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 Post subject: Re: Stalker in accident
PostPosted: June 7, 2015, 8:40 pm 
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Mid-Engined Maniac

Joined: April 23, 2006, 8:26 pm
Posts: 6009
Location: SoCal
Returning to the cause of the accident, failure of the front suspension bracket, check out these pictures. These pics are from another of the same type of car, where the driver side lower A-arm bracket failed. The last two shots are of the opposite side of the same car, showing failure cracking well in progress on the lower A-arm bracket.

The point is, having brackets larger than the tubes they're welded to is bad news, made worse when the forces feed into them off-axis (the brackets don't "point" at the tube) which causes them to flex right along the HAZ. Seeing a failure on one side might be excused if a big pot hole was struck, but failure on both sides seems to suggest something more fundamental.

What we can all learn from this is to be aware of the possible consequences of using over-sized brackets, feeding them offset loads, and especially checking the car over after taking a big hit.

They're big pictures, so click on the links

http://www.midlana.com/Diaries/Current/ ... ilure1.jpg
http://www.midlana.com/Diaries/Current/ ... ilure2.jpg

Now compare the above picture with a picture of the same bracket off the car in question:
http://www471.pair.com/stalkerv/gallery ... alNumber=2
http://www471.pair.com/stalkerv/gallery ... alNumber=2

http://www.midlana.com/Diaries/Current/ ... ilure3.jpg
http://www.midlana.com/Diaries/Current/ ... ilure4.jpg

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 Post subject: Re: Stalker in accident
PostPosted: June 7, 2015, 10:14 pm 
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The voice of reason
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Thanks for those pictures, Kurt. The last two from your site show exactly what I was wondering about, part of the bracket cantilevered past the edge of the tube, putting a little flex into the part of the bracket in the HAZ zone. I would guess the car in this thread was well on the way to failure by the time that pot hole was run over, so it wasn't a real issue, just a distraction...

Which is why if you run on tracks and compete, looking your car over is a good idea. Not just going around and torqueing bolts all the time, but actually just looking at it. For me that works best if I pick different parts of the car on different days and look at that part more carefully. The idea is not to see what you always see, but to notice something different.

I learned this doing preflights when I used to fly. Every time I did the preflight I picked the next area from the previous preflight and looked a lot more carefully at it. One day I got down low and looked up under the cowl and saw that the nose gear was coming off the plane! It was held on by a clamp and both nuts were so loose I could see half the threads on the inside of the nut! :shock: That day, I won big!

The trick is try to look at the parts like they are not familiar. Carefll inspections are great, but just being in the habit of looking at your car when your standing near it or walking up to it can find lots of problems. You see people driving down the highway with half the air missing in a tire! Everyone can benefit from learning just to look at their car...

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 Post subject: Re: Stalker in accident
PostPosted: June 7, 2015, 10:45 pm 
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Mid-Engined Maniac

Joined: April 23, 2006, 8:26 pm
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Location: SoCal
Yeah this thread reminds me that I need to do exactly that, inspect every fastener and bracket more often.

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 Post subject: Re: Stalker in accident
PostPosted: June 7, 2015, 11:17 pm 
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Posts: 775
Two things, no, three things.

1) best wishes on a speedy and complete recovery. Reports like this are great learning opportunities for the rest of us.

2) impact absorbing seat foam is very common in the aviation industry. For one reliable source and some details on the products available see here http://www.afeonline.com/shop/dynafoam- ... thick.html

3) I live in an area where we experience a lot of freeze/thaw through the year, as many of the forum's members do, and as a result our roads are constantly full of potholes. See example of a Winnipeg street below. The reported accident caused by hitting one pothole certainly is cause for concern and caution if you drive a similarly bracketed car on our streets....just think of the abuse the chassis and suspension are taking during a daily drive. An idea that has been much discussed in the past but hasn't made its way into this thread yet is the color of paint used on the chassis, light color for ease of cracking inspections, black paint a la Colin Chapman to hide cracks.

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 Post subject: Re: Stalker in accident
PostPosted: June 8, 2015, 3:24 am 
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First off, I wish xcarguy the speediest possible recovery.

Regarding that method of bracketing the suspension pickup points, I've wondered why it isn't more common to at least add small gussets top and bottom to help support the overhung portion of the bracket...Or maybe even a fully boxed 'gusset' from an angle cut slice of rectangular/square tubing.

Regarding the impact absorption, this has helped me put 2 and 2 together with all that I've learned about infant/toddler car seat construction and materials over the past year or so...I'll now be integrating EPS into the construction of my seats.

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 Post subject: Re: Stalker in accident
PostPosted: June 8, 2015, 8:22 am 
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Location: West Chicago,IL
Quote:
Regarding that method of bracketing the suspension pickup points, I've wondered why it isn't more common to at least add small gussets top and bottom to help support the overhung portion of the bracket...Or maybe even a fully boxed 'gusset' from an angle cut slice of rectangular/square tubing.
We Locostusa'ers know this. And we often suggest adding full gussets. The subject comes up occasionally and is commented on new builders' build logs. This is why I immediately saw this on the Stalker. I wonder what other Stalker builders might think about checking their vehicles.

It is tough to accept that the frame you just spent good money on needs to be "fixed". At least that is what I would think. In "the book" this is the way it is done. Another reason not to expect a different approach is needed.

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 Post subject: Re: Stalker in accident
PostPosted: June 8, 2015, 8:25 am 
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Location: Fort Worth, Texas
Driven5 wrote:
First off, I wish xcarguy the speediest possible recovery.


Regarding the impact absorption, this has helped me put 2 and 2 together with all that I've learned about infant/toddler car seat construction and materials over the past year or so...I'll now be integrating EPS into the construction of my seats.


What's EPS?

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 Post subject: Re: Stalker in accident
PostPosted: June 8, 2015, 11:13 am 
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Location: Under the weather. (Seattle)
Expanded PolyStyrene

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 Post subject: Re: Stalker in accident
PostPosted: June 8, 2015, 1:51 pm 
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KB58 wrote:
No...

This foam, when used as roll bar or headrest padding, is an entirely different application then when used as a seat cushion. When you cinch down the shoulder belts, it imparts a steady load - unlike in a roll bar or headrest application. The steady load compresses the foam and makes it both harder and thinner. Now that so-called 1" foam is 1/2". As the foam compresses further during the race, the driver cinches down the belts again, and now that 1/2" foam is 1/4". This material is not the solution this thread is presenting it as. It's intended to be used exactly once - like when your helmet bashes into it during an accident. Consider how well the roll bar foam would work if you put dozens of zip ties along the bar, compressing the material before it's used in the event of an accident. That's exactly what's happening when you sit on the stuff and cinch down the belts. The foam works by compressing - being compressed before the fact makes it completely useless. A lot of misinformation here.
From what I've read so far, the extensive testing and subsequent recommendations/requirements from many top-tier professional racing series' seems to disagree with your opinions regarding SFI 45.2 foam. It's being used both as the impact absorbing material in more conventional seat shells, as well as being poured as the 'seat' itself in formula cars. It's a resilient material, meaning it should not continue compressing down under a relatively constant average pressure, while also allowing for continued use through multiple impacts. Apparently even a strapped down squishy organic body exerts a low enough pressure that it still retains superior impact absorption qualities for a given thickness relative to other available materials. The price can really add up on it though.

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 Post subject: Re: Stalker in accident
PostPosted: June 8, 2015, 3:48 pm 
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Joined: October 24, 2008, 2:13 pm
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Location: Carlsbad, California, USA
Looking at the photos Kurt (KB58) posted, this is convincing prima facie evidence that the bracket mounting approaches in the Book and many parts of the Hayes Roadster just are not adequate, at least not for a car driven in a high performance context. I never have liked them and do not plan to use them on my own build if I can find a way to avoid it.

It is sobering to read about this accident and does motivate me to look at what I can do to enhance driver and passenger safety on my own car.

Cheers,

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Damn! That front slip angle is way too large and the Ackerman is just a muddle.

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 Post subject: Re: Stalker in accident
PostPosted: June 8, 2015, 4:38 pm 
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Mid-Engined Maniac

Joined: April 23, 2006, 8:26 pm
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Location: SoCal
Driven5 wrote:
... It's being used both as the impact absorbing material in more conventional seat shells, as well as being poured as the 'seat' itself in formula cars...

Poured? Is this the same material? Used in seat side cushions and head rests, sure, but used as the primary constant load-bearing surface? If so, I wonder if that's because it's already being used for the rest of the seat, not because it has any magical properties.

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 Post subject: Re: Stalker in accident
PostPosted: June 8, 2015, 6:21 pm 
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Yes, poured. Like many foams, it would seem that this starts life as a liquid that sets up into the final 'solid' foam form. You can buy the chemicals to mix up a batch of this foam yourself, if you would like. In fact certain racing supply shops sell such kits specifically for creating the ultimate body hugging DIY racing seats.

Kirkey Racing wrote:
KIRKEY RACING SFI 39.1 CERTIFIED CUSTOM CONTAINMENT SEAT. Constructed from 5052 and aircraft grade aluminum for maximum strength. Easy mounting with pre punched multiple side mounting locations and pre-installed recessed shoulder mounts. All mounts NASCAR approved. Seat reinforced in all high stress areas. Accommodates all head and neck restraint systems. Contoured extended bottom to support lower back, hips and thighs .No square corners on bottom. Easy installation of leg supports (# 03300/# 03400-sold separately) Machined billet aluminum connector brackets. SFI 45.2 certified head surround is adjustable vertically and horizontally, padding meets NASCAR requirements. Accommodates all seat belt systems with precut openings in seat sides and bottom. SFI 45.2 certified padding in bottom of seat to pass NASCAR rules. Contoured high impact padding has built-in leg seperator for inner thigh support. Extra high impact padding on shoulders and rib area attached directly to seat. Cover sold separately. Optional padded leg separator available (# 99700) NOTE: Special seat to fit Asphalt Modifieds Part # 92000 Call for details.
I haven't looked into it deep enough myself, but supposedly NASCAR (among others) did a substantial amount of testing that subsequently led to adding the the above noted requirement.

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 Post subject: Re: Stalker in accident
PostPosted: June 8, 2015, 7:02 pm 
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Mid-Engined Maniac

Joined: April 23, 2006, 8:26 pm
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Location: SoCal
Hmm, the link above to the manufacturer, https://www.rollbarpadding.com/product/id-40
doesn't mention use as a seat bottom, and neither does the attached brochure. Maybe it works great, but I'm wary of any material not listed as a solution to a problem. The text you included is by a reseller of the material, so it's less certain what their motivation is.

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 Post subject: Re: Stalker in accident
PostPosted: June 8, 2015, 7:36 pm 
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Why not also question BSCI's "motivation" for providing barely a high level overview of their products on the web site and in their brochure?...Maybe this will help clarify Kirkey's explicitly stated motivations:

NASCAR Rule Book wrote:
All seat interiors must be lined with inserts and/or padding. It is recommended that a
minimum thickness of two (2) inches of SFI 45.2 insert/padding be used. It is recommended that the
padding meet the SFI 45.2 specification and display a valid SFI 45.2 label. All non-SFI 45.2
insert/padding materials must be 1/2 inch thick or less. No gaps or non-SFI 45.2 specification
approved material(s) may be present between the seat structure and driver’s uniform in the area
directly under the driver.
The area directly under the driver extends from the driver’s waist (belt line)
forward to the front edge of the sub-strap pass through holes, as well as extends five (5) inches to
both the left and right of the driver’s centerline. It is recommended, a minimum thickness of 3/4 inches
of insert/padding meeting the SFI 45.2 specification be used in this area directly under the driver.



Edit: Found the same foam in the pourable DIY kits with specific reference to "help manage the forces exerted on a driver's body during crashes" as a seat insert, and not just for head protection anymore.

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Last edited by Driven5 on June 9, 2015, 2:30 am, edited 1 time in total.

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 Post subject: Re: Stalker in accident
PostPosted: June 8, 2015, 9:09 pm 
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Posts: 160
Also, I agree with and extend my own best wishes on a speedy and compete recovery.

Now, about expanded polystyrene/styrofoam, etc. There is a big difference between foams and a LOT of compounding variables. As a point of reference, your helmet probably has eps as its core shock absorbing material. You can compress it with static loads, but it is very difficult, and here is why: EPS is a rigid closed cell foam with a pretty tough polymer making up the cell walls. Under normal compression, the small gas (CO2) bubbles/cells act as springs with a pretty high spring constant. The tough polymer means each cell is pretty strong spring, resisting rupture on its own, but the long range network of tough, cross linked polymer material resists deformation beyond a localized area, and along with billions of tiny gas springs, creates rigidity to relatively low stresses like seat belt tension.

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