I’ve finally managed to get the roll cage tubing, as seen in the picture. Astonshingly, it’s taken me about three months to get this. I went to the suppliers that Jeremy recommended, Tube Engineers of Market Rasen in Lincolnshire, as that seemed sensible. Since then I’ve had a long stream of excuses and woffle including “he’s in France”, “we’re setting the machines up for 38mm next week”, “oh, I’d forgotten about you”, “I’ve lost your email” and “we’re notching the tubing”. The last is special because I didn’t ask them to do this. In fact, a selection of the tubes arrived notched in a useless manner (how could they know what angle I needed them notched at?), what’s more, the front hoop (the only difficult bit because that’s the only bent tube) arrived a different length from what my drawing and my email specified.
However, I’ve been waiting so long I decided to just work around the problem which I think I can. I certainly shan’t be putting any business their way in the future though.
Still, at least I could get going on this now. First thing was to fit the diagonal to the rear hoop and weld that to the chassis. So, I tacked things together and tacked the hoop to the chassis after cutting the bottom of the legs so that it would all end up vertical when it was fixed to the non-horizontal plates on the chassis. However, with it in position I realised that it could easily be too far forward in that there might not be room for a crash pad behind my helmet. So, I fixed a bit of hardboard to the hoop and checked how much clearance there was; in fact I videoed myself as it’s really quite difficult to work out how much clearance there is around your helmet when you’re wearing it!
That testing showed that the hoop was indeed too far forward and I had to move it back to the position that you can see in this photo. The problem with this, if you look at the bottom of the hoop, is that the legs are no longer above the chassis.
So, I had to 
extend the hard mounting points on the chassis which I did by welding in a chunk of box section in as shown in the photo, and then extending the plate I’d already welded to the top of the chassis.
With that done the hoop seemed to be fine, although the upcoming problem is working out how to attach the harnesses to the car. I’ve always known this was going to be an issue but I’ve never worked out what to do about it. There’s really two possibilities. One is to weld an additional horizontal harness bar into the cage over which the harnesses will loop before going to the chassis mounts. (This is what I did on the Fury when fitting the HANS device.) The second is also to weld an additional tube into the cage, but to use that directly for attaching the harness to. Any suggestions gratefully received.
Anyway, with all that sorted I welded the diagonal properly into the hoop and welded the hoop to the chassis.
Then I had a nice cup of tea.
Next up was the backstays. As I’ve mentioned I wanted to make these removable. So, I turned some lumps of steel so that I could weld a pre-made insert into the end of the tubing into which I could mount a rod end. The joints I’m using are actually rather more expensive that the ones I normally use. They’re rated at about twice the maximum radial load that a normal cheapie joint is rated at. I decided I wanted to do this properly, you see.
I then welded some mounting to the cage and the end result is shown in the photo.
So, that meant that the back end of the roll cage was all done, and a view of the whole rear end is also shown.
I now had to fit the front hoop. First thing, though was to again check that there was sufficient clearance when I was wearing my helmet. So, I cut the base of the hoop at the correct angle for mounting it to the chassis (although I don’t yet have the hard points in the chassis) and held it in position with, errm, two G-cramps and a length of ½” tubing held in place with gaffer tape. Luckly, the tubing is CFS so it should be strong enough.
With that done I again videoed myself climbing in and checking this. You should think yourselves luckily that I’m not showing you any of this riveting video. The conclusion was that it seemed to be fine.
So, the next job is to put the hard points in the chassis and weld the front hoop in place. Then I need to do the roof bars.
The problem with all this is that the cage is horribly heavy. The regulations have changed and the whole thing is much heavier than the equivalent cage I have on the Fury. Oh well, I suppose there’s not much I can do about that…
Finally, the dampers have moved on a bit. I’m now being promised these at the end of January which will be OK for me; I’m getting more and more convinced that I’ll need to start the new season using the Fury, to be honest so it’s a good job that I haven’t sold it. To tease you a bit, though, here’s the latest rendering of the damper and reservoir!
I agree with your comment about the heavyness of the hoops with out even feeling the weight the car looks top heavy! what do the regs have to say about the frame it is attached to? do additional braces need to be added directly under the hoops to stop the mounting tube bending?
It looks a bit odd without the bodywork, but they always do. And, the rest of the chassis is still way heavier. The BB is fairly quiet on the subject of what the cage is actually attached to apart from there being a mounting plate there. TBH, I reckon that if the cage is attached to a decently triangulated chassis, which the J15 is, then it’s OK.
T
Tim
Are you going to put any side-intrusion bars in while building the cage ? I keep thinking of doing this with my Phoenix and hiding them below the bodwork line, just to give the driver and passenger (in my case) some chance in a T-Bone type accident. Although in a race environment you will only get impacted by cars of a similar type which probable don’t ride over the chassis into the passenger compartment.
There’s already some pretty serious side-intrusion stuff in the chassis itself. I had wondered about adding another bar but I probably wouldn’t unless I removed the chassis stuff from the passenger side. I’m not planning on that just yet.
Tim
I just wondered if a rollcage size bar at shoulder level would stop or mitigate intrusions into the passenger space. The chassis side structure looks pretty low from what I see in the pictures. It is just something at the top of my list after the fatal accident involving the Westfield demonstrator.
The side structure is probably round about CoG height (something I keep meaning to measure properly). Certainly from race experience I’ve never seen anyone hit anything, or be hit by anything, that would benefit from additional bars above that height, especially from something that would be narrow enough to go between the two roll hoops.
However, you can’t make things like this completely safe; Henry Surtees’ accident last year is just the sort of freak occurance that’s essentially unavoidable, without staying at home all wrapped up in cotton wool anyway.
What happened in the Westfield demonstrator? I hadn’t heard about that.
Tim
My understanding is that a couple took the Westfield demonstrator out for a drive and a Yaris hit them. I’m not clear as to who was to blame but this is the article http://www.expressandstar.com/2009/07/23/woman-dies-in-horror-smash/ . The driver also died in hospital a few days later. I remember it being a side impact but it appears it was a head on. Much more info on the Westfield forum.
Ouch! Hard to see what direction the impact was from, especially as the nosecone appears to be undamaged, albeit unhinged. Note that that car has the Westfield cosmetic roll bar; something my Westfield had and which now rather worries me.
T