Given that the Elise is, for me, primarily a track-toy, modifying it to accept a harness that’s compatible with my HANS device and adding a fire extinguisher were high on my agenda when I bought the car in March. In doing so, however, I wished to keep the stock seat (it fits me well, and I like it) and the stock three-point belt. I thought I’d share what I’ve done, if only to inform the debate about these issues. If I’ve followed a different path than others on the boards, it’s only b/c it felt right to me. I don’t claim to have any real expertise on automotive/racing safety, although I have gone through this exercise before and I did solicit a lot of advice and read carefully all the materials that came with both the HANS and the harness. Several members of the community -- including especially Stan, Sleepless (and his shop, Cantrell Motorsports), Jack, Arno, Brad S., and Lucien -- were generous with their time/advice and deserve a public note of thanks. I also got some useful advice from Lotus Motorsports in the form of both telephone calls and the opportunity to review their installation instructions for their six-point harness and competition seat.
I broke down and bought the Sector111
Halon extinguisher, just because it is the coolest looking fire extinguisher on the planet, and I like the look and feel of the mount and the mounting location.
I bought a Schroth Profi II -- HANS six-point harness from HMS Motorsports. While I believe in supporting our sponsors, I’ve long felt that HMS is one of the best suppliers of safety gear to racers/trackers, and they were very helpful in terms of providing technical advice during the installation.
There seems to be a growing consensus surrounding the merits of using a 2” lap-belt (it sits better on the pelvis and can be tightened further than a 3” belt) and HANS recommends the use of 2” shoulder-belts because they tend to sit better on the yoke of the device. Schroth uses a webbing material that stretches less for this particular harness than it uses for its non-HANS compliant harnesses.
Based on Schroth’s literature, I did not buy and would discourage anyone from using a sternum strap to keep their harnesses from spreading. This seems best addressed by (i) preventing the shoulder-straps from spreading on the bar (for this, I used a 5” canvas climbing loop from REI), (ii) routing the harness through appropriately placed holes in the seat, and (iii) complying with the routing, strap-lengths, and geometry recommendations from your harness manufacturer.
Harness Bar and Shoulder-Straps:
I bought the Sector111 4Tress bar. It seems well designed and solid. I like the fact that it attaches using stock threaded holes in the rollbar and (unlike the last rollbar I installed) didn’t require hacking up my interior. I like the fact that the bar sits only 8” away from the top of the HANS yoke when I’m in the car, which is about as good as you can do with an adjustable seat. What I don’t like is the fact that the bar sits higher than my shoulders, so my shoulder-belts slope downward (by about 10 degrees) from the bar to the top of the HANS. This is not ideal (ideal would be horizontal) but the good folks at HMS assured me that the slope is mild enough to be acceptable.
I wasn’t comfortable using the stock seatbelt mounts for my lap-belts b/c (i) that requires the mounts to support the stock belts AND my aftermarket harness and (ii) it results in the entire load placed on the sub-straps and lap-straps being transferred through the seat-rail to threaded fittings that attach with relatively small M8 bolts. While this is undoubtedly fine for street use (who am I to second guess Lotus?), I felt more comfortable using 7/16th inch UNF bolts mounted through the aluminum cross-chassis member that the stock seat-rails bolt to. This is a c-shaped beam with vertical members both fore and aft, and I liked the fact that it abuts (and seems bonded to) a major chassis member, so any load applied to it will be solidly transferred into the chassis.
This is the exact approach taken by Lotus Motorsports according to their instructions for their competition seat. The bolts are supported under the car by backing plates that are glued and riveted to the bottom of the chassis. The mounts are roughly 16” apart (which is ideal according to Schroth). What I don’t like about this is that (i) the downward angle of the belts to the floor is only 50 degrees (the ideal angle is 60 degrees according to Schroth, but that cannot be supported by the aluminum skin of the sheer-panel that forms the floor) and (ii) the mounts are assymetrical -- the right-hand bolt is located just to the left of the seat-rail (i.e., between the two seat-rails), whereas the left-hand bolt is located just to the left of the seat-rail between the rail and the chassis-beam that runs down the outside of the car (i.e, outside of the two seat-rails), but the offset distances are modest and there wasn’t much choice. All-in, I’m comfortable with the approach.
I elected to have holes cut in the stock seats. Alas, the shop that did the job cut them too small to permit the harness to be easily shoved through the holes, so I will likely return to have the holes enlarged after I return from Thunderhill this weekend. Having spent some time with the seat, I no longer harbor any concerns that modestly-sized and appropriately-positioned holes will threaten its integrity in the event of an accident. I recognize that Lotus doesn’t recommend this, but I am comfortable with the approach. The stock seat may not leave enough clearance for the HANS (which recommends 2” of distance between the back of the HANS and the seat). This may be aggravated by the slight downward slope of my shoulder-straps which seems to pull the device backwards, however. I may revisit this issue later, after I’ve spent some time on the track.
Because much of the load has been shifted to the rollbar (via the shoulder-straps) and the chassis (via the lap-belt bolts), I felt comfortable attaching my sub-straps to a Sector111 anti-submarine bar. The bar is braced by a beam that runs across the seat and seems pretty stout. The resulting location of the sub-straps is close to ideal, and the short run of the straps is great. What I don’t like about it is that there’s a lot of hardware in a pretty tight space, so I may look into ways of lowering the attachment under the seat to create more room. While Schroth strongly discourages the use of a five-point harness, the tightness of the Elise may merit it. I will have to see how it all feels at the track this weekend.
I'll try to post some photos if I can figure out how to do so. Hope this is of some use to folks.