Stuart Walker
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| posted on 24/1/07 at 10:44 AM |
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SVA Tester advice: Upper Seatbelt mounts
Hi,
Just thought I'd share this with everyone in case someone is in the same situation as me.
My upper harness mounts are welded onto the top of the chassis rail, with a captive nut welded inside them (same as many other people, i believe).
This failed as insufficient strength, the tester said the pillar might break forwards and come off at the welds in the event of an impact.
I emailed him for some advice on a number of possible solutions (basically I don't want to have to take everything apart to fix it), and the only
acceptable one was this one:
Don't know if this is of use to anyone, but there you are!
Cheers,
Stu
 
Rescued attachment Copy of seatbelt_mounts.jpg
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James
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| posted on 24/1/07 at 11:10 AM |
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I'm not surprised it failed. As it says in the SVA book, you have to allow for the force exerted on the mounts to be 20x your weight. 75kg x 20
= 1500kg on a small piece of 16g tube!
Anyway, good luck sorting it.
Cheers,
James
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"The fight is won or lost far away from witnesses, behind the lines, in the gym and out there on the road, long before I dance under those lights."
- Muhammad Ali
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PaulBuz
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| posted on 24/1/07 at 11:11 AM |
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Oh dear
I can see what he means about the original, but the solution does seem a little OTT.
Could you not do as I have below, or that unacceptable as well?
I first fully welded it on all sides, then welded 'L' shaped pieces on top to give an even bigger welded surface.
 
Rescued attachment l095.JPG
ATB
Paul
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roadrunner
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| posted on 24/1/07 at 11:14 AM |
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My Indy failed on something similar, mine is an older chassis , new ones have a bridge in front of them, option 2 should pass with no problems,
could'nt you shorten the length of the mounts, as it all comes cown to leverage.
If you look at the picture above you will see that you need humpback bridges in front of the mounts.
[Edited on 24/1/07 by roadrunner]
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bartonp
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| posted on 24/1/07 at 11:29 AM |
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quote:
Originally posted by PaulBuz
Oh dear
I can see what he means about the original, but the solution does seem a little OTT.
Could you not do as I have below, or that unacceptable as well?
I first fully welded it on all sides, then welded 'L' shaped pieces on top to give an even bigger welded surface.
My gut feel is that while the welds to the extensions probably won't fail here due to the L pieces, the top cross tube they are welded to may
well rotate/deform under loading - or even rip the side of the 16g tube out. Hence the triangulation of the 'approved' solution.
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Stuart Walker
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| posted on 24/1/07 at 11:40 AM |
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James - I only weigh 60kg! 
But yes, thinking about it it does make sense really (would like to point out at this stage that I bought the car part-built!!)...
Paul, I did suggest something similar to yours as one of my other options, but without the L-shaped bits. Has yours passed or not tested yet?
I can't shorten the mounts or they would be lower than the seat holes, with all the other SVA and general painful consequences of that...
Cheers
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bartonp
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| posted on 24/1/07 at 11:41 AM |
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quote:
Originally posted by James
I'm not surprised it failed. As it says in the SVA book, you have to allow for the force exerted on the mounts to be 20x your weight. 75kg x 20
= 1500kg on a small piece of 16g tube!
Anyway, good luck sorting it.
Cheers,
James
... and in this case two on the same bar = 3 tonnes (assuming you have an equal weight passenger)
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JAG
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| posted on 24/1/07 at 12:12 PM |
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I had the same problem - not enough height at the top seat belt mounting. I created this;
 
seat belt mod' finished/fitted
It worked/passed at Nottingham SVA. There are some more pictures in my archive if you're interested.
Justin
Who is this super hero? Sarge? ...No.
Rosemary, the telephone operator? ...No.
Penry, the mild-mannered janitor? ...Could be!
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the_fbi
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| posted on 24/1/07 at 12:14 PM |
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My Westfield has 2 short threaded bushes welded to the back of that same bar, apparently it does need a sleeve adding to make it high enough too,
which will enable more leverage too, not a good thing.
As far as I'm aware, my chassis is the same as the current WF chassis so if you moved your tube onto the back of the crossmember, even with
height extension it would pass SVA. Seems mad, but works for WF. Although its only a 1" height up on the WF which is less than your picture
shows.
Edit: WF's is the same as Justins picture above.
[Edited on 24/1/07 by the_fbi]
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PaulBuz
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| posted on 24/1/07 at 07:16 PM |
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quote:
My gut feel is that while the welds to the extensions probably won't fail here due to the L pieces, the top cross tube they are welded to may
well rotate/deform under loading - or even rip the side of the 16g tube out. Hence the triangulation of the 'approved' solution.
But all of my tubing is 2mm thick ,I can't see it bending over such a small length
....Can it!!
ATB
Paul
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907
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| posted on 24/1/07 at 08:10 PM |
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I don't think the short upright length would bend.
I think the cross member would twist.
Looking at the off side of the car the short upright would end up pointing at 2 o'clock.
IMHO
Paul G
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Liam
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| posted on 24/1/07 at 11:29 PM |
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Does anyone know if it's OK with SVA man to have the harnesses fed round a bar on the rollbar? I mean have a horizontal bar at shoulder height,
but instead of a bush tube welded through it and a bolted harness mounting, simply wrap the strap round the bar and through a buckle. My mate has
harnesses mounted this way in his MR2 track car. Seems a good method to me - not only will the bar never rip out, but you also avoid a sharp 180
degree fold on the strap itself.
A bit like what you see in this piccy i googled (dunno what this is in). I guess it's a question of can you remove the normal bolt mount fitting
(is the strap usually sewn round it?) and do you have enough strap length - or would any harness be mountable this way?...
Liam
[Edited on 24/1/07 by Liam]
 
Rescued attachment harness mount.jpg
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Marcus
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| posted on 25/1/07 at 08:58 AM |
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My mounts are welded to the roll bar, but I can't see why wrapping round would fail. Many rally cars use this method.
Marcus
Because kits are for girls!!
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bartonp
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| posted on 25/1/07 at 09:40 AM |
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quote:
Originally posted by PaulBuz
quote:
My gut feel is that while the welds to the extensions probably won't fail here due to the L pieces, the top cross tube they are welded to may
well rotate/deform under loading - or even rip the side of the 16g tube out. Hence the triangulation of the 'approved' solution.
But all of my tubing is 2mm thick ,I can't see it bending over such a small length
....Can it!!
Nooo - not the short bit sticking up with the thread in it - the cross tube it's welded to could deform/twist. The triangulation is dirctly
transferring this moment into the forward tube...
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Doug68
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| posted on 25/1/07 at 10:10 AM |
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Reading in the February 2006 issue of “Racecar Engineering” there was an article on WRC safety covering research done at Cranfield University. The
salient bit for this discussion was that at:
60g Deceleration you’ll get a good concussion.
80g Deceleration you’ll get massive head injuries.
100g Deceleration will kill you.
My thought is that I’d want the seat belt mount to stay in place even at 100g, even if only to make identifying the remains easier. So allowing for a
fat bloke and spreading the load between the 2 that’s 5 tonnes a piece the mounts should take before they let go.
The other interesting point was that none of their testing resulted in g loadings of less 20g and that was hitting something solid at 50km/h with a 1m
thick crumple zone on the vehicle.
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goodguydrew
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| posted on 26/1/07 at 02:17 AM |
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If you are using two roll hoops on the car, can the eyes be screwed into horizontal threaded tubes welded into the hoops, two eyes per hoop, at the
appropriate shoulder height. I think it might be a way to have the belts at the right height without looking too obtrusive.
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wilkingj
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| posted on 26/1/07 at 03:11 PM |
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quote:
Originally posted by Stuart Walker
James - I only weigh 60kg!
Cheers
What about your Passengers, or the next owner if you sell it. It has to conform and above all be safe.
Lucky you only being 60kg. Me and my son are 20 St Each Thats 128kgs apiece!
ie a 1/4 Ton of blubber... Oops I meant People.
Now you know why I built a Viento... I'm a Bat F'Stard
PS... I could get a very very Cheap increase in power, simply by driving Solo and loosing weight... Cheapest Bhp/Ton power gain ever
1. The point of a journey is not to arrive.
2. Never take life seriously. Nobody gets out alive anyway.
Best Regards
Geoff
http://www.v8viento.co.uk
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tks
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| posted on 2/2/07 at 08:38 AM |
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mhhh
20Geee thats allot!
in fact i think that if the bracket will survive (staying rigid) your brains wont!!
in a accident what we want is absorp the amount of energy basicly what we want is that the duration of the impact is as long as it can bee because it
means less energy per second wich results in less force on the body!
in the NL couple of years ago, 2 (of 3) solders where killed in a accident with a Leopard and a train.
the train impacted the tank in the side!
and shove it with him 50mtrs..
due to the high G forces the 2 inside where killed.
the one who survived the accident whas the one wichs sits on the deck of the tank he jumped off the tank....
i woudn´t reinforce your tube anymore.
making it rigid won´t help you. (L person)
i´m sure that it will bend but that will take away force wich was destinated on your chest... its true that you will move a bit forward (sow you might
brake some fingers/wrist)..
the solution your sva inspector gave is a realy good one but i wouldn´t complicate things anymore.
i would weld 2 3mm plates (triangual) in front of the tube.
i think it will be a bit weaker but again you don´t want your mounts to survive 100G trust me.
my dad had a accident with 50MPH in a tree (frontal) the airbag of his vauxhall omega didn´t come off sow he was only taken by the auto seabelt
spanners.
the shape/surface of the skin of the tree could be readed in the bonnet! the omega is rearwheel driven sow the rearwheels where facing inwards (toe
in!)
only thing he had was a broken wrist (1 bone) and a totalled omega 2.5TD
(p.d.) the reason he changed cruisecourse whas because of a drunken person on bike wich crossed the street
he didn´t wanted to hit him and just turned the wheel.
Tks
The above comments are always meant to be from the above persons perspective.
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