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CDS Vs BB


Warthog
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Been looking into cage's for awhile now. But the most common argument is between CDS or BB?

Correct me if im wrong....

- Blue Band is seam welded tubing, like scaffold tubing?

- Blue Band wall thickness can vary and cause weak spots?

- CDS Cold drawn steel, strong?

- CDS walll thickness constant?

- CDS expensive?

- CDS or BB has to be 3mm thick wall to meet ARC/MSA regs

The cage's i have been looking at are 3mm wall, Blue Band and comes pre bent ready to fab weld together and mount. Cost is good value, but safety is more important.......

Cheers

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BB is spec'd at 48.3 outside diameter x 3.2mm wall thickness, how much it varies i do not know

That's what I'm using for a full tube chassis. I can't see the point in CDS if its just a regular 'oh my landy might tip on it's side' type cage.

What are you building the cage to do - that's the real question. Though the answer would have to be pretty full-on to justify NEEDING CDS over BB.

Of course, if you can do it CDS and don't mind the cost, then why not?

Another point is that I know a lot of US offroad racers mix tube types or avoid CDS all together due to fears over it's brittle failure characteristics - they think it's more likely to fracture and stab you than something more ductile which will just bend. Personally, I don't subscribe to this viewpoint and my next cage will be CDS, but it's not for a 'landy-that-might-tip-on-its-side'...

Either will be fine if the welding is ok.

Al.

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Blue band is more than strong enough. It may be a little heavier, but it is easier to fabicate with. It does not deform so easily in the cheaper benders, and it welds strongly and easily. It takes hard knocks without damage.

If you are building a lightweight racer using a big budget, then CDS would be a good choice. But it is a bit more difficult to work with. For most things offroad that you will do with a Land rover, including racing, Blueband is more than up to the job, represents good value for money and is approved by the AWDC/MSA.

Never heard of tubing inconsistences being of consequence. It is manufactured to a specific standard and is used for high pressure steam etc. It is VERY different from scaffold tube which may look similar, but should NOT be used.

If you are concerned about safety, then the cage design, mounting points and quality of welding are more important factors than any percieved safety differences between the two materials.

Regards,

Diff

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My cage is front hoop cds rear hoop cds, as this is the material that can be mandrel bent.

The rest of the cage was fabricated by myself using blue band, where having a slight kink in the radius of the bent tube would not adversley affect the overall strength.

Over the last 2 years I have given it some severe abuse and have yet to see any problems.

The front and rear hoop complete with kit form mounts came from Tomcat but fabricated to "Gwyn Lewis" spec.

I am not sure who tomcat use to mandrel bend tube for them.

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BB is strong but heavy; that's why my new cage will use Clubman 500 with some T45 for straight sections that won't see trees (internal cross braces, windscreen bar etc). I agree there's no point going silly as you won't get really high speed rollovers doing what we do.

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CDS is hugely expensive, and yes its stronger but most use this strength to go down in wall thickness to save weight on racers, as such for us BB is fine.

There are differeing qualities I have found the best I have ever seen is CORRUS BS1387 I think from memory, red paint coated, do NOT EVER use galv BB for bending !, and IMHO not even for straights as the metal qualiy and strength has been altered, plus not nice to weld...

Talking of welding in my mind is a memory that CDS should be annealled, and is better if TIG welded rather than MIG, which can be done but needs a better qaulity of welding and skill that you could get away with on BB

If you use CDS and have the same OD (48.3mm BB vs 50mm CDS) and have the same wall thickness then you will save nothing, use 50mm CDS and thinner wall and you are going to save weight for the same strength, but IMHO for what we do vs comp safari motors not worth it

More importnat are IMHO.....

The design and mounts of the cage,

spreader plates, and base plates

fishmouths and not huge welding to fill gaps,

cleaned metal quality welds and

decent HT bolts of the right spec and OD etc

Nige

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More importnat are IMHO.....

The design and mounts of the cage,

spreader plates, and base plates

fishmouths and not huge welding to fill gaps,

cleaned metal quality welds and

decent HT bolts of the right spec and OD etc

Nige

Quite right Nige. The cage geometry is by far the most inmportant factor. Add in some decent fabrication and your pretty much there.

Good point on the CDS heat treatment, and if your looking at Tigging it, I guess back-purging would be required inside the tubes :rolleyes: ... I'm not sure Northern chris is on here much any more, but I expect he'd have some good points too.

Does anyone know the actual steel that we call BB or CDS? I'm talking about the material code here. I've only used a small amount of CDS but it cuts & welds completely differently to BB. I wonder exactly what materials they are? :unsure:

Al.

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BB is BS1387 heavy

But isn't that the dimension/mass properties - standards for piping etc?

BS 1387:1985 "Specification for screwed and socketed steel tubes and tubulars and for plain end steel tubes suitable for welding or for screwing to BS 21 pipe threads"

What I mean is what steel is it actually made from?

Al.

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what do people use?

I use this.

http://www.tubela.com/h3pr.htm

Second hand. I have yet to ripple anything. I have managed to get the two outer pins to dent 3mm wall tube by using them on a narrow setting (meant for smaller tube). It was just an experiment to see how small a radius I could get (it still bent with no ripples, but as I say, there were a couple of small dents right at the pins).

Moglite used it for his cage and links which included some pretty heavy spec tube - I don't think he got any rippling on that either, maybe he will chime in.

There is little ovalation (is that a word?!?) - well within the usual 0.9 aspect ratio limit, which if memory serves is also good for FIA spec stuff.

Borrow a bender if you can - it's a bit of a use it once and then have it sit on your shelves forever getting in the way type deal if you are only doing one cage.

Al.

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Good point on the CDS heat treatment, and if your looking at Tigging it, I guess back-purging would be required inside the tubes :rolleyes: ... I'm not sure Northern chris is on here much any more, but I expect he'd have some good points too.

Yes, Chris is still looks in occasionally and has some good points.

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I'm a novice when it comes to steel types but I know we had our hot drawn seamless(?) tube for £25 a length 50mm by 3.2mm wall in stock 6 m lengths. Similar CDS would have been around £40 a length (but don't quote me). I can ask my mate for exact prices of all this if anyone is interested as he has a steel fabrication business and specialises in tube bending. He is also building his own space frame comp safari motor which is a work of art!!

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I personaly wouldn't allow BB tube anywere near my car: It potentially splits on the weld in a big impact. Forget that £15 pound saving per metre for a moment and picture yourself barrel rolling down a hill. In motorsport regs it is specifically forbidden to use this material.

The reason : BB = MM

Just to be sure that everyone understands, for people that need an explanation: Blueband (or ERW) is mickey mouse material.

Daan

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I went to Protection and Performance in Skipton to look at the tubeular chassis they are making and the guy there was telling me they sell pre bent hoops for around £100 these are 2" CDS made on a cnc machine. Why tiddle around with pre-historic carp tubing? Blue Band has been banned in every other MSA motorsport discpline for a reason!!!

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Why tiddle around with pre-historic carp tubing?

You're kidding, right? Any idea how many bends there are in a complete custom tube chassis?

100 quid a pop? :rolleyes: [sure, if it's just a roll hoop then the price thing isn't so much of an issue].

We're talking about landys leaning on trees, or flopping onto it's roof here, right? Not 120 mph multi-roll disasters.

Having said that - I may need a little more tube, anyone got a source in Hampshire for CDS? :ph34r::rolleyes:

Al.

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Disclaimer: I know nuffink!

But... as people have said, the design/mounting/welding is surely at least as important as the material.

Also, there is the question of what the vehicle is going to be used for - if you're likely to barrel roll at 100mph into a tree then you want a different beast of a cage than the average defender which may lean against a tree or fall on its side at <2mph. Worst case for most of us would be "doing a Jules" and even then, as long as the cage is reasonably well designed you will walk away (which is the important bit) whether it's made of pure Unobtainium or a bit of old scaffolding.

Personally I would be more than happy with a BB cage because my application would be to prevent too much tree damage and keep me & the vehicle reasonably intact if I did lay it on it's side. I'm not about to enter a comp safari so I don't care if landing on the roof at 50mph will maybe cause a tube to split because if that was going on I'd have bigger worries anyway, and would only have myself to blame for not fitting a cage designed for that job.

Now, before the wailing and gnashing of teeth commences, I would like to say there are some very knowledgable and experienced people here posting for BOTH SIDES of the argument, but this is because they come from different disciplines - some from racing, some from trialling, etc. - The same split argument would ocurr if you got into suspension design, engine tuning, etc. etc. some people come from a hi-tech / hi-spec racing angle, some come from a more agricultural one, both will work in the application they're intended for.

Really we need Jules as he's raced, winched, crashed and rolled in quite a few disciplines :lol: I'll bet now his Freelanders have slightly higher spec cages than his 90 did.

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I'd like to point out that Blue Band IS APPROVED for comp safari motors by the AWDC/msa and IS capaple of providing adequate protection in a high speed multiple roll over. Like any cage, whatever the material, it has to be designed, welded and fixed correctly.

More and more offroad racers are being built with CDS, because vehicles are getting lighter and faster. To go faster you need to lose weight, the easiest way to lose weight is to use CDS instead of blue band. Weight for weight CDS is stronger. If you can afford CDS, and feel you need it, then use it, if you can't, use blue band.

The original poster was asking for a simple rollcage for his landrover, lets not get carried away. :D

Regards,

Diff

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Well the same bloke who made/fitted Jules cage made/fitted mine

so the design has been tested at least.

I've seen CDS professionally built/fitted cages that are poxy to be crude!

not welded properly to the chassis/poor joint welding

and no screen bars.

x2 different companies too.

mine wasn't a cost issue rather a design prefrence I wanted after seeing Ali/Jules cages.

ps BB is in the Regs book still specifying material/mountings etc.

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Ive used allsorts, ERW, CDS, Scaffold, horses for courses IMO, you can make a cage from concentrated supertuffonium but if the design and/or execution is poor then its money wasted.

I need light, hence CDS, T45, C500, Im poor hence begging, borrowing, trading.

I use CDS for making our suspension components and wouldnt consider using any form of Electro resistive welded tube under ANY circumstances but then the stresses are different in that application. Having said that theres "expert" offroad fabricators selling mondo expensive CDS based suspension components with welds remanescent to a Crunchie bar - once again, nice material, carp manufacture = waste of money.

the is no right or wrong way - only the way more appropriate for your application and budget but fundemantally whatever you use get the design and build right.

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