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 Post subject: Re: Stalker in accident
PostPosted: November 23, 2015, 8:51 pm 
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BHRmotorsport wrote:
geek49203 wrote:
To dust off this topic...


Plus we need to ask xcarguy how his recovery is progressing.


Bill,

Thanks. All things considered, my recovery is progressing well.


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 Post subject: Re: Stalker in accident
PostPosted: December 10, 2015, 4:25 am 
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I just came across this thread; I'm not sure how I missed it. I have given a lot of consideration to crashing, but as mentioned, vertical drops never really factored in. I seem to recall seeing seats that had a tube frame perimeter with wide, thick nylon straps (like towing straps) interwoven, creating a taut hammock. This was then covered with foam and upholstery. Seems that this may give the sort of deceleration that we are seeking while remaining sufficiently rigid under normal events. Nylon is amazing at smoothing impulse and absorbing energy all while remaining structurally sound.

Given your reply, I'm assuming you're still on the non-surgical recovery. It's very personal, and I don't mean to pry; I just want to wish you the best.

From my view, you attend HPDEs for pleasure. This means the loss of 'mental edge' and driving slower won't matter. If you're like me, you just need to get out there and feel the car work beneath you, the speed and the lap times are inconsequential. I've come to the conclusion that going down the rabbit hole of slicks and aero and making the machine faster doesn't improve the experience; it just increases the risk. There is some part of our nature that equates the extra risk and the associated adrenaline with a more pleasurable experience, but can we instead find a more complete happiness from pursuing perfection without increasing risk?

Wow. I'm going to bed now before my philosophical ranting gets any worse.


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 Post subject: Re: Stalker in accident
PostPosted: February 1, 2016, 11:40 pm 
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Not sure how many of you guys are following Mark Ortiz's monthly newsletters (which are great btw). I took the liberty of emailing him regarding this incident because it affects us all. He answered with his most recent newsletter (which is awesome! Thanks for the input Mark!)

I've not had a chance to read it in depth yet, but here it is:

http://www.auto-ware.com/ortiz/ChassisN ... er2015.htm

Cheers.

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 Post subject: Re: Stalker in accident
PostPosted: March 3, 2016, 11:37 am 
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I did some digging around in the USAC sprint/midget scene after this thread started. They have a (for lack of a better word) cushion that is supposed to prevent injuries like this. You know, all of the vendor's claims about gov't aircraft specs and stuff.

Trouble is that no one seems to have any testing data in the actual use. But no one wants to be the first to go on record and say, "Hey, this might not work."

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 Post subject: Re: Stalker in accident
PostPosted: March 3, 2016, 1:55 pm 
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C10CoryM wrote:
Not sure how many of you guys are following Mark Ortiz's monthly newsletters (which are great btw). I took the liberty of emailing him regarding this incident because it affects us all. He answered with his most recent newsletter (which is awesome!
Indeed it is, and I love everything about it except the beginning, where he describes this incident as...

A fellow Locost driver had a relatively minor incident (caused by chassis bracket failure) on a road course where he ended up with a severe back injury.

...which is not fair to the many Locost builders, who build with care and without overhanging suspension brackets.

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 Post subject: Re: Stalker in accident
PostPosted: March 3, 2016, 11:15 pm 
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JackMcCornack wrote:
C10CoryM wrote:
Not sure how many of you guys are following Mark Ortiz's monthly newsletters (which are great btw). I took the liberty of emailing him regarding this incident because it affects us all. He answered with his most recent newsletter (which is awesome!
Indeed it is, and I love everything about it except the beginning, where he describes this incident as...

A fellow Locost driver had a relatively minor incident (caused by chassis bracket failure) on a road course where he ended up with a severe back injury.

...which is not fair to the many Locost builders, who build with care and without overhanging suspension brackets.



Well then I guess you like Mark, and dislike me, because that's who he is quoting there :lol:
I'm not sure how you got more out of that quote. It doesn't say anything about other Locost builders, or the quality of their cars. It only states that a chassis bracket failed and caused this incident. Is this not correct? Or is it that I lump non-book cars in as Locosts?

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 Post subject: Re: Stalker in accident
PostPosted: March 3, 2016, 11:23 pm 
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I think Jack is pointing out that the author described the car as a locost. The Stalker is a kit, not a locost. Describing a manufactured car as a locost impugns scratch builders.

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 Post subject: Re: Stalker in accident
PostPosted: March 4, 2016, 2:00 am 
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Exactly right, Omterry...but after thinking about this issue I have something to add.

The Stalker and Locost are two very different cars with similar appearance. The bracket failure (fatigue in the bracket overhang) is peculiar to the Stalker design. The Stalker folks have not corrected Mark's post quoting you, C10CoryM, so I guess they don't mind too much if people think it's a Locost problem rather than a Stalker problem.

A Stalker is not a non-book Locost, it is a Stalker. Stalkers generally have larger engines than Locosts, and the Stalker chassis is made from larger tubing than a Locost, and the Stalker is all around heavier and stronger than a Locost, except that sometimes during hard driving, the suspension attachment brackets bust off the chassis. In my opinion, responsible behavior would be to let every Stalker owner know which brackets need to be inspected daily (and possibly more often for autocrossers and track cars) to avoid catastrophic failure. That does not seem to be what is happening. In fact, I googled <stalker bracket failure> and <locost bracket failure>and the <only> forum I found that correctly identifies this as a Stalker is good ol' LocostUSA.

So C10CoryM, maybe you should go back to Mark and ask him to correct that name for you. A better informed Stalker driver is a safer Stalker driver.

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 Post subject: Re: Stalker in accident
PostPosted: March 4, 2016, 12:12 pm 
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While I agree with Jack about a Locost homebuilt chassis (whatever that really is. There are so many variations and deviations) vs a Stalker kit, it does remind all of us to give a very close inspection of our entire car as we come out of hibernation this Spring and even a few times during this driving season.

Many of us now know that the rear bracket design in a "book" chassis is not even close to being "good" let alone "ideal". There are too many examples of failures here in the USA, back in the UK and worldwide. We know how to "make it right". But not all Locost builders know about this common failure, or built using "good practice". Did they (we) apply that gained knowledge to all the suspension parts? The only way to know is to inspect our cars. Evidently the Stalker designers didn't know.

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 Post subject: Re: Stalker in accident
PostPosted: March 4, 2016, 8:18 pm 
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I had decided I was not going to post in this topic (like aerodynamics discussions) but this keeps coming up.

Imho, it is apparent from the xcars gallery pics that the front lcap bracket forward flange was cracked before running off the track, based on the rust I see in the crack, the condition of the right (opposite) side bracket, and the video. Miner’s rule of cumulative fatigue.

There are a number of reasons as to how the bracket could have been cracked previously. Some of those reasons are why there is generally no warranty on parts used for racing. For street use, I don’t think there is anything wrong with the design, but it could be improved slightly, again, imho. I’ve suggested that the control arms should not be stronger than the frame. At least with a tweaked control arm, the driving characteristics will change (versus just a crack in a weakened bracket that will only grow due to reduced cross section) and the driver will probably pit.

Imho, any car put into racing use will see failures of some kind. Consider also that non-compliant bushings, particularly with steel washers on each side to tighten it up further will see higher peak loads than a production car bonded rubber bush with greater wall thickness.

Regarding Ortiz, one way to provide some spinal protection from vertical impacts is to design the seats to be 2 inches deeper with 2 inches of Styrofoam below the seat cushion. Then it will move with the seat and belt mounts will not be affected. Another way to help is to ensure there is a reasonable amount of suspension travel with progressive bump stops.

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 Post subject: Re: Stalker in accident
PostPosted: March 4, 2016, 11:16 pm 
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JackMcCornack wrote:
Exactly right, Omterry...but after thinking about this issue I have something to add.

The Stalker and Locost are two very different cars with similar appearance. The bracket failure (fatigue in the bracket overhang) is peculiar to the Stalker design. The Stalker folks have not corrected Mark's post quoting you, C10CoryM, so I guess they don't mind too much if people think it's a Locost problem rather than a Stalker problem.

A Stalker is not a non-book Locost, it is a Stalker. Stalkers generally have larger engines than Locosts, and the Stalker chassis is made from larger tubing than a Locost, and the Stalker is all around heavier and stronger than a Locost, except that sometimes during hard driving, the suspension attachment brackets bust off the chassis. In my opinion, responsible behavior would be to let every Stalker owner know which brackets need to be inspected daily (and possibly more often for autocrossers and track cars) to avoid catastrophic failure. That does not seem to be what is happening. In fact, I googled <stalker bracket failure> and <locost bracket failure>and the <only> forum I found that correctly identifies this as a Stalker is good ol' LocostUSA.

So C10CoryM, maybe you should go back to Mark and ask him to correct that name for you. A better informed Stalker driver is a safer Stalker driver.


I wasn't aware the Locost name held such pedigree. If following Ron Champion's book is what makes a Locost, very few people own one. I certainly don't. Those that do have similar poorly supported brackets as the Stalker, and other known flaws. Far as I am concerned, if it looks remotely like one and isn't designed/built with professional engineers; it's a Locost. If I wanted to be precise, maybe the Stalker would be a Locost-Kit-Car. The Stalkers were designed/built by some guy in his backyard.... no different than me. The fact that they have problems is proof of this. Even though they are selling them for profit, they are still just car guys building similar cars to me and having fun with them. I'm all for that. Their company is growing, which is great, and maybe soon I will consider them to no longer be "Locosts".

I couldn't care less about names, politics, or what to call what car. I'm just here because I enjoy light-weight, fast cars. Stalkers included. I won't discuss this further because this topic is not related to this thread, and because I truly do not care about the semantics of "Locost".

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 Post subject: Re: Stalker in accident
PostPosted: March 5, 2016, 6:25 am 
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rx7locost wrote:
...it does remind all of us to give a very close inspection of our entire car as we come out of hibernation this Spring and even a few times during this driving season. [snip] Did they (we) apply that gained knowledge to all the suspension parts? The only way to know is to inspect our cars.
Absolutely right, Chuck. I do daily suspension inspections because the suspension is the place where a component failure can kill you. I check my suspension at least ten times as often as I check my oil--an engine failure may have you coasting to the side of the road, a suspension failure may have you darting into oncoming traffic. That is one area where the Se7en style beats full bodies--the open architecture makes it lots easier to preflight.
Miatav8,MstrASE,A&P,F wrote:
lmho, it is apparent from the xcars gallery pics that the front lcap bracket forward flange was cracked before running off the track, based on the rust I see in the crack, the condition of the right (opposite) side bracket, and the video.
I share that opinion. While the final failure was pretty much instantaneous, it seems to have gradually worked its way to the failure stage, and during the time it was weakened but holding, some of the damage was probably visible. A good reminder to inspect thoroughly and inspect often.
C10CoryM wrote:
I wasn't aware the Locost name held such pedigree.
Oh, it doesn't. Locosts are all over the place. A Locost is an inexpensive scratch-built sports car, inspired by Ron Champion's book, which was inspired by the Lotus Seven. The Stalker is the one with the pedigree. It is a branded, professionally manufactured kit car, and if you were building and selling Locosts and calling them Stalkers, I'm confident the Stalker folks (or their attorneys) would have words with you.
C10CoryM wrote:
Far as I am concerned, if it looks remotely like one and isn't designed/built with professional engineers; it's a Locost. The Stalkers were designed/built by some guy in his backyard.... no different than me. The fact that they have problems is proof of this.
I don't know the Stalker designer's credentials, but I know professional engineers make mistakes too.
C10CoryM wrote:
I couldn't care less about names, politics, or what to call what car...this topic is not related to this thread...I truly do not care about the semantics of "Locost".
In my heart of hearts, I'm with you on this (for example, I can't tell a Ford from a Chevy without looking at the badges, and I generally just call them "cars"). However, if we want to encourage Stalker drivers, as well as Locost drivers, to inspect their suspension closely and often, we should acknowledge that they care about names even if we don't. When a Stalker (or Caterham) driver reads about a Locost suspension failure, they think Not My Circus, Not My Monkeys--they don't drive Locosts so it's not their problem. So in this case, it might be better to call a spade a spade, instead of a club, man.

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 Post subject: Re: Stalker in accident
PostPosted: March 5, 2016, 9:43 am 
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Not My Circus, Not My Monkeys--they don't drive Locosts so it's not their problem. So in this case, it might be better to call a spade a spade, instead of a club, man.


:rofl: First time I've heard the monkey expression.

As Jack implies some of our problem is we don't really have a word like "clubman" for these cars that's more generic than an actual model.

I use lowercase locost to represent what a lot of people on our site build and uppercase Locost for things that are following book or closely book style.

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 Post subject: Re: Stalker in accident
PostPosted: March 5, 2016, 10:47 am 
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JackMcCornack wrote:
Miatav8,MstrASE,A&P,F wrote:
lmho, it is apparent from the xcars gallery pics that the front lcap bracket forward flange was cracked before running off the track, based on the rust I see in the crack, the condition of the right (opposite) side bracket, and the video.
I share that opinion. While the final failure was pretty much instantaneous, it seems to have gradually worked its way to the failure stage, and during the time it was weakened but holding, some of the damage was probably visible.



You're both wrong. The bracket wasn't damaged prior to my hitting the pothole...not humble opinion, fact.


JackMcCornack wrote:
. . . In my opinion, responsible behavior would be to let every Stalker owner know which brackets need to be inspected . . .



The bracket design on the original (Classis) Stalker chassis was addressed by the Company several years ago.


If a moderator can lock this thread, I respectfully ask that they do so....it's long overdue.


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 Post subject: Re: Stalker in accident
PostPosted: March 5, 2016, 3:25 pm 
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SOME STUFF FOR DESIGNING IN CRASH RESISTANCE. SORRY ABOUT THE CAPS.

FINDING THE MINIMUM REQUIRED DISTANCE TO STOP A MOVING BODY UNDER A MAXIMUM ALLOWABLE g FORCE USING AN IDEAL ENERGY ABSORBER (CRUMPLE ZONE) WHERE FORCE IS CONSTANT OVER DISTANCE

FROM PHYSICS:

IN AN IDEAL ENERGY ABSORPTION SYSTEM (CRUMPLE SYSTEM), FORCE WILL BE CONSTANT OVER DISTANCE.
THEN THE ENERGY ABSORPTION CAPACITY OF THE SYSTEM IS EQUAL TO MxGxH.
WHERE M = MASS, SLUGS = WEIGHT/32.2
G = 32.2 FPS^2
H = DISTANCE, FEET

A MOVING BODY (CAR, DRIVER OR JESUS STATUE ON THE DASH) TRAVELS WITH A KINETIC ENERGY OF 0.5 M x V^2.
WHERE V = VELOCITY, FEET PER SECOND (FOR EXAMPLE 100 MPH = 147 FPS)

EQUATING THE TWO AND FIDDLING AROUND GETS YOU:

THE DISTANCE REQUIRED FOR THE IDEAL SHOCK ABSORPTION SYSTEM TO DECELORATE A BODY UNDER A SPECIFIED FORCE IN g’s IS EQUAL TO M x VELOCITY SQUARED / ALLOWABLE FORCE IN g’s


EXAMPLE:

I WANT TO MAKE A SHOCK ASSEMBLY CRUMPLE ZONE THAT WILL PROTECT MY SUITE ASS IN A 100 MPH HEAD ON COLLISION. I KNOW FROM MYTHBUSTERS THAT MORE THAN ABOUT 10 g’s WILL CROAK ME. SO MY CRUMPLE ZONE LENGTH MUST BE EQUAL TO (0.5/G) x VELOCITY SQUARED / ALLOWABLE FORCE = [(0.5/32.2) x 147 SQUARED] / 10 g’s = 33.5 FEET.

THIS IS FOR A DIRECT HIT. USE GEOMETRY FOR RESULTS AT DIFFERENT COLLISION ANGLES. ALSO, THIS IS FOR AN IDEAL ENERGY ABSORBER. ADD 10 TO 20 PERCENT FOR REALITY. GOOD RACE SHOCKS (AND TRUCK SHOCKS) ARE AROUND 90 PERCENT EFFICIENT FOR CONSTANT FORCE OVER DISTANCE CRITERIA.


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