Joined: November 7, 2008, 4:48 am Posts: 1097 Location: snow city - it's wet!
Hi Photo, I'm not looking to be contrary, but I was wondering if you had considered how your belt arrangement would actually function in a front end impact. There are some subtle things at play here and I figured I would ask.
Generally, on production vehicles the belts cross the upper body from the upper, outer edge of the seat to the lower inner point of the seat. This loosely acts as a hinge that rotates the upper bodies of both occupants towards the outside of the vehicle and away from each other in a frontal impact.
Your set-up would have the hinge effect reversed, and in an impact would tend to swing both upper bodies inwards towards each other. My concern would be the possibility of the occupants bumping heads quite hard in a significant impact. I've seen video of cases were even fully belted in racers have had their head and upper body travel close to a foot in a big impact. I'm not saying your situation would not work or isn't safe, but it might be worth thinking about. And of course all of this comes with the standard "I'm not an engineer, and have never played one on TV" disclaimer.
john hennessy wrote:
last time i posted something about Barry Massivenose i got shouted at.
Huh, and here I spent all this time thinking it was Barry Banananose...
Joined: October 6, 2009, 9:29 am Posts: 7651 Location: Tallahassee, FL (The Center of the Known Universe)
It's Barry Pantyhose and Dodge Vipers used to have the shoulder belts "backwards" to other cars going from inside shoulder down to the buckle. FWIW...
_________________ JD, father of Quinn, Son of a... Build Log Quinn the Slotus:Ford 302 Powered, Mallock-Inspired, Tube Frame, Hillclimb Special "Gonzo and friends: Last night must have been quite a night. Camelot moments, mechanical marvels, Rustoleum launches, flying squirrels, fru-fru tea cuppers, V8 envy, Ensure catch cans -- and it wasn't even a full moon." -- SeattleTom
Joined: October 6, 2009, 9:29 am Posts: 7651 Location: Tallahassee, FL (The Center of the Known Universe)
Warren Nethercote wrote:
As do the back seats of some cars - Bimmers I recall.
Where it wouldn't surprise us to find Barry Pantyhose...
_________________ JD, father of Quinn, Son of a... Build Log Quinn the Slotus:Ford 302 Powered, Mallock-Inspired, Tube Frame, Hillclimb Special "Gonzo and friends: Last night must have been quite a night. Camelot moments, mechanical marvels, Rustoleum launches, flying squirrels, fru-fru tea cuppers, V8 envy, Ensure catch cans -- and it wasn't even a full moon." -- SeattleTom
Joined: July 26, 2010, 10:37 am Posts: 752 Location: Tennessee
erioshi wrote:
Hi Photo, I'm not looking to be contrary, but I was wondering if you had considered how your belt arrangement would actually function in a front end impact. There are some subtle things at play here and I figured I would ask.
Generally, on production vehicles the belts cross the upper body from the upper, outer edge of the seat to the lower inner point of the seat. This loosely acts as a hinge that rotates the upper bodies of both occupants towards the outside of the vehicle and away from each other in a frontal impact.
Your set-up would have the hinge effect reversed, and in an impact would tend to swing both upper bodies inwards towards each other. My concern would be the possibility of the occupants bumping heads quite hard in a significant impact. I've seen video of cases were even fully belted in racers have had their head and upper body travel close to a foot in a big impact. I'm not saying your situation would not work or isn't safe, but it might be worth thinking about. And of course all of this comes with the standard "I'm not an engineer, and have never played one on TV" disclaimer.
john hennessy wrote:
last time i posted something about Barry Massivenose i got shouted at.
Huh, and here I spent all this time thinking it was Barry Banananose...
Actually, I had not considered that. I have considered and may switch to a reel-less system. If I switch, then I can mount the bolt on the outside of the roll bar. Not sure just yet. Thanks for pointing that out.
Joined: April 5, 2008, 2:25 am Posts: 4829 Location: Fort Worth, Texas
I hadn't thought of the hinging effect.
While some of the Vipers may have the reverse belt arrangement they also have a center console that's twice as wide as other cars. This gives extra room for hinging towards each other.
_________________ mobilito ergo sum I drive therefore I am
I can explain it to you, but I can't understand it for you.
Joined: July 17, 2008, 9:11 am Posts: 6414 Location: West Chicago,IL
The "hinging effect" may sound plausable in theory. So I went looking at crash test photos. Every one I see shows a straight path to the steering wheel (and passenger side too) airbag. I know we don't have airbags but the body and head path should be the same, at least until the belts stop stretching.
Any further info you can provide? I'm interested.
_________________ Chuck.
“Any suspension will work if you don’t let it.” - Colin Chapman
Joined: November 7, 2008, 4:48 am Posts: 1097 Location: snow city - it's wet!
rx7locost wrote:
The "hinging effect" may sound plausable in theory. So I went looking at crash test photos. Every one I see shows a straight path to the steering wheel (and passenger side too) airbag. I know we don't have airbags but the body and head path should be the same, at least until the belts stop stretching.
Any further info you can provide? I'm interested.
No, actually.
Although the last time I was in a really big hit with just a standard shoulder belt and no airbag, my cranium did wallop the side window hard enough for me to blank out for 3 to 4 seconds. I cannot attribute all of that to the shoulder belt however; in my case the direction of impact played a big role.
Or perhaps I can find something that shows the tendency I was suggesting. After writing the above, I decided to see what popped up when I googled for "no air bag frontal crash test". Among the videos returned where the following three. Each of them tends so show what I'm talking about, although it seems the sideways motion is from less of a hinge effect, and more from a spring effect as the occupants are being returned upright after the impact. In each of these, the occupants are being tossed towards the outside edge of the car on their return to being upright.
The third video is probably the hardest to read, as it's a 1/2 frontal impact and the car is being spun by the hit. While the occupant on the left side of the car reacts normally to the spinning, the occupant on the right side of the car bounces straight up, centered in their seat, ignoring the spinning motion of the car which should have tossed them strongly to the left. The right occupant does in fact begin to move strongly left after returning upright and reaching a point where the shoulder belt is no longer constraining their movement.
The good news in all of this is that it appears there is less lateral movement that I was expecting. Although in a locost, both occupants are very close together.
As always - I am not an expert, and a couple YouTube videos do not turn my theory into fact.
edit: And thinking about this, if the mods or Photoman would prefer this discussion split off into another area of the boards, I support the idea. This is a topic that might merit it's own discussion thread.
Actually, I had not considered that. I have considered and may switch to a reel-less system. If I switch, then I can mount the bolt on the outside of the roll bar. Not sure just yet. Thanks for pointing that out.
Interia reel belts are there as a bare minimum for lazy people, don't even consider them for your build. One company, Bimmer, Saab or Volvo if I remember, even has an explosive device to tighten them up on impact.
Locost has the barest minimum protection as it is without compromising on belts.
the pyrotecnic tensioners have been used for about 25 years now, i've seen them as original equipment on mercedes from the mid eighties.
if you think that the seat belt is going to save your life in an accident severe enough to need to be held in place by it you are mistaken, all it will do is trap you in the car which will crumple around you, in a locost, you must view them the same as windshields, something a beaurocrat has determined that you have to have to get registration.
this is not meant to bad mouth seat belts or beaurocrats, it's meant to make you more aware of the vulnerability of the locost user, look at f1, to save the driver there is a lot of absorbtion materials all around him, in a locost there's a few bits of tube and aluminum, make no mistakes, in a left side impact you are the passinger's crumple zone and visa versa.
use your seat belt by all means, anything is probably better than nothing, speaking as a person trapped in a car in a head on collision because the seat detatched from the floor and the seat belt catch was now under the seat where it could not be reached, the only thing that kept me in that car was the top of the windshield which dug into my head, we are back to the old addage of if i'm not wearing a seat belt, i would have been thrown clear.
all i'm saying is in a locost it's the same as a bike but with tubes and things waiting to pearce your body, you should, if you use due care, never have to find out how good or bad your seat belt works.
_________________ this story shall the good man teach his son, and chrispin chrispian shall ne'er go by, from this day to the end of the world. but we in it shall be remembered.
Joined: November 13, 2009, 8:43 pm Posts: 505 Location: Sunnyvale, CA
I was browsing through Autoblog and they had a link to a video review of the Morgan Three-Wheeler. It's a fairly similar vehicle to Locosts, sort of. Anyway, it's got center mounted seatbelts, too.
knowing Peter Morgan, they are attached where they are because there was something to bolt them to at that point in the chassis.
that S&S motor is fine but somehow doesn't have the charm of the J.A.Prestwich lump they used in the originals, copper tubing and brass fitting etc.
_________________ this story shall the good man teach his son, and chrispin chrispian shall ne'er go by, from this day to the end of the world. but we in it shall be remembered.
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