Offroad-Express

Hi

Looking to shave some weight on the next cage I make for the 4wd . The national rally rules spec grade 250 pipe . This is at the low end of the scale and has a stength of about 60,000 psi I believe . At the top end of the scale is crome moly , 4130 , and in a normalized state is about 90,000 psi . Hence a 2.1mm wall tube is about as strong as a 3.2mm grade 250 pipe . But this is a bit pricey I am told , have not rung to find out yet , a bit gun shy .

What is there in between ?

Manz spec 38.1 x 2.5 wall tube but what is this , what are the spec's on it , strength weight per meter etc . It must come in other sizes etc .

What else do you guys recomemnd or have used in the past and what is its strength and weight .

Its always the a tough one it put an answer on as you don't want to gamble with saftey .

Cheers

Chris

Very good question Rotazuk. I'm keen on the answer for this as well, as I'm about to exo the wreck as project LION HEART continues.

ok as far as i'm aware steel and tube sell roll cage tubing (labeled as such)

wgtnnewbie wrote:ok as far as i'm aware steel and tube sell roll cage tubing (labeled as such)

umm. he knows where to buy tube

MANZ rollcage tube only comes in 38.1x2.5mm, it has a minium tensile strength of 350Mpa. It weighs 2.19kg/m. This is comply with MANZ and CAMS and ORANZ (need to double check about ORANZ)

The only other tube available in NZ (that i know of) is chromoly. Normal ERW tube is much weaker and not suitable.

There are lots of different pipes. and i have a spec sheet some where giving strengths, sizes etc.


I am writing an article that will be on my website within the next few weeks (along with lots of other articles) about this topic.

Hmmm
350 MPa converts to 50763 psi so somewhere my figures are not right .

From the Steel and tube page ERW tube looks like it has a tensile strength of 275 . They list a tube "ASTM A106 grade b" with a strength of 415 , that sounds better than roll cage tube , but the same as grade 250 pipe . Will try and find another source for the strength of that .

Chris

You are correct with your figures, roll cage tube is considered too lite by the national rally rules.

Motorsport NZ specifies this tube for car cages, as it is seamless, but you have to bend it in such away as there are no visible signs of crushing/crimping to maintain the strength.

I was going to make my cage from that tube thinking that it would be way better than what the national rally spec's where, but when i found out about the agricultural grade required, i was quite shocked

Rotazuk wrote:Hmmm
350 MPa converts to 50763 psi so somewhere my figures are not right .

From the Steel and tube page ERW tube looks like it has a tensile strength of 275 . They list a tube "ASTM A106 grade b" with a strength of 415 , that sounds better than roll cage tube , but the same as grade 250 pipe . Will try and find another source for the strength of that .

Chris

I think you'll find grade 250 pipe is 250Mpa - hence "grade 250". i.e, it has a nominal yield strength of 250Mpa.

Make sure you don't get mixed up between yield and tensile strength when comparing figures too.

Chromolly wil be about a bizillion times more expensive... OK, maybe only 3-5 times more expensive, but it should also be TIG welded, and stress relieved after welding.

Ben

give murray gorge a call in New plymouth hes normaly pretty good with his 4130 priceing

Chrome Moly is no good for 4wd cages. to expensive is the least of the problems. The correct method of welding and stress relieivng is what ramps the price up when getting things made out of it. One roll it its time ofr a new one

Ok, so as an aside which we have all you fancy university trained big-word-and-number-using peoples - what do you use - whats the best bang for buck tube to make something safe from? Obviously the rules for different competitions require a certain spec, but for a simple safe mud-plug truck what is acceptable?

I'm using 40mm med-wall bog-standard off-the-rack pipe for everything on the Hilux... nothing fancy, but its 3.2mm wall thickness and I figure that will make up for the inherent weaknesses of the welded seam. Weight isn't an issue since Hiluxes don't weigh bugger all anyway.

Sorry Chris, its not really a threadjack, just an aside to broaden the info a little...

Steve

Ok, so as an aside which we have all you fancy university trained big-word-and-number-using peoples - what do you use - whats the best bang for buck tube to make something safe from?

yea!!! there is light
Having built a few roll cages I use Southwards Tube as per recommendations from the Manz rules book. Its not the strenght of the steel tube being used. Its how the cage is constructed ,every bend should be free from deforms, and the cage be trianglulated.There is more but grab a MANZ motorsport rule book and use their ideas as a starting point.
Cheers DJ without a honuors degree in confussion and B..S

I am using MANZ tube for my cage. Like DJ said design is very important.
But you cant bend this tube in a bow and arrow style bender (some people might argue this) you need a pro tools style manual bender, speedworks bender or a full on hydraulic bender.

I understand SHIRMIN has its cage made from Cromoly - talking to Tony at Taupo 1000

DJ wrote:Having built a few roll cages I use Southwards Tube as per recommendations from the Manz rules book. ... There is more but grab a MANZ motorsport rule book and use their ideas as a starting point.
Cheers DJ without a honuors degree in confussion and B..S

Cheers DJ - good to see you back. Another fleeting visit to confuse us and then disappear for 6 more months without trace? I might have to grab a copy of that book for reference...

nz4x4 wrote:I am using MANZ tube for my cage. Like DJ said design is very important.
But you cant bend this tube in a bow and arrow style bender (some people might argue this) you need a pro tools style manual bender, speedworks bender or a full on hydraulic bender.

I understand that and have been trying to justify a pro-tools bender for quite a while... The thing thats always stopped me is the price of the dies on top of the bender here in NZ... Might have to revisit that and just bite the bullet... I'm well aware of the mess the crush benders make of good pipe or tube.

Chris, are you making your own cage? What are you using to bend it?

Steve

Try ringing Brian Howat @ Howat Engineering in Wellington 04 567 1471,
He helped write the nz4wda rollcage regs and has also worked at southwards where they make the supposed "rollcage tube", he has some quite interesting facts on it.

Cheers

Cheers DJ - good to see you back. Another fleeting visit to confuse us and then disappear for 6 more months without trace?

Hi
havn't disappeared just kicking back watching ..waiting,sending dissgusting , un PC txt's

worked at southwards where they make the supposed "rollcage tube",

thats interesting, Professor B/S, I thought that Southwards are a steel importer as there is nobody in NZ making steel tube to a desent standard. Please enlighten us!! Once again ...although the steel is a factor, the design is much more critical.....

Chrome Moly is no good for 4wd cages. to expensive is the least of the problems. The correct method of welding and stress relieivng is what ramps the price up when getting things made out of it. One roll it its time ofr a new one

Maybe JAFA ca n shed some light on this. Afer all hes just put a cage in his highly modified winch truck

finally some progress pics for ya'all.
Cage built by Octane Automotive in Palmy.
Main hoop is 1.75" 4340(Chromoly) rest is 1.5"

thats interesting, Professor B/S, I thought that Southwards are a steel importer as there is nobody in NZ making steel tube to a desent standard. Please enlighten us!! Once again ...although the steel is a factor, the design is much more critical.....

professor b/s ????? wtf?

Good to see we could not have a threat without name calling .

I have a reply from Fletchers on the strength of Blackwall pipe as spec'ed in the NZ4WDA rules . So in summary we have

Blackwaal pipe , BS1387-1985 etc etc at 320 MPA min ( thats 46 thou PSI tensile )
Manz rollcage tube at 350 MPA ( 50 thou )
ASTM A106 tube at 415 MPA ( 60 thou )
4130 crome moly at 615 MPA ( 90 thou ) in normalized cond .

So in my view Manz tube is not worth the effort due to the cost of a tube bender at ball park figure of $1000 . 4130 would be nice but cost would be high and since its a little hard to heat treat a whole cage can't get strength above 615 ish by the look of it .

I will have to look into to what grade this ASTM A106 is as it may be the only alternative depending on what size it comes in .

Steve sounds like you are using the pipe spec'ed , ie blackwall pipe , just out of coincidence .

Will left you know what I find out about the A106 tube unless someone pipes up .

Cheers

Chris

well i built the cage for the cruiser from 65mm schedule 50... mandrel bent.. and its sitting on the lawn..

DJ wrote:I thought that Southwards are a steel importer as there is nobody in NZ making steel tube to a desent standard. Please enlighten us!!

I realise this was probably meant in a more light-hearted fashion that it appears to have been taken - but here is your enlightenment... a direct quote from Atlas Metals website - the now-owners of what used to be Southward Engineering (Now NZ Tube Mills):

"In 2004 Atlas also purchased Southward Engineering in Wellingtion, a tube mill that produces mild steel, galvanised, aluminium, and stainless steel tubular products. In 2006 Southwards Engineering was renamed New Zealand Tube Mills."

Steve

i built my front axles out of 4130 in my 3/4 midget didnt have a tig welder so used gas welding and cromemolly filler never evr broke on me bent a few though as for reliveing i belive u dont have to doing it this way

Have a look here Chris, starting about page 61. Strengths for all sorts of grades of tube /pipe.

http://www.steelandtube.co.nz/downloads ... ire_DP.pdf

Ben

what pipe do i need to use to make a space frame for trials?, i am still confused and dont have a rule book yet.cheers
vaughan

Cheers Ben been through that .
Still looking like the seemless pipe , about 1/3 stronger than grade 250 , comes in pipe size ( for bender ) , just need to see if you can get it in sch 10 here . Its listed in the Easysteel catalouge so will find out next week .

Chris

so did anyone find out if we can use the manz roll cage tube

Random grave dig

nz4x4 wrote:I understand that and have been trying to justify a pro-tools bender for quite a while...

The bender is great, had 1', 1-1/2", 1-3/4" and 2" dies, take care of them and they will last a life time. Used seamless and then chrome moly. Only use ERW for minor brackes and non-structual pieces and parts.

Merc Cage

You have to b very carefull bending crome molly tubeing i used itf or the complet chassis and roll cage in my 3/4 midget and during a flip the roll cage where it was bent broke because the bending formers streached the tubeing that much it made it to week to hold together .
im not sure of what the speedway controll board came up with in regards to bending but i know they did something about it and it mentioned what formers you could use for speedway use.
From that day on iused tubeing from Southfort mills it is a certifyed rollcage tubeing that you can get from steel and tube.
If you have probs getting it let me know and i will contact someone i know that works there to get it for you.