standard impact attenuator current status?

[Yunlong Xu]

Hi,

in the new 2011 rule states that a standard impact attenuator is being designed and developed by the Rule Committee.

Does anybody know what kind of status it is in and when it will be finished and released?

we are thinking of using that standard design and therefore really need to know about it before we can finalise our front bulkhead.

cheers,
Yunlong

[Dsenechal]

Indeed, We would like to know the status of the "standardized" Impact attenuator.

We are also curious how design points will be added/taken away for a student design vs the standard design. Anyone care to comment?

[Yunlong Xu]

Any news? just about to finalise the chassis design...

And it's really annoying that we are told that there will be a standard IA design but don't really know when...

[Mumpitz]

I think it ought to be large and pink and weigh 20lbs basically to reward the teams that invest their time and effort. This is a design competition, if a team can't handle designing an IA and sending it out for testing wouldn't you question their ability to design a safe car period? No offense to those to those who wish to use the OTS one that SAE is offering, I can't blame you. Assuming the price is right it's a no brainier. But for the teams that have spent a considerable amount of resources buying different materials, doing all the calculations (ahead of time), conducting preliminary testing, finding testing sponsors, and learned something.... There really ought to be some way to differentiate the teams that buy and the teams that design. Feel free to disagree.

[RANeff]

Mention all your testing/analysis in the design comp...?

[Mumpitz]

Safety and ergonomics design criteria:

Driver interfaces, seat, belts, steering wheel,steering column, control panel/dash, cockpit sizing & protection, driver comfort/ease of control, shifter, pedals, braking system. Is this car as safe as it can be? Selection and use of
materials.


Mention all your testing/analysis in the design comp...?

It has been my experience that the judges are not as concerned with the impact attenuator. That portion of the design event seems to be more focused on driver interaction rather than crash worthiness. The IA essentially has a tiny potential point value but is required. If it is so critical to the design of the car that you are not allowed to run without an approved one there ought to be more value allocated to it one way or another.

[Sormaz]

Originally posted by Mumpitz:
I think it ought to be large and pink and weigh 20lbs basically to reward the teams that invest their time and effort. This is a design competition, if a team can't handle designing an IA and sending it out for testing wouldn't you question their ability to design a safe car period? No offense to those to those who wish to use the OTS one that SAE is offering, I can't blame you. Assuming the price is right it's a no brainier. But for the teams that have spent a considerable amount of resources buying different materials, doing all the calculations (ahead of time), conducting preliminary testing, finding testing sponsors, and learned something.... There really ought to be some way to differentiate the teams that buy and the teams that design. Feel free to disagree.

Do you design your belts and wrist restraints as well?

Teams that design an IA will be rewarded by their design...If you design your own IA then that should imply that it has some benefit when compared to the template one (weight, size, cost savings etc...) and there is your reward

[Mazur]

We're also waiting on the verdict of this one. Our reasoning is to save man hours that can be spent doing other tasks.

[Kettering Admins]

Kettering was initially contacted in hopes that we might be able to do the testing on a spec impact attenuator with our crash sled. We have since been told that there is no funding to design and test them and that there will not be one. I don't know if they are still looking to do this in the future or not.

However, we are going ahead with our own plans to test impact attenuators sometime in January. There is a thread from a few months ago with more information.

[American]

Back to the top.

We need this information. Is there another way to get this information, other than on the forum? A certain person to talk to?

[Kettering Admins]

There is no spec impact attenuator information because it doesn't and won't exist. This is coming from somebody on the rules comitte that originally brought the idea to us.

If you wanted our info, it is found here: http://fsae.com/eve/forums/a/t...=342100584#342100584 (http://fsae.com/eve/forums/a/tpc/f/125607348/m/950104484?r=342100584#342100584)

[Bill Riley]

I will post an update on this tomorrow.

[Yunlong Xu]

Thanks Bill. That's very good news!

[STH]

Very interested in this topic too. I can arrange a test day in early 2011 for impact attenuators. Contact me for details.

[Bill Riley]

Hi everyone. Here is an update on the spec attenuator.

As the Kettering post eluded to, when I came up with the idea for the 'spec' attenuator the original thought was to find a University grad student or similar to work on the design and do the testing. Kettering graciously agreed to look into it, but the funding never came through. At that point I decided to work on it myself because I thought it was something worth doing.

I have a preliminary design and I have been working through the commercial issues of sourcing an energy absorbing foam. Obviously, whatever material we pick needs to be able to be purchased from any team who wants to around the world, so specifying an obscure product that is hard to get was not ideal. I've made good progress and hope to have the commercial issues resolved next week.

Once the foam is decided up the next step will be to test the design and tweak the geometry to pass the requirements. I've asked Kettering to test it, and they are looking into it, but anyone else who is able to donate this service please let me know.

The design is intended to be easy to manufacture, relatively insensitive to manufacturing tolerances, easy to confirm at the event and be applicable to a wide range of nose sizes. It is not intended to be the lightest attenuator out there, and as is implied in the idea of a standard design, once you change it, you have to go through the full process on your own.

Since I'm basically at maximum bandwidth on FSAE projects, I'm going to use this as the first test of the 'open source' FSAE project I have been thinking about for a long time. The idea here is for individuals at Universities who may not have an FSAE team, they can work on a specific part of the car that appeals to them and then post it to the open source website for others to use in their own designs. This will also be valuable for teams who may only have six people and if they can readily pickup a few designs that work, it would help them out. Again, none of these are going to be the lightest, greatest parts out there, but it gives people some exposure, especially in places where there may not be a culture of racing or race cars.

So in summary:

1) No guarantee this will happen. I'm working on it, but if it is going to be successful it needs community involvement.
2) I will push the commercial side for the foam source and as soon as it's confirmed will post the information on cost/availability.
3) I need a University or individual willing to make the initial prototypes.
4) Need to find a place to quasi-statically crush the initial prototypes, and iterate as necessary
5) Finally, I will post the final drawings, pictures, manufacturing techniques so anyone interested can make the design.

The current foam I estimate to be about 1.5 pounds (0.7 kg). How does that compare to the mass of other attenuators people have made in the past? That doesn't include the steel insets that get bonded into the foam to take shear loads and attach to the anti-intrusion plate, nor bolts.

The Rules Committee has been extremely swamped lately, so there are not multiple people working on this. I am trying to push it through on my own, which was not the original intent. So I appreciate all of your patience. Remember, if this spec attenuator is a huge failure, you'll still need to one, so I hope you all will put in place a fall back plan. Finally, remember you don't need to test your your designs dynamically, quasi-static crush is acceptable, so that may ease the process of developing your own design.

I will be updating fsaeonline dot com with the files for you to download. The current (Draft) solid model with attachment holes is on there now. The holes get steel sleeves bonded in, then bolts installed to attach it to the frame.

The link can be found off the main page at fsaeonline dot com.

Regards,

Bill Riley

[Yunlong Xu]

Thanks Bill. I believe that a standard IA is a genuinely good idea, especially when this component is actually safety critical.

Our plan B is to use what we had last year(test results as well as the actual IA). The rule does allow that, right?

The problem for us is that we are a very small budgeted team so Aluminium honeycomb is pretty expensive for us. So we need to make something that is a bit overengineered to make sure it passes the test at the first time, otherwise we'll have to waste more materials on further tests...

[Tom W]

700g for a foam impact attenuator sounds pretty low. We had a foam IA that was not at all optimized in '08 that weighed in at just over 1.5kg.

[Thunder Wolf]

Hello Bill !

I am one of the team captains from Lakehead University. We apparently can't use our previous design for an impact attenuator, since it was dynamically tested on a "home made" testing rig. Although the report that was sent in about it last year received a high score, so I don't understand the issue.

Our university doesn't own any sort of equipment for the quasi-static crush. We are basically bound to the standard attenuator due to the rule change.

I might be able to arrange a way for us to build a prototype to your design and then ship it off to whomever is willing to do the testing. I may even be able to help with finding a team to do that for us. And we would be willing to put the test results together for use in whatever report needs to be written up.

If there is anything else we can do to help make sure that a design is available to everyone ASAP, please let me know. We are reluctant to start building our frame before we know that our bulkhead is suitable for the attenuator and anti-intrusion plate. I am sure there must be a few other small, low budget teams out there who are in the same position.

Thanks,

Oliver

[D.J.]

I know that we are in the same boat as Oliver.

UConn doesn't have any type of crash sled or quasi-static equipment that I know of. Our in shop setup was a lot better than a backhoe but it is obviously off the table.

Although I did not see anything in the rules specifically stating that team could not use old results, ours would be invalid because of the new anti intrusion plate rule.

B3.21.9 During the test, the attenuator must be attached to the anti intrusion plate using the intended vehicle attachment method. The anti intrusion plate must be spaced at least 50 mm (2 inches) from any rigid surface. No part of the anti-intrusion plate may permanently deflect more than 25.1 mm (1 inch) beyond the position of the anti-intrusion plate before the test.

As far as I can tell without a standard attenuator our team and many others are basically screwed.

[KeWLKaT]

And sadly this whole ordeal is taking so much time as the design phase for much of the vehicle is already over, and yet we are here waiting for news on the IA, and cannot do anything to purchase materials or whatnot.

[Yunlong Xu]

[QUOTE]
B3.21.9 During the test, the attenuator must be attached to the anti intrusion plate using the intended vehicle attachment method. The anti intrusion plate must be spaced at least 50 mm (2 inches) from any rigid surface. No part of the anti-intrusion plate may permanently deflect more than 25.1 mm (1 inch) beyond the position of the anti-intrusion plate before the test.
[QUOTE]

I'm a bit confused by this rule. Does it mean that we cannot now perform a drop test(ie, with the IA facing up) because this would mean that we need to have our IA & anti-intrusion plate floating because of the 50mm gap rule?

So horizonta impact test only?

[Tom W]

I assume the intent of the rule is to force teams to test the impact attenuator on a representative section of the front of their car. I'm not quite sure why the rules committee wouldn't just say this though if that was the case.

[SNasello]

It was pointed out at the FSG conference that the intent of the rule is to ensure that there is not more than 25mm of deflection of the anti-intrusion plate. This means that in order to test the actual deflection of the plate, you need to install it on a representative front bulkhead (normally 25mm thick) as it would be in your car. The 50mm is to allow an additional 25mm air gap behind the test piece. The additional 25mm attachment to the test bench (sled or ground) should be rigid.

I also don't fully understand the rules commitee doesnt make these things a little more clear when writing the rules, especially when it comes to something like impact testing.

[Yunlong Xu]

The only test rig that we've got is somehwere you can put the IA on, and then it will be crashed downwards. I'm now finding it really difficult/impossible to carry the test specified with the 50mm gap on our test rig since it will mean that we need to find someway to support the structure up 50mm...

[Bill Riley]

It's very hard to write rules that are understandable by everyone. Obviously, we thought this was clear enough or we would have revised it before publication.

Bolt the impact attenuator to the anti-intrusion plate. Bolt/weld or otherwise attach the anti-intrusion plate to a 1" welded box section or something equivalent to represent the front bulkhead. Add another 1" of spacer material (box tube, supports, whatever) to the back of the fake front bulkhead to give you 2" between the anti-intrusion plate and the bed of the Instron or whatever baseplate you're using. Then crush the attenuator and make sure nothing bottoms out on the baseplate.

[D.J.]

Thinking about this a little more...

If teams that do not have approved testing equipment and opt to use the standard IA (assuming one is supplied), how will they prove that their anti-intrusion plate will not deflect more than the 25mm? Will using the approved material and attachment method

(B3.20.4 On all cars, a 1.5 mm (0.060 in) solid steel or 4.0 mm (0.157 in) solid aluminum “anti-intrusion plate” must be integrated into the Impact Attenuator. If the IA plate is bolted to the Front Bulkhead, it must be the same size as the outside dimensions of the Front Bulkhead. If it is welded to the Front Bulkhead, it must extend at least to the centerline of the Front Bulkhead tubing.)

be sufficient?

I guess I am a little confused about what this is actually supposed to be testing. Is this just another check for the IA or is it more of a test for your anti-intrusion plate and bulkhead?

If it is more for the a.i.p. and the bulkhead then obviously the setup and possibly the total deflection will differ team to team.

[Yunlong Xu]

Originally posted by Bill Riley:
It's very hard to write rules that are understandable by everyone. Obviously, we thought this was clear enough or we would have revised it before publication.

Bolt the impact attenuator to the anti-intrusion plate. Bolt/weld or otherwise attach the anti-intrusion plate to a 1" welded box section or something equivalent to represent the front bulkhead. Add another 1" of spacer material (box tube, supports, whatever) to the back of the fake front bulkhead to give you 2" between the anti-intrusion plate and the bed of the Instron or whatever baseplate you're using. Then crush the attenuator and make sure nothing bottoms out on the baseplate.

Thanks Bill for your clarification. I originally thought that '50mm gap rule' would mean nothing at all between the plate and the bottom of the rig. Now if we are allowed to use solid tubes to create this gap, it will make our job a lot easier.

I'm not sure about the 'not bottom out' requirement as you said. Surely in the rule it says the anti-intrusion plate can't deflect more than 25mm, which means that it can't deform lower than the 'model bulkhead'? So there will need to be at least 25mm gap after the test between the anti-intrustion plate and the bottom of the rig, right?

Anyway, still waiting for the standard IA design and hoping that we dont' have to make one our own. The materials can be quite expensive and we can't afford making many test pieces...

[moose]

Yunlong,

I think the 50mm gap is designed to provide a way to provide for measurement of how far the plate deflects down. If you had the bulkhead section flat on the test-bed of the instron, you couldn't easily measure if the anti-intrusion plate touches down in the center, since you wouldn't be able to see it or fit anything underneath. With the extra gap, you can see & measure what's happening (probably one of a few different ways).

[Some Guy]

Had a few thoughts on the attenuator testing ban here. I cant say I have the best writing style in the world so hopefully this is coherent.


I feel it's worth it to point out the ban on impact attenuator testing doesn't actually stop unsafe methods of impact testing. With what can be a potentially expensive test, a team that needs to test out the attenuator with a backing plate for the first time might just go and use whatever home made crash rig they have lying around until they get the attenuator and backing plate rules compliant, same goes for teams doing a complete redesign of the attenuator and for new teams. At the point they get there in house testing working they could simply send it off for "official testing". The people who approve the unit would be none the wiser because the unofficial data is not actually sent in, and the team's university never has to know about it either.

To put it another way, a team that feels their attenuator may not work and is strapped for cash, as quite a few teams are, may just go and test it themselves until they have something that passes. To use Kettering's number, 300 dollars a test could add up real fast if multiple tests are needed. I think my team tested something like 5 iterations of our attenuator last year. So there is still motivation to test it yourself because each test (not including the attenuator itself) is basically free if a school has traditionally done the test "jerry rigged". At the cost of an official test there is quite some motivation to make sure it passes the test on the first try creating the incentive to test in house in spite of the ban.

I am not convinced that quasi-static testing is the best idea either. Nothing stops teams from making there own crush rigs. Unlike, say a drop rig however a poorly designed crush rig (one that uses hydraulics for example) can fail unpredictably and at any time. Compare to a drop rig where you know that the weight is going down and it you use at least a marginal release system only when you tell it too. I suppose both examples you would need to exercise good engineering judgment (or maybe just common sense), but as has been demonstrated that isn't always the case.

I really dont see any way to eliminate unsafe testing methods without releasing a spec unit and ensuring that it costs less than other testing options (otherwise the cost incentive still exists).

EDIT: Thought about this a bit harder, changed and added a few things.

[EHog]

What if the current attenuator in development was deemed mandatory? That way you throw the safety concern of testing out the window. Also, the safety concern of "will it actually work?" is eliminated.

After all, they don't let us make our own 6 point harnesses...

In my opinion, the team that crashed into a backhoe would have been safer without an attenuator at all.