Pendulum rigging

[Stephen Blair]

 

I think we must have some sort of scottish roots with names like Angus, Keely, Allister and Lachlan! Irish too... (Don't judge me for it)

 

nowt wrong with the irish mate, :thumbup:just go to Dublin for your holidays and you will see what i mean:biggrin:

[Angus]

I still get a buzz out of chatting to people on the other side of the world!

how do you guys get on with snales and beasties, how do you clear a site of them or minimise the risk??

In southern parts of Australia, things that bite are not as prolific as they are up north. We do come across snakes and bitey insects fairly often during a week, but working up in the tropics is where most of the nastys are.

[Angus]

Can you eliminate the need for a dynometer in a system like this by taking the pieces off with a step cut at 90 degrees to one of lines then tensioning 1 line to lift the piece.

Removing the dynometer would defeat the whole purpose of the system...

 

You probably could do what you suggested, but there are plenty of other systems that have an equivalent level of control of your suggestion but would allow a much faster work rate.

Reg has an excellent example of a dynamic system for lowering timber sections using his twin rope lowering device.

[ame=http://www.youtube.com/watch?v=aiqK8z_4GyM]YouTube - Video for Angus[/ame]

 

Opposing pendulums is for absolute and complete control where everything must be as static as possible.

[rbtree]

Hey Angus....

 

If Graeme is like me, he'd easier know when and where the article ran. I used to get published a fair bit (my skiing photography mostly) and kept track of all the pubs..... I know I could find the article, as I've kept most of my arb mags, but it would be a bit of work to dig through them all.

 

As far as using two GRCS's for the job, it could have been done, (had Greg or anyone invented such a device at the time) as tension could have been progressively and carefully applied to each till the load lifted off gently. However, there would be no way to use an inline dyno....

 

The directional problem is solved by adding a block directly above the capstan....which would add a bit more resistance and friction to the system.

[rbtree]

My comments within, in bold

 

As part of the solution we've taken opposing pendulums to the next level. A few weeks ago I derived the formula for a triple point lowering system.

I've written and tested the formula AND program, and we're now eagerly waiting to test it out on the job.

The applications of the triple point lowering system are very exciting - far beyond this one job. Sounds awsesome

 

For example, any job where there are is at least ONE high point can use the program. (The other two can be on the ground, to a car, etc.) Gotta hear more about that!! I can almost visualize, I thinkkkkkkkk....?

This would give crane level accuracy for significantly less cost.

The highpoints can be at any angle from each other. With three, I can see that

The formula can tell you how much tension is on each line, and each highpoint.

 

I've written the program as a graphical windows application, but I'll probably code it for a mobile phone fairly soon.

 

We'll hopefully have a video of the system in action some time in 2010.

 

Not to negate, criticise, or denigrate in any way your calc's, or the technique, but with 2 GRCS's any load, within range of the friction drum's holding capabilities and the strength of two men, can be lifted gently, and then lowered, up to 2500 lb or more.

Edited January 2, 2010 by rbtree

[wiley_p]

Angus, I have a question. At some point the inside angle on an anchor will be in creasing, as the opposite side it is decreasing, how do you account for the added force being imparted on the far high angle block?

Secondly is your program available for others?

[Angus]

If Graeme is like me, he'd easier know when and where the article ran

Thats the thing - when I asked him about it, he said ArborAge was the only one he knew of. The journal of arboriculture didn't accept it...

 

Not to negate, criticise, or denigrate in any way your calc's, or the technique, but with 2 GRCS's any load, within range of the friction drum's holding capabilities and the strength of two men, can be lifted gently, and then lowered, up to 2500 lb or more.

I completely understand, and as I said above, lowering with two ropes isn't something new.

I guess I am trying to address this fixation with using two GRCS's... The job we derived opposing pendulums for was about control and efficiency.

We keep talking about how the GRCS could've been used, but I can't seem to get an acknowledgement that it doesn't improve both control and efficiency.

If there is a disagreement with that, then there's a fundamental misunderstanding as to why one would use opposing pendulums.

 

On that note, the job we've created the triple point lowering system we need the same level of control and efficiency - but we can't find two opposing highpoints... But we can find three!

 

I'll do a second post with a picture.

[Angus]

At some point the inside angle on an anchor will be in creasing, as the opposite side it is decreasing, how do you account for the added force being imparted on the far high angle block?

The compass bearings of the three highpoints are fixed, and as you've correctly pointed out, the vertical angles will be ever changing.

We only need to address this change at the point of cut - so we have a device that is sat on each rope and tells us the inside angle.

These three angles + the weight of the log we are cutting are fed into the program which then specifies what the exact tensions need to be.

 

I'm hoping to release the program at the same time I release the video of the system in action.

When I wrote the program I did write a test GUI for the calculation class. There are a few boxes which pop up with horizontal forces, vertical forces etc. but this will eventually be integrated into a 3D model of the parameters entered. With this ability you'll be able to specify limits on your anchors. This will be particularly helpful for ground anchors.

 

 

Thats what the class tester looks like, I don't think you could even call the application in alpha stage at the moment.

 

If you use Google Sketchup (free), you can take a look the Trivect 3D model

 

I gave the example earlier that you've got one high point, but no opposing highpoint(s), Trivect would allow you to have two ground points.

 

In the picture, the ropes run down to the ground at -34o and -30o, our highpoint is 60o to the point of attachment on the log.

The two ground points are separated by just 25o.

Our log is going to weight 600kg when we cut it. We can see that that tensions of each line are quite high compared to the load.

 

There are still a few bugs, and there are certain conditions that make the program do back-flips. I've added a few constraints to the basic formula to help the program stick within reality.

[rbtree]

Thats the thing - when I asked him about it, he said ArborAge was the only one he knew of. The journal of arboriculture didn't accept it...

 

 

I

I guess I am trying to address this fixation with using two GRCS's... The job we derived opposing pendulums for was about control and efficiency.

We keep talking about how the GRCS could've been used, but I can't seem to get an acknowledgement that it doesn't improve both control and efficiency.

If there is a disagreement with that, then there's a fundamental misunderstanding as to why one would use opposing pendulums.

 

 

Angus, With inline dynos, you'd have more control, simply by being able to determine the exact amount of force to apply. But the efficiency with GRCS's would be improved, as there would be no need for prussics on the load lines, for the Tirfors and dynos.

 

Either system would work essentially the same with opposing pendulums....Each GRCS would be cranked till appropriately tight, the cut made, and then cranked till the piece lifts off gently. With your system, all that was done prior to making the cut, which is really slick, and speaks to the mathematical precision of the program and figuring...and the precise weight estimations...including taking into account the weight from added water lower down.

[Stephen Blair]

how do you know what size of bit you are cutting off, and if its too big, then what do you do??sorry if i am missimg the point here, i think i know what you guys are talking about, but in my world, we just take less than what we thnik the equipement will take, if its too big, i just get a bit twitchy, cut a chunk off or hold my breath, holding your breath usually cancels out all weights and ratios to making a boo boo:001_smile:i havent and probably never will come across the tree situations you guys come across, but the bottom line is, someone has to get up there and cut off a bit.