Author Topic: XS60C PCP Repeater project (Read 455580 times))

westtexasrancher · « **Reply #740 on:** January 08, 2015, 10:13:46 PM »

Man I love these kinds of threads.

ali · « **Reply #741 on:** January 09, 2015, 04:42:46 AM »

ali · « **Reply #742 on:** January 09, 2015, 08:58:08 AM »

This is what we had discussed so far right?

This is what I understood about what we talked about with Bob. With the 'screw head' pass the OD of the aluminum tube, the shear area (accordingly) is the plane area of 'L-2' and 'L-3', that is,

A2= L-2 x 10mm = 2.5mm(thickness) x 10mm(tearing distance) PLUS
A3= L-3 x 10mm = 2.5mm(thickness) x 10mm (tearing distance)

A (overall) =0.0775 sq. in. x 4(number of screws)
A (overall..Bob) = 0.310 sq. in. (Bob's calculation), punching shear principle same as 'square peg' that you've described.

But how about if like this,

In the picture here, i moved the screw inside the tube and fashion it in a curve style so that it is just 1.25mm attached inside the tube. So now, there are already 3 plane areas that are in shear right? 'L-4', 'L-5', and 'L-6', hence we have,

A4 = L-4 x 10mm = 8mm( hole diameter) x 10mm( tearing distance) PLUS
A5 = L-5 x 10mm = 1.25mm (thickness) x 10mm (tearing distance PLUS
A6 = L-6 x 10mm = 1.25 mm (thickness) x 10mm (tearing distance)

A (overall) =0.16275 sq. in. x 4(number of holes)
A (overall) =0.6510 sq. in , this is how I see by applying how you calculate it. Isn't the overall value (0.6510 sq.in) greater than the original calculation you've got (0.310 sq.in) ?

Maybe I missed something.

QVTom · « **Reply #743 on:** January 09, 2015, 01:45:41 PM »

Quote from: ali on January 09, 2015, 08:58:08 AM

This is what we had discussed so far right?

This is what I understood about what we talked about with Bob. With the 'screw head' pass the OD of the aluminum tube, the shear area (accordingly) is the plane area of 'L-2' and 'L-3', that is,

A2= L-2 x 10mm = 2.5mm(thickness) x 10mm(tearing distance) PLUS
A3= L-3 x 10mm = 2.5mm(thickness) x 10mm (tearing distance)

A (overall) =0.0775 sq. in. x 4(number of screws)
A (overall..Bob) = 0.310 sq. in. (Bob's calculation), punching shear principle same as 'square peg' that you've described.

But how about if like this,

In the picture here, i moved the screw inside the tube and fashion it in a curve style so that it is just 1.25mm attached inside the tube. So now, there are already 3 plane areas that are in shear right? 'L-4', 'L-5', and 'L-6', hence we have,

A4 = L-4 x 10mm = 8mm( hole diameter) x 10mm( tearing distance) PLUS
A5 = L-5 x 10mm = 1.25mm (thickness) x 10mm (tearing distance PLUS
A6 = L-6 x 10mm = 1.25 mm (thickness) x 10mm (tearing distance)

A (overall) =0.16275 sq. in. x 4(number of holes)
A (overall) =0.6510 sq. in , this is how I see by applying how you calculate it. Isn't the overall value (0.6510 sq.in) greater than the original calculation you've got (0.310 sq.in) ?

Maybe I missed something.

Your second illustration... Is this a blind hole? If so there isn't much point in the design as the parts can't be assembled. If it is a thru hole the same tear out criteria applies, but you have reduced the bearing surface of the hole and it is likely that the tube material would yield in compression. Which occurs first is dependent on the bolt head diameter and hole placement from the end of the tube. Both modes of failure can potentially kill so it is best to get it right or copy a design (exactly) that is already proven safe.

Tom

rsterne · « **Reply #744 on:** January 09, 2015, 01:48:45 PM »

I can't see a practical use for that setup, but it seems you may be correct for the shear area.... HOWEVER, you have now reduced the BEARING area of the screw head by 50%, so instead of a 2.7:1 safety margin you are about 1.35:1.... That is low enough (under 2:1) to be subject to fatigue, so WILL eventually fail.... In addition, there is an increased possibility of the tube stretching outward over the head of the screw (ramping outward), and failing in hoop strength (tensile)....

Overall, I see no point in continuing along that line, sorry....Beyond that, I agree with Tom, you can't assemble it....

Bob

ali · « **Reply #745 on:** January 09, 2015, 02:26:14 PM »

It's a true hole Tom. How can I place the screw if it's a blind hole,

Ah yes, the bearing load. Good day.

stalwart · « **Reply #746 on:** January 09, 2015, 05:01:25 PM »

QVTom, have you figured out how much pressure the XS60 bulk cap retainer can handle? Would love to know...

ali · « **Reply #747 on:** January 09, 2015, 05:46:48 PM »

rsterne · « **Reply #748 on:** January 09, 2015, 06:10:53 PM »

Your bearing area calculation for the thread is incorrect, you only used the contact area of ONE thread, you have to use the full engagement depth, the same as you do for the shearing force on the threads.... Your calculation for the thread shear is also incorrect, you used the major diameter, you need to use the pitch diameter....

Your comment about bearing load not being important is just plain UNSAFE.... A soldered connection relies on the shear strength of the solder, there IS no bearing area....

Plus, your previous diagram showing the crowned head on the screw is wrong as well, because when you rotate the screw to install it, the head must be a body of rotation, so the contact point with the pocket in the tube would not follow the top of the profile, but the edge.... The edge is very close to the ID of the tube at the center of the hole, drastically increasing the possibility that the tube would stretch and slide up over it.... a VERY dangerous situation....

If you are an engineer, I respectfully suggest you need to go back to school, because the designs you are suggesting, and your understanding of them, leaves a lot to be desired, IMO.... I'm not trying to insult you, but I will no longer discuss this stuff with you, I have better things to do with my time....

Bob

QVTom · « **Reply #749 on:** January 09, 2015, 07:14:46 PM »

Ali, you seem to be hunting for examples to support your position on tear-out and bearing surface calculations then MISS-APPLYING them. Like Bob I'm not trying to insult you but you really need to learn to accept the advise of the more qualified. This forum is a great resource for members of all disciplines and skill levels but it not a debating club. You have been offered lots of good advise, I suggest you play it safe and follow that advise even if you believe it leads you to over build your designs. Just think about a larger screw engagement vs the alternative.

Tom

QVTom · « **Reply #750 on:** January 09, 2015, 07:17:16 PM »

Quote from: stalwart on January 09, 2015, 05:01:25 PM

QVTom, have you figured out how much pressure the XS60 bulk cap retainer can handle? Would love to know...

Still waiting on me? LOL Could you please PM me the last drawing with all the dimensions and I'll give it a go.

Tom

ali · « **Reply #751 on:** January 10, 2015, 02:41:44 AM »

ali · « **Reply #752 on:** January 10, 2015, 03:13:23 AM »

rsterne · « **Reply #753 on:** January 10, 2015, 01:04:11 PM »

For dissimilar metals threaded together, you do the shear strength calculation using the pitch diameter, and using 60% of the tensile strength of the weaker material.... or 60% of the yield strength for a greater safety margin.... You must derated the area by 50% because through that plane (cylinder of pitch diameter) half the shear plane area is on each part (male and female)....

I assume since you haven't stated any qualifications, that like me, you are self-taught with the help of input from people in the field who know what they are talking about and have taken the time to share.... Its a great way to learn, provided you listen carefully....

Bob

NJMevec · « **Reply #754 on:** January 10, 2015, 06:58:35 PM »

So this little guy right here. The XS60C. It accepts MRod magazines with some mods? Hmmm...would anyone be willing to cut my receiver and barrel if I order one? I have plenty of MRod mags from my 22xx and this seems like a better version of a Disco as far as bang for your buck goes.

AmBraCol · « **Reply #755 on:** January 10, 2015, 09:10:04 PM »

Quote from: NJMevec on January 10, 2015, 06:58:35 PM

So this little guy right here. The XS60C. It accepts MRod magazines with some mods? Hmmm...would anyone be willing to cut my receiver and barrel if I order one? I have plenty of MRod mags from my 22xx and this seems like a better version of a Disco as far as bang for your buck goes.

stalwart is the guy to contact about this. He's been tweaking on these rifles and newing and improving them for quite a while - and has many satisfied customers.

ScarletFire186304 · « **Reply #756 on:** January 11, 2015, 08:49:45 PM »

Quote from: NJMevec on January 10, 2015, 06:58:35 PM

So this little guy right here. The XS60C. It accepts MRod magazines with some mods? Hmmm...would anyone be willing to cut my receiver and barrel if I order one? I have plenty of MRod mags from my 22xx and this seems like a better version of a Disco as far as bang for your buck goes.

stalwartarms.com

QVTom · « **Reply #757 on:** January 12, 2015, 06:52:22 PM »

Quote from: QVTom on January 09, 2015, 07:17:16 PM

Quote from: stalwart on January 09, 2015, 05:01:25 PM
QVTom, have you figured out how much pressure the XS60 bulk cap retainer can handle? Would love to know...

Still waiting on me? LOL Could you please PM me the last drawing with all the dimensions and I'll give it a go.

Tom

Ok, this is the nut as I understand it. The transition from the internal thread to the front face is suspect......... So if you can verify all these dimensions and post a picture that would be great.

Tom

stalwart · « **Reply #758 on:** January 12, 2015, 08:26:09 PM »

They vary in most dimensions, by quite a bit, and even the shapes vary. I had 2 at hand... the dimensions not exampled are within .002.

rsterne · « **Reply #759 on:** January 12, 2015, 09:59:46 PM »

The one I had here was 0.738" ID and 0.945" OD, the dimensions I gave Tom.... I don't think I specified an overall length, it won't matter anyway....

Bob

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XS60C PCP Repeater project

Author Topic: XS60C PCP Repeater project (Read 455580 times))