Measuring Friction / Efficiency?

I was testing my gear again yesterday and the amount of friction in the system really seemed excessive. I don't know if the leather CS was the problem or if the hitch pulley was jamming the Blakes but I wasn't too happy. Maybe the TIP was too large for the leather CS?

In order to be objective when evaluating a system how could a measuring scale be set up on a footloop to actually measure the rope tension? Can you buy 100lb+ spring-type fish scales or something like that? Thanks.

Edit--
Searched and found This...
and This...

I can't answer on friction measuring methods but as far as solving your problem I'd start with the hitch first. Take the hitch advancing pulley out of the equation first and climb on the system. Depending on how a hitch advancing pulley is configured it can cause binding. If the problem still exists then I would look at how tight you set your Blakes. A Blakes set too tight will cause the problem you're describing. I don't think it's the sleeve.

I'm predicting that your hitch is set too tight with the hitch advancing pulley a close second as probable cause.

What diameter and construction rope are you using? Blakes sets tighter on on 12-strand 1/2\" rope than on 16-strand 1/2\" rope. The smoother 11mm ropes (24-strand) often require a tighter set Blakes.

Edit: The other possibility is you set the rope in a tight V crotch which is pinching the rope through the sleeve. A long shot, you would have had trouble setting the sleeve in the crotch if it was that tight.
-moss

Davej wrote:

I was testing my gear again yesterday and the amount of friction in the system really seemed excessive. I don't know if the leather CS was the problem or if the hitch pulley was jamming the Blakes but I wasn't too happy. Maybe the TIP was too large for the leather CS?

In order to be objective when evaluating a system how could a measuring scale be set up on a footloop to actually measure the rope tension? Can you buy 100lb+ spring-type fish scales or something like that? Thanks.

moss wrote:
I can't answer on friction measuring methods but as far as solving your problem I'd start with the hitch first. Take the hitch advancing pulley out of the equation first and climb on the system.

I don't know but the required down-force seemed excessive and disconnecting the pulley didn't really answer the question. It made things easier, but of course it would.

Dave Looks like neither one of those weighting tools have enough capacity for the measurements you like to complete. Talk to Ron at TCC. He teaches Physics and Mechanical Stuff and works in a University Lab that has all kinds of high capacity measuring tools and he has actually done many of those measurements and posted on line at least twice.
You may do a search or ask Bill Maher or Ron to point you in the right direction. Good luck and post you findings( photos ) of the set ups are also nice!

oldtimer wrote:
You may do a search or ask Bill Maher or Ron to point you in the right direction. Good luck and post you findings( photos ) of the set ups are also nice!

Well, I'm going to get one of These...

Since I weigh only about 150 and DdRT ought to reduce that to maybe (150/2)+30=105 (???)

The hitch auto-advance is a mystery to me. Last Fall I tried a sliding plastic widget under the hitch and it didn't work, and now this micro-pulley doesn't seem right. Why not just wrap the silly hitch around a coat hanger wire?

Davej wrote:

I don't know but the required down-force seemed excessive and disconnecting the pulley didn't really answer the question. It made things easier, but of course it would.

Which question are you referring to, how to measure friction or how to solve the problem of excessive friction in your system?

If taking the pulley off reduced the friction then you're part way there. What type of rope are you using and did you try setting the Blakes less tight?

How well the pulley works is dependent on how you're setting it up in your system.

If the hitch is set too tight the pulley or any hitch advancer won't work very well. So you still have several variables to work through to isolate the cause of excessive friction.

Photos of your hitch and pulley hitch advancer setup would be helpful to diagnose the problem.

FYI, I'd dump the hitch advancer for now, it just gets in the way of climbing. It's obviously complicating your system at this point.
-moss

moss wrote:
Which question are you referring to, how to measure friction or how to solve the problem of excessive friction in your system?

Well, if the weather will clear up a little more I'll give it another try later today. Obviously the friction can only come from the hitch or the leather CS. I think the leather CS might not be the best choice if it barely covers the TIP.

moss wrote:
FYI, I'd dump the hitch advancer for now, it just gets in the way of climbing. It's obviously complicating your system at this point.

Stop thinking like that! I'm old and tired, not old and senile.

Davej wrote:

Stop thinking like that! I'm old and tired, not old and senile.

I'm serious, if you're using footloops if you've got the old and tired part covered, and the young and energetic part (at heart). The hitch advancer is way overrated. Keep the bridge nice and short, one hand above one hand below, move the hitch up with the lower hand as you stand on the footloops. Humor me and try it.

Yep, your photo tells the story, lots of friction on the tree. Not a big deal, the sleeve is still reducing friction significantly compared to rope on bark only. More often you're going to be climbing on lesser diameter limbs. We all find ourselves climbing on huge limbs with a too short sleeve, it goes with the territory.

Case in point, \"lower\" limb on huge loblolly around 100 ft. up:


-moss

moss wrote:
FYI, I'd dump the hitch advancer for now, it just gets in the way of climbing.

I'll admit you are right -- I can't get the pulley to work properly for this -- so it is easier going without it. Maybe the pulley works better for closed hitches?

Davej wrote:

I'll admit you are right -- I can't get the pulley to work properly for this -- so it is easier going without it. Maybe the pulley works better for closed hitches?

It's one of those things that seems like a good idea, and is for certain situations and climbing style. I know very few climbers who actually use a hitch advancing pulley on a regular basis.

A hitch advancing pulley isn't needed for a closed hitch, the idea is that the hitch collapses when not under load and just rides on the rope as the climber ascends, then magically grabs the rope when the climber loads it. Takes some adjustment of cord length and hitch configuration to achieve that ideal behavior.

It is confusing though, it is advisable to use a slack tending pulley with a closed hitch, so you can take slack out by pulling the tail away from the climber, useful returning from limb walks and other similar situations. Sometimes people think a slack tender is a hitch advancer, not so.

The hitch advancer is intended for a Blakes, takes some fiddling around to get it to work properly. As mentioned I've never liked using one.
-moss

I did try a bungee cord on the handled ascender (footloop) and I like that -- although I don't have the length adjusted correctly yet.

So how tall is that Loblolly if it has branches like that at 100ft up?

Davej wrote:

I did try a bungee cord on the handled ascender (footloop) and I like that -- although I don't have the length adjusted correctly yet.

So how tall is that Loblolly if it has branches like that at 100ft up?

Didn't measure it but it's in the 140'+ range, it's next to the national champ loblolly which we did measure, it's 169'. I posted a report back in February with links to photos etc.
-moss

I may be way off mark here Dave, but it seems like you are equating friction within the system and climbing efficency. I'm not sure that is going to gain any real efficency (though I'd love to see it studied scientifically). Reducing friction may improve climbing speed, but not necessarially efficency.

I believe that climbing efficency comes from several areas, first a simple system with few moving parts, and second conservation of motion with a preference for use of larger muscle groups. A good example of this is a comparison of climbers during a tree climbing competition. On one tree you may see a climber on a DdRT system with with a self advancing closed hitch system, on another tree you'll see a climber performing a secured footlock. The guy on the DdRT is tugging hard using the upper body, chest, arms, and back, his time for a 40' climb is going to be something like 20-30 seconds, and will look fast. The guy doing secured footlock is going to cover 40' in something like 16 seconds, using only legs, stomach, and shoulders. After performing both of these myself, I've no doubt that the secured footlock is vastly superior from an efficency standpoint (even though I'm not yet very good at it). I'm also sure that I could climb far more on such a system during the span of a day. Would I want to do that during a recreational climb? No way! It's too risky, and no where near as comfortable, plus you'd have to change systems in the tree.

If you are really serious about increasing your climbing performance focus on your biomechanics, and pick one system and keep it consistent, that'll be your control. I'd reccomend video of your climbs, efficency could be defined as vertical gain per pull. From a biomechanic standpoint one can increase this ratio on a DdRT system by fully extending the legs (leg muscles), aligning the long axis of the body with the rope (stomach and back), and fully extending the arms that are advancing the hitch (shoulders). This is the same motion as the secured footlock, and works pretty well on DdRT by tying a long bridge and footlocking the tail.

Climb Safe!
Icabod

icabod wrote:
I may be way off mark here Dave, but it seems like you are equating friction within the system and climbing efficiency. [...] I believe that climbing efficiency comes from several areas, first a simple system with few moving parts, and second conservation of motion with a preference for use of larger muscle groups.

Well, from the standpoint of simple physics the upward friction in the system ought to be pure waste. It may not be avoidable but it is waste. I'm not interested in competition but I am interested in evaluating comfort, speed, and ease of use.

I think the bases are covered. The limb is wider than the sleeve so you get expected added friction where the rope is contacting the bark. The configuration of the hitch advancer was adding friction. The tightness of the hitch may have added friction.

Icabod delved into the other side, climber technique and efficiency for a particular mode of ascent. Theoretically the more you climb the more efficient you get for a particular climbing technique/configuration. At some point you plateau and are as efficient as you're going to get for the technique.
-moss