Roll bar spec

[Deanno]

Does the roll bar have to be bent?
I have made one in work 50mm OD and 5mm thick, as I was unable to bend it so I did 2 straight uprights, then in at 22.5 deg and the same for the top would this be ok?

I put a bevel on all the joints to enable me to get full penetration.




Regards
Dean

[davidimurray]

For IVA there is no actual requirement to have a rollbar. Although welding isn't obviously as good as a single piece of tube there shouldn't be any great issue with your hoop - I presume it is CDS and not welded or even worse scaffold pole?

It is worth noting that if you mount yout seatbelts to the hoop structure then it becomes part of the 'seatbelt' system and as such must be deemed suffciently strong by the IVA man to resist any impact. AshG had an issue on his test where the inspector deemed that the single bolt at the bottom of the diagonals would not be strong enough and had to fit 2 bolts. I've done the same on mine to avoid any potential problems - have a look at photo 170 in my gallery here http://www.facebook.com/media/set/?set=a.245243755324.181913.601005324&l=a9831a9319& type=1

Out of interest what are the chnages you have made to the rear structure for ?

[eSteve]

Deanno,

my understanding (from a previous post) is that the roll bar per say is not an IVA requirement. Search the IVA manual for roll bar or an equivalent and there is nothing about it. So fabricated (i.e. not bent) roll bars maybe OK.

The aspect of the roll bar that will be inspected is the use of it to secure the seatbelts/harnesses. For this purpose the IVA inspector will need to deem it suitable, but this might only concern the fixing of the roll bar to the chassis (see below) and the suitablitiy of the cross bar to which the harnesses are secured. I see you don't have a cross bar at the moment but presume you will fit one. Puting all this to gether my interreptation would be that: if the roll bar is adequately fixed to the chassis and the cross bar mounting the harnesses is suitalbe then the top of the roll bar shouldn't matter to much, assuming no sharpe corners blah, blah...

One thing to note, and a little mod. I have to do to my fabricated parts for the back stay lower mounts, is that AshG failed when having only a single bolt, it looks like you have too (correct me if I'm wrong). So I am planning on having two fasteners per roll bar backstay.

See Ash's note on his IVA fail here:

http://www.haynes.co.uk/forums/showthread.php?t=3700

This maybe a bit discretionary on ther part of the examiner, but my take is it's best to err on the safe side rather than have to re-work it latter.

Hope that helps,


PS: Looks like davidimurry and I were replying at the same time, sorry to covers some of the same ground!

[Deanno]

it is welded tube but this is only a mock up, i do intend to get CDS tube, now that you mention Ash G's issue with the stays i do recall reading that in the "Guide to building the Haynes Roadster" i will address this thank you for bringing that up.

as for the changes here, i have put these vertical ones here and i'm puting them also on the corners for extra strength.


here i have put an extra peice of 20mm box from the tube to the top of the rear suspension plate with a corner piece of 3mm plate this will be for my full roll cage / rear support stays. and will also act as a support for when i but my "boot" in made from aluminium (after IVA)

[Deanno]

yes i intend to put 2 bolts through the rear stays and i have also used M10 bolts for securing the roll bar itself.

Davidmurray: that is a good idea for the 2 bolts thank you.

[davidimurray]

Dean I would be tempted to move the two verticals at the back closer to their original position under the roll hoop diagonals as this provides a nice load path for the hoop that runs almost straight down and then ties the back of the car up to the bottom of the hoop. It's good to see that you have included gussets to help the load path but I would have thought if you moved them outwards you could get rid of them and also the centre bar betweern the two and save a bit of weight.

[Deanno]

good point i will do that but probably keep the gussets in, and "copy" your idea with the 2 bolts for the rear stays if that is ok.

may i ask roughly how much did it cost to do your roll bar inc materials?

[davidimurray]

I bought my roll hoop ready bent as part of AshG first group buy, from memory it was about £40 for the bent tube and then I bought a length of CDS for the cross bar and another length for the diagonals.

One other little thougt, if you mount the plates at the bottom of the tube, you can make the bolts hidden but still get a spanner on the bolt from underneath. See photo 1 and 2 in this gallery http://www.facebook.com/media/set/?set=a.10150244028550325.366987.601005324&l=583fd5 cd3a&type=1

[Deanno]

cheers for that david

[eSteve]

Deanno,

I like your idea of having the strut from the rear suspension mount box to the top of the rear tub bar thing. I've just stuck a bit of tape on my chassis to remind be to put two in.

David,

agree with moving the two verticals out so they are then under the roll bar rear struts, I will be doing this too.

Thanks for the tips and nice photo galleries, both of you. I will be having a good look at them.