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DIY parts moderator first attempt. An experiment.

Hello, I made a few DIY Mods with plastic tube, The only thing required was getting the Thread adapter central in the Tube, Exit end was 6mm which was easy to drill the plug, Curlers and felt internals, The better mods are the oil filters but only around 25 mm
 
Just to point out that there's a lot of redundancy in my current baffle arrangement. The Hogan only has the two centre baffles. My end baffles are only there for alignment purposes really. I could and should redesign without them and see how it goes. If I had put a groove into the face of the threaded bung I could push the inner tube into it and keep things concentric at that end. It would be easy to fit the inner tube to the turned aluminium muzzle end too with suitable dimensions.
 
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Bore was a bit tight. Should have known as it usually prints a tiny bit undersize. I've drawn up a more compact mk2. It should fit in the vice better. Shorter bolts employed too which is helpful. See how this goes.

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Fifth time's the charm.

Finally got a working model. It was tricky making it as small and quick to print as possible while still allowing clearance for the screws and bolts as they can't stick outside the hex. My suck it and see approach wasn't very efficient at solving this. Also realised that the nut recesses would be better off being hexagonal rather than circular but it works. I've made corrections for iteration number six if I ever print it.


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This version six for captive nuts that won't spin.

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Another angle, same thing.

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It should make indexing the 120 degree spaced grub screw holes a breeze. I could start a production line😜
 
Yay! It works rather well. This is it posed after I'd done the work, as you can see the grub screw in place already. The purple thing on the vice is an adjustable stop, allowing the block to go back in the same place left to right in the jaws. The top point of the hex was used to centre the drill up, which was a bonus.


I've printed out the number six hex version but the previous version, number five, was used.

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nice idea re centering the drill on the point of the hex , but as your printing it how hard would it be to print in a feature to your clamp , say a drill tip cone or even an actual hole the size of your drill give or take ?
 
sussexa said:
nice idea re centering the drill on the point of the hex , but as your printing it how hard would it be to print in a feature to your clamp , say a drill tip cone or even an actual hole the size of your drill give or take ?
Click to expand...
Exactly, then you wouldn’t need the additional stop.
 
Yeah it did occur to me after I set up to drill. It's no problem at all to add a small shallow semicircular hole on both sides of the print for the drill indexing rather than going by eye. Just another two and a half hour print. I'll get the model updated later. Don't fancy drilling through the print as a drill guide itself though. I prefer to see what's going on and the height of print would take up a lot of the length of the drill.

I paid a lot of money for that tiny stop. First time I've found a use for it.
 
unless just set up for the photo with that much stickout from the clamp any vibrations with no support underneath ?and no i wouldnt drill through clamp either , was just suggesting a hole your drill size would make quick centering tool
 
Yes, I do need to be more mindful with regard to my set up. Too eager to get stuff often.
 
Richiew said:
Yeah it did occur to me after I set up to drill. It's no problem at all to add a small shallow semicircular hole on both sides of the print for the drill indexing rather than going by eye. Just another two and a half hour print. I'll get the model updated later. Don't fancy drilling through the print as a drill guide itself though. I prefer to see what's going on and the height of print would take up a lot of the length of the drill.

I paid a lot of money for that tiny stop. First time I've found a use for it.
Click to expand...
Just drill the clamp
 
Stuck a drill-liner-upper dimple on the model. In Fusion 360, I had to move the two parts together, create an offset plane level with the apex, sketch a circle for placement and finally use the hole command. It's been good practice if nothing else.

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Two baffles and three 40mm tubes have been provisionally printed for the innards. The end piece has a 18mm step on the ID which the tube fits into. The opposite threaded end piece which screws to the barrel will get the same treatment so everything stays aligned and in place. The carbon fibre tube is a little over 6 inches long. One of the 40mm tubes will get reprinted to a custom length, allowing everything to fit nicely with no rattles once the threaded bung has been turned

I just need to summon the energy to get back on the lathe.

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Braved the garage last night and turned the threaded bung end. Tube glued up and left to stand overnight. I hit the correct length for the inner cage part at the second attempt this morning. Ended up with 40mm 45mm and 40mm cages. Now I know the total length required, I could reprint in different lengths to mix the chamber sizes up. Those original sizes were just for convenience of getting something built.

Total finished weight 83g. Overall length162mm.

I haven't tested for accuracy yet as we have strong winds today. I have put a mag of 12 pellets through it in the garage at a target three feet away just to check for any clipping issues and it passed with flying colours. Dry fires have been compared with the bigger version and they sound about the same as far as I can tell. I realised what a good job it was doing after dry firing without the moderator. It reminded me how loud air rifles can be in enclosed spaces. It would be interesting to get an objective sound measurement comparison to see how well or badly they are actually doing

It's 41g lighter than my larger carbon effort and 65g lighter than the Hogan so that's a win. The Hogan has a steel tube and steel ends which is where the weight is. The Hogan internals themselves are very light.

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Posed with bigger brother.


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I can't quote or even remember the original source but it suggested that chambers should be diferent lengths and that they should use the square root of 2 as a multiplier. For a 3 chamber system this gives ratios of 1:1.4:2. I don't know if there is any scientific basis for this but it is something I have used as it seems just as sensible as anything else.
Ultimately comparing performance is not really possible with the kit that ordinary people, that is not acoustic scientists, can afford. Also you have 2 different requirements which may or may not actually differ since some of us wish to quiten guns vecause of neighbours while others are interested in hunting. Certainly human hearing is very different to that of animals in terms of frequency response and it may be that something which seems silent to us is exteremely loud to a rat.
However you look at it the experimentation is fun although it can become addictive and expensive.
 
If I reuse one of my 40mm cages then 28mm and 57mm is a close approximation. Plenty of spare felt.
 
For what it's worth...
I have been making and experimenting with moderators for a while now
So from my experience;
  1. The the larger the volume the better attenuation
  2. The distance between baffles needs to be logarithmic large near the muzzle ( apart from better attenuation, you get the least disturbance to the pellet flight)....the aim is for smooth transition through the moderator.
  3. The transition ( the baffle hole thickness) needs to as thin as possible ( again, least impact on accuracy)
  4. The best material to use for the dampening material, I found, can be found cheap on AliExpress (Graphite Felt Black Welding Protective Blanket).
  5. Making the holes very small/tight will risk clipping as well as causing pellet transition differential pressure that would impact the accuracy....the tighter the hole, the more impact the differential pressure around the pellet will be.
  6. I use heat-shrink on the moderator body, cuts down the HF sound component.
These are my findings, you can do as you please . All I can say is: My moderators are as quite as a baby's burp or a soft thigh slap.
No: I do not make moderators to sell.
 

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I'm using the graphite felt already. It was sold to me as that stuff anyway.
I can redesign the baffle around the hole. To make it thinner. That's an easy thing to try.
I use a neoprene cover on my mods so that may do a similar thing to the heatshrink?
 
Richiew said:
I'm using the graphite felt already. It was sold to me as that stuff anyway.
I can redesign the baffle around the hole. To make it thinner. That's an easy thing to try.
I use a neoprene cover on my mods so that may do a similar thing to the heatshrink?
Click to expand...
yes
 
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