What are the "flanges" on a Rolling Block? Not familiar with the term as applied to a Rolling Block action?

Quote:


I wouldn't bet on that. Owning a rolling block in a higher pressure (than BP) cartridge, my ears always perk up when I hear of a catastrophic failure in a rolling block. I'm no expert on the action, but I don't recall ever reading of the pin failing. It's always the breech block at the ring of steel around the pin.

I don't think the stress/strain solver in SolidWorks is sophisticated enough to predict the failure point (and certainly not to 5 significant digits). For such work, a solver such as LS-DYNA, which can handle plastic deformations, might be needed. 

Also, unless you've talked with Tippmann and he's given you reason to take that 52 ksi pressure rating as the stress limit in the steel, I'd assume he's talking about cartridge pressure. Dave Higginbotham always rated his action in terms of cartridge pressure. He didn't care about case (piston) diameter, but as you realize that is a critical part of the equation. 

One reason I don't think your action will fail is provided by Uberti. They offer their No.2 size action in .357 and have so for decades. The CIP rates this cartridge at 44 ksi and Uberti will proof it for that. The SAAMI .223 (about the same diameter) is 52 ksi, but your No.1 sized action is much beefier than their little No.2.

I may be reading it wrong, but I think he’s talking about the same location we are.

The 1/4" gap he said was for an extractor. I took it the Tippmann is using a rotary extractor in the middle of the breech block instead of on the side. I think (but am not certain) Uberti does this for the rimfire version of their No.2 clone. He also said the breech pin passes through the "flanges."

Regardless, in this image of a breech block:

(You need to Login or Register to view media files and links)

the typical failure point would be at 12 o'clock from the pin centerline, where the breech face ends and a ring of steel surrounding the pin begins.

See the pics of Tippman breech block and extractor, definitely different than solid blocks of originals
Weak spot is the the upper intersection of the pivot "flange" to the block.
KWK, trying to verify Tippman steel alloys and 52 kpsi number, the calculations are based on this number, even though it seems low for cast steels (most are in the 60-110 kpsi), it is still positive in safety factor, 
And respectfully disagree on Solidworks not being capable of solving the location of potential high stressed areas in classical or plastic deformations, SW solves to 8 places, which is insignificant in the load range we are talking about.
Please provide an example of the LS-DYNA solver and let's compare.

LS-DYNA is expensive, and I have no need to acquire a license. It will solve for multiple parts with clearances and handles plastic strain. It also runs dynamic loads. Examples of what it can do can be (You need to Login or Register to view media files and links).

As to "solving the location of potential high stressed areas" yes, of course, Solidworks will show "potential." Once plastic deformation begins near a corner, it's accuracy may start to fall off. Dassault is a big company with a need for accurate stress analysis, so maybe.

I'm not an engineer, I've never owned a rolling block, but I do think I more or less understand what's being debated here.  Therefore, if you'll please excuse my ignorance, what is the purpose of the two screws right above the pivot hole in the Tippmann breech block?   And why don't their holes increase the potential of the block cracking at that critical corner?

Bill Lawrence

Bill, the plate is Tippman's approach to a two piece firing pin The plate covers a cavity for a headed pin, had to mod this one for the .223 , a lot smaller
The plate adds thickness, but in the model I eliminated it since it is not welded to the rest of the block, the stress point however stays the same at the change in geometry area for the flanges to the block, sharp point'
The two mounting holes don't appreciably affect the max stress as they are above the interacting stress plane and the forces coming off the flanges from the pivot pin.  Most of the breech block is in compression and hugh failure margin numbers for this.
The stress concentrations are in the flanges and even in the original blocks as the face of the breech is loaded in compression and the flanges/pivot hole mass is subjected to massive tensile stress trying to pull it apart and also applying large bending loads once the breech block hits and stops on the hammer roller face. This bending load is concentrated in the least cross sectional area of the flanges, or lower solid block.
Failure would probably be stretching of the area around the pivot pins, either very long term fatigue  crack or just plain stretching (yielding) till tolerances of the breech and hammer rollers would not work together.
Depending on the pin material, numbers indicate they are possibly the weakest link, might bend, crack or fail before large scale failures of the blocks.
This make any sense?