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Bulldog44

M38 Hollow Core Scope Project 2016 - Bulldog44

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Update March 2018-   For anyone still interested in any progress on these scopes,etc. please go to my Facebook Bulldog Props Page. 
Due to the photobucket fiasco, I haven’t found a reliable way to post pics so I am using the Facebook page for now.

 

https://www.facebook.com/BulldogPropsJapan/

 

 

 

 

When first I started my E-11 build I really wanted to make the Doopy resin scope look as real as possible. I thought buying a real scope at the time was expensive and better suited for a Sterling conversion which is not possible to own in Japan. So I studied all the great mods members here on the FISD did to make their resin scopes better than just a solid cast replica. I quickly decided that I wanted my resin scope to have clear lenses and be hollow to allow light to pass through, meaning I had to drill out the center. With only a simple hand drill and some wood drill bits I did my best to bore a hole through the scope without putting one through my hand. Luckily no trip to the hospital was needed. The next step was to try and find a proper sized lens to fit on both ends. Installing them is not always a easy and clean procedure either. It was a challenge to mod the scope but I think it was one of favorite parts to work on.<br>
That experience led me to wanting a real scope so I managed to buy one ......... then I bought a few more. Having some real scopes in hand, I thought it would be fun to try and cast a scope that wasn't solid but hollow. I wanted to make this part of the E-11 build easier to work with without having to do major surgery and allow for easier ways to add lenses and screws, etc. Casting the whole scope from one end to the other limited access to install the lenses so I thought it would be better to cast all the parts separately. There are very thin walled parts and delicate details to capture making it a bit difficult to do but after some trial mold making and casting I was able to get decent enough results to post. I have had a lots of great advice & feedback from some super FISD members so any success in this project is thanks to them- you know who you all are! Thanks guys! ;)

In the photos you will notice the scope parts are all mixed up shades of grays. Partly because I was experimenting with adding black pigment into the resin and also so its easy to see that all the parts are separate pieces. The resin I am using is from a Japanese model making company and is ideal for casting small parts. It actually has some flexibility to so its not as brittle as other resins I have seen. Again, this project is still in development and more materials and procedures need to be tested. The scope's main body is slush casted so getting even walled castings each time is a skill I haven't mastered yet. A rotational casting machine would be great but money, space, and skills to build one are not in cards at the moment. I am literally making these scopes on the floor in a space no bigger than a square meter or so. :blink:

Bulldog%20Props%20M38%20Scope%20Project%
Parts seen in photos are from my third mold making trial. Little bit of seam cleanup on the main scope body and random flashing on some smaller parts.

Just to clarify the scopes are not 100% hollow after casting. The center of the scope needs to be punched out or drilled depending on the thickness, not difficult at all. The end where the smaller lens unit is attached needs to be drilled or opened. The walls of the scope in general are sufficient and sturdy enough, nothing cracked when I applied some minor pressure. I can't say how resistant they are to added pressure or being struck. I think they are somewhat fragile but certainly stronger than my drilled out Doopy scope. 

There is threading on the casted retainer rings and inside the scope so the parts can actually be screwed on much like the real scopes. Its not always a perfect fit but this should make it easy to install lenses and then screw on the retainer rings to keep it in place. Painting the parts might make the parts fit a bit tighter but that is far from being tested at this point. The smaller lens unit still has all the holes where hardware should go, an easy 1,2,3 to drill them out and install real screws. The scope feet still have visible mounting screw holes as well. 

In the photos (bottom page-second from the left) you can see the ring part that houses the lenses on both ends. I have to cast these parts with the lenses to avoid damaging the real parts. It is a partial casting as well since it might be difficult to fit the whole part if casted as it actually is. You really only need the front ring section, the opaque lenses need to be removed and clear optics can be mounted behind the ring. This may make it easier to install slightly different sized lenses, nothing needs to be exact to ring hole opening (just slightly bigger than the opening of course!)- the outer rim of the lens will be hidden by the ring. <br><br>
One problem I found out was that not all the M38 scopes are perfect copies of one another. I have casted the large and small retainer rings from another M38 scope but they fit rather loose. And strange enough the lens rings are a bit oversized. Perhaps there is some distortion when casted. After a few more tests I should be able to determine if all the casted parts for one particular scope will fit together without any issues. The last part to cast is still in the works but I will leave that for another post in the future if it works out as I hope.<br><br><img src="http://i300.photobucket.com/albums/nn37/Bulldog44USA/Bulldog%20Props%20Hall-ow%20M38%20Scope%20Test%20Phase/Bulldog%20Props%201942%20M38%20Hollow%20Core%20Scope/IMG_0245_zpsmxq23bpy.jpg"alt="IMG_0245_zpsmxq23bpy.jpg"><br><br>
Sorry for the long story about these scopes but hope you get a better idea of whats involved in this project. Its been a year of reading up, months of planning (mostly me staring at an M38 in the midnight hours losing sleep) and a month of silicone & resin tests. Thanks for reading and stopping by! :)

Edited by Bulldog44
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You'll get all the sleep you need when you're dead.

 

Looks sharp Brian!

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Awesome that you're doing this mate. Good luck, the parts look great!

 

Sent from my HUAWEI G510-0251 using Tapatalk

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Hi Brian,

 

glad to see you finally coming online with these beauties. I keep fingers crossed for you and hope we will soon see more.

 

These hollowed scopes could mark the next level of accuracy for the builds out there.

 

To me this seems like the dawn of a new era for resin scope replicas...

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That's an awesome project! I'm really impressed! The scopes looking great!!<br>

Cheers<br>

Christian

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Hi Brian,

 

glad to see you finally coming online with these beauties. I keep fingers crossed for you and hope we will soon see more.

 

These hollowed scopes could mark the next level of accuracy for the builds out there.

 

To me this seems like the dawn of a new era for resin scope replicas...

:D Thanks a million Tino. Still more work to be done but I do hope these turn out to be a one of kind scope. Of course they still need those finishing details that are included in your kits!  

Cheers!

Edited by Bulldog44

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This would make a very nice addition to my aluminum build. You have my attention sir. Great work and thanks for sharing.

Cool. I would like to perhaps offer  a limited run when I think they are up to par for the community.  :duim:

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That's an awesome project! I'm really impressed! The scopes looking great!!<br>

Cheers<br>

Christian

Awesome to hear that Christian. ;) Feedback fuels the fire to try and make these the best resin scopes possible.

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Very cool, the list of stuff to add to my ultimate build is just getting better and longer!!

 

Great work Brian.

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This is some fantastic work. I'm continually amazed at the level of skill and dedication that the people here have.

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Very cool, the list of stuff to add to my ultimate build is just getting better and longer!!

 

Great work Brian.

 

 

the scopes looks real awsome. You doing a great job... :duim:  :duim:

 

 

This is some fantastic work. I'm continually amazed at the level of skill and dedication that the people here have.

 

Thanks guys for your kind words. Keeps me motivated to make these better each time.

 

I had a productive weekend casting a few more of the scopes using black pigment. They are starting to look the part. Getting the black color consistent for all the pieces is difficult but these can be painted so I guess just having a dark base color should be sufficient. Photos to come.

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To push this project further I am working on making the scope easier to assemble by adding the prism cell (cylindrical part where the prisms sit). This means I need to make a new mold of the scope that incorporates prism cell opening. I will attempt to cast the prism cell this week in its original shape but since its such a complex part, I might have to re-think this. Fingers crossed! :icon_beg:

 

Further inside the scope behind the prism cell are screw holes. If I can capture the internal cavity of the scope from the smaller lens end, all the parts will line up exactly as the original by just using the visible screw holes as a guide. 

Sorry no photos of the real scope internal cavity but here is a quick sheet showing how the prism cell can be taken apart. The prism cell is identical on both sides except for the imprinted numbers.

 

M38%20Scope%20Parts%202016%20Prism%20Cel

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Project Update:

 

M38%20Scope%20Parts%202016%20Prism%20Cel

 

The prism cell part was my second biggest worry to cast (after the main scope body) due to its irregular shape. So far I am able to cast fairly clean ones with some minor imperfections on the surface, just a little clean up here and there. Screw holes need to be opened and then it will be easy to get the part perfectly line up with the scope inner cavity screw holes. I didn't cast the actual prisms in place, this leaves some flexibility for someone to maybe install their own prism set up. 

 

Version 4 Scope-

 

I wasn't happy with the seam line that could be seen along the top and the bottom of the scope so I had another go at preparing a new mold that only leaves a seam line on the scope's belly. Another new feature on this version was hinted at in the photos above showing the prism cell installed. I was able to mold the inside of the scope on both ends. Only a circular wall of resin in the center needs to be removed to make the scope hollow 100%. 

 

M38%20Scope%20Parts%202016%20V4%20Test%2

 

I am still experimenting with adding black pigment to the resin so the scope exterior results in mixed finishes of matte to semi-gloss black. 

That is all for now.  Thanks for dropping by! :)

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Very impressive indeed Brian. I was thinking of looking at something similar but the price of a decent real scope was a little out of my budget.

 

Keep up the great work.

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This is a really cool idea. I wonder if those little prisms inside can be purchased anywhere or replicated somehow...

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This is a really cool idea. I wonder if those little prisms inside can be purchased anywhere or replicated somehow...

 

Hey Sean, there is a monocular in that Completion Set V 2.4 that you got. If you fully disassemble this, you will find 2 prisms. These are bigger than the original ones, but maybe someone can get this working...

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Hey Sean, there is a monocular in that Completion Set V 2.4 that you got. If you fully disassemble this, you will find 2 prisms. These are bigger than the original ones, but maybe someone can get this working...

This would be great to see.

 

Brian are you able to measure the sizes of the prisms?

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Hey Sean, there is a monocular in that Completion Set V 2.4 that you got. If you fully disassemble this, you will find 2 prisms. These are bigger than the original ones, but maybe someone can get this working...

 

You're right T-jay, in fact I used those prisms in my scope (copying Chris's [Thrawn's Guard] build), but the prisms in the actual M38 appear to be shaped differently. The problem with modifying/cutting-into a prism is that the surfaces/angles need to be pristine of course in order to get a clear picture.

 

Really don't mean to hijack Brian's thread here, but the idea of having his resin cast scope with real optics inside is very intriguing...

 

I contacted a company called precision optical with pictures of the M38 prisms and he says these are known as "twisted right-angle prisms". Essentially it is exactly like the prism in T-jay's monocular, but "twisted" 90 degrees. I guess this allows it to work in the parallel position seen in the M38 scope, rather than the 90 degree right-angle position seen in T-jay's monocular. I think he/they/someone else might be able to make some of these for us. I will inquire as to the cost. 

 

Will need the dimensions from someone who actually has the prisms, though... if anyone with access to the prisms has time to measure. We really only need the one measurement seen below (the length of one of the short sides) and everything else can be calculated:

 

prism-dimension.jpg

 

Also, are any of the edges mirrored? It looks like the black surfaces seen on the prisms in these shots below might be mirrored-finish, but I can't really tell from the pictures.

Edited by count chocula
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Prism Measurements- I measured as best as I could. I don't have any digital measuring tools so these numbers may be slightly off a touch. 

 

M38%20Scope%20Parts%202016%20Prism%20Mea

 

Sean, Tino & Chris,  thanks for discussing and exploring the possibilities of adding prisms. I think this is very possible. The only part of the scope that may hinder a fully working prism set up is the central glass/lens. I am not sure what role it plays in the magnification or if its only a central glass piece used as a barrier. My resin scopes preserve the location and shape of that lens but of course its opaque resin and needs to be removed. Its possible to install a new lens there with some careful work. 

   I also looked into buying prisms but found them to be very expensive. If the monocular prisms from Tino's completion sets fit well enough, that would be a perfect solution.

Let me know if prisms of the size I posted above can be made/purchased for a relatively cheap price.

 

Upgrades to the scope ultimately would include:

  • working prisms with brackets & screws to mount the prisms to the prism cell unit
  • micro slotted screws (seen on the side of the scope and under the small lens unit)
  • 3 cheesehead slotted screws seen on the outside wall of the smaller lens unit
  • 2 slotted screws set slightly deeper into the small lens unit
  • long thin screws to mount the small lens unit to the prism cell and main scope body
  • lenses for both ends
  • crosshair discs 
  • micro LED lights powered by watch batteries

Hoping to find supplies for these in the next few weeks. 

If there is enough interest from the community I would like to offer scope kits in small runs. Hoping to achieve a higher level of casting quality before I take that step. 

Edited by Bulldog44
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Nice work Brian. Nice avatar too. Getting serious now :)

Thanks mate!  Had to ask my dog for his permission to use his photo. He was easily bribed with a biscuit.

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Scope Parts Labeling- 

 

M38%20Scope%20Parts%202016%20Revised_zps

 

These are some labels I have selected for each scope part in the full assembly. I am no expert so the names either were my best guess and some lifted from telescope diagrams on the web. If you have any other suggestions or feel something is not labeled correctly please feel free to chime in.  :)

Edited by Bulldog44
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I also looked into buying prisms but found them to be very expensive. If the monocular prisms from Tino's completion sets fit well enough, that would be a perfect solution.

Let me know if prisms of the size I posted above can be made/purchased for a relatively cheap price.

 

Yeah, you're right. I couldn't find any prisms like these available commercially, and having them custom-made would be very expensive (I was quoted for $1,400 for two lol)...

 

Another option may be to cast the prisms you have with crystal clear resin, like this stuff. Not sure if you'd need a pressure pot, though, to get all the air bubbles out.

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