Treeaddict
Treehouser
Sorry it’s Facebook. The unit rides up and down trees.
The Official Random Video Thread!
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Sorry it’s Facebook. The unit rides up and down trees.
Burnham
Woods walker
That pruning machine was developed quite a long time ago...iirc in the 1990's. The purpose of the pruning was to allow young second growth stands to produce clear wood (with a higher value) much sooner than would occur from natural branch dieback. I saw one demoed, but I never heard much of anything about actual production use. Moving the machine and its power plant did not fare well on much of a slope or rough topography.
The USFS let some contracts in the same timeframe for manual pruning, with polesaws. It turned out to be pretty expensive, with potential return-on-investment at a minimum several decades in the future. Also, workers encountered physical issues with neck and shoulder injuries at a surprisingly high rate.
This sort of stand improvement work never really caught on, to my knowledge. At least not in any significant volume.
The USFS let some contracts in the same timeframe for manual pruning, with polesaws. It turned out to be pretty expensive, with potential return-on-investment at a minimum several decades in the future. Also, workers encountered physical issues with neck and shoulder injuries at a surprisingly high rate.
This sort of stand improvement work never really caught on, to my knowledge. At least not in any significant volume.
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Burnham
Woods walker
Unintended consequences. We humans seem to excel in finding them.
flushcut
TreeHouser
Whoopsie doodle!
Knotorious
That Guy With The Face
Cross loaded carabiners tested in different configurations...
Burnham
Woods walker
That is excellent info, @Knotorious . Best thing on the subject that I've seen. Thanks.
Burnham
Woods walker
I've always wondered if shock loading breaks things at different levels than the slow increase of load that break tests seem to commonly use.
Anyone know about that?
Anyone know about that?
Knotorious
That Guy With The Face
Yes, my guess is that it definitely would. Shock loading produces different forces than slow pulling; this much I do know for certain. That's why companies use both slow pull testing and drop testing when testing their products.
Knotorious
That Guy With The Face
But I don't think that the ultimate breaking values would differ by huge amounts. The slower pull will generate slightly higher breaking strengths versus drop testing in most cases.
Kaveman
Treehouser
Shock loading can actually amplify the forces delivered quite a bit. E=mc², yall. Once things start gaining velocity, numbers climb quickly.
As far as the pruning machine goes, it looked like more hassle than it was worth. Lots of potential for huge amounts of hydraulic fluid sprayed all over the forest too. Glad to know they never caught much traction.
That harvesting motorcycle thingy is pretty cool. I can't see much use other than what they're doing, except maybe palm trimming, but I don't do that craptastic job, so I couldn't say.
As far as the pruning machine goes, it looked like more hassle than it was worth. Lots of potential for huge amounts of hydraulic fluid sprayed all over the forest too. Glad to know they never caught much traction.
That harvesting motorcycle thingy is pretty cool. I can't see much use other than what they're doing, except maybe palm trimming, but I don't do that craptastic job, so I couldn't say.
Burnham
Woods walker
While this is certainly so, I was more wondering if say 20kN delivered all at once to an object might break that object when the same 20kN delivered in a slow buildup to that load would not. I don't know at all.
Knotorious
That Guy With The Face
My understanding is that slow pulling simulates an ever-increasing static load and, once it reaches 20kN, if the carabiner or rope are rated for 20kn (let's imagine they are rated for EXACTLY 20kN, versus in the real world where the ratings are very conservative, and you can expect most things to break slightly above the rating value), then the carabiner and rope will break at 20kN or higher.
When you shock load the same carabiner or rope using enough weights to produce exactly 20kN during a drop test, you will often find that they will break lower than 20kN because of how the abrupt forces strain the crystalline (metals) or amorphous/semi-crystalline (polyester) structures of the materials in a MUCH more dramatic way than a slow pull test would.
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Knotorious
That Guy With The Face
But this is exactly why the ratings are conservative, to account for shock loading's effect on a piece of hardware or rope versus the effect of slow pull. If they only used the low pull values created by tests, then the carabiner's rating would be unrealistic. At least this my theory.
Knotorious
That Guy With The Face
Knotorious
That Guy With The Face
One of the guy's runs back for his phone and barely gets out alive...
Knotorious
That Guy With The Face
Whoah...
Knotorious
That Guy With The Face
LOW speed chase. This is so cool...
Knotorious
That Guy With The Face
I had no idea that car companies do this...
Sorry, I'm blowing up this thread.
Sorry, I'm blowing up this thread.
Knotorious
That Guy With The Face
Absolutely, force=mass x acceleration =mass x velocity ^2. Double the velocity you quadruple the force, the same force is needed to break stuff as the slow pull but it's possible with far less weight. Depending on the material and how big the shock load is the force could not have enough time to stretch elasticly, which can overwhelm a weak point in the rigging system. It's also the reason that impact guns are used, the torque is generated by the hammering effect of the small accelerating mass, and why shock loading rigging tends to break stuff. The slow pull is easier to measure the breaking strength which is what they're trying to measure, so it gives a consistent result, and it will also show the elasticity of the material, which is used for other calculations.
The factor of safety (which gives you the working load limit) varies depending on a variety of factors, and if shock loading is expected it's really high, 10 to 1 for rope compared to most rigging at 5 to 1, and shock loading most rigging is explicitly prohibited. That's a good portion of why i started doing trees, if things move suddenly at all when you're rigging in construction you have totally failed, but with trees everything is super dynamic and fun, yes I'm wierd like that
Rope is also elastic, but it needs time to go back to its original length after loading, another reason for the high saftey factor. I'm sorry but this is incorrect, the safety factor is an engineering value to try to accommodate real life rather than theoretical calculations. Everything that supports a load; rigging, buildings, roads, vehicles, phone screens, even your clothes are designed by using a safety factor, which helps engineers design stuff that isn't too big or small. The consequences of failure and expected abuse are also major considerations, and for stuff like cars they literally do a cost/benefit analysis for expected lawsuits from deaths vs cost of bigger part, and if the cost of a few settlements is less than the cost of the stronger part, then they use the smaller part, sometimes with disastrous results. When you see a recall that's what has happened, they frigged up and didn't account for something, and their saftey factor wasn't high enough so more failures are occurring than they had budgeted for, and now they've decided the cost of the recall is less than the court fees. Yay unchecked capitalism.
REALLY IMPORTANT PART TO THE END OF THE POST:
For rigging they usually consider the working load as a non shock loaded straight line pull with the recommended bend radius at the connections, and then require the user to know how to add an additional factor called efficiency depending on exactly how it's used. That's why if you look at a rigging sling you'll see a tag telling you different working load limits (WLL) depending on a straight pull, basket, or choker configuration, that's the increased (basket) or decreased (choker) capacity with the efficiency calculated in. End terminations also matter greatly, as does bending radius, which is why knots can cut the capacity by half or more. On more complex rigging like multiple parts of line even the friction of the pulleys matters and must be accounted for, as well as the layers of line on a winch, and line angles. They train us as apprentices to do the calculations for multi part line tugger setups by looking up the all different components efficiency; the line angle, bearing material, sheave diameter, end termination, winch layers, etc., all reducing the force that can be applied as the rope (wire in our trade) snakes through the rigging system. So if you have a 2k wll winch with 4 part line you can't actually pick up 8k, but probably more like 6.5 or less depending on its exact configuration.
Rigging trees is literally the exact same thing, the same principles apply and have just as much importance, which is why the prudent thing to do is almost always to climb higher and go smaller, limiting both the distance the cog will fall and the weight. In practice tree work is done by estimation far more than industrial work (very little estimation, wayyyyy more calculation), uses rigging that's designed to stretch to gradually apply the force to the system, utilizes rigging systems designed to spread the load through the tree in certain ways to support the tree structure, and ideally has a skilled ground guy to let the rope run which gradually catches the load and minimizes acceleration, kinda like gently applying brakes vs stomping on the pedal. All of these things aim to lower the force by lowering the acceleration, and not understanding them fully while pushing the envelope is a great way to ensure bad shit happens.
side note rant:
This is my biggest problem with rigging rings, terrible bend radius with way more friction, all to save weight and the cost of the actual gear, as if the pulley was the problem. When i read the "where does the friction need to be in our rigging systems" or whatever he named it i had to go drink, pure ignorance of the most basic rigging skills paraded as fact, except for the lower force on the tree itself part since the efficiency is so terrible. I get it, it works, and that's why rigging rings have been around since before recorded history (called lizards and deadeyes in the last millenia or so). Good for small stuff, but so is natty crotch, and when the weights go up it's time to start rigging intelligently. The only reason rings are viable on heavy shit is because we're completely spoiled with modern rope, arguably the biggest advancement in rigging since the modern crane.
Knotorious
That Guy With The Face
Absolutely, force=mass x acceleration =mass x velocity ^2. Double the velocity you quadruple the force, the same force is needed to break stuff as the slow pull but it's possible with far less weight. Depending on the material and how big the shock load is the force could not have enough time to stretch elasticly, which can overwhelm a weak point in the rigging system. It's also the reason that impact guns are used, the torque is generated by the hammering effect of the small accelerating mass, and why shock loading rigging tends to break stuff. The slow pull is easier to measure the breaking strength which is what they're trying to measure, so it gives a consistent result, and it will also show the elasticity of the material, which is used for other calculations.
The factor of safety (which gives you the working load limit) varies depending on a variety of factors, and if shock loading is expected it's really high, 10 to 1 for rope compared to most rigging at 5 to 1, and shock loading most rigging is explicitly prohibited. That's a good portion of why i started doing trees, if things move suddenly at all when you're rigging in construction you have totally failed, but with trees everything is super dynamic and fun, yes I'm wierd like that
I'm sorry but this is incorrect, the safety factor is an engineering value to try to accommodate real life rather than theoretical calculations. Everything that supports a load; rigging, buildings, roads, vehicles, phone screens, even your clothes are designed by using a safety factor, which helps engineers design stuff that isn't too big or small. The consequences of failure and expected abuse are also major considerations, and for stuff like cars they literally do a cost/benefit analysis for expected lawsuits from deaths vs cost of bigger part, and if the cost of a few settlements is less than the cost of the stronger part, then they use the smaller part, sometimes with disastrous results. When you see a recall that's what has happened, they frigged up and didn't account for something, and their saftey factor wasn't high enough so more failures are occurring than they had budgeted for, and now they've decided the cost of the recall is less than the court fees. Yay unchecked capitalism.
REALLY IMPORTANT PART TO THE END OF THE POST:
For rigging they usually consider the working load as a non shock loaded straight line pull with the recommended bend radius at the connections, and then require the user to know how to add an additional factor called efficiency depending on exactly how it's used. That's why if you look at a rigging sling you'll see a tag telling you different working load limits (WLL) depending on a straight pull, basket, or choker configuration, that's the increased (basket) or decreased (choker) capacity with the efficiency calculated in. End terminations also matter greatly, as does bending radius, which is why knots can cut the capacity by half or more. On more complex rigging like multiple parts of line even the friction of the pulleys matters and must be accounted for, as well as the layers of line on a winch, and line angles. They train us as apprentices to do the calculations for multi part line tugger setups by looking up the all different components efficiency; the line angle, bearing material, sheave diameter, end termination, winch layers, etc., all reducing the force that can be applied as the rope (wire in our trade) snakes through the rigging system. So if you have a 2k wll winch with 4 part line you can't actually pick up 8k, but probably more like 6.5 or less depending on its exact configuration.
Rigging trees is literally the exact same thing, the same principles apply and have just as much importance, which is why the prudent thing to do is almost always to climb higher and go smaller, limiting both the distance the cog will fall and the weight. In practice tree work is done by estimation far more than industrial work (very little estimation, wayyyyy more calculation), uses rigging that's designed to stretch to gradually apply the force to the system, utilizes rigging systems designed to spread the load through the tree in certain ways to support the tree structure, and ideally has a skilled ground guy to let the rope run which gradually catches the load and minimizes acceleration, kinda like gently applying brakes vs stomping on the pedal. All of these things aim to lower the force by lowering the acceleration, and not understanding them fully while pushing the envelope is a great way to ensure bad shit happens.
side note rant:
This is my biggest problem with rigging rings, terrible bend radius with way more friction, all to save weight and the cost of the actual gear, as if the pulley was the problem. When i read the "where does the friction need to be in our rigging systems" or whatever he named it i had to go drink, pure ignorance of the most basic rigging skills paraded as fact, except for the lower force on the tree itself part since the efficiency is so terrible. I get it, it works, and that's why rigging rings have been around since before recorded history (called lizards and deadeyes in the last millenia or so). Good for small stuff, but so is natty crotch, and when the weights go up it's time to start rigging intelligently. The only reason rings are viable on heavy shit is because we're completely spoiled with modern rope, arguably the biggest advancement in rigging since the modern crane.
All I was saying is that drop tests undoubtedly raise the ultimate rating for a piece of hardware or software above what it would be if only pull tests had been performed. It's obviously not the only determinatining factor for a rating. I could have worded what I said better.
