How to install a point harness?

[Horse]

I'm trying to figure out how to install some bracketry that will be sturdy, but removable for the installation of a 4 point harness for racing autocross. There really isn't a decent forum for this, so I guess I'll post it here.

My original idea was to make a bracket that will bolt to the two bolts that hold the back of the driver's seat to the floorpan, but I don't think that those two connection points will be enough to prevent forward motion in case of hard braking or, god forbid, a crash. Then I thought of bolting a bracket to the seat bolts and then flop down the rear seat and make two more points to connect it to in the trunk, so i'd have two bars that ran up the back of the seat and were connected to the seat bolts and then another peice that ran from the top of those bars back to my connection points in the trunk. that seems problematic though because I think I might hit the gas tank when trying to drill the floor of the trunk, and I don't want to drop the tank.

Here's my last idea. How much weight are those seat anchors rated for? You know the ones that sit up on the rear dashboard and are covered by little plastic lids. I think that they are for baby seats. Do you think I could bolt something to that?

I'd REALLY like some input on this.

And, yes, I know a 4 point roll cage would make it easy, but that will change my class, and I don't want to do that.
Thanks.

[lowflyn]

If you are wanting these to seriously hold, then don't just drill a hole in your floorboard to put them in, you need to tie them into the frame.

[Monkey]

4pt are bad. either stick with your stock 3pt or go to a 5pt setup. 4pts create an effect called Submarining. This is where the chest is restrained in the event of a wreck, rollever, etc. and the lap isnt. I have ridden in a car that had a 4pt harness and the camlock sat near my belly button. Your hips actually end up sliding toward the steering wheel and then you get stomach and abdominal lacerations due to the straps stopping your abdomin instead of your hips. You can get an anti-sub belt (5th point) and put it into your floor board so you don't need a new racing seat.

Eventhough I know you autoX and there is little danger of wrecking or rolling over, it does happen.

But, to answer your question. You want harnesses mounted in at most a 45* angle to the driver. The only real options for mounting would be these:
1) Between the back seat bottom and top. There are a couple bolts back there that could support the stress of shoulder harnesses and you can put the seat bottom back on to retain in your class. That is about a 45* angle.
2) The seatbelt things on the rear deck. Those are actually welded into the frame of the car. Those are your best bet. What's best about those is that you can buy harnesses designed to bolt up to those. They come with a little anchor bolt and you put it on those. Then there is, in effect, a seatbelt locking mechinism that connects that to the harness. That way, you can take the harness in and out with just unclasping the seatbelt lock.

#2 is how I would do it. Run the long shoulder harness straps (remember, has to be 3" to be legal in any type of race) to the rear anchor mounts and then the two lap belts to where the seatbelt normally resides.

[SpectorV]

you should mound a bar across the back of your head rests to mount the top belts, so they are straight back from the top of your shoulders, Get a 5 pnt harness.

[Horse]

Why would they have to be 3"? My seat belts now aren't even quite 2".

Also, the submarining only happens if the lap belt is set too high, if you are wearing it right and it's mounted right, it should be no different than the lap belt on the existing 3 pt belt the car started with right?

I think what I've decided to do is to fab up a cage out of 1"X1 3/4" rectangular steel tube and bolt it in where the power seat rack is bolted to the floor, then run it back to the bolts under the rear seat, and run it up the back of the seat level with the back of the driver's seat. I'm then going to strap the top of it to the anchor mounts on the rear dash to help toughen it up even more... That ought to work.

Thanks for the ideas, they helped. I'll have to get some pics of it when it's done.

[Monkey]

Quote: Originally Posted by Horse Why would they have to be 3"? My seat belts now aren't even quite 2".

"Three (3) inch lap and shoulder belts are the minimum standard required." from one of the local races here. It is jsut the rule. I can see the rule being because there are plenty of 2" belts on the market like on ebay and whatnot for the pair for under $30. Those offer no real safety issues and the racing community knows this. A real set of harnesses are gonna cost you over $100 for each one. minimum.

Quote: Also, the submarining only happens if the lap belt is set too high, if you are wearing it right and it's mounted right, it should be no different than the lap belt on the existing 3 pt belt the car started with right?

No. It is just natural with 4pt harnesses. This is because when you tighten the shoulder straps, the locking mechanism moves up to your stomach area. Just normal physics. If you bolt the lap belts more forward, then you have no lap support and have even worse submarining effect. 4pts are fine for autoX. Just do not do any other racing with them. A 5pt is so much better. A 5pt harness system costs literally less than $10-20 more for each harness than a 4pt. People know they will have to buy the 4pt, and to pick up the anti-sub belt (5th point) is another ~$15. totally worth it.

Quote: I think what I've decided to do is to fab up a cage out of 1"X1 3/4" rectangular steel tube and bolt it in where the power seat rack is bolted to the floor, then run it back to the bolts under the rear seat, and run it up the back of the seat level with the back of the driver's seat. I'm then going to strap the top of it to the anchor mounts on the rear dash to help toughen it up even more... That ought to work. Thanks for the ideas, they helped. I'll have to get some pics of it when it's done.

You're basically talking about a harness bar. Just a bar that runs behind the front seatbelt about shoulder hight to attach the harnesses. Good design. Just please remember my reply about the 45* rule. Do not connect it at more than a 45* angle.

Oh, just another quick piece of advice. Harnesses are only good for 5yrs. They come with a date on them and they are good for 5yrs after that. After 5yrs, you have to replace them completly. They also fade and lose strength in the sun. So take them out when you are not going to be racing. Also, I would 100% always use the stock seatbelt for daily driving. The harnesses make it hard to see in any direction except straight forward and you cant reach the stereo very well, etc.