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does anybody know or has any manufacturer measured how much force is effective on each riser on an average slider up, slider down and slider off base jump?

I was reading some interesting data from test jumps done on a military skydiving system a few years ago that was really interesting, in that on some jumps, with asymmetrical loading with one riser getting 60 to 80% of the load. Typical opening shocks averaged about 4.5 g's, with a typical scatter of 1.5 g avbout the mean. (ie between 3 and 6 G average). However now and then, a shock of up to 9.0 G's would be encountered.

Again, this is skydiving data and not that recent, so technology has changed.

if you ask me, its not a very relavent question. the differences would be soooo scattered, there would be no point in doing the research. PCA would probably be about a total of 1.5G accumulative, and i would guess it would be fairly evenly distributed between the 4 risers.

on a 3.5 sec delay, i would guess upwards of 8 or 10G. probably leaning more toward the front risers.

on a slider up terminal, i would say an average of 6G, evenly distributed front and rear.

but i dont know much about this.

damnit. now i want to test it. I have a load cell i use for rope hucks, maybe i should go to the potato with some super modified risers....

the reason why i would like to know these numbers is that i am planning to set up a rope jump (with tyrolean traverse - unfortunatelly it is not possible to swing alot so it is more or less a vertical drop) which should allow 50 m freefall or even more - we just started to calculate the system...

...i wonder if the rope-jump can also be done with a skydiving-rig instead of the climbing harness and how much load will then be acceptable to not harm your body.

Are you talking about this?: http://www.pcprg.com/

ahh.... i see.

we have used BASE harnesses for rope jumps, i think they are stronger than rock climbing harnesses.

weird attatchments though, and ropes will always hinder the exit trajectory and body position to an extent. but thats cool.

what about whiplash when you used base harnesses? did it hurt? (newbie question: does basejumping hurt (alot) when the canopy opens?)


how did you attach the rig with the jumping rope and where did you attach the backup rope - maybe you have got pictures of that?


i thougt it maybe helpful to use some rubber bands somewhere on the system which hold the jumping-rope back untill you need it. what do you think?

PS: i apologize for my poor english

No, that's not it. This was some testing done by Irvin Parachutes for the Cdn. military on a haho ramair system.

no pictures, that was a while ago. i could draw a diagram though.

we wore the harness over a sit harness, the riser release was used to transfer directly to a rappel device.

reserve rope was tied into the climbing harness.

that is what i would have planned.

but i am not sure yet how to connect the jumprope to the risers...?

PS: would be cool if you had the time to draw a diagram

I used Vertigos risers, but i would strongly recomend Asylums risers, they are stronger.

Attatch large french links to the riser ends where they would be on the lines, larger even than BASE links, then with the risers folded up through the shoulders, lay them down your back, and attatch ALL 4 riseres to the rope. a simple figure 8 knot on the rope end should be good, its what we used.

while jumping, useing a break away rubber band to hold the rope on your lower back at the CG of your body will mostly stop rope drag interferance, and be sure to jump with the rope at your back.

Can you explain what leads you to conclude this?

I prefer Asylum risers personally, but not for strength reasons. I'm unaware of any substantial difference in the structural strength of the two. But, I'm pretty sure that you've got to be hitting the risers harder than most BASE jumps, so it's likely you've done more research than I have on this.

Thanks!

whats the tensile on the links? perhaps locking biners may be a better solution?

the stats say that steel screw links one 'size' bigger than the Norm BASE links have a stronger breaking force than all aluminum carabiners.

also, carabiners made for climbing are bulky, and awkward.

most steel links that are above 3mm have a breaking strength of above 6,000 lbs. links also lock closed, and are pretty much cross-load proof.

most aluminum carabiners, EVEN locking ones (in annoys me that even a lot of climbers think that a locking carabiner is stronger than a non locker)
ok, most aluminum biners can hold between 4000 and 6000 lbs. they cross load easily, they are bulky.

fair enouh.. didnt consider cross-loading.

I would say the forces are about the same for rope jumps and slider off base hops.

Asylum risers have no hole through them for the 3 ring string. why all risers for BASE are not like this amazes me.

When one disects most risers, they find that there is not a hole 'cut' in the riser for the grommet, but the load bearing fibers are spread, and the cordwise fibers are cut to allow this grommet.

this does however weaken the riser, probably not noticably, but it would matter.

If one understands how woven textiles break under tensile load, they can understand how pushing the load bearing fibers asside can be bad for the strength of a webbing peice.



in all reallity, it doesnt matter. i just like the idea of asylums risers.

why ouldnt you just tie in to the risers themselves...?

I have risers from Apex, Morpheus and Asylum that are all built like this.

With a tensile strength of 4000 LBS, I doubt it.

I have a newer set of Morpheus' and they are built the skydiving way (hole in the webbing), not that it realy matters to me.

However when I bulid them I go integrity because they are easier to make.

i worded that wrong.

it would matter splitting hairs, but at 4000 lbs, your right.

you could, butfabric on fabric can be very good, and it can be very bad. knots (figure 8s) that are being dynamicaly loaded do not stay in the same shape, the loop that would be through the risers would slide very slightly back and forth.

Soft links do not 'sway', and they are a very soft, smooth fabric. kernmantle sheath on webbing might get ugly.

protect the rope and the risers maybe?

on our systems we sheath or double sheath everything in the final system.

IE webbing over the knotted end of the rope,
we also use thimbals on tyroleans.

Morpheus will build them either way. You just have to tell them what you want when you order them.

what would is the purpose in having ring side up? why put a useless hole in your risers? I know why skydivers have them, but in BASE? no holes in my risers please.

I prefer no hole in my risers.

However, one argument in favor of the hole is that it's easier to gear check at exit (because the rings are exposed). Another is that new jumpers who are used to skydiving gear are more likely to be familiar with it.

The hole doesn't weaken the riser enough to matter in most applications (at least not with a type 8 riser). I think there's a post somewhere in the Gear and Rigging forum in which Bill Booth gives the whole history and explanation on the reversed risers (which were first developed by PdF as an alternative to type 17's with a hole in them, if I recall correctly).

(sic)

reversed/integrity risers have a lower overall leverage ratio than standard risers

mini-rings are quite common on base risers now, the thinking behind that has been for compatibilty with most skydiving gear, to encourage you to skydive your base canopy first

mini-rings have a lower overall leverage ratio than standard 3-rings

the most common failure mode for type 8 risers would be pull-through of the yellow cable

the force on the riser that is required for this failure mode is the force required to pull the yellow cable through the grommet multiplied by the overall leverage ratio

the force required to pull the yellow cable through the grommet is the same for standard or intergrity risers, but, as stated the leverage ratios are different and range from something like 12:1 to over 30:1

so if you are on the bigger side (think 200lbs ungeared) with mini rings and integrity risers, according to some numbers seen in deployment tests (6G peak load during deployment) and then in riser failure testing, IF you had that 6G peak force all on one side's risers (severly assymetrical and very hard deployment), you are very close to the force needed to pull the yellow cable through the grommet or you are exceeding it

that is where standard risers with mini rings would take more load before pull-through than integrity risers, this happens before they break, even with a hole and grommet through the riser



as above, it allows you a better leverage ratio and only affects a failure mode that is not the first to occur IF you have mini 3-rings...


in skydiving yellow cable pull through is a perfectly acceptable failure mode, in fact I would prefer it to a riser breaking. in skydiving riser failure is preferably to injury or harness damage or failure.

in BASE your body should fail before your risers or harness does



this is a valid statement if you are under 200lbs, or you have large 3-rings

there is a lot of research published on this, just look around