Well dang .... major Diana 56 failure

[Petey]

I thinks that's equal to a "Full Diaper".

[Hanabata808]

We got the piston Robert!! Whew!!! Thanks to Clark on the Dianawerk who pointed me to the post on the yellow, and to Scott for getting in touch with the seller.
Totally sick that this happened....cannot tell you how great that rifle was shooting after Scott set her up.
The ONLY pellet I ever used in her was JSB Heavies...period. I take very good care of my guns and see absolutely no reason for this to have happened.
I did a search and found another thread that stated the same exact problem with a brand new 56.

That's awesome you got the replacement piston!
When you examine the broken part, can you somewhat determine what kind of flaw caused it to fail?

...
BTW, that may be the most beautiful yard I have ever seen.

Thanks, nice of you to say. 

[Motorhead]

If there is a golden under lining to all this .... it very well maybe ( Given compression chambers concentric ) that the R&D of others being an O-ring type piston seal and precision tolerance piston further increases this rifle shooting potential
Tad bit or rework involved and some careful bore gauge measuring to see if compression chamber is actually round and suffering any degree of taper ? .... Lucky to have access to buds with SUNNEN hone machines if the need arises 

Deep breath ..... tell one's self, Toy guns toy guns 

[michaelthomas]

If need be.......I have access to several Studer cylindrical grinders, too......in case that need arises.

I hope it doesn't for you, though.

Mike

[Sfttailrdr46]

Tough break Joe no pun intended that reall not worthy I know you liked the way that rifle shot

[chuckinohio]

  Exactly, that 56 was a hummer at long range, what a PITA to have that happen to it.

  But, looking to the bright side as mentioned above, the HMO piston might wring out some more performance in the old shootin iron for ya Joe.

[palonej]

I so appreciate everyone's help and concern. If you follow this thread you will find what makes this place great!! Everyone looking to help in anyway they can. Awesome!!
Little patience, and faith in the Motorbada$$!!!! Like Scott says....toy guns..toy guns....

PS Does anyone have an idea on how this happened or what would cause this failure?? The ONLY pellet fired is the JSB 10.3 domes. AOA says light pellets will cause this...they were NEVER fired from this gun. Lotta lead thru her, but don't think this should've caused this issue. Shooting laser beam accurate one shot....the next...no lock up.
??

[Motorhead]

Fatigue pure and simple my take on it.  Cracks origin clearly at root of the knurling which would be / is a stress riser being there at all.
As a spring guns hammer falls that long lock post becomes essentially a tuning fork vibrating down it's length with every shot taken. 

Not an engineer, but clearly seeing first hand different methods manufacturers use in attaching there cocking rods to pistons head, this Diana way pretty obviously is designed less than optimal

[WHITEFANG]

I have heard of this but never seen it. Is the stem threaded  or just pressed in the piston head? Just not a good thought of that happening.?Good thing for the RWS BEAR TRAP working while cocking .
I wonder if it snapped after firing or just let go after cocking. That would have bent a trip on on the break barrel and the gun loaded, well would have fired on either type gun.
Safety on or not it would have fired if it just let go.
 

[Motorhead]

Can NOT tell how rod was attached being HEAD of piston still has the END of the rod within it.
Knurling present indicates little being it is lengthwise, load placed upon the rod and if pressed in would just as easily pull out 
Some thing else in the design holds the rod in place and that detail is hidden from view by that portion still in place ... unless I cut piston in half to get a cross sectional view can only guess 

[palonej]

I have heard of this but never seen it. Is the stem threaded  or just pressed in the piston head? Just not a good thought of that happening.?Good thing for the RWS BEAR TRAP working while cocking .
I wonder if it snapped after firing or just let go after cocking. That would have bent a trip on on the break barrel and the gun loaded, well would have fired on either type gun.
Safety on or not it would have fired if it just let go.
 

Hey Fanger!!
Was shooting perfectly. Took a shot, on target, cocked gun and it did not feel or sound right at all. Tons of pressure when trying to return cocking lever to closed position. Held back on it, released near trap, closed lever. Lever would not stay in place, flopped open bout an inch. Pulled trigger and got nothing but a small click.
No warning or sign of a problem till she failed.
I e mailed Diana, but haven't heard a word. AOA wants nothing to do with the issue.
Thank God for the Motormouth! Not sure what my options would be otherwise.

[WHITEFANG]

I always thought they were pressed in but never new for sure. I do know you can drill and pin them when they get loose or just drill a plug and then mig weld the plug. After that you can clean the weld up and you are tight now. By the picture, which it is hard to tell, looks like it had a stem  type setup. At the brake is there any type of a void on the end of the stem where it broke?

[WHITEFANG]

I posted on top of you. So by what I understand the thing let go maybe after the shot. The you cocked the gun the stem stayed in the trigger group. The clicking was the trigger letting go of the rod that was still in place. I know when I remove the spring and play with a spring setup or trigger the guns will click to release the piston with no spring. Then you just pull  the psiton forward a tad and re set the trigger. Must to have let go after the shot. Either way it is bad deal but if it had let go while cocked on any of the guns the thing would have fired. Just think when you load one and set it down for the next bird or what ever or just picked the gun up and it went of. HOLLY COW!!!! THAT IS WHAT BOTHERS ME ABOUT THE STEM ON THE PISTON GUNS.
You were lucky!!!

[palonej]

Yup. This is a PITA, but a trip to the hospital would be much worse!! Also, judging by the amount of pressure on cocking lever...if that thing snapped back fingers would go flying.
Is the piston we picked up just like the stock one that failed?? Any differences??

[Paul68]

I THINK the rods in these pistons is not really a true press fit. The knurling, at least in the 34's, 350's and clones seems to serve more to keep the rod from rotating, but is probably a bit of an interference fit when first put together. The rod is installed in the cap before the cap is crimped into the piston body. I THINK it is locked in place by a sort of lip on the rod end that prevents pullout, which is why these rods can be sort of loose and move around without pulling out. If I'm right, it looks like this one snapped the end lip off.

[QVTom]

My take is that the straight knurl is used to reduce the need for a high tolerance interference fit.  If a proper press fit tolerance and finishes were used, I'd bet the knurl would be unnecessary.

Tom

[Booger]

Come to think about it, when I got my D-34 T-06 tuned, my tuner told me something about a piston problem some RWS T06s were having. He said they were pressed on and he had a fix for it if it was needed. He said something about tapping it. In my case it was not needed. I am not mechanically inclined so it just flew right over my head and never thought anything about it until I heard about Joe's loss, and Motorheads resurrection.

[palonej]

Yup. Mine is the third I've heard of with a similar problem. I e mailed Diana last week and haven't heard back from them.

[Booger]

Yup. Mine is the third I've heard of with a similar problem. I e mailed Diana last week and haven't heard back from them.

Please keep me informed, even if it is with a PM. If support is not given to you, I will not give them any more support with my $$$. I know I am just one person, but I am one person who does not want to be promised a gold mine and get the shaft instead.

[palonej]

Will let everyone know what the out come is Jess. I sent another e mail this evening. I also e mailed Weihrach the same day. I got a notice that e mail was received and got an answer the next day. They are also sending me a free hat just for reaching out to them. Hope I at least get a response from Diana.