utkinpol

Hi,

I tried to find a definitive answer and failed, may be I just looked in wrong places.
Is it under any regulations - how long can those shoulder harness straps be - between back of the seat and harness bar mount?

on a picture attached it only says 'mount 0 to 10 degrees below shoulder'. but how long those straps can be?

Regards, Paul.

911SLOW

From Schroth

"Shoulder Belt Routing (applies to all restraint types)

· Shoulder belts must run from the shoulders horizontally or down, at no more than a 20° angle.

· In cases where the shoulder belts must be routed down to the chassis floor, support by a roll cage bar or harness guide at the appropriate height is essential to establish the horizontal shoulder strap routing off the shoulder/HANS®. Most racing seats are not designed and tested to carry shoulder belt crash loads from downward installation. Severe injury or death could result. A 45° downward shoulder belt installation is possible with seats that SCHROTH has positively tested to take a load measured during a 50 kph [31 mph] and 28 G impact with a 75 kg (175 lb) dummy. Refer to the list of SCHROTH approved racing seats in section “About Seats”. WARNING: 45° downward shoulder belt installation is not recommended with HANS®.

· For the best restraint of the occupant’s upper torso, ideal anchor points should not be further back than 200 mm [8”] from back of user’s seat.

In the event that the anchor points are further towards the rear of the vehicle [e.g. using a roll cage bar for wrap around attachment] the distance between the strap anchor points will narrow or even cross over as described in following graphs and tables.

· It is especially crucial to follow this strap routing when HANS® is in use."

cfjan

Usually the shorter the better.. (less stretch during an impact) But you see Cup cars running the harness all the way back too.. so I guess it is probably not a big deal..

utkinpol

<=200mm. I see. Is it also in PCA rule books? It does not really say there 'forbidden' but 'discouraged' is strong enough verbiage for me.

I just saw some (crazy) folks at AX who run harnesses attached over the rear seats to the bar at the very end of the vehicle and got curious what actually regulates all that stuff. I have BK R-1030 bar so it would be a convinient cheat not to mount a removable bar part and simply extend shoulder belts to the bar that sits on top of rear strut bolts. but I guess DE tech chair will not like it too much.

thanks for a detailed response.

utkinpol

yep, that is where I get confused.
I have C2 car with rear seats, so for me to put on harness bar in and out is a PITA to some degree, so, it would really be great to find out what is the official word on this subject.

LVDell

Actually from what I have read, you want some length to allow the belts to stretch reducing the impact. But then again I'm not 100% sure which is correct.

utkinpol

it looks like in my case it will not work anyway - I just went down to garage and measured ends of shoulder straps, they are not long enough to reach rear bar and be properly tightened anyway, they are short by a half foot at least. i suspect all manufacturers enforce those limits of how long those straps can be.

cfjan

Dell, I was just going by my comment based on the reading the Schroth manual when I was installing my harness.. it implied that the shorter the better (please also see 911SLOW's post above, i.e., ideally, less than 20cm) due to less movement of the body.

But yeah, that's just my assumption based on what I read.. I don't have any hard science to support that..

911SLOW

"
What happens during a frontal impact:

This data is based on an optimised installation with an upright seating position during dynamic testing. It simulates a 90° head on collision, utilising a 75 kg [165 lb] mass dummy, an impact velocity of 50 kph [31 mph] and a stopping distance of approximately 400 mm [16”] with a maximum deceleration of 30 g [FIA Standard 8854/98 dynamic test requirements]:

· The pelvic load, expected to surpass 14 kN [3,100 lb] at each side, will elongate the lap belt and compress the tissue on the pelvis. The pelvis will slide forward by 80 to 100 mm [3”-4”]

· The upper torso load is expected to surpass 7 kN [1,550 lb] on each strap, will elongate the shoulder belts, the upper body will roll in, the adjusters will move up the chest by approximately 200 mm [8”] and forward head trajectory will be up to 400 mm [16”]

· The pelvic movement combined with the shoulder belt forces will load the anti-sub straps to more than 6 kN [1,320 lb] each in a 5- or 6-point racing harness and can be intentionally higher in a F‑type model where the anti-sub straps are routed rearwards.

In more reclined seating positions, the pelvic load will be reduced to approx. 9 kN [2,000 lb] since the seat pan, designed as a ramp, will take some of the load. Therefore it is essential the seat or chassis manufacturer ensure the seat pan is strong enough not to bend or even collapse under extreme loads.

In any case, seats are a significant component of the safety system!



What does the discussion of frontal impacts mean to the occupant?

The numbers above seem to be quite high when compared with actual racing accidents. Fortunately, most racing accidents are not 90° head-on collisions. Car deformation is greater than the 400 mm [16”], and modern soft walls also convert impact energy. Therefore, accidents with higher impact speeds are often less severe than the FIA required test set up. However, SCHROTH racing harnesses have been tested to speeds and decelerations surpassing FIA requirements."

911SLOW

See how far body travels even at the pelvic area held by the short lap belts..

"will slide forward by 80 to 100 mm [3”-4”]"

ace996

And guys, let's make sure those 5+6pts are properly secured and tightened...don't make me post that "degloving" link again...

LVDell

John, in English please. It's too late for me to read technical crap. It's beer:30 time for me

911SLOW

in greeklish the shorter the belts the better.

size matters but not for belts.

drink one vodka for me later

cheers

LVDell

The Grey Goose is flowing my good friend