Hi all. Did my first track day in the Megane last week, and now want to install proper harnesses, as I only have the oe seatbelts at the moment. I have the Recaro seats, but still am being thrown around terribly. It is quite uncomfortable, and I am sure I am losing lap time just trying to cling on through the steering wheel. My arms are jelly after just a a few laps. This is on road tyres (Michelin PS4S), so would of course be worsened considerably on sticky tyres, which I intend to use at some point in the future. I am not keen on floor mounting the harnesses, as I think the load on the seat would be primarily downwards in the event of a big shunt, and could compromise the seat, if that makes sense. Has anyone simply secured these to a rear strut bar, or am I forced to buy a half cage to attach them to. Or is there another way to mount them? Cheers Carl
You need to do your own due diligence to come up with your own arrangement (one that you are happy with) and without doubt a half cage would be the ideal. In my case I didn't want to go the half cage way, plus I didn't like the commercially available UK item/arrangement which has a horizontal bar secured by the existing top and bottom seat belt bolts - large sleeve right near your helmet doesn't seem too clever. So I went for a custom harness bar fitted to the car using 4 x 16mm (10.9) bolts screwed into the rear seat fixing points (reinforced points close to main chassis cross beam). Clearly I removed the rear seats as the car is not a daily. I found this fixing arrangement better than the others I've seen where a bar is secured using either the luggage tie-down securing points (only 2x12mm?) or the Trophy RS luggage bar fixing points (only 2x14mm?). I've attached a couple of photos - points worthy of note 1. high strength roll cage tubing was used (cold rolled seamless tube) 2. all TIG welded & reinforced feet 3. approved harness eye bolts screwed into sockets which are welded on both sides 4. height kept to the minimum but still providing the allowed max angle of -20 degrees as required for HANS device (HANS is as important as a helmet in my opinion) 5. made a wooden jig to ensure foot flanges would fit perfectly Also importantly I went for a specific 4 point harness which would remove risk of submarining - the only manufacturer I found that could do this for a 4 point harness was Schroth. I was comfortable with my harness bar design and fabrication but do not warrant it suitable for you/others - do your own research/calcs to make sure you are happy with whatever arrangement you come up with.
Thanks for the input everyone. I had a good look at yours Zoto, my thoughts are towards more triangular bracing. I have a tame fabricator to hand though, so will post up his result. Must get on with this now, got Donington booked 03rd August! Cheers
Originally I was going to include a back stay, but considered the current design adequate, based on: There will be a moment transferred to the foot but it is reduced by around half as the bar is NOT orientated in a vertical plane, but in fact more like around 45 degrees. Also the ribs on the feet will assist in strengthening this interface and all TIG welded. The M16 bolts x 4 are good for a total of around 200kN, which equates to 20 tonnes - so for a 100g crash it should hold 100kg, when considering the 45deg orientation, etc. Hopefully the chassis metal work around the seat fixing points will hold?? The 44.5mm CDM tube with 2 point load, 100g crash and my 80kg weight has a safety factor of 1.1. Also I would expect the Schroth anti-submarining harness "stitching" would have released before this, so the safety factor would be considerably greater, as peak transient load is reduced. The stitching release acts like a shear pin. So hopefully all good. Also I'd rather have this arrangement with a HANS device and Schroth 4 point harness then driving around with just a 3 point lap/sash belt. But without doubt a half cage would be fantastic.
Also forgot to mention that the threaded sockets welded into the tube for the harness loading points would further increase safety factor on the 2 point load stress calc; equates to almost a solid 44.5 tube! I suppose that's why MSA requires their specific design.
