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RL180-Poor Man Blaster Rifle DLT-19


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I didn't have much luck with Netfabb, not much about it since AutoCad took over the project and it's flagged as outdated in my AUR (repository).  However, I did spend the day getting Nvidia 3D accelerated Docker containers working and was able to get FreeCAD and Blender working within the container -- which is pretty damn cool.   I was able to import an OBJ file that I found floating around the net.





Now I have no idea what I'm doing...  But enough for today.

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LOL..  can you figure out which icon is the clone tool in FreeCAD?




Clever... but I think we would all agree they got the wrong lid icon for a clone.  Should we open a bug report?

Edited by rl180
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Back to working on the next part of the Barrel Jacket.  I used the the hole template referenced in Astyanas' build thread for this section of PVC.



This template worked perfectly for me at 100% I did not have to rescale the image.  It's mounted in my vice ready to be drilled for pilot holes and then Forstner bit.




Two coats of hammered paint to add some texture:




A light black washing was then applied with a dry brush and rag.  (I'm not 100% thrilled with how this came out, I think I will add another layer of hammered paint and black wash it again.)




I took a 1.25 inch coupling and cut the length down to 1 inch.  This will be used to connect these 2 barrel jacket sections together.  The middle sight is built around the coupling.  The middle sight is one of the parts I had 3D printed so I won't do anything else with this part until that arrives as that 3D printed part may replace this one.




The image below is just a dry fit for now.  If I ever make another one of these, there is no reason the two PVC sections can't be made from a single part and this coupling is just lightly sanded to allow it to slide into place.  That would be a much stronger assembly.


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In looking at the diagram of how the barrel jacket connects to the receiver, in most builds it is made out of standard 1.5 inch PVC.  Before doing the standard build method I wanted to experiment to see if I could come up with something different.  Since the transition of this fitting is 1.25 inch PVC to 1.5 inch PVC I figured I would start with a 1.25 x 1.5 inch reducer coupling linked to the 1.5 male adapter which is the connection point into the gun body (upper and lower receiver) of my build.


This is what I tried first:



A] is the female threads cut off from the 1.25 x 1 inch slip x threaded reducer bushing.  It fits perfectly inside the 1.25 inch socket -- push it in all the way and the 0.75 inch PVC pipe fits perfectly inside it to keep it centered.
B] is the 1.25 inch x 1.5 inch reducer coupling.
C] is a small section of 1.5 inch scheduler 26 PVC pipe just to connect "B" and "D" together.
D] is a standard 1.5 inch male adapter which threads into the gun body.
You will notice that part "B" has a step between the 1.25 inch and the 1.5 inch, which is not consistent with the actual MG-34 design.  I figured I could make a smooth slope using my belt sander, this is what I came up with:
It still is just too much of a slope.  If I keep sanding it down, I'll just end up with a pipe anyway... so I decided to NOT USE THIS PART and I started over.  Not everything you try works out.
INSTEAD of the part used above, I went back to the standard build model.  I used the the hole template referenced in Astyanas' build thread for this section of PVC. 
This template needed some tweaking to get to fit correctly, simply had to scale down until it wrapped around correctly, 87% was the magic number that finally worked.
I couldn't use the schedule 26 PVC for the connection as it is so thin that 1.25 inch PVC will easily pass through it without touching which means you can't glue them together.  So for this section I used standard 1.5 inch schedule 40 PVC pipe and then used my Dremel sanding bit to thin it out until 1.25 inch PVC pipe could be inserted into it.
Then drilled pilot holes and used my Forstner bit to complete the holes.
Where the 1.25 inch PVC would block holes in the 1.5 inch PVC once inserted was marked off with a pencil and removed with the Dremel sanding bit [not pictured].  I was not happy with my sanding job inside the 1.5 inch PVC. In some spots too much was removed which is easy to do with a Dremel. I joined them together with PVC glue but the connection did not feel solid.  I then "spot welded" around the connection with Gorilla Super Glue gel.  It was pretty solid after that.   But then between all the "spot welds" I used Apoxie Sculpt - two part epoxy and squished it into all the gaps and made a cap around the entire seam.
Once dry this seam was sanded down smooth.  
At the end of the Barrel Jacket, I cut off the end of the female threads from another 1.25 x 1 inch slip x threaded reducer bushing. It was too large to fit inside the male part of the 1.5 inch male threaded adapter.  I had to sand it down slightly to fit, then glue it in place.  Lastly using some Apoxie Sculpt around the edges to fill any gaps.
This will hold the inner barrel very snug and centered.  The external barrel Jacket is essentially complete now.  It is a little long by design to allow some room to trim when the center sight arrives (being 3D printed) -- these parts are still a few weeks from arriving.


I've ordered some Black Styrene Sheets and White PVC Foam sheets to start adding some details to the fittings on the barrel and I'll be able to start working on the main gun body (upper and lower receiver, custom trigger, etc) shortly.
Edited by rl180
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Thanks TK!



So I haven't been able to get good measurements out of FreeCAD.   So I switched to MeshLab (made a new docker container with Nvidia 3D acceleration and getting 300 FPS with the DLT-19 model).  What I couldn't figure out in FreeCAD I did figure out in MeshLab... scaling the internal arbitrary unit of measure to something you can actually use such as inches, mm, cm, etc.  


In my case, I had to scale the model by 0.78688 to get to inches. I came up with this using the following - the virtual measurement using the default unit was 61.17 (arbitrary unit) I know the MG-34/DLT-19 is 48 inches long (double checked with Wikipedia).  Simple division of 48/61.17 gives the scale factor.


Now when I measure the length of the model using the virtual tape measure I get 48.1 inches which I think is close enough.




So now to try some measurements.   When I look at something simple like the box cover over the ejector port I get 4x1x1 inches.  But I can't validate this with anything else, can someone else confirm this measurement?  I thought it stuck out more than one inch based on pictures I have seen:




NOTE:  After some more testing with Meshlab I was able to get a more accurate default measurement of 61.2775 which alters the scale factor to 0.783321774 which now gives me exactly 48.0 I'm happy with.  I'm getting ejector port measurements of 4.1x1.1x1.1 which is all within a fudge factor of my initial measurement.  

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Storage and transport of the DLT-19 is always a concern and having the cocking handle stick out makes the transport and storage more difficult.  My goal was to have an easily removable handle and a working slider - I want some movement of the handle and if I can get a click-click (front to back to front) even better and then have the handle stay in position until cocked again.  Cocking the handle won't actually do anything, it's just a fun thing to do.


I know many people use part of a flashlight for the cocking handle or just some PVC.  I have not located an ideal handle yet, but for now I'm going to use the 1/4 inch air compressor connector which is a reasonable size. The handle size referenced in MEPD is 2.25 inches long and with the attachment connector it will be exactly that size.  It will look even better once painted black.




The first thing to work on is to locate something that could be used as a track and slide.  Looking at my local home improvement store, this Defender Security 4 inch surface bolt (10cm) seems kinda close.  It was about $8, cheap enough to try.




Once I got it home and inspected it, I found out that the top slider only moved less than 1/2 inch (2cm) which was not enough movement to be useful -- but it did make the click-click sound I was looking for as it hit the stops on each side.  I wanted to use the full bottom track but only a portion of the upper track to extended the movement.  Unfortunately it could not be taken apart so I know I had to cut it.  Based on where marks were on the bottom of it, I estimated where I had to cut it to get the top rail and I wanted to save that little knob in case I could use it as a mount point for a handle.




Where to put the track for the cocking handle? On the gun body just above and behind the pistol grip, I sanded off some stuff that was in the way and cut out a grove where the track would be slightly recessed.




I tried to use this little knob as a mount point for a handle and it just awkward in size. It's a little wide and round everything just rolls off.  So I figured I'd cut it off and try to glue something else on.




After cutting the knob off and sanding it flat, I use liquid epoxy on 2 washers to give a nice wide flat surface. To make the cocking handle stay in place and yet be detachable I placed a Neodymium Super Magnet (12mm x 3mm) on top and let the epoxy dry overnight.



The idea here is that the cocking handle could be held in place just by using the Neodymium Super Magnet which worked great at first.  During a test fit the cocking handle went right in place and seemed to be working good until I tried to remove the cocking handle, the super magnet ripped the washer right off and broke the attachment point... should have thought of that, back to the drawing board!


No worries, I have another idea.

Edited by rl180
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I realized I needed to make something much stronger for the cocking handle attachment.  The Air Compressor quick release being used as a handle has a threaded connector side.  This seems like the logical thing to do. Instead of just using a magnet to snap it into place it will be a threaded connection.  Just screw on the handle and I think I can reuse this attachment should I find or make a better handle in the future (just have to modify any new handle to use 1/4 inch female threads).


I took another 1/4 inch threaded air compressor fitting and figured I could cut these threads off to make the base of the attachment point.




Oh let the sparks fly!




I have been impressed with these dremel cutting attachments, they have sliced through everything I have tried.




To hold the cocking handle in position when not being used,  will be the Neodymium Super Magnet discs (12mm x 3mm).  The plan is to have one inside of the gun body and one on the outside of the body.  The two of them make an even stronger magnetic field and will add decent resistance in moving a metal handle.  All the parts I used in this attachment point will be made from steel which is important not for strength but that all these parts need to have iron in them for the whole magnet concept to work.


Unfortunately all the Defender Security 4 inch Surface Bolt Kits are made from solid brass which is not magnetic.


This shows the Neodymium magnet disc installed and held in place on the inside of the gun body.  As a side note the two gray rails in the upper right side of the picture hold the inner gun barrel in place for a solid attachment. (I have not made the inner gun barrel yet, but I made these parts to fit the diameter of 3/4 inch PVC which will be used).




In making a new cocking handle attachment point, I cut a section off the top rail of the Defender Security 4 inch Surface Bolt Kit to be the same size I had used before on my previous attempt.  I then drilled a hole through the solid brass part wide enough for a small #6-32 oval head slotted steel screw to go through.   I then had to sand down the oval screw head small enough to fit under the slider and not get in the way of the track.




Once the customized steel screw was inserted through the hole a 0.25 inch steel coarse threaded hex nut was used to lock in place.  Then the steel 1/4 inch threads were wedged on top of the hex nut.  Then another steel hex nut, a steel locking washer and then another steel hex nut.



Lastly some black gel nail polish is used as a thread lock.  This stuff only hardens under UV light -- after a couple of minutes it was solid.


Edited by rl180
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This shows the track the slider will use for the cocking handle mount point.  The slider has not been added yet.  The screw on the left side is a small #6-32 oval head slotted steel screw which stops the slider from going any further and makes a nice click sound when the screw head under the slider hits it.  The screw is held in place with a 0.25 inch steel coarse threaded hex nut.  On the right side of the track is the outside Neodymium Super Magnet discs (12mm x 3mm) which will be typically hidden from view by the cocking handle. Once everything is painted black and the rest of the body work is completed I don't think this will even be noticed.




The cocking handle slider / attachment point has been added and does a pretty good job keeping the Neodymium magnet disc hidden.



Threaded on the cocking handle and its solid, stays right in place.  Pull back the slider which hits the stopping screw head produced a "click", push forward and the slider snaps in place over the Neodymium magnet for another "click".  I held the gun body vertical and it stays in place, jumped up and down and while it rattled a little the handle stayed in place.




It's not perfect, visually it's not a good match to what is used, I'll keep looking for something better.  The weight of the handle and the slight "play/wiggle room" between the track and slider does let the handle point downward slightly.  Nothing significant, but enough that I notice it.  I'll keep thinking about it, maybe find a way to correct it.

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The ugly factor was getting to me with that cocking handle.  I had to paint it to get a better idea of how it looks.   It's a little less ugly now.



I also picked up a handle used for GoPro cameras which was already black and fully knurled.  I was hoping it was a cheap hollow tube I could convert into a new handle but it turns out it was solid aluminum.  I don't think I'm up for trying to drill out aluminium.  I'll keep looking.

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Since the gun body is not based on the MG-34 style, the trigger is not even remotely close to the iconic MG-34 trigger, I can't ignore that.   I think I can make a closer match.



The first step was to sand down the forward ridges and remove the paint that was already on the trigger.




Next using Apoxie Sculpt - two part epoxy, I filled in the holes and added a little hump in the center of the trigger.



Gave the epoxy a coating of paint to seal it / primer.



Gave it a black wash to see how its looking.  Needs some more sanding and a little more detail work.



Installed and added a little screw to the center.  I have some ideas on how to add the "E" and "D" letters, I'll come back to that.


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This is the current opening I have for the ejector port.  It is about the right location to the MG-34 design and about the right size.  Some builds use large boxes some use much thinner boxes.




This is what would normally be inserted into that opening, on this NERF gun model, this is where the cartridge clip would be inserted.  This device would lock the clip in place and have an ejector button (right-side already removed).  The lines drawn is where I'll cut to get this about equal to the ejector port cover of the DLT-19 which is slighter longer than 4x1x1 inches based on what I can calculate on 3D models.



Had to make a jig on my chop saw to get a clean line as none of the sides of this device were actually flat which would have given me an angled cut.  Looks like my jig worked and I have a clean cut.




Using white PVC Foam board, I started to make sides for the ejector port cover.  To secure in place I use a combination of Gorilla Crazy Glue Gel (immediately tack in place) and Gorilla Glue which is an expanding foam glue which fills in the gaps that I have since the inner box walls have an angle but the exterior PVC foam board will not.



All four side walls have been added.  You can clearly see where the expand foam glue has filled gaps on the left side.



And a top cover put on. Worked perfectly.  However something about it kept eating away at me, the issue is I have seen builds that use a large ejector port cover like this and builds that use a much narrower one.  I decided this was too big for my build.



So I cut off about 1/3 of the unit and added a new side.   This is much better proportion for the build I'm looking to do.




But the A$$ that I am, cut the wrong 1/3 off.  Which left me 2/3 I couldn't use.  I want to trim and remove the bottom not the top. Since I lost much of the internal structure in my mistake I had to build in some internal support.



Gave it a coating of hammered metallic gray for a little texture.


Edited by rl180
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Since the ejector port cover was made smaller, I also had to adjust the gun body to make the ejector port area smaller to match.




Once that was all sanded down the new ejector port size looked pretty good.




The Ejector Port cover is not glued on yet.  I'll do that later on, for now it is just set to the side.




Since a significant amount of the gun body has been removed from this section I reinforced it with epoxy and more PVC foam board, I don't want this to become a crush point when the weight of the barrel and butt stock is added later on.


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TRIGGER - Completed


To finish up the Trigger, I've been thinking about how to get a decent "E" and "D" onto it.  No way I was going to try and hand engrave it.  That would just look to sloppy.  My wife does scrap booking and makes things out of paper and has a device called a Cricut Explore Cutting Machine:


It's like a plotting printer that uses a razor instead of an ink pen.  So instead of drawing patterns on paper it cuts patterns into paper, plastic, vinyl, etc.  Using adhesive vinyl paper we made some tiny letters.  The green background is the cutting mat with 1 inch square grid pattern.




These letters are tiny about 3/16 of an inch (4mm?) and hard to handle.  Also it is not that shinny in person, I angled the light to make them really show up in the camera. I might darken the letters a bit later on if needed.


Edited by rl180
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While browsing the isle of my local home improvement place, I was checking out some flashlights I could chop up that were cheap, metal and had the required knurled handle needed for a cocking handle.  I came across a Defiant Aluminum 65 Lumen LED Flashlight (1001 592 742) which was $9 and change.  Cheap enough to check out.


After disassembly of the flashlight, I only need the the main handle and the end switch housing where the ON/OFF button used to be.    I cut the main handle down to size and gave a few coats of black paint to cover up the logo.  Then I sanded down another female 1/4 inch air compressor fitting until it fit inside the switch housing.




Sanding down the female 1/4 inch air compressor fitting took some time.



Then cut off the section I needed.



It was a snug fit which just popped right into place with a little pressure.




I think this is an acceptable replacement handle and much closer match to what is expected.  It also weighs a bit less than my previous handle.


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The 3D components I uploaded and ordered prints from Shapeway.com arrived 1 week ahead of schedule.  All the prints look pretty good, nice and smooth.  



I'm very new to 3D printed stuff and it seems that many people smooth out the parts to remove gradient lines by using liquid 2 part epoxy made for 3D printed parts called XTC-3D. While I don't have problems with gradient lines I thought the idea of an epoxy coating making the parts stronger might be worth trying.



I mixed up a small amount (teaspoon) with a ratio of 2:1 of Part A and B.  Made a little working tray using a few layers of aluminium foil to hold the epoxy once it was mixed.  Just a light coating to smooth the surface and add a little strength to the parts.
Then I kept the parts elevated to allow any excess epoxy to drip off.  Waited over-night for it to dry.  The next morning I was a bit upset with the results.  I really felt it made the parts look worse and I probably didn't need to use it.  I spend most of the day sanding it off and digging out the epoxy from the detailed areas.
This is showing a mix of parts super glossy and sloppy from the dried epoxy and parts that I have sanded down to remove the epoxy.
And even worse, the parts no longer fit together once the epoxy was applied, I had to sand it off anyway.
This shows the 3 pieces assembled and held in-place with a few nails just for a visual reference of how detailed the 3D printed parts are next to a picture of a MG-34.   I'm not sure how I'm going to actually mount these 3 parts.  I'm going to look at the selection of nylon screws next time I'm at the home improvement center.
Edited by rl180
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To install the front sight base attachment I cut out this small section from the Recoil Booster housing.  I did this with my Dremmel using a combination of a small cutting bit and a grinding stone.




Test fitting of the front sight base attachment with locking lever fitting perfectly into a notch and front sight extended.  Again just using some nails to hold the parts in place and test the movement of the parts.




Test fitting of the front sight down.


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The mid-sight is one of the parts I had 3D printed.  I was worried about how it would fit with PVC parts.  It turned out to be so a little snug.  A 1.25 inch spigot fitting was a tight fit but would fit, but PVC pipe was just a little to big.  The PVC pipe had to  be sanded down and the mid-sight needed to be sanded a bit as well.




I'm not certain how strong 3D printed parts are, so I figured the liquid 2 part epoxy would be helpful.   I gave it a very light coating and hung it to allow any excess to drip off.  In the morning I found that the excess didn't drip off but made bulb like welts on the lowest part.  It never dripped off and I found too much detail had been covered up.  I spend a few hours sanding off and digging out epoxy from the detailed areas.


This shows the Mid-Sight in the middle of sanding and being cleaned up.  Focused mainly on the test fitting to the Barrel Jacklet.




To attach the rear part of the Jacket Barrel into the Mid-Sight I made a small fitting using the female threaded part of a 1.25 inch x 1 inch reducer bushing (slip x female threaded).  I sanded it down until it was a snug fit inside the 1.25 inch schedule 26 PVC pipe.




The custom part was attached with PVC cement and inserted about 1/2 of the fitting.  After a few minutes it was glued into the Mid-Sight.  After a bit more sanding and a coating of some primer paint, looking pretty good.




I'm pleased with how the gun barrel jacket is turning out.  Going to be time to add some more details to it.


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To add some more detail to the barrel jacket I wanted to start with the bands on the front where the bi-pod mount is attached around the recoil booster.   I decided to use white rigid PVC Foam board/sheet (0.080 x 7.6 x 11 inches).  It is pretty stiff when holding a full sheet and is too thick to use a score & snap method.  I use my small chop saw to make the strips.  When cut down to narrow strips the PVC board bends pretty easily.


Instead of trying to grove a sheet to get the seams, I simply used multiple strips.  These are attached with Gorlla Crazy Glue gel, so it only takes a few moments for these to stay in place



I then added a second layer of PVC foam board of a different width to resemble the look of the bi-pod being attached.



Next I added the metal tab that goes under the barrel when the bi-pod will mount.   The white PVC foam board from the previous picture above has already gotten its first coat of black paint.  This tab also made from the PVC foam board where the right side of the tab has been rounded off.  I used two oval headed slotted screw heads for decoration.  The screw are not cut off perfectly at the head.  I left a little bit of the shaft and then drilled the PVC board to allow for the shaft.  This made a very tight gluing surface.  These are held in place by Gorilla Super Glue



The PVC foam board and screw heads have been painted black and scuffed up and some light silver dry brushing added to the parts for the metallic look.


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If you have any more 3d parts that you want to have a smooth surface on, I've always just sanded on fairly flat surfaces, and where the surface is curved or angled and has more striations I've put on a little Humbrol modelling putty smeared with my thumb so it almost fills the gaps and then sand.


Acetone is supposed help with getting a smooth surface, but if too much is used it can make a mess as it dissolves the ABS/PLA. I haven't tried it myself, but a colleague at work has with his own prints and most of the time it's given a good finish.



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Acetone only works on ABS. It does not work on PLA.

My colleague has had success with Ultimaker PLA, reading up on some UM forum posts it looks as though somene of their PLA is actually a composite with some ABS mixed in which is why it works. I didn't realise it didn't work with all brands.


If ordering from Shapeways they offer a smoothed print which appears to be ABS which has then been through an Acetone vapour step to help the surface, although I've read some forum posts where people have said that their parts arrive slightly sticky.



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