Why aren't POWs Aluminum?

[Merle Nelson]

Re the OP, as others have said, I don't see why not. If antal rings take the beatings they do with no issues, why not a POW

Antal rings and X Rigging Rings both went to great lengths to put on a "hardcoat" layer that virtually eliminated wear by clean ropes and prevented as much heat transfer through friction. I forget what the hardcoat is likened to in hardness but it's increadible for that application. Only weakness is muddy ropes can 'sand' through it and it can be chipped by strikes against hard objects.

An aluminum porty with true hardcoat could be interesting.

 

[Tree09]

From a manufacturing standpoint, welds in al are weaker than the surrounding metal (opposite of steel), so al parts are usually machined from billet. This is dramatically more expensive than welding and forming from standard steel shapes. In the industrial world, you will never see any aluminum in rigging, it doesn't hold up, and since al is work hardened, every dent from it slapping the tree trunk would be a potential crack. The only rated aluminum I've ever seen as a fitter are rings on a harness (very expensive one for rope access work). While vastly superior for heat dissipation, it's strength issues and work hardening would make me leary of a pow. Bollard yes, pow no. While I'm a part time at best tree guy, I'm a fan of steel stuff, but then again my heavy lowering line of choice is treemaster 3 strand. .

 

[SeanKroll]

I learn so much here!

Are bollards milled, not welded? Why bollards but not POWs?

 

[Mick!]

Good info Kyle.

Look at the shapes Sean, milling a bollard is straightforward, a POW, not so much.

 

[Tree09]

Thanks. When al is heated, it gets softer, no matter the cooling rate. They heat it up after forming processes, which anneals it, allowing more forming (think a beer can for example). The plate that you can buy where the aluminum is very hard has been cold rolled, which are rollers that compress the sheet, hardening it. Once you weld it, the heat from welding anneals the area, making it softer. Stuff made from aluminum is usually oversized to account for the strength loss (in welded stuff).

 

[Marc-Antoine]

Thanks for the explanations Kyle.
I saw on the net that we can anodize small aluminum parts at home. It wouldn't be optimized at all, but I wonder if that couldn't be used to "repair" a worn out or dented coating and get some more life for the device.

 

[DMc]

Thanks. When al is heated, it gets softer, no matter the cooling rate. They heat it up after forming processes, which anneals it, allowing more forming (think a beer can for example). The plate that you can buy where the aluminum is very hard has been cold rolled, which are rollers that compress the sheet, hardening it. Once you weld it, the heat from welding anneals the area, making it softer. Stuff made from aluminum is usually oversized to account for the strength loss (in welded stuff).

While all true, it does not negate the fact that welded aluminum has been used successfully for not only port-a-wraps, but many, many other parts where weight is part of the design's consideration.

 

[Tree09]

Agreed. But for a rigging device at the base of a tree weight isn't an issue, in fact the only reason it would be aluminum would be for heat dissipation. You could incorporate cooling into a steel design, and that would eliminate glazing (cooling fins made from al on the inside of the pipe, water cooling, etc). From my experience of a pow, since they aren't lashed to the tree like a bollard is, so they slap the trunk just about every time you use them, which dents the soft al and causes work hardening, which in turn causes cracks. Al is a wonderful material, with lots of uses, however, in my humble opinion, is the wrong material to use for a pow. I've repaired several al objects in my life so far, just about all of them failed due to cyclical loading and work hardening far below what their breaking strength was. The grcs al bollard is massive, and with it being not anodized will wear out from abrasion before cycles to failure and the resulting work hardening cracking. I think that was intentional design. Proper design always takes into account the limitations of the material, and in the case of the grcs, I think the decision to not anodize the bollard was to require replacement before other more serious failure modes would occur.

 

[rbtree]

Since aluminum dissipates heat better than steel, and you can build them as strong as needed, why doesn't anybody make them?

Sean, as seen in a link above, the Buckingham POW is available in aluminum. In fact, Patrick has had one for years. It has a deep groove in it, and he may have replaced it recently. Conversely, my powdercoated (?) steel one, which may be 20 years old, is fine. Yes, Al does dissappate heat better.

 

[SeanKroll]

... From my experience of a pow, since they aren't lashed to the tree like a bollard is, so they slap the trunk just about every time you use them, which dents the soft al and causes work hardening, which in turn causes cracks.

Fwiw, a choked $4 ratchet strap, with the ratcheting buckle hooked to the top of the POW, does wonders to prevent flop.

 

[Mick!]

Do you back yours up with a heavier strop Sean?

 

[SeanKroll]

The ratchet straps holds the top of the POW upwards. The anxious strap on the bottom, as usual.

 

[CurSedVoyce]

Now that you will have the GRCS, I doubt the porty will be used as much
Smoothes your rope man out once the learning curve is handled.

 

[kevin bingham]

I love my grcs but my porta wrap gets used quite a bit more. Its so much easier to get out of the truck. An aluminum one would be even more so!

 

[MasterBlaster]

No need to break out the big guns if you don't need em!

 

[CurSedVoyce]

True. I guess on the smaller ones I don't need any pretension on I use my portys more. But then, most of what we do.........

 

[CurSedVoyce]

Zip line is another exception. We do a lot of that. But that is anchor point and not lowering with friction.

 

[SeanKroll]

Good thing I have blocks for fair leads. A bid to submit calls for removal of 4 large firs, on top of each other, in a row. Winching onto a gin pole action.

Stuff to learn. Tricks to pick up.



Feeling like a bigger fish with a GRCS, ya know, a milestone, and a useful component component in the arsenal.

 

[CurSedVoyce]

Just a tip, often with a gin pole, just a hand pulled tension works fine instead of cranking the bollard. If you need the lift, great, but if you can just tip the piece, hand pulled tension.

 

[CurSedVoyce]

Negative blocking, crank it. Get the stretch out

 

[SeanKroll]

Roger that!
Thanks.

I'll look into a grcs video.

Is it such that the shock load is negligible enough to not pretension, if a power drill is readily available?

 

[CurSedVoyce]

Situation d pendant like all tree work

 

[SeanKroll]

I can see it being within wll and safe and efficient hand tight.

This group of firs is next to primaries. Would be nice to hang marketable lengths... Log buyer is just across downtown.

 

[CurSedVoyce]

Then lift and drift. Run two lines if possible.