Any engineers know why the metal dangerously failed on DIana trigger

[Barryg]

We are awaiting Diana's explanation (they had better be quick)do
any metal experts on here have any ideas?
So far it seems a one off.
I thought that some of you DIana owners might be interested as it's a safety thing.
You can see the broken part in this thread.
http://www.network54.com/Forum/18447...en+T06+trigger

[bighit]

possibly powdered metal?

[crowbar]

It could be slag in the casting or the loud bang could be the rifle detonating upon firing blowing the piston
back and breaking the trigger catch.

[NickG]

looks like a sintered part to me , not a good part to be cost cutting on

[Modski66]

Shame that the pictures don't show the fracture faces, but my first thought is the lack of a radius in the corner where the crack appears to have initiated. There will be a high stress concentration in that area, and sharp corners don't get on well under high stress loads. Look up Liberty ships in WW2 and the original Comet aircraft design.
The part will obviously need to be hardened to stop the sear face wearing away, so any breakage on components of this type will be a brittle fracture.
Putting it bluntly, it's a design fault...

[bezzer]

Certainly looks a cast part, shame an end grain pic wasn't posted. No room for casting or treatment error when there is such a sharp angle on a part which becomes the weakest link.

edit- too slow....wot modski said

[Solvo]

It's impossible to tell without a high rez image of the face of the break.
Those pics show it failed on an obvious weak point (the 90 degree angle) however you cant tell what caused the failure without seeing the metal composition and type of failure.

If it's a sintered part it's a terrible design flaw especially given the lack of a relief radius on the angle.

There could be any number of issues shown in the face though. Two tone radial would show a gradual failure initiated by older damage. but there could be anything from contaminates and corrosion to air bubbles shown in the break.

[blooregard]

I might be wrong here but I wouldn't think anyone would use Sintered metal on a sear.

We are awaiting Diana's explanation (they had better be quick)does
any metal expert here have any ideas?
So far it seems a one of.

Why do you need a quick response? Seems like the issue is resolved and as you say it is a one off. Doesn't matter what you are shooting, if there is the potential for something to come out of the business end it should be pointed in a safe direction so no harm done as long as you are handling the rifle safely.

[airgunnut]

possibly powdered metal?

You beat me to it, have they started using metal printing? (it starts off as a tray of powdered metal) I'm assuming if this is the case then the hardening and tempering process is substandard or the printed parts are under more stress than the printed metal can stand.

[Solvo]

Printed metal is not in widespread use and certainly not likely to be found in a production system for a relatively simple part.

Printing is very slow and costly compared to standard manufacturing and very much a niche market.

[bighit]

Printed metal is not in widespread use and certainly not likely to be found in a production system for a relatively simple part.

Printing is very slow and costly compared to standard manufacturing and very much a niche market.

its used in knife making so I guess it may be used on many things.

[pastie]

I might be wrong here but I wouldn't think anyone would use Sintered metal on a sear.



Why do you need a quick response? Seems like the issue is resolved and as you say it is a one off. Doesn't matter what you are shooting, if there is the potential for something to come out of the business end it should be pointed in a safe direction so no harm done as long as you are handling the rifle safely.

That design is prone to failure, as there is a stress raiser in the right angled corner...it is where the crack propagated from. If this is made with any type of secondary flaw such as a void in the steel or any imperfections / impurity, then it will do exactly as it has here.

One would hope that this Safety Critical component is not made of any Sintered or Cast process, as that would surely result in a metal part not fit for purpose if any minor flaw was present.

Take a look at HW Sear, which is a very much tried and tested piece...it has no significant right angle to act as a stress raiser.

Diana should look at this as a matter of urgency. If there was an accident then they would have liabilities I suspect.

[NickG]

If It is sintered ,the hardening would occur at the same time

[bighit]

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Diana could be getting them made outside the factory .

[Barryg]

Diana should look at this as a matter of urgency. If there was an accident then they would have liabilities I suspect.

And they can't say that they didn't know about it now it's been reported.