Three Maxim inspired short, fat LDCs: .177 / .22 / .25

[subscriber]

This family of short LDCs was inspired by Maxim's patented designs from 1909.  My .22 version was proven very effective in the thread "Taming the bark of an Avenger".  See images below.

The designs are scaled by caliber, with the .177 version being the smallest.  The .22 version stretches the diameter proportional to the caliber.  The .25 version is scaled on diameter and length.  All have 1/2 20 UNF threads tuned for 3D printing.  All have tapering wall thickness to make them lighter, while having sufficient strength to resist air pressure and bending under gravity (without living in a metal can).

The designs have permanent supports inside, that while occupying some volume do not interfere with the air flow - see last image.  The parts need to be printed standing on their front ends, with the threads pointing up away from the platen.

This wetransfer link expires on 13 November:
 https://wetransfer.com/downloads/862d5dfac4e7c9150073df39dfec0e2c20221107013017/1854d65b59a8fd97cbdf9320ee5433ba20221107013039/9f9c31?trk=TRN_TDL_01&utm_campaign=TRN_TDL_01&utm_medium=email&utm_source=sendgrid 

So, if you feel inspired, download the STL files before the 13th.  I have grouped all three designs in one zipped folder.  If you have no interest in some of the 3 parts, just delete them and the zipped folder, after you have the version/s you want.

My suggestion is to slice the parts such that the walls are 3 or four layers thick, with 50% infill selected.  Or 100%, if you prefer.  Turn supports off in the slicer. 

The .177 version is just over 4" and just over 2" in OD.  The other two versions are scaled up from that.

[WobblyHand]

Thanks for posting this!  I have a printer coming in this week.  Maybe by next week I will try one of your designs.  I'll need to make an adapter, but I think I will machine it on my lathe. 

What CAD program did you do the design in?  I took a quick look at the stl files and I am still trying to wrap my head around the basic shapes in the design.  I recently learned FreeCAD (this January) and am puzzling on how you did the basic model.

[jackssmirkingrevenge]

Nicely done!

You've probably considered this but I wonder if it would make sense to have threaded modules that would allow the user to customize the length, something like this:

[SILENT SQUIRREL]

Now that's incentive to learn how to print!

[subscriber]

Bruce,

I used the basic version of Solidworks 2015, but you one could create those shapes with any version or Solidworks, and probably most 3D CAD programs.

The internal toroidal shapes were created by rotating a profile to add material.  See sketch profile rotated around green bore axis line below.  The longitudinal ribs were added by the common CAD process of extrusion.   The circumferential ribs were added by rotating a profile that defines their dimensions.  This was done in several steps.

There are tutorials on youtube for all CAD packages.   The principles design are the same for all of them, although the instructions differ.   Once you grasp the basics it is actually not difficult.

[subscriber]

Jack,

Stacked baffles where the user can vary the length are a great idea.  Also, because each print is only one baffle tall, you have a much shorter print time and smaller material use, should any given print fail. 

Are the parts in your image injection molded plastic, or metal?

It is possible to stack this design concept.  I have done similar stacked designs that live inside a shroud.  As the intent now, is to make the baffles strong enough to live outside a tube, my concern is droop at each joint, leading to misalignment with the barrel. 

Now, if the baffle is half as long as its diameter stability should be improved.  Also, I think I would include conical nesting features that forces strong concentricity and angular alignment.  The threads would need to be robust for 3D printed parts, and they may take a fair amount of room. 

Now you have given me a challenge....

[jackssmirkingrevenge]

you have a much shorter print time and smaller material use, should any given print fail.

 

Anyone who's ever used a 3D printer will certainly welcome that

Are the parts in your image injection molded plastic, or metal?

Machined metal to my knowledge, but if you look up the SIG MODX series they use a similar design and are 3D printed in titanium.

my concern is droop at each joint, leading to misalignment with the barrel.

 

Look up the "Demolition Ranch" channel on YouTube, they went crazy with stacking a similar model and even with metal parts it look a remarkable amount of segments before they got a baffle strike.

Now, if the baffle is half as long as its diameter stability should be improved.  Also, I think I would include conical nesting features that forces strong concentricity and angular alignment.  The threads would need to be robust for 3D printed parts, and they may take a fair amount of room.

You could also avoid threads and instead clamp the segments together using long bolts, if you look up the SilencerCo Osprey Micro it uses this method.

[subscriber]

Jack,

Thanks for your input.  Translated: I need to use a generous baffle bore diameter for caliber, to allow some misalignment.  After all, I am not printing the parts and not screwing them together.

Will check out demoranch.   That guy does crazy stuff that often seems wasteful to me, but destructive testing can teach one a lot.

Bolting together segments is another option, but unless you know how long a stack you want to use, the bolts have to enter at an angle, so each joint is bolted separately.   In contrast to that, your original suggestion has so much value that exploring and developing that stands out as the most obvious design path: 

Perhaps inch long baffles that can be screwed onto each other.  If four are not long enough, then try 6 or 8...  The front and rear caps are obviously unique parts; so a set would be distinct STL files per caliber, with multiple copies printed of the "middle" baffle.

[customcutter]

Thanks, Sub:

I downloaded the files.  Does that mean I'm going to get a visit???

[subscriber]

Ken,

At this point, having information contained in a patent from 1909 is still allowed:  https://patents.google.com/patent/US916885A/en?oq=916885 




It is what you do with it that might bring a visit.  Keep it off PBs - unless you got the paperwork approved first.

[customcutter]

Yeah, I thought about doing the forms, paying the taxes, setting up a trust and all many years ago when I got my thermal.  The way my remaining 2 brain cells function and constantly disagree about everything I'm supposed to remember, I'm glad I didn't.  Too danged many reg's/rules for this old man to keep up with.  LOL

[jackssmirkingrevenge]

I need to use a generous baffle bore diameter for caliber

Not necessarily, what you've suggested about conical nesting can virtually guarantee alignment without needed to allow for too much slack.

One other option to consider given the ubiquity of strong cheap neodymium magnets and the relatively low pressures in air guns is a magnetic lock with inserts that would be easy to twist apart but but hold together while firing.

[subscriber]

So, I spent several hours working on the extendible screw-on baffle version of the Maxim design.   Rather than a single cone for alignment, I was inspired to make it double sided.

The version shown is for .177, but it can be scaled up.

Still have to make the front and rear cap designs.

I think the "vaulted ceiling" part of the toroidal space will need some form of support to print.  As the design is open, turning on support in the slicer is an option.  I prefer to add permanent supports that are not intended to be removed.

First, I need a break....

[EdinGa]

Following... I really want a short can for a few of my carbines.

[subscriber]

Added front and rear cap.

Current version needs to be printed with supports on in slicer - see image for right way round on platen.  Will come back and add permanent supports later.

Will have to split zipped STL files per reply due to file size.

[subscriber]

Had to use wetransfer to upload files due to size, even when zipped.

Link will be active for 7 days:
https://wetransfer.com/downloads/53f6eaa93a1f18726b5a1cffa1c5b75720221109124139/365d7583a31bb38fcb8b95c4366a406f20221109124158/df5174?trk=TRN_TDL_01&utm_campaign=TRN_TDL_01&utm_medium=email&utm_source=sendgrid

This version needs to be printed with supports on.  Remove supports before use...

[subscriber]

It would be useful if someone printed the middle Maxim baffle to determine if it would indeed require printing with supports on. 

It may be a question of step size, but to me, any slanted overhang flatter than 45 degrees is a risk.  Especially if it spans more than 2 mm.    The exact sequence and path the material is deposited probably also matters.  So there may be more than one answer.

The image below shows the size of that curved "ceiling" that I think is at risk without added support.  Specifically the red "fan" 13 mm wide.

It would be great if these can be printed without supports turned on; or my permanent supports that are part of the design.

[jackssmirkingrevenge]

Very impressive, I like the alignment ring.

It would be great if these can be printed without supports turned on; or my permanent supports that are part of the design.

I suppose temporary supports would be a very minor inconvenience since they can be very easily cleaned up in a modular design like this one as opposed to a one-piece unit.

I have no reference for what lower end printers are capable of but wouldn't they prefer coarser threads?

[Kmanca1]

 
I don't have a printer......
but, I'd buy one of those.

hint, hint.

[WobblyHand]

Bruce,

I used the basic version of Solidworks 2015, but you one could create those shapes with any version or Solidworks, and probably most 3D CAD programs.

The internal toroidal shapes were created by rotating a profile to add material.  See sketch profile rotated around green bore axis line below.  The longitudinal ribs were added by the common CAD process of extrusion.   The circumferential ribs were added by rotating a profile that defines their dimensions.  This was done in several steps.

There are tutorials on youtube for all CAD packages.   The principles design are the same for all of them, although the instructions differ.   Once you grasp the basics it is actually not difficult.

Thanks for your detailed answer, appreciate it greatly.

Please indulge me a little further.  I understand the basics of 3D CAD.  I know about solids of revolution.  Trying to understand the long ribs.  For the longitudinal ribs, they go through and compartmentalize the cavities formed by the voids of revolution, so the gases have to follow a long path?  And that contributes to the sound attenuation?

My printer kit arrived today, so I am revved up about this.  Got to start building the printer tomorrow.  Got some starter PLA.  To arrive are a couple of spools of PETG.

Can you post a little bigger 2D sketch of the cavities?  Some of the dimensions are on top of each other and a bit hard to sort out.  I guess I could figure it out eventually, but would appreciate a clearer, easier to read view.  Thanks.