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Seatbelt mounting
Dickyboy - 6/1/09 at 09:13 AM

I know there are numerous threads on setbelt anchorages but:-
I have two loop type roll bars and am looking at lap diagonal belts. For SVA requirements I will have to fix the top mounting point to the outside edge of the respective roll bars to get the offset from centre line and height from seat squab. What ways of fixing will satisfy SVAman. One suggestion is to get appropriate diameter tube, drill out the roll bar and weld the tube in then tap the tube to accept the seat belt bolts. Would that work? any better ideas (not costing too much!!)


Mr Whippy - 6/1/09 at 09:27 AM

No need to tap the tube as the correct thread bolts are really available. The welding in of at least a 3mm thick tube through the roll bar is by far the best method. Since you are using a lap belt it is worth simply getting a set from the scrapyards from a car that has not been involved in a bash. Make sure though it is not fitted with pre-tensioners as they are dangerous to work on till disarmed. Production car upper anchorages and fittings will work just fine so simply use what’s already fitted to the seatbelts. I use red rover ones on the buggy and they cost £10 for the pair.


matt_claydon - 6/1/09 at 09:41 AM

Don't use second-hand belts unless you know what you are doing! There are numerous different types of belts with different class codes and they are not all interchangeable for different seating positions. For example most belts in front seat positions with airbags are made of a much more 'elastic' webbing than traditional belts; if used without an airbag you will likely hit the wheel in a crash.


Mr Whippy - 6/1/09 at 09:46 AM

well I did say don't use pre-tensioner belts...

best use ones out a cheapo basic car


Dickyboy - 6/1/09 at 10:00 AM

Thanks chaps, where can I get the threaded tube??


stuart_g - 6/1/09 at 10:32 AM

If you are going to drill the roll bar I believe you have to go right through and weld the boss to each side of the roll bar tube. I don't think you will get away with just one side.

Someone will clarify and correct if I'm wrong.


Mr Whippy - 6/1/09 at 12:00 PM

quote:
Originally posted by stuart_g
If you are going to drill the roll bar I believe you have to go right through and weld the boss to each side of the roll bar tube. I don't think you will get away with just one side.

Someone will clarify and correct if I'm wrong.


which your not


AdamR - 6/1/09 at 01:04 PM

quote:
Originally posted by Mr Whippy
quote:
Originally posted by stuart_g
If you are going to drill the roll bar I believe you have to go right through and weld the boss to each side of the roll bar tube. I don't think you will get away with just one side.

Someone will clarify and correct if I'm wrong.


which your not


Bugger! Are you sure? That's how I've done mine. I don't see how welding a boss through one side of the rollbar tube is any weaker than weding a boss onto a bit of 3mm plate, which is what a lot opf people do.


stuart_g - 6/1/09 at 06:06 PM

Here is the picture from the SVA manual


AdamR - 7/1/09 at 10:21 AM

Thanks for that. Just goes to show that I ought to start checking the SVA manual before doing work that will be difficult to undo!

Still doesn't make any sense from a structural point of view though. Why is the first of those and weaker than the last? Is it just about the depth of thread? My thread bosses are about 2" long, half of which is inside the rollbar tube.

Pic of my setup - though you may have to squint:

seat in situ
seat in situ


[Edited on 7/1/09 by AdamR]