After fitting the bucket seats, I needed a half cage with harness bar. I want to run 6-point harnesses on track with the seatbelt on the road. I don`t dispute a full cage is safer on circuit, but it’s a pain to live with on the road and as this car is multipuapose, a ull multipoint cage simply isn’t something I considered.
Corin at SW Motorsports reached out and asked if I was willing to take my R8 for them to scan, they’d build the cage and fit it whilst I was there.
Sounded like a plan to me so I drove across the M62 and arrived nice and early. They are only just over an hour away so it was no problem driving across.
Pulled into the workshop
Removed the seats then Corin and I covered the rear half of the cabin in reflective self adhesive dots.
Why ? So he could take a mm accurate 3d scan of the interior
They help the scanner to know where it is and allow it to build the 3D version of the car.
Once done, he loaded up Fusion and set about designing the main hoop, rear stays and harness bar
A click of the mouse and the interior is removed leaving only the cage
This is where the software is so good. MSA regulations specify how much the hoop can be tipped back from the vertical. Staying within that limit meant the seatbelt wouldn’t be able to be used, it would hit the hoop. We had a discussion and both agreed the hoop would have to lean back more than we’d like, but to maintain on road use it was the only way.
This photo from later on shows how the hoop is only as far back as it needs to be so it clears the belt
I started by removing the bulkhead trim in the engine bay to expose the rear sound deadening
Remove the side trim bracket
I cut slots in the insulation to fold back the part we needed, it’ll become obvious later
In the cabin, initially we were going to use rectangular spreader plates
These were aligned using the captive threads Audi installed for the brackets in the engine bay
Cut the insulation
Remove and expose the heat reflactive deadening behind
You can see the captive threads clearly now
Peel off the deadening
Drill out the captive threads
These holes will be used to bolt the spreader plates to the bulkhead. At this point Corin realised that as the rear stays were at quite a steep angle, the tube would overhang the rectangular plate.
In seconds he’d modified the plate to suit
Sound deadening trimmed and plate fitted. (I didn’t have a better photo)
Then the clever stuff happened. This was sent to another program that controls the tube marking and profiling
The machine then labels each point on the tube with a sharpie, engraves where the tube will sit and also cuts the intersection profile. Perfectly.
Corin looking quite pleased with himself as we’d just test positioned the main hoop.
With the hoop bolted to the seatbelt mount, it was positioned and the rear stays tacked in place in the car
This was then removed, fitted to a bare jig base and the jig modified to suit the bars. This will then be kept for any future R8 cages and they won’t need to tack weld it into the car
Once fully secured in the jig, everything was welded up
The Hoop and rear stays were put back in the car and bolted into place. The engraving for the harness bar can clearly be seen, as well as the profiled end of the bar itself.
The engraving allows accurate positioning and the profiling was absolutely spot on !
The planned clearance between the harness bar and the rear stays was exactly as expected.
This was again tacked, removed, the Jig harness bar added and then welded up
Logo attached.
To stop the harnesses from sliding around the curve on the harness bar, some C pieces were cut on the laser cutter
You can just see them on this photo, before the bend in the harness bar. This is the cage being hand-prepped before powdercoating.
We then tackled the rear trim cutting. What a pain ! mark, offer up and repeat.
Cage bolted in after powdercoating
Back in the engine bay, you can see the locknuts that are behind the sound deadening I removed previously, I drilled out the bracket to accept the larger bolts, so that is secured with the same nuts
The insulation now folds back to cover the nuts. I appreciate this is the passenger side, I don`t have the same photo of the drivers one.
Bulkhead trim bolted back up
Interior rear trim refitted. It’s not the easiest thing in the world and requires quite a bit of force as everything clicks into place. It certainly won’t be working loose anytime soon, although removing it for any maintenance will be fiddly.
I mentioned the seatbelt bracket earlier, this is the combined lower hoop mount to the chassis and repositioned seatbelt
I’m very happy with the fit of the hoop and harness bar
If I hadn’t been involved and just received the half cage after ordering, I wouldn’t have understood why the hoop was tilted back. Watching Corin design the cage, seeing if it was far enough forward to clear the seatbelt it would be alongside the drivers head which is obviously unwanted in an accident, made me extremely pleased with the finished design.
Refitted the seats.
With the schroth 6-point Harnesses
The total weight for the cage in CDS tube, including hardware, securing bolts, reinforcing plate etc would be 14.0kg
I went for the full T45 hoop, harness bar and rearstays which with hardware is 9.7kg