techbod Posted August 21, 2014 Share Posted August 21, 2014 Car is a 1989 live axle. My current harnesses are a pair of Willans with 2" shoulder straps and are pretty old (the FIA label says ok to 1985) so I was going to replace them with a set that had 3" shoulder straps and are more up to date. I bought a set of Caterham/Luke from another club member and went to start the fitting process when I came across the problem that the original harness bolts look like they are 5/16ths and not 7/16ths. The bar they are bolted too (forward of the roll bar) is 1" box - I assume that is standard? So what are my options? Use a sleeve/bush with the 5/16ths? Drill out the box to take 7/16ths? (It doesn't have a captive nut under the bar, its uses a nylock). Or just leave well alone... Link to comment Share on other sites More sharing options...
Dave H Posted August 21, 2014 Share Posted August 21, 2014 Hi techbod, My '86 chassis has a replacement harness and I used a "tophat" type spacer that allows the harness some movement, but the 5/16th bolt holds the spacer solid. I think they came from Redline. Dave H Link to comment Share on other sites More sharing options...
Area Representative Golf Juliet Tango Posted August 21, 2014 Area Representative Share Posted August 21, 2014 I have some tophats. I'll go and measure them. EDIT: internal dia (if imperial) is 7/16" and the narrow part of the tophat is 9/16" Edited by - Golf Juliet Tango on 21 Aug 2014 15:30:23 Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted August 21, 2014 Member Share Posted August 21, 2014 A reliable source of top hat washers would be very helpful: I couldn't find one a couple of years ago. Jonathan Link to comment Share on other sites More sharing options...
techbod Posted August 22, 2014 Author Share Posted August 22, 2014 Thanks for the replies. Its good to know I'm not the only one with 5/16th bolts, and that a bush/top hat etc is an acceptable method of sorting out the problem. I could make some up (have a lathe), or might just speak to Redline, however having looked at the end of the lap belt, first I need to make sure that I can make this work. It turns out the current lap belt ends are anchored by 7/16ths eyes (this sort of thing here) and are fixed with a snap type fitting (http://www.stroudsafety.com/Images/Restraints-SeatBeltEndsLg.jpg) which the replacement belts don't have. So I need to unscrew the eyes, but I just have to assure myself that they are screwed into a captive nut or threaded boss, rather than just a nylock nut (like the shoulder straps) or I'll end up with a nut floating around and nothing to screw into and possibly have to remove the inner panels to sort. I'm using the car this weekend so it will have to wait until next week before I can pull out the seats and check. Edited by - techbod on 22 Aug 2014 22:30:26 Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted August 22, 2014 Member Share Posted August 22, 2014 If you're going to make a batch I measured some top hat spacers that work well (and some that don't). Jonathan Link to comment Share on other sites More sharing options...
techbod Posted August 23, 2014 Author Share Posted August 23, 2014 Those measurements would be good to have thank you, they will undoubtedly save a whole lot of trial and error... Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted August 24, 2014 Member Share Posted August 24, 2014 The batch I had made were: 11.45 mm internal bore throughout Base section 19 mm outside diameter, 4.7 mm height Upper section 14.21 mm outside diameter, 5.2mm height above base. For me the crucial dimension was the height of the upper, thinner section. My new Titon belts had thicker plates than the originals and I needed taller spacers to allow them to swivel. 5/16" = 7.94 mm 7/16" = 11.11 mm Jonathan Link to comment Share on other sites More sharing options...
techbod Posted August 25, 2014 Author Share Posted August 25, 2014 Thanks Jonathan, most appreciated. Link to comment Share on other sites More sharing options...
techbod Posted September 8, 2014 Author Share Posted September 8, 2014 Note to self: Remember never, ever, assume anything. Just because the bolt removed from the top harness mounting point is 5/16ths, it doesn't mean the hole they came out of is actually 5/16ths At some point, someone used a combination of washers, rubber spacers and nylocks to allow a Willians harnesses, with a 5/16ths hole in the top mounting point to be 'mounted' in a 7/16ths hole with a 5/16th bolt. The top mounting point is 'T' shaped on this particular harness, making it very thin where it bolts to the car. You couldn't open the hole out to 7/16ths there would be so little meat left on each side. A quick play with a micrometer says it would be very approx 3.8mm (or 5/32") left on each side if drilled to take a 7/16ths bolt. Hence the rather unorthodox mounting technique I assume. Relived to have got to the bottom of it, not sure I would have wanted to tested it in an accident... Link to comment Share on other sites More sharing options...
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