I understand (but correct me if I am wrong) that there is a regulation governing the diameter and the material to be used in Roll over bars. Could anyone let me know what this is or point me in the direction for obtaining the information. My needs are a single loop bar for a Dellow.
Thank you
John Mac.
John, The best place to go for a definitive answer is the RAC blue book. I can photocopy the relevent section for you if you haven't got a copy. cheers Simon
ReplyDeleteSimon, My Blue book is way out of date in fact its probably a collectors item by now!! If you could copy the relevant page for me this would be very much appreciated. Thanking you Regards John Mac
ReplyDeleteJohn The Blue book contains some vital gen. But please forget any idea of a single un-braced roll over bar. Lethal. It is vital to have properly designed stays/supports running either fore or aft (to use the nautical terms). I had the very sad experience of seeing someone killed at a speed hill-climb when his un-braced "roll over bar" simply folded over in a relatively low speed accident. Such a bar may look the business, but is a sure sign of an amateur engineer at work. Maybe John Aley of the MCC would give you further advice. He set up and ran Aley Bars (Aleybars?) for many years and did more than most to promote the safe design and construction of roll over bars.
ReplyDeleteNigel, Thanks for your comments I will take heed of your advice. John
ReplyDeletePosted on behalf of John Aley (who knows about these things!) Hello Mike I`ve been reading the rollover bar correspondence with some interest but had purposely not added my twopennoth as it`s 12 years since I sold Aleybars and I suppose, if I`m honest it still hurts a bit. We started making and selling the things in 1964 when outside of the US they had not been heard of and by `71 had made such an impact in the competition world that the FIA made them compulsory. Although things have changed a bit since those early days the sort of bars we were making then would be ideal for something like a Dellow in trials or even in sprints or some other club competitions. The recommendations in the Blue Book are based on the FIA approved designs which although effective are heavy and expensive to produce. I suggest that for the Dellow something from 38mm or 50mm OD tube, good quality ERW is quite sufficient and about 16gauge would be quite adequate. What is vital though is that the main hoop has backstays and the whole thing is strongly mounted on to some part of the frame that is STRONG. It may be sensible to weld some strong mounting points into the car and the bar can then be bolted into place. The secret of a rollbar`s strength lies in TRIANGULATION. Like Mr Bugatti I trained as an artist rather than an engineer and am a strong believer in the old theory of what looks right probably is. A single hoop by itself is lethal and the heavier it is the more likely it is to crumple, perhaps on to the driver, in an accident whereas a lightweight structure with lots of tubes in all directions will cope with anything - remember the old Maserati Birdcage chassis? In our heyday we built a full cage in light alloy for a GTM Alfa that had struts in all directions but which I could still lift with one hand. It increased the rigidity of the car to such an extent that its lap times improved by 2 seconds - and when the car was subsequently written off the cage saved the driver. Sorry Mike, I`m beginning to ramble but it`s late and my glass is empty - see you on the Lands End I hope. John
ReplyDeleteJohn Aley, Thank you for your clear comments on roll over bars - were I nearer I would refill your glass for you. Presumably scrutineering of roll bars is not part of the trialling scene, in making this comment I have not yet had the opportunity of looking in the Blue book under I'm told "safety regulations". The Dellow has inner steel wheel arches that are fore and aft of the seat back, I'm quite sure that many Dellows have only a single loop bolted onto the steel which as was suggested by another correspondent is more of a cosmetic/pretty item than a safety feature. The other point especially for the Dellow is the difficulty of triangulating steel behind the bar as this would interfere with the frame for fitting the hood (albeit many Dellows including mine have never had the luxury of weather protection) Anyway, thanks again for your comment, after I get my Dellow back from an expensive engine rebuild, which could be the subject of further correspondence!! I will review whats needed. Regards John Mac
ReplyDelete