Harnesses for HANS devices

[DaveK]

Our local hillclimb club has a rule on the books to allow only 3" harnesses. I know that many companies have started offering belts with 2" shoulder straps specifically marketed as HANS specific. In addition, some manufacturers have even moved to offering 2" lap belts as there is thought that 3" lap belts can cause hip/pelvis injuries.

Does anyone have any documentation handy (web sites, PDFs, etc.) that you'd be willing to share so that I can bring materials to our club meeting tonight to try and show them that they are just as safe?

Thanks,

Dave

[Audi UrQ]

I would like clarification on this as well ... perhaps remove mention of specific belt widths from rules (haven't read the different rulebooks or amendments lately, so perhaps this has already been done?), and just say harnesses must meet SFI 16.1 or be FIA xxx approved.


... some manufacturers have even moved to offering 2" lap belts as there is thought that 3" lap belts can cause hip/pelvis injuries.


I don't think anyone is saying that 3" lap belts can cause hip/pelvis injuries, but rather that 2" lap belts fit the contours of the pelvis better, allowing the lap belts to be tightened tighter, thereby potentially further reducing injuries.

[Morison]

I don't think anyone is saying that 3" lap belts can cause hip/pelvis injuries, but rather that 2" lap belts fit the contours of the pelvis better, allowing the lap belts to be tightened tighter, thereby potentially further reducing injuries.
but you spread that load on 2/3 of the area thereby increasing the pressure applied to the pelvis... that's a tough sell to me.

[DaveK]

I would like clarification on this as well ... perhaps remove mention of specific belt widths from rules (haven't read the different rulebooks or amendments lately, so perhaps this has already been done?), and just say harnesses must meet SFI 16.1 or be FIA xxx approved.

How does the FIA or SFI approval work? Are there specific numbers that are allowed, or if the number is higher than what's listed you are good to go?

Dave

[Jgardhouse]

Here's how CARS has it worded...

3. Safety Harness.
(a) Five or six point safety harness of unmodified proprietary manufacture shall be fitted for both
crew members. (Note: It is not permitted to mix parts of seat belts. Only complete sets may be
used.) It is highly recommended that the belts be homologated by the FIA and comply with FIA
standard no 8853/98. All safety harness systems must either have a date of manufacture label
or stamp that is no older than five years from the date of competition, or not exceed the expiration
date indicated on the manufacturer's label.
(b) If the harness is not homologated by the FIA, the following minimum widths apply:
(i) The width of the crotch and pelvic straps shall not be less than 44 mm.
(ii) The parts of the crotch straps which are not in contact with the user's thighs may have
a minimum width of 25 mm.
(iii) The width of the shoulder straps shall not be less than 70 mm.

[Audi UrQ]

It's a specific number relating to a specific specification detailing the tests that the device must meet or exceed to pass that standard, so e.g. SFI 16.1 is the specific SFI standard for harnesses, SFI 38.1 is the specific SFI standard for H&N restraint devices etc.

FIA has specific numbers as well (see above).

[Audi UrQ]

Here's how CARS has it worded...

3. Safety Harness.
(a) Five or six point safety harness of unmodified proprietary manufacture shall be fitted for both
crew members. (Note: It is not permitted to mix parts of seat belts. Only complete sets may be
used.) It is highly recommended that the belts be homologated by the FIA and comply with FIA
standard no 8853/98. All safety harness systems must either have a date of manufacture label
or stamp that is no older than five years from the date of competition, or not exceed the expiration
date indicated on the manufacturer's label.
(b) If the harness is not homologated by the FIA, the following minimum widths apply:
(i) The width of the crotch and pelvic straps shall not be less than 44 mm.
(ii) The parts of the crotch straps which are not in contact with the user's thighs may have
a minimum width of 25 mm.
(iii) The width of the shoulder straps shall not be less than 70 mm.

Notes:
3 (a) should state 5 or more, since some manufacturers now produce 7-point belts (3 submarine belts: leg straps + crotch)

3 (b) (i) 44mm < 2", so 2" crotch and pelvic straps are permitted by CARS

3 (b) (iii) 70mm > 2", so HANS belts that narrow to 2" over the shoulder to fit the HANS shoulder profile are not permitted unless the harnesses are FIA approved.

[John Cassidy]

Check out this link for info that might add or generate more discussion:

http://www.schrothracing.com/products/Competition/profi/profi-II

The Profi-II HANS belt is what we run in our car. FIA certified.

If you have questions, call HMS in Mass and they'll answer all/any questions. Very knowledgeable and the US importer for Schroth harnesses.

And yes, I paid for our harnesses, we're not sponsored by HMS. :-)

Cheers! John

[Mike Hurst]

but you spread that load on 2/3 of the area thereby increasing the pressure applied to the pelvis... that's a tough sell to me.

...but injuries to, and resulting from pressure applied to the pelvis by the belt is not a (relative) problem, the problem is spinal injuries resulting from the lap belt riding upward off the pelvic area and overloading the spine, and this is less likely to occur with a 2" belt versus a 3" belt.

[Morison]

...but injuries to, and resulting from pressure applied to the pelvis by the belt is not a (relative) problem, the problem is spinal injuries resulting from the lap belt riding upward off the pelvic area and overloading the spine, and this is less likely to occur with a 2" belt versus a 3" belt.

A perfect example of why people shouldn't go with what they 'think' is right and should look for a standard that has some science behind it and is widely recognised.

[Mike Hurst]

An hour ago I sat through an SAE paper presentation based on research done by John Melvin and Tom Gideon entitled "Determination of the pressure distribution beneath two and three inch wide Racing Safety Belts". This study was done recently on 15 human volunteers, (pressure applied, no crash), and test dummies at Wayne State University.

In addition to the benefits of fit on the pelvis (which I wrote this morning before the presentation), the study confirmed that seat belts are "edge loaded"...the center of the belt applied little pressure on the body, it's the two edges that apply the force, whether 2" or 3", it's the edges applying the pressure.

[DaveK]

Mike - first off, thanks for joining the thread and sharing! Was any mention of the extra stretch that would presumably result from having 2" belt vs. a 3" belt? I think the info you've provided shows that from a "pressure applied to the body," should be basically the same due to the edge loading, so that should remove one of the safety concerns we're facing.

I think the biggest hangup we're seeing is that people view the 3" belts to be safer simply because they are bigger.

Dave

[Mike Hurst]

Mike - first off, thanks for joining the thread and sharing! Was any mention of the extra stretch that would presumably result from having 2" belt vs. a 3" belt? I think the info you've provided shows that from a "pressure applied to the body," should be basically the same due to the edge loading, so that should remove one of the safety concerns we're facing.

I think the biggest hangup we're seeing is that people view the 3" belts to be safer simply because they are bigger.

Dave

According to the presentation, that was an issue with the nylon belts, but now the 2" polyester belts have less stretch, and a more "friendly" rate of yield than the old 3" nylon belts.

Note that 2" belts are already being used at the pro level, with plenty of real-life severe crashes to prove their ability.

[DaveK]

According to the presentation, that was an issue with the nylon belts, but now the 2" polyester belts have less stretch, and a more "friendly" rate of yield than the old 3" nylon belts.

Note that 2" belts are already being used at the pro level, with plenty of real-life severe crashes to prove their ability.

Thanks for the clarification on that. I noticed that the actual webbing stitching/material was different on my Sabelt 3" FIA belts from 2005 vs. my Schroth 2" FIA belts from 2008, but wasn't aware that they are now using a different material. This may go a long way to helping our club make the transition to the newer technology.

Do you have any documentation you could share with us from the paper presentation?

Dave

[Mike Hurst]

Thanks for the clarification on that. I noticed that the actual webbing stitching/material was different on my Sabelt 3" FIA belts from 2005 vs. my Schroth 2" FIA belts from 2008, but wasn't aware that they are now using a different material. This may go a long way to helping our club make the transition to the newer technology.

Do you have any documentation you could share with us from the paper presentation?

Dave


http://www.sae.org/technical/papers/2008-01-2977