[@ScarbsTech] thread on Zhou's Roll hoop (didn't fail in his opinion)
Posted Jul 4, 2022, 7:19 PM UTC
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It worked as designed, which doesn't mean the design (in this case regulations) can't be improved. But it wasn't a faulty part in any way
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Until they determine the actual force it broke at we don't know if "it did it's job". That has to be part of the investigation.
Saying that essentially it's OK, only because the other parts protected the driver is garbage plain and simple.
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For those in the comments saying that drivers are not allowed to sit higher than the Halo, unless something has changed in the past few years, the Halo itself is not even considered (correction: being below the halo) when determining how high a driver is allowed to sit.
Here's an image where Mercedes is checking Bottas's compliance during his seat fit, note that they do not perform this test with the Halo even attached to the car.
https://www.formula1-dictionary.net/Images/rool_hoops_f1_measurement.jpg
Again, unless this is outdated info, it's just a matter of being within the triangle formed by the two roll structures in the car.
Drivers can, and do, stick the tips of their helmet above the halo. In previous years, I recall Leclerc being one that sits several inches above the halo. I haven't noticed this year.
Edit: Checked the technical regulations, the 2nd image I sent is outdated. The secondary roll structure in the regulations is now the halo itself. So it's below diagonal line from the halo to the airbox. This still easily allows for a driver to be poking above the halo.
12.5.2 Helmet Position
The driver's helmet must lie below a line drawn between the front fixing axis of the secondary roll structure and a point 75mm vertically below the highest point of the principal roll structure.
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This still easily allows for a driver to be poking above the halo.
With the primary roll structure intact that is - the way the Alfa was destroyed, there was almost a bit of a "cut" in line with the Halo, see the bottom pic here, and in that case poking above the Halo isn't ideal.
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Cars have flipped before we had a halo, those protections are still in place.
The halo is for huge direct impacts which it did absorb in this case.
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I suppose it could be that just the roll hoop or just the halo on their own wouldn't have been enough, but in combination they did the job.
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Yep. Roll hoop took the brunt of having 900kg car dropped on it, and still kept going long enough to slow car down. Once it gave up, halo kept the head above the ground. Without halo, it would have been helmet scraping afterwards. So, in a sense, both devices did their job.
Although, I am assuming one of the change we will see is a new test. Another imaginary line from top of halo to some point of roll hoop much lower in the car. Basically same triangle but inclined the other way. And helmet will have to be lower than this second imaginary line as well. That way, if roll hoop disintegrates, helmet will still be away from the ground.
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Although, I am assuming one of the change we will see is a new test. Another imaginary line from top of halo to some point of roll hoop much lower in the car. Basically same triangle but inclined the other way. And helmet will have to be lower than this second imaginary line as well. That way, if roll hoop disintegrates, helmet will still be away from the ground.
Yeah 100%
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I have a pet hypothesis on this. It may be wrong, it's somewhat speculative, but in my view it does need to be considered.
Alfa Romeo this year are using the blade-type roll hoop and airbox design. This was originally pioneered by Mercedes part-way through the 2010 season on the W01 - see here.
The solution was then subsequently adopted by various other teams even after Mercedes themselves moved away from it. Force India used a solution like this on various occasions, such as on the VJM04 in the 2011 season.
Designs of this sort have cropped up semi-consistently since then - it's not been an enormously common design choice but there have been a handful of cars with it.
These blade-type roll hoops obviously pass all of the structural tests that the FIA impose. The question is whether the tests themselves are sufficiently all-encompassing to properly represent the real-world conditions in which a roll hoop might be called upon to protect the driver.
For instance, a blade-type roll hoop might stand up perfectly well to a loading running, as it were, 'top-down' - along the car's y-axis, representing the sort of force that would be imposed if the car was dropped, upside-down, straight down onto the roll-hoop.
However, such a roll hoop may equally be nowhere near as strong as a traditional triangular-style roll hoop when it comes to shearing force - forces trying to push the roll hoop sideways and collapse it that way. These are exactly the sorts of forces that one encounters when a car slides across the racetrack upside-down, resting on the roll hoop, as Zhou did yesterday.
Therefore, if the FIA's tests don't account for a scenario like this - and the performance of the roll hoop against forces in those particular directions is not tested - then the roll hoop might be perfectly legal and pass all the FIA specifications, but the FIA specifications themselves may be deficient.
I have also long harboured another safety concern regarding these blade-type roll hoops - that is, they are far more prone to digging into soft surfaces such as grass. If the car rolls and lands upside-down on the roll-hoop on the grass, it may be that the blade-type design simply penetrates the ground and digs into it, so that the driver's head is not then prevented from also impacting the ground.
I am going to try to research how roll-hoops are crash tested to look into this more, as it's interesting and I think will be an important safety topic in the near future.
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Scarbs has some info on the roll hoop tests in the same series of tweets: https://twitter.com/ScarbsTech/status/1543660406643871744?s=20&t=v7td71PR9YVCQ4wxkmxqHw (they do test loads from multiple directions).
And in this tweet that where it was ripped off is meant to withstand 13 tonnes: https://twitter.com/ScarbsTech/status/1543655417875951616?t=M1DLX0QHRKoIHy6HYFfGpw&s=19
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Designs of this sort have cropped up semi-consistently since then - it's not been an enormously common design choice but there have been a handful of cars with it.
I think for several years now, Sauber/Alfa Romeo were the only ones left using it. They briefly had a normal hoop-structure before returning to a blade.
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The roll hoop failed at its one purpose- protect the driver in case of rollover. When Zhou was sliding, the only thing protecting was the halo. So is it good the halo was there? Absolutely. But that is not what the halo is there for. The roll hoop obviously passed the minimum standard, but damn, if it collapses that easily, the standard needs to be raised
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What happened still would have ended up infinitely worse with a tall driver whose head is slightly higher than the halo.
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Nope. They have to be below a line that travels from the halo to the roll hoop diagonally.
Here he Ocon is in a 2022 car . His head/helmet certainly would be in danger of being dragged on the ground if the hoop fails him
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No he isn't. The amount of chassis that would need to break before his head is on the ground is so large and the force required is so large that if it broke, his head on the ground would be the least of his concern
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You mean like this or this. The body work was gone
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Did you even open the link at all? The responses literally show drivers with their heads above the halo.
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That's literally illegal according to regulations. No matter how tall, driver's helmet can't be higher than the imaginary line between roll hoop and halo. IIRC, there was even a gap accounted for, in that regulation. So, even if driver is tall, their head can't stick out if the car is upside down.
Well, maybe if there is a structural failure and that foam above the shoulders got loose, gravity can pull driver down closer to the ground. But height itself is not the concern.
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It literally disintegrated
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When a car disintegrates in a big crash, do you think that's a bad thing?
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Yes
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Congratulations on not understanding anything that the car industry has learned in the last 50 years then. Go drive a 1970s Mustang then.
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There are parts that are specifically meant to disintegrate (nose/front impact structure, side impract structures, rear impact structures) and parts that are not supposed to disintegrate. The primary roll structure in the airbox is one of those (alongside the Halo and the monocoque).
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So you want the roof of your car collapsing on you?
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After going through tarmac, gravel and a heavy impact at 200kmph, for 250m easily.
Although, there is an investigation going on, on how to improve it further. Most probably, we will see a switch to same material as halo, and maybe a design change. At the very least, it will result in load tests improved to consider this possibility.
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Don’t care what he says. Everyone saw what happened. We have eyes.
Edit: his excuse of ‘everything protected him after’ would not have worked for russell albon or ocon, who are taller. Zhou’s helmet scrapped the floor imagine if a teller person was pushed harder against it.
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Fail to me means didn't perform to specification. The specification will be evaluated and changed based on this I'm sure, but I don't think we can judge from afar whether it failed to do what it was designed to withstand.
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It’s a unique design alfa uses as well. So I’m not too sure.
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In the thread he responds to a question about the 3D printing and say multiple teams have 3D printed roll hoops. I don't know if the Alfa is unique in another way.
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Alfa is the only team using a blade-like rollover structure rather than a traditional hoop-design.
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When a car disintegrates in a crash, do you also say "it failed, we have eyes"?
It's still to be investigated, but it's entirely possible that the roll hoop absorbed a ridiculous amount of energy while being crushed / broken off, which in itself is a good thing.
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The roll hoop broken off is never a good thing, because the point of the roll hoop is to provide clearance height for driver’s head when it flipped over. In this case it was gone so the supposed clearance of driver’s head is gone, it’s fortunate that it happened to a shorter driver in Zhou that the secondary clearance (top of actual halo) happened to work, but in the case of a taller driver it wouldn’t have worked, which then would have caused a biiiiiiiiiig issue
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Taller drivers sit lower. They have to be below the halo.
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No. The top of the helmet has to be below a line drawn from the roll hoop to a point in front of the cockpit. Many drivers' helmets are higher than the rest, but still a legal driving position.
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They are very obviously higher up than zhou. Upside down you’re going to go behind the halo. ‘But they’re kept in place’ no they’re not. Porpoising.
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He’s not saying it didn’t fail, in a comment he said it failed when being dragged across the ground at speed but not on contact. I think his point is it isn’t designed to withstand that sort of situation and it succeeded at what it’s tested for. That’s all fine but in the end it wasn’t much help for most of the incident
Yeah that's true, should have reflected that in the title. I guess it's just that I see the finger being pointed at Alfa but I don't think we have the evidence to say it didn't work to spec (i.e. point the finger at the regs, not Alfa).
I think people don’t know or understand that there are multiple forces acting on a rigid body even under its own weight. Normal stress, shear stress and bending moments occur and he was sliding for a long time.
He got hit before he even reached the end of pit lane. So, distance from pole to first corner, plus gravel trap. Easy 250m distance. After basically getting whole 900kg car on one impact point. Yeah, that thing ain't surviving. I don't know why people think it should.