Rollcage Design/materials

nz4x4 · Post by **nz4x4** » Tue Sep 05, 2006 3:19 pm

Hi guys, just a quick question. Is their anything wrong with the strength/design of this cage or with the materials i am intending to use?
Its for a SWB MK Patrol.

Cheers

doddzee · Post by **doddzee** » Tue Sep 05, 2006 3:40 pm

Looks as though it meets ORANZ specs so it should be sweet. Are you going to have enought head room, That will probly be a problem area in my GQ.

You may find it hard to get the 51mm main hoop in there any may be better off going for something smaller in diameter with a larger wall thickness.

Wearnt you going to go for an Exo?

GQTROL · Post by **GQTROL** » Tue Sep 05, 2006 5:30 pm

Sam,
That cage will meet NZFWDA, MANZ and CCDA requirements. For it to meet ORANZ requirements, the foot plates on the main hoop need a twin lug connection to attach it to the chassis.

Make sure the main hoop is no more than 150mm behind the occupant's heads and that you've got 90mm clearance from the top of their helmets to the top of the cage.

Awesome piece of work dude!

nz4x4 · Post by **nz4x4** » Tue Sep 05, 2006 6:13 pm

i was going for an exo but i would then have to build a cargo barrier and mounting points for harnesses. So i am going to try and kill 2 birds with one stone.

Up untill a few weeks ago i also though i would have a problem with head room, but have since removed the head lining and gained 30mm of head room. I am also making new seat mounts for my buckets that are 30mm lower (was sitting up too high)

GQTROL: When you say twin lug construction for the main hoop, do you mean: the main hoop bolts through the body to another peice of plate that is attached to the chassis via another small peice of tube and a plate? Like in this photo?

If not, could you please enlighten my primitive mind on what a twin lug construction is?

GQTROL · Post by **GQTROL** » Tue Sep 05, 2006 6:25 pm

Twin lug connection is a flexible (and removable) joint at the point where you've got the plate attaching to the chassis. See Fig 4 in the back of the ORANZ manual.

The body-to-chassis connection you've got there has a bush welded on the end of it (think of a bush with rubbers like in the end of your leaf springs). A bolt goes through the centre of the bush to end plates which are welded to a base plate, which is then welded / bolted to your chassis. Thats a messy description, ORANZ manual shows it better.

doddzee · Post by **doddzee** » Tue Sep 05, 2006 6:25 pm

http://www.oranz.co.nz/artman/uploads/o ... k_2006.pdf

Page 32

nz4x4 · Post by **nz4x4** » Tue Sep 05, 2006 6:40 pm

Oh got you now!

So i would still have a plate, but rather than weld the tube to it i would have to 6mm pieces that are welded on it at right angles and then the bush on the end of the tube would bolt to that.

Will do a detail drawing to post up just to make sur ei have the right idea.

doddzee · Post by **doddzee** » Tue Sep 05, 2006 6:40 pm

Are you sure that it will meet NZFWA rules GQ TROL?

There rules state that -
over 1500kg - min 40 NB max unsuported span 1600mm
over 2000kg - min 50 NB max unsuported span 1800mm

When i enquired about it those sizes were required over the hole cage not just the main hoop.

GQTROL · Post by **GQTROL** » Tue Sep 05, 2006 6:48 pm

Winch challenge events currently require 4-point cage to NZFWDA regs. That is, a main hoop and two longitudinal rear stays of 50mm dia.

Everything else is 38.1mm dia as per MANZ and ORANZ.

If winch challenge rules go to 6-point cage to NZFWDA regs, then yes it all needs to be 50mm dia.

nz4x4 · Post by **nz4x4** » Tue Sep 05, 2006 7:13 pm

Ok, so is this correct?

There does seem to be a few problems with the materials needed for NZFWDA. 50mm NB will be closer to 54-56mm OD which seems to be an overkill. I may be wrong, but Shermin only has 1.5" OD chromoly which wouldnt comply with NZFWDA regs. I think NZFWDA needs to have a re-think about the cage requirements when it comes to materials giving clearer and more definitive answers.

I will post up my final design (when we sort it out) on Sooty's forum and see what Mike and Howard say and then report back.

callum007 · Post by **callum007** » Tue Sep 05, 2006 7:43 pm

i know its not that important but isnt overkill better than dead?? Im having my 60mm o.d schedule 40 pipe (4.75mm wall) bent at the moment.

2 main hoop and all lateral supports will be of same pipe

welded to 10mm plates. with 12mm cap screws between plates..

nz4x4 · Post by **nz4x4** » Tue Sep 05, 2006 7:55 pm

Yea an overkill is better but i dont think i can fit 60mm OD in....

Who is doing your bending Callum?

callum007 · Post by **callum007** » Tue Sep 05, 2006 8:36 pm

They are called "tube benders" (isnt it ironic) in east tamaki.. real helpful and CASH talks with him..

nz4x4 · Post by **nz4x4** » Tue Sep 05, 2006 8:41 pm

Will go and see him.. with CASH

How did you set out the shape you wanted? just a big pattern on paper?

callum007 · Post by **callum007** » Tue Sep 05, 2006 8:46 pm

no i scribbled some measurements on a pad in the van while outside his shop on sat morning. handed it to him. he said sweet as.. going to take a week or 2 as he will run it with another order.... CHEAPER if someone else pays the set up..

nz4x4 · Post by **nz4x4** » Tue Sep 05, 2006 8:52 pm

Oh, something just came up when looking at the tensile strenths of ERW compared to DOM. ERW is has only half the tensile strength! (45000PSI compared to 80000PSI) What a bugger. this means that it would not comply with CCDA specs.

Anyone know where you can buy DOM tube in Auckland? and can you get it in the same/similar size? (will price it up and look at sizing)

callum007 · Post by **callum007** » Tue Sep 05, 2006 9:01 pm

call Steel south Auckland. 263-5806 very helpful.
or fletcher steel in penrose..

nz4x4 · Post by **nz4x4** » Tue Sep 05, 2006 9:05 pm

Steel South auckland is who i normall deal with so will give them a call tomorrow. Cheers for that Callum

nz4x4 · Post by **nz4x4** » Tue Sep 05, 2006 9:22 pm

OMG!!! You cant satisfy everyone!!! I have just been reading through NZFWDA specs and it states

"Twin lug connections as in fig 4 with axis working under double shearing conditions may be used, but not on main hoop."

Also after reading the ORANZ specs i couldnt find anything saying that a twin lug connection had to be used on the main hoop/b pillar. Only that that is an approved type of connection. Where did you find that information GQTROL? (will take your word for it though as im still a newbie)

So according to this and GQTROL you cannot satisfy NZFWDA and ORANZ.

Post by **mike** » Tue Sep 05, 2006 9:23 pm

can you post your findings back here please. I would be interested in what steel to use as I will be going down this path for my project.

Cheers

Mike

nz4x4 · Post by **nz4x4** » Tue Sep 05, 2006 9:26 pm

Will do. After i get a definitive answer i will post the design and materials used. I will also get the built cage checked by ORANZ, MANZ, and winch comp scruitneers to verify that it is to standard. then people will have a definitive design to work off.

Post by **mike** » Tue Sep 05, 2006 11:02 pm

Sounds like a very good plan and will be a valuable piece of information for anyone wanting to build one at a later stage.

Mike

gomulletgo · Post by **gomulletgo** » Wed Sep 06, 2006 12:21 am

Hi, I know this is a little off-topic, but.....

nz4x4 could you please tell me the CAD program that you are using, and if it is easy to learn or not?

I don't want to design the next space shuttle so if anyone could put me onto a simple easy to use CAD program I would really appreciate it.

MULLET

GQTROL · Post by **GQTROL** » Wed Sep 06, 2006 7:26 am

Sam,
We were told at Scrutineering for Kiwi by Howard that we needed the twin lug connection if we wanted to race ORANZ events. Sam Baddeley also had to do that before Taupo 1000 last year. But now just re-reading the ORANZ rules, the twin lug connection is just one way of connecting the cage to body / chassis. Since welding the foot plate to the body isn't one of the recommended methods, I wonder if that is why Howard told us to twin lug it.....cos our foot plates are welded as per MANZ, but I guess is a no no for ORANZ.

nz4x4 · Post by **nz4x4** » Wed Sep 06, 2006 8:20 am

Oh OK, sweet as, was just trying to figure it out.

So looking at the rules, my first idea of how to mount the cage to the chassis should be fine, and according to the NZFWDA rules would still aloow me to compete in winch comp's.

I have sent Howard an email and have also posted on Sootys forum to try and get the definitive answer. As usual, it all goes back to Howard.

nz4x4 · Post by **nz4x4** » Wed Sep 06, 2006 8:21 am

gomulletgo wrote:Hi, I know this is a little off-topic, but.....

nz4x4 could you please tell me the CAD program that you are using, and if it is easy to learn or not?

I don't want to design the next space shuttle so if anyone could put me onto a simple easy to use CAD program I would really appreciate it.

MULLET

I didnt even uase a CAD program for that, that was jsut illustrator. But normall i use Vector Works or pro-desktop

doddzee · Post by **doddzee** » Wed Sep 06, 2006 8:24 am

If you mount it in the way of your first picture you are going to get vibrations through the body as your body is rubber mounted. You are going to need some sort of flexible joint inbetween the chassis and body.

nz4x4 · Post by **nz4x4** » Wed Sep 06, 2006 8:30 am

What about putting rubber inbetween the body and the plates where the plates sandwich the body?

doddzee · Post by **doddzee** » Wed Sep 06, 2006 8:35 am

Im not sure but if you were going to you would probly have to make the rubber fairly thick. Not sure if the NZFWDA would allow that either

GQTROL · Post by **GQTROL** » Wed Sep 06, 2006 8:37 am

Agree with Doddzee,
We've used Nissan rubber body mounts where the two rear stays attach to the chassis. This way the entire cage is effectively flexible mounted.