mini 3-rings on a full sized 3-ring system

[scottherbert 0]

Has anyone ever used mini 3-ring risers on a standard sized 3-ring harness? Just curious... Does it work?

[DBCOOPER 5]

Yes and yes.

Replying to: Re: Stall On Jump Run Emergency Procedure? by billvon

If the plane is unrecoverable then exiting is a very very good idea.

[skydiverek 63]

Keep in mind that the mechanical advantage will be lower. From the 3-ring inventor:

http://www.dropzone.com/cgi-bin/forum/gforum.cgi?post=124861;search_string=mechanical%20advantage;#124861

http://www.dropzone.com/cgi-bin/forum/gforum.cgi?post=1898947;search_string=mechanical%20advantage;#1898947

[pchapman 279]

To expand on skydiverek's links, for the OP:

Bill Booth says that the mechanical advantage of a small ring riser will be less with the large harness ring, than it would be for a small harness ring (because the latter is not quite as thick). But that it is OK as long as everything is built properly.

In any case, while there are variations in how good various combinations of rings and riser designs are, having small riser rings on a large harness ring is "completely normal" and not considered incorrect.

[base283 0]

scottherbert

Has anyone ever used mini 3-ring risers on a standard sized 3-ring harness? Just curious... Does it work?

Sorry, I have to answer this with sarcasm.
NO, No one has ever done that so that precludes your 2nd question making it obsolete.;-)
Take care,
space.

[riggerrob 643]

Harness ring thickness makes a big difference when you are comparing RW-7 and RW-8, but a tiny difference when you are comparing RW-8 and RW-10 harness rings.

[pchapman 279]

Well that challenged me to actually check some numbers. Using a micrometer I measured the front to back diameter of the top of three different harness rings. These aren't original engineering numbers, but just one person's measurements of rigs in service:

RW-1 a standard big harness ring
6.87mm (.270")

RW-8 a standard mini harness ring
6.04mm (.238")

RW-7 the 'thin' mini harness ring, installed until maybe the mid 1990s but no later (As it was then considered to be too rough on risers due to its thin diameter -cheese cutter effect.. or at least that's what I heard. Still acceptable to use but a little frowned on I think.)
5.25mm (.207")

Anyway, that puts the RW-8 mini ring as being 12% thinner than the RW-1 big ring. Not a huge difference but not negligible. How that actually affect 3-ring cutaway forces is going to be a more complex calculation based on geometry of the rings and the stretchable webbing.

[edit] How does the RW-10 big harness ring that's sold now, compare to the traditional RW-1 big harness ring? It isn't clear, between ParaGear, Poynter's, and the Parachute Rigger Handbook.

[riggerrob 643]

RW-1 and RW-10 look to be the same thickness ... at arm's length. The next step is to measure them with micrometers.

RW-1 was introduced in 1981 ... is rated for 3,000 pounds and was the first slotted harness ring.

RW-10 looks the same at arm's length. You can only tell the difference when you look closely at the fillet where the slot meets the ring. Because they are full thickness through the fillet, RW-10 are rated for 5,000 pounds which makes them strong enough for tandems and military freefallers who like to jump with rucksack, rifle and snowshoes. ... the sort of military-freefallers who think 100 pound rucksacks are for sissies.