Roll Cages

[OutCell]

I am designing a Roll Cage (Using CAD+FE) and trying out new materials for testing/analysis. Commonly used materials i found are:

• CDS Carbon Steel
• ERW Mild Steel
• DOM Mild Steel
• Cr (Chrome Molybdenum) Steel
• T-45
• 1020 Grade Mild Steel CDW

Anybody knows any other suitable material i could use? It would be highly appreciated

OutCell

[Alan Cherry]

What does the Blue Book say your'e allowed ? - assuming it's to be MSA/FIA compliant ?

[OutCell]

Originally Posted by Alan Cherry

What does the Blue Book say your'e allowed ? - assuming it's to be MSA/FIA compliant ?

Hi Alan. There is no book. I am searching light weight and strong materials that would be suitable for roll cages (For any book let us say ).

[Al Weyman]

Chrome Moly is meant to be the nuts isn't it?

[phoenix]

ERW is a definite no-no. The tube must be seamless and cold worked.

CDS is the minimum specification in the MSA Blue Book - BS EN 10305-1 CFS 3 BK is the spec. Minimum diameter and wall thicknesses are also specified in the Blue Book.

T-45 is permitted I believe but needs heat treating after welding as it becomes brittle around the welds. I believe the same goes for chrome moly but I believe that it is commonly used in the United States (not made in this country I don't believe).

I cannot comment on the other materials you mentioned.

(just re-read that - a lot of "believe" s in there!)

[terence]

T45 is the way to go,are you going to get it Certificated you'rself?

[brickkicker]

Found this if its any use

[OutCell]

Originally Posted by Al Weyman

Chrome Moly is meant to be the nuts isn't it?

I would just try the material specs in FE analysis, as part of my testing

Thanks mate

[OutCell]

Originally Posted by phoenix

ERW is a definite no-no. The tube must be seamless and cold worked.

CDS is the minimum specification in the MSA Blue Book - BS EN 10305-1 CFS 3 BK is the spec. Minimum diameter and wall thicknesses are also specified in the Blue Book.

T-45 is permitted I believe but needs heat treating after welding as it becomes brittle around the welds. I believe the same goes for chrome moly but I believe that it is commonly used in the United States (not made in this country I don't believe).

I cannot comment on the other materials you mentioned.

(just re-read that - a lot of "believe" s in there!)

Yeah. I will be making an FE model for each material for analysis and testing.. Thanks for your reply

[OutCell]

Originally Posted by terence bower

T45 is the way to go,are you going to get it Certificated you'rself?

No. It is for a project i am doing. I will make a finite element model for each material and then analyzing it. And hopefully find some new material that can be used for roll cages

Thanks for the reply mate

[OutCell]

Originally Posted by brickkicker

Found this if its any use
http://www.safetydevices.com/index.p...d=29&Itemid=49

Thanks mate Yeah i used this site to confirm some of the materials i saw around..

[Notso Swift]

Try 4130 as the correct number for CrMo steel
There are also exotic materials, namely Manganese Molybedamn Steel alloys.
Try and search Reynolds (though I have one of those feelings that part of the business is sold now. This is the stuff that is the grade up from superior to T45 (all of it is aero)

[OutCell]

Originally Posted by Notso Swift

Try 4130 as the correct number for CrMo steel
There are also exotic materials, namely Manganese Molybedamn Steel alloys.
Try and search Reynolds (though I have one of those feelings that part of the business is sold now. This is the stuff that is the grade up from superior to T45 (all of it is aero)

Thanks mate will do that

[crofty]

As I understand it, high chrome-moly, especially T91 can be a pain to weld properly.

[AU N EGL]

If this helps, this is some of what we in the states who run under the NASA banner must use:

NASA CCR wrote:
15.6.18 Roll Cage Tubing Sizes
For the purposes of determining roll bar tubing sizes, vehicle weight is as raced, but without fuel and driver. Note: There is an allowance of minus 0.010 inches on all tubing thicknesses.

Minimum tubing size for the roll cage is:
Up to 1500 lbs.
1.375” x 0.095” Chrome-moly / Seamless mild steel (DOM)

1501 - 2200 lbs.
1.500” x 0.095” Chrome-moly / Seamless mild steel (DOM)
1.500” x 0.120” ERW* (No issuance of log books for cars with ERW cages 04/30/03)
*Note- Specifications listed for reference for inspection of grandfathered vehicles.

2201 - 3000 lbs.
1.500” x 0.120” Chrome-moly / Seamless mild steel (DOM)
1.750” x 0.095” Chrome-moly / Seamless mild steel (DOM)
1.750” x 0.120” ERW* (No issuance of log books for cars with ERW cages 04/30/03)
*Note- Specifications listed for reference for inspection of grandfathered vehicles.

3001 - 4000 lbs.
1.750” x .120” Chrome-moly / Seamless mild steel (DOM)
No ERW allowed.

Over 4000 lbs.
2.000” x 0.120” Chrome-moly/Seamless mild steel (DOM)
No ERW allowed.

[zefarelly]

Originally Posted by phoenix

T-45 is permitted I believe but needs heat treating after welding as it becomes brittle around the welds. )

what do they do when they weld a cage in the car with the stuff then ?

I'm looking at designing a cage for a monocoque GRP car soon . . . . anyone recommend any decent glue

[terence]

Neutralize it with a large gas gun or bake the whole thing usually.

[jonners]

I read an interview once with Martin Short of Rollcentre fame and he said that T45 isn't a good option for roll cages - he said that once deformed it goes brittle so is likely to snap on a second impact unlike ordinary steel which is more [?] elastic.

[Insert usual caveat here about not being an engineer etc...]

Has always stuck in my mind - an honest comment from someone in a position to do well out of more expensive cages. That is, to the extent that I properly understood what he was saying in the first place.

I bought a lovely alloy cage about a year before they were banned...Thinking about it wasn't alloy banned for the same reason as T45 not being ideal as mentioned above?

[terence]

Thats a major problem with modern touring cars,big shunt and they are scrap because of using T45.

[phoenix]

I think the problem with T45 is that if it is truly to BS 4 T45 spec then it is supplied heat treated - hardened and tempered - as that is part of the BS specification. Welding will produce localised heating and therefore localised hardening, which requires tempering to get the area of the weld and it's surroundings back to the same condition as the rest of the tube work.

The main reason top teams use T45 is not for strength: the advantage is gained by using thinner tube, but meeting the the same strength requirements of 'lesser' carbon steel materials. This results in a weight saving.

The yield point and tensile strength of T45 is higher than that of carbon steel for the same cross sectional area. The reduction in wall thickness by the regs is down to the minimum yield and tensile strengths that a lesser steel would give.

However - and there is always a however!

I am very, very confident in stating that the torsional rigidity of steel is almost constant regardless of the alloy and directly proportional to the cross sectional area. Therefore, a cage made of THIN-WALL T45 with the same number of tubes and in the same position as a cage made from regular CDS will:

be lighter
have very similar tensile strength
have a very similar yield point
potentially be more brittle due to the hardening - particularly in the areas of welds.

Because the csa of the material is less, have LOWER torsional rigidity.

Because of this, more triangulation and gusseting will be needed to restore rigidity. I can only assume that all these extra bits add up to less weight than a regular, low carbon steel alloy cage but give the same or greater rigidity. Who knows, without extensive knowledge and ability to analyse the structures.

Maybe the guy who started this thread will be able to enlighten us all.

http://www.dstan.mod.uk/data/05/069/00000300.pdf

http://www.e-pipe.co.kr/eng/BS/6323-5.htm

[phoenix]

also....

http://www.roymech.co.uk/Refer_Docs/...eg_Steels.html

BS EN 10305-1 is the one we are interested in mainly.

[TWRv12]

Atko's crash in Japan looked very dodgy when the cage broke in number of places

[OutCell]

Originally Posted by AU N EGL

If this helps, this is some of what we in the states who run under the NASA banner must use:

NASA CCR wrote:
15.6.18 Roll Cage Tubing Sizes
For the purposes of determining roll bar tubing sizes, vehicle weight is as raced, but without fuel and driver. Note: There is an allowance of minus 0.010 inches on all tubing thicknesses.

Minimum tubing size for the roll cage is:
Up to 1500 lbs.
1.375” x 0.095” Chrome-moly / Seamless mild steel (DOM)

1501 - 2200 lbs.
1.500” x 0.095” Chrome-moly / Seamless mild steel (DOM)
1.500” x 0.120” ERW* (No issuance of log books for cars with ERW cages 04/30/03)
*Note- Specifications listed for reference for inspection of grandfathered vehicles.

2201 - 3000 lbs.
1.500” x 0.120” Chrome-moly / Seamless mild steel (DOM)
1.750” x 0.095” Chrome-moly / Seamless mild steel (DOM)
1.750” x 0.120” ERW* (No issuance of log books for cars with ERW cages 04/30/03)
*Note- Specifications listed for reference for inspection of grandfathered vehicles.

3001 - 4000 lbs.
1.750” x .120” Chrome-moly / Seamless mild steel (DOM)
No ERW allowed.

Over 4000 lbs.
2.000” x 0.120” Chrome-moly/Seamless mild steel (DOM)
No ERW allowed.

Awesome info. do you by any chance happen to know the specific naming of Chrome-moly/DOM/ERW materials so i can look up the specific properties to make an FEA and compare them?

Thanks again

[OutCell]

Originally Posted by phoenix

I think the problem with T45 is that if it is truly to BS 4 T45 spec then it is supplied heat treated - hardened and tempered - as that is part of the BS specification. Welding will produce localised heating and therefore localised hardening, which requires tempering to get the area of the weld and it's surroundings back to the same condition as the rest of the tube work.

The main reason top teams use T45 is not for strength: the advantage is gained by using thinner tube, but meeting the the same strength requirements of 'lesser' carbon steel materials. This results in a weight saving.

The yield point and tensile strength of T45 is higher than that of carbon steel for the same cross sectional area. The reduction in wall thickness by the regs is down to the minimum yield and tensile strengths that a lesser steel would give.

However - and there is always a however!

I am very, very confident in stating that the torsional rigidity of steel is almost constant regardless of the alloy and directly proportional to the cross sectional area. Therefore, a cage made of THIN-WALL T45 with the same number of tubes and in the same position as a cage made from regular CDS will:

be lighter
have very similar tensile strength
have a very similar yield point
potentially be more brittle due to the hardening - particularly in the areas of welds.

Because the csa of the material is less, have LOWER torsional rigidity.

Because of this, more triangulation and gusseting will be needed to restore rigidity. I can only assume that all these extra bits add up to less weight than a regular, low carbon steel alloy cage but give the same or greater rigidity. Who knows, without extensive knowledge and ability to analyse the structures.

Yes, that is right to what i read so far. The weight is almost the same for all but the strength is what differs between them. So having a smaller tube for Chrome-moly (Making it lighter) would be the same strength of a heavier DOM cage (Bigger tube).

http://www.ioportracing.com/faq/rollbar.htm

Maybe the guy who started this thread will be able to enlighten us all.

http://www.dstan.mod.uk/data/05/069/00000300.pdf

http://www.e-pipe.co.kr/eng/BS/6323-5.htm

That is what i am exactly trying to do for my project. Analysing different used materials and comparing them with other materials such as titanium etc.
That's why i am looking for the exact naming of the specific materials used such as ERW, DOM, Chrome-moly etc

Thank you all for your replies and sorry for being late, i didn't get any reply notifications

[AU N EGL]

Originally Posted by OutCell

Awesome info. do you by any chance happen to know the specific naming of Chrome-moly/DOM/ERW materials so i can look up the specific properties to make an FEA and compare them?

Thanks again

ERW = Electrical Resistance Welded = is NOT allowed. So dont even look at it

DOM = Drawn Over Mandral