Dynamic loads

[Lazarus2]

Yes Cary

People don't realise that if the diameter is doubled for the same length, the weight of the log will be quadrupled (ish).

What I meant, was that as the log increases in diameter, there is an increase to correlate in rope diameter, keeping a 4 foot constant length.

But these log weights keep increasing exponentially, i.e. a 4'long x 12" wide log will be around 4 times the weight of a 4' long x 6" wide log, but a 4'long x 2' wide log will be more than 8 times heavier than the 4' long by 6" wide log, because the increase is exponential.

 

[caryr]

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But these log weights keep increasing exponentially, i.e. a 4'long x 12" wide log will be around 4 times the weight of a 4' long x 6" wide log, but a 4'long x 2' wide log will be more than 8 times heavier than the 4' long by 6" wide log, because the increase is exponential.

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I understand what you are saying, but exponential has a very specific definition and what you are describing is not exponential. What we have here is a quadratic and specifically x^2. An exponential would be something like 2^x. Also the 2' log should be 16 times heavier than the 6” log ([2*2]^2).

Cary

 

[Lazarus2]

Oops, yes - of course, 16 times - thats what happens when metric heads try to go imperial (or work backwards then miss a gear going forwards again) /forum/images/graemlins/grin.gif And yes your exponential is the true meaning of the term.

What are you like at duelling chainsaws? /forum/images/graemlins/grin.gif

Imperial is the superior measure though, even though I struggle with it (Only got 10 digits without taking my socks off). Its up to the people of the USA to keep it alive!

As far as I'm concerned, math is a necessary evil - lives are at risk. Which was why I came up with a rule of thumb in the first place, so i didn't have to do all this math everytime I started a saw - give me the stage any day!

 

[TheTreeSpyder]

i think the amount of dynamic increase, can be divided by the amount of dynamic releif of elasticity and proper snubbing of force through good rope handling. A running rope can be used to snub such forces, or to build force and impact more if suddenly stopped after a free run.

The taller log, with higher CG/CM can get more of a drop impact by virtue of this increased length. But, on the flip side(which always exists in the duality of the equal and opposite forces); if you are using a tag line tied to top of the load you can muscle it over on the hinge/ make stronger hinge to carry load farther before free fall. In some scenarios, an increased angle of lean i think can give a similar result without the tag line. Then the additional length of the load can work in your favour; by giving more turning leverage over the load, to force stronger hinge, to hold on further, sometimes to toal inversion of load before tearoff(though that is a big chunk for that trick of holding on until total inversion). If the amount of beggining line tension is very high, it can help in this effect; of forceing a stronger support hinge, for softer handing off to the line of the load too.

This lessens the input force into the elasticity and snubbing control strategies. Friggin'Riggin is like a can do PMA(Positive Mental Attitude) exercise; whereby anything that can be set agianst you, should also present situations that can help you i think.

This Vid is of a backleaning branch that has to evade a trap on the left, but not come over my head on right (twist in pull/tag line and uneven faces helping in concert). If not for the tag line, and the shape of the load offering so much useable, leverageable length by the tagline, could not have as much control, or as strong of a hinge to usher load around and forward, while still hanging on. Especially from a back leaning position. The more 'hang time' on the hinge, and slower movement, the less impact on line i think.

 

[caryr]

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What are you like at duelling chainsaws? /forum/images/graemlins/grin.gif

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I don't know, but around here our chainsaws are more like broadswords than sabers.

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Imperial is the superior measure though, even though I struggle with it (Only got 10 digits without taking my socks off). Its up to the people of the USA to keep it alive!

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Imperial/SI it doesn't matter to me. It's just a different representation of the underlying reality.

Cary