/material-properties/1050-H14-Aluminum

https://www.makeitfrom.com/material-properties/7003-AlZn6Mg0.8Zr-A97003-Aluminum

[rider]

There are over 140 alloy grades of aluminium. These have been developed to give the best possible characteristics in a enormously wide variety of applications from decorative picture frames and strips through the aircraft fuselages. You seem unaware but these are not one and the same materials, they have been designed and then adapted with exhaustive application testing to give best results in their environment. So your decorative aluminium doesn't need to withstand any kind of stresses it just needs to look nice and look good; polish up nicely. Your fuselage alloy needs to be high strength, light weight and low corrosion. Onto crash bars, these need to be high strength and low corrosion. They also need to be deformable in the instance of an accident to lessen the force of impact on the vehicle and also the body hit.  You can stretch a 7xxx grade alloy fully a third more before it'll crack than a 1xxx grade. That is kind of important if deformation is a key property and it is in crash bars.

So, if you are making crash bars just like Toyota then you do maybe need to think which one of the 140 commercial alloys out there do I go for, the pretty one you can polish up nicely or the high strength deformable one? I'd suggest the logical solution would be to copy the Toyota choice if you want to be just like Toyota. Its what I would do, use the very same alloy material. That kind of takes the pin a tail guesswork out of it. Anyone who commercially retails has to be able stand behind and to support their claims, in a court of law if required.

[Tyson]

I have split some of the comments off as requested to form a technical post of reproducing this part. I have done my best to include and modify all posts to make sure they pertain to the reproduction of this part in general terms and not a specific product. Any further posts should remain general and not make reference to a specific part already being reproduced unless you have factual information that would be useful to this thread. Please feel free to remove or change comments as you see fit to make it read better as a standalone thread.

[Scooter]

So a replacement bar might be too stiff and/or absorb a lower amount of energy than the stock one. 

The design of the original with open ends/non welded seams might be functional and allow more deformation/energy absorption. So the perceived improvement of welding these up might not be an actual one, and then yes Aluminiums like steels vary hugely depending on how they are alloyed and also made or heat treated/annealed after (other than i think copper, metals in cars will all be alloys).

I'd say having an aftermarket one would be better than none for the cars occupants, perhaps very slightly worse for a pedestrian (depending on where they hit)

When you have, Caterhams, Motorbikes, Ed China's Bed car, Flat fronted 40 tonne artics, and 4x4's with front moounted bull bars or winches the point about the spec and design of a aluminium bar becomes a bit moot for me?