13 replies to this topic

[Sawyer]

Hi all.

 

I have searched high and low and just want a definitive answer, hopefully by someone who has experience in this subject and using this size tube . I am planning on using 1 5/8" (41.28) cold drawn seamless tube to build a cage for my mini. I plan of using this mini for track days and would one day like to compete in events such as hill climbs and sprints. I don't want to use the wrong tube now and potentially restrict my possibilities in the future.

 

I have downloaded a copy of the MSA Blue Book 2016 and from what I can gather I am okay to use this size tube for a roll cage. 

 

'Material Specifications 

1.4.1. Specifications of the tubes used: 

Minimum Material 

Cold Drawn Seamless Unalloyed Carbon Steel, containing a maximum of 0.3% of carbon. 

Note: For an unalloyed carbon steel the maximum content of additives is 1.7% for manganese and 0.6% for other elements. 

Minimum Yield Strength 

350 N/mm2 

Minimum Dimensions (Ø in mm) 

a) Mandatory tubular members
45 x 2.5 (1.75” x 0.095”) or 50 x 2.0 (2.0” x 0.083”). 

38 x 2.5 (1.5” x 0.095”) or 40 x 2.0 (1.6” x 0.083”). (For roll cages/bars approved prior to 1.1.95). 

b)Optional tubular members
38 x 2.5 (1.5” x 0.095”) or 40 x 2.0 (1.6” x 0.083”). 

1.4.2. In selecting the steel, attention must be paid to obtaining good elongation properties and adequate weldability. 

1.4.3. The tubing must be bent by a cold working process and the centreline bend radius must be at least three times the tube diameter. If the tubing is ovalised during bending, the ratio of minor to major diameter must be 0.9 or greater.'

 

Link - http://www.safetydev...e Book 2016.pdf

 

To some this might seem obvious but I don't want to get caught out, am I right in saying 1 5/8" would be fine to use for the entire cage?

 

Thanks for any input!

 

Ben

Edited by Sawyer, 08 March 2016 - 10:43 PM.

[keefr22]

I'm no expert, but the way I read the blue book, cages using mandatory members made using the tube size you mention must have been approved by the msa before 1995, and therefore new cages would need those members in the larger diameter tube. However, for certain classes in hillclimbs and sprints you don't need to use an msa approved cage. The rule of thumb is to read the section relating to the discipline you want to compete in first (section s for hillclimbs/sprints) as the regulations in that section take precedence over the general regs if they are different.

It may also be a good idea to e- mail the msa technical department and ask their advice, as they're usually pretty helpful.

Our Mini is logbooked for modified production class and we have a Safety Devices cage that uses the smaller diameter tube all round - but the SD approval was obtained prior to 1995. However, the scrutineer who did the logbook didn't actually check that......

Keith

[Sawyer]

Thanks Keith that is sound advice, trouble is at present I don't have a particular route in motorsport I want to explore. I was hoping I could fit a cage that covers a spectrum of events which also makes the car easier to sell down the line if needed. An e-mail is in order.

[keefr22]

 I was hoping I could fit a cage that covers a spectrum of events which also makes the car easier to sell down the line if needed.

That's a good plan, it's what we did with ours - logbooked  as a modprod car so it can be run when sorned without tax or MOT, but built to stage rally car specs & it would take little work to get to class 3 Historic spec.. Trouble is, I think some disciplines require MSA (or FIA if you want to do international events) approved cages which is why it's often easier to just buy such a cage. I have no idea how you (or even if you can) get approval for a self built cage - be worth asking the MSA that too!

 

Good luck

 

Keith

[nicklouse]

You will not be able to compete with a roll cage using that tube,

It is not big enough. You also do not state thickness.

[Sawyer]

You will not be able to compete with a roll cage using that tube,
It is not big enough. You also do not state thickness.

Originally I had planned to use 44mm x 2.6mm CDS for my main hoop and 38mm x 2.6mm CDS for everything else but no one local to me as dies capable of bending these tubes. I did however find someone who can bend 1 5/8" (41 x 2.6mm)

What cage can you recommend is suitable for my needs?

Thanks

[nicklouse]

Your mandatory tubes have to be the 45 or the 50mm with appropriate (as listed) thicknesses.

to be honest give Roll centres a call for one of their flat pack weld in cages. You get all the tubes of the correct dimensions bent in the right places and just a bit over length to allow for notching.

But back to the rules. Read the blue book downloadable from the MSA site.

It states what are the mandatory tubes and those have to comply. It also states what size othe others can be.

What is what depends on what cage you are doing.

When mine arrived 20 years ago.

[keefr22]

You will not be able to compete with a roll cage using that tube,

It is not big enough. You also do not state thickness.

You could compete using a cage made from that tube in road production classes in sprints & hillclimbs, as rollcages are not mandatory in those classes, so they don't need to meet the specs for classes where they are. I admit though it would probably be a bit shortsighted not to use the specified materials.

Keith

[nicklouse]

You will not be able to compete with a roll cage using that tube,It is not big enough. You also do not state thickness.

You could compete using a cage made from that tube in road production classes in sprints & hillclimbs, as rollcages are not mandatory in those classes, so they don't need to meet the specs for classes where they are. I admit though it would probably be a bit shortsighted not to use the specified materials.Keith

Sorry but no. If you have a cage it should comply. Having a cage that does not comply in a class that does not need one is not permitted.

You are basically implying you could compete with an Alloy roll cage in a class that does not require a cage even though they are banned from all Motorsport.

[keefr22]

There was a long running thread about home made cages on another forum, and one conclusion I remember was that it was stated that you could still use an Alleybars alloy cage in road production classes because there are no regulations covering the use of cages in those classes. Whether that would be the case if you actually turned up to an event with one fitted, I dont know, and wouldn't be interested in trying to find out! I do know that the one time we ran in road production in my sons Ibiza Cupra fitted with full FIA cage, harnesses and Cobra seats, the only thing the scrutineer was interested in was did we still have the inertia reel belts fitted (even though we weren't using them), were the back seat and door cards still there and was the live battery terminal marked in yellow and the ignition switch with on/off. He didn't even look at the cage, it could have been made from plastic plumbing pipe - he just wasn't interested as it wasn't needed to compete in the class.

[luigi86]

Whilst I admire the idea of making your own cage from scratch, you might be better off buying a kit and fitting it yourself, then you can add extra tubes etc if you feel the need to.

[Sawyer]

Whilst I admire the idea of making your own cage from scratch, you might be better off buying a kit and fitting it yourself, then you can add extra tubes etc if you feel the need to.

 

Im starting to think that might be the way forward, I'm a fabrication and welding engineer by trade and we have just about every machine you could think off but no tube bender as we always buy in pre bent stainless fittings like most do. Im personally looking into buying a tube bender as it would appear no one in my area has one! but the costs involved would certainly require I would need to be able to make money back from it. My boss is after a tube bender but its not a priority of his unfortunately.....and new twin spindle all shiny milling/turning DMG lori singing and dancing machines keep getting in my way!

 

I have emailed that roll centres the other day who Nicklouse recommended so will wait and see if they reply and what sort of price they are asking for.

Roll cages are a minefield and not something you want to get wrong, especially when my loved ones will be driving this car too!

[nicklouse]

Good move.

Mine when in over a weekend. I did buy a notcher but as you will know a couple of cuts with a grinder and you have as good a cut.

The oddest thing is thinking about the welds on top of the cage. Easy if no roof but if there is you just cut 4 holes in the floor and drop the main hoop and front legs through the floor. The spreader plates cover the holes up after.

Have fun.

[Sawyer]

Good move.

Mine when in over a weekend. I did buy a notcher but as you will know a couple of cuts with a grinder and you have as good a cut.

The oddest thing is thinking about the welds on top of the cage. Easy if no roof but if there is you just cut 4 holes in the floor and drop the main hoop and front legs through the floor. The spreader plates cover the holes up after.

Have fun.

 

 

I did wonder about welding the top once the cage was taking shape in the car, thats great advice drilling some holes in the floor! Im really looking forward to getting the cage started.

Edited by Sawyer, 11 March 2016 - 06:20 PM.