greenstream Posted July 11, 2015 Share Posted July 11, 2015 Hi alm. I am in The process of designing an external rollcage for a Defender. When looking at the main hoop, you often see them more narrow than then truck cap.I would have thougt that the same width or a bit wider than the truck cap would be the choise ? Whats your choise or experince with this. How about the hight of the main hoop ? Thoughts and experince ? Thanks Morten Quote Link to comment Share on other sites More sharing options...
simonr Posted July 11, 2015 Share Posted July 11, 2015 By 'external' do you mean behind the truck cab in the pickup / load area rather than external to the bodywork? A narrower cage is likely to be stronger as width at the top is closer to the width of the chassis rails - the overhang on either side is less reducing the leverage trying to bend the tube. On the other hand, something wider than the cab protects the bodywork better. The height is the same - shorter = stronger. If the purpose is to save the bodywork - make it external. If it's to save you - make it internal. The MSA Blue Book is worth a look for tried & tested cage designs. It gives guidance on jointing and material type. If you follow their guidance, it will most probably save you when you really need it! Si Quote Link to comment Share on other sites More sharing options...
De Ranged Posted July 12, 2015 Share Posted July 12, 2015 Just to add to the above, sticking the cage out past the body to protect it can backfire when you drive through scrub and bush.... sticks get down between the body and the cab and as you go forward pivot around the cage damaging the body Also if you exo you need to consider body movement and space away for this, the landy is good for this as the body is bolted to the chassis not on mounts Personally if its a road going truck a simple A, B 6 point cage internally to me in this case its all about weight and running costs and is only there for the one time use.... you don't drive your daily driver into situations where its 50/50 lol so the internal is lighter and doesn't cause air drag upping your fuel usage If its a trailer queen or a weekend hero where your going to "try that line" then an exo and I build them out past the body (its not nice driving home without a windscreen or windows lol) if I'm going to run 50/50 lines and regularly roll it then I'm building the body into the cage Here in NZ one of the rule sets for cage building NZ4WDA has span distances and vehicle weight versus the dia of the material so cages are built to the weight and clear unsupported span length... now notice how I said one of the rule sets, we have 4 different sets that apply to 4wd competition best you talk to the local club (or event organizers) before you start this so what you build can compete (and be safe) Quote Link to comment Share on other sites More sharing options...
greenstream Posted July 12, 2015 Author Share Posted July 12, 2015 Thanks for your reply. The cage is for a pick up and is to be covering the truck cap both at the front and behind the cap. How wide the front hoop will be gives it self as its passing between the footwell and outer front wing. This makes the hoop slightly wider than the truck cap. This width I would like to copy to the rearhoop for a clean design. But when I have been studying photos of other cars the rear hoop seems more narrow and raised the question. Its not for my own car. Its for at challenge truck. We have some rules for building cages here in Denmark, but they are not adapted to 4x4's very well so we tend to uprade to some of thd British rules when in doubt. Quote Link to comment Share on other sites More sharing options...
Jon White Posted July 13, 2015 Share Posted July 13, 2015 I suspect its a matter of commercials - the hoops are bent up to fit inside a hard top, and they simply use the same hoop for an external cage - saves people having to stock two different sizes of hoop. There is no reason if you are bending your own why you cant bend it to be whatever shape/size you want. The bull bar on mine is a good example of this - mine actually goes slightly outboard of the front wings, and has save my wings many times. The commercially available ones don't, and so you end up doing the wings in all the time (plus mines made out of the same tube as my roll cage). Jon Quote Link to comment Share on other sites More sharing options...
simonr Posted July 13, 2015 Share Posted July 13, 2015 The bull bar on mine is a good example of this - mine actually goes slightly outboard of the front wings, and has save my wings many times. Sorry, my mistake, this is Hybrid from Hell's Si Quote Link to comment Share on other sites More sharing options...
Jon White Posted July 13, 2015 Share Posted July 13, 2015 PMSL Quote Link to comment Share on other sites More sharing options...
simonr Posted July 13, 2015 Share Posted July 13, 2015 Sorry Jon - I couldn't help myself! Si Quote Link to comment Share on other sites More sharing options...
greenstream Posted July 13, 2015 Author Share Posted July 13, 2015 Guess its to light weight for Dirty Diesel to be involved in ? Quote Link to comment Share on other sites More sharing options...
western Posted July 13, 2015 Share Posted July 13, 2015 cripes, that's some bullbar Quote Link to comment Share on other sites More sharing options...
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