Musings

[Kitcat]

First: Where'd the engine heat go? All summer I suffered in a cockpit heat-wave comforted by the idea that when it got chilly, that heat would be great. I laughed at the redundancy of a heater & toyed with adding lightness by ditching it. This a.m. it was 32 and I was grateful for the modest warmth dribbling out of the heater. All semblance of engine heat was gone & I would have frozen without my little heater. Of course, it might have helped to put up the top, or at least the side screens but that seems unnatural unless it is raining.

 

Second: I just replaced the 3 point inertia reel seat belt system with the Caterham 5 point harness system. The car feels so much better. Instead of feeling like one good bump would pitch me out, I feel velcroed to the seat and have a better sense of what the car is doing, feel more in control and certainly safer. Biggest single improvement to the car so far (aside from rebuilding the starter so it starts regularly:)).

 

Third: Safety. I added the FIA roll bar and feel more secure with it in place. It weighs about 25 lbs and the little one weighs about 12 pounds so all that metal must be worth some rollover protection.

 

Fourth: Seat belt installation. The shop that put in the belts mounted the crotch strap just in front of the seat. Everything I read says it should be mounted at the back & the Caterhjam guys at Rocky Mountain said mount it on the side seat belt anchor and sit on it and then fasten it. Apparently its main function is to keep the lap belt from riding up above the hips and squashing vital organs. So, does the current mounting location seem reasonable? The installers have built many race cars and have a reputation for being knowledgeable.

[bsimon]

The shop that put in the belts mounted the crotch strap just in front of the seat.

 

Just double up the crutch straps with the side belts as RMSC suggests. I've been told that if the straps are mounted in front of the seats, "other" vital organs could be crushed in a shunt.:ack: I don't know if I completely understand the dynamics rationalizing this claim, but I decided I wasn't about to experiment.

 

The proper crutch strap location is behind the seat. There are two tabs protruding from the rear bulkhead on each side of the car. The straps were supposed to be anchored to these with a bolt and spacer through the bottom skin of the car. Herein lies the rub; If you are using older S-type seats, the back of the runners set on the tabs. Also, one of the passengers side (RHD) anchor tabs is in line with the exhaust bracket if you have a JPE zorst.

 

Since both the JPE exhaust bracket and the seat rails were issues in my car, I placed the crutch straps and the side belts together as RMSC suggested.

 

I suppose a hole could be bored through the seat bottom at a trimming shop if you don't want to sit on the straps.

[JBH]

Rather than offer my opinion, I will refer you to an excellent document by Schroth that describes not only proper mounting points and hardware, but provides addional information on the differences between 5 and 6 point harnesses and the effectiveness of a Hans device. It is recommended reading for anyone using or contemplating the installation of harnesses: http://www.schrothracing.com/docs/Competition_Instructions.pdf

 

Unless I don't understand the advice offered by RMSC, a five point harness can not be mounted at the lap belt points - it has to be centered and mounted to the frame and not the floorboard.

 

It is hard to believe, but in a crash the belts stretch so you want to keep the belts as short as possible by keeping the mounting points as close as possible to the cam/latch.

 

[Kitcat]

RMSC says the strap can be side mounted and used at an angle. After I read and digest the Schroth article (a mere 73 pages!) I will post my conclusions.

[JBH]

Here's what you can do with a five-point harness with the anti-sub straps mounted at the sides. Pretty much all the benefits of a six-point harness using the five-point cam.

http://www.schrothracing.com/ximg/1616/sc_subdualsnap.jpg

[JohnCh]

Here's what you can do with a five-point harness with the anti-sub straps mounted at the sides. Pretty much all the benefits of a six-point harness using the five-point cam.

I'm confused. That picture is of a 6-point crotch strap.

-John

[JBH]

Sorry, that was a little confusing...I was suggesting not using a center mounting point for a five-point and since Kitcat was considering mounting the anti-sub straps back to the sides, I thought it would be just as easy to make it a six-point.

[bsimon]

The Shroth document is an excellent reference. After reviewing it, here's my thoughts;

 

If you look at pages 25 you will see an installation of the crutch straps to the lap belt mounting points. It's a little confusing since they have a stern warning on page 26 that leads one to believe that they are contradicting the previous page.

 

Anti-sub straps must not be redirected. Redirected straps, e.g.

using an OE stock seat for a formula type racing harness and

running the straps over the seat edges down to an anchor point,

will provide extra slack during a crash and the expected

performance will not result.

Slack from such anti-sub strap routing will allow a buckle ride up

during an accident which results in higher upper torso and head

movement. This increases the risk of head impact, head and neck

injuries and internal injury.

 

I think the point they are making is running the crutch straps over high sides of a wide side cushion seat will add unwanted slack. The Seven's plywood bench-board or type-S seats really have no cushioning at that point. I believe that, although not ideal, sitting on the crutch straps would probably be OK in a Seven.

 

Points to ponder;

 

1) Any additional slack in the harness system is a real no no!

 

2) Take a look at how you are restrained in a Seven and ask yourself this; where is the lap belt going to end up in a frontal impact. With a four point system the lap belt will restrain you with all the soft squishy bits in your chest cavity above your hips.

 

3) Crutch straps should be mandatory. Jochen Rindt refused to wear them and had his guts extruded through his facial orifices at Monza in 1970, thus ending his life and subsequent career.

 

Any thoughts?

 

 

 

 

 

 

[JohnCh]

I read this a little differently. I believe that comment was specifically referring to a crotch strap running to the floor of the car in front of the seat, not over the sides – i.e. you should run the crotch strap down a hole in the seat bottom rather than over the front.

 

On page 25 they show that a traditional crotch strap which buckles into a slot on the rotary buckle should run down through the seat to the floor. It should run at an angle from 0 deg to 20 deg rearward. The Profi F models, which run the crotch strap through D-rings on the lap belts and then attach to the shoulder harness buckles, rather than attaching to the rotary buckle, can run under the legs as you described. See page 12 for a comparison of how the crotch straps attach on the F-model vs. normal mounting. Looking at the diagram of the Profi F models, it appears that crotch straps are much farther apart than a traditional 6-point system, and therefore run on the inner thigh rather than in front of the crotch. This is probably why they can be mounted differently. I would hate to think of the consequences of mounting a narrow angle 6-point crotch strap to the rear of the car. Those harnesses will use your crotch as the brake. A properly mounted traditional 5/6-point should prevent the lapbelt from riding up, which in turn will prevent you from sliding under it. It shouldn’t simply act as a crotch brake -- although I'm sure it does that a bit as well.

 

Regarding 4-points, Schroth actually has a 4-point system that addresses the lapbelt movement issue in an accident. Their ASM technology employs an asymmetric shoulder harness system. The inner shoulder harness is longer and the slack is taken up by stitching the extra length over itself. In an accident, the stitching breaks, lengthening that belt and rotating your body outward. As this happens your hips also rotate, thus further tightening the lapbelt and digging it into you beneath your hip bone. This stops you from sliding under the harness. Lapbelt angle is crucial in this system. If it is a severe angle (like my Westfield had before adding new lapbelt mounts) then the lapbelt will ride up too high and won’t allow the rotation of your hips to stop your forward progress.

 

-John

 

[bsimon]

I read this a little differently. I believe that comment was specifically referring to a crotch strap running to the floor of the car in front of the seat, not over the sides – i.e. you should run the crotch strap down a hole in the seat bottom rather than over the front.

 

That's what I first thought, but look at the second "don't do this" illustration under the warning block. It shows the belt over the sides.

 

 

The Profi F models, which run the crotch strap through D-rings on the lap belts and then attach to the shoulder harness buckles, rather than attaching to the rotary buckle, can run under the legs as you described.

 

That makes sense. I couldn't understand the reference to Profi-F after searching the document. Seems I should have been looking for Profi-(something)F.

 

I would hate to think of the consequences of mounting a narrow angle 6-point crotch strap to the rear of the car.

 

Makes me wonder why Caterham designed the crutch strap mounting points on the rear bulkhead structure behind your bum. Not ideal.

 

It looks as though the "F" style belt would be the best choice for a Seven.

 

I'm still a little skeptical about the Schroth break-away style 4 point system.

 

 

[JohnCh]

That's what I first thought, but look at the second "don't do this" illustration under the warning block. It shows the belt over the sides.

Not sure how I missed that second diagram. But then again, I'm not noted for my attention to detail

 

I'm still a little skeptical about the Schroth break-away style 4 point system.

 

Check out this crash test dummy video. It shows the ASM vs. regular 4-point & 3-point harnesses.

 

-John

[Kitcat]

I have done a simple test: Sat with my restraint system (brand new Caterham 6 point belts-NOT cheap, btw) buckled up, as currently installed. It feels great. But when I lean forward with even slight pressure on the shoulder harness, it pulls the lap belt up a little.

 

Assuming a front end crash and the much higher forces it wld generate on the shoulder harness, Scroth's concern that it would lift the belt off my pelvic area into the "soft, squishy" stuff (the gizzard???) are valid. It is simple physics. A very strong upward force on the belt will lift it up. What is needed is a strong downward force in exactly the opposite direction.

 

Hence Schroth's recommendation that the anti-sub belt be mounted thru a hole in the seat centered directly below the lap belt buckle. My anti-sub belt is at a 90 degree angle to the belt buckle and, therefore, useless as a means of stopping it from riding up. I guess it would help restrain my squishy parts post-impact, but making it easy to remove my body from the wreck isnt one of my goals.

 

Since it is a 6 point harness with the anti-sub strap similar to the one pictured above, I may, for now, mount it on the seat belt posts sit on it and buckle it up between my legs. I have read a post on the Miata Forum by a racer who has had this set up and survived 2 bad accidents without harm. Also, the Elise forum notes this is how US fighter pilots do it. But long term, my plan is to knock a hole in the seat and mount the strap there, or buy a dedicated racing seat that has the sub-belt cut-out in place.

[soareyes]

Here is Simpson's recommendations from their web site (www.simpsonracing.com):

 

http://www.simpsonraceproducts.com/images/big_up5pt.gif

 

http://www.simpsonraceproducts.com/images/big_up6pt.gif

 

Lap Belt must be anchored to the frame rail or roll cage as close to the hip as possible at an angle of 45 degrees, but no greater than 60 degrees to the ground.

 

5-Point Anti-Submarine Belt should be anchored on or slightly behind the Chest Line1.

 

6-Point Anti-Submarine Belt should be anchored at an angle of 20 degrees behind the Chest Line as measured from the intersection of the Chest Line and the lap belt buckle. Mounts should be approximately 8 to 12 inches apart (approximately located under each hip and as close to the body as possible). Two routing holes in the seat or a special seat mount may be required. Using the 5-Point hole detracts from the effectiveness of this system.

 

[Kitcat]

The Simpson diagram proves a picture is worth a 1000 words.

 

Also interesting that the Simpson instructions call for a seat with 2 anti-sub belt holes for a 6pt installation. I don't recall ever seeing one like that.

[slngsht]

stan, thanks for the picture. I definitely need to modify my setup.

[JBH]

The problem is finding a secure location to mount the sub. My Caterham has the sub straps mounted just behind the seat because it is the only place with sufficient structural strength. Putting just below the opening in my seat would require welding a horizontal bar spanning the width of the frame. Because of the distance, the bar would have to be fairly thick.

 

The alternative is to go to a Formula harness where the straps feed through D-rings on the lap belts.

 

I am going to contact GT Classics in VA. They run several Caterhams in SCCA events - I am sure they have a solution.

[bsimon]

It sure looks as though the formula type belt set would be of prime consideration.

 

Attaches to existing belt fixations.

 

The individual crutch straps can be separated so you wouldn't be sitting on them when not in use.(although you should probably always use them)

 

The outward angle and minimal intrusion in the crotch area means you probably won't damage your junk in a shunt.:cry:

 

I to am curious as to what the SCCA e-prod Caterhams are using.

[slomove]

Here is another one: Not knowing what I was doing, I used to have the anti-sub belt of my previous 5-points going around the front of the seats. At one time I got a tirade from the NASA tech inspector for that. Since my Cobra seats don't have a hole (and impossible to make one) I swapped the 5-points for 7-points from Racerwholesale ($139) with the center strap still going to the front of the seat (to hold everything down) and the 2 side straps going back under my bum to the lap belt mounting points (to prevent me from slipping forward while protecting sensitive body parts).

 

http://www.racerwholesale.com/images/7102a.gif

 

That held me well in place but unfortunately the setup as designed made the side strap edges press into my thighs and was very uncomfortable. I changed it to cut the side straps from the anti-sub buckle tab and connected the end loops with a short piece of high strength chain that is run over the buckle and under the shoulder belts (not sure if that explains it....). When the buckle is released and the shoulder strap tabs slip out the loop with the anti-sub side straps falls to the floor. Since they are longer now they conform with the thighs and don't bother me.

 

Gert

[JBH]

While researching Mog seats, I came across a thread on the Elise forum that addresses the concern expressed here about mounting sub straps. The Elise has the same issue as the Caterham in that there is nothing but aluminum floorboard if one wants to mount the straps according to manufacturer's recommendations.

 

The solution developed for the Elise looks good so I thought I would post it here. This picture illustrates the point, but if you want all the details, here's a link to the thread:EliseTalk

 

http://www.elisetalk.com/forums/attachment.php?attachmentid=50787&d=1175552566

 

 

[Boxologist]

great, one of my local AutoX buddies is posting in that thread...eventually he'll find his way here.