Peter Empson
PCGB Member
Here's a pic that shows my setup, the seat here is positioned in my normal driving position. In real life the distance seems to be even greater than is shown in the picture.
Modified 944's
- Thread starter rickware
- Start date
Yes, but with most bolt in cages the plate that they bolt to, that is welded to the car can incorporate what you like. The photo of mine is not clear but the plate that is welded in runs all the way round the sides of the suspension mounts, onto the boot floor and up the sides of the car. Therefore offering lots of structural rigidity.
Firstly, sorry Patrick. It must be my fat fingers but I hadn't spotted it. I type Jihn rather than John quite often, but it's easy to spot and since Mr Sims didn't take me up on the suggestion of changing his name I correct it most of the time.
I don't find myself all that low in my 944 with side mounted buckets as low as I can get them (at the back at least). My helmet doesn't touch the sunroof, but it's not that far away either, and I don't consider myself much in any taller than average.
As I think I have said before I imagine that in some crash situations cage setup 1 might better cage setup 2, but that in another crash the opposite might be true.
It does seem like a rear cage (with any protrusions to allow fitting of a front section removed or positioned in a safe location) has few downsides from a safety perspective, albeit in some crashes it might add little. Even though a driver's head does intersect the line between the rear cage top and the front of the bonnet that is still better than the stock situation where the equivalent line runs from the front of the bonnet to the bottom of the hatch, remember.
In terms of a full cage with no helmet the situation is less clear as there is a strong chance of head injury against the tube that runs inside the door top. Of course there is also an upside that there may be less injury due to the structure around the driver being stengthened. I have to say I am somewhat sceptical that decent padding on a bar across the top of the door would leave it dramatically dangerous compared with the top of the door itself, which in a standard 944 I am pretty sure my head would impact given the right sort of crash.
The reasons I say I am unconvinced it is significantly more dangerous is that with the right padding to manage the impact of the head, plus the fact that head and tube are relatively close together thereby limiting the amount of acceleration of the head toward the tube that the presence of the tube might be mitigated. In other words if you have a crash where your head hits the roll cage either your head would have hit the top of the door anyway (which is unforgiving in comparison to a head and also has an edge) or it would hit the cage without a massive amount of force which could be dissipated to a sufficient degree by padding (by padding I don't mean 1/2" of foam pipe lagging).
As an aside are we all aware that the 944 has hooks behind the rear axle that are intended to play a part in frontal impact? The engine moving backward pushes the torque tube and the transaxle backward and it hits the hooks to limit the backward intrusion of the engine into the passenger compartment by passing some of the force behind the occupants. I guess it might work in reverse to some degree with a heavy rear impact also.
I don't find myself all that low in my 944 with side mounted buckets as low as I can get them (at the back at least). My helmet doesn't touch the sunroof, but it's not that far away either, and I don't consider myself much in any taller than average.
As I think I have said before I imagine that in some crash situations cage setup 1 might better cage setup 2, but that in another crash the opposite might be true.
It does seem like a rear cage (with any protrusions to allow fitting of a front section removed or positioned in a safe location) has few downsides from a safety perspective, albeit in some crashes it might add little. Even though a driver's head does intersect the line between the rear cage top and the front of the bonnet that is still better than the stock situation where the equivalent line runs from the front of the bonnet to the bottom of the hatch, remember.
In terms of a full cage with no helmet the situation is less clear as there is a strong chance of head injury against the tube that runs inside the door top. Of course there is also an upside that there may be less injury due to the structure around the driver being stengthened. I have to say I am somewhat sceptical that decent padding on a bar across the top of the door would leave it dramatically dangerous compared with the top of the door itself, which in a standard 944 I am pretty sure my head would impact given the right sort of crash.
The reasons I say I am unconvinced it is significantly more dangerous is that with the right padding to manage the impact of the head, plus the fact that head and tube are relatively close together thereby limiting the amount of acceleration of the head toward the tube that the presence of the tube might be mitigated. In other words if you have a crash where your head hits the roll cage either your head would have hit the top of the door anyway (which is unforgiving in comparison to a head and also has an edge) or it would hit the cage without a massive amount of force which could be dissipated to a sufficient degree by padding (by padding I don't mean 1/2" of foam pipe lagging).
As an aside are we all aware that the 944 has hooks behind the rear axle that are intended to play a part in frontal impact? The engine moving backward pushes the torque tube and the transaxle backward and it hits the hooks to limit the backward intrusion of the engine into the passenger compartment by passing some of the force behind the occupants. I guess it might work in reverse to some degree with a heavy rear impact also.
Padding is needed to meet FIA standard 8857-2001. Type A padding is needed in all areas possible contact between the occupants and vehicle can occur. This would cut down on head injury but I do get a tad concerned when I drive my car on the road. To be honest the other day I did a test (by throwing myself round the car, it wasn't moving at the time) to see if my harness would stop me before my head hit the cage and it only just does. I would think in an accident I would make contact.
If you are going to use the car for competition then you need a cage, if you do lots of tack days then I think it would give you more confidence. But if the car is a road car I wouldn't bother with all the trouble.
If you are going to use the car for competition then you need a cage, if you do lots of tack days then I think it would give you more confidence. But if the car is a road car I wouldn't bother with all the trouble.
edh
New member
Tom - in an accident your neck would stretch - I'm sure you would make contact with the cage.
Fen's point is an interesting one - the closeness of the cage reducing the energy of the collision. I guess a HANS is a natural extension of this discussion - as I understand it that works by stopping the head accelerating away from the torso & your neck breaking
If I ever get there, I'll stick in half cage. It's got to be better roll protection than nothing, (and a good point to attach a harness) - Simon if you're interested, I know of a chap in Derby who builds custom cages - I've seen some he's done in saloons. You can get him via Frank Browns in Allestree.
Fen's point is an interesting one - the closeness of the cage reducing the energy of the collision. I guess a HANS is a natural extension of this discussion - as I understand it that works by stopping the head accelerating away from the torso & your neck breaking
If I ever get there, I'll stick in half cage. It's got to be better roll protection than nothing, (and a good point to attach a harness) - Simon if you're interested, I know of a chap in Derby who builds custom cages - I've seen some he's done in saloons. You can get him via Frank Browns in Allestree.
? Granted my Blue Book is 2004 but I can't find that as a requirement. It could well be that the suspension mounting point is outside of the zone necessary to achieve the specified angle of the back stays but, as far as I can see, location relative to suspension mountings is not prohibited on the grounds of increased rigidity. It may be the case that the addition of supplementary bars, to pick up the suspension mountings, could be outlawed because of the detrimental effect they could have on the principal structural members though.
Any triangulated structure rigidly fixed to a car will improve the rigidity of the car - unless the mountings move how can it do anything else?
Cages are frequently used to improve the structural rigidity of a racing car and thereby increase their potential. Racers would not weld fillets between a cage and the frame of a car, over and above that which was mandatory, for fun as the fillets add weight. They add fillets because it increases the rigidity of the car which makes the suspension more tunable which improves performance.
appletonn
New member
Well a 'simple' bolt in front strut brace adds rigidity to the front supensions towers, so a bolt in cage, however 'simple', must add some rigidity to the body structure, albeit not as much as a welded in cage.
Unless the bolts and the mounting points are made from rubber, of course..... [8|]
944 man
Active member
A further point: do the people arguing with me here really believe that a little (or a lot, it doesnt matter) extra rigidity in the cabin area makes any practical difference? I once drove a 1979 Volvo 344 (it was beautiful, it had travelled under 30,000 miles and it looked like new) round a tight uphill corner spiritedly, and the drivers door and the hatch both opened! That car was the exception to the rule. That car might have benefitted from the increase in torsional rigidity that a bolt in roll cage would have added. Most cars, 924/944/968 types included, wont benefit at all from a six point cage; and they probably wont benefit even where the cage is tied in to the monocoque. The only real benefit would come from extending the tubes to meet the suspension mountings and bracing those points across. Of course, to benefit fully from this the whole structure would need to be welded into the vehicle and not simply bolted...
944 man
Active member
Anyway; if you really want to stiffen a car (where a proper multipoint cage isnt permitted by the rules) you seam weld it. If you dont believe me ring up EMC and tell Kevin that youd like him to fit you a SD bolt in cage, because you need the extra rigidity and youre looking forward to reaping the benefit in handling that it will bring.
That's a little offensive but, none the less, considering "little real knowledge" strut braces work in tension not compression. They are there to stop the suspension towers pulling apart - fact
I fear many of your points are based on speculation where a a good number of the contrary points are based on personal experience.
Just my opinion.
Which rules are these? Any regulations I have read state minimum requirements. I accept there may be issues with classic open top sports cars but that isn't the nature of this thread.
A triangulated cage securely bolted into a car will increase its structural rigidity. It may not increase it to the point that you can necessarily feel it but any additional bracing must be of some benefit.
Seam welding is a tried and tested method of increasing rigidity as is, where appropriate, foam filling cavities. Neither are necessarily routes that those of us who indulge in an occasional track day are likely to consider where as a Roll hoop or cage perhaps are.
To be fair Simon I don't see you speaking with any more authority or demonstrable knowledge than several other posters (and I do not include myself in that as a rolll cage is one thing I have never had in any car) and I'm afraid "ask Kevin at EMC" doesn't cut it for me either as I believe that for everyone who has a strong opinion in his favour you'll find someone else who dousn't rate EMC. Apocryphally they couldn't build a reliable turbo engine if their life depended on it for example. I point out here that I have never had any dealings with them, but based on what I have read over years around the community they are on my mental "more sizzle than sausage" list to use a trurn of phrase I believe you will fully understand.
I have to say that you are losing credibility in my eyes (and you have a lot in most areas) by trying to suggest a bolt in cage willl not increase rigidity. You also argue against yourself with the Volvo 344 ditty as you state it would benefit. Now there is no way a Volvo can benefit and a 944 not, the difference can only be in degree. As I have said before I have no direct experience of a cage in a 944 (nor anything else), but it is plain that some stiffness will be added by any form of bracing and a bolt in rear cage properly attached at floor and seat belt B-pillar top mounts, especially with harness and/or diagonal bars, will add rigidity. Whether or not it is noticeable is a different issue, and I suspect it would be hard to feel a difference based on my experience with a strut tower brace in the 944, but it might.
I personally wouldn't fit a rear cage for increased rigidity as I tend to agree the difference might be small (possibly not so much in a cab as they are a bit wibbly) but for added safety (I'd rather in a becoming upside down situation my head intersect a line between the top of a cage and the bonnet if it comes to that than the alternative of intersecting a line from the bottom of the hatch to the front of the bonnet), and although we may disagree on this point I'd also want to use it to attach my harness shoulder straps to.
On the other hand I agree with you and disagree with John in terms of suspension pickup. There are lots of more standard classes that exclude triangulation of cages to the suspension, particularly the front where the cage would otherwise go nowhere near the suspension mounts. This I have always assumed is to keep perparation costs down by preventing some people from using the cage required to meet safety regulations from using it to gain significant extra rigidity. Which of course underlines that extra rigidity in significant amount is there to be gained from so doing.
Bottom line though is that anything solid attached rigidly where there is currently fresh air will add some stiffness to a structure.
I have to say that you are losing credibility in my eyes (and you have a lot in most areas) by trying to suggest a bolt in cage willl not increase rigidity. You also argue against yourself with the Volvo 344 ditty as you state it would benefit. Now there is no way a Volvo can benefit and a 944 not, the difference can only be in degree. As I have said before I have no direct experience of a cage in a 944 (nor anything else), but it is plain that some stiffness will be added by any form of bracing and a bolt in rear cage properly attached at floor and seat belt B-pillar top mounts, especially with harness and/or diagonal bars, will add rigidity. Whether or not it is noticeable is a different issue, and I suspect it would be hard to feel a difference based on my experience with a strut tower brace in the 944, but it might.
I personally wouldn't fit a rear cage for increased rigidity as I tend to agree the difference might be small (possibly not so much in a cab as they are a bit wibbly) but for added safety (I'd rather in a becoming upside down situation my head intersect a line between the top of a cage and the bonnet if it comes to that than the alternative of intersecting a line from the bottom of the hatch to the front of the bonnet), and although we may disagree on this point I'd also want to use it to attach my harness shoulder straps to.
On the other hand I agree with you and disagree with John in terms of suspension pickup. There are lots of more standard classes that exclude triangulation of cages to the suspension, particularly the front where the cage would otherwise go nowhere near the suspension mounts. This I have always assumed is to keep perparation costs down by preventing some people from using the cage required to meet safety regulations from using it to gain significant extra rigidity. Which of course underlines that extra rigidity in significant amount is there to be gained from so doing.
Bottom line though is that anything solid attached rigidly where there is currently fresh air will add some stiffness to a structure.
944 man
Active member
Demonstrable knowledge: I have a family history of race car prep. My grandfather built and prepared racing Aston Martins and my uncle is a well known racer (who has built and prepped everything from the original Tuscan challenge cars to spaceframe GTs, right the way back to Mini Se7ens). I have built cars myself and I have spent the last twenty years looking, trying, reading and learning (and failing)...
Rigidity: what is it exactly and more importantly, how does it benefit you? The Volvo was made of jelly and it twisted under load; enough to allow the doors to open. Theres no denying that that car would have benefited from anything that stiffened it; I am saying that adding a little (and it is a little with a bolt in cage, unless the welded in mounting provision is so substantial that youve ended up plating the chassis) rigidity to the cabin of a 4cyl Porsche doesnt give you any real benefit. In order to benefit from this stiffness, you have to tie the new stiffer structure/area into the suspension mounting points (and as I mentioned earlier: you then need to brace them across -top and bottom ideally- and tirangulate the front cross-brace to the firewall).
Im sure that this will be an even more contentious point, but I will make it anyway. Where you make the cabin area stronger though fitting a bolt in roll cage, and then stiffen it further through tying-in, you eventually end up compromising the rest of the bodyshell. You havent added any worthwhile strength, because the suspension mountings are still all unreinforced, but you have reduced the area of the structure which is able to absorb the still present flex/movement...
EMC: I quite like Kevin, but I have mentioned them principally because I believe that their body preparation to be sound and because they seem to be held in high regard, also: his blunt style amuses me... Of course, I am also confident that he will corroborate my opinion. With regards to engine building, I know virtually nothing, so I cant comment.
Its a good job that I didnt mention anything about not running List 1B or slick tyres in an unprepared chassis..... [
]
Rigidity: what is it exactly and more importantly, how does it benefit you? The Volvo was made of jelly and it twisted under load; enough to allow the doors to open. Theres no denying that that car would have benefited from anything that stiffened it; I am saying that adding a little (and it is a little with a bolt in cage, unless the welded in mounting provision is so substantial that youve ended up plating the chassis) rigidity to the cabin of a 4cyl Porsche doesnt give you any real benefit. In order to benefit from this stiffness, you have to tie the new stiffer structure/area into the suspension mounting points (and as I mentioned earlier: you then need to brace them across -top and bottom ideally- and tirangulate the front cross-brace to the firewall).
Im sure that this will be an even more contentious point, but I will make it anyway. Where you make the cabin area stronger though fitting a bolt in roll cage, and then stiffen it further through tying-in, you eventually end up compromising the rest of the bodyshell. You havent added any worthwhile strength, because the suspension mountings are still all unreinforced, but you have reduced the area of the structure which is able to absorb the still present flex/movement...
EMC: I quite like Kevin, but I have mentioned them principally because I believe that their body preparation to be sound and because they seem to be held in high regard, also: his blunt style amuses me... Of course, I am also confident that he will corroborate my opinion. With regards to engine building, I know virtually nothing, so I cant comment.
Its a good job that I didnt mention anything about not running List 1B or slick tyres in an unprepared chassis..... [
]
Absolutely and I agree with you 100%. Without restrictions as such those with the money would build a space frame. There are restrictionns subject to class and Blue Book Drawing Nº Q37 demonstrates the mandatory frame members and maximum additional bars allowed. These do not come forward of the fire wall as, were they to do so, one assumes the transfered force of a crash could bend the main safety cell. I haven't found (in the Blue Book) a specific instruction which prohibits picking up the rear suspension points as, my further asuption is, the rear bars will pick up on the suspension, or not, subject to if the suspension is at a point relative to the correct angle for the rear bars. If this was a design consideration one assumes there would perhaps be a stipulation that the frame must not be mounted within a certain distance of the suspension pick up points.
My comment was on the suggestion that bolt in cages are deliberately designed not to increase structural rigidity.
The MSA design is to provide the maximum economic level of protection for the driver. Additional shell rigidity is not part of the design criteria but an inevitable byproduct. The design is not such to reduce the effect of this byproduct; it ignors it.
You best take that up with the MSA then as they are obviously deliberately putting drivers at risk.[
].....Its a good job that I didnt mention anything about not running List 1B or slick tyres in an unprepared chassis..... [
Why's that? We could then have something to agree on. [
]
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