Have you watched slow motion crash videos and seen how much people flop around inside cars with 3-point belts? They're really designed for 35 mph crashes.

Crash safety starts by keeping the occupants in one place relative to the chassis so that the chassis can deform and absorb energy. This lets the occupants go from 60-0 in 4-5 feet instead of six inches, thus decreasing the maximum gees they experience. 3 point belts do a much worse job of keeping the occupant in the proper location, partly because of the fewer anchor points, but also because they're designed to be loose/spring loaded (and then tensioned actively during the accident), rather than cinched down tightly the way 5/6-point harnesses are. They also provide less surface area for transferring load to the body, which increases the risk of the injury from the belt itself.

Note that infant safety seats are 5-point, not 3.

--Ian

 

I have, but why is "flopping around" in the car a bad thing? The additional motion just serves to further reduce peak g-forces, no?

Crash safely doesn't "start" anywhere, IMO. It works as a full system. The 3-point belt allows for additional movement, which is why in recent years airbags have been added to the mix to protect the head and body in big impacts. Changing one component of the system may not be the best way to go.

My point is that I'd rather have my entire body flop around in a 3-point than allow my head to flop around independently with a 5/6 point.

They're also generally rear facing, specifically to support the head/neck/spine

 

So we need those new VR goggles and some cameras, then drive backwards.

 

No, flopping around the car means there's all kinds of things body parts can hit (roof, dash boards, other passengers, steering wheels, etc) and it means that the belts will not necessarily be located across the correct parts of the body. There's no anti-sub strap on a 3-point, it relies on the upper torso folding to try to keep the the lap belt from digging into the abdomen, and it doesn't always work.

Crash safety is about two things -- slowing the occupant to 0 mph in as much time as possible in order to decrease the acceleration that he/she experiences, and keeping intruding objects from causing direct trauma. The latter is what the cage is for, the former is what belt stretching, airbags, and impact-absorbing structures are for (crumple zones, F1-style deformable noses, etc). For the impact absorbing structures to work properly, the occupants need to be located in the positions that the engineers expect them to be in, and 5/6-point belts do this better than 3.

3 point belts are a safety compromise. They're better than 2 point and WAY better than nothing, and they're about the max level of inconvenience that normal people are willing to put up with on the street. 5/6-point belts are a PITA, you can't even lean forward to adjust the radio, let alone get your wallet out at the drive-thru, and they take significant time to put on properly when alone. If you put those in street cars, no one would use them.

Infant seats are rear facing for the first year (some people are now recommending first 2 years) then front-facing until the child is big enough to use a normal seat belt with a booster seat (somewhere between 4 and 6, depending on the child).

--Ian

 

A body whipping about will accelerate at the end (towel snapping analogy.) The increased velocity increases the risk of injury, either by hitting something or by damaging soft tissue by elongation and contraction. I'm not just fitting up my car for worst case scenario. There's a good video earlier in this thread posted while discussing air bags (I don't remember by who.) The driver put the passenger side wheels off and then shot left across the track and into a wall when regaining traction. Driver had 5/6 pt and passenger had three point. The difference in movement was dramatic. Also, I recently spun after loosing the back end to the left, (not enough revs on a down shift) over correcting and having the tail swing right, catching that but then driving onto the grass and completing the spin to the left. I was glad to be planted in the seat throughout that learning experience.

 

I'd rather have a 5 point in a rollover than a stock 3 point, fwiw. I'd also prefer a rollbar rather than the stock protection in that instance.

Since this is a safety thread:
Ridewhencan, please don't drive that car on the street without first installing some high density padding on the rollbar. A minor rear end collision could potentially split your skull if you aren't wearing a helmet. Pool noodle type padding, even though sold in some race shops, is not the correct material for protecting your head. They usually have both the noodle and the high density types at race shops. You want the harder one.

 

Slight change of topic. HMS motorsports has older cobra seats on sale for cheap. I just got a cobra racer pro for $615 with free shipping and two years left on the FIA cert.

I'm going to use this on the passenger side since it has tall shoulder openings and a good sized 6 point opening. What is the polite way to get an instructor that fits in your passenger seat? I tried to fit several wider seats (momo start, suzuka GT, imola S) but my door bars are tied in right at the front/widest edge of the seat and there isn't room for a wide seat. I don't want my passengers to be forced into a seat they don't fit into/won't be safe in.

 

I have the Hard Dog SFI approved high density padding with the HD vinyl cover. You are recommending additional padding or the perhaps hard dog pad doesn't show through in the pics? Car is basically just driven to and from track days and I sit a couple of inches below the bar but I've hit the side of the bar (3 pt restraint) with a helmeted head and have some idea of the force that can be generated.

 

SFI padding is still designed for a helmeted head. Not your bare skull.

 

Hard to see in pics when on mobile app. Now that I'm on the computer I can see it. It is good you have it.

Well, it is better than not having it.

 

exactly right.

 

It's about preparing for the most likely collisions. I do lots and lots of track days. Rollovers are not common. Big impacts with walls happen maybe 3-4x as often as rollovers. If given the option to hit a wall with 3-points vs. 5 points and no HNRS, I'm wearing the 3-points with a stock airbag. That's my opinion and my choice, and you may disagree. My point is that safety systems are just that - systems. You cannot alter one part of the system and expect to make it safer. Until you have the rollbar and the HNRS to match, the 5-points may not be as good as the 3-points you replaced.

This is why I have a 3-point and OEM airbag on the street, and a 6-point with HNRS, FIA containment seat, and airbag delete for the track. Two complete safety systems for two different situations.

 

Right. i also look to what kind of tracks you run when are planning our a cage. down here by us we have either concrete walls (road Atlanta) or a poorly stacked tire walls (CMP,Savannah) the concrete walls stop cars fast, and they get hit at a real speed. for this i built out the foot box a little more. the poorly stacked tire barriers have a tendency to sent cars into the air. for that i built my cage as tall as i could. gives me a little more vertical height.

 

Bumping this up, just because. I ran my first wheel-to-wheel race last weekend (LeMons) and it just got me on the topic of safety. I think it's hugely underestimated far too often, so bringing the topic back up is never a bad thing. I read through the whole thread a long time ago, so it's not fresh in my memory how much of this stuff has been gone over already.

Personal safety (risk prevention that only affects you as a driver) is a calculated risk that the driver needs to assess. I think the flow chart does a good job of determining the safety levels, what is not acceptable on a track, what is semi-safe and so on. It's up to the driver to determine which of the "green" category they need to fall in, and what they are able to fall into (based on cost, how much it's used on the street, etc). For example, I used to do HPDE with 6-point, roll bar, Kirkey seat with brace, helmet, jeans, SFI gloves, and SFI shoes, with a low-boost turbo setup and brakes that were plenty stout for the power. I do realize now that I should've invested in a HNRS to go with the 6-point, but besides that I was a rookie driver on a slow track that I never saw over 95 mph on, and I was controlled and timid enough to keep it on the track. This coming season, I'll have an LS1 with a totally new fuel system, fuel tank pressure release system, more than twice the power (and heat), exhaust on both sides of the transmission tunnel, and in general a super fast car that's essentially a prototype (ie: most of the systems I put together, turned the wrench, etc). I now have added a HNRS, SFI3.2A/5 suit, SFI balaclava, and SFI socks. I feel it was necessary due to the added risk of an unvalidated fuel system, much faster car, and I will be exploring some faster tracks, as well as pushing the car harder with more experience now.

Do center/window nets and wrist restraints accomplish the same goal? Keeping hands and arms away from danger, or do nets serve another purpose? In FSAE we always needed wrist restraints, and in LeMons we were required to also (we run a Mk3 Supra chop-top). I'm surprised I haven't seen any discussion about them here, and didn't find anything when searching the threads.

 

arm restraint is just that, restricting arm movement in case of an accident (mainly roll over protection for open top cars, but also help with arm exiting window. Miata hard top also don't much in case of a roll over).

window net also serve a function of flying debris protection.
center net serves 2 functions (could be more): 1. restrict your shoulder from moving side way during side impact while your head is held in a halo seat. if you don't have a halo seat, it kinds of acting like one. 2. a lot of people don't install center correctly. 2 of 3 straps actually wraps around to driver side's roll cage and should be very snug around the seat.. It also helps holding seat in during a violent impact.

 

Thanks for resurrecting this thread, acedeuce - I just spent several hours reading through it. I just bought an MSM specifically for track use (see my thread about it here). It was set up by someone else who's since given up track driving, but there are some things that may or may not be a good idea, from a safety perspective.

First, door bars:

He added Hard Dog door bars, which seem to do wonders in terms of stiffening the chassis.


However, OG mentioned that, unless properly supported on one side, they could act as "mouse traps". I borrowed this picture from Bethania's web site, showing the rear mounting set-up:

So, what say you all? Leave 'em in or yank 'em. What's the reputation for this part?

 

Second question is about the 5-point (SFI-rated) harness that is installed on the driver side. First thing you'll notice is that the car still has the OEM seats. Some nylon webbing loops were sewn into each side of the seat in order to keep the strap in place. Will these suffice? My instinct tells me that they won't hold up to any serious force, but will the strap tighten the properly (i.e. not slip off the shoulders) in a collision?


Where should the outside lap belt should lie. Over or under the door bar?


Now's the biggie. Since the OEM seat doesn't have a pass-through for the anti-submarine belt, am I not protected properly?


The bottom seat cushion crushes when the belt is cinched tight and I can't force myself forward. I understand that the forces in even a minor collision are far greater than I can exert by muscle power alone, but I'm not sure about the "rules" about this set-up.


I don't take many selfies, but here's one of me belted in:


After reading through this thread, I had a sinking feeling that things are not up to par as is. I could toss the OEM seat for a race version, but then driving to and from the track (with the OEM seatbelt) presents a risk. Or, I could toss the harness altogether and rely on the 3-point OEM belt, with all its attendant flaws.

Appreciate any advice from the gurus. Thanks.

 

The anti-sub straps are mounted completely wrong and the shoulder harnesses are very dubious.

There are race seats that can be plausibly used with factory 3-point belts, at least for normal size adults. I do that with the Recaro Pole Positions that I have in my Miata.

--Ian

 

In for info on this.

 

1. Door bars - While those ostensibly should provide more side protection than, say, nothing, I think their greatest benefit would be an offset frontal impact. Bracing against the back wall of the cabin to try to prevent the front and back half from folding up like a soft taco seems like a noble cause for keeping them. Keeping my knees from getting closer to my pelvis seems like a good idea.

2. The five point harnesses are fine, with the proper seat and mounting. You don't have the proper seat and mounting. I would use the stock seatbelt with the stock seat and the harness with a seat designed for a harness. The arrangement pictured is dangerous. Get a Kirkey or something similar to bolt in for track days and double check the mounts for those belts. Make sure they have good mounting points with oversize backing plates. The lap belts can sometimes use the stock points.