43 replies to this topic

[Sean - MiataCage]

+ 1 for SafeCraft.  Its the only belt I use in all my cars including the cars that are not Miata's.  It is my understanding Charles has received FIA certification so the belts are now good for 5 year.    Fantastic set of belts and Charles is great guy!

 

Sean

[Tom Hampton]

The rules are a minimum and you should make your own decisions. You are free to replace your SFI belts after every race, if you want to. If they are never exposed to sun or rain, you may want to replace them after five seasons. As always, the person who does the annual on your car can require you to replace any belts that are in poor condition, no matter what the date or certification. (SFI or FIA)

I have always used 3", but I am going to the 2" when mine expire.

While true, of course, it seems presumptuous of the SCCA...with no foundation for the ruling (and the FIA, as well).

Saying "you can change your belts whenever you want" assumes that the racing public is informed enough to know that the SCCA extension is baseless.

I always wondered why the FIA recent period was 5 and Sfi was 2...of course, like most everyone else I assumed that the FIA had good reasons for allowing 5 years. Finding that they do NOT, was a bit of an eye opener.

[Steve Scheifler]

Not how I see it at all. It is absurd to have one-size-fits-all rule based on absolute worst case assumptions. Why should a sedan racer in the north who does a few events per season be forced to replace belts as often as someone racing an open cockpit car year round in the south?

It's called personal responsibility and accountability. Set limits at a more reasonable level for the occassional racer then publish guidelines and educate people on how to apply them.

[Tom Hampton]

This is sort of a moot argument. But, it's far from absurd. I've been and engineer for a long damn time at some pretty big companies. The number of engineers that I would trust to make that judgement is less than 20.

However, your precondition isn't even true... No guidelines have been published, and the racers haven't been educated on how to apply them.

What does a weak belt look like by the way?

[Steve Scheifler]

I'm not saying how it is but how it should be. And I'm not talking about how they look, but how and under what conditions they are used. Let's face it, you can look at countless things in racing and imagine how they could be made safer. In classes where cars can be built from scratch a lot of responsibility is placed on the individual to ensure that the car that is "safe", but what that means is far from spelled out in every detail. And in every class it's your responsibility to replace parts that are worn, damaged or just have too many hours on them to trust. I don't see any rules about how long a balljoint can be used even though a failure can endanger not only you but others.

I'm not suggesting a free for all, I just don't want the worst case scenario applied blindly to everyone.

[Todd Green]

This is sort of a moot argument. But, it's far from absurd.

 

Again, what's the difference between racing and street belts?  You never hear of decades-old street belts failing (in any significant numbers.)  So:

 

• There is something different in materials and/or manufacturing
• We're being way overly cautious with our rules (not necessarily a bad thing when it is your life on the line.)
• It's a pretty nice revenue stream for companies if you have to replace your belts every two years.

Again if you think racing is under-engineered, we use nylon ropes for climbing and there are ZERO regulations on replacing ropes.  We regularly take 15-20 foot falls on 9mm to 10mm of nylon cord.  Rope guidelines say they'll last up to 10 years if not heavily used.  But like you, I'm not risking my life to save a couple of hundred bucks and replace mine yearly.

 

Anyway, that's nylon and the little research I did said that FIA belts are primarily polyester, hence the longer validation periods.  One would think the material science is well known to extrapolate the 5 year period.  In any case, I'm surprised no one has done old-belt testing much like Black Diamond does for ropes (and a bunch of other equipment.)

[MotoFusi]

Again, what's the difference between racing and street belts?  You never hear of decades-old street belts failing (in any significant numbers.)  So:

 

• There is something different in materials and/or manufacturing
• We're being way overly cautious with our rules (not necessarily a bad thing when it is your life on the line.)
• It's a pretty nice revenue stream for companies if you have to replace your belts every two years.

Again if you think racing is under-engineered, we use nylon ropes for climbing and there are ZERO regulations on replacing ropes.  We regularly take 15-20 foot falls on 9mm to 10mm of nylon cord.  Rope guidelines say they'll last up to 10 years if not heavily used.  But like you, I'm not risking my life to save a couple of hundred bucks and replace mine yearly.

 

Anyway, that's nylon and the little research I did said that FIA belts are primarily polyester, hence the longer validation periods.  One would think the material science is well known to extrapolate the 5 year period.  In any case, I'm surprised no one has done old-belt testing much like Black Diamond does for ropes (and a bunch of other equipment.)

 

 

Product liability is the culprit. No offense to anyone in the legal profession............. We all have to make a living

[Tom Hampton]

Again, what's the difference between racing and street belts? You never hear of decades-old street belts failing (in any significant numbers.) So:

• There is something different in materials and/or manufacturing
• We're being way overly cautious with our rules (not necessarily a bad thing when it is your life on the line.)
• It's a pretty nice revenue stream for companies if you have to replace your belts every two years.

Again if you think racing is under-engineered, we use nylon ropes for climbing and there are ZERO regulations on replacing ropes. We regularly take 15-20 foot falls on 9mm to 10mm of nylon cord. Rope guidelines say they'll last up to 10 years if not heavily used. But like you, I'm not risking my life to save a couple of hundred bucks and replace mine yearly.

Anyway, that's nylon and the little research I did said that FIA belts are primarily polyester, hence the longer validation periods. One would think the material science is well known to extrapolate the 5 year period. In any case, I'm surprised no one has done old-belt testing much like Black Diamond does for ropes (and a bunch of other equipment.)

I don't know the difference.

The testing has been done. Here is a ppt from Sfi summarizing the data:

http://www.sfifounda...ion 12-2014.pdf

[Cnj]

Tom, it's good data. All based on continuous exposure, a worst case condition of course.

Part of the engineering design that my company provides is rigging systems for performance venues so I'm highly sensitive to repetitive stress design limits, etc - and the need to always design for worst case when we are hanging equipment over people that could/will kill people if it falls. With that said, there are also limits to the safety factors that we apply to the designs. I wonder what safety factor (per the SFI degradation chart) we are applying when every 2 years I replace belts that are stored in my garage 95% of the year and receive direct sunlight probably less than 2% of the year.

CNJ

[RussMcB]

Thanks for sharing that SFI document.

 

" <snip> ... a cycle that included humid night conditions (8 hours light-on followed by 4 hours dark and damp), so the UV radiation approximately represented 80% of the yearly UV radiation of Miami, FL.".

 

Wow.  Can you imagine, under what conditions someone might leave their race car outdoors, for at least 10 months a year, with the belts exposed to sunlight (and rain) as if it were in Miami, FL?!?! 

 

[Tom Hampton]

My company does the same for aircraft structures. How many stress analysis reviews, reports, and fatigue failure studies have I sat through or read? No clue.

I don't disagree with your premise. I agree that our use case is not "worst". However, as you know it becomes a matter of identifying a "standard" use case and defining a test protocol to simulate it. That said, do you think there are scca racecars that spend more time exposed to uv, moisture, and heat than your car? Which case should we design for?

There are so many variables here that are unaccounted for.

My point was (and still is) that the 5 year duration is baseless. The 2 year cycle is probably excessive for the average scca racecar. But, to what extent no one can quantify, not FIA or the SCCA.

I have no issue with a quantified life limit based on actual science. But, again I realize this argument is moot.

[Steve Scheifler]

I don't know the difference.

The testing has been done. Here is a ppt from Sfi summarizing the data:

http://www.sfifounda...ion 12-2014.pdf

Thanks for the link.

I don't need to quantify it with precision, suffice to say that based on their testing I will likely expire before my belts should.

[Tom Hampton]

Lmao. Could be two ways that comes to be true. ;-)

[Todd Green]

The testing has been done. Here is a ppt from Sfi summarizing the data:

 

I'm not talking about some laboratory, worst-case-scenario test of new belts.  The UIAA does that for climbing ropes and puts the number of falls they can take on the rope.  It's generally 8 or less.  My rope is rated for 5.  You know how many hundreds of falls I've taken on it?  Probably over 400 by the time I retire it.  Suffice to say way more than 5.

 

I'm talking about taking real-life expired belts and putting them through pull tests.  Something like this: (Thanks to the person who sent that my way privately.) http://aimss.com.au/...life-extension/

[Tom Hampton]

Missing link...

[Todd Green]

Missing link...

Weird...it was there when I typed it.  Added it back in. Just in case: http://aimss.com.au/...life-extension/

[Tom Hampton]

Thanks.  Seems like that along with a few other studies to repeat the results would go a long way towards extending the life limits for NASA.  And maybe even SCCA beyond the 5 year limit currently imposed. 

 

BUT, 16 harnesses is not a very large sample size.  Particularly, when dealing with uncontrolled, and frankly unknown conditions.  In this case, where one is testing the effects of real-world use cases which are highly varied and unknown its important to establish the shape of the population-curve with enough statistically valid samples.  Sampling technique becomes critical in an experiment of this design.

 

A more thorough research paper describing the sampling technique and more detailed statistical analysis is really necessary to understand how representative the 16 harnesses were for the entire racing population. 

 

As I said above.  I'm all for a data driven life limit.  Just not one that is longer because everyone "wants it to be true". 

[ChrisA]

Suppose you are using OMP's topline belt (I'm not) made with Dyneema, which is strong and UV, water & chemical resistant. Shouldn't it be granted a longer SFI & FiA life?  http://www.ompameric...products_id/664

http://www.dsm.com/p...tors/fiber.html

Actually sounds like an interesting material.

[Todd Green]

Suppose you are using OMP's topline belt (I'm not) made with Dyneema, which is strong and UV, water & chemical resistant. Shouldn't it be granted a longer SFI & FiA life?  http://www.ompameric...products_id/664

http://www.dsm.com/p...tors/fiber.html

Actually sounds like an interesting material.

 

Not surprisingly Dyneema (aka Spectra) is also used in climbing.  Makes for great slings between carabiners for trad routes.  It's drawbacks are that it does not stretch so you really don't want to fall on it (e.g. tether yourself to an anchor) and it has a low melting point.  (Wouldn't want to have your rope run/saw over it.)  I'm not a seat belt engineer, but you'd think you'd want some stretch in the belts to absorb impact and since it can melt at less than 300 degrees that sounds scary in a fire.

[Steve Scheifler]

A little stretch perhaps, but I thought that the problem with nylon for seatbelts is that it stretches too much. Or do I have that backwards?