Harness Question(not necessarily Porsche)
12-31-2005, 01:01 PM
#31
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Cristal;
Yes, tie the tails together under the angled stay brace. In case of an offset impact (angle), the belts can slide down the bar if the seat moves laterally. Tieing the belts will help keep them from sliding.
owain;
The seat back can be in with the bar there, but it must remain up. Otherwise, it will lay against the bar, which is not a problem either... really.
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Another point about the stock seat with harness thing. The body comes out from under the belts because of chest deformation, or Shape Change as it is called by Dr. Melvin. The following is my theory, based on what I have read on this. I have not seen anyone explain the physical Shape Changes in this detail, it is just my surmize.
This Shape Change probably takes the form of the shouders being pulled backward relative to the breast bone (This is the force that splits the sternum and the reason for the existance of sternum straps). This angles the shoulders backward, allowing a non-perpendicular surface that the belt(s) can slip off of more easily. This is exacerbated in an offset hit where the off-side shoulder will slip out from under the off-side strap even more easily.
Dr. Melvin has documented reductions of as much as 50% in chest loads when a cradle type dual sub system is employed. It is my surmize that utilizing the the cradle type sub setup will also therefore decrease the Shape Change of the chest and shoulders commensurate with that chest load reduction. I further theorize that this reduction in shape change will help the torso remain under the belts in a stock seat application.
Quite interestingly, Dr. Melvin also has seen a reduction in neck tension of as much as 15% with a proper cradle sub setup. This is fascinating stuff!
Yes, tie the tails together under the angled stay brace. In case of an offset impact (angle), the belts can slide down the bar if the seat moves laterally. Tieing the belts will help keep them from sliding.
owain;
The seat back can be in with the bar there, but it must remain up. Otherwise, it will lay against the bar, which is not a problem either... really.
---------------------------------------------------------------------------------------
Another point about the stock seat with harness thing. The body comes out from under the belts because of chest deformation, or Shape Change as it is called by Dr. Melvin. The following is my theory, based on what I have read on this. I have not seen anyone explain the physical Shape Changes in this detail, it is just my surmize.
This Shape Change probably takes the form of the shouders being pulled backward relative to the breast bone (This is the force that splits the sternum and the reason for the existance of sternum straps). This angles the shoulders backward, allowing a non-perpendicular surface that the belt(s) can slip off of more easily. This is exacerbated in an offset hit where the off-side shoulder will slip out from under the off-side strap even more easily.
Dr. Melvin has documented reductions of as much as 50% in chest loads when a cradle type dual sub system is employed. It is my surmize that utilizing the the cradle type sub setup will also therefore decrease the Shape Change of the chest and shoulders commensurate with that chest load reduction. I further theorize that this reduction in shape change will help the torso remain under the belts in a stock seat application.
Quite interestingly, Dr. Melvin also has seen a reduction in neck tension of as much as 15% with a proper cradle sub setup. This is fascinating stuff!
12-31-2005, 01:07 PM
#32
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Mark;
I knew where you were going with this after your 1st post. I was of the same mind on that point myself. I felt that belts should pull straight off there moorings. However, Schroth themselves state that if the shoulder belt path from mount to seat exceeds about 16", that they should be crossed. This enters the same kind of shear loads into the material that you are thinking of, and yet they recommend it. That tells me it may not be of as much concern that you or I are/were thinking.
It is an interesting point, and one that needs to be clarified, methinks. I think I will write them and see if I can get a clarification.
I knew where you were going with this after your 1st post. I was of the same mind on that point myself. I felt that belts should pull straight off there moorings. However, Schroth themselves state that if the shoulder belt path from mount to seat exceeds about 16", that they should be crossed. This enters the same kind of shear loads into the material that you are thinking of, and yet they recommend it. That tells me it may not be of as much concern that you or I are/were thinking.
It is an interesting point, and one that needs to be clarified, methinks. I think I will write them and see if I can get a clarification.
12-31-2005, 01:52 PM
#33
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Originally Posted by RedlineMan
Mark;
I knew where you were going with this after your 1st post. I was of the same mind on that point myself. I felt that belts should pull straight off there moorings. However, Schroth themselves state that if the shoulder belt path from mount to seat exceeds about 16", that they should be crossed. This enters the same kind of shear loads into the material that you are thinking of, and yet they recommend it. That tells me it may not be of as much concern that you or I are/were thinking.
It is an interesting point, and one that needs to be clarified, methinks. I think I will write them and see if I can get a clarification.
I knew where you were going with this after your 1st post. I was of the same mind on that point myself. I felt that belts should pull straight off there moorings. However, Schroth themselves state that if the shoulder belt path from mount to seat exceeds about 16", that they should be crossed. This enters the same kind of shear loads into the material that you are thinking of, and yet they recommend it. That tells me it may not be of as much concern that you or I are/were thinking.
It is an interesting point, and one that needs to be clarified, methinks. I think I will write them and see if I can get a clarification.
Keep us posted.
12-31-2005, 03:57 PM
#34
Race Car
Kool -
here's my suggestion regarding the harnesses. use a 5 or 6 point snap-in with harness eyelets bolted to the floorboard and central tunnel for the sub and lap belts. then you can snap the harnesses in or out in less than 5 minutes and convert the car back to street driving. the only problem is you'd have to use a rollbar or at least a harness mount bar for the two shoulder harness straps, but it's a very simple and effective way of having great harnesses. This is the way I have my new M3 setup. I do have one piece track seats with shoulder belt holes, but it's not too uncomfortable to drive daily.
here's my suggestion regarding the harnesses. use a 5 or 6 point snap-in with harness eyelets bolted to the floorboard and central tunnel for the sub and lap belts. then you can snap the harnesses in or out in less than 5 minutes and convert the car back to street driving. the only problem is you'd have to use a rollbar or at least a harness mount bar for the two shoulder harness straps, but it's a very simple and effective way of having great harnesses. This is the way I have my new M3 setup. I do have one piece track seats with shoulder belt holes, but it's not too uncomfortable to drive daily.
12-31-2005, 05:14 PM
#35
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Hey Joseph
That is kind what I was leaning towards. I have been wading through the "RSX vs. horse drawn carriage in a straight line" posts on other RSX forums to see what other people use and I have found a Autopower cage for $325. So that is a possibility.
I wanted to thank everybody for all the good info. I know it isn't Porsche specific but the knowledge base that is here doesn't exist anywhere else that I can find.
That is kind what I was leaning towards. I have been wading through the "RSX vs. horse drawn carriage in a straight line" posts on other RSX forums to see what other people use and I have found a Autopower cage for $325. So that is a possibility.
I wanted to thank everybody for all the good info. I know it isn't Porsche specific but the knowledge base that is here doesn't exist anywhere else that I can find.
12-31-2005, 06:47 PM
#36
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Originally Posted by joseph mitro
Kool -
here's my suggestion regarding the harnesses. use a 5 or 6 point snap-in with harness eyelets bolted to the floorboard and central tunnel for the sub and lap belts. then you can snap the harnesses in or out in less than 5 minutes and convert the car back to street driving. the only problem is you'd have to use a rollbar or at least a harness mount bar for the two shoulder harness straps, but it's a very simple and effective way of having great harnesses. This is the way I have my new M3 setup. I do have one piece track seats with shoulder belt holes, but it's not too uncomfortable to drive daily.
here's my suggestion regarding the harnesses. use a 5 or 6 point snap-in with harness eyelets bolted to the floorboard and central tunnel for the sub and lap belts. then you can snap the harnesses in or out in less than 5 minutes and convert the car back to street driving. the only problem is you'd have to use a rollbar or at least a harness mount bar for the two shoulder harness straps, but it's a very simple and effective way of having great harnesses. This is the way I have my new M3 setup. I do have one piece track seats with shoulder belt holes, but it's not too uncomfortable to drive daily.
...NOT.
Relate the mounting of eye bolts into thin sheetmetal in tension to the fact that in an "average crash" (which would register 30-40g), the lap belts will see somewhere in the neighborhood of 2800lbs load! In that G range, a human body of 200lbs "weighs" the equivalent of 6,000-12,000lbs! Those G-loads are not at all difficult to generate, even in a street crash.A sheetmetal floor simply will not withstand that sort of load... no matter HOW big the washers are you are thinking about using. Think of it this way. What would happen if you put your floor jack under the pan somewhere and raised the car? It would crush, of course. That is only a static load, where the forces on belts and cages - those of a crash - are dynamic, even exponential. Also note that OE systems NEVER mount to floor pans. They mount to reinforced side sills in shear.
Floor mounting seems easy and convenient, but being injured... or dead, is not quite so.
12-31-2005, 07:19 PM
#37
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Kool: back to what (I think) was part of your original question...easy in/easy out & swapping between 2 cars. As you all can see, I LOVE my new setup, and it was pretty easy to install, but it's not going to be coming in & out, which was kinda my original intention also. I definitely wouldn't want to be trying to deal w/it at the track, for example. As for the 5- or 6-point question, I went w/6 just so I wouldn't have to drill in my floor, and I'm glad to read it's probably safer as well! 
12-31-2005, 08:36 PM
#38
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Redlineman,
so what would you suggest as an alternative mounting point for harnesses? I know this is your soapbox, but please don't say the seat mounts, those are not designed for that use, despite what the manufacturers say. Unless the mounts are reinforced. Mounting would be more effective if the harness mounts were separated from the seat mounts, because the forces on the mounts and the forces on the seats would be divided. the only alternative in my view would be to weld in brackets to the sheetmetal, or do you have a better alternative?
also, don't forget that the forces are divided by the number of mounting points. ie, 12000 lbs is not all directed through one eyebolt, but five or six different mounting locations. and if there is a sub-belt mounted, where else but the floorboard would the harness be mounted to? you could weld in a mounting plate which essentially serves the same purpose as a backing plate, except you could use a larger size plate to distribute the force more effectively.
So tell me what you think I should do to mount harnesses in my M3 that serves as primarily track car but is also street registered?
EDIT - sorry, one more thing.....the outer harness bolt is bolted to the same location that holds the stock seatbelt mount. the inner central tunnel bolt goes through two layers of sheetmetal (as opposed to one on the 944), and the floorboard has one layer of sheetmetal. So on my 5 point harness setup, only two of the mounting locations passes through sheetmetal, and only one of those (the floorboard) is a single layer of sheetmetal
so what would you suggest as an alternative mounting point for harnesses? I know this is your soapbox, but please don't say the seat mounts, those are not designed for that use, despite what the manufacturers say. Unless the mounts are reinforced. Mounting would be more effective if the harness mounts were separated from the seat mounts, because the forces on the mounts and the forces on the seats would be divided. the only alternative in my view would be to weld in brackets to the sheetmetal, or do you have a better alternative?
also, don't forget that the forces are divided by the number of mounting points. ie, 12000 lbs is not all directed through one eyebolt, but five or six different mounting locations. and if there is a sub-belt mounted, where else but the floorboard would the harness be mounted to? you could weld in a mounting plate which essentially serves the same purpose as a backing plate, except you could use a larger size plate to distribute the force more effectively.
So tell me what you think I should do to mount harnesses in my M3 that serves as primarily track car but is also street registered?
EDIT - sorry, one more thing.....the outer harness bolt is bolted to the same location that holds the stock seatbelt mount. the inner central tunnel bolt goes through two layers of sheetmetal (as opposed to one on the 944), and the floorboard has one layer of sheetmetal. So on my 5 point harness setup, only two of the mounting locations passes through sheetmetal, and only one of those (the floorboard) is a single layer of sheetmetal
12-31-2005, 10:51 PM
#39
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I am reluctant to do anything that might kill me. 
Christal
Is your car dual use? Or only for the track? I just noticed that your other car is an acura as well. It is hard to go wrong with an Acura/Honda product. If you do drive your car on the street what blets do you use? I would like to be able to keep the functionality and ease of use of the factory 3 point for the street. If the lap belt is hard to get out then tucking it away wouldn't bother me. But I wouldn't want to have the shoulder straps flapping around while I was using the stock belt. That was my thinking behind being able to remove them. But if that is not feasable then I will have to think of something else. Or delay the belt upgrade until the car becomes more for track then street.
Christal
Is your car dual use? Or only for the track? I just noticed that your other car is an acura as well. It is hard to go wrong with an Acura/Honda product. If you do drive your car on the street what blets do you use? I would like to be able to keep the functionality and ease of use of the factory 3 point for the street. If the lap belt is hard to get out then tucking it away wouldn't bother me. But I wouldn't want to have the shoulder straps flapping around while I was using the stock belt. That was my thinking behind being able to remove them. But if that is not feasable then I will have to think of something else. Or delay the belt upgrade until the car becomes more for track then street.
12-31-2005, 11:09 PM
#40
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I'm not convinced there is anything dangerous about the way I suggested installing a harness. In fact, if I am understanding correctly, Christal's 6pt setup has both lap belts and sub belts mounted at the same mounting point? Correct me if I am wrong, but if this is the case I respectfully submit that having SEPARATE mounting points for each of the 6 harness mounts is safer than mounting 2 belts to one bolt. The load should be divided by 6 mounting points, not four.
Additionally, the force vectors created in a crash are not perpendicular to the mount, but vary in three dimensions significantly. I am by no means an engineer, but I would like to see some crash data to support the belief that using backing plates is considered dangerous.
Happy new year
Additionally, the force vectors created in a crash are not perpendicular to the mount, but vary in three dimensions significantly. I am by no means an engineer, but I would like to see some crash data to support the belief that using backing plates is considered dangerous.
Happy new year
12-31-2005, 11:16 PM
#41
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I agree with you.
The thing is that none of us know what the forces actually are. It isn't like all 6 points equally share the load. I would think that the majority of the load is taken by the shoulder belt followed by the lap belt and then the sub belt. I would also submit that if there an impact of 40g does not directly translate into the numbers posted above. Not that RedlineMan's point is not valid. I just don't think the numbers are realistic.
I hope all of you have a great new year. I am going out.
The thing is that none of us know what the forces actually are. It isn't like all 6 points equally share the load. I would think that the majority of the load is taken by the shoulder belt followed by the lap belt and then the sub belt. I would also submit that if there an impact of 40g does not directly translate into the numbers posted above. Not that RedlineMan's point is not valid. I just don't think the numbers are realistic.
I hope all of you have a great new year. I am going out.
01-01-2006, 02:55 AM
#42
While we are havng fun with all this.......John, Mark or anyone else, do you have an educated opinion on mounting the belts 3, 5, or 6 pt. to the seat itself!?
In my car the harnesses are mounted to the tub on both sides of the seat.
Feels kinda good to know that if we go sailing I am bolted to the car not the seat with those little 6mm mounting bolts!
In my car the harnesses are mounted to the tub on both sides of the seat.
Feels kinda good to know that if we go sailing I am bolted to the car not the seat with those little 6mm mounting bolts!
01-01-2006, 10:07 AM
#43
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Most new cars have the Pretensioner bolted to the seat. I build seats for the X5 and Z4 and both have the pretensioner bolted to the seat adjuster.
The pretensioner is the buckle only on most cars now days it has a mechanism in it the tensions the belt in the event of an accident.
That is for one point of the three for the belt. The other two points bolt to the B pillar. In the case of the Z4 the retractor(part that holds the belt) is bolted to the bulkhead behind the seat as there is no B pillar.
The bolts used to hold the seat in are not near as large as the I bolts I have seen that hold in a racing harness.
The pretensioner is the buckle only on most cars now days it has a mechanism in it the tensions the belt in the event of an accident.
That is for one point of the three for the belt. The other two points bolt to the B pillar. In the case of the Z4 the retractor(part that holds the belt) is bolted to the bulkhead behind the seat as there is no B pillar.
The bolts used to hold the seat in are not near as large as the I bolts I have seen that hold in a racing harness.
01-01-2006, 03:15 PM
#44
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Joe;
I don't think you really meant anything by it, but I'm not sure I particularly care for the "soap box" characterization. If you mean do I care that people get good information, and a resulting setup that is as close to optimal as can be attained, then yes, I am preaching... long & loud. I know there are a few folks that think I have become a bit of a blow bag on some of this stuff. I don't really care. If they choose to place lesser importance on safety, it is their neck. I want people to have as much info and understanding as they can. I LIKE my track friends just as they are; healthy, happy, and full of life.
I am trying to be clear about what is optimal, what is not, and what is BAD. This is not personal, and I may be reading your note wrong. If I read what you wrote correctly, you mention drilling a hole in the floor pan and mounting an eye bolt in it, as in the pic below.
If I read your note correctly, and this is what you suggest, then that is what I disagree with. It is not a proper mount for a lap belt. In fact, it is dangerous! I have seen these mounts very nearly tear through a floor on a car that never hit anything. Simple cornering load over time did the dirty work.
I have never seen a manufacturer belt mount that was not in shear, meaning that the belt did not pull off the mount point fairly close to parallel to the mounting surface, as below. Materials in shear have a far higher yield strength than in any other direction, as I assume a lot of people realize. And yet, I see a lot of poor choices still being made in this regard.
You can construct floor mounts that are safe, but they must attach to something that will take the bending load without yielding at all, and transfer it into an adjacent perpendicular panel, like a rocker sill or tunnel. This means making a beam or tube that runs under/over the floor and ties into the rocker sill and tunnel, as in this angle iron mounting system I frequently construct. Both the rear lateral and side longitudinal beams are made from .125x2 angle iron.
The only area that usually provides a prooper point in a sedan is the beam that makes up the front seat mount point in most cars (the front beam in this photo). Unfortunately, that is at the front of the seat, not the back where the lap belt needs to be. No matter how big the backing plates, if a belt mount relies on the horizontal portion of the floorpan at all, it is DANGEROUS. You can see the inner belt mount bolt just behind the cross beam I built. I built the outer belt mount into the iron portion extending back along the rocker sill, as the OE point was too far back.
As another for-instance of a shear mount, this is a dual use setup I built in a 996. Everything in shear, right on the seat slider, and both OE and race belts employable as desired.
You can take these basic principles and judge whether your mounts are proper. You should try and adhere as closely as possible to these basic tenants.
If this is what you had been saying, then I read you wrong, and I am sorry. If this is not the model anyone was working from...
I don't think you really meant anything by it, but I'm not sure I particularly care for the "soap box" characterization. If you mean do I care that people get good information, and a resulting setup that is as close to optimal as can be attained, then yes, I am preaching... long & loud. I know there are a few folks that think I have become a bit of a blow bag on some of this stuff. I don't really care. If they choose to place lesser importance on safety, it is their neck. I want people to have as much info and understanding as they can. I LIKE my track friends just as they are; healthy, happy, and full of life.
I am trying to be clear about what is optimal, what is not, and what is BAD. This is not personal, and I may be reading your note wrong. If I read what you wrote correctly, you mention drilling a hole in the floor pan and mounting an eye bolt in it, as in the pic below.
If I read your note correctly, and this is what you suggest, then that is what I disagree with. It is not a proper mount for a lap belt. In fact, it is dangerous! I have seen these mounts very nearly tear through a floor on a car that never hit anything. Simple cornering load over time did the dirty work.
I have never seen a manufacturer belt mount that was not in shear, meaning that the belt did not pull off the mount point fairly close to parallel to the mounting surface, as below. Materials in shear have a far higher yield strength than in any other direction, as I assume a lot of people realize. And yet, I see a lot of poor choices still being made in this regard.
You can construct floor mounts that are safe, but they must attach to something that will take the bending load without yielding at all, and transfer it into an adjacent perpendicular panel, like a rocker sill or tunnel. This means making a beam or tube that runs under/over the floor and ties into the rocker sill and tunnel, as in this angle iron mounting system I frequently construct. Both the rear lateral and side longitudinal beams are made from .125x2 angle iron.
The only area that usually provides a prooper point in a sedan is the beam that makes up the front seat mount point in most cars (the front beam in this photo). Unfortunately, that is at the front of the seat, not the back where the lap belt needs to be. No matter how big the backing plates, if a belt mount relies on the horizontal portion of the floorpan at all, it is DANGEROUS. You can see the inner belt mount bolt just behind the cross beam I built. I built the outer belt mount into the iron portion extending back along the rocker sill, as the OE point was too far back.
As another for-instance of a shear mount, this is a dual use setup I built in a 996. Everything in shear, right on the seat slider, and both OE and race belts employable as desired.
You can take these basic principles and judge whether your mounts are proper. You should try and adhere as closely as possible to these basic tenants.
If this is what you had been saying, then I read you wrong, and I am sorry. If this is not the model anyone was working from...
01-01-2006, 04:24 PM
#45
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Does the 996 set up integrate with the stock adjuster?
The post above just answered almost all my questions. In the 996 belt application would it be unsafe to use I bolts and the quickrelease latch as long as the belt is oriented in such a way that it is loaded in shear rather then a direct pull type of load?
The post above just answered almost all my questions. In the 996 belt application would it be unsafe to use I bolts and the quickrelease latch as long as the belt is oriented in such a way that it is loaded in shear rather then a direct pull type of load?