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I did read the link Rich.
The way i see it, is having a strut there or not, if the bar breaks, wouldn't make any difference. The door would come crashing down regardless. Besides, if the bar is gonna break, then it's gonna break when the door's shut (most torque stress applied to the bar at that point).
Rissy
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i've had torsion bars break on me when the force has been taken off, so if its going to snap, it could be at any point, Depends on fatigue / cracks or flaws when it was manufactured.
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Quote:The way i see it, is having a strut there or not, if the bar breaks, wouldn't make any difference. The door would come crashing down regardless. Besides, if the bar is gonna break, then it's gonna break when the door's shut (most torque stress applied to the bar at that point).
Well you did ask....and that was the reason
One day I'll get chance to show you the difference between a door with a strut, and a door with nothing....Dermot already knows :lol:
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and what happened to the door when it went?
Rissy
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May 1981 vin#1458 "LEX"
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Chassis: #1073
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2005 BMW M3 in Velvet Blue
2010 Honda Civic Type R in Sapphire Blue (1 of 115 made)
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RichH Wrote:Quote:The way i see it, is having a strut there or not, if the bar breaks, wouldn't make any difference. The door would come crashing down regardless. Besides, if the bar is gonna break, then it's gonna break when the door's shut (most torque stress applied to the bar at that point).
Well you did ask....and that was the reason
One day I'll get chance to show you the difference between a door with a strut, and a door with nothing....Dermot already knows :lol:
I'd just like to spend more time with my car, never mind get more time spent with you guys. It's frustrating having my car 325 miles away from me all the time.
Rissy
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i dunno if the question was to me, but it wasnt a door, it was the rear suspension on an aircooled. I jacked the car up and it went BANG! i pooped a little, went to the toilet and wiped up 
Chris, are there no garages you can rent locally? I rent a HUUUUUUUUUge unit for my cars and bus, about 13 miles away.
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Quote: It's frustrating having my car 325 miles away from me all the time.
Now that would really cheese me off...
Quote:I rent a HUUUUUUUUUge unit for my cars and bus, about 13 miles away.
Generally around here cheap garages are in dodgy areas with poor security and very small. The cheapest I can find for anything substantial (room for work benches etc) is getting on for £10K a year by the time you've paid Council Rates and VAT :evil:
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it's the same story as everyone else. I looked into it, but all are council garages which i wouldn't trust the car being left in. No no. i want my OWN garage with the car right there so I can tinker with it and drive it more often, no matter what day, without having to make a special journey to go collect it. It also means I can take more apart and not have to be in a rush to reassemble it before having to leave it again.
Rissy
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have you tried local farms, cash in hand stylee?
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Blimey! Just come back home and found quite a few replies to the original post.......talk about a hot topic!
Mind you, that's the great thing about having a forum. I can't imagine how hard it was to do anything on our cars before the internet and forums were around. Talk about a nightmare...
Anyway, my understanding was that with the struts off the door would open a couple of inches. As far as I understand it the force of the torsion bar COUNTERS the weight of the door, but not enough to lift it all the way. It's like having a see-saw with a nearly equal weight at an equal distance from the pivot as yourself. This makes it far easier to move yourself up and down. In the case of the door it makes it far easier for the strut to move the door.
In my case the bar doesn't move the door that couple of inches away from the bottom. I checked it with the seals, strut and door strikers removed, so they didn't have an effect. As for adjusting the torsion right the way up so it can open the door on itself, well from what I've read thie can cause loads of damage as the torsion bar twists the frame and T section. Sounds like a bad idea to me. 
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The torsion bar is a spring. It’s like a suspension spring except it is straight (yes, really, a suspension spring twists along its length). The more you want to twist it, the more torque is required. It is not a counterbalance because that would give constant force regardless of position.
The gas strut is also a spring, the more you compress it, the more force is required. However it also has a damping function 1) from the gas passing through the piston and 2) because there’s a teaspoonful of oil in there as well which causes the last half inch to slow down. Number 2 was not present in original struts and is not present in all struts today. The compressive force of a fully compressed strut should be 1200N or about 1/8th of a tonne if anyone’s counting.
However, when fully compressed, the strut is acting directly through the centre of the hinge – in other words it has absolutely no effect whatsoever. If your door is to pop on its own, the torsion bar must lift it the first couple of degrees. HOWEVER, don’t forget that from the outside you’re helping the door by pulling on the handle and from the inside, a quick elbow is often all that’s required (we do it on any other car so you probably don’t even notice you’re doing it). When fitting door launchers, you soon notice quite how much user-intervention is required normally!
So the door has just popped open; the more the door opens, the less assistance the torsion bar provides, but the more the geometry of the gas strut allows it to assist the door. Its applied force is also dropping along its stroke, but the improving geometry more than compensates.
I could do a couple of moment diagrams to help explain but I can’t be bothered. Suffice to say that when fully closed, the gas strut does not help lift the door, hence the torsion bar does the work. This has led to the theory that the door should hang open slightly without a strut – but it’s really only by half an inch to an inch or so in my experience.
On the flip side, the door is an absolute monster to lift without a torsion bar even with a new strut, but once up there, it’s not that hard to hold it there.
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Ah, I see what you mean now . Yes, I can see that when the door is closed the force of the strut has nowhere to go as its laying flat and it needs the force of the torsion bar to move the door into a position whe it can start to exert that force and lift the door. Makes sense now.
So, are we saying that in fact I need to check things again with regards the torsion bar, and that it may be fine, or that it indeed needs adjusting?
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The bar and the strut are designed and sized to work in concert with each other. As Martin says, when I had no bar and a new D-sized strut, the strut could not open a closed door, but it would keep an open door open.
No doubt a much larger strut could actually open the door for you but it would put a lot of stress on the mounting points (the Mercedes SLS just uses two struts, no bar, for instance)
Similarly if you support your open door on your shoulder and pop the strut off (with a bar), you will certainly feel the weight of the door. If you then hold on to the door (with the bar attached) and guide it towards the closed position, it will find equilibrium 1-2 inches above the door sill (or 0.5-1 inches). I don't think that anyone measures it. If it is anywhere in that range, I think most people err towards not touching the bar.
While no tech expert like Rich or Martin, the failed bars that I have heard of have always broken in the closed position, which makes sense as that is the highest stress condition. I assume it is possible that it would break while closing the door (and increasing stress) and you are inside the car, but very unlikely that it would happen while opening, and therefore relieveing stress. Anecdotal stories tell of hearing a loud crack while driving, possibly with some additional flexing of the tub being the final straw.
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Rich,
Was that post of mine really 12 years ago? ...does make me feel very old!
http://www.projectvixen.com/dmcuk-archive/msg15299.html
Currently in touch with Brian Rix again, as we are writing up door bit.
Chris Parnham
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flux3d Wrote:So, are we saying that in fact I need to check things again with regards the torsion bar, and that it may be fine, or that it indeed needs adjusting?
First things first, fit a new strut and see how the door behaves. If it isn't good enough, tweak the bar up a spline or two. Test the bahavour with each added spline, on a hot day you can expect a bit of a bounce at the top but not too much
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