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Author Topic: Trojans take on engineering  (Read 17405 times)

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trojan

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Re: Trojans take on engineering
« Reply #60 on: July 11, 2009, 03:13:44 AM »
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island buggy

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Re: Trojans take on engineering
« Reply #61 on: July 12, 2009, 06:53:02 PM »
The problems with FEM analysis is that forces and angles still have to be assumed.  You pick a direction and a force and a input function and the software plot's your results.  Sure it will show you where the stress concentrations are but only for that particular angle of inpact.  In order to properly "design" an a-arm this way would take thousands of hours running simulations from all angles with varying loads.  The sum of all these results would have to be reviewed to determine the proper tradeoff's.

Building a set of arms and driving the car until it they break provides the same information as the program it just takes more work.  Lesson's learned during years of experience and testing will always be more valuable than a few weeks simulation with a computer.

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Offline fabr

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Re: Trojans take on engineering
« Reply #62 on: July 12, 2009, 07:24:32 PM »
My point  exactly. And welcome BTW Islander!
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"There can be no divided allegiance here.  Any man who says he is an American,
but something else also, isn't an American at all.  We have room for but one
flag, the American flag... We have room for but one language here, and that is
the English language... and we have room for but one sole loyalty and that is a
loyalty to the American people."
Theodore Roosevelt 1907

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 " You have all the right in the world to believe any damn thing you'd like, but you don't have the right to demand that I agree with your fantasy"

island buggy

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Re: Trojans take on engineering
« Reply #63 on: July 12, 2009, 08:41:55 PM »
Thanks, been lurking for awhile.  Currently got a pair of ST3's with some of Ricks touches in progress.  More of a winter project though summer's for golfin.
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Offline fabr

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Re: Trojans take on engineering
« Reply #64 on: July 12, 2009, 08:59:16 PM »
Well ,keep us updated if youu wish!
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"There can be no divided allegiance here.  Any man who says he is an American,
but something else also, isn't an American at all.  We have room for but one
flag, the American flag... We have room for but one language here, and that is
the English language... and we have room for but one sole loyalty and that is a
loyalty to the American people."
Theodore Roosevelt 1907

-----------------------------------------------------------
 " You have all the right in the world to believe any damn thing you'd like, but you don't have the right to demand that I agree with your fantasy"

trojan

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Re: Trojans take on engineering
« Reply #65 on: July 13, 2009, 01:43:57 AM »
Quote from: Masterfabr on July 12, 2009, 07:24:32 PM
My point  exactly. And welcome BTW Islander!

BULLSHIT (again) your point was that it's all WILD ASS GUESSES, which it is not. I take Islander's point and in fact it was considered in my opinion.
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trojan

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Re: Trojans take on engineering
« Reply #66 on: July 13, 2009, 01:51:07 AM »
Quote from: Island buggy on July 12, 2009, 06:53:02 PM
The problems with FEM analysis is that forces and angles still have to be assumed.  You pick a direction and a force and a input function and the software plot's your results.  Sure it will show you where the stress concentrations are but only for that particular angle of inpact.  In order to properly "design" an a-arm this way would take thousands of hours running simulations from all angles with varying loads.  The sum of all these results would have to be reviewed to determine the proper tradeoff's.

Building a set of arms and driving the car until it they break provides the same information as the program it just takes more work.  Lesson's learned during years of experience and testing will always be more valuable than a few weeks simulation with a computer.



Years of testing vs weeks of simulation are no where near comparable especially if you delude yourself as to what testing is (like some manufacturers) and call it a few laps in the car park outside the shed.
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Offline fabr

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Re: Trojans take on engineering
« Reply #67 on: July 13, 2009, 06:11:43 AM »
Quote from: Island buggy on July 12, 2009, 06:53:02 PM
The problems with FEM analysis is that forces and angles still have to be assumed.  You pick a direction and a force and a input function and the software plot's your results.  Sure it will show you where the stress concentrations are but only for that particular angle of inpact.  In order to properly "design" an a-arm this way would take thousands of hours running simulations from all angles with varying loads.  The sum of all these results would have to be reviewed to determine the proper tradeoff's.

Building a set of arms and driving the car until it they break provides the same information as the program it just takes more work.  Lesson's learned during years of experience and testing will always be more valuable than a few weeks simulation with a computer.


So,trojan,you disagree with this? All engineering has to be based on real world results. Real world results are what the engineering math is based upon. Engineering as shown in that statement IS based on WAG in one way or another.Assume(WAG) the wrong thing ,and you must assume some things, and the engineering goes out the window.But again ,trojan has shown me the path to trojan enlightenment for me to see the only true opinion that counts. Of course my opinion is once again BS since it is not in line with his opinion.  mm: bb:
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"There can be no divided allegiance here.  Any man who says he is an American,
but something else also, isn't an American at all.  We have room for but one
flag, the American flag... We have room for but one language here, and that is
the English language... and we have room for but one sole loyalty and that is a
loyalty to the American people."
Theodore Roosevelt 1907

-----------------------------------------------------------
 " You have all the right in the world to believe any damn thing you'd like, but you don't have the right to demand that I agree with your fantasy"

island buggy

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Re: Trojans take on engineering
« Reply #68 on: July 13, 2009, 12:58:10 PM »
I'm not saying that FEM doesn't have it's place.  If you are trying to shave pounds off a design to increase fuel economy or reduce manufacturing costs per piece.  Sure finite element is a great and useful tool.

Most of the stuff on this site will never reach mass production in the true sence of the word and therefore the design doesn't require cost optimization. 
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Offline fabr

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Re: Trojans take on engineering
« Reply #69 on: July 13, 2009, 01:02:53 PM »
Again I agree. You have experience with FEM?
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"There can be no divided allegiance here.  Any man who says he is an American,
but something else also, isn't an American at all.  We have room for but one
flag, the American flag... We have room for but one language here, and that is
the English language... and we have room for but one sole loyalty and that is a
loyalty to the American people."
Theodore Roosevelt 1907

-----------------------------------------------------------
 " You have all the right in the world to believe any damn thing you'd like, but you don't have the right to demand that I agree with your fantasy"

island buggy

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Re: Trojans take on engineering
« Reply #70 on: July 13, 2009, 01:58:59 PM »
We dealt with it a bit in school, I am a mechanical engineer in the aerospace industry and believe that all designs come with different criteria.  Aviation FEM is crucial to the final design of the aircraft.  Recreational buggy building, make it strong.  Break it, then make it stronger.
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Offline fabr

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Re: Trojans take on engineering
« Reply #71 on: July 13, 2009, 02:21:20 PM »
Again ,agreed.
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"There can be no divided allegiance here.  Any man who says he is an American,
but something else also, isn't an American at all.  We have room for but one
flag, the American flag... We have room for but one language here, and that is
the English language... and we have room for but one sole loyalty and that is a
loyalty to the American people."
Theodore Roosevelt 1907

-----------------------------------------------------------
 " You have all the right in the world to believe any damn thing you'd like, but you don't have the right to demand that I agree with your fantasy"

trojan

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Re: Trojans take on engineering
« Reply #72 on: July 14, 2009, 01:39:55 AM »
this thread came out of a professional build to differenciate between "engineered" and "drawn up".
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Offline fabr

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Re: Trojans take on engineering
« Reply #73 on: July 14, 2009, 08:06:58 AM »
Quote from: trojan on July 13, 2009, 01:43:57 AM
BULLSHIT (again) your point was that it's all WILD ASS GUESSES, which it is not. I take Islander's point and in fact it was considered in my opinion.
My point was that all engineering began with a WAG. Without those initial WAG there was no where to start engineering from in the first place. Call  BULLSHIT all you wish trojan.
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"There can be no divided allegiance here.  Any man who says he is an American,
but something else also, isn't an American at all.  We have room for but one
flag, the American flag... We have room for but one language here, and that is
the English language... and we have room for but one sole loyalty and that is a
loyalty to the American people."
Theodore Roosevelt 1907

-----------------------------------------------------------
 " You have all the right in the world to believe any damn thing you'd like, but you don't have the right to demand that I agree with your fantasy"

island buggy

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Re: Trojans take on engineering
« Reply #74 on: July 14, 2009, 10:37:52 AM »
Quote from: trojan on July 14, 2009, 01:39:55 AM
this thread came out of a professional build to differenciate between "engineered" and "drawn up".

Doug never stated he "engineered" these arms he designed them.  Where we are disagreeing is on what constitutes a designed set.  There is no black or white here its not Designed or Drawn Up.  There are levels of design all across the board.  As far as that goes, two different designs will have different design constraints.  Tensile stresses will be considered for one design, buckling for another, weight for one design cost for another.

I do understand that you are considering this as all or nothing.  It's engineered or it's not.  I'm just stating my opinion that design and engineering are not the same thing, design is the concept generation, inital fabrication and testing.  Engineering comes into play for optimizion of the design or preparing for production.
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