5 Point Harness Mounting

I'm getting ready to install a set of buckets (kid sized) to replace the bench seat, as well as another set of buckets (toddler sized) in the cargo area. I will also be replacing the factory seats with a set designed for use with five point harnesses. All the kid seats are using 5 point harnesses. I need some help with mounting for the harnesses.

I have an internal six point cage (D&C). With the removal of the rear bench, I am planning a C pillar hoop to make it 8 point, with triangulated reinforcement from D pillar to C pillar and C to B. This will allow a harness bar across each hoop (B,C,D), which will also be triangulated if I use one for the kids seats (these seats have an internal triangulated frame to keep the top tether above the shoulder height...just not sure if I want the extra reinforcement).

What I don't know is how much floorpan reinforcement to use for the harness mounts or whether I should be bolting into the cage directly with triangulated reinforcement to prevent bending of the cage during crash forces, which becomes a major issues when seat belts are mounted directly to a cage. The harnesses come with load distribution washers, but the XJ sheet metal is awfully thin in places. The middle row would be fine as it is reinforced for the factory bench seat belts, but the back row is a problem as is the front row.

I know that nobody else has done a six seater setup, but some mount pics from anybody who has done a five point harness for the front seats would be most appreciated. I want to see where you located the mounts in relation to the seats, especially the two lap belt mounts and the anti-submarine belt.

I do have instructions with the belts, but they aren't vehicle specific and therefore are basically worthless beyond the basic safety issues.

Any help is most appreciated. Just trying to map this whole thing about before we get into it.

Nay

get in touch with forewheeler.

he's got a great kid set-up for the back. his kids are protected 100-percent, harnesses, buckets, EXTRA cage and the works.

he should post some pics.

Cool, thanks.

Dave,
when I am in doubt I often use the SCCa rulebook as a minimum guideline. I do understand we are talking about young un's so what I am about to suggest is wayoverkill.

When mounting harness for tin top race cars, I do the this :-

- Mount shoulder belts to a horizontal bar. Belts should mount level with shoulders or in a range of 15degrees down from level. Keep belts as short as possible. Not sure what ends are on yours - are they tabs? Or can you remove the tabs and run the belt around the horizontal tube and back through it's own buckle - best solution.
- Mount lap belts. they should be 45 degrees from horizontal. Do the lap belts have tabs? If so, aa-mfg.com or speedway motors or Summit, sells seat belt mounting tabs. A pack of 5 costs about $10 and is cheaper and easier than fabbing yourself. These tabs can be welded to the roll cage itself. I prefer to use two tabs and "sandwich" the belt tab in-between (in double shear - in other words). If you cannot mount the tabs to the cage then I use the Summit tabs and fab a bracket (still sandwiching the seat belt tab in double shear) and mount the bracket to the unibody. I also make a backing plate of the same dimensions that goes on the other side of the sheet metal. Use a minimum of 10 linear inches for the plate, like a 2x3 or 2.5"x2.5" (total the dimensions along all four sides and must = or > 10")

Kinda hard to explain, but if you need I can shoot pics and send them your way, if needed.

Minimum mounting plate thickness would be 3/16" (adults)

HTH

I mounted my shoulder belts to bars behind my seats. The lap belts are mounted in the factory locations...


Jes

Grant said:

Dave,
when I am in doubt I often use the SCCa rulebook as a minimum guideline. I do understand we are talking about young un's so what I am about to suggest is wayoverkill.

Click to expand...

Overkill is good for your kid's safety...I'll take it .

Grant said:

Mount shoulder belts to a horizontal bar. Belts should mount level with shoulders or in a range of 15degrees down from level. Keep belts as short as possible. Not sure what ends are on yours - are they tabs? Or can you remove the tabs and run the belt around the horizontal tube and back through it's own buckle - best solution.

Click to expand...

I have the Y belts (the two shoulder belts connect and run through one seat slot. They are tab ends for a bolt-in solution. The belts are probably too long to mount directly to the horizontal bar (the kid sized seats are smaller, but still have full sized harnesses as I've could find kid sized) unless it was run way back from the seat...which won't work in my application. How to you reinforce a harness bar so it doesn't simply bend when the forward force is applied during a crash? There isn't any room for triangulation that I can see given the third row of seats. It seems to me it would be better to route the shoulder tether over the bar (with a guide hoop to keep it located properly) and then bolted down into the cage floor. Wouldn't that keep the spinal compression forces from occurring, or do you really need the mount directly to the harness bar?

Grant said:

Mount lap belts. they should be 45 degrees from horizontal. Do the lap belts have tabs? If so, aa-mfg.com or speedway motors or Summit, sells seat belt mounting tabs. A pack of 5 costs about $10 and is cheaper and easier than fabbing yourself. These tabs can be welded to the roll cage itself. I prefer to use two tabs and "sandwich" the belt tab in-between (in double shear - in other words). If you cannot mount the tabs to the cage then I use the Summit tabs and fab a bracket (still sandwiching the seat belt tab in double shear) and mount the bracket to the unibody. I also make a backing plate of the same dimensions that goes on the other side of the sheet metal. Use a minimum of 10 linear inches for the plate, like a 2x3 or 2.5"x2.5" (total the dimensions along all four sides and must = or > 10")

Click to expand...

The lap belts have tabs. The PRP seats have tabs for the seats themselves to mount directly into the cage...can get more (at $.60/ea for 3/16" thick) for the harnesses if they fit...I'll compare to your recommendations. Good point on double shear...I'll definitely do that.

The 45 degree angle on the lap belts...the guide slot in the seat has this angle so I'll just continue it on to the cage. Do you know how much variability is acceptable? Space is pretty tight back there, possibly necessitating a somewhat steeper angle.

What tube thickness is recommended for these mounting points? I am thinking square tube for flat mounting surfaces. I think my cage is .120 wall...and this will have to be thicker I'd think. Any guidelines?

Thanks for the input...very helpful.

Nay

Re: 5 Point Harness Mounting - Jes??

The pix shows the shoulder straps mounted way too wide apart - you could slip out from under them - suggest you move them together behind your head. Most racecar belts have one shoulder strap which wraps around the bar and comes through a slot in the seat - with a stock seat between the uprights of the headrest would be best.

Bob NHRA racing since 61

Re: 5 Point Harness Mounting - Jes??

rsalemi said:

The pix shows the shoulder straps mounted way too wide apart - you could slip out from under them - suggest you move them together behind your head. Most racecar belts have one shoulder strap which wraps around the bar and comes through a slot in the seat - with a stock seat between the uprights of the headrest would be best.

Bob NHRA racing since 61

Click to expand...

???
They slide freely on the bars if you didn't notice.
My new seats will hold them in the proper place when I install them.
Also, I don't use my Jeep for drag racing.

I did some more research, and I think I'll swap out my shoulder harnesses. The seats have a single slot for harness routing, and this is an option for my belts:



The harnesses came with this setup, which is really too long for the smaller kids seats:



That should solve my problems. Now I need to check and see if I can get them in a custom length so there isn't a bunch of extra strap flapping around.

I'd like a straight latch setup for the kids, like this:



But they aren't DOT approved and don't have an anti-submarine feature. Not a huge deal offroad at slow speed, but a concern on payment. Plus they are too long...

Nay

Re: 5 Point Harness Mounting - Jes??

Jes said:

???
They slide freely on the bars if you didn't notice.
My new seats will hold them in the proper place when I install them.
Also, I don't use my Jeep for drag racing.

Click to expand...

Jes, I think you should route them through the headrest bars until you have your new seats. That will hold them in place, and is what I've seen as proper installation for your style seats. You may already be doing this...obviously they are just hanging there for that pic.

Nay

Re: 5 Point Harness Mounting - Jes??

Bob,

In recent years SCCA is recommending to use two seperate shoulder straps rather than the Y-style. I believe (but don't know for certain) that NHRA is as well, certainly in the faster classes.

Reasoning is in an extreme crash the shoulder belts (in a y-style) can cause trauma to the neck. as the driver goes forward the belts tighten and can strangle or sandwich the driver's neck. Thus the recommendation for seperate belts.

I understand it's really semantics, in fact the harnesses in my xj are Y-style and are perfectly suitable for the crawlin' I do.

Another disadvantage to the y-style is that they are typically longer. this means they will stretch further than shorter belts. Of course in a Jeep longer allows more mounting options.

rsalemi said:

The pix shows the shoulder straps mounted way too wide apart - you could slip out from under them - suggest you move them together behind your head. Most racecar belts have one shoulder strap which wraps around the bar and comes through a slot in the seat - with a stock seat between the uprights of the headrest would be best.

Bob NHRA racing since 61

Click to expand...

Re: 5 Point Harness Mounting - Jes??

Dave,

In the "SportBars" (read Roll Bar) we sell for the Mini's and Subaru's I use 1.5" .120 wall DOM for the shoulder harness bars. The bars are less than 3' span, and do not really have any triangulation dealing with a forward motion. The bars are part of the diagonal brace in the main (B-hoop) and do have partial bends in them (to contour around the back of the seat. Those bends would help strength in a forward impact, but only marginally.

If you are using square tube as part of the mounting, I'd go with probably 2" square, at least 1/8" but preferably 3/16" (.187 wall).

Two opinions on mounting the shoulder harness'. If you go over the mounting bar to the floor, no problem (for your application). But there is a school of thought that the seat should be mounted to the cage, and the harness mounted to the cage as well. This is so that in a really bad impact, where the body may rip loose from the cage, the occupants would still be safely in the seat in the cage. If the belts are mounted to the floor/body and the cage breaks loose, it could lead to the belts becoming useless, or actually causing harm. SCCA Rally rules are like this.

The 45 degree angle for the lap belts is a recommendation, but can be varied by 15 degrees in either direction, if needed. Use the slots in the seats as a guideline. The intention is to have the belts aligned with the direction of the force they are likely to encounter. Dale Earnhardt was killed partially as a result of his lap belts being mounted almost directly behind him, which lead to the belt "bunching" in the adjustment buckle, which possibly caused the belt to fail. This lead to his head hitting the wheel, although the actual cause of death was a basal skull fracture.

But obviously your needs are different from a NASCAR, or rally car. I would be happy with mounting the harness's to the unibody if the load is spread over a large enough area. Some parts of the unibody are significantly stronger than others.

HTH

Good points Grant, Nay.
I tried running them through the headrest bars but they pinched my neck so I just run them around the sides for now. To tell you the truth, the only time I have worn them so far has been on the long descents on the Rubicon. There's places where I might nose it in hard off a ledge and could get a face full of steering wheel, so that's when I wear them. Most of the time I just use the lap belt and on the road I use the factory seat belt.
I was wondering about cage/body tie ins myself and wondered if it really matters when your cage and body are designed as one structure? Stock seatbelts are mounted to the B pillar, the door sill near the B pillar, and the tranny hump on early XJs. On later XJs the seatbelts are mounted to the B pillar, the door sill near the B pillar, and the seat.
My cage is really part of my chassis at this point and the B pillar hoop is tied into where the seatbelt mounts, thus I don't think it's a big deal that my seat is bolted in the stock location along with my lap belt and the shoulder harness is tied into the cage. Maybe it's not the thing to do for a racecar but my Jeep really is a rock crawler.
Bla bla bla, I'm rambling, just some thoughts.
Off to URF to build junk, will be back Sunday...

Jes

Re: 5 Point Harness Mounting - Jes??

Grant said:

Two opinions on mounting the shoulder harness'. If you go over the mounting bar to the floor, no problem (for your application). But there is a school of thought that the seat should be mounted to the cage, and the harness mounted to the cage as well. This is so that in a really bad impact, where the body may rip loose from the cage, the occupants would still be safely in the seat in the cage. If the belts are mounted to the floor/body and the cage breaks loose, it could lead to the belts becoming useless, or actually causing harm. SCCA Rally rules are like this.

Click to expand...

That was my orignal thought - tie everything into the cage so that the seats and harnesses will all stay together, even with moderate cage bending in a serious accident. I don't plan to run the kids around on the road much in the XJ, but we will use it to get to the trail. I think I'll keep the idea of mounting everything to the cage. This will be an interesting cage when it's done with the three rows of seats .

I also just found kid sized 5 point harnesses from two different companies. One of them has the five point cam lock design vs. the latch design (much less bulky)...I'm going to get specs to compare to the adult sized belts and may be buying these for a better fit.

Thanks to all for the help...very useful for an important topic to me.

Nay

Re: 5 Point Harness Mounting - Jes??

Cam lock design is much better than the latch. The only reason to go with the latch setup would be cost. Simpson belts, the difference is almost $100, so cheap bastard I am, the Mini has latch belts.

But ease of use the cam design is better. Although with kiddies - would they be able to "accidentally" undo the cam? The latch takes considerable more finger strength to undo.

Re: 5 Point Harness Mounting - Jes??

Grant said:

Cam lock design is much better than the latch. The only reason to go with the latch setup would be cost. Simpson belts, the difference is almost $100, so cheap bastard I am, the Mini has latch belts.

But ease of use the cam design is better. Although with kiddies - would they be able to "accidentally" undo the cam? The latch takes considerable more finger strength to undo.

Click to expand...

Yep, that's what I was thinking. How are the cams released? It's not obvious from the pictures and I've never seen one in person.

No way they'd get the latch undone strengthwise...but that's an awfully bulky piece for toddlers...

Nay

Re: 5 Point Harness Mounting - Jes??

The camlock designs I have used are spring loaded and need no action when inserting the various belt clips. A good thing, especially with kids, compared to the latch design when one hand holds the latch, one hand holds the shoulder belts, and one hand holds the lap belts. See the problem.

For release the cam design requires a quarter turn counter clockwise (some need a half turn) and then all the belts release. Quick and easy. But possibly too easy for junior to figure out after Dad does it a few times. Possibly the cam locks for kiddies have a feature to prevent this sort of release.

If money is not the main deciding factor then I'd definitely pitch for the cam design.

I'm checking the RCI Racing specs, as they are the only ones to offer the junior harness with cam...at least as far as I've found Googling all damn afternoon. I'll post back when I get some info.

I'm hoping others find this interesting. If you have two kids or less, you can remove your bench seat and strap their little butts into a five point harness in kid sized seats...and then you have enough room for a 35" spare in the cargo area along with other options. This is a really sweet way to open up cargo space...which I'm just filling with more kids.

I thiink I need to be doing this in one of the older fullsize Land Cruisers and stop trying to turn my XJ into a 4wd schoolbus .

Nay