TIP Physics

SoftBankHawks

SoftBankHawks

Branched out member
Location
Japan
Could someone check these figures and correct mistakes.
If we take the climbers weight as 100kg I would like to know the weight applied to the TIP.

SRT w/anchor belay 200kg.

SRT w/ choke 100kg.

Dbrt 200kg.

dbrt w/ floating
anchor belay 400kg.

Footlock ?.

RAD ?.
 
Dbrt = 100kg, because it is a closed loop both sides of the line hold 50kg

Dbrt w/ floating anchor belay = 200kg, same concept as SRT w/anchor belay

Footlock = 100kg
 
Thanks Leon, I was confused about the Dbrt because it seems that as we pull to go up the hitch is effectively not working in the dynamic at the TIP, only when we have sat back on to the hitch does it form the loop.
 
One important factor to remember with DRT is that, yes each leg of rope carries 50% of the load, as well as the crotch recieving roughly 50% vertical force as the rope runs through, however; when the rope ceases to run through the crotch (in between thrusts) the crotch (TIP) is now holding 100% load. Again, when you are climbing DRT and the two legs of rope recieve 50% each, the TIP is still recieving 100%, then at increased angles when limb walking the TIP is recieving uncalculated forces due to the angle of pressure. Depending on your climbing technique while limbwalking you can distrubute your weight partially onto the limb, accounting for the increased angle pressure on your TIP.

Also remember that at static load the TIP recieves 100%, now when you thrust or footlock you are in effect applying dynamic load to the TIP... lets say like a post pounder. The hammer rests on the target post at 100% load, then when lifted and released the force increases exponentially. Now envision the TIP recieving an exponential force as you thrust upwards with each bounce (most prevailent with SRT). Climbing with a smooth style will help with this, as well as your joints (and you'll look cooler to that chick watcing from across the street). ;)

All such physics must be in mind while climbing and working. Don't let your gaurd down.
Climb safe.
Ian
 
Leon wrote:

[ QUOTE ]
Dbrt w/ floating anchor belay = 200kg, same concept as SRT w/anchor belay


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Although if it is a floating false crotch off of a straight DdRT (i.e. with no belay, no way to lower the climber), then it is 100kg, same as DdRT.

Be aware that for the load to be doubled both legs of the line must be parallel and there would be no friction at the TIP. In reality, however, the legs of the line will probably not be parallel, there will be friction at the TIP, and there will probably be several other points of contact besides the TIP that spread the angle of the legs of the rope and create additional friction.


SoftBankHawks wrote:

[ QUOTE ]
...as we pull to go up the hitch is effectively not working in the dynamic at the TIP,

[/ QUOTE ]


Your hand(s) is acting in the same manner as the hitch--it creates a fixed, closed loop. Each leg of the loop bears 50% of the load and thus the TIP still sees 100% of the load, in your example, 100kg.
 
[ QUOTE ]
...the crotch recieving roughly 50% vertical force as the rope runs through,...

[/ QUOTE ]


I don't think this is correct. Why would the crotch receive roughly 50% as the rope runs through?

Your second paragraph:

[ QUOTE ]
Also remember that at static load the TIP recieves 100%, now when you thrust or footlock you are in effect applying dynamic load to the TIP... lets say like a post pounder. The hammer rests on the target post at 100% load, then when lifted and released the force increases exponentially. Now envision the TIP recieving an exponential force as you thrust upwards with each bounce

[/ QUOTE ]

contradicts your first statement, but, I think, is more accurate.
 
My 2centses (please don't feel short changed); about these amazing topics.

If the support(s) doesn't hold 100%; you fall.

If the system is closed; the support equals the load.

If system is open; and the bight is at the TIP; the load is doubled on the TIP.

If it is open and the bight is at the load (split supports); then the load is halved.

These are inline calculations. At less than 120 spread the ends will have leverage over the bend. At 120 spread the ends force equals the bend/bight force. Flatter than 120, the bend will have leverage (be less than) the ends(singularly).

A straight leg is a minimal system with an equal and opposite shared loads. That is equal in loading force; while opposite in direction of that force. Each bend/bight begins a compound system; to be calculated separately from other compound systems.


These are static; dynamic gives more forces by a distance over time factor(speed). The dynamic can be dampened; by rope length, elasticity, construction, knot choice, flex of support; etc. And, percentage of tensile strength loaded; whereby, the SWL of a line under load and the line's elastic response (not by length) are reciprocals. So, a 1000# shock on a 10k line gives an SWL of 10:1; while a 2000# shock to same line gives an SWL f 5:1. But, more dampening would be provided to the 2000# shock. So; a 2000# shock to an SRT would give more elastic dampening than same to a DdRT (from a 400# source); so the SRT would give less loading to the TIP. Similar for a multi-power 2:1 or 3:1 rig. Statically, the 2:1, 3:1, DdRT would give less loading to a singular TIP; but dynamically they would give more than single line with a control leg or SRT. We say more line in a system gives more dampening; but we don't count multiple legs to load as increased distance!!


DdRT is 1:1 in hang/static; but is 2:1 + friction in smooth ascent, and 2:1 - friction in smooth descent. Impacting, inertia jerking ascent/descent even just hanging will raise these numbers.

There are 4 pulley forces. Pulley on load to give 1/2 speed at 2/1 power; and it's reciprocal pulley on effort to give 2/1 speed at 1/2 power. Then pulley on support/anchor/non moving position that divides a load line to a control line that gives 1/1speed and 1/1 power that doubles the support loading; and then it's reciprocal/equal-opposite of a pulley on an input anchor to take the input force and it's equal and opposite effort force and focus both into a closed system to the load. Seeing as the input anchor takes a 2x and the system is closed, so then the load does too! But the 2x is only on the effort and not the weight of the input; for the existence of the person or machine is the equal opposite of that, so only it's input force can have an equal opposite to be compounded with it's direct input to further impact load. So, that is 1x weight (if in proper direction) and 2x input force.

Orrrr sumetin like'dat
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Thanks for sharing your thoughts Mahk Adams... please allow me to explain my train of thought here, and do correct me if I'm misstaken.

If the climber rests in DRT, the crotch (TIP) is recieving 100% static load, with each leg of rope recieving 50% correct? What I'm trying to refer to here is the few moments in between static and dynamic loading - while thrusting. Hmm... there has to be a gradient of forces being applied during these moments which I think will tie the whole process together better now that I analyze it further. (note: I don't have a measuring device for force)

1. The initial static load (climber) is 100%
2. The change from static to dynamic as the climber take a thrust applies the pile driver concept in increasing the load beyond 100%
3. (point in question) Our dynamic rope system as doudled acts to some degree giving a slight catapulting effect, though not really very noticable and for a brief moment, and quickly the crotch recieves a marked decrease in force as the rope runs through. I can't say exactly how much without measuring it but for argument sake I said "roughly 50%" of the initial static load.

One could also say that the climber must have a slightly jerky style while thrusting, as a smooth pull will apply a more even distribution of weight.

I'm just envisioning the climbing process in my mind here, and probably over-analyzing it, but physics are a very important part of what we do in terms of safety and understanding loads.
 
Is there such a thing as an elasticated friction hitch or cambium saver? I like to girth hitch my pulley onto the stem rather than chance a decent branch being in place, most of my work is crown reductions which means that I always flat-line and climb above my TIP
mad.gif
. Intuition for safety is pushing me to work of an SRT system, when climbing my two concerns are TIP snapping through excess force like with a fall and the impact to my body. I chatted to an arborist of 23 years about wearing a full harness and his reaction to it was like..."well what are the chances of that (type of fall) happening".
True about the amount of variables and I cant forget that this is why I like tree climbing and rigging so much and that there will never be a fool proof system. Always being kept right on our toes!
 
Usually these items are too short to give very much elasticity; but, the friction hitch itself (and it's terminations) can slip to give similar absorption/exchange of dynamic distance force to frictions to dissipate from mechanical. When close to the TIP we will have less absorption through rope device, than when far; so the need for more absorption as you site is variable in the system.. Then, tp your same point there is the possibility of (choosing) flex of the TIP itself; to give elastic response that could even replace dynamic absorption response lost as you get closer to the TIP (and have less rope/rubberband in the system).

A doubled rope gives less elasticity than a single.
 
For DDRT, neglecting friction at the crotch for the moment, the load at the TIP can never be less than the weight of the climber, as long as the TIP is the sole support to the climber. If the climber is hanging in the saddle, the downward force on the TIP is the climber's weight. That is the static force.

When the climber strokes, i.e. lifts himself, a dynamic load is generated at the TIP in addition to the static load. So the total load at the TIP is the static load plus the dynamic load. At the end of the stroke, the dynamic load goes away and once again the TIP only has to support the load of the climber.
 
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Is there such a thing as an elasticated friction hitch or cambium saver?

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I believe someone answered this already, but there's a good reason why such a device does not exist. Climbers use static lines, unlike rock climbers who use dynamic lines. Why is that?

Having a dynamic element in the line accomplishes two things: First, it equalizes (to some extent) the force on the TIP. Second, it requires the climber to use some energy towards stretching the material which otherwise would be used to lift the climber closer to the TIP. Every time the line stretches and recoils, energy is absorbed by the line. Generally, we like to utilize as much of our expended energy as possible towards the task at hand (ascending the tree).

Beyond that, if you're TIP is that questionable, it makes sense to either pick another one, or back it up.
 
SoftBankHawks:

Regarding your initial post, the following forces apply when there is no movement in the system (i.e. the climber is at rest). Note that friction is ignored, but in the real world it can be significant (as when the rope runs through a FC not utilizing a pulley or through a natural crotch).

1. SRT (when anchored below and running through a pulley at TIP): 200 kg

2. SRT (Tied off / choked at TIP): 100 kg

3. DdRT: 100 kg

4. DdRT “w/ floating anchor belay” depends on the setup of your static line. If your static line is rigged as in 1 above, the force is 200 kg. If your static line is rigged as in 2 above, the force is 100 kg.

5. The same applies for all other setups: if your weight is on a line which terminates above or runs back to you, force is 100% of mass (weight); if the line runs straight down to a different rigging point, force is 200% of mass (as a rule).

Of course, what Mahk said applies: there are other factors that affect forces such as friction.

Something that was mentioned by IJB and needs clarification is the impact of “increased angles when limb walking” upon the force at the TIP. As climbers and riggers, we’re trained to beware of increased angles in any circumstance, and rightfully so since the forces involved can approach infinite values. However, we still need to think things through.

When limb walking, increased angles at the TIP may actually decrease the force applied to the TIP. There are a number of factors which need to be considered, including:

• The Angle between the rope and the pull of gravity
• The angle between the rope and the limb or trunk to which the TIP is secured
o Bear in mind that a branch can generally with stand more force applied along its axis than it can when applied perpendicular to the axis.
• The amount of weight born by the limb you are standing on.

Because there are so many factors involved, it might be helpful is examples are used. I’ve included one that is relatively simple, but others might be suggested. When the climber is at rest, all forces are balanced.
 

Attachments

[ QUOTE ]
When the climber strokes, i.e. lifts himself, a dynamic load is generated at the TIP in addition to the static load. So the total load at the TIP is the static load plus the dynamic load. At the end of the stroke, the dynamic load goes away and once again the TIP only has to support the load of the climber.

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That was my point as well.
 
[ QUOTE ]
[ QUOTE ]
When the climber strokes, i.e. lifts himself, a dynamic load is generated at the TIP in addition to the static load. So the total load at the TIP is the static load plus the dynamic load. At the end of the stroke, the dynamic load goes away and once again the TIP only has to support the load of the climber.

[/ QUOTE ]


That was my point as well.

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I'm sorry, but I humbly dissagree... to a certian extent, and agree to a certian extend. At face value the static load plus dynamic load equals greater than 100%, yes, but not in a consitant flow from sart to finish during each individual hip thrusting event in Ddrt.

I think I see a controled study and research paper coming out of this.

Ian
 
Sure dynamic loading is likely not going to be consistent. We likely 'push' harder at some points during the stroke than at other points through the stroke.

I think the point I, and Mahk before me, was making was that the TIP always has the weight of the climber, and the dynamic loading due to the ascension stroke adds to the force at the TIP rather than lessening it.

Hence during climbing, the loading on the TIP is more than our weight due to dynamic loading.
 
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Mahk, I knew it was, I was just supporting and elaborating a bit.

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Ron, I knew it was, I was just supporting without elaborating a bit.
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Thanks for picking up where I was slacking. Same for your last post.
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[ QUOTE ]
Sure dynamic loading is likely not going to be consistent. We likely 'push' harder at some points during the stroke than at other points through the stroke.

I think the point I, and Mahk before me, was making was that the TIP always has the weight of the climber, and the dynamic loading due to the ascension stroke adds to the force at the TIP rather than lessening it.

Hence during climbing, the loading on the TIP is more than our weight due to dynamic loading.

[/ QUOTE ]

And in DdRT TIP friction must be added on ascent and subtracted on descent for TIP loading.

The base/nominal weight is inescapable; (as are all forces) it can be subtracted from/lessened on descent; but must always be realized in full disclosure; for there is no free ride. Every weight, angle, distance, impact, friction etc. are multipliers; even if less than 1/reciprocal of our usual view of a multiplier. Inline leverage in non-flexibles is just 'not leveraged'/length doesn't matter becasue it has a cosine multiplier of Zer0 X it's leveraged force potential (weight, forces X length of CG) etc.; but in full disclosure, all these things must be recognized.


"Nature to be Commanded; Must be Obeyed"
-Sir Francis Bacon
 
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