Silent Partner Top-roping (and rappel)

Aric Datesman wrote:As I mentioned above, it locks based on changes in rotational velocity of the drum.

Heck, the point is that I really could not get that part at first. :P

So, if I got it right now, it's not about its absolute speed, but rather its acceleration. Right?

Bingo.

EDIT: it occurs to me now that I should have just pointed out it works the same as a seatbelt. Oops. :)

Aric Datesman wrote:Bingo.

Ugh. Theoretically that means that if I keep gaining speed very gradually it would keep rolling even after a while and going quite fast, then.

I guess I'll have to experiment a massive lot with that, I just have to realize *where*. I have an anchor on my ceiling but I cant get up that much with that. :P

Yup. Fortunately it'll only get so far before the clove starts binding on itself, but yeah, that might be longer than you'd like.

Personally, I use an Eddy for lead solo and Minitrax for TR solo.

Aric Datesman wrote:Yup. Fortunately it'll only get so far before the clove starts binding on itself, but yeah, that might be longer than you'd like. Personally, I use an Eddy for lead solo and Minitrax for TR solo.

I can easily see why you use the Minitrax for TR (I do as well and I think I'll back it up with a Petzl Microcender rather than alpine butterfly knots).
But, why do you prefer the Eddy for lead solo over the SP? I'd really like to know. The SP is boasted everywhere as the best tool for that job - and it's among the few specifically designed for that purpose.
Afaik, the Eddy is not, so I'd really love to know the reason of your preference if you'd like to share it.

BTW, Rock Exotica states about the SP that " its speed sensitive locking mechanism will catch even head first falls".
I guess it's inaccurate then, being actually the lock not speed, but acceleration dependant.

Semantics, but when an object is traveling in a circular path around a fixed point at a constant rpm it is in fact accelerating toward that fixed point. We (or a locking pin) experience this acceleration as a perceived force (ie commonly called centrifugal force). I haven't seen a blueprint for the device but I always assumed this is what was meant by 'acceleration dependant' because this is how an engineer would describe 'centrigual force'.

In other words, if one were to take a slowly accelerating fall on a slab, the device would still lock up once he reached a certain velocity.

jon apprill wrote:Semantics, but (snip)

John, I'm afraid it's not semantics. It's angular acceleration. As in radians per second squared, which has nothing to do with centripetal force or how the device locks. The rollers are free to lag or overrun with respect to the drum and locking ramps, and do so as a result of changes in angular velocity (which is the definition of angular acceleration).

jon apprill wrote:I haven't seen a blueprint for the device (snip)

If you scroll up you'll see a cutaway view of the device, which should make it clear how the device functions.

Febs wrote: I can easily see why you use the Minitrax for TR (I do as well and I think I'll back it up with a Petzl Microcender rather than alpine butterfly knots).

Microcender works nice too, as does the Ushba Basic (the Kong Duck works, but needs much more weight at the bottom to feed smoothly). I really only settled on the Minitrax because I can lock the cam open to rap rather than have to hold or detach the device.

Febs wrote: But, why do you prefer the Eddy for lead solo over the SP?

Well, mostly because I really liked Joe Healey's writeup of his Eddy-based system, tried it, made some tweaks and am now quite comfortable with it. Plus I really didn't want to drop $200 on a SP before I knew I enjoyed lead solo. I still kinda want one since I'm a total gear whore, but it would take a lot for me to move off my current system.

At the time I got into it, the popular option was a Death-mod GriGri1. One of the "features" of the Eddy is that the cam is held in the unlocked position by a spring loaded ball detent, which is fairly easily overcome (moving the cam into the locked position) when the sharp end of the rope comes taut. Joe Healey (correctly, IMO) observed that this allows the rope to run freer in a lead solo application than a GriGri1, an switched over to it.

His system worked quite well for me with a 10.something rope, but I found it to run a bit too free with a dry treated 9.8 so made some tweaks. Namely, I now not only flake the rope into a backpack and run it over my shoulder, but I also have it running through an old-school oval biner rigged with a biner brake bar to add friction when paying out more rope. As I move upwards, a quick hand to my shoulder pays out the needed rope, but friction from the brake bar keeps the system from running away since it's more than enough to pop the cam on the Eddy out of the detent and into the locked position.

On a side note, with my 10.2 this was not necessary as the combination of the rope diameter and suppleness was already right on the edge of popping the cam into the locked position the moment the free end came even a little bit tight. It would run a bit with the 9.8, which was a bit unnerving even with the instinctive grab-the-free-end-running-across-my-chest-to-pop-the-cam. So now I use the biner brake bar and only pay out as much rope as is needed every move or three (which has the side advantage of keeping me from getting my feet tangled in it).

Febs wrote: BTW, Rock Exotica states about the SP that " its speed sensitive locking mechanism will catch even head first falls". I guess it's inaccurate then, being actually the lock not speed, but acceleration dependant.

The wording is tricky, especially when you're marketing to people who may or may not understand the nuance between speed and acceleration when applied to rotating bodies. Perhaps I'm being overly pedantic about it, but "speed sensitive" in this scenario is actually referring to changes in speed, which is acceleration.

Aric Datesman wrote: John, I'm afraid it's not semantics. It's angular acceleration. As in radians per second squared, which has nothing to do with centripetal force or how the device locks. The rollers are free to lag or overrun with respect to the drum and locking ramps, and do so as a result of changes in angular velocity (which is the definition of angular acceleration). If you scroll up you'll see a cutaway view of the device, which should make it clear how the device functions.

Yes you're right, I see it now. It's all about acceleration. When I go solo rock climbing on Mars I'll be sure and bring a different device :-)

Interesting.... It wouldn't work on the moon, would it? Angular acceleration of the drum due to the linear acceleration of the climber wouldn't be enough to cause it to lock! No wonder it took Blanchard and eKat so many years to work out! Quite the balancing act with the springs, and probably why it's so hard to find other examples of bidirectional roller clutches.

(Seriously, thanks for pointing out the Mars thing... I had assumed it would be gravity independent, but clearly not. Which in turn explains slow lockup in sliding falls. Fascinating. :) )

Academic at this point, Jon, but my reading of the patent has the spring biasing the roller outwards against the drum, and rolling friction is what causes them to move outwards on the locking ramps.

But yeah, low gravity = low linear acceleration = low angular acceleration = no locking until the clove bites. The more I think about this, the more impressed I am with Blanchard and eKat. Seriously cool stuff going on with this, to the point if you do a Google search for "bidirectional roller clutch" you'll get *nothing*. Partly because there's no industrial application, and partly because it's that hard a thing to actually get to work.

On a side note, Blanchard sold off the design ages ago and dove into building guitars. Never seen one in person, but I hear they're amazing. Like the SP, best info to be had on the subject is on ST. Haven't seen Blanchard there in a long while, but eKat is there daily and drops pics of some of his work every now and again.

Which reminds me of the other thing I wanted to mention, Febs.... You're right; aside from the SP there's practically nothing out there that's approved for lead solo climbing. Reason for this is that it's a very small niche market with an insanely high liability insurance cost associated with it, so manufacturers are loathe to enter the market.

Case in point, a friend of mine developed something he calls The Guardian a decade or so ago, ran through a bunch of prototypes and hundreds of pitches, and then shopped it around. No one would touch it even though they loved it and it works better than anything else out there. Flat out told him the liability costs were too high for rope solo devices and not enough sales volume to offset it. I have a set of blueprints for it and permission to make a copy for myself, and have to say it's a shame it never made it to market. Lovely design, and stupid simple.

On a side note, I know I keep saying to head to ST for SP advice, but eKat dropped a piece of history today/yesterday (I forget which) regarding them having developed a rope bag for the SP that did away with the loops and knots hanging off the harness. Apparently worked well, but fell by the wayside once they decided to license the design rather than make it themselves. The big pile of loops off the harness was always a turnoff for me, but YMMV.

Also nothing against folks here on MP, but when it comes to advice on using the SP you can't get more authoritative than talking direct to the folks who invented it over on ST.

You all can't realize how much I'm loving this thread. It really makes me wanting to study some basic physics to understand it in its details.

What I have been able to understand despite my lack of physics background, is, johnnyrig's "It won't just keep spinning faster and faster without locking. I tried it. "

I guess it's very hard to do such a test in a totally accurate way - I mean, really accelerating lineary up to "infinite" speed :). But it would make sense if the device would work like that, so that once reached a certain speed (actually angular speed, right?), it would lock anyways despite having reached that speed with a low acceleration. That would make a lot of sense.

I registered to supertopo and I read probably all the posts about the unit. I did not liked the fact that when a user posted a concern about the device, the SP lovers beat him in the knees as if he blasphemed their personal god. I agree that thread had quite a trolling subject ("POTENTIAL DEATH WITH THE SP" ) but its contents where interesting in my opinion.
I will probably post my questions there as well; but I am really loving how informations are gathering here so far, so I will wait - so not to split everything in a confusionary way.

Heading to this link now :) https://www.khanacademy.org/science/physics/torque-angular-momentum/torque-tutorial/v/relationship-between-angular-velocity-and-speed

Febs.... If it dries out this weekend, I will take some vids for you of dropping SP loaded with weights.

Last night I pulled out the gear bin and put accessory cord, the 9.4 and 10.2 through the device. It didn't matter how I pulled the SP as soon I gave it a solid yank it locked up as soon as the slack was gone.

And I tried spinning it to where it wouldn't lock up. The just plain won't happen, the acceleration would immediately lock the drum.

JacksonLandFill wrote:Febs.... If it dries out this weekend, I will take some vids for you of dropping SP loaded with weights.

I love you. :)

Here you go:
youtu.be/w6TIa0gJ0to

Hope it helps. Sorry about the angle, I ended up having to hold the camera while suspending the weights.

For what matters the top rope setup, what REALLY makes me think that the SP could actually be a very effective device for Top Roping is that you commented at the end of the video:

"any fall with the slack removed and the device below the anchor resulted in about a half meter length fall".

It is true as well that in your tests the unit was overhanging in the void while on a sloppy terrain it would accelerate at a slower speed, so I'll want to test that as well (with nice backup knots :P) but your tests are really reassuring so far.

Thank you very much dude. :)

I wanted you to know that I finally received it and it's here all new and shiny.

It's not the most fortunate season to test it, and the following weekends weather forecasts pretty much sucks, but I'll fiddle with it indoor as much as I can. Let's the fun begin.

• gosh*, on the unit itself, there's the usual disclaimer about proper training, climbing is dangerous, and so on.

So far, so good.
But this one:
""this device will not catch any fall", glom.

I guess it's only a kind of a disclaimer. Isn't it? :)

Febs wrote:I wanted you to know that I finally received it and it's here all new and shiny. It's not the most fortunate season to test it, and the following weekends weather forecasts pretty much sucks, but I'll fiddle with it indoor as much as I can. Let's the fun begin. *gosh*, on the unit itself, there's the usual disclaimer about proper training, climbing is dangerous, and so on. So far, so good. But this one: ""this device will not catch any fall", glom. I guess it's only a kind of a disclaimer. Isn't it? :)

Yep

I spent one hour fiddling with the SP and I think I found a nice, very effective way to rappel with it by having full, easy control on the speed while descending.

It worked so well during my test that I really wonder why this is not in the official manual, neither is discussed anywhere on the internet[1].

So, I suspect there could be something wrong in this idea :) and here I am submitting it for a review. :)

What really looked to work well in my test was using an Italian (what else) hitch tied into a small carabiner, that is clipped into a leg loop, below the Silent Partner.

That allowed me, by holding the rope that enters the italian hitch, to rappel to the speed I desired.

I could not test yet if the SP would lock if I leave the hold on the rope for any reason (i.e. I am struck by a rock and I let go).
I did actually tried, but I could not take enough speed for it to lock and my ass gently and slowly reached the floor. There was a very short "room" for the setup to take speed (I tried it only indoor so far); I will also test it at the local kids playground asap and I'll let you know.

Anyway, that is quite secondary overall. What I loved is that I could very easily rappel with it; without unmounting it.

do you see any potential issues with that?

I tried to take a picture of it; this is the best I could do (sorry; that room is very dark). I hope it's clear enough nevertheless.

Setup to rappel with the Silent Partner by controlling the descent speed with ease, while not unmounting the belay device itself. Comments?

[1] as far as I could find.