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XR Build Thread

Posted by Thomas Kimsey 
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Keith Morison
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Re: XR Build Thread
June 08, 2016 04:23PM
Scrutineers are not there to give an opinion on the safety of a design, merely to say that the build meets the rules (which include FIA as an option) and that the build appears to have been done properly. (no-one is about to start x-raying the welds)
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Thomas Kimsey
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Re: XR Build Thread
June 08, 2016 06:25PM
Would this be the rule which makes this design illegal?

4.1.3 Reinforcement plates
These are plates welded to the bodyshell used for attachment of the cage, either by direct welding or via mounting
feet. Reinforcement plates must be a minimum of 1/8” thick, and have an area of 12 to 100 square inches, with a
minimum dimension on any side of 2.5” and a maximum dimension on any side of 12”. It is highly recommended that
these plates be formed to attach in more than one plane.
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Anders Green
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Re: XR Build Thread
June 08, 2016 08:47PM
Quote
Thomas Kimsey
My local NASA inspector wont accept what is on Skye's car (1st image)
That design appears to send a load into the side of a tube. My guess is that's the core of the issue.

Anyone can do a full FIA cage under NRS, and ignore all the rest of the entire roll cage appendix. It explicitly says so in the rules. Very simple. It's been this way for more than a decade.

Anders



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MarkHille
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Re: XR Build Thread
June 10, 2016 08:47AM
I don't know what you say when you say "tube" anders. Do you mean the shock tower?

I don't see how skye's car isn't meeting the fia regulation.

The only way I see it not meeting the NRS specification is if the reinforcement plate is smaller than 2.5" x 5". Is that the argument? It doesn't say it can't be bent. It actually encourages it to be more than 1 plane. There is no mention in the rules of shear or compression. I can understand that someone might not think it is the best design but I don't see how it doesn't meet the rule.

At what angle does compression become shear? It looks as if the backstay is in compression going into the shock tower and it is the tower that is in shear. Is that the real issue? According to Rally America they would prefer this. How is anyone to build a cage they can race both series in without issues if it always comes down to the individual scrutineer's opinion of safety?
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Thomas Kimsey
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Re: XR Build Thread
June 11, 2016 01:00PM
I still don't have any resolution on if its legal or not. Just that the scrutineer "has a problem" with it.
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john vanlandingham
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Re: XR Build Thread
June 11, 2016 01:39PM
Quote
Thomas Kimsey
I still don't have any resolution on if its legal or not. Just that the scrutineer "has a problem" with it.

Such a silly thing.. so much fappery....



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Keith Morison
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Re: XR Build Thread
June 11, 2016 02:40PM
What has the sanctioning body said about this?

If you are building to the rules, and it sounds like you are, and a scrutineer is blocking your car because of an unsubstantiated personal preference, the sanctioning body needs to step-in and remind the scrutineer of their responsibility and scope of powers.

Quite frankly, the position where scrutineers are 'approving designs' is one they really don't want to be in unless they are professional engineers with an active stamp and run the design through the calculations/FEA analysis to back-up their assessment.
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DexterVW
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Re: XR Build Thread
June 13, 2016 12:56PM
Quote
Not Trolling

Quite frankly, the position where scrutineers are 'approving designs' is one they really don't want to be in unless they are professional engineers with an active stamp and run the design through the calculations/FEA analysis to back-up their assessment.

i wouldn't be surprised with this one tongue sticking out smiley
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Thomas Kimsey
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Re: XR Build Thread
June 13, 2016 01:44PM
Quote
DexterVW
Quote
Not Trolling

Quite frankly, the position where scrutineers are 'approving designs' is one they really don't want to be in unless they are professional engineers with an active stamp and run the design through the calculations/FEA analysis to back-up their assessment.

i wouldn't be surprised with this one tongue sticking out smiley

I do have a solidworks model of the cage. Wouldn't be terrible to add in some sheet metal for the attachment points and run some FEA on it. Still don't thing that will help. I will probably just end up building to what the scrutineer wants as explanations of the design don't seem to help.
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NoCoast
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Re: XR Build Thread
June 13, 2016 03:32PM
I think Mike Hurst's Capri was this design too.



Grant Hughes
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Mad Matt F
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Re: XR Build Thread
June 13, 2016 04:18PM
Quote
Thomas Kimsey


I do have a solidworks model of the cage. Wouldn't be terrible to add in some sheet metal for the attachment points and run some FEA on it. Still don't thing that will help. I will probably just end up building to what the scrutineer wants as explanations of the design don't seem to help.

As active lurker of this thread... That's "fAWked" and your scrutineer should be drawn in (that's not drawn and quartered, merely reigned in).... No need to add the FEA, just a bit of calm-in sense....

Maybe just good beer and a chat? And say, well, I'd like the force of a big blow to the front of the cage to through the supporting dic (member) of the rear of the car, rather then resolved into the gas (atmosphere) that makes up the 22 gauge metal of my rear tire's mud guard...

winking smiley
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Robert Culbertson
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Re: XR Build Thread
June 13, 2016 05:24PM
Quote
Thomas Kimsey
Quote
DexterVW
Quote
Not Trolling

Quite frankly, the position where scrutineers are 'approving designs' is one they really don't want to be in unless they are professional engineers with an active stamp and run the design through the calculations/FEA analysis to back-up their assessment.

i wouldn't be surprised with this one tongue sticking out smiley

I do have a solidworks model of the cage. Wouldn't be terrible to add in some sheet metal for the attachment points and run some FEA on it. Still don't thing that will help. I will probably just end up building to what the scrutineer wants as explanations of the design don't seem to help.

Anyone can make pretty color plots with FEA. By changing element type and size you could make a bad design actually pass.
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Thomas Kimsey
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Re: XR Build Thread
June 13, 2016 07:41PM
Quote
Robert Culbertson
Quote
Thomas Kimsey
Quote
DexterVW
Quote
Not Trolling

Quite frankly, the position where scrutineers are 'approving designs' is one they really don't want to be in unless they are professional engineers with an active stamp and run the design through the calculations/FEA analysis to back-up their assessment.

i wouldn't be surprised with this one tongue sticking out smiley

I do have a solidworks model of the cage. Wouldn't be terrible to add in some sheet metal for the attachment points and run some FEA on it. Still don't thing that will help. I will probably just end up building to what the scrutineer wants as explanations of the design don't seem to help.

Anyone can make pretty color plots with FEA. By changing element type and size you could make a bad design actually pass.

Yes, any tool can be misused if you do not know how to use it, whats your point? Also there is no way a cage design would be allowed on FEA designs alone in the US. I was just pointing out that an engineering tool that could be used to help prove that this design is legitimate would not be helpful in this case. I will ask the scrutineer more blatantly tomorrow "Does this not meet the NASA rules".
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john vanlandingham
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Re: XR Build Thread
June 13, 2016 07:57PM
Quote
Thomas Kimsey
Quote
Robert Culbertson
Quote
Thomas Kimsey
Quote
DexterVW
Quote
Not Trolling

Quite frankly, the position where scrutineers are 'approving designs' is one they really don't want to be in unless they are professional engineers with an active stamp and run the design through the calculations/FEA analysis to back-up their assessment.

i wouldn't be surprised with this one tongue sticking out smiley

I do have a solidworks model of the cage. Wouldn't be terrible to add in some sheet metal for the attachment points and run some FEA on it. Still don't thing that will help. I will probably just end up building to what the scrutineer wants as explanations of the design don't seem to help.

Anyone can make pretty color plots with FEA. By changing element type and size you could make a bad design actually pass.

Yes, any tool can be misused if you do not know how to use it, whats your point? Also there is no way a cage design would be allowed on FEA designs alone in the US. I was just pointing out that an engineering tool that could be used to help prove that this design is legitimate would not be helpful in this case. I will ask the scrutineer more blatantly tomorrow "Does this not meet the NASA rules".

Precedent evidently means nothing..maybe phrase it "what is it specifically in Fords design used for years in WRC that they did in error and that you will not approve?

Of course I would love to ask "when you encountered these specific set ups in the past what did you make them do to get approval"



John Vanlandingham
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CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.
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Robert Culbertson
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Re: XR Build Thread
June 14, 2016 05:11PM
Quote
Thomas Kimsey
Quote
Robert Culbertson

Anyone can make pretty color plots with FEA. By changing element type and size you could make a bad design actually pass.

Yes, any tool can be misused if you do not know how to use it, whats your point? Also there is no way a cage design would be allowed on FEA designs alone in the US. I was just pointing out that an engineering tool that could be used to help prove that this design is legitimate would not be helpful in this case. I will ask the scrutineer more blatantly tomorrow "Does this not meet the NASA rules".

No real point to be made, and I'm certainly not trying to ruffly any feathers here. I'm just not sure of your experience with FEA or FEA within Solidworks. (hence my comment about changing element type and size, which are only 2-variables of the many that you could change).

It could be useful in comparing the two designs side by side, but looking at absolute strain values of a complex structure without an FEA study and validation is not very accurate, in my opinion.
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