Eye bolt through the floor with large flat washers on both sides ok?

Yes, make it in line with your spine.

Ok, Thanks. Mine is in the middle of the seat and about 4" in from the seat lip.

It has to be behind the centerline of your body as you sit in the car.

Raul

and needs to be 1/2"

The further rearward the better. The point of having it is to keep the load on your bones...if you slide down, the load from the lap belt goes to your guts....not good.

The further back the attachment point is, the more forward resistance it provides.

Having a belt straight up for example will rotate in the crash, and let you slip under the lap belts.

The rearmost mounting location also puts the load of the bolt in shear instead of tension. Less likely to rip the washer through the floor pan.

Well Consider with an upright seating position application:

1. On the average person, standing, where is their COG? Just above or in the area of the belly button.
2. In a frontal impact, with a persons legs extended forward and seated, the COG moves higher.
3. The lap belt mainly restrains the pelvic bone, an area able to resist large forces, and its way below the belly button.
3. If a person was say standing upright, and was contacted by a moving robust horizontal object, below their COG, they would always fall over the top, they would never skoot/submarine underneath.
4. The shoulder belts restrains a large chest mass, by transferring impact load to the rollbar, or rear attaching point, AND on the other end to the lap belt. The "and" is the key point here.
5. When the lap belt resists the upward pull of the shoulder harness restraining the chest/head/helmet mass, the lap belt is pulled upwards into the soft stomach area with venerable organs, that do not tolerate large forces well.
6. Having a submarine belt used in a curve, means when the shoulder harness pulls upward on the lap belt with a frontal impact, the "submarine" belt under tension wants to straighten out before it transfers its load to the submarine floor mounting point, in the meantime, allowing the lap belt to ride up into the belly.
7. "submarine" is the common name for the belt, not what its supposed mainly to achieve, in upright seating impacts.
8. There might be a very, very odd impact angle that this belt might prevent submarining in a full chassis car, but it would be something like a hard impact with front of car at an elevated angle say of 45Deg?, ( to get the COG below the lap belt?) and then nothing I mentioned here would have much negative impact anyway.

Anyone have pics of correct mounting?

jcc I don't care if the rule is unanimous, it is on page 42 of the general regulations in the NHRA rule book. I actually check cars to make sure their belts are properly mounted. NHRA made this rule for one purpose, to give the drivers a good chance of surviving a bad wreck.

Raul

JCC... I appreciate your opinion and the detailed thought process you posted, but I can tell you from 15 years of seat specific testing/engineering experience this is not how your body reacts in a crash. I'll try to address your points one by one...


Well Consider with an upright seating position application:

1. On the average person, standing, where is their COG? Just above or in the area of the belly button.
Agreed.

2. In a frontal impact, with a persons legs extended forward and seated, the COG moves higher.
Agreed. But you made a key point here you ignored... the "legs extend forward".

3. The lap belt mainly restrains the pelvic bone, an area able to resist large forces, and its way below the belly button.
Agreed somewhat... I wouldn't call the hip bones "Way below", but doesn't matter.

3. If a person was say standing upright, and was contacted by a moving robust horizontal object, below their COG, they would always fall over the top, they would never skoot/submarine underneath.
Not exactly true...Your body is not a rigid vertical board, and does not react in this way. Anyone that has ever played hockey or football would tell you. If you get hit/pulled in the waist, you're not going end over end. Get clipped in the knee though (Well below the CG), then you will. What happens is your joints freely move, and you somewhat "fold in half". Your chest is restrained from the shoulder belts, and your hips are restrained from the lap belt. What's not restrained are your legs. While the lap/shoulder belts keep the bulk of your mass from moving, your legs continue forward under huge loads. What happens is that your legs actually "suck you under" the belt because they are an unrestrained mass moving forward. This force pulls your body under the lap belt, causing the "submarining" under the belt.

4. The shoulder belts restrains a large chest mass, by transferring impact load to the rollbar, or rear attaching point, AND on the other end to the lap belt. The "and" is the key point here.
Correct.

5. When the lap belt resists the upward pull of the shoulder harness restraining the chest/head/helmet mass, the lap belt is pulled upwards into the soft stomach area with venerable organs, that do not tolerate large forces well.
The lap belt does resist the upward pull of the shoulder harness, however... the lap belt if installed properly is at a 45 degree angle. When the bulk of your body pulls on the lap belt, the belt actually rotates downward. It tries to become parallel with the floor. This downward motion is more then enough to compensate for the upward tension of the shoulder belts.

6. Having a submarine belt used in a curve, means when the shoulder harness pulls upward on the lap belt with a frontal impact, the "submarine" belt under tension wants to straighten out before it transfers its load to the submarine floor mounting point, in the meantime, allowing the lap belt to ride up into the belly.

Again, the lap belt downward rotation towards the floor is more then enough to compensate for the shoulder belt pulling up. The anti submarine belt's purpose is NOT to fight against the shoulder belt force. It's purpose is to keep the occupant in place, and keep you from sliding under the lap belt. The more rearward tension you can put on the anti-sub belt, the better.

7. "submarine" is the common name for the belt, not what its supposed mainly to achieve, in upright seating impacts.

This is not true. It's exactly what it's supposed to do. To be honest we spend an ENORMOUS amount of time in regular passenger cars seat designs fighting against anti-submarining in forward crashes. We don't have the luxury of anti-sub belt, so we have to design the seat frame, and lap belt angles accordingly to prevent this from happening. In some extreme cases we actually use an airbag under the thighs to drive pressure upward in a crash to prevent anti-submarining.

8. There might be a very, very odd impact angle that this belt might prevent submarining in a full chassis car, but it would be something like a hard impact with front of car at an elevated angle say of 45Deg?, ( to get the COG below the lap belt?) and then nothing I mentioned here would have much negative impact anyway.

As mentioned above, the CG is not the issue. Is the mass of the unrestrained legs pulling the rest of the body under the belt that causes the issue.


Here is an excellent example of what I'm talking about.

Notice that this test does NOT have an anti-sub belt. What you see if you watch this a few times, is that the lap belt rotates slightly downward as the belts tighten (Not upwards as you had theorized above). However as the lap belt becomes tight, the occupant's thighs rise, and actually pull the body down/forward. The belts position is fairly predictable. What's tough to predict/control is how to keep the occupant's position in those belts so we can apply force where we need them.

Key points:
1) Lap belt rotates down (slightly... watch the tag), not up. This is because of the reasons I pointed out in point #5 above.

2) Lap belt still ends up on the "gut" of the racer. (Because in this case, there is no Anti-Sub belt). Watch the racers hip motion, you can see as the belt tighten up, the slouching/submarining motion occurs.

https://www.youtube.com/watch?v=bFOprqPmgqQ

Hope the helps explain what's going on in a forward crash a little better. I wish I could share more video's/info, but I don't think my employer would be too happy about divulging that kind of information to the world.

You can believe me though when I say that I have analyzed 100's of forward sled impacts... so I have a pretty good idea of what's going on with this one.

Playing hockey has not been my experience, so I'll pass on that. Focusing on the points we differ:

"6. Having a submarine belt used in a curve, means when the shoulder harness pulls upward on the lap belt with a frontal impact, the "submarine" belt under tension wants to straighten out before it transfers its load to the submarine floor mounting point, in the meantime, allowing the lap belt to ride up into the belly.

Again, the lap belt downward rotation towards the floor is more then enough to compensate for the shoulder belt pulling up. The anti submarine belt's purpose is NOT to fight against the shoulder belt force. It's purpose is to keep the occupant in place, and keep you from sliding under the lap belt. The more rearward tension you can put on the anti-sub belt, the better.

7. "submarine" is the common name for the belt, not what its supposed mainly to achieve, in upright seating impacts.

This is not true. It's exactly what it's supposed to do. To be honest we spend an ENORMOUS amount of time in regular passenger cars seat designs fighting against anti-submarining in forward crashes. We don't have the luxury of anti-sub belt, so we have to design the seat frame, and lap belt angles accordingly to prevent this from happening. In some extreme cases we actually use an airbag under the thighs to drive pressure upward in a crash to prevent anti-submarining.

8. There might be a very, very odd impact angle that this belt might prevent submarining in a full chassis car, but it would be something like a hard impact with front of car at an elevated angle say of 45Deg?, ( to get the COG below the lap belt?) and then nothing I mentioned here would have much negative impact anyway.

As mentioned above, the CG is not the issue. Is the mass of the unrestrained legs pulling the rest of the body under the belt that causes the issue.


Here is an excellent example of what I'm talking about.

Notice that this test does NOT have an anti-sub belt. What you see if you watch this a few times, is that the lap belt rotates slightly downward as the belts tighten (Not upwards as you had theorized above). However as the lap belt becomes tight, the occupant's thighs rise, and actually pull the body down/forward. The belts position is fairly predictable. What's tough to predict/control is how to keep the occupant's position in those belts so we can apply force where we need them.

Key points:
1) Lap belt rotates down (slightly... watch the tag), not up. This is because of the reasons I pointed out in point #5 above.

2) Lap belt still ends up on the "gut" of the racer. (Because in this case, there is no Anti-Sub belt). Watch the racers hip motion, you can see as the belt tighten up, the slouching/submarining motion occurs.

https://www.youtube.com/watch?v=bFOprqPmgqQ

Hope the helps explain what's going on in a forward crash a little better. I wish I could share more video's/info, but I don't think my employer would be too happy about divulging that kind of information to the world.

You can believe me though when I say that I have analyzed 100's of forward sled impacts... so I have a pretty good idea of what's going on with this one."


Would be interesting to see what the empirical data indicates what the unrestrained percentage of mass the legs constitute.
It would also seem that if the lap belt in your example actually moves lower in a frontal impact under loading, the submarine belt would then start to loosen?
If lap belt is mounted at 45deg "optimun" angle, are you saying the reaction of the lap belt under load moving downward is nearly equal to the forces pulling upward by the shoulder harness?
This might be easier to visualize, if the unrestrained mass of the legs equaled the body mass above the lap belt, taking into account the geometry of the belts and COG.
Not an ideal comparison, but a pass car with a 3 pt belt, there is relatively nothing pulling upwards on lap belt, and I'm not aware of high frequency of submaring results from the unrestrained leg forces in frontal impacts, and the chest mass is somewhat restrained by the cross chest belt.

I am handicapped by not looking at 100's of sled tests.

Most belt manufacturer's that I have reviewed suggest sub belt mounted "slightly" behind front plane of chest in upright seating.

I will not go OT and interpret what exactly NHRA motivations are for their rules.

Facts usually are seldom disputed, interpretations are where differences usually occur.

What say you?


Edit:
I don't want to beat a dead horse and add another reply, but you quote some research on percentage of leg mass below, more then I knew, however I think that research in all fairness should take into account a couple of details, its nearly 26 years old ( we have gotten heavier, and I suspect that tends more towards the middle then the legs), the subjects were young Russians ( we all know about dreaded middle age spread), and they were "athletic", ie I would surmise not a lot of fat. So the 40% figure surprised me, I would have guess closer to 20%, and I suspect if the above factors are reconsidered, the 40% number is much lower, as a guess.

Would be interesting to see what the empirical data indicates what the unrestrained percentage of mass the legs constitute.

Legs make up about 40% of the total body weight… so it is fairly significant.
http://www.exrx.net/Kinesiology/Segments.html



It would also seem that if the lap belt in your example actually moves lower in a frontal impact under loading, the submarine belt would then start to loosen?

That is correct. That’s why it is important to put the attachment on the floor rearward of the occupant. It will minimize the loosening that occurs. The tighter the angle between the lap belt and anti-sub belt, the less geometrical loosening will occur. Also remember that the vertical anti-sub belt wills see almost all “tension” in the floor. This will cause significantly more floor deformation (more loosening), then a belt in shear will.

If lap belt is mounted at 45deg "optimum" angle, are you saying the reaction of the lap belt under load moving downward is nearly equal to the forces pulling upward by the shoulder harness?
This might be easier to visualize, if the unrestrained mass of the legs equaled the body mass above the lap belt, taking into account the geometry of the belts and COG.

I’m saying it’s even more. You can see this from the video. With no anti-sub belt, the lap belt still rotates down. The only way this can happen is if the vertical force vector of the lap belt, is greater then the tension of the shoulder belt. The other thing you have to consider is the friction of the belts. The load is not constant throughout the shoulder belt like a static cable/pulley system would be. The high friction/load that is at the top of the shoulders actually creates higher tension in the horizontal portion of the belt above the shoulder, then it does at the other end of the shoulder belt at the lap attachment.

Not an ideal comparison, but a pass car with a 3 pt belt, there is relatively nothing pulling upwards on lap belt, and I'm not aware of high frequency of submaring results from the unrestrained leg forces in frontal impacts, and the chest mass is somewhat restrained by the cross chest belt.

You are correct. In a 4/5 point system, you can’t ignore the fact that the shoulder belts are certainly putting some upward force on the lap belts. However it’s not as large of a force as you may think it is.


Facts usually are seldom disputed, interpretations are where differences usually occur.

What say you?

Well the way I look at it is this… From everything I’ve ever seen in 3,4, or 5 point harnesses testing or FEA modeling, I have NEVER seen the lap belt go “up”. What I have seen is significant occupant movement from the submarining effect that the leg mass causes. Because of that, I would put priority on fixing that issue before worrying about keeping the lap belt down. Remember, even if you had a rigid lap belt (a bar or something), it would not keep you from sliding under it. The ONLY thing that can do that is the anti-sub belt.

That being said, mounting the anti-sub location further rearward (more horizontal belt) is more effective then mounting it further forward (for a vertical belt).

To be CRYSTAL CLEAR… I am not advocating that anyone run any belts with a “curve” in them. The anti-sub belt should be as tight as you can get it when in use, which may require seating modifications to achieve this (on stock OEM seats).