Centre Support Spars and Strengthening

I had a bit more time than I originally thought before I flew out next and I really wanted to nail these centre support spars. It was a lot harder of a task than it seemed to be as a lot of thinking took place. I wanted to keep the spars to look clean without any protruding joins and match the rest of the subframe so I opted for 20mm OD pipe with a 1.6mm thickness as this could be easily bent with a conduit pipe bender we had floating around a work. The thing that worried me the most was where would I have these spars mount on the rear of the subframe and to make sure that the point at which they mounted was structurally strong enough. So before I started on the centre spars I had to weld in some plates which wasn't a bad idea as it made the whole underside of the towers quite robust.

Here is what was done:

After that was complete I made up some removable brackets that the spars would be welded to so that they could be removed at any time if needed. Amongst all this the front spar I previously had was scrapped and had to be redone using different mounting brackets than previously. I used 25mm OD 2mm thick pipe for this.

Now back to the centre spars. I decided to go through the centre near the exhaust rather than around the side because of where I mounted the front brackets and I figured it may be a better spot for its intended use - restricting flex down the centre of the subframe. Getting the bends at the right angles on a singular piece of tube wouldn't be very easy so another idea was making up a few bends then welding them together. I really didn't to lose any structural strength when doing this so a mate from work handed me a piece of lathed down pipe that would fit inside the spar pipe. This made aligning the pipe ends together a cinch and also made for a better weld over the normal butt weld.

This is what was done.

So after a few hours of messing around grinding and twisting the pipes into position, started to tack welding the pipes and brackets to each other. I was almost finished doing the centre spars, all that was left was to finish the welds in the welding bay and clean up. One thing I would of done differently was doing these whilst inside the car, because I did find that my left mount spar was slightly out by 2mm due to the overheating when welding the strengthening spar. So this could of been avoided but it was as simple as the welder was in a different location. Not a big problem though as I could still mount the subframe inside the engine bay no worries, a little bit of TLC does the trick.