What grade aluminium would be best?

[Bki26]

I'm working on a prototype device for lead rope solo climbing and I'm at the stage of making a metal version for testing but quite stumped on what grade would be best.

It comprises of 2 plates with a 15° bend in each towards the end and one plate is 3mm other 5mm. Originally I was planning on making the 5mm plate stainless so I could weld an axle to it but I have decided instead I can get away with aluminium to massively reduce the weight (270g down to 80g for just that plate) so was thinking of going with 7075 but after doing a bit of research I've seen that grade does NOT like to have bends since it's sold already t6 treated and would probably crack etc.

What grade would be my best option for the main factors of needing strength, ability to take a 15° bend and ideally keeping said bend when under load with a carabiner through the "eyes" and lastly can be easily anodised since I'll probably have to do that step myself once I cut the radius edges.

Any help is extremely appreciated!

 

[Misterg]

What yield strength have you designed for?

 

[lchris21]

Im not a climbing expert, but have some lifting equipment inspection experience......
Most decent CAD packages would have an FEA function for differing material? Those eyelet walls look quite vulnerable for cracks etc. Also have you considered non controlled home anodising (Im assuming) and any post-treatment stress testing.
You could loose some bulk/weight out of the body of the plates with strategically placed holes maybe if weight is critical?
Not worth risking life and limb to save a few grammes, but good luck with the project

 

[Maker]

Most decent CAD packages would have an FEA function for differing material?

It looks like Fusion, which does FEA but I think you have to pay for "cloud credit" to run.

It'll be no good for solving non-linearities around work hardening of different alloys at the bend, which is really what he's interested in.

 

[Agroshield]

Having no shame in these matters, I always look to best of breed and copy that.

See what DMM or Petzl or any of the other tree monkey suppliers use.

Can I offer 2 1/2p's worth?

1p: my gut feeling is that the amount of material around that top eye is insufficient
2p: a lot of climbing gear is forged, which offers better grain flow and far better performance (fatigue, stress cracking, etc.)
2 1/2p: a lot of climbing gear is forged in China. Same word, different meaning.

 

[Bki26]

What yield strength have you designed for?

Im not a climbing expert, but have some lifting equipment inspection experience......
Most decent CAD packages would have an FEA function for differing material? Those eyelet walls look quite vulnerable for cracks etc. Also have you considered non controlled home anodising (Im assuming) and any post-treatment stress testing.
You could loose some bulk/weight out of the body of the plates with strategically placed holes maybe if weight is critical?
Not worth risking life and limb to save a few grammes, but good luck with the project

Its not designed to be a primary aka PPE certified etc device, it is simply meant to assist with an existing problem that we lead rope solo nutters have and help simplify the process involved.

If the weight is still pretty good I might be able to make it from stainless but I have yet to figure out what the total mass would be so it looks better suited for aluminium.

We all know the risks involved in it but unfortunately don't have the same r&d budget as big companies (the lead rope solo community is pretty small) so have to make do with whatever we can like the original pioneers of climbing equipment back in 60/70s etc.

Having no shame in these matters, I always look to best of breed and copy that.

See what DMM or Petzl or any of the other tree monkey suppliers use.

Can I offer 2 1/2p's worth?

1p: my gut feeling is that the amount of material around that top eye is insufficient
2p: a lot of climbing gear is forged, which offers better grain flow and far better performance (fatigue, stress cracking, etc.)
2 1/2p: a lot of climbing gear is forged in China. Same word, different meaning.

Most use 7075 it seems in t0 and harden it once in final shape.

Ultimately the device might not work but I still wanna give the idea a test hence wondering what grade aluminium would be best for the fact it needs to be able to bend without cracking like the stronger 7075 does.

If it does work and there is significant interest I will approach several of the low volume production companies around the uk to see if it is cheap enough for it to be made to the same standards as commercial gear.

 

[Misterg]

Its not designed to be a primary aka PPE certified etc device, it is simply meant to assist with an existing problem that we lead rope solo nutters have and help simplify the process involved.

Surely you've got some sort of loading figure in mind? (Even if it's just your own weight with some sort of safety factor?)

The tensile yield strength of aluminium alloys ranges from <35 to >400 MN/m^2. Cost and processing problems tend to increase with strength.

IIRC most climbing stuff is rated for 22kN - taking that as an example (without safety factors, etc), you would need between 55 and ~650mm^2 of material to take the load (at yield point), depending on which alloy you chose. How much material you actually have in your design (e.g. around the attachment eye), and what your design loads actually are will determine the *minimum* yield strength you need, and possibly rule out a swathe of alloys. (You need to consider failure in shear, too.)

You don't need an 'R&D' budget for this, just the back of an envelope - it's 1st year Engineering mechanics. Without doing the calculations, you're not designing anything in an Engineering sense, just drawing pictures. (Sorry to be blunt.)

 

[Bki26]

Surely you've got some sort of loading figure in mind? (Even if it's just your own weight with some sort of safety factor?)

The tensile yield strength of aluminium alloys ranges from <35 to >400 MN/m^2. Cost and processing problems tend to increase with strength.

IIRC most climbing stuff is rated for 22kN - taking that as an example (without safety factors, etc), you would need between 55 and ~650mm^2 of material to take the load (at yield point), depending on which alloy you chose. How much material you actually have in your design (e.g. around the attachment eye), and what your design loads actually are will determine the *minimum* yield strength you need, and possibly rule out a swathe of alloys. (You need to consider failure in shear, too.)

You don't need an 'R&D' budget for this, just the back of an envelope - it's 1st year Engineering mechanics. Without doing the calculations, you're not designing anything in an Engineering sense, just drawing pictures. (Sorry to be blunt.)

Yes that's totally fair and I agree with what you're saying, but right now I'm just wanting to test the idea and prove it actually works so for now I need to move away from weak 3d printed test pieces and make an actual full scale metal version since until you physically have something in your hands to play with you might not notice a problem you've missed.

I'll cross the safety and design refining bridge when I get to it but for now I need a "proof of concept" version hence my original question of what alloy would be good for strength and ability to bend which for now would allow me to test aspects of it.

 

[Misterg]

what alloy would be good for strength and ability to bend which for now would allow me to test aspects of it.

Since you don't know that you need anything exotic, I'd suggest designing it around one of the 6XXX series alloys - probably 6082 T6 since you're in the UK (or 6061 if you're USofA). Widely available, fairly strong, nice to machine, reasonably workable & anodises OK.

Aluminium Alloy 6082 Data Sheet - thyssenkrupp Materials (UK)

Looking to find information on the Aluminium 6082? We reveal important information such as applications, properties, forms and more. Click here to find out more.

www.thyssenkrupp-materials.co.uk

But FFS figure out what stresses you're dealing with and design to suit before you put it in to use.

Some info on standards that may be of general interest - (scroll past the foreign language to reach the English bits).

Test from EN 15151-1

EN 15151-2

(Disclaimer - These aren't the UK standards, and may not even be the ones that are relevant to your device... but they're *probably* close.)

 

[Bki26]

Since you don't know that you need anything exotic, I'd suggest designing it around one of the 6XXX series alloys - probably 6082 T6 since you're in the UK (or 6061 if you're USofA). Widely available, fairly strong, nice to machine, reasonably workable & anodises OK.

Aluminium Alloy 6082 Data Sheet - thyssenkrupp Materials (UK)

Looking to find information on the Aluminium 6082? We reveal important information such as applications, properties, forms and more. Click here to find out more.

www.thyssenkrupp-materials.co.uk

But FFS figure out what stresses you're dealing with and design to suit before you put it in to use.

Some info on standards that may be of general interest - (scroll past the foreign language to reach the English bits).

Test from EN 15151-1

EN 15151-2

(Disclaimer - These aren't the UK standards, and may not even be the ones that are relevant to your device... but they're *probably* close.)

Yea I'm not gonna take the risk on the safety side of it, I plan on making it as bomber (climbing version of flicking a ratchet strap and saying it ain't going anywhere ) as possible for testing purposes and not put any lives at risk and once I know if the idea works I'll then look into refining it and meeting requirements for the peace of mind.

Those test standards give a good idea what to aim for with any tests I do so appreciated, since my design is pretty simple if I end up wanting it commercially manufactured it shouldn't be too complicated being the methods already exist (petzl grigri for example is basically the same design of 2 plates and shafts linking)

Ultimately I really hope I can make my device a reality as it solves a significant problem for the solo climbing community and would definitely sell but only once I know it is safe even though it isn't a primary ppe device.

 

[selectedgrub]

 

[Kram]

I lost the thread after typing so heres a late reply...

In what way is it not a primary PPE? Apart from backup devices, will it not be the only attachement between harness and rope?

For a DIY or one off device could I suggest instead of bending, and intruducing stresses, that you could machine the 15 degree angle from thicker billet - The extra material used, would cost very little and to get flat plates would be quick simple machining but use a radiused edge cutter so theres no sharp corner stress riser.

I assume one side has a swing plate design for loading rope etc.. but perhaps the middle contents could be incorporated into one of the side billet peices if you use my suggestion. It would look a lot higher quality, again in my opinion. I hate the Petzl Grigri design with thin sheet, which was not even deburred from plasma cutting before their anodise process.

Compactness to the harness would be quite important for lead solo, no? You dont want it sticking out a way where it may hit or catch something in a fall or cross load the carabiner by the gate, Spanish style.

Notch make an alternative to carabiners which are more compact called the Quickie, which uses a 4 way locking, sprung "Slic pin", may be useful.

Eldrid Pinch is a carabiner-less climbing device which may be another design worth considering for the attachment.

Notch, DMM and ISC are companies worth approaching. For example, Notch is making some kit for a famous tree guy, including a mechanical prussik device, for Reg Coates, even though it has the same target market as their own Rope Runner device.

Other decives worth looking at, Petzl Zigzag, Buckingham Throttle, Bulldog Bone (not a certified device).

Tree mechanical devices share some similar requirments as a lead solo device except you are not supposed to take falls or whippers on them, and use a large static rope rather than skinny stretchy one. They both need to feed rope freely when not loaded

 

[Bki26]

In what way is it not a primary PPE? Apart from backup devices, will it not be the only attachement between harness and rope?

Its not primary PPE because it isn't the primary device, it's a secondary device which incorporates the functions of 2 devices (wild country revo and petzl micro traxion) into one simple device to hopefully solve one of the main issues with lead rope solo which is the primary device (grigri etc) not activating due to a head first fall which doesn't provide the necessary friction to activate the grigri cam so my device grabs the rope once the centrifugal mechanism activates which provides the necessary friction to cause the grigri to grab thus stopping the fall.

instead of bending, and intruducing stresses, that you could machine the 15 degree angle from thicker billet - The extra material used, would cost very little and to get flat plates would be quick simple machining but use a radiused edge cutter so theres no sharp corner stress riser.

I did think about it but ultimately making each "plate" cnc'd would be too inefficient and expensive hence going down this road. The top plate swings open once you lift it up to clear the central "shaft", if I was to get it forged commercially then I'd incorporate a clearance grove like the grigri side plate.

Compactness to the harness would be quite important for lead solo, no? You dont want it sticking out a way where it may hit or catch something in a fall or cross load the carabiner by the gate, Spanish style.

Currently it's only 1" thick and similar sized to a grigri so compact enough but like I've said previously I might have to change the design but I won't know until I have a physical complete prototype in my hands.

Eldrid Pinch is a carabiner-less climbing device which may be another design worth considering for the attachment.

I don't need to make it anymore complicated or add another potential point of failure or get sued for design infringement by a big player in the industry.

Notch, DMM and ISC are companies worth approaching. For example, Notch is making some kit for a famous tree guy, including a mechanical prussik device, for Reg Coates, even though it has the same target market as their own Rope Runner device.

As much as I'd love to work with the likes of DMM being a British brand this is a niche device that wouldn't be profitable for a large company to be interested in, take the rock exotica silent partner for example that is the gold standard in Lead Rope Solo gear but they were selling it at a loss and is now no longer produced and sells for 10x the original price to be collected.

I appreciate your input anyway.

 

[bourbon]

simplest way is to approach Petzl or the other companies with your idea, Ask for a royalty on each one sold.

 

[Agroshield]

Simplest way is to approach Petzl or the other companies with your idea, Ask for a royalty on each one sold.

Please read the last paragraph of his reply directly above yours. He explains with a concrete example why a similar device in the past was not economic for corporate production.

 

[Misterg]

I might have to change the design but I won't know until I have a physical complete prototype in my hands.

Might be worth 3D printing a prototype to get a feel for how it looks / handles before committing to metal.

 

[Bki26]

Might be worth 3D printing a prototype to get a feel for how it looks / handles before committing to metal.

I have already printed different aspects of it whilst refining the design (10+ pieces all over my desk lol 3d printing is revolutionary for rapid prototyping) and plan on printing a full sized version when the hardware (bolts magnets rollers etc) arrives but need a metal version for testing to destruction and because everything will act differently with aluminium vs slippery PLA.