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Cam lobe damage after fall.

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Hi,

I need a bit of advice on a damaged size 3 DMM dragon cam. Following a fall there is a flattened area 1/2 cm by 1/4cm in size on one lobe, which has caused a flake on one side of the lobe. The wire on that size now brushes against the flake, but only when fully cammed. The cam is about 2 years old.

Would appreciate some advice on whether:

a) the cam should be retired.

B) if still ok to use, would it be ok to gently file down the flake to prevent the wire catching.

Can't see a way to upload photos here but hopefully the description suffices!

Thanks,

Kevin 

 Andypeak 13 Jul 2020
In reply to Kevin_Daniel_Garvey:

I'd get rid and replace or send to dmm for inspection. You never know they might give you another at cost price or something

In reply to Kevin_Daniel_Garvey:

This really is a question for the manufacturer to advise on. There are some expert metallurgists on this forum, but ultimately DMM know their products better than anyone else. Sounds like it took a fair amount of force though

 jkarran 13 Jul 2020
In reply to Kevin_Daniel_Garvey:

If it's actually a flake implying a crack has formed I'd definitely send it to DMM for them to take a closer look.

If it's just bulged or torn the surface slightly raising a little burr then it's your call, you could file it off but it'll never be quite the same shape again but that may not matter in reality. Again, checking with DMM direct to see how seriously damaged they think it is seems sensible if you're worried.

jk

Post edited at 14:54
In reply to purplemonkeyelephant:

Yer that's fair, it's a bit of an unfair question to put on people. But thought I'd test it out on the masses to gauge people's experience of this, in case I was over reacting a bit. 

Thanks for your advice, I'll pop an email over to DMM. 

Kevin

In reply to jkarran:

Cheers JK, that sounds sensible. 

Kevin

 timparkin 13 Jul 2020
In reply to Kevin_Daniel_Garvey:

Try this for a photo but I back up  the others opinions in sending a photo  to  DMM

https://imgbb.com/

In reply to timparkin:

Ah thanks, nice one! Here's a pic...

https://ibb.co/xHfG61H

Kevin

 nniff 13 Jul 2020
In reply to Kevin_Daniel_Garvey:

IMHO - file it off. 

 Coel Hellier 13 Jul 2020
In reply to Kevin_Daniel_Garvey:

> Here's a pic...

File it off.  It'll be fine. 

 jkarran 13 Jul 2020
In reply to Kevin_Daniel_Garvey:

I'd file that off.

jk

 The9inger 14 Jul 2020
In reply to Kevin_Daniel_Garvey:

Looking at your photos I had a similar issue with my big blue cam when it was fallen on albeit slightly smaller affected area, filed it so that it didnt rub on the other lobe and carried on climbing, it hasnt caused an issue since 

In reply to The9inger:

Thanks everyone for your input, much appreciated! 

 Prof. Outdoors 15 Jul 2020
In reply to Kevin_Daniel_Garvey:

It does look repairable by filing it.

It would, however, be interesting to hear DMM viewpoint of what happened here.

Why not send the photograph to DMM and get their feedback? I have always found them to be extremely helpful.

Post edited at 10:22
 muppetfilter 15 Jul 2020
In reply to Prof. Outdoors:

On the grounds of  liability I would suspect DMM will tell the OP to take it out of service, imagine the potential lawsuit if they advised to use it and it failed. Any force sufficient to deform the lobe in such a way could potentially affect the integrity of other cam components.

Post edited at 10:33
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 Neston Climber 15 Jul 2020
In reply to Kevin_Daniel_Garvey:

I did a very similar thing last summer to a red Camalot falling off the bulge on King Bee Crack.

I retired it (it was a decade old anyway). Some friends throught it would be OK after some fileing, but my thoughts were that because of the 'dent' there would be a lot less contact between rock and lobe (less than half of designed) if the cam was touching the rock at the same point. Not science but worth considering.

Glad you were OK after the fall. 

 Toerag 15 Jul 2020
In reply to Kevin_Daniel_Garvey:

The question is, how vulnerable to microcracks is the alloy used, and have any been created?  It's one thing having a lobe squidge as per the pic, but another to have it split in half due to the microcrack created in the first instance.

8
 tallsteve 15 Jul 2020
In reply to Kevin_Daniel_Garvey:

You're asking this question because cams are bl**dy expensive.  If they were cheaper you wouldn't risk your life on it again.

Check out https://koubaclimbing.com  .  They manufacture cams and do 4 varieties including double axles.  Just bought a set of their Manta cams at £35 per cam including delivery (£10 48 hrs from Czech Republic).  Really nicely engineered, easy to place, solid and 7 cams cover 20mm to 145mms of crack.

At £35 you'd chuck it away and buy another, at £70 you'll umm and arrr and risk your life.

Post edited at 11:59
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 nniff 15 Jul 2020
In reply to Toerag:

> The question is, how vulnerable to microcracks is the alloy used, and have any been created?  It's one thing having a lobe squidge as per the pic, but another to have it split in half due to the microcrack created in the first instance.

Cracking would be associated with brittleness, but the 'squidge' is clearly a plastic deformation, so I would say that the alloy is not vulnerable to microcracks.  That would be a bad thing - hit a cam with a big load and it shatters - bad day out for all concerned

 AlanLittle 15 Jul 2020
In reply to tallsteve:

While I see your general point that people shouldn't cut corners on safety equipment, in this case I really don't think anybody would be risking their life on a normal bit of wear & tear like the one in Kevin's photo.

Post edited at 12:13
1
 duchessofmalfi 15 Jul 2020
In reply to timparkin:

I'd file that off and keep using it

 beardy mike 17 Jul 2020
In reply to Kevin_Daniel_Garvey:

The normal mode for failure for a double axle cam lobe is them it deforms the entire cam lobe flattening it against the opposite axle. This would be permanent deformation and would most likely cause the cam to become inoperable and it would be quite noticeable. To me this looks more like the surface has moved against a pebble or protrusion. I’d be surprised if it’s caused structural damage to the lobe - microcracks are not really a thing - there were problems I believe with fatigue  in 2000 series duralumin in aircraft structures, but these are most likely 6083-t6. Without seeing a side profile I don’t know for sure but I’d be optimistic from that photo.

 bergfuhrer 18 Jul 2020
In reply to Kevin_Daniel_Garvey:

If the fall was enough to damage the cam, then it is worth having DMM check it over. It is possible the shaft that the cams rotate on has been invisibly over stressed past its elastic limit, so that nxt fall it fails.

Filing off the damage is no issue, just the potential invisible damage.

4
 wbo2 18 Jul 2020
In reply to bergfuhrer: Is that really a thing with invisible stressing past the elastic limit of the shaft?  Stressing past the elastic implies stretching to me (correct?), and while this has damaged the lobe (crstal, pebble?) does it imply a larger force applied to the stem than normal?

 nikoid 18 Jul 2020
In reply to bergfuhrer:

I think you're overthinking it!😁

 beardy mike 18 Jul 2020
In reply to bergfuhrer:

Now we have micro cracks in 17/4PH stainless? Well I never. No. Just no. Firstly the elastic limits of 17/4PH is extremely extremely high, especially in the 900 state it's in in these axles. It's the equivalent of some of the highest strength carbon steels, and there is very little chance that it's gotten even close to the sort of load required to stress it to that point. Secondly if you know about steels of this nature, you'd know that Youngs modus is high, i.e. it is quite flexible for it's stength - yield strength is a long way from Ultimate Tensile strength, unlike the 6082-t6 aluminum that the lobes will be made from. If it bends in-elastically you will not form cracks until shortly before it breaks, and it will yield a long way before it finally thins and breaks. If there is going to be a problem, it will be with the lobes a long time before the axles.

cb294 18 Jul 2020
In reply to Kevin_Daniel_Garvey:

If it were mine I would file it off and keep on using it, as long as the axle mechanics feel OK (clean movement, no wobble....).

CB

 timparkin 19 Jul 2020
In reply to Kevin_Daniel_Garvey:

Out of interest, was the cam inserted horizontally in a vertical crack and then pulled down in a fall? That sort of torsion/twisting can generate large forces because of the leverage but the actual force on the cam isn’t large...

cp123 19 Jul 2020
In reply to bergfuhrer:

> If the fall was enough to damage the cam, then it is worth having DMM check it over. It is possible the shaft that the cams rotate on has been invisibly over stressed past its elastic limit, so that nxt fall it fails.

If it is stressed past the elastic limit permanent plastic deformation will have taken place and the axle will not return to its original shape once the stress has been removed - you will therefore be able to tell if this has happened.


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