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Rollcage/spaceframe design and ULTRA 4/MSA regulations


Lewis

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Interesting.

I've seen 2 minimum spec CDS rear hoops deform and bend rearward whilst going around a tight corner around a tree.The tree caught all of the competitors rear hoops and 2 were deformed. The two that were deforemed were CDS cages the competitors were told they cannot compete any more they must redo the cage. One guy left the sport one guy went to whitbread and ordered new rear hoop.

As I understand it the main problem with seamed (blue band) is not just about the method used to create the pipe but more to do with it's consistency and the material/carbon content. I've seen the issue myself with blue band both when bending it and in use. The material specification for Blue Band means it has to have a specified average carbon content along a length of 100 metres. The problem with that from a roll cage POV is that it's not consistent along it's length so some parts can be too brittle and some parts too soft.

I've seen a blue band cage bend when the vehicle was literally just rested against a tree because it just so happened that the piece they'd used for the front hoop had a very low tensile strength at that point, the right hand side of the front hoop was MUCH softer than the left hand side (as proved via some very basic tests with a hammer after the hoop was removed).

CDS isn't any more difficult to bend than blue band, the bender needed is a bit more expensive but not THAT much and if CDS was made mandatory I'm sure most clubs would end up with a bender or two available for people to use.

It's a similar reason for the change to AF/R helmets, it wasn't due to the fire resistance part but was due to a change that meant those without FR had the test sample rate reduced dramatically so AF/R helmet shells were far more consistent as a safety specification.

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I feel that the qualities of metals have fallen over the years. As an engineer the reason I back seemed tube with thicker wall, is that the lower carbon steel is better able to take a home weld. I've seen a CDS tube torn around the weld on a rear hoop. If a stronger tube is used with higher carbon content, the fabricator needs to be aware the risks of making it brittle.

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I have a few thoughts have been involved in various events and Motorsport types over the years;

The MSA cage types are really only intended as a ROPS on a chassis and body, or monocoque vehicle. Start trying to combine MSA type ROPS and external protection from rocks and trees doesn't work without loads of complications and extra weight. Take Paul's (Moose) little tractor for example, the cage is based on a pretty typical external MSA cage. Start adding tube wings, tray back, door bars etc and it gets very complicated with loads of discontinuities in the structure.

True US spec Ultra4 cars using the cage above the belt line principle are all a complete tube frame system (i.e NO original chassis or body) and are probably safer and stronger, while lighter than a truck like Paul's that complies to MSA. This is because the rules allow them to use continuous tubes around the belt line and roof sides that work better for external protection, while the over all cross bracing and diagonals in the structure build the strength.

My vote would be allow the US type cages in Ultra4, there's great proof that they're safe and strong in this type of competition and plenty of European events will permit them. Sod the out of date MSA events.

Regarding seamed tube, I completely agree with banning it. It's fine for a low speed flop during a trial, but I wouldn't want to see the effects of a 60mph+ roll or a multiple roll down a rock section on a home made push bender bent seamed tube cage. Throw it in the scrap bin and pay someone to build you a cage that will actually save your life one day!

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The problem is there has been plenty of 60 mph Plus accidents with seemed its how they used to make comp safari cars way back when dont you know and believe me they were going faster then 60 mph even in the 70's! Hell a few cars still competed after there accidental excusrions into trees at speed. There are several accidents on you tube and many will remember some of the bigger accidents of the 80's and early 90's where seemed did just fine thankyou!

As for falling down a rock face or prolonged over and over. I'd prefer something to not crush or deform! Minimum spec cds does and its quite well documented. Add to that the welding high carbon content is more involved. There is a few pics of the weld making its node brittle and after a roll rips the ajoining tube away from the welded node where its become brittle. I believe this was a brought cage not built at home (I could be wrong but if memory serves me right) Alot of people up spec the wall thickness of CDS but then lose the weight advantage.

The one thing that will always steer me away from buying ANY Cage from anyone else. Did you see the spec of the material? Do you know EVERY weld is good under the neat bead? Do you know that they bothered to clean the chassis before welding or maybe they hired a new guy and he is welding your motor up.

Would you bet your life on it?? Just because you paid someone doesn't mean they bothered to care, Your just another punter. With the way things are these days with the carp being sold I wouldn't bet my pet gold fish's life on someonelses weld or prep. If I make it to spec, order material and double check its actually to spec before I build it, I know it will be upto the job. That, I'd bet my life on!


I don't understand the seemed haters, and I probably never will.

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If you're really concerned about buying a professionally built cage then ask to see the certificate of conformity for the material and the welder's coding certification. Beyond that there's not much anyone can do besides 3d modelling analysis and/or destructive sample testing

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The cage on my landy is blue band, it's been rolled and abused by me fairly well, there are no deformities and I trust it- it was built in the workshop by us, and welded by my dad (a coded welder) and there has never been an issue, or with any of the other blue band cages we have built.

Dad's buggy uses a cds hoop, likewise, this has been abused and is still fine- although it is a much lighter truck, however this will be changed to a blue band cage in the next year or so, as it is a trialer not a racer, therefore it does not warrant the extra cost of the cds, the only reason for new cage design is that it is being changed to single seat.

My next car however, which is being designed for the u4e style events, will use a cds cage to suit regs, however as it is not to save weight, I will likely use thicker walled cds and it will be built closer to a u4 style chassis and cage anyway, so as mentioned, will be much stronger than a twin hoop alrc esque cage.

The comments about expense; well I plan on entering KoV this year, and hopefully following years, although probably not in my land rover for much longer, so far I have bought coil overs and tyres, along with obviously the other bits that people tend not to think about, to name it in one, beefing the old girl up, and I could buy a very high quality cage for less- let alone what I could build one for; I'm not as the cage that's there is suitable and meets regs, but if it didn't it wouldn't cost the earth to change it- and i for one, would not resent spending the same on a cage as I have on shocks.

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my buggys safety cell/main cage was £450 made out of CDS, all notched and bent. That ISNT a lot of money for a cage thats well over spec'ed and that i trust to keep me and my best mate alive.

All the addiction tube work will be made out of blueband and similar to Barry Gee's tomcat, with be made sacrificial.

Your an idiot if you expect to take part in a extreme sport without spending the money to keep your co-driver and yourself safe.

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No issue spending money. I have never said I begrudge spending money on a roll cage in fact quite the opposite. My own time is worth more to me than most peoples Hourly rate as I believe most people have the same beliefs. Paying someone else to do the job would work out cheaper by far I would expect. My issue is trusting somone else!! Have you seen some of the welding passed off on some challenge vehicles more to do with critical suspension mods than cage in this instance built by supposidly "pro workshops".

Not knocking anyone or anything on here don'r get me wrong. Its interesting how this has gone.

The soloution is above by another poster who has the best compromise. That builder/Forum guy sounds a very sensible chap! Buy the material and take it to be bent to own specs.

The point I was making was the extreme effort put into outing of everyman who used to be able to build to a high spec in his own workshop. own bender to get things Right. This hate of Blueband has come from car builders in the last few years I'm sure. This somehow got lost into a my truck is better because xxx CDS is better because xxx. seemed is better because xxx The actual Point it seems people think unless you own a fab shop, use the latest CDS, get "pro workshop" builder to build it, your uncapable of building a vehicle to compete with. Or am i Missing something? I guess now its set in most peoples minds and beyond sense to me anyway. With the recent welding poor fab work poor engineered design seen on more then a few instances. I wouldn't trust anyone "supposidly coded or not" to weld a wing mirror on, let alone touch my chassis or any critical part. The reg change is very interesting and the way its been defended is again is very interesting. I wonder how far it will go will the MSA/FIA try the same thing??

Good Mudding!

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I have a few thoughts have been involved in various events and Motorsport types over the years;

Regarding seamed tube, I completely agree with banning it. It's fine for a low speed flop during a trial, but I wouldn't want to see the effects of a 60mph+ roll or a multiple roll down a rock section on a home made push bender bent seamed tube cage. Throw it in the scrap bin and pay someone to build you a cage that will actually save your life one day!

I almost completely disagree...

Material selection (cds v sch40) is almost irrelavent if a cage is built to a poor desgn and prepared and welded poorly.

I have built close to 100 sch40 cages with a center push (and 8 cds cages to date on my draw type) i always built to the msa's blue book, i consider it to be an essential blueprint for keeping myself and others alive and well.

i have beaten all of my cages badly without any failures, and dispite a few mulitiple endo's and complex hard rolls on rock sections the red band cage on my Gwagon is still sound.

I do wonder whether part of the motivation behind legislation toward cds is the perception that the costs associated with cds would push cage building into the hands of "professionals" away from us amateurs.

I also really cannot understand why some home builders and (supposed) professionals choose to ignore the msa specs and drawings, there are plenty of cage designs that can be adapted for virtually any use. and allow you easy log booking and scruteneering and peace of mind that you are using a proven design that will work.

Unless your spectaculaly talented (Daan!) or building something extremely odd shaped why risk you own design?

I personally really don't like most of the american cages with their random sleived joints where the cage builders aren't skilled enough or cannot be bothered to make all tubes continuous where possible.

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I have no problems with the tube specs all the tube on my truck is cds any way.

I also don't have a problem with making it as safe as possible, On both years that KOV has been running that has been some big roll overs not just flops.

I was surprised at the new side bar rule and I wrongly assumed that having a car that met all the (MSA) cage regs last year would mean I would be fine for this year.

Its easy enough for guys with space frames like Mike to adapted but not quite as easy when you have an exo cage, but i will ask some questions and see what I can do to meet this rule.

I did really want to do the EMC "every man challenge" as I might have had a small chance at being competitive in this class but really don't know why they put in the rule about the radiator being in the front....

Not sure if this rule came from the states where they have no mud?

Its mega frustrating I have always had the radiator in the front but last year was my breaking point, as there was a pool of bonnet depth mud on the lap and after each dip we have to pull over and empty litres of water over the rad to try and clear it enough to get some cooling. So i have spent some money got a new radiator which I am about to install in the back...

I also think its a little short sighted as I reckon there would have been quite a few uk challenge spec trucks that might have entered.

Under the EMC rules I can have coil overs and and triple bypass shocks per corner (as long as attached to the axle) but i can't have a radiator in the back.....

So is the EMC class really there to open up the event to a wider audience less pro more budget....

Not trying to have a go I understand that there will always be some thing in rules that competitors don't like and it is impossible for an organizer to please every one.

Paul

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I almost completely disagree...

Material selection (cds v sch40) is almost irrelavent if a cage is built to a poor desgn and prepared and welded poorly.

I have built close to 100 sch40 cages with a center push (and 8 cds cages to date on my draw type) i always built to the msa's blue book, i consider it to be an essential blueprint for keeping myself and others alive and well.

Fair enough and I certainly agree with your comments regarding design and construction.

My first home made cage was exactly built to MSA layout from CDS, driven by some of the horrors id seen with off the shelf bolt together internal cages (it was for a mk1 escort).

I do feel that banning blue band MIGHT help to deter people who don't know what they're doing 'having a go' and I'm sure your cages are properly built and designed and therefore do the right job!

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  • 3 weeks later...

Thought i would update this thread for any one following...

The rules have been tweaked slightly...

19.5 All vehicles, including those with doors, must have at least one side bar on each side of vehicle that will protect occupants from side impact. The sidebars must be of the same tubing material and dimensions as the main frame of the roll cage. The sidebars must be located to provide maximum protection to the occupants, and must be securely attached to the front and rear hoops of the roll cage. The location of the sidebars must not cause difficulty in entering or exiting the vehicle.

So I will be able to use bolt in side/door bars in the cab...

also for people interested in the EMC (every man challenge) this might help too....

27.5 The engine must be mounted at the front of the vehicle along with a cooling radiator.

might get another season out of the old tractor yet before work starts on an IFS unobtainium tubed buggy :unsure:

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also for people interested in the EMC (every man challenge) this might help too....

might get another season out of the old tractor yet before work starts on an IFS unobtainium tubed buggy :unsure:

The wording of 27.5 has now been changed to...

"27.5 The engine must be mounted at the front of the vehicle"

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