Mechanical Advantage: Pulley System Principles

A note about the size of the pulley sheave & it's effect on efficiency: A larger ratio between the sheave diameter vs. the rope diameter will increase rope strength, but does not necessarily, nor directly affect the pulley efficiency. What affects the pulley efficiency are two things:
1. The coefficient of friction between the bearings/bushing and the axle
2. The difference in diameters between the outer pulley wheel vs. the pulley axle. All things being equal, the smaller the axle, the bigger the diameter difference & thus a more efficient pulley due to better leverage ratios. You can also do this by increasing the size of the sheave of the pulley, so long as your axle remains the same. The net effect of this diameter difference changes the lever length ratio, thus affecting the mechanical advantage.

[@christopherhedquist8236]

Great video. Thanks for posting your videos

[@Propeller_Head]

Thanks for watching!

[@jetseverschuren]

You're correct, surface area doesn't matter for friction. The key here is pressure. Given the same weight/mass, increasing the surface area will also spread that same weight over a larger area, which ends up cancelling out (on the atomic level there's some weird stuff going on, but for day-to-day stuff it's close enough)

[@midnightng]

Given the choice and disregarding any consideration of cost, would you choose the maestro over the clutch?

[@Propeller_Head]

I'm not super passionate about one over the other & there is no such thing as a "one-device quiver" to do it all.... just like "all-season" tires are sort of ok but only in the mid-range of the weather elements. It all depends. Am I choosing it as an item for my personal kit or some other "team" kit? And what do I foresee the majority of application? What is my "mission profile"? For example, fire-based technical rescue teams for the most part, in all reality, will use team-based systems. Therefore I would choose a Maestro hands down all day over a Clutch because there is no "anti-panic" feature that tends to be annoying when operating the device at an anchor (fixed brake/DCD). Plus the release handle is setup to be more ergonomic when operating at the anchor, but less so if using it as a descender. I also find it easier to operate it as an "independent team belay" if needed, vs. the Clutch. On the other hand, the Clutch offers more versatility, as it can be used as either a travelling brake (descender) or as a fixed brake (DCD). And while the Clutch does not have a built-in friction horn like the Maestro, you can always route the rope through a carabiner re-direct to make up for it. Personally I think it would be awesome if the Clutch did not have the anti-panic feature & was more like a Petzl Rig, in size as well. So my personal kit that I keep at my fire-based job I keep an ascending kit with a Petzl Rig in a side pouch on my harness. The Rig is there because it cuts down on size, weight, and does not have an "anti-panic" feature which for me I really like (but for people who don't do this very often then that may be dangerous). The team equipment that we carry consists of a handful of IDs, Maestros, & MPDs. My personal "On-Rope" & Rope Access kit that I have at home I have a Clutch. Clutches are hands down my favorite for on-rope work, albeit they are HEAVY, so I would not be taking it anywhere that would require me to hike or travel on foot a significant distance.

[@midnightng]

@@Propeller_Head Awesome, I very much appreciate the time and thought you put into things. Haven't had the opportunity to use a Maestro but you've piqued my interest in it. At my department, we basically use the clutch exclusively, unless someone has their own kit along with them, there are some who do. Lots of petzl rigs and the like. Situation normal - we have more than enough FD clutches and gear to accomplish nearly anything, within reason. That being said, if our one and only heavy rescue is not available (distinct possibility given the breadth of their responses) we will not have access to our long lines or vortex, amongst other things. Additionally, generally speaking, our best and most experienced rope techs are assigned to the rescue, thus taking them out of play also. Therefore, I frequently try to train in a manner that forces us to solve problems as a Squad company with limited (rope tech) help and equipment. That leaves us with only 2 clutches. An eye opener when setting up a high line, for example. Anyway, thank you for sharing your knowledge. Your explanations are outstanding and immensely helpful, even for a simpleton, like myself.

[@Propeller_Head]

Right on, thanks. Yea I guess if you wanted one device to do it all relatively well, then the Clutch is it. But if money is no object..... I'll take them both please

[@resq76]

Bob send me an address... I'm sending you a new T-shirt. 😅 Seriously give me your address I'm going to send you a t-shirt you can wear in your next video!

[@Propeller_Head]

Is this because of the rip on the back of my shirt in the video & you feel sorry for me? Or is it for promoting purposes?, because I have to be careful about promoting/advertising, as my channel needs to be as unbiased & neutral as I can possibly make it.

[@resq76]

Just giving you a hard time about the rip. Love the videos. I was going to send you a union shirt from our department.

[@meganafurman198]

😂