Manx Club

In the process of having a roll cage built for the Manx.It will be a 6 point affair anchored to the back of the rear seat area and along the sides on a '67 pan.Question is,I like the looks of either the 1 5/8" or 1 3/4" tubing and was wondering what has been used for wall thickness.The buggy will be strictly a streeter.Any ideas,tips etc. will be appreciated.

I would say if it is mild steel go with .090" minimum. You could probably go thinner with chrome molly if you gusset it well and tig weld. It is a light car without air bags, if you roll it your greatist chance of injury if flopping out or having an arm cruched or smushed between the cage and the pavement... Thicker wall tubing bends easier and most fab shops mig the gaps instead of doing a proper fit up. In that case thicker is better.

1 1/2" dia. .095 thick D.O.M. tubing would be more then enough to support the weight of a buggy. I built this cage from 1 1/2" dia. .095 thick D.O.M. tubing. Here are a few more pics. http://www.manxgallery.org/gallery/Berrien-Nostalgia

Here is what I did using 1 3/4 inch DOM. I also welded in 3/4 inch tubing into the cross bar and tapped them so that I could attach my shoulder straps. Carlton

[QUOTE="carltons"]Here is what I did using 1 3/4 inch DOM. I also welded in 3/4 inch tubing into the cross bar and tapped them so that I could attach my shoulder straps. Carlton[/QUOTE] You need to safety wire the harness bolts since you performed an engineering no no. The bolts should never be inserted from the bottom. If they loosen up they can fall out. If the bolt were installed from the top you would at least have a chance that they will stay in place. The cage looks great.

I have not shopped it in a while, but last time I built a cage the DOM was twice the cost of regular tubing. If you are not machining the tubes regular seam should work fine. I used 1 1/2" schedule 40 black pipe ( a demolition derby car) because the outer diameter fit into my POS Harbor Freight bender mandrel and did not kink so bad. We did end up flipping the car and all it did was bend the giant 14 gauge shark fin that I welded on the roof. That has a 1.900" OD 1.610 ID and .145 wall. The 1 1/4 has 1.660" OD and .140" wall, it should hold up a glass car from crushing you if you are on a budget. They also make tight radias weld on elbows with same dimensions. but I have more time than money in most cases.

Fubar stop and look at the wall thickness of what you used and the DOM tubing, then look at the weight you have vs. DOM and that is not counting the stragth of the DOM VS. your house pluming tube. Personaly I would not trust Black pipe. Remember this is a safty thing and is it worth the price of a life. By the way good eye on the incorectly installed bolt. They might want to put a bushing in it then they can tighten it down and it will be stronger that way.

The point I was trying to make is that regular tubing is half the cost of DOM. My understanding of the DOM is that it was held to tighter dimensional tollerance because of the process. When I say "regular tubing" I am not speaking of black pipe. But hear are the specs for black pipe: 1 1/2" x .095 wall tube weighs 1.426 lbs per foot.1 1/4" .109" wall black pipe is 1.80 lbs per foot. The 1 1/4 ( 1.66 " OD ) with the .140 wall is 2.27 lbs per foot. The last time I spoke with an engineer about some tube trusses he used cross sectional surface area and the process to calculate stregnth. Also tension and (or) compression as a factor. All the fatal roll cage failures I have heard of have been from weld failure due to chrome plating chrome molly tubing. Suspension failure is the same. So if you are worried about safety buy a Volvo. Or get the SCORE racing specs for cage construction and stay away from hack welders. And if you are concerned about 20lbs of extra steel and you happen to weigh 300lbs it would make more sense to step away from the cheesburgers.....

Most sandrail type buggys (before the long travel buggys) were built from 1 1/2"x .095 welded steel tubing. They were and are plenty strong enough to take on just about any offroad punishment you can throw at them if properly designed and welded. If you are building a cage to protect you from a Soccer Mom driving thru your buggy with her SUV it ain't gonna happen. Your better off keeping the buggy as light as possible so it will basically get knocked out of the way instead of getting run over. Build the rollcage to protect you in the event of a rollover. I know from personal experience that a SCORE legal 1/2 1600 2 seat buggy built from chromoly tubing is no match for a relatively light side impact by a Trophy Truck. Fortunately nobody was in the buggy when the truck making hotlaps lost control and brakes ran into it.

Thanks Jerry for the safety wire Idea. I was going to use locktite. Im going for both now. I have not finished my installation (This winters project) Yea I know its an engineering no no, but it looks cool.... and anyway its not a real roll cage since its bolted to the pan. So in some warped way I have convinced my self that its ok???? The inserts I welded in were 3/4 Inch Diameter and reamed out to accept 3/8" grade 8 bolts and are welded through the cross bar on both sides. I went throught the same material delema. the 1 1/2, or 1 3/4 standard seam tubing is perfectly acceptable for a roll cage for a buggy. I wanted a clean cage and as much protection as possible ( I know that is an oxymoron for a fiberglass buggy). DOM is twice the cost, but whats $100 when safety is involved. Look around If you find the right supplier DOM is not so bad. I think I finally got it for $4.00 a foot. Others were trying to sell it to me for 6 - 8 bucks a foot, or my favorite Whats DOM...but im sure I can get it for you on special order. ANd for what ever its worth I talked with a few roll cage fabricators who do rock crawlers and jeeps. DOM was the way to go, but they all built cages out of regular seam tubing for most of their clients. Its a preference and what are you going to use it for thing.

Can't get these pics to post for some reason but Mel Hubbard asked me to try and put them up here. Brit John Gurney's been doing wonders with tubes for years... http://f3.yahoofs.com/users/41e6bb6cz37 ... FBk8Nsi1Ej http://f3.yahoofs.com/users/41e6bb6cz37 ... FB1.rdsNhP

Thanks everyone for the info,I think I'm going to use the 1 3/4".The only supplier in the area had regular 1 3/4 tubing with either .083" wall or .120".I prefer the .120 but having no knowledge of bending steel tubing what will be easiest to form?What precautions need to be taken if any?I had also planned on using saddle gussets on some of the welded areas for added strength,anyone used these?The individual that's building my cage has only used 1 1/2 tubing,any differences in the bending procedure other than the dies or is it all the same.You guys have built some nice cages,I will be glad when mine is completed,painted and mounted.This is the last big project on the Manx,after 2 1/2 years and a little behind schedule it's nearing completion.

The only problem forming the thinner tubing is that it likes to kink. You can fill the tubes with sand if that becomes a problem. The "k factor" or bend deduction will be different when you change OD. Can the guy building it get the material he likes to use? It seems like a steel yard should be able to order anything made of metal. Or just buy it off the internet direct.