CtrMint Posted November 23, 2020 Author Share Posted November 23, 2020 Chris, Are you sure the runners are different? Luckily I've got the same seats in the 620R and 420R but I can't see any difference. Do you know the part code.Thanks Link to comment Share on other sites More sharing options...
CtrMint Posted November 23, 2020 Author Share Posted November 23, 2020 Found them, does make you wonder what the difference is.https://caterhamparts.co.uk/seats/6619-bespoke-runners.html Link to comment Share on other sites More sharing options...
ChrisC Posted November 23, 2020 Share Posted November 23, 2020 What we do know is the holes for the 620 seat are drilled in a different location to the standard Tillet seat, so even if the runner is the same dimensions it's in a different location. http://www.caterhamr500.co.uk/2016/03/620r-countersunk-seat-fasteners.htmlDaniel French posted about it on his blog in 2016. Link to comment Share on other sites More sharing options...
ChrisC Posted November 23, 2020 Share Posted November 23, 2020 They are 100% different, the standard Tillet doesn't have the captive nuts holding them to the floor. What the dimensional differences are, I don't know because I have never seen the two parts side by side, What I do know is when I spoke to the factory about my build, and spoke about the runners and the possibility to using the 620 runners on the standard Tillets they said it wasn't possible. Link to comment Share on other sites More sharing options...
CtrMint Posted November 24, 2020 Author Share Posted November 24, 2020 Chris, Thanks for the help with this. I certainly wasn't aware of the different runners, it might explain the source of the issue. Link to comment Share on other sites More sharing options...
ChrisC Posted November 24, 2020 Share Posted November 24, 2020 If you look at Daniel's blog photo, which shows the rubber bung from the original Tillet seat fitting holes. You can see the 620R seat holes are drilled about 2 - 3 cm back, assuming the photo is taken from the passenger side. I think the photo is taken from the passenger side because the exhaust isn't present, and I think you can see a rear wheel blurred in the background.I have no other evidence other than this photo from 2016, but I suspect it shows the 620R seats have the runners fitted further back in the floor plan, and this is the cause of your problem. Personally I would contact CC to gain advice about fitting a crutch straps with 620R seats and lowered floors, but understand this may be complex. I have found photos of 620R seats with crutch straps from google image searches, so it must be possible. Link to comment Share on other sites More sharing options...
CtrMint Posted November 25, 2020 Author Share Posted November 25, 2020 I've dropped Simon Lambert an email, I'm trying to get an update on the 620R cooling revisions, things have gone rather quiet. At the same time, I've asked about the crutch strap. Link to comment Share on other sites More sharing options...
CtrMint Posted November 28, 2020 Author Share Posted November 28, 2020 This issue is now resolved.This morning with the help of a mate we blitz through a number of setup configurations trying to find a solution. We also started the process of designing a brace across the back. In the end, we reverted to my original thought of reversing both rails, which places the seat further back on the rail to start with. This provides sufficient clearance to achieve the same seating position without the strap retainer. This approach does require the forward most seat hole in the offside adjustable rail to be elongated. It's out by a few mm. I've reinforced the hole with a large thick washer which doesn't foul the runner.It's a simple fix, but I think better than bracing the rear etc. I'll post more info in my up coming blog, although we didn't get any pics. Simon Lambert has promised me an update on the 620 cooling next week, he's also going look into this issue. I suspect it's something that's been overlooked, but we'll see what the feedback is. Although I'm happy with my solution. Thanks all for the support, I certainly didn't consider the fact the rail was bespoke to the 620 seats. Link to comment Share on other sites More sharing options...
7 wonders of the world Posted November 28, 2020 Share Posted November 28, 2020 "I certainly didn't consider the fact the rail was bespoke to the 620 seats."It would seem neither did CC.... or perhaps your the first owner wanting a 6 point.... Link to comment Share on other sites More sharing options...
aerobod - near CYYC Posted November 28, 2020 Share Posted November 28, 2020 I would say that if the different mounting holes can't be used between the rails and seat, then shortening the rails behind the rear most mounting point on the seat may be the best solution with no particular risk, as crash loads are taken through the harness as opposed to the seat rails. Link to comment Share on other sites More sharing options...
CtrMint Posted November 28, 2020 Author Share Posted November 28, 2020 James, I'm not following your comment. The harness including all points are mounted on as designed. The near side rail is reversed, without any other changes, It's only the offside rail front bolt hole which has a minor change. I'm not sure why this represents an issue. Link to comment Share on other sites More sharing options...
aerobod - near CYYC Posted November 28, 2020 Share Posted November 28, 2020 Mark,I thought you still had the issue of the rail on the offside still hits the harness mount plate due to the fact that a lot of the rail protrudes behind the seat mounting point. That is the bit that looks as though it can be cut off without affecting any functionality or safety, allowing the seat to slide back further without that rail hitting the mounting plate. The only potential issue I could see is that the seat locking lever may not lock the seat in the most forward possible positions if the rear of the rail with the locking holes in it is shortened. Link to comment Share on other sites More sharing options...
CtrMint Posted November 28, 2020 Author Share Posted November 28, 2020 Understood. The solution that I've got is nice and simple and I can't see any safety concerns.still can't account for the extra Tillet spacer on the 620. Link to comment Share on other sites More sharing options...
aerobod - near CYYC Posted November 28, 2020 Share Posted November 28, 2020 Hi Mark, sorry I missed the bit in your earlier post of elongating the hole to be able to reverse the offside rail, sounds like a perfectly good solution to the problem. Link to comment Share on other sites More sharing options...
CtrMint Posted December 2, 2020 Author Share Posted December 2, 2020 Finally had chance to write the blog post.https://www.caterham7diaries.com/post/crutch-strap-install Link to comment Share on other sites More sharing options...
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