Roadster roll bars

[Talonmotorsport]

I've been playing with some tube latly and I've asked every body who walks through the door what they think a rollbar should look like and what size tube it should be. Considering the rollbar is mounted to a 16 gauge chassis 3mm ERW seams to be over kill, 2mm CDS is ££££ so 2.5mm wall ERW in either 42mm or 48mm dia? Which of the three designs you would be interested in although I will be making all three in the next week or so and will be in my ebay shop soon.

[gingea1pom]

Personally I like the third one but I already have the second one thanks to AshG.

How much are we talking?

[Talonmotorsport]

Looking to be £80-120 ish but the lower bar would be fish mouthed on the lathe and fully welded with the base plates in place , 7/16 unf inserts fitted for either 4 point belts or inertia real belt top mounts. The rear support bars would be supplied over long with both ends fish mouthed one at 90' to join to the horizontal bar and the other at 40' (ish) to join the vertical.

[HandyAndy]

Originally Posted by Talonmotorsport

Considering the rollbar is mounted to a 16 gauge chassis 3mm ERW seams to be over kill, 2mm CDS is ££££ so 2.5mm wall ERW in either 42mm or 48mm dia?

i don,t wish to sound negative to your thoughts/idea of supplying a roll bar but,

i,m not sure i agree with the above, having been a semi pro bike racer (sorry i know i,m boring) i was always happy to spend extra on a helmet that i felt would offer me the best protection for my head in a crash, & yes i crashed a few times in my career but have never had a serious head injury, & i was always thankful that i didn,t buy the cheapest helmet on the market.

my point being....... i don,t think you can have "overkill" when the roll bar is the last safety device to protect your head in a roll over crash.

My own roll bar was supplied via one of Ash g,s group buy & my back stays are of the same material/thickness, & feel happy with the safety it offers.

said in a polite way i assure you.
cheers
andy

Full cage is the best option for paranoid folk and I fall into that bracket as up front the only thing hard enough to keep your head off the ground is the engine if you only have a rear roll bar.

[Talonmotorsport]

Fair comments Andy and yes you get what you pay for. I come from making NASA Autograss rollcages. Mid mounted engined full space frame saloons and theres no point in making a very strong rollbar if it connects to a tissue paper base. It'll just snap at the weakest part which will be the 16 gauge tubing. I can make FIA spec roll bars and even full rollcages in 38x2 CDS but it's £52 per 5mtr lengh and the idea of the Roadster is 'budget' is it not?

[HandyAndy]

i do understand your points tho i must say i,m in no way qualified in structural strength of chassis designs of any vehicle, as Fabby has suggested, a full roll cage is the "better/safer option" if the car builder wants total piece of mind etc, i was just using my own personal experience of "head safety" to be able to offer ( i hope ) a credible personal point of view.
As you say the Roadster is "to build a sports car on a budget" but doesn,t give a budget figure & so the safety aspect is one area i believe is worthy of spending more rather than less if the individual builder wishes/can afford to.

on a lighter note i prefer the middle diagram of roll bar design

again said in a polite & hopefully constructive discussion manner.

cheers
andy

[squbti]

i was thinking of the third option for my roadster & have cad drawings for 50mm pipe & was going to use stainless but but now also have the second one thanks to ashg
if onyone wants a copy of the cad drawings just let me know.
cheers
samy

[NEroadster]

I may be able to do some FEA Analysis for you if you want only quick and dirty but will give the general principles

[Alphax]

38x2 CDS but it's £52 per 5mtr lengh and the idea of the Roadster is 'budget' is it not?

There is a difference between safety and budget.

Safety is never expensive.