Nut coming off Petzl Stop

[paul]

There's a report on ukCaving.com that a caver's Stop fell apart in their hand luckily while still at the beginning a rappel before attaching it to the rope.

It appears that one of the nuts holding on the sideplate had loosened and fell off.

Has anybody else heard of this happening?

[NZcaver]

There's a report on ukCaving.com that a caver's Stop fell apart in their hand luckily while still at the beginning a rappel before attaching it to the rope.

It appears that one of the nuts holding on the sideplate had loosened and fell off.

Has anybody else heard of this happening?

Nope, haven't heard of that before. Thanks for sharing - interesting thread. Scary!

I just dived into my bag and grabbed the Stop I have with me. The bolt and nut seem good and tight, like every other time I've checked them. But I'm not in the habit of cranking on the nut, taking it apart, and putting it back together again. Plus I don't have any Loctite handy.

I tend to concur with some of the posts on the ukCaving forum. Somehow that Stop might have either been disassembled and put together again, suffered a significant drop, or been used as a hammer. Any of which could have cracked the Loctite seal, and started the loosening process.

Hank - any comments?

[mgala]

I've seen such situation couple of times, but after replacing the wheels. Simply the nut was screwed too weak. That's why I'm always checking lower nut before descending. For inexperienced cavers we recommend in Poland additional device - shunt - above descender.

[ian mckenzie]

Have seen it once, on a Stop where no parts had been changed. The thing just came apart in the caver's hands.

I've changed my own spool, but have had no problems with the nut.

[paul]

I've seen such situation couple of times, but after replacing the wheels. Simply the nut was screwed too weak. That's why I'm always checking lower nut before descending. For inexperienced cavers we recommend in Poland additional device - shunt - above descender.

Isn't that a bit tricky with a Stop? One hand to hold the lever in, one hand to hold and control the rope beneath and another hand (!) to hold the Shunt!

[caverdoc]

He was referring to using a Basic/Simple with beginners. I still use a shunt when I rappel with mine.
Doc K

[NZcaver]

He was referring to using a Basic/Simple with beginners. I still use a shunt when I rappel with mine.
Doc K

So Doc, do you use a French Wrap type of shunt below the bobbin, or something above it? Just curious - all my bobbins are either autostops or CRDs.

The mysterious 'third hand' also crossed my mind when mgala mentioned using a separate shunt. It would be interesting to find out if losing that nut while on rope is indeed fail-safe, as one of the ukCaving forum people suggested. It could well be, as the sideplates should still be held together in 3 places - the attachment point at the bottom, the nut on the upper bollard, and the post right at the top. I suspect that as long as the lower bobbin bolt doesn't work itself loose, vibrate towards the back, and deprive the front plate of it's pivot point - you should be fine (other than crapping yourself, of course!)

[mgala]

I said we suggest to use shunt for beginners. I don't use it.

if you descend with shunt, you keep i over descender. it's easier (you don't hang on the rebelay) and safer (double fix) to pass the rebelay with shunt and simple.

you are also safer when the anchor above you (descend out of control) or below you (destroyed bobbin) will break.

...and if you have some problems with your nuts ;)

[caverdoc]

So Doc, do you use a French Wrap type of shunt below the bobbin, or something above it?

I use a Petzl shunt above the non-handled Petzl Simple. I have one descender that is worn into a wide groove on 11mm rope and another that I use on 8mm/9mm lines. I also like the Petzl stop, the Anthron, and the SRT stop descenders. Lately I mostly use a BMS Micro Rack with no safety. I'm going to have to experiment in my rigged maple tree out back to decide if the French Wrap is something to use on a regular basis. Back in the '70s I used a carabiner/Gibbs safety shunt above a Bluewater rack, seemed extra complicated...
Dr K

[hank moon]

Hank - any comments?

This is the first I've heard of it happening. Be interesting to know the batch code and/or purchase date of the device in question. The lower bobbin on the current STOP is fastened to the body by a bolt screwed into a ~20mm-long threaded sleeve that forms the axle, and the bolt is secured with Loctite.

More later after I've had a chance to look into it. Some of the older models may use a different fastening method.

[paul]

I said we suggest to use shunt for beginners. I don't use it.

if you descend with shunt, you keep i over descender. it's easier (you don't hang on the rebelay) and safer (double fix) to pass the rebelay with shunt and simple.

you are also safer when the anchor above you (descend out of control) or below you (destroyed bobbin) will break.

...and if you have some problems with your nuts ;)

Ok - I see - I thought you were referring to a Stop as opposed to a Simple (the non-Autostop variety).

[hank moon]

Below are links to some pictures of the STOP.


THIS ONE is a list of parts (not complete) showing the threaded sleeve and bolt that hold the lower bobbin in place. Takes 14-15 complete rotations (360°) of the sleeve to remove it from the bolt when installed on the STOP. The post on the UK forum mentioned that the sleeve only had "3 or 4" threads engaged. Below is a link to 3 views of the STOP with only 3 or 4 threads engaged.

http://home.comcast.net/~onkaluna/STOP/3_views.jpg

[NZcaver]

Below are links to some pictures of the STOP...

Thanks, Hank!

That's certainly no ordinary nut and bolt on the Stop. This does beg the question - what the heck was the original poster on the ukCaving forum talking about?
I can't see how the incident could have happened, the way he described it.

[ian mckenzie]

hm, wait a minute...

[NZcaver]

Well that's obviously a redesigned axle, probably in response to the rare self-disassembies described above. My Stop is over 20 years old and has a regular-type, and rather thin, nut on the end of the bolt. There is slightly less than one thread showing above the nut, which itself probably conceals only a few turns. Top spool is attached similarly. So, the ukCaving reference makes sense. The Stop that I'd seen come apart was perhaps ten years ago.

(EDIT - ***IAN HAS RETRACTED THIS DESCRIPTION - SEE HIS NEXT POST***)

Interesting. I wish I still had my old Stop to pull apart and check (it was about 15-20 years old). Unfortunately I 'recycled' that one, and the newer ones I have appear to contain threaded sleeves like Hank described.

That original post on the ukCaving forum states -

One Stop; irregularly used for the past five years. Checked often. Never had bobbins replaced nor springs. The thing decided to part company of itself in as much as the retaining nut came away from the bolt (lower bobbin section)!!

To me, this statement implies that this particular Stop is about 5 years old - in which case it would use the threaded sleeve design. However, if it was acquired after being used by someone else - perhaps not.

I hate to give up any piece of gear as much as the next guy, but I wonder if there comes a time when you should just retire that obsolete item? Equipment designs usually change for a reason...