Interestingly, they do! Sort of. The non-replaceable ‘friction zones’ (lower cam which is not quite a spool) of the Stop, an ‘auto-stop’ device similar to the Simple in many respects, are made of stainless steel. Petzl specifically advertises the increased durability of the Stop, “Stainless steel friction zones make it a durable tool for all your excursions!” The Stop has its proponents and detractors, but it is a significantly more costly device with features that not everyone desires.

My suspicion is that, where the Simple is concerned, it is financial rather than practical decision. Stainless is somewhat expensive raw material compared with 6061 aluminum, and much more costly and time consuming to machine into finished parts. Most people buying the Simple are attracted to its light weight and low cost, neither of which are helped by the addition of steel. This is a niche product, to be sure, but at least those few of you who are willing to sacrifice a few grams and a few dollars for a smooth ride and a longer lasting device have options. Options are good.

I suppose the best answer to this is ‘no’, in the sense that these spools are designed for the purpose of rappelling/descending/abseiling which is not a particularly ‘safe’ activity. Consider that the EN 15151-2 and UIAA 129 standards to which the Simple conforms contain no stipulations on how much friction a device must be able supply—that is up to you.

If your experience is anything like mine, it results in a desire for a smoother device. I like using the Simple, but I prefer the ride of the Micro Rack. This is something of a happy medium. I find that, whereas before I C-rigged almost every drop (especially when using a Freino), now I can usually get away with an S-rigged device.

I also find that I have less occasion to remove the rope from the braking carabiner in order to reduce friction, which one could argue is actually safer! That said, I am a fan of the Raumer Handy. I’ve used just about every permutation of braking carabiner and, though I like the streamlined nature Freino-Z, I like the Handy best. That’s what I reccomend.

It is also worth noting that none of the original Petzl critical hardware is replaced (i.e. the bolts that secure the spools). The ultimate static strength of the device is unaffected by replacing the spools.

I don’t know. Seeing as they do make pulleys I would think they would call them something else. Definitely not sheaves. Capstans? Some folks prefer ‘wheels’. Bobbins also works, but somehow has come to mean the device as a whole and is therefore confusing. So far as I can tell, ‘spool’ is the closest thing to ‘correct’, at least in English. If it’s good enough for the authors of Alpine Caving Techniques, it’s good enough for me. If you want to call them pulleys, I won’t make fun of you!

I bring this up mostly because I have talked with people—generally people who don’t regularly/ever use a bobbin style device, who think that the spools rotate like pulleys and are therefore suspicious of them.

I’d argue that the stainless spools especially, are pretty good value. In the final analysis, the prices reflected here are just what makes sense to me. There is a lot that goes into these things; bulk material orders, tooling, shop overhead, web hosting, shipping, testing, machining, deburring and polishing, engraving, emails and phone calls, insurance, etc. Considering that the value proposition is quite a bit better than the product they replace, I think the price is reasonable. That said, I do wish I could sell them for less, but at this volume, that’s not likely to happen. If you feel that the price is outrageous, it’s ok. Remember that no one is forcing you to buy them. If you really want one, but honestly can’t afford it, shoot me an email—I sometimes have perfectly functional seconds, I’m sure we can figure something out.

We want space metal! I did make a couple test pieces with some Grade 5 (Ti-6Al-4V). Despite its many astounding properties (and cachet), it isn’t ideally suited for this application. Ask your friendly neighborhood tribologist! It is ludicrously expensive (compared with 7075 and 316) and despite its relatively high hardness, does not have particularly good wear characteristics in this application. The samples didn’t have the smooth feel of 316 and were heavier and much more expensive than 7075. It’s also kind of a pain to work with. In total; just not worth the squeeze.

That said, if you must have a Ti spool and cost is no object, get in touch—I still have some material. For everyone else, the 7075 aluminum spools are a great choice if weight is a concern.

I do! Despite that, these spools don’t have a tendency to glaze ropes.

Aluminum is a pretty amazing material. Compared to stainless steel it is much less dense and has some very desirable thermal characteristics. These are great fits with the goals of a descender so it is no surprise that so many are made of it or use it in their design. Stainless steel, specifically 316 has some desirable properties as well. It is much more resistant to abrasion than aluminum, resists corrosion and has a lower coefficient of friction with many rope materials.

The whole point of descending on rope is to control the rate at which we convert our potential energy (at the top of the pitch) to kinetic energy (during the descent) and dissipate this energy as heat from friction. In order to reach the bottom of the pitch all of this energy must be converted and what we control is the rate at which this conversion takes place. All descenders trade deceleration for heat. How you spend this heat budget is up to you. The slower you descend, the more time your descender has to dissipate heat relative to how much heat is generated through slowing your descent. The above might be obvious to some of you, but it’s worth pointing out. There are a ton of variables we encounter while descending that affect the system. The load (mass), the composition and conductivity of the rope, its moisture content, the ambient temperature and conditions, the many particulars of the descender, and so on. It is nothing short of a testimony to human capability that we are able to process all these variables in real time and control the outcome by moving one hand around a little.

It is yet another case of ‘horses for courses’. It is pretty rare to use the Simple for pitches exceeding 100m. The alpine rigging where it is most at home tends to break up long pitches and for this use case, the Simple is very well suited. If you’re headed to Bridge Day, it is not the descender to bring. If you want to descend long, uninterrupted pitches at high speeds, it is not ideal. If you’re using the Simple as intended, you should not have any issues. If you do, you should slow down and/or change devices. If you remain concerned, please reach out.

You should follow the instructions from Petzl. The ‘glue’ is assumed to be a thread-locking compound—they mention this in some of their other manuals. They do not specify a brand/formulation but LOCTITE® 242 (blue, medium strength) is the usual choice. There are less aggressive formulations more suitable to disassembly with hand tools. The HFT #42 threadlocker from Harbor Freight is a very cost effective alternative.

HowNOT2.com also have a video demonstrating spool replacement. We recommend an aluminum spool in the upper position, though. Likewise, the venerable Derek Bristol demonstrates spool replacement on pre-2019 devices in his video on Bobbin-style descenders, an instant classic. Both bolts and then both nuts should be tightened to 20Nm.

The hex nuts and bolts have 13mm heads (pre-2019 use 13 and 14mm) and can be removed/replaced with socket integrated into the handle of Petzl’s Tam Tam hammer. Pretty neat.