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PostPosted: Sat Nov 03, 2007 1:08 pm 
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drmini in aust wrote:
smac wrote:
Hehe...I love this topic. Next thing to happen is someone (like me) asks how the force at a particular point in a closed system can double while the overall force somehow stays the same, and then people start arguing with bad science, and it's great! :lol:

It's just snatch block mechanics technology. The top mount in a retractable system acts as a pulley. As old as the hills, older than me even. :lol:
Ask any woodcutter or serious offroad 4WD enthusiast. :wink:


Ya but that's where the bad science comes in :wink:

The reason a pulley can lift twice as much (for the same force) or in this case exert twice the force is only if the distance is doubled. That's the important bit that gets missed from these (numerous!) threads. In this case the total distance the belt being pulled out does not change (in fact I think it halves due to the pulley, and that's how the force is the same).

I don't claim to know all the answers on this one yet, I'm still thinking (it takes a while!) but I DO know it's not as simple as it seems.

Don't get me wrong though - I completely agree using an "unre-enforced" (it's now a word) bin is a no go. The belt can't act as the re-enforcement as suggested above because it's the surrounding bin metal that's the problem. You'll either pop your mount clean through the bin metal, or as doc says pop the bin off the floor.


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PostPosted: Sat Nov 03, 2007 2:53 pm 
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Hey distance doesn't matter, it has a 2:1 mechanical advantage, force wise, even in a static system.
Basic mechanics .... :wink:
You could be pulling a 4WD stuck in mud or solid concrete, the force is still doubled.

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PostPosted: Sat Nov 03, 2007 3:08 pm 
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Personally I wouldn't like to have an accident in your mini using that belt (I wouldn't like to have an accident in any mini or other car for that matter though) as I think the bolt would tear vertically through the metal causing enough of a hole to fail . Even though there is a plate on either side it is still bolted through a single thickness bit of bodd steel . The figure used by DOTARS for accident testing is an impact of 20 G's , that means the belt mounts have to hold 20 times the wieght of an average adult is put on it suddenly . Lets say for argument sakes that the average weight of an adult man is 80kg's , that means the seat belt mount has to withstand at least 1.6 tonnes put on it in less than a second . I don't know about you but I wouldn't like to put that much weight on a single thickness of flat body steel .

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PostPosted: Sat Nov 03, 2007 3:43 pm 
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I'm with Ian, I wouldn't like to have that belt between me and the windscreen in an accident...

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PostPosted: Sat Nov 03, 2007 3:55 pm 
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Kennomini wrote:
me and my regular passengers weigh in between 45-65kg so if the std top mount can't support those forces even if their doubled then there's something wrong with the structure of the car in the first place.


Mate, you and your (skinny) passengers will be weighing very much more than 45-65kg under the massive deceleration that you will experience in a head-on. Its like that old road safety ad for child seats where they demonstrated that even a really strong bloke wouldn't have the strength to hold onto a baby in a head-on. When I had the head-on in my Moke, my hands punched out the windscreen. Believe me, you don't want that split second thought "I hope those dodgy seatbelts hold up".

Tim

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PostPosted: Sun Nov 04, 2007 10:41 am 
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Timbo wrote:
When I had the head-on in my Moke, my hands punched out the windscreen.
Tim


When I had an "incident" that included my original Clubby attempting to mount a Peugeot from the rear, my glasses came off and bounced back to where they were meant to be. Thats how close to the screen my face was. I'd not change seat belt mounts in any way. Without getting them properly engineered. It's not how heavy you or your passengers are that matter, but whether you could live with it if your mod caused a death, or serious injury to a passenger (or heaven forbid even yourself).

Don't want to pick on ya for the sake of it, but life is worth much more.

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PostPosted: Sun Nov 04, 2007 6:38 pm 
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Hmmm looks like I should refit the belts using the std mounts from whats been said :( (something I don't want to do but seems critical). I'll try my best to fit them like WantOne has but I think my Clubman seats may be in the way :? . I'll keep yous updated.

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PostPosted: Sun Nov 04, 2007 6:43 pm 
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Kennomini wrote:
I think my Clubman seats may be in the way :?


Swap the seats, left-to-right. makes it a bitch to get to the release handle, but they won't foul on the seatbelt reel.

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PostPosted: Sun Nov 04, 2007 9:37 pm 
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d1ck0 wrote:
When I had an "incident" that included my original Clubby attempting to mount a Peugeot from the rear, my glasses came off and bounced back to where they were meant to be. Thats how close to the screen my face was.


Ha Ha, (hope its safe to laugh about now). My glasses kept on going, they disappeared off down the road somewhere, with the mokes bonnet. I was pretty near blind for several days in hospital until I got some new ones made.

Tim

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PostPosted: Mon Nov 05, 2007 9:12 am 
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Seat belts can be an odd argument. It is perfectly legal for me to take passengers in the back of my Mini with no seat belts fitted. If I crash, they die. If I fit seat belts to the back without getting them engineered, then my passengers may only get badly injured in an accident but I am liable :lol:

I have relatively new Klippan fixed belts in my car, but they have a habit of slowly losing their tension and you have to tighten them up. Seems to be a design feature as my other Mini with the same belts (which are even newer) do it too? That's the main reason I would like to fit retractable belts. That, and it requires less explaining when you take a passenger.


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PostPosted: Mon Nov 05, 2007 9:34 am 
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Fixed belts are no less safe than retractables in an accident. In fact there is an argument that they are safer because there is no reel for the belt to tighen around (not considering webbing grabbers).

HOWEVER, they need to be adjusted every time they are fitted, because even wearing a different shirt will effect the fit. So the main reason for fitting them is tidyness (no belt to stow). Also less hassle explaining to your passenger how to adjust it.


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PostPosted: Mon Nov 05, 2007 9:37 am 
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I've been thinking that a good compromise would be to buy new fixed belts but get shorter ones that suit the Mini and my slim build - then it looks less messy. Admittedly it will mean I can no longer take bargearse for a drive, but I can deal with that.


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PostPosted: Mon Nov 05, 2007 7:17 pm 
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One of the reasons I've gone for the retractable belts is because to reach the switches you need to have the belt loose :? , I figured in an accident a loose belt = bad pain. It's a 'catch 22' situation, unfortunately I'm coming up against all 22 catches :x :lol: But I have tomorrow off so I'll try and install the belts more "safely/legally".

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PostPosted: Tue Nov 06, 2007 1:09 am 
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Anto wrote:
Seat belts can be an odd argument. It is perfectly legal for me to take passengers in the back of my Mini with no seat belts fitted. If I crash, they die. If I fit seat belts to the back without getting them engineered, then my passengers may only get badly injured in an accident but I am liable :lol:

That, and it requires less explaining when you take a passenger.


Well it could be said that when there are no seat belts fitted, your passengers can make an informed decision upon seeing no belts and refuse to get in (nobody does though(, but by fitting unsafe belts you are creating the appearance of a safe situation and denying them the right of an informed decision. Plus don't forget that belt guidelines also try to prevent badly instaled belts from becoming a death trap preventing passengers from escaping from a crashed and burning vehicle.

Plus there's nothing wrong with having to lean over your female passengers and adjust the belt around them - all without ever appearing sleazy - you are only concerned about their safety after all...


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PostPosted: Tue Nov 06, 2007 4:16 am 
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Mike that's exactly the reason, but very few understand it. It's the same reason for the rules around a lot of modifications. YOU know what's been done and how to use it properly, but the poor sap two owners down the track doesn't know.


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