This video shows a 195 lb. weight being dropped 3.3' on to a toothed ascender attached to an "arborist rope", no specs given for the rope or ascender.
Toothed ascender drop test

Rope appears to be shredded, looks like the ascender slid 10-12 ft. before it stopped moving, rope did not completely sever, held the weight.
-AJ

Scary video. I once dropped roughly three feet on SRT when an unseen sucker limb broke above me and dropped my anchor down to the big limb I'd originally thought it was over. There was no apparent damage to my rope (Bandit), the ascender (Petzl), my trusty NT saddle, or me -- of course I only weigh 146 pounds soaking wet...! I once saw ol' Joe of the Jungle take a five-foot drop in a similar situation with a Jumar ascender without any apparent damage.

I'm guessing that the brand of ascender, particularly the number of teeth and thier length and sharpness, might have something to do with the shredding of the rope. Could the diameter of the rope have an effect?

My understanding is that toothed ascenders were originally designed for kernmantle ropes where the core is the primary strength of the rope, the cover is for protection against abrasion. When a toothed ascender is shock loaded on a kernmatle it tears the cover but the the accident is theoretically survivable because the core remains intact. Guessing that as the cover is being stripped it also provides some shock absorption for the climber.

In arborist ropes (depending on the construction mileage varies) the exterior of the rope is part of the overall strength of the rope. This is why toothed ascenders are considered more problematic in a shock load situation on arborist ropes.

The discussion came up here on the Buzzboard in response to a TCIA magazine article on SRT.
-AJ

I would rather be on a thicker than a thinner arborist rope if that happened. With a static kernmantle rope thickness is probably less of a factor (to a point) since the core/cover should should behave similarly in response to a toothed ascender whether the rope is 11mm or 10mm.
-AJ

It looked like a very soft landing--that's the good news.

It looks like the main rope is anchored on the limb about 6 ft. above the ascender, which would mean we're looking at a fall factor of about 0.3. On a static rope this would probably seem very severe. Stripping the cover might actually be the least bad thing in this situation.

Unless the core breaks, too. Has anyone heard of this happening?

Said in the video caption that the weight dropped 3.3' before the force of the fall hit the ascender.

I think the core survival concept is invalid for a double braid arborist rope since the core and cover each share half the load. For example if the ascender destroys the outer braid the strength of the rope is halved.

With a kernmantle static like NE Ropes KMIII or Sterling HTP the rope should theoretically maintain close to full strength with the cover destroyed

Would be useful to do ascender load testing on various types of arborist rope:
16 strand 1/2" like Safety Blue etc.
11mm double braids like Bandit, Blaze, Velocity etc.
11mm+ double braids like Tachyon, Poison Ivy etc.
NE Ropes Fly is an odd one because it is apparently a kernmantle according to published descriptions, guessing the cover does share the load.
-AJ

As we've discussed before, to get a fall factor to force an ascender to completely sever a double braid the climber's body is probably going to suffer serious damage.

I think the main point is be smart about assessing a ground anchored SRT setting no matter what rope or toothed ascender you use.

I know I've shaved it too close on more than one occasion, requires discipline per climb to avoid the temptation or self-imposed pressure to climb on a less than great setting. By self-imposed pressure I mean the following scenario which may be familiar to many climbers:

1. You are lead climber and are setting the initial acess rope.
2. After a number of throws you're not getting the bag where you want it
3. Climbers are sitting around for a long time
4. You finally get a setting but have some doubts
5. You climb it anyway because the sun sets eventually
6. Half way up you can now see clearly where the rope is. It makes you very unhappy as you realize the climb to that point was very risky

In other situation I was criticized by a very experienced climber for taking too much time to create a solid setting. Many experienced climbers accept that some limbs may or will break out while they're ascending. If that happens it can be no problem or a big problem.
-AJ

Those six factors you listed can be real temptations.. It seems almost as if it's safer to do things we wouldn't normally do when it starts getting dark. Interesting how the mind works.

As I've said many times, our motto has to be "Don't fall!". We don't have fall protection gear in place when climbing and the video more than demonstrates how little it takes to strip a cover on an arborist rope. Although, I have to say, I believe my 11mm EzBend would fair better than the rope used.

While the load eventually stopped, that doesn't mean it will everytime. It could strip the cover all the way to the ground.

Another consideration in a fall is what you're going to hit on the way down - like tree limbs. That may cause more severe injuries than a clean fall and soft stop as shown in the video. Also, we may not be on such a substantial limb (anchor) and the force of a fall could break the limb and then we would not only free fall, but have a limb coming down on top of us.

Brrrr, no wonder I stay tied in twice at all times.

Since it's a true kernmantle it most certainly would, just as long as the shock load didn't exceed the strength of the core.
-AJ