Author Topic: Boxed Sheet Metal Components.  (Read 5776 times)

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Offline fabr

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Boxed Sheet Metal Components.
« on: June 05, 2012, 08:21:15 PM »
For quite some time I've read about ,watched the use of, and questioned the thickness of the sheet metal many are using for components such as a arms. For smaller ,lighter buggies such as the barra2da I see no issues at all but for a bit larger, midi size , I have serious doubts about the use of 16ga material I see sometimes used especially since I bent both lower a arms on my rorty R16 car made from 1.25 x .120 4130.
  Thoughts and opinions?
"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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"I fear the day that technology will surpass our human interaction. The world will have a generation of idiots" Albert Einstein  (IT'S OFFICIAL THAT DAY IS HERE NOW!)

Offline sandycrack

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Re: Boxed Sheet Metal Components.
« Reply #1 on: June 05, 2012, 08:29:17 PM »
Dont know abot the sheet, but my arms are 1.5 .120 CM with 20 " of travel and estimating the final weight at 2200.  What are you estimating the weight of your car?
You smell that?

Offline Lance-W

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Re: Boxed Sheet Metal Components.
« Reply #2 on: June 05, 2012, 08:32:54 PM »
If you look at the stress plots for the Barra2uda they prove that a properly designed (I hope it's yet to be beat upon) will be significantly stronger than a tube structure.  Almost all the big boy off-road trucks run boxed sheet metal arms.  They can't all be wrong...........there must be a reason they're not using tubes.  Now my driving style might be severe compared to others but the fact remains that they bent.  I even attempted to box the tubes on the single seater two different ways and they still bent, I'm now on the third set of tubed arms (at some point I'll probably retro-fit them with the new boxed design).    Scooter's wife Dawn's also bent.  He went to 4130 tube and additionally boxed them.  I don't know how the 4130 ones held up this season.  The first set of her's (mild steel) bent just like Samantha's............ 

Offline Lance-W

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Re: Boxed Sheet Metal Components.
« Reply #3 on: June 05, 2012, 08:38:40 PM »
Fabr,

Another thing to think about is that running in the sand is entirely different than running in the desert (you've spoke many times of the desire to run in the desert).  In the sand you support the weight of the buggy and it lands in a semi soft medium when it gets air.  In the desert it's like landing on asphalt every time you jump.  Add in the rocks and sometimes boulders that put themselves in your way and the impacts alone will take out the arms.  In my opinion and I'm sure some will disagree but the desert is a factor of 2 or 3 harder and more abusive than the sand is on a vehicle.

Offline fabr

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Re: Boxed Sheet Metal Components.
« Reply #4 on: June 05, 2012, 08:49:26 PM »
Dont know abot the sheet, but my arms are 1.5 .120 CM with 20 " of travel and estimating the final weight at 2200.  What are you estimating the weight of your car?
I'm 1800 with sand tires/wheels and 2000#with dirt tires/wheels.
"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

-----------------------------------------------------------
"I fear the day that technology will surpass our human interaction. The world will have a generation of idiots" Albert Einstein  (IT'S OFFICIAL THAT DAY IS HERE NOW!)

Offline fabr

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Re: Boxed Sheet Metal Components.
« Reply #5 on: June 05, 2012, 08:51:40 PM »
Fabr,

Another thing to think about is that running in the sand is entirely different than running in the desert (you've spoke many times of the desire to run in the desert).  In the sand you support the weight of the buggy and it lands in a semi soft medium when it gets air.  In the desert it's like landing on asphalt every time you jump.  Add in the rocks and sometimes boulders that put themselves in your way and the impacts alone will take out the arms.  In my opinion and I'm sure some will disagree but the desert is a factor of 2 or 3 harder and more abusive than the sand is on a vehicle.
we're in complete agreement.
"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

-----------------------------------------------------------
"I fear the day that technology will surpass our human interaction. The world will have a generation of idiots" Albert Einstein  (IT'S OFFICIAL THAT DAY IS HERE NOW!)

Offline fabr

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Re: Boxed Sheet Metal Components.
« Reply #6 on: June 05, 2012, 08:59:58 PM »
If you look at the stress plots for the Barra2uda they prove that a properly designed (I hope it's yet to be beat upon) will be significantly stronger than a tube structure.  Almost all the big boy off-road trucks run boxed sheet metal arms.  They can't all be wrong...........there must be a reason they're not using tubes.  Now my driving style might be severe compared to others but the fact remains that they bent.  I even attempted to box the tubes on the single seater two different ways and they still bent, I'm now on the third set of tubed arms (at some point I'll probably retro-fit them with the new boxed design).    Scooter's wife Dawn's also bent.  He went to 4130 tube and additionally boxed them.  I don't know how the 4130 ones held up this season.  The first set of her's (mild steel) bent just like Samantha's............
Again ,we agree . My point was I suspect 16ga mild will not hold up on a car the size/weight of mine. I don't mean to knock anyone's design but ,sorry engineer, I was skeptical when you posted your arms and now I'm really skeptical after bending mine. Engineers car is ,I think ,comparable in size/weight as mine. At any rate we're probably twice your cars weight. As for the big trucks ,I'm betting they use a bit thicker than 16 ga.
 I understand box section is stronger. Look at Mosebilt stuff. All his front arms are made from square tube,then boxed. That man builds some innovative stuff that works.
"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

-----------------------------------------------------------
"I fear the day that technology will surpass our human interaction. The world will have a generation of idiots" Albert Einstein  (IT'S OFFICIAL THAT DAY IS HERE NOW!)

Offline Lance-W

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Re: Boxed Sheet Metal Components.
« Reply #7 on: June 05, 2012, 09:51:03 PM »
Not saying 16GA (.063) is the answer for yours.  Obviously it would have to be sized appropriately.   I first modeled them at .120 sheet.  My stress guy told me twice "Go Thinner".  Changing the sheet thickness as a result of the stress plots is very easy.  They just get heavier the thicker you go  :)

I agree the big trucks use thicker material but then they have 600+ horsepower to push them thru the desert.

Offline Carlriddle

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Re: Boxed Sheet Metal Components.
« Reply #8 on: June 06, 2012, 05:50:37 AM »
My research and little knowlegde lead me to the idea that square material is stronger if the forces come straight in on flat side, if from the 90* corner they're weaker than same sized round.  Round is same from all around and thus better for the novice builder.  I'm guessing the boxed arms fit in that, but  drowning drowning.  If modeled and put thru the stress like Lance did (which was pretty damn cool) you could workout most weakness. 

I hope to see Engineer's but at this fall ride,  ;)
You can keep your CHANGE, I'd like to keep my DOLLAR.

Offline fabr

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Re: Boxed Sheet Metal Components.
« Reply #9 on: June 06, 2012, 06:01:41 AM »
Please understand that I'm NOT talking about the barea2uda. I AM saying that 16 ga will not hold up to serious or even casual use whether the sand or hardpack on a bigger heavier car . Sheet metal box structures can and are used very successfully on all size cars.  There is a huge difference tho  in the stresses a light small buggy suspension arm will see and what will be seen by larger heavier cars. In this topic,I'm not in the least considering small buggies. It is only about stuff that will be 1800# or so and larger such as engineers car. Again ,lance ,I am NOT talking about the barra2uda. IMO your design will work quite well and looks very very nice and professional. That said,I stand by my opinion.
"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

-----------------------------------------------------------
"I fear the day that technology will surpass our human interaction. The world will have a generation of idiots" Albert Einstein  (IT'S OFFICIAL THAT DAY IS HERE NOW!)

Offline fabr

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Re: Boxed Sheet Metal Components.
« Reply #10 on: June 06, 2012, 06:06:01 AM »
Problem with FEA,as I found out recently while playing aroiund with Alibre FEA is that it is Vvery much a high tech witchcraft tool. Works very well but the saying "garbage in=garbage out" really applies to FEA.
   How ,for example, can you determine the load applied to anything when you have no way to measure what that load is?
"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

-----------------------------------------------------------
"I fear the day that technology will surpass our human interaction. The world will have a generation of idiots" Albert Einstein  (IT'S OFFICIAL THAT DAY IS HERE NOW!)

Offline Lance-W

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Re: Boxed Sheet Metal Components.
« Reply #11 on: June 06, 2012, 06:09:14 AM »
I understand.  I was only using it as a comaprison, albiet a smaller ligther version of your car or Engineers.  It all scales up.  The heavier car the more the g-forces are a factor upon impact as a result of more mass hitting a solid unmoveable item.  Obviously the sheet thickness needs to be adjusted accordingly to the weight of the vehicle aka the final load it will see.

Offline Lance-W

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Re: Boxed Sheet Metal Components.
« Reply #12 on: June 06, 2012, 06:12:35 AM »
Problem with FEA,as I found out recently while playing aroiund with Alibre FEA is that it is Vvery much a high tech witchcraft tool. Works very well but the saying "garbage in=garbage out" really applies to FEA.
   How ,for example, can you determine the load applied to anything when you have no way to measure what that load is?

In my case it was easy.  I had bent enough arms in real life that I knew where they failed and I knew how much the buggy weighs.  I just took the old arms and modeled them and applied the load till they failed like in real life.  There I had a real life load and parameters to apply to the "new" arms or certainly a comparitive load.  Plus I have a very talented Stress person doing my anaylsis.  Shall we say an expert at the witchcraft :)

Offline fabr

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Re: Boxed Sheet Metal Components.
« Reply #13 on: June 06, 2012, 07:43:33 AM »
I fully agree with what you are saying. Additionally,box structures can be made with thinner materials but that does not necessarily mean lighter total weight.

  Example,1.5" round has a circumference of 4.71" vs 1.5" square being 6". A difference of 28% more material. so,material of approx .090 could be used in place of .120 and weigh the same.

  I would guess that the .090 square tube supported at both ends and a vertical load applied at the midpoint would support  more than the .120 round. With that said I also see advantages to box construction on things such as a arms when considering horizontal loads. I think I will take a page myself from Mosebilt and build a arms and the like from square tube ,plated where needed. Stronger for one thing and also much easier to attach tabs and such. IMO ,a no brainer to go square. Just need to be careful and consider the weight of square vs round when designing. Make sense?
  Biggest issue I see with using tube instead of sheet metal is that box construction is "in" and square tube is not. For sales appeal sheet metal is the way to go but from a fab standpoint of building one offs the tube works best I'd think.  I have a lot of respect for the out of the box thinking Mosebilt does and his willingness to do what he feels is best regardless of what others are doing.
"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

-----------------------------------------------------------
"I fear the day that technology will surpass our human interaction. The world will have a generation of idiots" Albert Einstein  (IT'S OFFICIAL THAT DAY IS HERE NOW!)

Offline Lance-W

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Re: Boxed Sheet Metal Components.
« Reply #14 on: June 06, 2012, 09:09:38 AM »
Just a quick weight comparison of 1 foot long peices for you.